Titanium: A Technical Guide

© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

www.asminternational.org

Contents Preface · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · vi Chapter 1 A Primer on Titanium and Its Alloys· · · · · · · · · · · · · · · · · · · · · · · · · 1 Chapter 2 Introduction to Selection of Titanium Alloys · · · · · · · · · · · · · · · · · · · · 5 Chapter 3 Understanding the Metallurgy of Titanium · · · · · · · · · · · · · · · · · · · · · 13 Chapter 4 Ingot Metallurgy and Mill Products· · · · · · · · · · · · · · · · · · · · · · · · · 25 Chapter 5 Forging and Forming · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 33 Chapter 6 Castings · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 39 Chapter 7 Powder Metallurgy · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 47 Chapter 8 Heat Treating · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 55 Chapter 9 Joining Technology and Practice · · · · · · · · · · · · · · · · · · · · · · · · · · 65 Chapter 10 Machining · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 79 Chapter 11 Cleaning and Finishing · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 85 Chapter 12 Structure/Processing/Property Relationships · · · · · · · · · · · · · · · · · · · · 95 Chapter 13 Corrosion Resistance · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 123 Chapter 14 Advanced Alloys and Future Directions · · · · · · · · · · · · · · · · · · · · · · · 131 Appendix A Summary Table of Titanium Alloys · · · · · · · · · · · · · · · · · · · · · · · · 139 Appendix B Titanium Alloy Datasheets · · · · · · · · · · · · · · · · · · · · · · · · · · · · 143 Appendix C Cross Reference to Equivalent Titanium Alloys · · · · · · · · · · · · · · · · · 283 Appendix D Listing of Selected Specification and Standardization Organizations· · · · · · · 289 Appendix E Selected Manufacturers, Suppliers, Services · · · · · · · · · · · · · · · · · · · 295 Appendix F Corrosion Data · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 307 Appendix G Machining Data · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 313 Appendix H Weights and Conversions · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 327 Appendix I Symbols · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 331 Appendix J Glossary · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 333 Appendix K Selected References for Additional Reading · · · · · · · · · · · · · · · · · · · 345 Subject Index · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 351 Alloy Index · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 369

© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

Titanium A Technical Guide Second Edition

Matthew J. Donachie, Jr.

Materials Park, Ohio 44073-0002 www.asminternational.org

www.asminternational.org

© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

www.asminternational.org

Copyright  2000 by ASM International® All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the written permission of the copyright owner.

First printing, December 2000

Great care is taken in the compilation and production of this book, but it should be made clear that NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE GIVEN IN CONNECTION WITH THIS PUBLICATION. Although this information is believed to be accurate by ASM, ASM cannot guarantee that favorable results will be obtained from the use of this publication alone. This publication is intended for use by persons having technical skill, at their sole discretion and risk. Since the conditions of product or material use are outside of ASM’s control, ASM assumes no liability or obligation in connection with any use of this information. No claim of any kind, whether as to products or information in this publication, and whether or not based on negligence, shall be greater in amount than the purchase price of this product or publication in respect of which damages are claimed. THE REMEDY HEREBY PROVIDED SHALL BE THE EXCLUSIVE AND SOLE REMEDY OF BUYER, AND IN NO EVENT SHALL EITHER PARTY BE LIABLE FOR SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHETHER OR NOT CAUSED BY OR RESULTING FROM THE NEGLIGENCE OF SUCH PARTY. As with any material, evaluation of the material under end-use conditions prior to specification is essential. Therefore, specific testing under actual conditions is recommended. Nothing contained in this book shall be construed as a grant of any right of manufacture, sale, use, or reproduction, in connection with any method, process, apparatus, product, composition, or system, whether or not covered by letters patent, copyright, or trademark, and nothing contained in this book shall be construed as a defense against any alleged infringement of letters patent, copyright, or trademark, or as a defense against liability for such infringement. Comments, criticisms, and suggestions are invited, and should be forwarded to ASM International. ASM International staff who worked on this project included Veronica Flint, Manager of Book Acquisitions, Bonnie Sanders, Manager of Production; Carol Terman, Copy Editor; Kathy Dragolich, Production Supervisor; Candace Mullet, Jill Kinson, and Alexandru Popaz-Pauna, Book Production Coordinators; and Scott Henry, Assistant Director of Reference Publications.

Library of Congress Cataloging-in-Publication Data Titamium: a technical guide / Matthew J. Donachie, Jr.—2nd ed. p. cm. Includes bibliographical references and index. 1. Titanium. 2. Titanium alloys. I. Title. TA480.T54 D66 2000 669’.7322—dc21 00-033134 ISBN: 0-87170-686-5 SAN: 204-7586 ASM International® Materials Park, OH 44073-0002 www.asminternational.org Printed in the United States of America

© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

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I wish to dedicate this book to my wife, Martha. She has been with me through many an adventure in this life and has put up with uncounted hours of my toiling on books, lectures and the like.

My life is a homing bird that flies Through the starry dusk and dew Home to the heaven of your true eyes Home, dear heart, to you. from the poem My Life is a Bowl by May Riley Smith When my hair shall shade the snowdrift, And mine eyes shall dimmer grow, I would lean upon some loved one, Through the valley as I go. I would claim of you a promise, Worth to me a world of gold: It is only this, my darling, That you’ll love me when I’m old. from the poem Will You Love Me When I’m Old author unknown

Sing, for faith and hope are high-None so true as you and I-Sing the Lover’s Litany: “Love like ours can never die!” from the poem Lovers Litany by Rudyard Kipling

Matt

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© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

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ASM International Technical Books Committee (1999-2000) Sunniva R. Collins (Chair) Swagelok/Nupro Company Eugen Abramovici Bombardier Aerospace (Canadair) A.S. Brar Seagate Technology Inc. Ngai Mun Chow Det Norske Veritas Pte Ltd. Seetharama C. Deevi Philip Morris, USA Bradley J. Diak Queen’s University James C. Foley Ames Laboratory Dov B. Goldman Precision World Products James F.R. Grochmal Metallurgical Perspectives Nguyen P. Hung Nanyang Technological University

Serope Kalpakjian Illinois Institute of Technology Gordon Lippa North Star Casteel Jacques Masounave Université du Québec Charles A. Parker AlliedSignal Aircraft Landing Systems K. Bhanu Sankara Rao Indira Gandhi Centre for Atomic Research Mel M. Schwartz Sikorsky Aircraft Corporation (retired) Peter F. Timmins University College of the Fraser Valley George F. Vander Voort Buehler Ltd.

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© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

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Contents Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Chapter 7

Chapter 1

Benefits of Powder Metal Processing . . . . . . . . . . . . . . . . . . 47 Alloys Used in Powder Metallurgy Applications . . . . . . . . . 48 Titanium Powder Metallurgy Production Processes . . . . . . . 48 Powder-Making Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Consolidation and Shapemaking . . . . . . . . . . . . . . . . . . . . . . 49 Postcompaction Treatments . . . . . . . . . . . . . . . . . . . . . . . . . 51 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Cost Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

A Primer on Titanium and Its Alloys . . . . . . . 1

ReadMe.First . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Why Use Titanium and Its Alloys? . . . . . . . . . . . . . . . . . . . . . 1 Titanium Metallurgy—A Short Course . . . . . . . . . . . . . . . . . . 2 Getting the Most Out of Titanium Alloys . . . . . . . . . . . . . . . . 3 Some Thoughts about the Future . . . . . . . . . . . . . . . . . . . . . . . 3 A Few Facts about Titanium and Its Production . . . . . . . . . . . 3 Chapter 2 Introduction to Selection of Titanium Alloys . . . 5

Chapter 8

General Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Selection of Titanium Alloys for Service. . . . . . . . . . . . . . . . . 5 The Titanium Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Application and Control of Titanium Alloys . . . . . . . . . . . . . . 9 Titanium Alloy Systems Availability. . . . . . . . . . . . . . . . . . . . 9 Evolution of Casting and Precision Forging . . . . . . . . . . . . . . 9 The Role of Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Property Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Crystal Structure and Alloy Types. . . . . . . . . . . . . . . . . . . . . 13 Effects of Alloying Elements . . . . . . . . . . . . . . . . . . . . . . . . . 14 Transformations and Secondary Phase Formation. . . . . . . . . 16 Titanium Groupings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Microstructural Development in Titanium Alloys. . . . . . . . . 21

Chapter 9

Ingot Metallurgy and Mill Products . . . . . . . 25

Forging and Forming . . . . . . . . . . . . . . . . . . . 33

Forging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Forming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Chapter 6

Joining Technology and Practice. . . . . . . . . . 65

Joining a Reactive Metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Weldability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Brazeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Weld Microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Weld Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 Welding Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Joint Design Criteria and Limitations . . . . . . . . . . . . . . . . . . 70 Precautions in Welding Practice . . . . . . . . . . . . . . . . . . . . . . 70 Fusion Welding Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Arc Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Electron Beam, Laser Beam, and Resistance Spot Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Some Fusion Welding Process Comparisons. . . . . . . . . . . . . 75 Solid-State Welding Practice . . . . . . . . . . . . . . . . . . . . . . . . . 76 Brazing Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

General Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Titanium Ingot Production . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Primary Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Chapter 5

Heat Treating . . . . . . . . . . . . . . . . . . . . . . . . . 55

Why Heat Treat? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Response to Heat Treatment . . . . . . . . . . . . . . . . . . . . . . . . . 55 Special Considerations in Heat Treatment . . . . . . . . . . . . . . . 56 Stress Relieving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Process Annealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Solution Annealing (Treatment) and Aging. . . . . . . . . . . . . . 58 Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Atmospheres, Contamination, and Post-Heat Treatment Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Growth during Heat Treatment . . . . . . . . . . . . . . . . . . . . . . . 63 Hot Isostatic Pressing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Chapter 3 Understanding the Metallurgy of Titanium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Chapter 4

Powder Metallurgy . . . . . . . . . . . . . . . . . . . . . 47

Castings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Alloys Used for Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Advantages of Cast Titanium and Titanium Alloys. . . . . . . . 39 Casting Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Effect of Weld Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Hot Isostatic Pressing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Heat Treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Cast Titanium Applications . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Cost Comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Chapter 10

Machining . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Traditional Machining of Titanium . . . . . . . . . . . . . . . . . . . . 80 Nontraditional Machining Methods . . . . . . . . . . . . . . . . . . . . 83 Surface Integrity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Chapter 11

Cleaning and Finishing. . . . . . . . . . . . . . . . . 85

Special Coatings and Surface Finishes . . . . . . . . . . . . . . . . . 85 Cleaning and Descaling Problems . . . . . . . . . . . . . . . . . . . . . 85

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© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

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Chapter 14

Removal of Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Molten Salt Descaling Baths . . . . . . . . . . . . . . . . . . . . . . . . . 87 Pickling Procedures Following Descaling . . . . . . . . . . . . . . . 88 Removal of Tarnish Films . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Acid Pickling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Polishing and Buffing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Wire Brushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Removal of Grease and Other Soils . . . . . . . . . . . . . . . . . . . . 91 Chemical Conversion Coatings . . . . . . . . . . . . . . . . . . . . . . . 91 Electroplating on Titanium . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Other Coatings and Procedures . . . . . . . . . . . . . . . . . . . . . . . 92

Titanium Aluminides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 Titanium Matrix Composites . . . . . . . . . . . . . . . . . . . . . . . 133 Other Process Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . 134 Nanostructure Technology and Rapid-Solidification Rate Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Higher-Temperature Conventional Titanium Alloys . . . . . . 135 Closing Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

Chapter 12 Relationships among Structures, Processing, and Properties . . . . . . . . . . . . . . . . . . . . . . . 95

Appendix A

Summary Table of Titanium Alloys. . . . . 139

AppendixB

Titanium Alloy Datasheets. . . . . . . . . . . . . 143

Other Sources of Information. . . . . . . . . . . . . . . . . . . . . . . . 143 Appendix C Cross Reference to Equivalent Titanium Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283

Basic Properties of Titanium and Its Alloys . . . . . . . . . . . . . 95 Structure and Hardening of Titanium . . . . . . . . . . . . . . . . . . 96 Interstitial Effects in Titanium . . . . . . . . . . . . . . . . . . . . . . . . 96 Pure Titanium Mechanical Properties . . . . . . . . . . . . . . . . . . 97 Alpha/Near Alpha Alloys. . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Alpha-Beta Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Beta Alloys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Relationships among Alloy Properties and Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Static Properties of Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Cyclic Properties of Alloys . . . . . . . . . . . . . . . . . . . . . . . . . 105 Cast Titanium Alloy Properties . . . . . . . . . . . . . . . . . . . . . . 110 Powder Metallurgy Titanium Alloy Properties . . . . . . . . . . 114 Low-Temperature Service. . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Chapter 13

Advanced Alloys and Future Directions . . 131

Appendix D Listing of Selected Specification and Standardization Organizations . . . . . . . . . . . . . . . . . . . 289 Appendix E Selected Manufacturers, Suppliers, Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 Appendix F

Corrosion Data . . . . . . . . . . . . . . . . . . . . . . 307

Corrosion Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 Appendix G

Machining Data . . . . . . . . . . . . . . . . . . . . . 313

Specific Data Listings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 Thermal Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

Corrosion Resistance . . . . . . . . . . . . . . . . . 123

Corrosion Behavior and Corrosion Resistance . . . . . . . . . . 123 Corrosion Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 Uniform Corrosion Processes . . . . . . . . . . . . . . . . . . . . . . . 125 Alloying Additions and Corrosion . . . . . . . . . . . . . . . . . . . . 126 Localized Corrosion Processes . . . . . . . . . . . . . . . . . . . . . . 127 Hydrogen in Titanium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Stress-Corrosion Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Liquid Metal Embrittlement. . . . . . . . . . . . . . . . . . . . . . . . . 130

Appendix H

Weights and Conversions . . . . . . . . . . . . . 327

Appendix I

Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

Appendix J

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

Appendix K Selected References for Additional Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351 Alloy Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369

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Preface Titanium and its alloys continue to provide excellent service in a variety of industries. As we progress into the twenty-first century, in the sixth decade of titanium’s commercial and industrial use, it appears that the industry has matured, but new technology and applications for the metal continue to develop. Despite the utility of titanium and its alloys, the number of books dealing with the metal has been limited. A series of International Conferences on Titanium, held periodically since 1968, have provided a focus for research reports while other occasional symposia and articles have contributed to the industrial literature on titanium. ASM International has been a leader in providing coverage of titanium and its alloys and has issued several books, including the first edition of Titanium: A Technical Guide. Titanium: A Technical Guide, Second Edition, is meant to provide the most complete introduction possible to the metal and its alloys through the use of 14 chapters and 11 appendices. The aim has been to condense and review the significant features of the metallurgy and application of titanium and its alloys. The text has been revised and expanded from that of the first edition with many additional figures and new and revised tables. The second edition of the Guide not only contains more information than the previous edition, but the book also has been modified to a larger page size to better accommodate the tables provided. All technical aspects of the use of titanium are covered with sufficient metals property data for most users. The Guide has been reviewed for accuracy, but it is possible that errors will have occurred. The editor would appreciate receiving either corrections or suggestions from readers. If you are new to the use of titanium, I would strongly recommend starting with Chapter 1: A Primer on Titanium and Its Alloys. This executive summary of the metal and its uses

should suit the needs of readers who require a brief introduction to titanium and who do not have time to devote to more intense study of the subject. If you are knowledgeable in metallurgy and/or materials engineering, or wish more in-depth information, you may prefer to choose from one of the chapter topics or the appendices that is more relevant to your immediate needs. For additional property data, see the ASM book Materials Property Handbook: Titanium Alloys. The editor wishes to thank not only those who contributed to the first edition of Titanium: A Technical Guide, but also the many contributors to other ASM books and the ASM Handbook series. This book is a product of the editor’s experience and personal bias, as well as his technical files. Most of all, however, it is a product of the resources available in the ASM International system. The editor especially would like to thank Veronica Flint of ASM International for her perseverance with him as the material made its way into electronic form. Veronica and I worked together on the first edition of Titanium: A Technical Guide, and it has been a pleasure to work with her again on this significant update. Its successful publication is a tribute to the dedication of ASM International to providing access to materials information for the widest possible audience.

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M. J. D. [email protected] Winchester, NH October 2000

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Titanium: A Technical Guide Matthew J. Donachie, Jr., p1-3 DOI:10.1361/tatg2000p001

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 1

A Primer on Titanium and Its Alloys ReadMe.First IN THE BUSINESS WORLD OF TODAY, the extended treatment offered by many reference books may pose an obstacle to a manager or other person needing to find information on a specific topic in a reasonable time. This is especially true when only an operational understanding of a subject is required. Titanium: A Technical Guide, Second Edition addresses the need for a concise printed summary of the most useful information required to understand titanium and its alloys. Even in a summary volume, there is a need for an overview of the technical aspects of a metal. This primer supports the needs of engineering, management, and other professionals for information on titanium by providing a brief overview of the major topics that are discussed more thoroughly throughout the book. The information in this chapter will maximize the reader’s ability to use the volume in the most efficient way and, at the same time, help the reader to glean enough information to satisfy his or her immediate requirements.

Fig. 1.1

After reading the primer, the reader might wish to refer to the Contents and the Index to locate more information about specific topics. Helpful information can also be found in the Glossary (Appendix J) and the list of Symbols (Appendix I).

important benefits offered by titanium alloys illustrate the basis for the widespread use of titanium today:

• The density of titanium is only about 60% of that of steel or nickel-base superalloys.

• The tensile strength (as an alloy) of titanium

Why Use Titanium and Its Alloys? Titanium was discovered in 1790 but not purified until the early 1900s. Moreover, the metal did not become widely used until the second half of the twentieth century. However, titanium now has the accumulated experience of some 50 years of modern industrial practice and design application to support its use. Much of this use has come in military applications in aircraft such as the SR71 (Fig. 1.1) or gas turbine engines (Fig. 1.2). More recent uses have featured such items as golf clubs and bicycles. Titanium has found its niche in many industries, owing to its unique density, corrosion resistance, and relative strength advantages over competing materials such as aluminum, steels, and superalloys. Some significant facts and/or

SR71 aircraft: first use of beta alloys in aerospace structures. Courtesy of Lockheed California Co.

Fig. 1.2

•

• •

can be comparable to that of lower-strength martensitic stainless and is better than that of austenitic or ferritic stainless. Alloys can have ultimate strengths comparable to ironbase superalloys, such as A286, or cobaltbase alloys, such as L605. The commercial alloys of titanium are useful at temperatures to about 538 °C to 595 °C (1000 °F to 1100 °F), dependent on composition. Some alloy systems (titanium aluminides) may have useful strengths above this temperature. The cost of titanium, while approximately four times that of stainless steel, is comparable to that of superalloys. Titanium is exceptionally corrosion resistant. It often exceeds the resistance of stainless steel in most environments, and it has outstanding corrosion resistance in the human body.

F119 engine by Pratt & Whitney powering the F22 Raptor aircraft

2 / Titanium: A Technical Guide

• Titanium may be forged or wrought by stan•

•

• • •

dard techniques. Titanium is castable, with investment casting the preferred method. (Investment cast titanium alloy structures have a lower cost than conventional forged/wrought fabricated titanium alloy structures.) Titanium may be processed by means of P/M technology. (Powder may cost more, yet P/M may offer property and processing improvements as well as an overall cost-savings potential.) Titanium may be joined by means of fusion welding, brazing, adhesives, diffusion bonding, and fasteners. Titanium is formable and readily machinable, assuming reasonable care is taken. Titanium is available in a wide variety of types and forms.

Titanium Metallurgy— A Short Course Structures in General

are not meant to be all inclusive but rather to suggest some of the alloys used in titanium alloy design.

more additional alloy element provided as well).

More on Structure

Titanium and Titanium Alloy Characteristics

Commercially pure (CP) titanium is alpha in structure. Additions of alloying elements to pure titanium produce the range of possible microstructures in titanium alloys. With sufficient beta-favoring alloy element level, beta phase is produced on heating and transformed during the cooling following high processing. The resulting structures are representative of the alpha-beta alloys. A variation of alpha alloys recognizes the wide range of alloy chemistry and structure possible within the essentially alpha range. This variation is termed near-alpha. Beta structures generally should be referred to as metastable beta. These are alloys that retain an essentially beta structure on cooling to room temperature. Titanium aluminides are intermetallic compounds of titanium and aluminum (with one or

Commercially pure titanium and the alpha and near-alpha titanium alloys generally demonstrate the best general corrosion-resistance qualities. They are the most weldable of the titanium/titanium alloy family. Pure titanium usually has some amount of oxygen alloyed with it. The strength of CP titanium is affected by the interstitial (oxygen and nitrogen) element content. Alpha alloys usually have high amounts of aluminum that contribute to oxidation resistance at high temperatures. (Alpha-beta alloys also contain, as the principal element, high amounts of aluminum, but the primary reason is to stabilize the alpha phase.) Alpha alloys cannot be heat treated to develop higher mechanical properties because they are single-phase alloys. The addition of certain alloying elements to pure titanium en-

The melting point of titanium is in excess of 1660 °C (3000 °F), although most commercial alloys operate at or below 538 °C (1000 °F). Titanium has two elemental crystal structures: in one, the atoms are arranged in a body-centered cubic (bcc) array; in the other, the atoms are arranged in a close-packed hexagonal array (Fig. 1.3). The cubic structure is found only at high temperatures, unless the titanium is alloyed with other elements to maintain the cubic structure at lower temperatures. The two crystal structures of titanium are commonly known as alpha and beta. Alpha actually refers to any hexagonal titanium, pure or alloyed, while beta denotes any cubic titanium, pure or alloyed. The alpha and beta “structures”—sometimes called systems or types— are the basis for the generally accepted four classes of titanium alloys: alpha, near-alpha, alpha-beta, and beta. Figure 1.4 schematically shows some effects of alloying elements on structure for representative alloys and classes or subclasses of titanium alloys. The figure also indicates the effects that structures have on some selected properties. The alloy compositions indicated

(a)

(b)

Appearance of crystal structures of titanium at the atomic level. (a) Hexagonal, close packed. (b) Cubic, body centered

Fig. 1.3

Fig. 1.4

Schematic showing effects of alloy elements on structure and some selected properties (representative alloys noted)

A Primer on Titanium and Its Alloys / 3 ables the resultant alloys to be heat treated or processed in the temperature range where the alloy is two phase (alpha and beta). The two-phase condition permits the structure to be refined and, by permitting some beta to be retained temporarily at lower temperature, enables optimum control of the microstructure during subsequent transformation when the alloys are “aged” after cooling from the forging or solution heat treatment temperature. The alpha-beta alloys, when properly treated, have an excellent combination of strength and ductility. They are stronger than the alpha or the beta alloys. The beta alloys are metastable; that is, they tend to transform to an equilibrium, or balance of structures. The beta alloys generate strength from the intrinsic strength of the beta structure and the precipitation of alpha and other phases from the alloy through heat treatment after processing. The most significant benefit provided by a beta structure is the increased formability of such alloys relative to the hexagonal crystal structure types (alpha and alpha-beta). Titanium aluminides differ from conventional titanium alloys in that they are principally chemical compounds alloyed to enhance strength, formability, and so on. The aluminides have higher operational temperatures than conventional titanium, but at higher cost, and generally have lower ductility and formability.

Getting the Most Out of Titanium Alloys The greatest potential that titanium and titanium alloys can provide in a specific application is realized if a few simple rules of thumb are kept in mind initially before a design is actually begun. Some of the more important guidelines are as follows:

• Wrought titanium alloy products are the more

•

readily available, but castings are close behind. Wrought alloys also have the greatest experience factor. Castings, however, are useful for savings in weight and cost. Cast-plus-HIP (hot isostatic pressed) material can attain comparable operating strength levels to wrought products for most alloys. Powder alloys are becoming more accepted. Also, powder processing allows more exotic titanium alloys to be mixed. However, because of the interaction of titanium with interstitial gases such as oxygen and nitrogen, complex powder production techniques are necessary. Consequently, titanium alloy powder may be too expensive for many applications. Furthermore, property levels for powder-processed conventional alloy compositions may not reach expectations. Nevertheless, with powder, there is the built-in, and possibly cost-offsetting, near-net shape (NNS) capability that powder offers. This

•

•

•

•

•

implies at least a potential for overall lower costs when amortized over the entire project. Cast or powder titanium alloys always should be possible candidate materials for structural applications. However, planning for such use should begin during the initial design stage rather than waiting and trying to fit the cast or powder-processed material into a wrought alloy design late in the developmental stages. It is wise when making a titanium alloy selection to use the more common alloys unless uncommon properties are absolutely needed. (Ti-6A1-4V clearly has widespread advantages, or else it would not be so commonly used.) Handbooks, reference material, and so on all are valuable in design. Numerous handbooks are available (Appendix K provides a selected references list), but there is no substitute for personal contact with a supplier or fabricator. (A partial list of titanium trade organizations, suppliers, and primary metal fabricators appears in Appendix E.) Properties that assume unusual forming conditions and/or unrealistic casting or powder processing yields should not be depended on, nor should unusual cooling or heating practices for properties. Cast and powder alloy properties may fall short of the best of wrought alloy properties. Typical properties may be roughly comparable, but data scatter in cast (and possibly in powder) products could result in lower design minimums. If a design admits of no flexibility with respect to property level realization, the design may be irreversibly compromised later. Aerospace specifications provide for the best properties and performance. When using titanium in noncritical applications, less stringent specifications should be chosen, where possible, to save money and time.

Some Thoughts about the Future The dynamic nature of industry as well as developments of a political nature can and will continue to affect the future of the titanium industry. For up-to-date information on business aspects of titanium, trade groups such as those listed in Appendix E can be contacted. However, some projections about the technical aspects of titanium use can be made:

• Titanium alloy compositions available and

used in the near future will remain substantially the same as those available at the end of the twentieth century, although the relative mix of alloys may change. Aerospace product volume is declining; fewer funds are available for research. A result is that new titanium alloy composition development will diminish. Furthermore, nonaerospace applications are consuming more titanium than in the early years of titanium development. Most of these applications use existing al-

• • • •

• •

loys that are available with limited added development costs. Greater emphasis will continue to be placed on the use of cast alloys. Textured alloys may be accepted for selected applications. (While these are technically feasible, there still is no real driving factor behind the concept.) Superplastic forming in conjunction with bonding should increase in favor, although it may remain largely a process for the aerospace industry. Advanced P/M processed materials will continue to be worked, but extensive cost-effective applications are unlikely in the near future. Much development work will be needed before P/M techniques can effectively be applied to an application. A good property base does not yet exist. Rapid solidification rate (RSR) processing is comparable to P/M in application and is not likely to be useful for most commercial service. Aluminides will continue to be developed and tested for applications requiring highertemperature capability, but economic application for industrial and commercial use is going to be limited for many years.

A Few Facts about Titanium and Its Production Titanium is the ninth most-abundant element on the planet and the fourth most-abundant structural metal. Mineral sources of titanium are rutile, ilmenite, and leucoxene, an alteration product of ilmenite. Principal world producers of ilmenite and titanium slag made from ilmenite are Australia, Canada, Norway, the Republic of South Africa, the United States, and Russia. Main producers of rutile are Australia, Sierra Leone, and the Republic of South Africa. Titanium sponge is produced mainly by Russia, Kazakhstan, the United States, Japan, the United Kingdom, and China. Titanium sponge and ingot are available worldwide. The titanium business was in a state of flux during the 1990s. Consolidations and closures modified not only the business names but also the delivery of titanium services in the world. Since titanium operations start with the availability of sponge and then ingot for remelt, casting, or for subsequent working, it is desirable that some players in the titanium market be identified. The primary producers of titanium sponge and ingot in the United States at the end of the twentieth century were Timet, RMI, and Allegheny-Teledyne-Oremet. In view of the fluidity of business operations, no other listing of titanium-related organizations is practical. When information is required, the appropriate trade organizations should be contacted as a start in locating titanium producers, fabricators, and other information for any titanium or titanium alloy application (Appendix E provides a listing of such organizations).

Titanium: A Technical Guide Matthew J. Donachie, Jr., p5-11 DOI:10.1361/tatg2000p005

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 2

Introduction to Selection of Titanium Alloys General Background TITANIUM is a low-density element (approximately 60% of the density of steel and superalloys) that can be strengthened greatly by alloying and deformation processing. (Characteristic properties of elemental titanium are given in Table 2.1.) Titanium is nonmagnetic and has good heat-transfer properties. Its coefficient of thermal expansion is somewhat lower than that of steel and less than half that of aluminum. Titanium and its alloys have melting points higher than those of steels, but maximum useful temperatures for structural applications generally range from as low as 427 °C (800 °F) to the region of approximately 538 °C to 595 °C (1000 °F to 1100 °F), dependent on

Table 2.1

composition. Titanium aluminide alloys show promise for applications at temperatures up to 760 °C (1400 °F). Titanium and titanium alloys are produced in a wide variety of product forms, with some examples shown in Fig. 2.1. Titanium can be wrought, cast, or made by P/M techniques. It may be joined by means of fusion welding, brazing, adhesives, diffusion bonding, or fasteners. Titanium and its alloys are formable and readily machinable, assuming reasonable care is taken. Some specific examples of product forms are: Mill products

• Ingot • Billet

Physical and mechanical properties of elemental titanium

Property

Description or value

Atomic number Atomic weight Atomic volume Covalent radius Ionization potential Thermal neutron absorption cross section Crystal structure Alpha (≤882.5 °C, or 1620 °F) Beta ( ≥882.5 °C, or 1620 °F) Color Density Melting point Solidus/liquidus Boiling point Specific heat (at 25 °C) Thermal conductivity Heat of fusion Heat of vaporization Specific gravity Hardness Tensile strength Young’s modulus Poisson’s ratio Coefficient of friction At 40 m/min (125 ft/min) At 300 m/min (1000 ft/min) Coefficient of linear thermal expansion Electrical conductivity Electrical resistivity (at 20 °C) Electronegativity Temperature coefficient of electrical resistance Magnetic susceptibility (volume, at room temperature)

22 47.90 10.6 W/D 1.32 Å 6.8282 V 5.6 barns/atom Close-packed hexagonal Body-centered cubic Dark gray 4.51 g/cm3 (0.163 lb/in.3) 1668 ± 10 °C (3035 °F) 1725 °C (3135 °F) 3260 °C (5900 °F) 0.5223 kJ/kg ⋅ K 11.4 W/m ⋅ K 440 kJ/kg (estimated) 9.83 MJ/kg 4.5 70 to 74 HRB 240 MPa (35 ksi) min 120 GPa (17 × 106 psi) 0.361 0.8 0.68 8.41 μm/m ⋅ K 3% IACS (where copper = 100% IACS) 420 nΩ ⋅ m 1.5 Pauling’s 0.0026/°C 180 ( ±1.7) × 10–6 mks

• • • • •

Bar Sheet Strip Tube Plate

Nonmill products

• Sponge • Powder Customized product forms

• Forgings • P/M items • Castings One of many different types of investment cast titanium parts now produced is shown in Fig. 2.2. Figure 2.3 shows a large forged titanium part. This part weighs approximately 1400 kg (3000 lb). Titanium has the ability to passivate and thereby exhibit a high degree of immunity against attack by most mineral acids and chlorides. Pure titanium is nontoxic; commercially pure titanium and some titanium alloys generally are biologically compatible with human tissues and bones. The excellent corrosion resistance and biocompatibility coupled with good strengths make titanium and its alloys useful in chemical and petrochemical applications, marine environments, and biomaterials applications. The combination of high strength, stiffness, good toughness, low density, and good corrosion resistance provided by various titanium alloys at very low to elevated temperatures allows weight savings in aerospace structures and other high-performance applications.

Selection of Titanium Alloys for Service Primary Aspects. Titanium and its alloys are used primarily in two areas of application where the unique characteristics of these metals

6 / Titanium: A Technical Guide

(a)

(e)

Fig. 2.1

Fig. 2.2

(b)

(d)

(c)

(f)

(g)

Some titanium and titanium alloys product forms. (a) Strip. (b) Slab. (c) Billet. (d) Wire. (e) Sponge. (f) Tube. (g) Plate. Courtesy of Teledyne Wah Chang Albany

Investment cast titanium transmission case for Osprey vertical take-off and landing aircraft

Fig. 2.3

Forged titanium landing gear beam for Boeing 757 aircraft

Introduction to Selection of Titanium Alloys / 7 justify their selection: corrosion-resistant service and strength-efficient structures. For these two diverse areas, selection criteria differ markedly. Corrosion applications normally use lower-strength “unalloyed” titanium mill products fabricated into tanks, heat exchangers, or reactor vessels for chemical-processing, desalination, or power-generation plants. In contrast, high-performance applications such as gas turbines, aircraft structures, drilling equipment, and submersibles, or even applications such as biomedical implants, bicycle frames, and so on, typically use higher-strength titanium alloys. However, this use is in a very selective manner that depends on factors such as thermal environment, loading parameters, corrosion environment, available product forms, fabrication characteristics, and inspection and/or reliability requirements (Fig. 2.4). Alloys for high-performance applications in strength-efficient structures normally are processed to more stringent and costly requirements than “unalloyed” titanium for corrosion service. As examples of use, alloys such as Ti-6Al-4V and Ti-3Al-8V-6Cr-4Mo-4Zr are being used for offshore drilling applications and geothermal piping, while alloys such as Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo+Si, Ti-10V-2Fe-3Al, and

(a)

(c)

Fig. 2.4

Ti-6V-2Sn-2Zr-2Cr-2Mo+Si are used or planned for use in aircraft or in gas turbine engines for aerospace applications. Desired mechanical properties such as yield or ultimate strength to density (strength efficiency), fatigue crack growth rate, and fracture toughness, as well as manufacturing considerations such as welding and forming requirements, are extremely important. These factors normally provide the criteria that determine the alloy composition, structure (alpha, alpha-beta, or beta), heat treatment (some variant of either annealing or solution treating and aging), and level of process control selected or prescribed for structural titanium alloy applications. A summary of some commercial and semicommercial titanium grades and alloys is given in Table 2.2. For lightly loaded structures, where titanium normally is selected because it offers greater resistance to the effects of temperature than aluminum offers, commercial availability of required mill products, along with ease of fabrication, may dictate selection. Here, one of the grades of unalloyed titanium usually is chosen. In some cases, corrosion resistance, not strength or temperature resistance, may be the major factor in selection of a titanium alloy.

Selection for Corrosion Resistance. Economic considerations normally determine whether titanium alloys will be used for corrosion service. Capital expenditures for titanium equipment generally are higher than for equipment fabricated from competing materials such as stainless steel, brass, bronze, copper nickel, or carbon steel. As a result, titanium equipment must yield lower operating costs, longer life, or reduced maintenance to justify selection, which most frequently is made on a lower totallife-cycle cost basis. Commercially pure (CP) titanium satisfies the basic requirements for corrosion service. Unalloyed titanium normally is produced to requirements such as those of ASTM standard specifications B 265, B 338, or B 367 in grades 1, 2, 3, and 4 in the United States. These grades vary in oxygen and iron content, which control strength level and corrosion behavior, respectively. For certain corrosion applications, Ti-0.2Pd (ASTM grades 7, 8, and 11) may be preferred over unalloyed grades 1, 2, 3, and 4. Selection for Strength and Corrosion Resistance. Due to its unique corrosion behavior, titanium is used extensively in prosthetic devices such as heart-valve parts and load-bearing

(b)

(d) A few typical areas of application for high-performance titanium parts. (a) Offshore drilling rig components. (b) Subsea equipment and submersibles requiring ultrastrength. (c) Aircraft. (d) Components for marine and chemical processing operations.

8 / Titanium: A Technical Guide hip and other bone replacements. In general, body fluids are chloride brines that have pH values from 7.4 into the acidic range and also contain a variety of organic acids and other components—media to which titanium is totally immune. Ti-6Al-4V normally is employed for applications requiring higher strength, but other titanium alloys are used as well. Moderately high strength is important in the application of titanium to prosthetics, but strength efficiency (strength to density) is not the prime criterion, assuming that biocompatibility concerns are addressed. However, while strength efficiency is not the defining factor, it has been suggested that the lesser weight of titanium alloy implants plays a noticeable role in patient perception of the efficacy of the device implanted in the body. Selection for Strength Efficiency. Historically, wrought titanium alloys have been used widely instead of iron or nickel alloys in aerospace applications because titanium saves weight in highly loaded components that operate at low-to-moderately elevated temperatures. Many titanium alloys have been custom designed to have optimum tensile, compressive, and/or creep strength at selected temperatures, Table 2.2

and at the same time to have sufficient workability to be fabricated into mill products suitable for a specific application. Selection for Other Property Reasons. Optic-system support structures are a little-known but very important structural application for titanium. Complex castings are used in surveillance and guidance systems for aircraft and missiles to support the optics where wide temperature variations are encountered in service. The chief reason for selecting titanium for this application is that the thermal-expansion coefficient of titanium most closely matches that of the optics. Although prosthetic applications for titanium alloys are made for biocompatibility and strength reasons, there is a benefit for structural implants such as hip stems because the lower modulus (than cobalt alloys and stainless) allows more load transfer to the bone and the potential for longer-lasting implant performance.

total weight of all titanium alloys shipped. During the life of the titanium industry, various compositions have had transient usage; Ti-4A1-3Mo-1V, Ti-7A1-4Mo, and Ti-8Mn are a few examples. Many alloys have been invented but have never seen significant commercial use. Ti-6Al-4V alloy is unique in that it combines attractive properties with inherent workability (which allows it to be produced in all types of mill products, in both large and small sizes), good shop fabricability (which allows the mill products to be made into complex hardware), and the production experience and commercial availability that lead to reliable and economic usage. Consequently, wrought Ti-6Al-4V became the standard alloy against which other alloys must be compared when selecting a titanium alloy (or custom designing one) for a specific application. Ti-6Al-4V also is the standard alloy selected for castings that must exhibit superior strength. It even has been evaluated in P/M processing. Ti-6Al-4V will continue to be the most-used titanium alloy for many years in the future. Ti-6Al-4V has temperature limitations that restrict its use to approximately 400 °C (750 °F). For elevated-temperature applications, the

The Titanium Alloys For most of the last half of the twentieth century, Ti-6Al-4V accounted for about 45% of the

Some commercial and semicommercial grades and alloys of titanium Tensile strength (min)

0.2% yield strength (min)

Impurity limits, wt% (max)

Nominal composition, wt%

Designation

MPa

ksi

MPa

ksi

N

C

H

Fe

O

Al

Sn

Zr

Mo

Others

Unalloyed grades ASTM grade 1 ASTM grade 2 ASTM grade 3 ASTM grade 4 ASTM grade 7 ASTM grade 11

240 340 450 550 340 240

35 50 65 80 50 35

170 280 380 480 280 170

25 40 55 70 40 25

0.03 0.03 0.05 0.05 0.03 0.03

0.08 0.08 0.08 0.08 0.08 0.08

0.015 0.015 0.015 0.015 0.015 0.015

0.20 0.30 0.30 0.50 0.30 0.20

0.18 0.25 0.35 0.40 0.25 0.18

… … … … … …

… … … … … …

… … … … … …

… … … … … …

… … … … 0.2Pd 0.2Pd

α and near-α alloys Ti-0.3Mo-0.8Ni Ti-5Al-2.5Sn Ti-5Al-2.5Sn-ELI Ti-8Al-1Mo-1V Ti-6Al-2Sn-4Zr-2Mo Ti-6Al-2Nb-1Ta-0.8Mo Ti-2.25Al-11Sn-5Zr-1Mo Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.35Si

480 790 690 900 900 790 1000 1030

70 115 100 130 130 115 145 149

380 760 620 830 830 690 900 910

55 110 90 120 120 100 130 132

0.03 0.05 0.07 0.05 0.05 0.02 0.04 0.03

0.10 0.08 0.08 0.08 0.05 0.03 0.04 0.08

0.015 0.02 0.0125 0.015 0.0125 0.0125 0.008 0.006

0.30 0.50 0.25 0.30 0.25 0.12 0.12 0.05

0.25 0.20 0.12 0.12 0.15 0.10 0.17 0.15

… … 5 2.5 5 2.5 8 … 6 2 6 … 2.25 11 5.8 4

… … … … 4 … 5 3.5

0.3 0.8Ni … … … … 1 1V 2 0.08Si 1 2Nb, 1Ta 1 0.2Si 0.5 0.7Nb, 0.35Si

α-β alloys Ti-6Al-4V(a) Ti-6Al-4V-ELI(a) Ti-6Al-6V-2Sn(a) Ti-8Mn(a) Ti-7Al-4Mo(a) Ti-6Al-2Sn-4Zr-6Mo(b) Ti-5Al-2Sn-2Zr-4Mo-4Cr(b)(c) Ti-6Al-2Sn-2Zr-2Mo-2Cr(c) Ti-3Al-2.5V(d) Ti-4Al-4Mo-2Sn-0.5Si

900 830 1030 860 1030 1170 1125 1030 620 1100

130 120 150 125 150 170 163 150 90 160

830 760 970 760 970 1100 1055 970 520 960

120 110 140 110 140 160 153 140 75 139

0.05 0.05 0.04 0.05 0.05 0.04 0.04 0.03 0.015 (e)

0.10 0.08 0.05 0.08 0.10 0.04 0.05 0.05 0.05 0.02

0.0125 0.0125 0.015 0.015 0.013 0.0125 0.0125 0.0125 0.015 0.0125

0.30 0.25 1.0 0.50 0.30 0.15 0.30 0.25 0.30 0.20

0.20 0.13 0.20 0.20 0.20 0.15 0.13 0.14 0.12 (e)

6 6 6 … 7.0 6 5 5.7 3 4

… … 2 … … 2 2 2 … 2

… … … … … 4 2 2 … …

… … … … 4.0 6 4 2 … 4

1170 1170 1170 900 690 1000(b) 1241(f) 862

170 170 170 130 100 145(b) 180(f) 125

1100 1100 1100 830 620 965(b) 1172(f) 793

160 160 160 120 90 140(b) 170(f) 115

0.05 0.05 0.03 0.03 0.05 0.05

0.05 0.05 0.05 0.05 0.10 0.05

0.015 0.025 0.015 0.20 0.020 0.015

2.5 0.35 2.5 0.25 0.35 0.25

0.16 0.17 0.17 0.12 0.18 0.13

3 3 3 3 … 3

… … … … 4.5 3

… … … 4 6.0 …

… 10V … 11.0Cr, 13.0V 8.0 8.0V 4 6Cr, 8V 11.5 … … 15V, 3Cr

0.05

0.05

0.015

0.25

0.13

3

…

…

15

β alloys Ti-10V-2Fe-3Al(a)(c) Ti-13V-11Cr-3Al(b) Ti-8Mo-8V-2Fe-3Al(b)(c) Ti-3Al-8V-6Cr-4Mo-4Zr(a)(c) Ti-11.5Mo-6Zr-4.5Sn(a) Ti-15V-3Cr-3Al-3Sn Ti-15Mo-3Al-2.7Nb-0.2Si

4V 4V 0.75Cu, 6V 8.0Mn … … 4Cr 2Cr, 0.25Si 2.5V 0.5Si

2.7Nb, 0.2Si

(a) Mechanical properties given for the annealed condition; may be solution treated and aged to increase strength. (b) Mechanical properties given for the solution-treated-and-aged condition; alloy not normally applied in annealed condition. (c) Semicommercial alloy; mechanical properties and composition limits subject to negotiation with suppliers. (d) Primarily a tubing alloy; may be cold drawn to increase strength. (e) Combined O2 + 2N2 = 0.27%. (f) Also solution treated and aged using an alternative aging temperature (480 °C, or 900 °F)

Introduction to Selection of Titanium Alloys / 9 most commonly used alloy is Ti-6Al-2Sn4Zr-2Mo + Si. This alloy is primarily used for turbine components and in sheet form for afterburner structures and various “hot” airframe applications. Titanium aluminides may displace the latter alloy but not for commercial applications in the foreseeable future. During the approximately 50 years that titanium has been commercially available, many other alloys have been developed, but none match the almost 50% market share that Ti-6Al-4V enjoys. In addition to the use of Ti-6Al-4V, Pratt & Whitney has used Ti8Al-1Mo-1V, Ti-5A1-2.5Sn, Ti-6Al-2Sn-4Zr-2Mo, and Ti-6Al-2Sn-4Zr-6Mo in its gas turbine engines. General Electric has used Ti-4A1-4Mn, Ti-l.5Fe-2.7Cr, and Ti-17 among other alloys in addition to the Ti-6Al-4V alloy. Rolls Royce has used IMI 550, IMI 679, IMI 685, IMI 829, and IMI 834 alloys as well as Ti-6Al-4V (IMI 318) in its engines. (IMI Titanium, Ltd. was a British producer-manufacturer that now operates as Timet UK.) Some of these mentioned alloys have found use in airframes. Other alloys used or evaluated extensively in aerospace, missile and space, and other high-performance applications have included Ti-6V-2Sn-2Zr2Cr-2Mo + Si, Ti-6Al-6V-2Sn, Ti-10V-2Fe3A1, and Ti-13V-11Cr-3A1. The latter alloy also is called BI2OVCA. It was the first of a line of metastable beta alloys, although it is now considered somewhat obsolete when compared with most contemporary alloys. Chemical processing operations have been concerned principally with the unalloyed grades, palladium-containing pure grades, and Ti-6Al4V. Ti-3A1-8V-6Cr-4Zr-4Mo (also called beta C) was approved for use in deep, sour-well technology. Other alloys are in various stages of use. The reader may wish to refer to Appendix A (“Summary Table of Titanium Alloys”) and/or Appendix B (“Titanium Alloy Datasheets”) for more specific information on the types of alloys available and their possible applications.

Application and Control of Titanium Alloys Rotating components such as jet-engine blades and gas turbine parts require titanium alloys that maximize strength efficiency and metallurgical stability at elevated temperatures. These alloys also must exhibit low creep rates along with predictable behavior with respect to stress rupture and low-cycle fatigue. To reproducibly provide these properties, stringent user requirements are specified to ensure controlled, homogeneous microstructures and total freedom from melting imperfections such as alpha segregation, high-density or low-density tramp inclusions, and unhealed ingot porosity or pipe. The greater the control is, however, the greater the cost will be. Aerospace pressure vessels similarly require optimized strength efficiency, although at

lower temperatures. Required auxiliary properties include weldability and predictable fracture toughness at cryogenic-to-moderately elevated temperatures. To provide this combination of properties, stringent user specifications require controlled microstructures and freedom from melting imperfections. For cryogenic applications, the interstitial elements oxygen, nitrogen, and carbon are carefully controlled to improve ductility and fracture toughness. Alloys with such controlled interstitial element levels are designated ELI (extra-low interstitial), for example, Ti-6Al-4V-ELI. Aircraft structural applications, along with high-performance automotive and marine applications, also require high-strength efficiency, which normally is achieved by judicious alloy selection combined with close control of mill processing. However, when the design includes redundant structures, when operating environments are not severe, when there are constraints on the fabrication methods that can be used for specific components, or when there are low operational risks, selection of the appropriate alloy and process must take these factors into account. There are instances of less highly loaded structures in which titanium normally is selected because it offers greater resistance to temperature effects than aluminum does or greater corrosion resistance than brass, bronze, and stainless steel alloys provide. In such cases, commercial availability of required mill products and ease of fabrication customarily dictate selection. Here, one of the grades of unalloyed titanium usually is chosen. Formability (as with tubes) frequently is a characteristic required of this class of applications.

Titanium Alloy Systems Availability In the United States, 70 to 80% of the demand for titanium was from the aerospace industries during most of the first 50 years that titanium alloys were available commercially. About 20 to 30% was from industrial applications. In the last decade of the twentieth century, demand from nonaerospace industries severely impacted the availability of titanium and its alloys for more traditional high-performance applications at times. For a while, titanium golf clubs were in great demand. Bicycles with titanium frames became quite popular. The golf club market proved to be less durable than expected, and demand is driven by the aerospace applications once again. In view of the fluidity of the market, any speculation or report about titanium application volume would best be gotten from sources such as trade associations, trade journals, or specialized reports prepared by consulting firms. Several dozen common titanium alloys are readily available. However, as is the case in many industries, there are often significant variations in the specifications to which a given organization purchases, or designs with, titanium alloys. To a large extent, aerospace appli-

cations are the prime cause of titanium alloy and process development and, thus, material availability. The industry has been cyclical in nature and has operated at peak capacity only a few times in the approximately five decades since titanium was introduced as a commercial material. The business conditions of the last decade of the twentieth century led inexorably to a consolidation of the producers of titanium alloys. Further consolidation may be expected in the alloy specifications that govern the use of titanium. Common specification agreements are in the works whereby a single specification may serve as a buying guide for a given composition. Single specification requirements for a given alloy should not be considered to grant a common design data base for a material, however. Actual design data will continue to be within the purview of titanium users such as gas turbine engine and airframe manufacturers. Commonality of purchasing requirements via common specifications should eventually drive design data to a more common framework. The data provided in this book and most handbooks (examples can be found in Appendix K) are meant to be typical data, not design data.

Evolution of Casting and Precision Forging While total titanium availability has remained relatively flat for many years, the availability of castings has risen remarkably. In addition to intricate castings, precision forgings, including near-net shape (NNS) forgings, and superplastic forming/forging have shown promise for extending the application of titanium alloys. Figure 2.5 illustrates schematically the areas of titanium usage in an advanced fighter airframe, that of the F-22 Raptor. Only the areas of titanium usage are shown. In the F-22, some 42% of all structural weight will be of titanium. In the aft fuselage alone, almost two-thirds of the weight is titanium. Titanium castings (Fig. 2.6) represented only 6% of the weight of aircraft gas turbines in the 1980s, but casting usage was expanded in the 1990s, especially when casting vendors moved to reduce costs to engine manufacturers. Powder parts may be available in limited quantities, but they are currently and principally restricted to somewhat more exotic alloys and/or applications. Titanium usage may increase for advanced gas turbines, but there are not that many new turbines in the works, and there is a tendency to look for “low-cost” materials/components for newer designs. Airframes represent a largevolume application for titanium, and titanium usage for airframes increased steadily through the latter decades of the twentieth century, as seen in Fig. 2.7. Military applications remain

10 / Titanium: A Technical Guide the largest volume uses for titanium, and Tables 2.3 and 2.4 show the airframe and/or engine titanium requirements as well as the buy weights for some commercial and military applications. It was not until about 1965 that nonaerospace usage accounted for a significant fraction of the titanium production. Continued modest growth has been taking place since then in many areas, including biomedical engineering, marine and chemical applications, automotive, and sporting goods. Table 2.5 provides a list of some titanium applications.

The Role of Processing

the same alloy in the same general temperature region of the phase diagram as that where the heat treatment is carried out. However, the

Titanium alloys are particularly sensitive to the processing conditions that precede their use in service applications. Processing denotes the wrought, cast, or powder methods used to produce the alloy in the appropriate condition for the intended application, as well as the heat treatments that are applied to the alloy. Heat treatment of alpha-beta alloys seems to produce microstructures that are substantially the same as structures produced, for example, by forging

Wings • Side of body fitting: titanium HIP casting • Spars: Front, titanium Intermediate, resin transfer molded composite and titanium Rear, composite and titanium

Fig. 2.6 Corp.

Aft fuselage • Forward boom: titanium welded • Bulkheads/Frame: titanium • Upper skins: titanium and composite

Fig. 2.5

Typical titanium alloy casting for aircraft gas turbine use. Courtesy of Precision Castparts

Mid fuselage • Skins: composite and titanium • Bulkheads and frames: titanium aluminum, composite

Some areas of titanium use in the F-22 Raptor advanced fighter aircraft

Fig. 2.7 Table 2.4

Titanium usage in Boeing aircraft from the first commercial jet to the Boeing 757

Titanium buy weights for commercial and military aircraft Titanium buy weight

Aircraft/engine(a)

Table 2.3 Military aircraft (including engines) titanium requirements Titanium buy weight Aircraft/engine(a)

A-10/(2) TF-34 F-5E/(1) J85 F-5G/(1) F404 F-14/(2) TF-30 F-15/(2) F-100 F-16/(1) F-100 F-18/(2) F-404 C-130/(4) T-56 C-5B/(4) TF-39 B-1B/(4)F101-GE-102 KG-10/CF-6-50 CH-53E/(3) T-64 CH-60/(2) T-700 S-76/(2) A11.250 AH-64/(2) T-700

kg

1,814 635 1,089 24,630 29,030 3,085 7,620 499 24,812 90,402 32,206 8,800 2,041 544 635

lb

4,000 1,400 2,400 54,300 64,000 6,800 16,800 1,100 54,700 199,300 71,000 19,400 4,500 1,200 1,400

(a) Typical uses are A-10 ballistic armament; structural forgings and wing skins for F-14 and F-15 aircraft; rotor parts for helicopter blade systems; B-1B fracture-critical forgings and wing carry-through section; and rotor discs, blades, and compressor cases on various engines.

Fairchild A-10 Northrop F-5 Grumman F-14 McDonnell Douglas F-15 General Dynamics F-16 McDonnell Douglas F-18 Lockheed C-130 Lockheed C-5B Rockwell B-1B 707/(4) JT3 727/(3) JT8 737-200/(2) JT8 737/300/(3) CFM-56 747/(4) JT-9 757/(2) PW2037 757/(2) RB211/535 767/(2) JT-9 767/(2) CF-6 MD-80 (2) JT8-217 DC-10/(3) CF-6 A300/(2) CF-6 A310/(2) CF-6

kg

lb

862 408 18,870 24,494 861 6,214 454 6,804 82,646 4,445 4,309 3,810 3,810 42,593 12,746 12,973 17,554 11,703 6,260 32,387 6,350 6,350

1,900 900 41,600 54,000 1,800 13,700 1,000 15,000 182,200 9,800 9,500 8,400 8,400 93,900 28,100 28,600 38,700 25,800 13,800 71,400 14,000 14,000

(a) Airframe only; slight variations by specific model. Product forms purchased include sheet, plate, bar, billet, and extrusions.

Introduction to Selection of Titanium Alloys / 11 Table 2.5

Some titanium applications

Aerospace Gas turbine engines Aircraft structures Spacecraft Helicopter rotors

Automotive Body panels Connecting rods Valves and valve springs Rocker arms

Power generation Gas turbines Steam turbines Piping systems Heat exchangers Flue gas desulphurization systems

Marine Surface ship hulls Deep-sea submersibles Pleasure boat components Racing yacht components Shipboard cooling systems Ship propellers Service water systems Ducting Fire pumps Water jet propulsion systems

Chemical processing industries Pressure and reaction vessels Heat exchangers Pipe and fittings Liners Tubing Pumps Condensers Valves, ducting, and filters Agitators

Fashion and apparel Eyeglasses Jewelry Watches Writing instruments

properties of wrought stock produced by deformation of the alloy at a high temperature generally seem to be better than those produced by heat treatment alone to effect the desired structure. Furthermore, the degree of work placed into the alloy seems to be a controlling factor in the attainment of optimum properties. (Bar stock does not have the same properties as a forged disk.) Once the alloy composition is selected, the properties of titanium alloys are linked inextri-

Oil, gas, and petroleum processing Tubing and pipe Liners Springs Valves Risers Biomedical Artificial joint prostheses Bone plates, intramedullary rods, etc. Heart valves Pacemakers Dental implants Attachment wire Surgical instruments Wheelchairs Architectural Roofing Window frames Eaves and gables Railings Ventilators

cably to the nature of the processing applied to them. One of the more considerable recent processing challenges was to develop satisfactory heat treatment procedures for optimizing the properties and the microstructure of cast titanium alloys after they have been hot isostatically pressed. Heat treatments and fabrication conditions to consolidate titanium powder or to make components from titanium aluminides represent ongoing challenges to the process technology involving titanium.

Sports Golf clubs Bicycle frames, gears, etc. Lacrosse sticks Racing wheelchairs Horseshoes Tennis rackets Scuba gas cylinders Skis Pool cues Miscellaneous Shape memory alloys Pollution control systems Hand tools Desalination systems Military vehicle armor Hunting knives Backpack cookware

Property Data Properties of commercially pure and alloyed titanium may vary from the data presented in Table 2.1. For specific information on many of the commonly used Ti CP grades and alloys, refer to Materials Properties Handbook: Titanium Alloys, published by ASM International (Appendix K provides a listing of references for additional information).

Titanium: A Technical Guide Matthew J. Donachie, Jr., p13-24 DOI:10.1361/tatg2000p013

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 3

Understanding the Metallurgy of Titanium Crystal Structure and Alloy Types METALS generally have simple atomic arrangements compared to ceramics and plastics. Metal atoms, which can be pictured as hard spheres for convenience, are arranged on crystal lattices. A grain is formed by the aggregate of a group of similar crystals of a given metal (or alloy). The orientation of lattice aggregates generally differs over distance and so a metal such as titanium is composed of many grains unless deliberately grown as a single crystal. Within each grain the orientation of the lattice structure is the same with distance but across a grain boundary the next grain will have a different spatial orientation. In addition to the existence of grains and concurrent grain boundaries, titanium is an allotropic element; that is, it exists in more than one crystallographic form. At room temperature, titanium has a hexagonal close-packed (hcp) crystal structure, which is referred to as “alpha” phase. This structure transforms to a body-centered cubic (bcc) crystal structure, called “beta” phase, at 888 °C (l621 °F). Beta phase and alpha phase hard-sphere models are shown in Fig. 1.1. It is common to separate the alloys into four categories, referring to the phases normally present. The alloy categories generally are called:

• • • •

becomes an alpha alloy. Crystal strucure and grain structure (i.e., microstructure) are not synonymous terms. Both must be specified to completely identify the alloy and its expected mechanical, physical, and corrosion behavior. The important fact to keep in mind is that, while grain shape and size affect behavior, the crystal structure changes (from alpha to beta and back again) that occur during processing play a major role in defining titanium properties. Chapter 12 covers this subject in detail.

Phase Diagrams—Road Maps for Alloy Relationships. The phase relationships in alloy systems can be represented by phase diagrams. When more than two elements are present, it is difficult to show the quantitative relationships. Pseudobinary phase diagrams, however, are a useful way to show behavior, especially on a comparative basis. Figure 3.1 shows the compositions of some U.S. alloys marked on such a road map, a pseudobinary phase diagram where the compo-

Alpha Near-alpha Alpha-beta (alpha-plus-beta) Beta

Sometimes a category of near-beta is also considered. These categories denote the general type of microstructure after processing. (Microstructure refers to the phases and grain structure present in a metallic component.) The categories listed describe the origin of the microstructure in terms of the basic crystal structure favored by an alloy composition. Thus, an alloy with only alpha phase present

Fig. 3.1

Some U.S. alloy compositions relative to a pseudobinary titanium phase diagram

14 / Titanium: A Technical Guide sition axis represents the amount of beta phase stabilizing element. The diagram clearly shows that alloys such as Ti-6Al-2Sn-4Zr-2Mo are “near-alpha” alloys because they are barely into the alpha-plus-beta region of the phase diagram. Alloys such as Ti-13V-11Cr-3Al, however, are clearly in the high end of the alphaplus-beta region and, owing to slow transformation kinetics, will remain beta on cooling from higher temperatures. The Mf and Ms lines introduced into the diagram refer to nonequilibrium martensitic phases introduced dur-

ing “rapid” cooling, as in steel. Martensitic phases are discussed shortly. Crystal Structure Behavior. An alpha alloy (so described because its chemistry favors alpha phase) does not normally form beta phase on heating. A near-alpha (sometimes called “superalpha”) alloy forms only limited beta phase on heating, and so it may appear microstructurally similar to an alpha alloy when viewed at lower temperatures. An alpha-beta alloy is one for which the composition permits complete transformation to beta on heating but transforms back to alpha plus retained and/or transformed beta at lower temperatures. A near-beta or beta alloy composition is one that tends to retain, indefinitely at lower temperatures, the beta phase formed at high temperatures. However, the beta that forms on initial cooling to room temperature is metastable. Dependent on chemistry, it may precipitate secondary phases during heat treatment. Microstructures show variations in the morphological development of the alpha phase and

the beta phase, which are dependent on alloy chemistry, prior work, temperature from which cooled, and rate of cooling. Coarse and fine acicular structures can be produced, but equiaxed structures also are possible. (This topic is discussed later in this chapter.) Typical titanium microstructures are shown in Fig. 3.2. The microstructures shown are intended to be representative but definitely not all-inclusive because the actual microstructure depends on chemistry and processing. Figures 3.3 and 3.4 give some additional illustrations of the effect of prior temperature (and cooling rate) on microstructure of a near-alpha and an alphabeta titanium alloy.

Effects of Alloying Elements Alloying elements generally can be classified as alpha stabilizers or beta stabilizers. Alpha stabilizers, such as aluminum, oxygen, and

(a)

(a)

(b)

(c) (b)

(d) Typical microstructures of alpha, alpha-plusbeta, and beta titanium alloys. (a) Equiaxed α in unalloyed Ti after 1 h at 699 °C (1290 °F). (b) Equiaxed α + β. (c) Acicular α + β in Ti-6Al-4V. (d) Equiaxed β in Ti-13V-11Cr-3Al

Fig. 3.2

(c)

Fig. 3.3

Microstructures of an annealed near-alpha alloy (Ti-8Al-1Mo) after cooling from different areas of the phase field. (a) Acicular alpha. (b) Equiaxed alpha and intergranular beta. (c) Fine alpha-beta structure

Understanding the Metallurgy of Titanium / 15 Air cooled

(a)

Water quenched

(b)

(c)

(d)

(e)

Pseudo phase diagram plus microstructures of an annealed alpha-beta alloy (Ti-6Al-4V) after cooling from different areas of the phase field. (a) Diagram with Ti-6Al-4V composition indicated. (b) Acicular alpha (transformed beta) with prior beta grain boundaries. (c) Alpha prime (martensite) matrix with beta (dark) and prior beta grain boundaries. (d) Grains of primary alpha (light) in a matrix of transformed beta containing acicular alpha. (e) Equiaxed primary alpha in a matrix of alpha prime (martensite)

Fig. 3.4

nitrogen, increase the temperature at which the alpha phase is stable. On the other hand, beta stabilizers, such as vanadium and molybdenum, result in stability of the beta phase at lower temperatures. The transformation temperature from alpha-plus-beta or from alpha to all beta is known as the beta transus temperature. The beta transus is defined as the lowest equilibrium temperature at which the material is 100% beta. The beta transus is critical in deformation processing and in heat treatment, as described below. Note that the beta transus for Ti-6Al-4V is shown in Fig. 3.4. Below the beta transus temperature, titanium is a mixture of alpha-plus-beta if the material contains some beta stabilizers; otherwise it is all alpha if it contains limited or no beta stabilizers. The beta transus is important because processing and heat treatment often are carried out with reference to some incremental temperature above or below the beta transus. Alloying elements that favor the alpha crystal structure and stabilize it by raising the beta transus tem-

perature include aluminum, gallium, germanium, carbon, oxygen, and nitrogen. Two groups of elements stabilize the beta crystal structure by lowering the transformation temperature. The beta isomorphous group consists of elements that are miscible in the beta phase, including molybdenum, vanadium, tantalum, and columbium. The other group forms eutectoid systems with titanium, having eutectoid temperatures as much as 333 °C (600 °F) below the transformation temperature of unalloyed titanium. The eutectoid group includes manganese, iron, chromium, cobalt, nickel, copper, and silicon. Two other elements that often are alloyed in titanium are tin and zirconium. These elements have extensive solid solubilities in alpha and beta phases. Although they do not strongly promote phase stability, they retard the rates of transformation and are useful as strengthening agents. The effects and ranges of some alloying elements used in titanium are indicated in Table 3.1.

The transformation temperature (beta transus, or completion of transformation to beta on heating) is strongly influenced by:

• The interstitial elements oxygen, nitrogen, •

and carbon (alpha stabilizers), which raise the transformation temperature Hydrogen (beta stabilizer), which lowers the transformation temperature

Table 3.1 Ranges and effects of some alloying elements used in titanium Alloying element Approximate range, wt %

Aluminum Tin Vanadium Molybdenum Chromium Copper Zirconium Silicon

2–7 2–6 2–20 2–20 2–12 2–6 2–8 0.2–1

Effect on structure

Alpha stabilizer Alpha stabilizer Beta stabilizer Beta stabilizer Beta stabilizer Beta stabilizer Alpha and beta strengthener Improves creep resistance

16 / Titanium: A Technical Guide

• Metallic impurity or alloying elements,

which can either raise or lower the transformation temperature

The role of the interstitial elements oxygen, nitrogen, and carbon was already mentioned. The substitutional alloying elements, such as tantalum and vanadium, also play an important role in controlling the microstructure and properties of titanium alloys. Tantalum, vanadium, and columbium are beta isomorphous (i.e., have similar phase relations) with bcc titanium. Titanium does not form intermetallic compounds with the beta isomorphous elements. Eutectoid systems are formed with chromium, iron, copper, nickel, palladium, cobalt, manganese, and certain other transition metals. These elements have low solubility in alpha titanium and decrease the transformation temperature. They usually are added to alloys in combination with one or more of the beta isomorphous elements to stabilize the beta

phase and prevent or minimize formation of intermetallic compounds that can occur during service at elevated temperature. Zirconium and hafnium are unique in that they are isomorphous with both the alpha and beta phases of titanium. Tin and aluminum have significant solubility in both alpha and beta phases. Aluminum increases the transformation temperature significantly whereas tin lowers it slightly. Aluminum, tin, and zirconium commonly are used together in alpha and near-alpha alloys. In alpha-beta alloys, these elements are distributed approximately equally between the alpha and beta phases. Almost all commercial titanium alloys contain one or more of these three elements because they are soluble in both alpha and beta phases, and particularly because they improve creep strength in the alpha phase. Many more elements are soluble in beta titanium than in alpha. Beta isomorphous alloying elements are preferred as additions because they do not form intermetallic compounds. However, iron, chromium, manganese, and other compound formers sometimes are used in beta-rich alpha-beta alloys or in beta alloys because they are strong beta stabilizers and improve hardenability and response to heat treatment. Nickel, molybdenum, and palladium improve the corrosion resistance of unalloyed titanium in certain media.

Transformations and Secondary Phase Formation

Fig. 3.5

Microstructure of acicular martensite in titanium alloy (Ti-12V)

Intermetallic Compounds and Other Secondary Phases. Intermetallic compounds and transient secondary phases are formed in titanium alloy systems along with microstructural variants of the traditional beta and alpha phases. The more important secondary phases, historically, have been omega and al-

Microstructure of an alpha-beta titanium alloy (Ti-6Al-4V) after slow cooling from above the beta transus. The white plates are α, and the dark regions between them are β. This is a typical Widmanstätten structure. Optical micrograph; 500x

Fig. 3.6

pha-2, chemically written as Ti3Al. Omega phase has not proven to be a factor in commercial systems using present-day processing practice. Alpha-2 has been considered to be a concern in some cases of stress-corrosion cracking. (Most present interest in alpha-2 centers on its use as a matrix for a high-temperature titanium alloy where stress-corrosion may not be a factor.) When phase transformations occur, they can be diffusion controlled and moderately fast or they can be diffusionless (no composition change) and very rapid. Diffusionless transformations usually lead to nonequilibrium phases. (Martensites in steel are phases formed by a diffusionless transformation.) Martensitic nonequilibrium phases exist in some titanium alloys. Martensites and Transformed Beta (Acicular Alpha). The decomposition of beta phase in titanium alloys can take place by martensitic transformations, and this frequently happens in the alpha-beta alloys. Nonequilibruium martensitic phases are produced in alpha-beta alloys as a function of alloy chemistry and processing. There are several of these martensite types formed in titanium. The betato-martensite transition is responsible for an acicular (plate-like) structure in quenched and/or quenched and aged titanium alloys (Fig. 3.5). Other acicular or lenticular plate-like structures can appear in titanium alloys without the formation of martensite. Figure 3.6 shows alpha platelets formed by slow cooling from the beta region. Since plate-like structures can be alpha or martensite, it is necessary to fully characterize the behavior of any given alloy. Figure 3.7 shows the range of structure that can exist in a superalpha alloy (a description of superalpha alloys is presented later in this chapter). The alpha that forms from beta is invariably acicular but with different degrees of fineness of structure. For Ti-6Al-2Sn-4Zr-2Mo-0.2Si, it can be seen that a very fine alpha (Fig. 3.7a) can result from transformation of beta, or a relatively coarse alpha platelet structure (Fig. 3.6 and 3.7b) can be formed. It may be difficult for the casual observer to recognize the difference between martensitic transformed beta and plate-like alpha formed from beta. Prior knowledge, including alloy chemistry and processing condition, is necessary to properly identify the phase present. Although a number of martensites were reported over the years, the two principal martensites turned out to be alpha prime and alpha double prime. Alpha prime, appearing as an acicular phase, is hexagonal in crystal lattice structure but similar in microstructural appearance to acicular alpha. (Acicular alpha is discussed in the section “Microstructural Development in Titanium Alloys” in this chapter). Alpha double prime is a supersaturated orthorhombic phase. Alpha-prime and alpha-doubleprime martensites are brought out by cooling, and they decompose, on subsequent aging, to alpha and beta phases. Cooling rate plays an important role in the creation of the martensitic phases.

Understanding the Metallurgy of Titanium / 17

βtr

α+β

0.1 mm

(b)

(a)

Fig. 3.7

Optical micrograph of a titanium alloy (Ti-6Al-2Sn-4Zr-2Mo-0.2Si) after (a) 2 h/1024 °C (1876 °F)/air cool, and (b) 2 h/968 °C (1774 °F)/air cool

Microstructural Ranges in Titanium Alloys. A graphic illustration of the range of microstructural transformation variations that can occur in an alpha-beta alloy, such as Ti-6Al-4V, is shown in Fig. 3.8. As can be seen, the morphology (shape/location) of the phases changes with prior treatments. The al-

(a)

pha phase present at the time of cooling (primary alpha) can remain relatively globular (equiaxed), but the transformed beta (martensites or alpha) can be very acicular or elongated. The amount of equiaxed alpha and the coarseness or fineness of the transformed beta products affect the alloy properties of titanium.

(b)

Metastable beta can show more variety in decomposition than does the supersaturated alpha or martensitic alpha structure. The omega phase can form from beta, as can alpha phase and a low-solute-content beta phase. Other intermetallic compounds also can form, and, under certain circumstances, ordering of the beta phase can occur. (Ordering removes the randomness in atom location that normally exists and puts atoms in specific locations.) Hardenability is a term much used in steel technology to describe the ability to create a level of hardness where it is desired by achieving a specific amount of martensite. The same concept is sometimes used in titanium technology. Hardenability of a titanium alloy is a phrase that refers to its ability to permit full transformation of the alloy to transformed beta (martensites, alpha) or to retain beta to room temperature.

Titanium Groupings

(c)

(d)

General Background. Although the four categories or classes of titanium have been described, a slightly different classification or grouping is sometimes used in commercial practice. For example, it is common to group titanium materials as:

• • • •

(e)

(f)

Microstructure of an alpha-beta titanium alloy (Ti-6Al -4V) in representative metallurgical conditions. (a) Equiaxed α and a small amount of intergranular β. (b) Equiaxed and acicular α and a small amount of intergranular β. (c) Equiaxed α in an acicular α (transformed β) matrix. (d) Small amount of equiaxed α in an acicular α (transformed β) matrix. (e) Plate-like acicular α (transformed β); α at prior β grain boundaries. (f) Blocky and plate-like acicular α (transformed β); α at prior β grain boundaries

Fig. 3.8

Unalloyed (CP) Alpha and near-alpha Alpha-beta Metastable beta

Table 2.2 lists the room-temperature tensile property levels and the chemistries for some commercial and semicommercial titanium grades (i.e., kinds) and alloys currently available. A more comprehensive listing of compositions for many CP grades is given in Table 3.2. A similar comparison listing for commercial alpha, near-alpha, alpha-beta, and beta alloys is given in Table 3.3.

18 / Titanium: A Technical Guide The different titanium families or groupings have different characteristics, as would be expected. Figure 3.9 shows schematically the main characteristics of the titanium alloy family groupings (excluding commercial purity titanium) with a few alloy compositions indicated for reference. Unalloyed titanium, generally known as commercial purity (CP) titanium is the weakest but most corrosion-resistant version of the metal. The interstitial elements oxygen and nitrogen greatly strengthen “pure” titanium. CP titanium takes advantage of the interstitial hardening of oxygen and the effects of small additions of other elements (e.g., iron and palladium) to provide for various grades of the metal to fit a variety of applications. The primary difference between CP grades is oxygen and iron content, and oxygen content is the principal regulator of tensile properties. (Refer to Appendix B for more information on grades.) Grades of higher purity (lower interstitial content) are lower in strength and hardness, and have a lower transformation temperature, than those higher in interstitial content. Unfortunately, although oxygen and nitrogen are not only strengtheners of titanium, they can be difficult to keep out of titanium alloys due to the high solubility of the interstitial elements. Thus, atmospheres containing oxygen or nitrogen create problems that are not concerns with most other metals. Oxidation is always of concern in elevated-temperature operation. Heating titanium in air at high temperature results not only in oxidation but also in solid-solution hardening of the surface as a result of inward diffusion of oxygen (and nitrogen). When titanium and its alloys are heated in an oxygen- or nitrogen-containing environment, a surface-hardened zone is formed. This surface-hardened layer is referred to as “alpha case” because oxygen and nitrogen stabilize the alpha phase. Alpha case (the “air-contamination layer”) is hard and britTable 3.2

tle and invariably detrimental to service application. Normally, this layer is removed by chemical milling, pickling, or machining or by other mechanical means prior to placing a part in service because the presence of alpha case drastically reduces fatigue strength and ductility. Customarily, CP titanium is selected for its excellent corrosion resistance, especially in applications where high strength is not required. Yield strengths of commercially pure grades may vary from about 170 MPa (25 ksi) to about 480 MPa (70 ksi) simply as a result of variations in the interstitial and impurity levels, with strength increasing as the oxygen/nitrogen (and iron) contents increase (Table 2.2). Alpha and Near-Alpha (Superalpha) Alloys. Alpha alloys are alloys with relatively large amounts of alpha stabilizer and low concentrations of beta stabilizers. Such alloys generally are more resistant to creep at high temperature than alpha-beta or beta alloys. Within the alpha and near-alpha systems, those alpha alloys that contain aluminum, tin, and/or zirconium are preferred for high-temperature and cryogenic applications. However, ductility and toughness of alpha-rich alloys are compromised at cryogenic temperatures unless interstitial content is reduced. Reduced-interstitial-level titanium alloys are designated “extra low interstitial” (ELI). The higher cost, ELI alpha alloys retain ductility and toughness at cryogenic temperatures. Ti-5Al-2.5Sn-ELI was one alpha alloy used extensively in cryogenic applications. Because there is limited phase transformation under normal heat treatment conditions (structure stays all alpha or almost all alpha), alpha alloys usually cannot be strengthened by heat treatment. Near-alpha or superalpha alloys are made by introducing some amount of beta stabilizing elements to an alpha-alloyed chemistry. The superalpha alloys are somewhat heat treatable. Grain structure changes in alpha and superalpha alloys are made by inducing recrystal-

lization through cold work and annealing. Residual stresses induced by cold working of alpha and superalpha alloys are relieved by stress-relief annealing or recrystallization annealing. Microstructure changes are effected by modifications in the maximum solution-treatment temperature and the cooling rates from solution heat treatment. Reference should be made to Fig. 3.7, which shows optical micrographs of a superalpha titanium alloy (Ti-6Al2Sn-4Zr-2Mo-0.1Si) as influenced by changes in the heating and cooling conditions. Ti-8A1-1Mo-1V and Ti-6A1-2Nb-lTa-0.8Mo are examples of alpha alloys that contain small additions of beta stabilizers. These alloys have been classed as near-alpha or superalpha alloys. The modest amount of beta-favoring elements provides for a very small amount of beta to be formed in the microstructure during processing. Although the alloys contain some retained beta phase after heating and cooling, they consist primarily of alpha phase and tend to behave more like conventional alpha alloys than alpha-beta alloys. Because the alpha phase is the more creep resistant of the phases in titanium alloys, superalpha alloys have outstanding creep strength. Because aluminum is frequently used to achieve the superalpha structure, such alloys may have a greater tendency to produce the alpha-2 phase that has been implicated in hot-salt stress-corrosion cracking of titanium alloys. In the superalpha alloys, stress-corrosion resistance is limited and care must be exercised in the use of such materials. One benefit of alpha alloys is their intrinsically good weldability, which stems from the fact that alpha alloys generally are insensitive to heat treatment. However, the alpha alloys usually have poorer forgeability and narrower forging temperature ranges than alpha-beta or beta alloys, particularly at temperatures below the beta transus. This poorer forgeability is manifested by a greater tendency for center bursts or surface cracks to occur, which means

Comparison of some commercially pure titanium mill products Tensile properties(a) Chemical composition, % max

Designation

JIS Class 1 ASTM grade 1 (UNS R50250) DIN 3.7025 GOST BT1-00 BS 19–27t/in.2 JIS Class 2 ASTM grade 2 (UNS R50400) DIN 3.7035 GOST BT1-0 BS 25–35t/in.2 JIS Class 3 ASTM grade 3 (UNS R50500) ASTM grade 4 (UNS R50700) DIN 3.7055 ASTM grade 7 (UNS R52400) ASTM grade 11 (UNS R52250) ASTM grade 12 (UNS R53400)

C

H

O

N

Fe

… 0.10 0.08 0.05 … … 0.10 0.08 0.07 … … 0.10 0.10 0.10 0.10 0.10 0.10

0.015 (c) 0.013 0.008 0.0125 0.015 (c) 0.013 0.010 0.0125 0.015 (c) (c) 0.013 (c) (c) 0.015

0.15 0.18 0.10 0.10 … 0.20 0.25 0.20 0.20 … 0.30 0.35 0.40 0.25 0.25 0.18 0.25

0.05 0.03 0.05 0.04 … 0.05 0.03 0.06 0.04 … 0.07 0.05 0.05 0.06 0.03 0.03 0.03

0.20 0.20 0.20 0.20 0.20 0.25 0.30 0.25 0.30 0.20 0.30 0.30 0.50 0.30 0.30 0.20 0.30

Ultimate strength Other

Total others

… … … … … … … 0.10 max … … … … … … … … … 0.30 max … … … … … … … … … … 0.12–0.25 Pd … 0.12–0.25 Pd … 0.2–0.4 Mo, … 0.6–0.9 Ni

Yield strength

Minimum elongation,

MPa

ksi

MPa

ksi

%

275–410 240 295–410 295 285–410 343–510 343 372 390–540 382–530 480–617 440 550 460–590 343 240 480

40–60 35 43–60 43 41–60 50–74 50 54 57–78 55–77 70–90 64 80 67–85 50 35 70

165(b) 170–310 175 … 195 215(b) 275–410 245 … 285 343(b) 377–520 480 323 275–410 170–310 380

24(b) 25–45 25..5 … 28 31(b) 40–60 35..5 … 41 50(b) 55–75 70 47 40–60 24..5–45 55

27 24 30 20 25 23 20 22 20 22 18 18 20 18 20 24 12

(a) Unless a range is specified, all listed values are minimums. (b) Only for sheet, plate, and coil. (c) Hydrogen limits vary according to product form as follows: 0.0150H (sheet), 0.0125H (bar), and 0.0100H (billet).

Understanding the Metallurgy of Titanium / 19 that small reduction steps and frequent reheats must be incorporated in forging schedules. Isothermal forging processes can reduce this problem. (More information can be found in Chapter 5.) Alpha-Beta Alloys. When a blend of beta-favoring and alpha-favoring alloy elements is added to titanium, alloys with structures in the alpha-beta range may form. Alloys in alpha-beta systems contain one or more alpha stabilizers (e.g., aluminum) or alpha-soluble elements plus one or more beta stabilizers (e.g. vanadium, molybdenum) in larger amounts than in near-alpha alloys. By moving alloy

Table 3.3(a)

chemistry away from the alpha solvus phase boundary, these alloys form significant beta phase when heated. When sufficient beta formers are present, it is relatively easy to exceed the beta transus by heating, and the alloy will be all beta before subsequent cooling. The alpha-beta alloys can retain significant untransformed beta after solution treatment and cooling. The transformation of lower-temperature alpha to higher-temperature beta phase, which takes place upon heating alpha-beta titanium alloys, is complete if the heating temperature goes above the beta transus. The formation of a little beta or a complete structure of beta per-

mits alpha-beta alloys to be strengthened by solution treating (exceeding the beta transus, or at least producing significant beta phase for subsequent transformation) and aging (heating to produce further change in the transformed beta—martensites, acicular alpha—and the retained beta). The specific amount of beta available for transformation from a fixed temperature depends on the quantity of beta stabilizers present and on processing conditions. A wide variety of microstructures can be generated in alpha-beta alloys by adjusting the thermomechanical process parameters. It should be noted that beta

Compositions of various alpha and near-alpha titanium alloys Impurity limits, wt% max Alloying elements, wt%(a)

Max total other Product specification

N

C

H

Fe

O

s or max each

Al

Sn

Zr

Mo

0.05 0.05

0.08 0.08

0.01 0.012

0.2 0.2

0.2 0.2

0.4 total others 0.4 total others

… …

… …

… …

… …

2.0–3.0Cu 2.0–3.0Cu

0.05 0.05

0.08 0.08

0.05 0.05 0.05

0.02 0.5 0.2 … 0.02 0.5 0.2 0.005Y(b) Impurity limits same as AMS 4910 0.10 0.02 0.4 0.2 (b) 0.10 0.0125 0.4 0.2 (b) 0.10 0.015 0.3 0.2 0.15Si

4.0–6.0 4.50–5.75 4.00–6.00 4.00–6.00 4.00–6.00 4.00–6.00

2.0–3.0 2.00–3.00 2.00–3.00 2.00–3.00 2.00–3.00 2.00–3.00

… … … … … …

… … … … … …

… … … 0.12–0.25Pd … …

Ti-5Al-2.5Sn-ELI (UNS designation R54521) AMS 4909 (plate, sheet, strip)

0.035

0.05

0.0125

0.25

0.12

4.50–5.75 2.00–3.00

…

…

…

AMS 4924 (bars, forgings)

0.035

0.05

0.0125

0.25

0.12

4.70–5.6

0.015

0.30

0.02

Ti-2.5Cu (AECMA designation, Ti-P11) Bars (AECMA standards prEN2523 and 2521) Sheet or strip (prEN2128) and forgings (prEN2522 and 2525) Ti-5Al-2.5Sn (UNS designation R54520) DIN17851 (alloy WL3.7115) AMS 4910 (plate, sheet, strip) AMS 4926 (bars, rings) and AMS 4966 (forgings) ASTM B 265 (plate, sheet, strip) ASTM B 348 (bar, billet) and ASTM B 381 (forgings) 3620-TA7 (Chinese)

Others

O + Fe = 0.32, 0.005Y, 0.05 each, 0.3 total O + Fe = 0.32, others(b) 0.15Si

2.00–3.00

…

…

…

4.00–5.00 2.00–3.00

…

…

…

0.005Y, (b)

8 7.35–8.35

… …

… …

1 0.75–1.25

1V 0.75–1.25V 0.75–1.25V

VT51 (U.S.S.R.)

0.05

0.10

Ti-8Al-1V-1Mo (UNS R54810)(c) AECMA, Ti-P66 AMS 4915, 4916, 4933 (rings), 4955 (wire), 4972 (bars, forgings), 4973 (forgings) MIL-R-81588 (ring, wire)

0.05

0.08

0.015

0.035

0.005

0.20

0.12

0.3 total

7.35–8.35

…

…

0.75–1.25

Ti-6242 (UNS R54620)(c) AMS 4919, 4975, 4976

0.05

0.05

0.0125

0.25

0.15

5.50–6.50

1.8–2.2

3.6–4.4

1.8–2.2

…

U.S. government (military)

0.04

0.05

0.015

0.25

0.15

(d), 0.1Si, 0.005Y 0.13Si, 0.3 max others

5.50–6.50

1.8–2.2

3.6–4.4

1.8–2.2

…

Ti-6Al-2Nb-1Ta-0.8Mo (UNS R56210) Typical U.S. government (military)

0.02 0.03

0.03 0.05

0.0125 0.0125

0.12 0.25

0.10 0.10

… 0.4 total

6 5.5–6.5

… …

… …

0.8 0.5–1.00

2Nb, 1Ta 1.5–2.50Nb, 0.5–1.5Ta

Ti-679 (UNS R54790) Typical AMS 4974 (bars, forgings) British TA.18, TA.19, TA.25, and TA.26

0.04 0.04 …

0.04 0.04 …

0.008 0.0125 0.0125

0.12 0.12 0.20

0.17 0.15 …

… (b), 0.005Y …

1 0.8–1.2 0.8–1.2

…

…

0.015

0.20

…

…

2.0–2.5

0.2Si, nom 0.15–0.27Si 0.1–0.5Si, 78.08 Ti min Same as TA.27

… 0.03 … … … …

… 0.05 … … … …

… 0.0125 … … … …

… 0.15 … … … …

… 0.13 … … … …

… … … … … …

6 5 6 6 5.5 5.5

2 5 2 … 3.5 4.5

4 2 1.5 5 3 4

2 2 1 0.5 0.25 0.5

…

…

0.02

0.07

…

6

2.75

4

0.4

British TA.20, TA.27 Other near-α alloys Ti-6242S(c)(e) Ti-5Al-5Sn-2Zr-2Mo(f) Ti-6Al-2Sn-1.5Zr-1Mo IMI 685 IMI 829 IMI 834 Ti-1100

Impurity limits not available 0.015 0.30 0.12

…

2.25 (nom) 11 5 2.0–2.5 10.5–11.5 4.0–6.0 2.0–2.5 10.5–11.5 4.0–6.0 10.5–11.5 4.0–6.0

0.8–1.2

0.08Si 0.25Si 0.35Bi, 0.1Si 0.25Si 1Nb, 0.3Si 0.7Nb, 0.4Si, 0.06C 0.45Si

(a) Unless a range is specified, values are nominal quantities. (b) 0.1 max each and 0.4 max total. (c) Depending on heat treatment, these alloys may be considered either near-alpha or alpha-beta and are also listed in Table 3.3(b) for alpha-beta alloys. (d) 0.1 max each and 0.3 max total. (e) In the United States, alloy Ti-6242S is typically classified as a superalpha or near-alpha alloy, although it is closer to being an alpha-beta alloy with its typical heat treatment. (f) Semicommercial alloy with a UNS designation of R54560

20 / Titanium: A Technical Guide formed at high temperatures and transformed to alpha or martensitic variants when cooled is often referred to as transformed beta. While this is a good generalization of the microstructural changes occurring, it does not do justice to the actual microstructure of alphabeta systems. Heat Treatment of Alpha-Beta Alloys. Solution treating usually is done at a temperature high in the two-phase alpha-beta field and is followed by quenching in water, oil, or another soluble quenchant. As a result of quenching, the beta phase present at the solution-treating temperature may be retained or may be partly transformed during cooling by either martensitic transformation or nucleation and growth (conventional diffusion-controlled phase formation) reactions. The specific response depends on alloy composition, solution-treating temperature (beta-phase composition at the solution temperature), cooling rate, and/or section size. Solution treatment is followed by aging,

Table 3.3(b)

normally at 480 to 650 °C (900–1200 °F), to precipitate alpha phase and produce a fine mixture of alpha and beta in the retained or transformed beta phase. Transformation kinetics, transformation products, and specific response of a given alloy can be quite complex; a detailed review of the subject is beyond the scope of this book. Chapters 4, 7, and 9 contain additional discussions of the transformations and microstructures in titanium, as affected by wrought alloy deformation processing and heat treatment. Also refer to the discussion of microstructural development in titanium alloys, which follows. Response to solution treating and aging depends on section size; alloys relatively low in beta stabilizers (e.g., Ti-6A1-4V) have poor hardenability and must be quenched rapidly to achieve significant strengthening. It has been shown that proper solution treating and aging can increase the strength of alpha-beta alloys by 30 to 50%, or more, over the annealed or

over-aged condition. Adequate cooling rates are often difficult to achieve unless section sizes are small. For Ti-6A1-4V, the cooling rate of a water quench is not rapid enough to significantly harden sections thicker than about 25 mm (1 in.). Hardenability increases as the content of beta stabilizers increases. Ti-5Al-2Sn-2Zr-4Mo-4Cr, for example, can be through-hardened with relatively uniform response throughout sections up to 150 mm (6 in.) thick. For some alloys with intermediate content of beta stabilizers, the surface of a relatively thick section can be strengthened, but the core may be as much as 10 to 20% lower in hardness and strength. It must be remembered that the strength that can be achieved by heat treatment is also a function of the volume fraction of beta phase present at the solution-treating temperature. In view of the cooling rate requirements, alloy composition, solution temperature, and aging conditions must be carefully selected and balanced to pro-

Compositions of various alpha-beta titanium alloys Impurity limits, wt% max Alloying elements, wt%(a)

Max others, Product specification(s)

N

C

H

Fe

O

each or total

Al

Sn

Zr

Mo

Others

0.05 0.05

0.10 0.08

(b) 0.01

0.3 0.3

0.2 0.2

… 0.4 total

6 5.5–6.75

… …

… …

… …

4 3.5–4.5V

0.05

0.08

0.012

0.3

0.2

0.4 total

5.5–6.75

…

…

…

3.5–4.5V

Ti-6Al-4V (UNS R56400) Typical Alloy Ti-P63 in AECMA standard prEN2530 for bars Alloy Ti-P63 in AECMA standard prEN2517 for sheet, strip, plate DIN 17851 (alloy WL3.7165) AMS 4905 (plate) AMS 4906 (sheet, strip) AMS 4911 (plate, sheet, strip) AMS 4920, 4928, 4934, and 4967 (rings, forgings, wires) AMS 4954 (wire) ASTM B 265 (plate, sheet)

0.05 0.03 0.05 0.05 0.05

0.08 0.05 0.08 0.08 0.10

0.015 0.0125 0.0125 0.015 0.0125

0.3 0.25 0.30 0.30 0.30

0.2 0.12 0.20 0.20 0.20

… (c), 0.005Y 0.4 total (c), 0.005Y (c), 0.005Y

5.5–6.75 5.6–6.3 5.5–6.75 5.5–6.75 5.5–6.75

… … … … …

… … … … …

… … … … …

3.5–4.5V 3.6–4.4V 3.5–4.5V 3.5–4.5V 3.5–4.5V

0.03 0.05

0.05 0.10

0.015 0.015

0.30 0.40

0.18 0.20

(c), 0.005Y (c)

5.5–6.75 5.5–6.75

… …

… …

… …

ASTM F 467 (nuts) and F 468 (bolts)

0.05

0.10

0.0125

0.40

0.20

(c)

5.5–6.75

…

…

…

3.5–4.5V 3.5–4.5V, 0.12–0.25Pd 3.5–4.5V

Ti-6Al-4V-ELI (UNS R56401) AMS 4907 and 4930 AMS 4996 (billet) ASTM F 135 (bar) ASTM F 467 (nuts) and F 468 (bolts)

0.05 0.04 0.05 0.05

0.08 0.10 0.08 0.10

0.0125 0.0125 0.0125 0.0125

0.25 0.30 0.25 0.40

0.13 0.13–0.19 0.13 0.20

(c), 0.005Y (d) … …

5.5–6.75 5.5–6.75 5.5–6.75 5.5–6.75

… 0.1 max … …

… 0.1 max … …

… 0.1 max … …

3.5–4.5V 3.5–4.5V 3.5–4.5V 3.5–4.5V

Ti-6Al-6V-2Sn (UNS R56620) Typical AMS 4918, 4936, 4971, 4978

0.04 0.04

0.05 0.05

0.015 0.015

0.35 –1.0 0.35 –1.0

0.20 0.20

… (c), 0.005Y

6 5.0–6.0

2 1.5–2.5

… …

… …

AMS 4979 (bars, forgings)

0.04

0.05

0.015

0.35 –1.0

0.20

(c)

5.0–6.0

1.5–2.5

…

…

0.75Cu, 6V 0.35–1.00Cu, 5.0–6.0V 0.35–1.00Cu, 5.0–6.0V

Other alpha-beta alloys UNS 56080 (in AMS 4908) UNS 56740 (in AMS 4970) Ti-6246 (UNS R56260) Ti-17 (see also Table 3.3c) Ti-6Al-2Sn-2Zr-2Cr-2Mo

0.05 0.05 0.04 0.04 0.03

0.08 0.10 0.04 0.05 0.05

0.015 0.013 0.0125 0.0125 0.0125

0.50 0.30 0.15 0.30 0.25

0.20 0.20 0.15 0.13 0.14

… … … … …

… 7 6 5 5.25–6.25

… … 2 2 1.75–2.25

… … 4 2 1.75–2.25

… 4 6 4 1.75–2.25

IMI-551 Ti-3Al-2.5V (in AMS 4943) IMI 550 IMI 679 IMI 700 Ti-8Al-1Mo-1V(e) Ti-6242(e) Ti-6242S(e)

… 0.02 … … … 0.05 0.05 …

… 0.05 … … … 0.08 0.05 …

… 0.015 … … … 0.015 0.0125(f) …

… 0.30 … … … 0.30 0.25 …

… 0.12 … … … 0.12 0.15 …

… … … … … … 0.3 total …

4 2.5–3.5 4 2 6 8 5.5–6.5 6

4 … 2 11 … … 1.8–2.2 2

… … … 4 5 … 3.6–4.4 4

4 … 4 1 4 1 1.8–2.2 2

8.0Mn … … 4.0Cr 0.20–0.27Si, 1.75–2.25Cr 0.5Si 2.0–3.0V … 0.25Si 1Cu, 0.2Si 1V … 0.08Si

(a) Unless a range is specified, values are nominal quantities. (b) Typical hydrogen limits of 0.0150H (sheet), 0.0125H (bar), and 0.0100H (billet). (c) 0.1 max each, 0.4 max total (d) 0.1 max Cu, 0.1 max Mn, 0.001Y, total others 0.20 max. (e) These alloys are considered either a near-alpha or an alpha-beta alloy (see Table 3.3a). (f) 0.0100 max H for bar and billet and 0.0150 max H for sheet and forgings

Understanding the Metallurgy of Titanium / 21 cold formed more readily than high-strength alpha-beta or alpha alloys. Beta alloys are actually metastable alloys; cold work at ambient temperature or heating to a slightly elevated temperature can cause partial transformation to alpha as the alloy reverts to the equilibrium condition. That metastability is exploited to produce exceptional structures from beta alloys. The principal advantages of beta alloys are that they have high hardenability, excellent forgeability, and good cold formability in the solution-treated condition, and can be hardened to fairly high strength levels. Because beta phase is invariably metastable and has a long-term tendency to transform to the equilibrium alpha-plus-beta structure, titanium producers use this tendency (to a point) by aging metastable beta alloys after solution treatment and fabrication. Temperatures of 450 to 650 °C (850–l200 °F) are used to partially transform the metastable beta phase to alpha. The alpha forms as finely dispersed particles in the retained beta, and room-temperature strength levels comparable or sometimes superior to those of aged alpha-beta alloys can be attained. In the solution-treated condition (100% retained beta), beta alloys have good ductility and toughness, relatively low strength, and excellent formability. Solution-treated beta alloys begin to precipitate alpha phase at slightly elevated temperatures and thus are unsuitable for elevated-temperature service without prior stabilization or over-aging treatment. Beta alloys do have some disadvantages compared to alpha-beta alloys. The beta alloys usually have higher density, lower creep

duce the desired mechanical properties in the final product. Precipitation Hardening of Superalpha and Alpha-Beta Alloys. Precipitation hardening (dispersion hardening by phases dispersed in the matrix, generally on a submicroscopic scale) to increase creep resistance of titanium alloys was a significant goal of early titanium development programs. Although the ability of alpha-beta alloys to be precipitation hardened in ways similar to nickel superalloys and aluminum was studied in laboratory programs from the inception of the titanium industry, the results were not favorable. The most significant developments of precipitation-hardened titanium alloys came with the introduction of silicon to alpha-beta alloys to form a silicide precipitate that seems to promote dispersion hardening. One of the more important continued applications of creep-resistant alloys has been the use of Ti-6Al-2Sn-4Zr-2Mo-0.2Si. About 0.25% or more of silicon can produce sharply enhanced creep resistance, probably by a dispersion-hardening reaction that creates particle barriers to deformation. Metastable Beta Alloys. Beta alloys are characterized by high hardenability, with the metastable beta phase being completely retained on air cooling of thin sections or water quenching of thick sections. Alloys of the metastable beta systems are richer in beta stabilizers and leaner in alpha stabilizers than alpha-beta alloys (Fig. 3.1). A major factor in the application of beta alloys has been the excellent forgeability of alloys with cubic titanium lattice structures. In sheet form, beta alloys can be Table 3.3(c)

strength, and lower tensile ductility in the aged condition. However, although tensile ductility is lower, the fracture toughness of an aged beta alloy generally is higher than that of an aged alpha-beta alloy of comparable yield strength. Very high yield strengths—about 1172 MPa (170 ksi)—with excellent toughness (KIc = 40 ksi in.) have been claimed for the beta alloy Ti-10V-2Fe-3Al. In general, the class of beta alloys serves a great need for titanium components that can be fabricated for moderate-temperature applications.

Microstructural Development in Titanium Alloys Background. Titanium microstructure generation has been mentioned frequently in this chapter. It should be apparent that once a chemistry has been selected, microstructures in titanium alloys usually are developed by heat treatment or other processing (wrought/cast/powder metallurgy), which often uses heat and/or is followed by heat treatment. With the exception of CP titanium and alpha alloys, microstructural changes are invariably produced through transformation of some or all of the alpha phase to beta phase. The microstructure that results is a function of the way in which the subsequent changes in beta or in residual (primary) alpha occur. Microstructural change is limited to grain refinement and, possibly, to grain shape changes in CP titanium and all alpha alloys. Typical al-

Compositions of various beta titanium alloys Impurity limits, wt% max Alloying elements, wt%(a)

Max others, Designation

Ti-13V-11Cr-3Al (UNS 58010)

Specifications

N

C

H

Fe

O

each or total

Al

Sn

Zr

Mo

AMS 4917

0.05

0.05

0.025

0.35

0.17

(b)

2.5–3.5

…

…

…

Others

AMS 4959 (wire)

0.05

0.05

0.030

0.35

0.17

(b), 0.005Y

2.5–3.5

…

…

…

MIL-T-9046, MIL-R-81588 MIL-T-9047; MIL-F-83142 High-toughness grade

0.05

0.05

0.025

0.15–0.35

0.17

0.4 total

2.5–3.5

…

…

…

0.05

0.05

0.025

0.35

0.17

…

2.5–3.5

…

…

…

0.015

0.04

0.008

…

(c)

2.5–3.5

…

…

…

0.05

0.05

0.015

1.6–2.4

0.11 (max), 0.08 (nom) 0.16

0.4 total

2.6–3.4

…

…

7.5–8.5

7.5–8.5V

0.05

0.05

0.015

0.30

0.12

0.4 total

3.0–4.0

…

3.5–4.5

3.5–4.5

7.5–8.5V

12.5–14.5V, 10.0–12.0Cr 12.5–14.5V, 10.0–12.0Cr 12.5–14.5V, 10.0–12.0Cr 12.5–14.5V, 10.0–12.0Cr 12.5–14.5V, 10.0–12.0Cr

Ti-8Mo-8V-2Fe-3Al MIL-T-9046, (UNS R58820) MIL-T-9047, and MIL-F-83142 Beta C MIL-T-9046, (UNS R58640) MIL-T-9047, and MIL-F-83142 Beta III AMS: 4977, 4980; ASTM: B 348, B 265, B 337, and B 338 Ti-10V-2Fe-3Al Forging alloy Ti-15-3 Sheet alloy

0.05

0.10

0.020

0.35

0.18

0.4 total

…

0.05 0.03

0.05 0.03

0.015 0.015

1.6–2.5 0.30

0.13 0.13

(c) (c)

2.5–3.5 2.5–3.5

… 2.5–3.5

… …

… …

Ti-17(d) Transage 175

0.05 0.05

0.05 0.08

0.0125 0.015

0.25 0.20

0.08–0.13 0.15

(c) (b)(e)

4.5–5.5 2.2–3.2

1.6–2.4 6.5–7.5

1.6–2.4 1.5–2.5

3.5–4.5 …

9.25–10.75V 14–16V, 2.5–3.5Cr 3.5–4.5Cr 12.0–14.0V

0.05 …

0.08 …

0.015 …

0.20 …

0.15 …

(b)(e) …

2.0–3.0 2

1.5–2.5 2

5.5–6.5 11

… …

11.0–13.0V 11.5V

Transage 134 Transage 129

Engine compressor alloy High-strength, elevated-temperature High-strength alloy …

3.75–5.25 4.5–7.5 10.0–13.0

…

(a)Unless a range is specified, values are nominal quantities. (b) 0.1 max each, 0.4 max total. (c) 0.1 max each, 0.3 max total. (d) Alloy Ti-17 is an alpha rich near-beta alloy that might be classified as an alpha-beta alloy, depending on heat treatment. (e) 0.005 max Y and 0.03 max B

22 / Titanium: A Technical Guide pha-beta and beta alloy microstructural development is covered for two selected alloys in the following sections. Ti-6Al-4V Microstructure. Ti-6Al-4V is one of the most widely used titanium alloys. It is an alpha-beta type containing 6 wt% Al and 4 wt% V. Typical uses include aerospace applications, pressure vessels, aircraft gas turbine disks, cases and compressor blades, and surgical implants. Ti-6Al-4V has an excellent combination of strength and toughness along with excellent corrosion resistance. The properties of this alloy are developed by relying on the refinement of the grains upon cooling from the beta region, or the alpha-plusbeta region, and subsequent low-temperature aging to decompose martensite formed upon quenching. When this alloy is slowly cooled from the beta region, alpha begins to form below the beta transus, which is about 980 °C (1796 °F). The alpha forms in plates, with a crystallographic relationship to the beta in which it forms. The alpha plates form with their basal (close-packed) plane parallel to a special plane in the beta phase. Upon slow cooling, a nucleus of alpha forms, and because of the close atomic matching along this common plane, the alpha phase thickens relatively slowly perpendicular to this plane but grows faster along the plane. Thus, plates are developed. Because there are six sets of nonparallel growth planes in a given beta grain, a structure of alpha plates is formed consisting of six noparallel sets. The Widmanstätten microstructure developed is illustrated in Fig. 3.6. The formation process is shown schematically in Fig. 3.10. It uses a constant-composition phase diagram section at 6% Al to illustrate the formation of alpha upon cooling. The darker regions are the beta phase left between the alpha plates that have formed. The microstructure consists of parallel plates of alpha delineated by the beta phase between them. Where alpha plates formed parallel to one specific plane of beta meet alpha plates formed on another plane, a high-angle grain boundary exists between the alpha crystals and etches to reveal a line separating them. This microstructural morphology, consisting of these sets of parallel plates that have formed with a crystallographic relationship to the phase from which they formed, is called a Widmanstätten structure. Upon cooling rapidly, beta may decompose by a martensite reaction, similar to that for pure titanium, and form a Widmanstätten pattern. The structure present after quenching to 25 °C (77 °F) depends on the annealing temperature. Different types of martensite can form, depending on the alloy chemistry and the quenching temperature. These are designated alpha prime and alpha double prime. Upon quenching from above the beta transus (about 980 °C, or 1796 °F), the structure is all martensitic alpha prime or alpha double prime with a small amount of beta (although in some alloys the beta has not been observed). The presence of some beta in the structure after quenching from above the beta transus is

due to the fact that the temperature for the end of the martensite transformation, Mf, is below room temperature (25 °C, or 77 °F) for this al-

Fig. 3.9

loy. That is because vanadium is a beta stabilizer, and the addition of 4% V to a Ti-6%Al alloy is sufficient to place the Mf below 25 °C

Main characteristics of different titanium alloy family groupings

Microstructures achieved at various intermediate temperatures by slowly cooling from above the β transus. Final microstructure consists of plates of α (white) separated by the β phase (dark).

Fig. 3.10

Schematic of the development of a Widmanstätten structure in an alpha-beta alloy (Ti-6Al-4V)

Understanding the Metallurgy of Titanium / 23 (77 °F). Thus, upon quenching to 25 °C (77 °F), not all of the beta is converted to alpha prime or alpha double prime. For the commercial Ti-6Al-4V alloy, there are some commonly used heat treatments. For each of these, the following descriptions are typical of the temperatures and times used. The actual practice varies with alloy producer and user. Figure 3.11 shows some microstructures formed from Ti-6Al-4V alloy as a function of solution temperature and cooling rate.

To place the alloy in a soft, relatively machinable condition, the alloy is heated to about 730 °C (1346 °F) in the lower range of the alpha-plus-beta region, held for 4 hours, then furnace cooled to 25 °C (77 °F). This treatment, called mill annealing, produces a microstructure of globular crystals of beta in an alpha matrix. A typical microstructure is shown in Fig. 3.12. Another annealing treatment is duplex annealing. Several variants of this treatment are used. Typically, the alloy is heated to 955 °C (1751

Furnace cooled

Air cooled

Water quenched

(a)

(e)

(i)

(b)

(f)

(j)

(c)

(g)

(k)

(d)

(h)

(l)

Effect of cooling rate on the microstructure of an alph-beta alloy (Ti-6Al-4V). (a) α' + β; prior beta grain boundaries. (b) Primary α and α' + β. (c) Primary α and α' + β. (d) Primary α and metastable β. (e) Acicular α + β; prior beta grain boundaries. (f) Primary α and acicular α + β. (g) Primary α and acicular α + β. (h) Primary α and β. (i) Plate-like α + β; prior grain boundaries. (j) Equiaxed α and intergranular β. (k) Equiaxed α and intergranular β. (l) Equiaxed α and intergranular β. Etchant: 10 HF, 5 HNO3, 85 H2O. 250×

°F) for 10 minutes, then air cooled. It then is heated to 675 °C (1247 °F) for 4 hours and air cooled to 25 °C (77 °F). With the aging treatment called solution treating and aging, typically the alloy is heated at 955 °C (1751 °F) for 10 minutes, water quenched, then aged for 4 hours at a temperature between 540 and 675 °C (1004 and 1247 °F), followed by air cooling to 25 °C (77 °F). Typical tensile mechanical properties for the three treatments are compared in Table 3.4. The strongest alloy is the one that has been solution treated and aged. The mill-annealed condition is stronger than the duplex-annealed condition, but the difference is slight. Ti-13V-11Cr-3Al Microstructure. The second alloy to be considered is a beta alloy, Ti-13V-11Cr-3Al. This alloy is historically important as the first beta alloy to see significant use in an aircraft. Body-centered cubic alloy elements (vanadium and chromium have bcc crystal structures) used to stabilize the beta phase in titanium raise the possibility of the development of a eutectoid alloy reaction. Figure 3.13 shows the two basic types of phase diagrams for binary beta-stabilized titanium alloys. The horizontal line above the alpha-plus-gamma phase field in Fig. 3.13(b) is the eutectoid temperature, and the possible transformation of the beta phase directly to alpha-plus-gamma on cooling describes the eutectoid reaction. It might be supposed that in a system with a eutectoid reaction, rapid cooling from the beta region can lead to a martensite structure in the same way that steel martensites are formed. However, the martensite formed in quenching or rapid cooling of the beta structure is alpha prime, which is not particularly strong. Consequently, as determined for alpha-beta alloys, quenching may be necessary to achieve adequate property levels in thicker material sections, but strengths and hardness levels commensurate with the martensites of steels will not be achieved.

Fig. 3.11

Structure of mill-annealed alpha-beta alloy (Ti-6Al-4V). Structure is globular particles of β in a matrix of α. Optical micrograph. ~500×

Fig. 3.12

24 / Titanium: A Technical Guide Table 3.4 Ti-6Al-4V tensile mechanical properties(a) Yield strength Condition

Tensile strength

Elongation at ksi fracture, %

MPa

ksi

MPa

Mill annealed 945 Duplex annealed 917 Solution treated 1103 and aged

137 133 160

1069 155 965 140 1151 167

10 18 13

(a) At 25 °C (77 °F) in the milled-annealed, duplex-annealed, and solution-treated and aged conditions

Table 3.5 Effect of alloying elements in several titanium binary alloys on eutectoid temperature and composition, and content needed to retain beta Alloying element

Manganese Iron Chromium Cobalt Nickel Copper Silicon

Eutectoid temperature °C

°F

550 600 675 585 770 790 860

1022 1112 1247 1085 1418 1454 1580

Eutectoid composition, wt%

20 15 15 9 7 7 0.9

Alloy content, wt%(a)

6.5 4 8 7 8 13 …

(a) Needed to retain beta after quenching at 25 °C (77 °F)

Fig. 3.14

Fig 3.13

Phase diagram schematics for beta-stabilized alloys (a) beta isomorphous and (b) beta

eutectoid

Beta alloys tend to be used because of the relative formability of the bcc beta structure compared to the hcp alpha structure. Sufficient alloy content allows retention of a metastable beta structure after quenching from the beta region to 25 °C (77 °F) as indicated previously. In this condition the alloy can be fabricated by plastic deformation. Then the component can be reheated below the eutectoid temperature to decompose the retained beta to a multiphase structure of beta and other phases that depend on the exact alloy chemistry, providing considerable strengthening over that of the retained beta. This approach is the basis of a few commercial alloys, and in this discussion, the physical metallurgy of one of these, Ti-13V11Cr-3A1, is examined.

Time-temperature transformation diagram for a beta alloy (Ti-1 3V-11Cr-4Al). Alloy was initially solution treated in the β region for 2 h at 760 °C (1400 °F); then air cooled at 25 °C (77 °F ); then aged.

The addition of chromium should maintain the desirable corrosion- and oxidation-resistance characteristic of titanium alloys. Table 3.5 shows the effect of several elements on the eutectoid temperature and composition and the alloy content required to lower the Mf to 25 °C (77 °F). Note that chromium is relatively effective in retaining beta. Data for titanium-vanadium and titaniumchromium alloys show that beta can be retained upon quenching from the beta region. In the titanium-vanadium alloys, hardening occurs upon aging due to the formation of alpha in the beta and the appearance of the intermediate omega phase. In the titanium-chromium alloys, hardening is associated with the formation of alpha in the beta and also, the phase TiCr2 is subsequently formed. Thus, in the alloy of Ti-Cr-V, it could be expected that beta can be retained upon quenching from the beta region to 25 °C (77 °F), and that upon aging, hardening associated with the formation of alpha and TiCr2, and perhaps the intermediate omega phase, occurs. These two latter phases are metastable and disappear upon prolonged aging.

The recommended commercial heat treatment for Ti-13V-11Cr-4A1 is to solution heat treat in the beta region from about 760 to 815 °C (l400–1499 °F) for 0.2 to 1 hour, then air cool or quench (depending on the size of the part) to retain the beta structure. Subsequent aging to precipitate alpha phase is accomplished around 480 °C (896 °F) for a time usually between 2 and 100 hours, depending on the properties desired. The use of aging temperatures around 480 °C (896 °F) is based on data that show that this is the optimum range to use for maximum strength for aging times up to 100 hours. Below this temperature, the rate of formation of alpha is too low to give appreciable hardening. This is seen in the time-temperature transformation (TTT) diagram of Fig. 3.14, which describes the transformation products of beta breaking down isothermally to alpha and other phases. At aging (isothermal holding) temperatures above 480 °C (896 °F), the beta phase transforms too rapidly and the resultant structure is too coarse to attain maximum strengthening.

Titanium: A Technical Guide Matthew J. Donachie, Jr., p25-32 DOI:10.1361/tatg2000p025

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 4

Ingot Metallurgy and Mill Products General Aspects THE MANUFACTURE OF TITANIUM ALLOYS consists of a number of separate steps. Of these steps, the following represent the transfer of titanium from an ore to an ingot ready for either wrought or cast processing or to mill products:

• Production of titanium sponge (reduction of • • •

titanium ore to an impure porous form of titanium metal) Purification of the sponge Melting of the sponge or the sponge plus alloy elements or a master alloy to form an ingot Primary fabrication, in which ingots are converted into general mill products, such as bar, plate, sheet, strip, or wire

An overview of the major aspects of a variety of operations performed on titanium, through mill products and final wrought forms, is shown in Fig. 4.1 (cast final processing and joining processes are not included in this figure). Casting of components is covered in Chapter 6, and joining is discussed in Chapter 9. The primary process for creating “raw” titanium is the Kroll process. In this process, magnesium is reacted with titanium tetrachloride. The resultant elemental titanium produced is then leached free of the magnesium chloride compound leaving a spongy residue behind. Hence, the name sponge titanium. Matthew Hunter was the first to develop a process to produce elemental titanium with the use of sodium to react with the titanium tetrachloride compound. The Hunter process was successfully used by some producers for many years, but the Kroll process eventually became dominant. The purity of the titanium produced is a function of the purity of the starting materials. Control of raw materials is extremely important in producing titanium and its alloys because there are many elements of which even small amounts can produce major, and at times undesirable, effects on the properties of these metals in finished form.

In order to produce ingots of titanium or titanium alloys for commercial application, titanium from sponge is commonly alloyed with pure forms of other elements, master melt of titanium plus alloy elements, and/or reclaimed titanium scrap (usually called “revert”). Titanium Sponge. Titanium is extracted from ores, such as rutile, where the form of titanium is as an oxide. Titanium dioxide is reacted with coke and chlorine to produce titanium tetrachloride. The subsequent reaction with magnesium produces magnesium chloride plus a spongy titanium mass, and it occurs usually in an iron retort. Processing is proprietary to each titanium company, but the sponge is machined from the iron retort and then leached to remove the impurities. Purification of the removed sponge mass was done with acid leaching for many years, but now vacuum distilling (with possible inert gas sweep) is widely used to produce a pure titanium by more completely removing the magnesium chloride byproduct. Vacuum distilling results in lower residual levels of magnesium, hydrogen, and chlorine than does acid leaching, but vacuum distilling causes a cost increase. Figure 4.2 shows typical titanium sponge. The removed and purified titanium is sold as titanium sponge. Purity of sponge varies with source ores and titanium extraction processes; in fact, for many years, some worldwide sponge sources were thought to produce purer sponge than others. Purity also can be affected by the location of the sponge relative to the iron retort. The principal impurities in sponge are nitrogen, oxygen, silicon, carbon, and iron. Although some differences may exist between sponge from different producers, modern melting techniques effectively remove volatile substances from sponge and control the purity of the sponge so that ingot of high quality can be produced regardless of which method is used for sponge production as long as the sponge is of high quality with regard to inclusion particles. Problems with titanium ingots and subsequent products can stem from the sponge production process. Consequently, titanium sponge

must meet stringent specifications relative not only to chemistry but also to inclusions and surface contamination of the sponge. It is most important that sponge does not contain hard, brittle, and refractory titanium oxide, titanium nitride, or complex titanium oxynitride particles. These particles, if retained through subsequent melting operations, could act as crack initiation sites in the final product. Although carbon, nitrogen, oxygen, silicon, and iron commonly are permitted as residual elements in sponge, these elements must be held to acceptably low levels because they affect the properties of the finished product. For example, carbon, nitrogen, and oxygen raise strength and lower ductility. (See Fig. 4.3 and Chapter 12.) In order to meet normal requirements for chemical and physical purity of sponge, sponge has been crushed after leaching or vacuum distillation and passed along a conveyor belt where inspectors remove discolored particles or other obvious nonconforming particles. When highest purity sponge is required, past practice often has dictated the use of sponge from the center of the retort rather than the wall. Clearly, practices such as this lead to higher costs for higher-quality material. Alloying Elements. Purity of the alloying elements added to titanium during melting is as important as the purity of sponge at an earlier stage. Alloy purity must be controlled with the same degree of care used in establishing sponge purity to avoid undesirable residual elements—especially those that can form refractory or high-density inclusions in the titanium matrix. The strength levels of commercially pure (CP) titanium (ASTM and ASME grades 1 through 4) basically are controlled by oxygen and iron contents. Differences in mechanical properties between extra-low-interstitial (ELI) grades and standard grades of titanium alloys also are effected by the oxygen levels (Table 4.1). In higher-strength CP titanium grades, oxygen and iron are intentionally added to the residual amounts already in the sponge to provide extra strength. On the other hand, carbon and nitrogen usually are held to minimum residual levels to avoid embrittlement.

26 / Titanium: A Technical Guide

Fig. 4.1

Overview of the production cycle for ingot and mill products

Ingot Metallurgy and Mill Products / 27 Reclaimed Scrap (Revert). The addition of scrap makes production of ingot titanium more economical than if only sponge were used. If properly controlled, addition of scrap is fully acceptable, and it can be used even in materials for critical structural applications, such as rotating components for jet engines. All forms of scrap can be remelted—machining chips, cut sheet, trim stock, and chunks. To be used properly, scrap must be thoroughly cleaned and carefully sorted by alloy and by purity before being remelted. During cleaning, surface scale must be removed because adding titanium scale to the melt could produce refractory inclusions or excessive porosity in the ingot. Machining chips from fabricators who use carbide tools are acceptable for remelting only if all carbide particles adhering to the chips are removed—otherwise, hard, high-density inclusions could result. Improper segregation of alloy revert produces off-composition alloys and could potentially degrade the properties of the resulting metal. Although uncommon, defects in titanium alloys have resulted in the failure of aircraft gas turbine engines. The safety record for titanium alloys is very good, but some component failures have had disastrous consequences. Most of the failures were traced to defects derived from

the sponge production process or to revert material that was inadequately inspected. As a result of one failure on a commercial aircraft at the end of the 1980s, there was concern that revert should be limited to noncritical titanium alloy applications. However, titanium turnings were exempt from concern because the FAA reported that “chips or machine turnings…if properly processed can be used to produce premium grade ingot.”

Titanium Ingot Production Vacuum arc remelting (VAR) has been the principal method for the production of titanium ingots since commercial introduction of titanium alloys occurred in the 1950s. VAR is a process used for high-performance alloys to control the melting and solidification of environment-sensitive alloys. A schematic of a VAR furnace is shown in Fig. 4.4. A cylindrical electrode of appropriate chemistry is melted by an arc in a vacuum and solidified in a water-cooled crucible. The process is capable of high melt rates with titanium, but steady-state solidification is not possible, and the molten metal pool is relatively deep. VAR has many advantages including high purity, good control, and reproducibility in the

product. However, the process is operated in a vertical position, which can cause gravity-induced segregation. Owing to the unique solidification conditions for titanium in VAR processing, high-density components of an electrode, if they fall into the melt as solids, can survive in the melt by rapidly dropping to the bottom of the molten pool and solidifying before they can be melted and homogenized in the solidifying ingot. An alternate to VAR, cold-hearth melting, has been developed and is discussed later in this chapter. Electrodes for making titanium ingots are compacted aggregates (“compact” or “briquettes”) of sponge and alloy elements, including both master melt and elemental materials. For commercially pure titanium, the sponge is compacted and the electrode is melted with appropriate oxygen control. When alloys are to be produced, granules of titanium sponge are mixed and then blended with appropriate alloy-containing material. The resultant “alloy” mixture is pressed into a compact or briquette. A number of compacts can be welded together to form a 4.5 m (15 ft) long electrode, which is lowered into a VAR furnace for melting. Alternatively, carefully selected titanium revert can be welded to form the electrode. Welding was done with a gas-tungsten arc in the early years of commercial titanium application, but tungsten contamination caused

Table 4.1 How oxygen and iron contents change the properties of titanium alloys (annealed sheet) Maximum impurity content, % Material

Unalloyed Ti, Grade 1 Unalloyed Ti, Grade 2 Unalloyed Ti, Grade 3 Unalloyed Ti, Grade 4 Ti-6Al-4V Ti-6Al-4V-ELI Ti-5Al-2.5 Sn Ti-5Al-2.5 Sn-ELI

Fig. 4.2

Titanium sponge

Minimum tensile strength

Minimum yield strength(a)

Oxygen

Iron

MPa

ksi

MPa

ksi

0.18 0.25 0.35 0.40 0.20 0.13 0.20 0.12

0.20 0.30 0.30 0.50 0.30 0.25 0.50 0.25

240 345 450 655 925 900 830 690

35 50 65 95 134 130 120 100

170 275 380 485 870 830 780 655

25 40 55 70 126 120 113 95

(a) At 0.2% offset

Drive motor Drive screw

Vacuum Crucible Electrode Water guide Electrode gap Ingot pool

Furnace body

Solidified ingot

Water out

Water in

Fig. 4.3

Effects of interstitial content on strength and ductility of unalloyed titanium

Fig. 4.4

Schematic of a vacuum arc remelting furnace

28 / Titanium: A Technical Guide metal-inert gas welding to be favored. Figure 4.5 shows some of the stages in the production of a titanium alloy ingot. Traditional Melting Practice. Most titanium and titanium alloy ingot is melted twice using the VAR process. The procedure is known as the double consumable-electrode vacuum-arc remelting process. Double melting is considered necessary for all applications to ensure an acceptable degree of homogeneity in the resulting product. For certain critical applications, a third, or “triple,” melting step was specified at times, especially after the middle of the 1960s when defects were found in rotor-grade titanium alloys produced by double melting. Triple melting achieves even better uniformity of chemistry and structure. Triple melting also reduces oxygen-rich or nitrogen-rich inclusions in the microstructure to a very low level by providing an additional melting operation to dissolve them. In the two-stage process, titanium sponge, revert, and alloy additions are initially mechanically consolidated (as described previously) and then are melted together to form an ingot. Ingots from the first melt are used as the consumable electrodes for second-stage melting. Ingots from the second melt are used as the consumable electrodes for third-stage melting when it is done. Processes other than consumable-electrode arc melting may be permitted in some instances for first-stage melting of ingot for noncritical applications. Usually, all melting is done under vacuum, but in any event, the final stage of melting for noncritical applications must be done by the consumable-electrode vacuum-arc process. While VAR has been required in the past for all melting stages of material destined for critical applications, improved melting technology using cold-hearth techniques is permitted for some applications. Modifying Microstructure and Macrostructure. The nature of the VAR process with titanium alloys makes it difficult to improve ingot homogeneity by modifying melt practice. Thus, although segregation and other compositional variations directly affect the final properties of mill products, melting technique alone does not account for all segregation and compositional variations and so has not been correlated with final properties. Melting in a vacuum reduces the hydrogen content of titanium and essentially removes other volatiles. This tends to result in high purity in the cast ingot. However, anomalous operating factors, such as air leaks, water leaks, arc-outs, or even large variations in power level affect both soundness and homogeneity of the final product. Ingot size is a factor in structure refinement. Normally, ingots are 650 to 900 mm (26–36 in.) in diameter and weigh 3600 to 6800 kg (8,000–15,000 lb). Larger ingots are economically advantageous to use and are important in obtaining refined macrostructures and microstructures in very large sections, such as billets with diameters of 400 mm (16 in.) or greater. Ingots up to 1000 mm (40 in.) in diameter and

weighing more than 9000 kg (20,000 lb) have been melted successfully, but due to increasing tendency for segregation with increasing ingot size, there appear to be limitations on the improvements that can be achieved by producing large ingots. The use of newer melting technologies may make larger ingot sizes possible. Newer Melting Technology. The 1990s saw the culmination of significant efforts devoted to the development of improved titanium melting technology relative to reduction of im-

purities and improvements in structure. Electron-beam and plasma-arc melting technologies are now available for the melting of titanium alloys or the remelting of scrap. The use of these technologies permits the cold-hearth melting (CHM) of titanium alloys. A conceptual illustration of hearth melting and refining technology is given in Fig. 4.6. Studies on electron-beam cold-hearth melting (EBCHM) and plasma-arc melting (PAM) have demonstrated the ability of hearth melting to remove

(a)

(b)

(c)

(d)

(e) Titanium ingot production. (a) Granules. Courtesy of Oregon Metallurgical Corp. (b) Compacts. Courtesy of IMI Titanium, Ltd. (c) Lowering electrode into furnace. Courtesy of IMI Titanium Ltd. (d) Final ingot. Courtesy of IMI Titanium, Ltd. (e) Welding revert. Courtesy of Howmet Turbine Components Corp.

Fig. 4.5

Ingot Metallurgy and Mill Products / 29 high-density inclusions (HDI) with great confidence. Low-density inclusions (LDI) are also addressed by CHM. Many LDI are alpha-stabilized areas of titanium. (Defects in titanium are discussed further later in this chapter.) Depending on size, shape, and chemistry, LDI can be heavier or lighter than titanium. Some LDI can be removed by gravity settling in CHM just as HDI are removed. However, most LDI will not settle out. The controlled time and temperature in the refining zone of the hearth (a process that is difficult to accomplish in VAR furnaces) is thought to contribute to the improved dissolution of any LDI present. In addition to the reduced incidence of HDI, and in conjunction with the dissolution of some LDI, CHM processes produce much lower levels of gaseous impurities and an improved structure. Although PAM was thought to be a lower-cost alternative to EBCHM, both processes continue to be applied. EBCHM units and PAM units were made operational at divisions of the major titanium producers during the latter part of the 1990s. Other techniques for melting titanium alloys have been considered. Electroslag melting, induction slag melting, induction skull melting, and other processes have all been evaluated as techniques that might produce improved properties for the most demanding titanium applications. One significant advantage of the cold-hearth melting techniques, in addition to structure and chemistry control, is the possibility of producing shaped ingot cross sections other than cylindrical ingots. Slab sections have been cast, and slab shapes should find their way into at least some limited applications in the future. Defects in titanium ingots have been a concern in titanium ingot metallurgy production since the early days of the industry. Different types of defects were recognized, most stemming from sponge handling, electrode preparation, and melt practice. The principal

Fig. 4.6

characterization of these defects was as low-density inclusions and high-density inclusions. Over two dozen different defects have been cataloged. Defects prompted strict process controls that were agreed upon by metal suppliers and customers alike. These controls have done much to attain either reduced-defect or defect-free materials. Despite the controls, occasional defects have been involved in significant events related to titanium alloy failures. It is predicted that the introduction of cold-hearth technologies will further reduce the incidence of defects in titanium ingots. VAR has been the traditional melting method of choice for titanium ingot production. There are portions of every VAR melt that are transient by nature. The startup and the hot-top are two such places, and solidification defects are most probable in these locations. Because of the problems with startup, titanium ingots are greatly affected by a temporary shutdown of the arc during VAR melting. Every producer has a proprietary aspect to titanium melting processes. All producers using VAR, however, are required by most purchasers of titanium ingots to report any unusual aspects of a given VAR run. A prime source of defects in alloys is segregation. Segregation in titanium ingot must be controlled because it leads to several different types of imperfections that cannot be readily eliminated by homogenizing heat treatments or combinations of heat treatment and primary mill processing. LDI are usually called type I imperfections. These are regions of interstitially stabilized alpha phase that have substantially higher hardness and lower ductility than the surrounding material. These regions also exhibit a higher beta transus temperature. They arise from very high nitrogen or oxygen concentrations in sponge, master alloy, or revert. Type I imperfections frequently, but not always, are associ-

TIMET’s larger hearth furnaces have dual chambers. Two such units, located at the Morgantown, PA facility, have a combined refining capacity of 40 million lb per year. Courtesy of Titanium Metals Corp. (TIMET)

ated with voids or cracks (Fig. 4.7a and b). Although type I imperfections sometimes are referred to as LDI, they often are of higher density than is normal for the alloy but are not as dense as the HDI that are associated with refractory metals such as tungsten. The nitrogen-stabilized LDI represent the most serious type of defect because the high hardness, low ductility, and possible voids or cracks dramatically reduce fatigue properties. Cold-hearth melting has been shown to reduce the rate of LDI occurrence. The reduction takes place by dissolution, which is effected by the higher superheat possible in cold-hearth melting compared to VAR. Type II imperfections, sometimes called high-aluminum defects, are abnormally stabilized alpha-phase areas that can extend across several beta grains (Fig. 4.7c). Type II imperfections are caused by segregation of metallic alpha stabilizers, such as aluminum. They contain an excessively high proportion of primary alpha having a microhardness only slightly higher than that of the adjacent matrix. Type II imperfections sometimes are accompanied by adjacent stringers of beta—areas low in both aluminum content and hardness. This condition, shown in Fig. 4.7(d), is generally found in the hot-top area of an ingot. It is associated with closed-solidification pipe into which alloy constituents of high vapor pressure migrate, only to be incorporated into the microstructure during primary mill fabrication. Stringers normally occur in the top portions of ingots and can be detected on surfaces by macroetching or blue-etch anodizing. Material containing stringers usually must undergo metallographic review to ensure that the indications revealed by etching are not artifacts. The hot-top procedure at the end of the VAR cycle can be adjusted somewhat to minimize the void and, thus, minimize type II defect formation. This defect also has been minimized by cold-hearth melting practices using plasma-arc melting. (EBCHM is not so effective because the high vacuum tends to promote high-vapor-pressure element migration.) Beta flecks, another type of imperfection, are small regions of stabilized beta in material that has been alpha-beta processed and heat treated. In size, they are equal to, or greater than, prior beta grains (Fig. 4.7e). Beta flecks are regions in the final product that are usually rich in beta-stabilizing elements, such as chromium, iron, and vanadium. Beta flecks are either devoid of primary alpha or contain less than some specified minimum level of primary alpha. They are caused by the presence of a localized region either abnormally high in beta-stabilizer content or abnormally low in alpha-stabilizer content. Beta flecks are attributed to microsegregation during solidification of ingots. Beta flecks appear in alloys that contain beta stabilizers (such as iron or chromium) that are strongly rejected by the freezing interface in the ingot. They are most often found in products made from large-diameter ingots. Beta flecks have been found in alloys such as

30 / Titanium: A Technical Guide Ti-6Al-4V or Ti-17 (Ti-5Al-2Sn-2Zr-4Cr-4Mo) and other alloys containing iron or chromium. Beta fleck may be sharply reduced or eliminated in cold-hearth melting methods owing to improvements in composition control resulting from the relatively shallow ingot molten pool depths and corresponding rapid solidification rates. Type I and type II imperfections are not acceptable in aircraft-grade titanium because they degrade critical design properties. Beta flecks are not considered harmful in alloys lean in beta stabilizers if they are to be used in the annealed condition. On the other hand, they constitute regions that incompletely respond to

heat treatment; for this reason, microstructural standards (allowable limits on beta flecks in various alpha-beta alloys) have been established. Beta flecks are more objectionable in beta-rich alpha-beta alloys than in leaner alloys.

• Melting process used to make ingot • Method for mechanically working ingots into mill products

• Fabrication or heat treatment, the final step employed in working

Primary Fabrication General Aspects. At each of the following steps, mechanical and physical properties of titanium in the finished shape can be affected by any of several factors, or by a combination of

(a)

(b)

(c)

(d)

(e) Representative microstructural defects in titanium alloys. (a) Type I alpha segregation; large voids surrounded by stabilized alpha. (b) Type I alpha segregation; small voids surrounded by stabilized alpha. (c) Type II alpha segregation as revealed by an etch-anodized technique. (d) Beta segregation, at times associated with Type II alpha segregation. (e) Beta flecks. (a) through (d) reprinted from AMS 2380, courtesy of SAE, Inc.

Fig. 4.7

factors, among the most important of which are:

Because the properties of titanium are so readily influenced by processing, great care must be exercised in controlling the conditions under which the processing is carried out. At the same time, this characteristic of titanium makes it possible for the titanium industry to serve a wide range of applications with a minimum number of grades or alloys. By varying thermal or mechanical processing, or both, a broad range of special properties can be produced in commercially pure titanium and titanium alloys. The conversion of ingot into general mill products—billet, bar, plate, sheet, strip, extrusions, tube, and wire—is what we define as primary fabrication. Forging, casting, powder metallurgy, and joining techniques used to produce a finished product are secondary fabrication. Mill products can readily be used in secondary manufacture of parts and structures (Fig. 4.1). Primary fabrication is very important in establishing final properties because many secondary fabrication operations have little or no effect on metallurgical characteristics. Some secondary fabrication processes, such as forging, ring rolling, and superplastic forging, do impart sufficient reduction to play a major role in establishing material properties. Reduction to Billet. Generally, the first breakdown of production ingot is a press cogging operation done in the beta temperature range. However, working in the alpha region below the beta transus is essential to produce billets with refined structures. Billet reduction processes are carried out at temperatures high in the alpha region to allow greater reduction and improved grain refinement with a minimum amount of surface rupturing. Where maximum fracture toughness is required, beta processing (or alpha-beta processing followed by beta heat treatment) generally is preferred. Table 4.2 gives standard temperature ranges for forging for the manufacture of billet stock. Some billets intended for further forging, rolling, or extrusion go through a grain-refinement process. This technique uses the characteristic of titanium that causes it to recrystallize when it is heated above the beta transus. By starting with grain-refined billet, secondary fabricators may be able to produce forgings that meet strict requirements with respect to macrostructure, microstructure, and mechanical properties without extensive hot working below the beta transus. Final tensile properties of alpha-beta alloys are strongly influenced by the amount of processing in the alpha-beta field—both below the beta transus temperature and after recrystallization. Such processing increases the

Ingot Metallurgy and Mill Products / 31 Table 4.2

Standard forging temperatures for some titanium grades and alloys Forging temperature Beta transus

Alloy

CP Ti Grades 1 to 4

Ingot breakdown

Intermediate

Finish

°C

°F

°C

°F

°C

°F

°C

°F

900–955

1650–1750

955–980

1750–1800

900–925

1650–1700

815–900

1500–1650

Alpha or near-alpha alloys Ti-5Al-2.5Sn Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-8Al-1Mo-1V

1030 995 1040

1890 1820 1900

1120–1175 1095–1150 1120–1175

2050–2150 2000–2100 2050–2150

1065–1095 1010–1065 1065–1095

1950–2000 1850–1950 1950–2000

1010–1040 955–980 1010–1040

1850–1900 1750–1800 1850–1900

Alpha-beta alloys Ti-8Mn Ti-6Al-4V Ti-6Al-6V-2Sn Ti-7Al-4Mo

800 995 945 1005

1475 1820 1735 1840

925–980 1095–1150 1040–1095 1120–1175

1700–1800 2000–2100 1900–2000 2050–2150

845–900 980–1040 955–1010 1010–1065

1550–1650 1800–1900 1750–1850 1850–1950

815–845 925–980 870–940 955–980

1500–1550 1700–1800 1600–1725 1750–1800

Beta alloy Ti-13V-11Cr-3Al

720

1325

1120–1175

2050–2150

1010–1065

1325

925–980

1700–1800

strength of high-alpha grades in large section sizes. With modern processing techniques, billet and forged sections readily meet specified tensile properties prior to final forging. Table 4.3 shows how billet and forging section size affect room-temperature tensile properties of various titanium alloys. Bar, Plate, Sheet, Strip, Wire, and Tubing. Roll cogging and hot roll finishing of bar, plate, sheet, and strip are standard operations for most titanium alloys. Wire also is produced, as is seamless tubing. Initially, primary fabrication equipment was the same as that used in the specialty steel industry; however, special rolling and auxiliary equipment was

eventually installed where necessary to allow closer control of all fabrication operations. Processes used by each manufacturer are proprietary and, in some respects, unique. Because all techniques must produce the same specified structures and mechanical properties, a high degree of similarity exists among the processes of all manufacturers. A representative range of temperatures used for hot rolling of titanium metals is presented in Table 4.4. Rolling at these temperatures produces end products with the desired grain structures. Extrusion is used as an alternative to rolling as a mill process in order to make rod-like

Table 4.3 Variations with thickness of typical tensile properties at room temperature for several titanium alloys Section size(a)

Tensile strength

Yield strength

in.

MPa

ksi

MPa

ksi

Elongation(b), %

Reduction in area, %

6Al-4V(c) 25–50 102 205 330

1–2 4 8 13

1015 1000 965 930

147 145 140 135

965 930 895 860

140 135 130 125

14 12 11 10

36 25 23 20

6Al-4V-ELI(c) 25–50 102 205 330

1–2 4 8 13

950 885 885 870

138 128 128 126

885 827 820 795

128 120 119 115

14 12 10 10

36 28 27 22

6Al-6V-2Sn(c) 25–50 102 205

1–2 4 8

1105 1070 1000

160 155 145

1035 965 930

150 145 135

15 13 12

40 35 25

1–2(d) 4(e) 8(f)

985 910 1000

143 132 145

905 840 895

131 122 130

15 17 12

36 35 23

6Al-2Sn-4Zr-2Mo + Si(g) 25–50 1–2 102 4 205 8 330 13

1000 1000 1035 1000

145 145 150 145

930 930 940 825

135 135 136 120

14 12 12 11

33 30 28 21

mm

8Al-1Mo-1V 25–50 102 205

(a) Properties are in longitudinal direction for sections 50 mm (2 in.) or less, and in transverse direction for sections 100 mm (4 in.) or more, in section size. (b) In 50 mm or 2 in. (c) Annealed 2 h at 700 °C (1300 °F) and air cooled. (d) Annealed 1 h at 900 °C (1650 °F), air cooled, then heated 8 h at 600 °C (1100 °F) and air cooled. (e) Annealed 1 h at 1010 °C (1850 °F), air cooled, then heated to 566 °C (1050 °F). (f) Annealed 1 h at 1010 °C (1850 °F) and oil quenched. (g) Annealed 1 h at 954 °C (1750 °F), air cooled, then heated 8 h to 600 °C (1100 °F) and air cooled

products, tube, and other shaped linear mill products. Extrusion also may be used to produce final design components. Properties of extrusions are affected by processing conditions in much the same way as they are for rolled or forged products. The properties of extruded products, however, are not identical to those of die-forged structures. Even where similar microstructures are produced, the thermomechanical working possible in open-die and closed-die forging permits much more control over the resultant properties. One of the more unusual applications of extrusion in secondary fabrication (component shape making) has been in the production of tapered wing spars for a military aircraft. The Role of Surface in Titanium Processing. Although titanium is melted under vacuum, badly oxidized surfaces can form on ingots during melting. Surface scale must be brushed off or, in extreme cases, machined off an ingot prior to remelting. Heavy oxide layers can form as a result of hot working unless hot working is done in inert atmospheres. Sufficient metal must be available on mill products so as to reach proper dimensions when this scale is removed. A most significant aspect of titanium alloy production (e.g., mill products and secondary fabrication by forging) is the need to consider the pickup of interstitial nitrogen and oxygen at the surface. Surface removal invariably is needed to eliminate the alpha case that forms during fabrication of titanium alloy mill products. After any necessary scale removal, further mechanical or chemical treatment is needed to remove the alpha case to avoid cracking during subsequent working operations or during service if the mill product is made into a component. Properties of Mill Products. Bars up to about 100 mm (4 in.) in diameter are unidirectionally rolled, and their properties commonly reflect total reduction in the alpha-beta range. For example, a round bar 50 mm (2 in.) in diameter rolled from a Ti-6Al-4V billet 100 mm (4 in.) square typically is 140 to 170 MPa (20–25 ksi) lower in tensile strength

32 / Titanium: A Technical Guide than rod 7.8 mm (5 16 in.) in diameter rolled on a rod mill from a billet of the same size at the same rolling temperatures. For bars approximately 50 to l00 mm (2–4 in.) in diameter, strength does not decrease with section size, but transverse ductility and notched stressrupture strength at room temperature do become lower. In diameters greater than about 75 to 100 mm (3–4 in.), annealed Ti-6Al-4V bars usually do not meet prescribed limits for stress rupture at room temperature—1170 MPa (170 ksi) min to cause rupture of a notched specimen in 5 hours—unless the material is given a special duplex anneal. Transverse ductility is lower in bars approximately 65 to 100 mm (2 1 2 –4 in.) in diameter because it is not possible to obtain the preferred texture throughout bars of this size. Plate and sheet can exhibit the same tensile properties in both the transverse and longitudinal directions relative to the final rolling direction. With the precise control systems (or types of titanium) now available, texturing and directionality can be obtained in alpha-beta sheet by unidirectional rolling. These characteristics favorably affect tensile properties of Ti-6Al-4V sheet in various gages (Table 4.5). Other properties, such as fatigue resistance, also are improved by this type of rolling. Directionality in properties generally is observed only as a slight drop in transverse ductility of plate greater than 25 mm (1 in.) thick. Military Specifications (MIL), Aerospace Material Specifications (AMS), and customer specifications all prescribe lower minimum tensile and yield strengths as plate thickness increases. For forming applications, some customers specify a maximum allowable difference between tensile strengths in the transverse and longitudinal directions. Microstructural control is essential to the optimization of properties in titanium alloys. Con-

trol of forging reductions and work imparted to ingots and finished products has long marked the successful use of titanium forged Table 4.4

components. Mill products can now be provided with improved properties and product uniformity.

Typical rolling temperatures for several titanium grades and alloys Rolling temperatures Bar

Alloy

CP Ti Grades 1 to 4

Plate

Sheet

°C

°F

°C

°F

°C

°F

760–815

1400–1500

760–790

1400–1450

705–760

1300–1400

Alpha or near-alpha alloys Ti-5Al-2.5Sn 1010–1065 Ti-6Al-2Sn-4Zr-2Mo 955–1010 Ti-8Al-1Mo-1V 1010–1040

1850–1950 1750–1850 1850–1900

980–1040 955–980 980–1040

1800–1900 1750–1800 1800–1900

980–1010 925–980 980–1040

1800–1850 1700–1800 1800–1900

Alpha-beta alloys Ti-8Mn Ti-4Al-3Mo-1V Ti-6Al-4V Ti-6Al-6V-2Sn Ti-7Al-4Mo

… 925–955 955–1010 900–955 955–1010

… 1700–1750 1750–1850 1650–1750 1750–1850

705–760 900–925 925–980 870–925 925–955

1300–1400 1650–1700 1700–1800 1600–1700 1700–1750

705–760 900–925 900–925 870–900 925–955

1300–1400 1650–1700 1650–1700 1600–1650 1700–1750

Beta alloy Ti-13V-11Cr-3Al

955–1065

1750–1950

980–1040

1800–1900

730–900

1350–1650

Table 4.5

Room-temperature tensile properties of unidirectionally rolled Ti-6Al-4V sheet

Gage

Tensile strength

Yield strength

Elongation,

Tensile modulus

MPa

ksi

MPa

ksi

%(a)

GPa

106 psi

Longitudinal direction 0.737 0.029 1.016 0.040 1.168 0.046 1.524 0.060 1.778 0.070

945 970 915 985 995

137 141 133 143 144

870 855 860 925 915

126 124 125 134 133

7.0 6.5 6.5 6.5 8.0

100 106 105 104 105

14.5 15.4 15.2 15.1 15.3

Transverse direction 0.737 0.029 1.016 0.040 1.168 0.046 1.524 0.060 1.778 0.070

1105 1195 1225 1125 1095

160 173 178 163 159

1061 1105 1165 1090 1055

154 160 169 158 153

7.5 7.5 7.5 8.0 9.5

130 145 140 125 135

18.8 21.1 20.2 18.2 19.5

mm

(a) In 50 mm (2 in.)

in.

Titanium: A Technical Guide Matthew J. Donachie, Jr., p33-38 DOI:10.1361/tatg2000p033

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 5

Forging and Forming MANUFACTURING PROCESSES such as die forging, hot and cold forming, machining, chemical milling, joining, and, sometimes, extrusion are all secondary fabrication processes used for producing finished parts from mill products. Each of these processes may strongly influence properties of titanium and titanium alloys, either alone or by interacting with effects of processes to which the metal has previously been subjected. Machining, joining, and chemical milling are covered in later chapters; extrusion is covered in Chapter 4, while this chapter is devoted to forging and forming of titanium and titanium alloys. Forging is the primary way in which shape and structure control are achieved in titanium alloy components. Forming is the primary way in which shapes derived from plate or sheet are prepared.

Forging General Aspects. Titanium alloy forgings are produced by all the forging methods currently available. These methods include opendie, closed-die, rotary forging, and others. Selection of the optimal forging method is based on the shape desired for the forged component as well as its desired mechanical properties and microstructure (which largely determine properties after alloy composition is set). Sequential forging operations may be required to achieve desired results. For example, blocker-type forging may be used to set the stage for the final conventional closed-die forging of a component. One of the main purposes of forging, in addition to shape control, is to obtain a combination of mechanical properties that generally do not exist in bar or billet. Tensile strength, creep resistance, fatigue strength, and toughness all may be better in forgings than in bar or other forms. Titanium alloys are forged into a variety of wrought shapes for many applications, particularly in the aerospace field; this forging is ac-

complished largely by use of dies. Titanium alloys are difficult to forge but less so than refractory metals and superalloys. The working history and forging parameters used in titanium alloy forging have a great impact on the microstructure and properties of the finished component. Consequently, forging sequences and subsequent heat treatment can be used to control the microstructure and resulting properties of the product. In the manufacture of titanium alloy forgings, the predominant forms of forging stock used are billet and bar that have been fabricated by primary hot-working processes. Only rarely is titanium alloy ingot directly forged into finished titanium alloy forging components. Even then, early forging stages are used to refine the ingot structure. Requirements for the forging stock are usually the subject of specifications set by the forger or are negotiated with the metal supplier and ultimate forging customer. Surface preparation of titanium alloy billet or bar forging stock is important. Proper preparation is necessary not only for the satisfactory performance of the stock in subsequent forging, but also because detailed, stringent nondestructive testing is frequently performed on the forging stock as a critical part of the overall quality assurance functions on titanium alloy forgings. Temperature exposure is critical to titanium forging characteristics as well as to microstructure and resultant mechanical property development. It is also good practice to limit the exposure of titanium alloys to high temperatures to prevent the formation of excessive scale and minimize the formation of alpha case owing to interactions with the interstitial elements oxygen and nitrogen. For any given titanium alloy, the pressure requirements for forging vary over a large range, which is dependent on: the actual alloy composition, the forging process in use, plus the temperature, strain rate, and other factors of the forging operation. Figure 5.1 gives an illustration of the flow-stress differences for CP titanium and several alloys. Note the significantly higher stress required for basic deformation of titanium and its alloys compared with steel.

Forging pressure requirements are related to flow stress and, in accordance with the customary flow-stress behavior of metals, vary with temperature (Fig. 5.2). Die Forging. Open-die forging is used to produce some shapes in titanium when volume and/or size do not warrant the development of closed dies for a particular application. However, closed-die forging is used to produce the greatest amount of forged titanium alloys. Closed-die forging can be classified as blocker type (single die set), conventional (two or more die sets), or high definition (two or more die sets). Precision die forging also is conducted, usually employing hot-die/isothermal forging techniques. Conventional closed-die titanium forgings cost more than the blocker type, but the increase in cost is justified because of reduced machining costs and better property control. The dies used in titanium forging are heated to facilitate the forging process and to reduce surface chilling and metal temperature losses, which can lead to inadequate die filling and/or excessive surface cracking of the forged component. Hot-die/isothermal forging takes the die temperature to higher levels. Forging is more than just a shape-making process. The key to successful forging and heat treatment is the beta transus temperature. Fundamentally, there are two principal approaches to the forging of titanium alloys:

• Forging the alloy predominantly below the beta transus

• Forging the alloy predominantly above the beta transus

There are possible variations on these approaches to achieve desired properties in commercial alloys. In fully stabilized beta alloys, manipulation of the alpha phase by varying forging parameters is not an issue. Fully stabilized beta alloys are typically forged above the beta transus of the alloy. Alpha, near-alpha, and alpha-beta alloys are often modified by forging (and heat treatment) variations. Conventional alpha-beta forging is best described as a forging process in which all or most of the deformation is conducted below the

34 / Titanium: A Technical Guide

Fig. 5.1

Flow stress of some common titanium alloys compared with a steel (AISI 4340)

beta transus. Both alpha and beta phases will be present in the microstructure at all times. The relative amounts of each phase present during the forging process are a function of forge temperature distance from the beta transus. Structures resulting from alpha-beta forging are characterized by deformed or equiaxed primary alpha phase (alpha present during the forging process) and transformed beta phase. Figure 5.3 shows schematically the possible locations for die forging temperature and/or heat treatment temperatures of a typical alpha-beta alloy such as Ti-6Al-4V. The higher the processing temperature in the alpha + beta region, the more beta will be available to transform on cooling. On quenching from above the beta transus, a completely transformed, acicular structure arises. The exact form of the globular (equiaxed) alpha and the transformed beta structures produced by processing depends on

the exact location of the beta transus, which varies from heat to heat of a given alloy and also on the degree and nature of deformation produced, as well as the cooling rate from forging. The actual forging temperatures used are based on experience and desired microstructures. Table 5.1 lists recommended metal temperatures for a number of commonly forged alpha, alpha-beta, and beta titanium alloys. As a general guide, metal temperatures of beta transus minus 28 °C (50 °F) for alpha/beta forgings and beta transus plus 42 °C (75 °F) are recommended. Superplastic isothermal die forging may be accomplished at temperatures that differ from these recommendations. Beta forging is a forging technique in which the deformation of the alloy is done above the

1093

2000 Beta region

1038

1800

Transformed beta

Alpha + beta region

10% Alpha

982

60% Alpha 1700

90% Alpha

927

Alpha region 1600

871

1500

816

1400 0 2 Ti + 6 wt % Al

4

6

8

Temperature, °C

Temperature, °F

1900

760 10

Vanadium, wt%

Fig. 5.2 4340)

Effect of forging temperature on forging pressure for some titanium alloys and steel (AISI

Fig. 5.3

Phase diagram used to predict results of forging or heat treatment practice

beta transus. In commercial practice, beta forging actually involves initial deformation above the beta transus, but final finishing with controlled amounts of deformation below the beta transus of the alloy. In beta forging, the influences of mechanical working (deformation) are not necessarily cumulative because of the high temperature and the formation of new grains by recrystallization each time the beta transus is surpassed on reheating for forging. Beta forging, particularly of alpha and alpha-beta alloys, results in significant reductions in forging pressures and reduced cracking tendency of the billet during forging. On the other hand, nonuniform working, excessive grain growth and/or poorly worked structures resulting in widely variant mechanical properties can result from improperly executed beta forging. Section size is important in die forging, and the number of working operations can be significant. Conventional die forging may require two or three operations, whereas isothermal forging may require only one. A schematic representation of a conventional forging and subsequent heat treatment sequence is shown in Fig. 5.4. The solution heat treatment offers a chance to modify, or tune, the as-forged microstructure, while the aging cycle modifies the transformed beta structures to an optimum dispersion. Undesirable structures (grain-boundary alpha, beta fleck, “spaghetti”—elongated alpha) can interfere with optimum property development. Consequently, microstructural control is basic to successful processing of titanium alloys. Titanium ingot structures can carry over to affect the forged product. Beta processing, de-

Forging and Forming / 35 spite its adverse effects on some mechanical properties, can reduce forging costs, while isothermal forging offers a means of reducing forging pressures and/or improving die fill and part detail. Isothermal beta forging is used in the production of more creep-resistant components of titanium alloys. Some alloys developed in the latter decades of the twentieth century are intended to be beta forged to develop their desired final mechanical properties (Chapter 12 provides additional discussion of the effects of beta forging on properties). Reheating of alpha-beta titanium alloys after hot working can substantially alter the microstructure. Careful attention must be paid to the development of microstructure right through the heat treatment steps. Superficially similar microstructures may not produce the same levels of mechanical properties. Solution heat treatment and aging of nonworked or insufficiently worked structures will not produce optimum strengths or toughness in titanium alloys. The effects of different thermomechanical processing schedules on the mechanical properties and the corresponding structures of alphabeta titanium alloys such as Ti-6Al-4V, Ti-6Al-6V-2Sn, and Ti-6Al-2Sn-4Zr-6Mo may be used to illustrate the effects of processing schedules on properties. Table 5.2 summarizes four thermomechanical schedules that produced optimum combinations of properties in test forgings of the alpha-beta alloy, Ti-6Al-4V: excellent tensile strength, good-to-excellent notch fatigue strength, low-cycle fatigue strength, and fracture toughness. Also included in the table are three schedules that produced subnormal properties. The microstructures of Ti-6Al-4V shown in Fig. 5.5 correspond to two of the schedules that produced good combinations of properties and two that produced inferior combinations. Note the substantial difference in microstructure in the same final product, which, in combination with the resulting properties, demonstrates that control of thermomechanical processing can control the microstructures and corresponding final properties of forgings. Figure 5.6 summarizes the results of an extensive study of alpha-beta forging versus beta forging for several titanium alloys. Although yield strength after beta forging was not always as high as that after alpha-beta forging, values

Schematic of a conventional die forging and subsequent heat treatment to produce an alphabeta structure

Fig. 5.4

Table 5.1

Recommended forging temperature ranges for commonly forged titanium alloys βt

Alloy

Forging temperature(b)

°C

°F

Process(a)

°C

°F

α/near-α alloys Ti-CP(c) Ti-5Al-2.5Sn(c) Ti-5Al-6Sn-2Zr-1Mo-0.1Si Ti-6Al-2Nb-1Ta-0.8Mo

915 1050 1010 1015

1675 1925 1850 1860

Ti-6Al-2Sn-4Zr-2Mo(+0.2Si)(d)

990

1815

Ti-8Al-1Mo-1V IMI 685 (Ti-6Al-5Zr-0.5Mo-0.25Si)(e) IMI 829 (Ti-5.5Al-3.5Sn-3Zr-1Nb-0.25Mo-0.3Si)(e) IMI 834 (Ti-5.5Al-4.5Sn-4Zr-0.7Nb-0.5Mo-0.4Si-0.06C)(e)

1040 1030 1015 1010

1900 1885 1860 1850

C C C C B C B C C/B C/B C/B

815–900 900–1010 900–995 940–1050 1040–1120 900–975 1010–1065 900–1020 980–1050 980–1050 980–1050

1500–1650 1650–1850 1650–1925 1725–1825 1900–2050 1650–1790 1850–1950 1650–1870 1795–1925 1795–1925 1795–1925

α-β alloys Ti-6Al-4V(c)

995

1825

Ti-6Al-4V ELI(f)

975

1790

Ti-6Al-6V-2Sn Ti-6Al-2Sn-4Zr-6Mo

945 940

1735 1720

Ti-6Al-2Sn-2Zr-2Mo-2Cr Ti-17 (Ti-5Al-2Sn-2Zr-4Cr-4Mo(g)

980 885

1795 1625

Corona 5 (Ti-4.5Al-5Mo-1.5Cr)

925

1700

IMI 550 (Ti-4Al-4Mo-2Sn) IMI 679 (Ti-2Al-11Sn-4Zr-1Mo-0.25Si) IMI 700 (Ti-6Al-5Zr-4Mo-1Cu-0.2Si)

990 945 1015

1810 1730 1860

C B C B C C B C C B C B C C C

900–980 1010–1065 870–950 990–1045 845–915 845–915 955–1010 870–955 805–865 900–970 845–915 955–1010 900–970 870–925 800–900

1650–1800 1850–1950 1600–1740 1815–1915 1550–1675 1550–1675 1750–1850 1600–1750 1480–1590 1650–1775 1550–1675 1750–1850 1650–1775 1600–1700 1470–1650

β/near-β/metastable β alloys Ti-8Al-8V-2Fe-3Al Ti-10V-2Fe-3Al

775 805

1425 1480

Ti-13V-11Cr-3Al Ti-15V-3Cr-3Al-3Sn Beta C (Ti-3Al-8V-6Cr-4Mo-4Zr) Beta III (Ti-4.5Sn-6Zr-11.5Mo) Transage 129 (Ti-2Al-11.5V-2Sn-11Zr) Transage 175 (Ti-2.7Al-13V-7Sn-2Zr)

675 770 795 745 720 760

1250 1415 1460 1375 1325 1410

C/B C B C/B C/B C/B C/B C/B C/B

705–980 705–785 815–870 650–955 705–925 705–980 705–955 650–870 705–925

1300–1800 1300–1450 1500–1600 1200–1750 1300–1700 1300–1800 1300–1750 1200–1600 1300–1700

(a) C, conventional forging processes in which most or all of the forging work is accomplished below the βt of the alloy for the purposes of desired mechanical property development. This forging method is also referred to as α-β forging. B, β forging processes in which some or all of the forging is conducted above the βt of the alloy to improve hot workability or to obtain desired mechanical property combinations. C/B, either forging methodology (conventional or β) is employed in the fabrication of forgings or for alloys, such as β alloys, that are predominately forged above their βt but may be finish forged at subtransus temperatures. (b) These are recommended metal temperature ranges for conventional α-β, or β forging processes for alloys for which the latter techniques are reported to have been employed. The lower limit of the forging temperature range is established for open-die forging operations in which reheating is recommended. (c) Alloys for which there are several compositional variations (primarily oxygen or other interstitial element contents) that may affect both βt and forging temperature ranges. (d) This alloy is forged and used both with and without the silicon addition; however, the βt and recommended forging temperatures are essentially the same. (e) Alloys designed to be predominantly β forged. (f) ELI, extra-low interstitial. (g) Ti-17 has been classified as an α-β and as a near-β titanium alloy. For purposes of this table, it is classified as an α-β alloy.

Table 5.2 Thermomechanical schedules for producing various property combinations in an alpha-beta titanium alloy (Ti-6Al-4V) Initial microstructure

Blocker forging Finish forging Finish temperature temperature forging range range reduction

Cooling after forging

Heat treated condition

Best combinations of properties … Alpha-beta

Alpha-beta

…

Air cooled

Annealed

Grain-boundary alpha

Alpha-beta

Alpha-beta

…

Air cooled

Annealed

Grain-boundary alpha

Alpha-beta

Alpha-beta

…

…

Beta

Alpha-beta

10%

Air cooled

Annealed

Subnormal properties Spaghetti alpha

Alpha

Alpha

…

Air cooled

STOA(a)

…

Beta

Alpha-beta

10%

Water quenched

STOA

…

Beta

Beta

…

Slow cooled

Annealed

(a) STOA, solution treated, overaged

Water quenched Annealed

Final microstructure

6% equiaxed alpha plus fine platelet alpha 26% elongated partly broken up grain-boundary primary alpha plus fine platelet alpha 23% elongated partly broken up primary alpha plus very fine platelet alpha 63% fine elongated primary alpha plus fine platelet alpha 25% blocky primary alpha plates plus very fine platelet alpha 43% coarse elongated primary alpha plates plus very fine platelet alpha 92% alpha basket-weave structure

36 / Titanium: A Technical Guide of notch tensile strength and fracture toughness were consistently higher for the beta-forged material. The beta-forged alloys tend to show a transformed beta or acicular microstructure, whereas alpha-beta-forged alloys show a more equiaxed structure. This latter structure generally is as shown in Fig. 5.5(a). Tradeoffs are required for each structural type (acicular versus equiaxed) since each structure has unique capabilities. Table 5.3 shows the relative advantages of equiaxed and acicular microstructures. Precision Die Forging. A titanium die forging alternative procedure involves the use of precision isothermal (sometimes superplastic) forging techniques. Precision forging produces a product form that requires much less machin-

(a)

(c)

ing to achieve final dimensions of the component. Precision-forged titanium is a significant factor in titanium usage in the aircraft and gas turbine engine fields. Most precision-forged titanium is produced as near-net shape (NNS) product, meaning that the forging is close to final dimensions but that some machining is required. Isothermal forging is a process in which the material being forged is held at essentially constant temperature conditions and, thus, does not undergo the thermal fluctuations of heat up and cool down, which are experienced several times in a conventional forging sequence. Identical forging presses to those for conventional-die forging may be used, although there may also be a press dedicated to isothermal

(b)

(d)

Microstructures corresponding to various combinations of properties resulting from forging an alpha-beta titanium alloy (Ti-6Al-4V). (a) 6% equiaxed primary alpha plus fine platelet alpha in Ti-6Al-4V alpha-beta forged, then annealed 2 h at 705 °C (1300 °F) and air cooled. (b) 23% elongated, partly broken-up primary alpha plus grain-boundary alpha in Ti-6Al-4V, alpha-beta forged and water quenched, then annealed 2 h at 705 °C and air cooled. (c) 25% blocky (spaghetti) alpha plates plus very fine platelet alpha in Ti-6Al-4V alpha-beta forged from a spaghetti-alpha starting structure, then solution treated 1 h at 955 °C (1750 °F) and reannealed 2 h at 705 °C. (d) 92% alpha basket-weave structure in Ti-6Al-4V beta forged and slow cooled, then annealed 2 h at 705 °C

Fig. 5.5

forging. There is, however, a difference in the dies used. Die block materials have been a significant concern in the development of the isothermal forging processes. Isothermal forging can be performed in the alpha-beta or the beta phase field. Microstructures can be controlled quite accurately. Thus, property uniformity should be better than that achieved by means of conventional forging. The advent of more readily forgeable beta and metastable beta alloys (such as Ti-10V-2Fe-3Al) helped to make isothermal NNS precision forging of titanium alloys a common procedure, for suitable alloys but at a premium cost, of course. The NNS concept has been the motivational basis of the isothermal forging process. This implies, of course, a desire to minimize the amount of costly machining that must be done to produce the finished component. It also implies a desire not to absorb costs of materials that will only be scrapped as chips. Although alpha-beta alloy isothermal forging is feasible, high process and tooling costs, catastrophic die failures, and other engineering problems associated with very high process temperatures combined to minimize its use on conventional alpha-beta alloys. Selected alpha-beta alloys such as Ti-6Al-4V and Ti-6Al-6V-2Sn are fabricated to NNS configurations. Although, initially, isothermal forging was applied to billet material, the technology has been applied to P/M ingot or to preforms. (A preform is a P/M consolidation that has a shape designed to be somewhat like the final shape to maximize die-filling capability in the forging process and to minimize pressures and excess material. Chapter 7 contains more details.)

Forming General Aspects. Titanium is more difficult to form than are steel or aluminum alloys, and titanium alloys generally have less-predictable forming characteristics than steel or aluminum alloys. However, as long as certain limitations on titanium alloys are recognized, and established guidelines for hot and cold forming are followed, titanium and titanium alloys can be successfully formed into complex parts. Titanium and titanium alloys can be formed in standard machines to tolerances similar to those obtained in the forming of stainless steel. Since titanium metals exhibit a high degree of springback in cold forming, titanium must be extensively overformed or, as is done most frequently, hot sized after cold forming. However, to reduce the effect of springback variation on accuracy and to gain the advantage of increased ductility, the majority of formed titanium parts is made by hot forming or by cold preforming and then hot sizing as just mentioned. Beta alloys generally are easier to form than are alpha and alpha-beta alloys. Much attention has been paid to the potential for the use of beta sheet alloys such as Ti-15V-3Sn-3Cr-3Al in the past decade.

Forging and Forming / 37 Table 5.3 Relative advantages of equiaxed and acicular titanium alloy microstructures Equiaxed Higher ductility and formability Higher threshold stress for hot salt stress corrosion Higher strength (for equivalent heat treatment) Better hydrogen tolerance Better low-cycle fatigue (initiation) properties Acicular Superior creep properties Higher fracture-toughness values

Fig. 5.6

titanium alloys, formability is best at low forming speeds. To improve accuracy, cold forming is generally followed by hot sizing. Hot sizing and stress relief are ordinarily needed to reduce stress and to avoid delayed cracking and stress corrosion. Stress relief is also needed to restore compressive yield stress. Hot sizing often is combined with stress relief. Stress-relief treatments for CP titanium and some titanium alloys are given in Table 5.4. Additional information is contained in Chapter 8. Heating titanium alloys increases formability, reduces springback, takes advantage of a lesser variation in yield strength, and allows for maximum deformation with minimum annealing between forming operations. Severe forming must be done in hot dies, generally with preheated stock. The greatest improvement in the ductility and uniformity of properties for most titanium alloys is at temperatures above 540 °C (1000 °F).

Comparison of mechanical properties achieved in near-alpha-, alpha-beta-, and beta-forged titanium alloys

Hot and Cold Forming. Titanium and titanium alloy sheet and plate are strain hardened by cold forming. This normally increases tensile and yield strengths and causes a slight drop in ductility. Hot forming does not greatly affect final properties. Forming at temperatures from 595 to 815 °C (1100 to 1500 °F) allows the material to deform more readily, and simultaneously, it stress relieves the deformed material and also minimizes the degree of springback. Titanium metals tend to creep at elevated temperatures; holding under load at the forming temperature (creep forming) is another alternative for achieving the desired shape without having to compensate for extensive springback. In all forming operations, titanium and titanium alloys are susceptible to the Bauschinger effect. This phenomenon is a drop in compressive yield strength in one loading direction accompanied by an increase in tensile strength in another direction due to strain hardening. The Bauschinger effect is most pronounced at room temperature; plastic deformation (1 to 5% tensile elongation) at room temperature always introduces a significant loss in compressive yield strength, regardless of the initial heat treatment or strength of the alloys. At 2% tensile strain, for instance, the compressive yield strengths of Ti-4Al-3Mo-1V and Ti-6Al-4V drop to less than half the values for solution-treated material. Increasing the temperature reduces the Bauschinger effect; subsequent full thermal stress relieving completely removes it. Temperatures as low as the aging temperature remove most of the Bauschinger effect in solutiontreated titanium alloys. Heating or plastic deformation at temperatures above the normal aging temperature for solution-treated Ti-6Al-4V causes overaging to occur, and as a result, all mechanical properties decrease.

Commercially pure titanium and the most ductile titanium alloys (such as Ti-15V-3Sn3Cr-3Al and Ti-3Al-8V-6Cr-4Zr-4Mo) can be formed cold to a limited extent. The superalpha alloy Ti-8Al-1Mo-1V can be cold formed to shallow shapes by standard methods. The cold forming of other alloys generally results in excessive springback and requires stress relieving between operations. For the cold forming of all Table 5.4

Selected stress-relief treatments for titanium and some titanium alloys(a) Temperature

Alloy

°C

°F

Time, h

480–595

900–1100

1 –4 4

Ti-5Al-2.5Sn

540–650

1000–1200

Ti-8Al-1Mo-1V

595 –705

1100–1300

Ti-6Al-2Sn-4Zr-2Mo

595–705

1100–1300

Ti-6Al-2Cb-1Ta-0.8Mo

595–650

1100–1200

Ti-0.3Mo-0.8Ni (Ti Code 12)

480–595

900–1100

1 –4 4 1 –4 4 1 –4 4 1 –2 4 1 –4 4

Ti-6Al-4V

480–650

900–1200

1–4

Ti-6Al-6V-2Sn (Cu + Fe)

480–650

900–1200

1–4

Ti-3Al-2.5V

540–650

1000–1200

Ti-6Al-2Sn-4Zr-6Mo

595–705

1100–1300

1 –2 2 1 –4 4

Ti-5Al-2Sn-4Mo-2Zr-4Cr (Ti-17)

480–650

900–1200

1–4

Ti-7Al-4Mo

480–705

900–1300

1–8

Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.25Si

480–650

900–1200

1–4

Ti-8Mn

480–595

900–1100

1 –2 4

Ti-13V-11Cr-3Al

705–730

1300–1350

1

Ti-11.5Mo-6Zr-4.5Sn (Beta III)

720–730

1325–1350

1

Ti-3Al-8V-6Cr-4Zr-4Mo (Beta C)

705–760

1300–1400

Ti-10V-2Fe-3Al

675–705

1250–1300

Ti-15V-3Al-3Cr-3Sn

790–815

1450–1500

Commercially pure Ti (all grades) Alpha or near-alpha titanium alloys

Alpha-beta titanium alloys

Beta or near-beta titanium alloys

(a) Parts can be cooled from stress relief by either air cooling or slow cooling.

–1 4 –1 12 4 1 –1 6 2 1 –2 2 1 –1 12 4 12

38 / Titanium: A Technical Guide Table 5.5 Temperatures for hot forming of titanium and some titanium alloys Forming temperature Alloy

°C

°F

CP titanium (all grades)

480 – 705

900 – 1300

α and near-α alloys Ti-8Al-1V-1Mo Ti-5Al-2.5Sn

790 ± 15 620 – 815

1450 ± 25 1150 – 1500

α-β alloys Ti-6Al-6V-2Sn

790 ± 15

1450 ± 25

β alloy Ti-13V-11Cr-3Al

605 – 790

1125 – 1450

At still higher temperatures, some alloys exhibit a phenomenon known as superplasticity. Superplastic behavior has become widely used in the forming and bonding of titanium. Above approximately 650 °C (1200 °F), it is recommended that forming be done in a protective atmosphere to minimize oxidation. Table 5.5 lists some temperatures for the hot forming of titanium and selected titanium alloys. As can be seen, most hot-forming operations are done at temperatures above 540 °C (1000 °F). For applications in which the maximum ductility is required, temperatures below 315 to 425 °C (600 to 800 °F) are usually avoided. While temperatures generally must be kept below 815 °C (1500 °F) to avoid marked deterioration in mechanical properties, superplastic forming is performed at 870 to 925 °C (1600 to 1700 °F) for some alpha-beta alloys such as Ti-6Al-4V. Care must be taken not to exceed the beta transus, or properties will be affected. Owing to the possibility of scaling and embrittlement in hot forming of titanium alloys at temperatures in excess of 540 °C (1000 °F),

time at elevated temperature should be limited. Generally, for heating in air, 1 h is the longest time permitted at 705 °C (1300 °F), and 20 min is all that is permitted at 870 °C (1600 °F). Argon gas is frequently used as an atmosphere for superplastic forming where temperatures are at the high end of the permitted range. Aging in Forming. Some hot-forming temperatures are high enough to age a titanium alloy. Heat treatable beta and alpha-beta alloys generally must be re-heat treated after hot forming. Alpha-beta alloys should not be formed above the beta transus temperature. Because of aging, scaling, and embrittlement, as well as the greater cost of forming at high temperatures, hot forming normally is done at the lowest possible temperature that will permit the desired deformation. Superplastic Forming. Superplastic forming of titanium currently is widely used in the aircraft industry and, to a lesser extent, in the gas turbine industry. Advantages of superplastic forming are, among others:

• Very complex parts can be formed. • Lighter, more efficient structures can be designed and formed.

• It is performed in a single operation. • More than one piece may be produced in a machine cycle.

• Pressure (force) is uniformly applied to all areas of the workpiece.

Superplastic forming is not without limitations, including:

• Expensive equipment • Long preheat times • Use of protective atmosphere

• Need for heat-resistant die materials with minimum nickel content. (Nickel in trace amounts has been implicated in loss of high temperature properties in titanium alloys.) The workhorse superplastic titanium alloy is the alpha-beta alloy Ti-6Al-4V. The art of superplastic forming of titanium is largely the result of work on this alloy, although many alloys exhibit superplastic behavior. Metallurgical variables that affect superplastic behavior in titanium alloys include grain size, grain size distribution, diffusion characteristics of the base and alloy atoms, ratio of alpha to beta phase amounts, and the texture of the alloy to be superplastically formed. Alloy composition has a very significant effect on superplastic behavior in titanium alloys. Superplastic forming has been combined with diffusion bonding to produce a versatile process that eliminates the need for welding and brazing of complex parts (more details can be found in Chapter 9). Deep Drawing and Other Forming Processes. The deep drawing of titanium alloys largely has been replaced by superplastic forming. Titanium can be drawn more deeply when hot, and more difficult forming can be done hot than cold, in accordance with the general information developed on titanium alloys. Generally, depth of draw depends on composition, workpiece shape, required radii, forming temperature, die design, die material, and lubricant. Temperatures to 675 °C (1250 °F) have been used in deep drawing. Titanium alloys can be formed by additional processes, including press-brake forming, power spinning, rubber-pad forming, stretch forming, creep forming, and others.

Titanium: A Technical Guide Matthew J. Donachie, Jr., p39-45 DOI:10.1361/tatg2000p039

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 6

Castings FOR OVER TWO DECADES, large structural castings have been available for aerospace applications, but casting has not found universal acceptance. Titanium is a challenge to cast because it is a highly reactive metal and can interact with the atmosphere and with conventional refractories used in molding processes. Cost factors associated with wrought alloy processing led to continual efforts to develop and improve casting methods for titanium and its alloys. The result has been a somewhat checkered application of titanium castings with a more widespread acceptance of the practice in the past decade. Now, a combination of casting and hot isostatic pressing (HIP) processing produces titanium alloys with acceptable mechanical properties and significant cost advantages over forgings or fabricated structures. Casting is simply another method for fabricating titanium into shapes. It may be considered a near-net shape (NNS) technique, although as such it is somewhat less a true-net shape process than powder metallurgy. Titanium castings now are used extensively in the aerospace industry and, to a lesser but increasing measure, in the chemical process, marine, biomedical, automotive, and other industries. Figure 6.1 shows a typical aircraft part cast in Ti-6Al-2Sn-2Zr-2Mo-2Cr+Si, and Fig. 6.2 shows a variety of smaller cast titanium parts for use in corrosive media. For a while in the 1990s, sporting goods, primarily investment-cast golf club heads, were the second leading application area for titanium (second only to the commercial aerospace industry). However, titanium castings still represent a small portion of the titanium industry—several percent of total weight of product shipped each year.

Ti-6Al-4V. Their results supported the idea that cast titanium parts could be made with strength levels and characteristics approaching those of conventional wrought alloys. Subsequently, additional titanium components have successfully been cast from pure titanium and alpha-beta and beta alloys. In casting applications, commercially pure (CP) titanium (as ASTM grades 1, 2, or 3) is used for the vast majority of corrosion applications for the metal. Ti-6Al-4V is the dominant alloy for aerospace and marine applications. With increasing frequency Ti-6Al-2Sn-4Zr2Mo-Si is being selected for elevated-temperature service. Castings also have been supplied in alloys Ti-5Al-2.5Sn, Ti-15V-3Cr-3Sn-3Al, Ti-8Al-1Mo-1V, Ti-6Al-2Sn-2Zr-2Mo-2Cr+Si, and Ti-6Al-6V-2Sn, as well as several European alloys. Close to 90% of all castings produced are of Ti-6Al-4V, however, and the majority of the remaining 10% is CP titanium.

There are no commercial titanium alloys developed exclusively for casting applications. All titanium castings have chemical compositions based on those of the common wrought alloys. This situation is unusual because alloys in other metallic systems often have been developed specifically as casting alloys, frequently to overcome problems such as poor castability of a wrought alloy composition. No unusual problems regarding castability or fluidity have been encountered in any of the titanium metals cast to date.

Advantages of Cast Titanium and Titanium Alloys As a result of the development processes by casters in concert with the relevant gas turbine engine manufacturers, titanium castings were

Alloys Used for Casting Although a number of different titanium alloys were initially investigated, efforts on alloys such as Ti-5Al-2.5Sn were dropped after a few years and investigators concentrated on

Fig. 6.1

Cast and hot isostatically pressed alpha-beta titanium alloy (Ti-6222S) F-18 ejector block (after chemical milling, blending, and mill repair)

40 / Titanium: A Technical Guide proven to be reliable substitutes for wrought alloys. Subsequently, titanium castings moved on to larger components in the air frame industry and to smaller components in areas such as the biomedical, marine hardware, sporting goods, and chemical processing industries. The advantages of titanium castings over conventional wrought titanium are:

• • • •

Cost savings Reduced lead time to component delivery Ability to provide complex near-net shapes Ability to use rapid prototyping to produce evaluation components inexpensively (compared with the use of conventional die forging, machining, and joining processes)

The cost advantage may be attained through increased design flexibility, better use of available metal, or reduction in the cost of machining or forming parts. Generally, the more complex the part, the better the economics of using a casting. The use of rapid prototyping encourages designers to consider titanium alloy parts because component designs can be evaluated in a fraction of the time needed and at a very small fraction of the cost for producing a part using conventional wrought processing techniques. Rapid prototyping using computer-aided modeling was claimed to cut over 50% from the development time for a complex casting for a helicopter transmission adapter. Moreover, the final production casting itself was created with a 63% reduction in machining and assembly hours and a concurrent reduction in weight when compared with a forged titanium alloy design. Unlike castings of many other metals, titanium castings are equal, or nearly equal, in strength to their wrought counterparts. Strength guarantees in most specifications for titanium castings are the same as for wrought forms. Typical ductilities of cast products, as measured by elongation and reduction in area, are lower than typical values for wrought products of the same alloys. However, fracture tough-

Fig. 6.2

ness and crack-propagation resistance can equal or exceed those values for corresponding wrought material. Although the fatigue strength of cast titanium is inferior to that of wrought titanium, the fatigue strength of cast titanium can be enhanced by special processing and heat treatment.

Casting Technology Titanium castings have been cast in machined graphite molds, rammed-graphite molds, and proprietary investments used for precision investment casting. The principal technology that allowed the proliferation of titanium castings in the aerospace market was the investment casting method coupled with the adaptation of HIP to the most critical castings. Significant design complexity, tolerance, and surface-finish control have been achieved, and large parts approaching 1.5 m (5 ft) in diameter can be cast. Castings generally are produced by vacuum arc remelting titanium in a copper, water-cooled crucible and pouring into molds. If the initial investment can be justified, hearth-melting processes may find application in the future for the remelting of alloy prior to casting. Casting Concerns. Of necessity, the casting mold systems must be relatively inert to molten titanium. Proprietary lost-wax ceramic shell systems were developed by the various foundries engaged in titanium casting. Usually the face coats of the ceramic shells are made with the proprietary coatings and conventional refractory systems are used to add shell strength. Regardless of mold type (e.g., investment or rammed graphite), foundry practice focuses on methods to control both the extent of the reaction of the molten alloy and mold and the subsequent diffusion of reaction products inward from the cast surface. Depth of surface contamination can vary from nil on very thin sections to more than 1.5 mm (0.06 in.) on heavy

Investment-cast titanium components for use in corrosive environments

sections. On critical aerospace structures, the brittle alpha case is removed by chemical milling. The depth of surface contamination must be taken into consideration in the initial wax pattern tool design for investment casting. The wax pattern and resultant casting are made slightly oversize, and final dimensions are achieved by careful chemical milling. Metal pouring temperature, mold temperature, casting force (if centrifugally cast), and thermal conductivity of the metal and the mold, as well as the cooling environment, are all factors in the production of a good investment-cast titanium part. Casting Processes. The molten metal resulting after remelting is poured into either an investment mold or a rammed-graphite mold as just described. Pattern making and investment-cast mold techniques are similar to those used with superalloy technology. Although rammed-graphite molds are different from investment molds, they are similar to conventional sand molds. Cores are used to cast hollow parts. Porosity continues to be a potential problem, but one that is addressed for premium aerospace castings by the use of HIP as described subsequently. Once the mold-metal reaction problem is addressed, the most significant problem—with respect to titanium and titanium alloy castings—is achieving sufficient levels of superheat in the molten metal to maximize flow and mold-fill characteristics. In many cases, either a centrifugal table or mold preheating (or both) is used to ensure proper mold filling. A simplified schematic of one type of titanium casting process is shown in Fig. 6.3. A significant difficulty related to large titanium castings is the problem of porosity. However, by use of HIP, internal soundness of titanium castings can be improved to the point that no porosity or small voids can be detected.

Fig. 6.3

VAR furnace for melting titanium and centrifugal table for casting molten metal into the mold

Castings / 41 Weld repair is used to close gross defects after HIP. Because strength increases and ductility (toughness) decreases as oxygen level increases, oxygen content is a matter of concern regarding titanium alloy castings. Control of oxygen levels in cast components is achieved mostly by selection of melt stock, but hearth melting can make an additional improvement possible. An ingot with a low oxygen content generally results in a casting with the lowest oxygen content. The exact role of revert in oxygen-content control and in alloy element segregation is not clear; both revert and virgin ingots are used. Oxygen also can be introduced to the casting from the surface mold-metal interaction. The rammed-graphite method is the oldest mold technique used to produce titanium castings. The method uses a mixture of graphite powder and associated binders and water additions that are rammed against a pattern to form a portion of the mold. Individual mold segments are then fired and assembled for casting. Figure 6.4 shows some typical titanium parts produced by the rammed-graphite process. Most high-performance titanium alloy casting applications rely on the technique of investment casting. Here a wax pattern is produced and “invested” in a ceramic shell. After the mold is completed and dewaxed, it is fired and is then ready for casting. For small components, multiple patterns are used in the same feeding stem in order to create many parts at a single time. This technique can be ideal for biomedical application (Fig. 6.5 shows some titanium alloy investment-cast implants), but it is not very practical for large components used in aerospace work.

• Unnecessary tooling complexity should be •

•

avoided. The casting envelope should be designed for smooth transitions between thick and thin areas, to contain generous radii and fillets, and to contain tapered, thin-wall sections that promote maximum density (i.e., minimum shrinkage porosity). The maximum diametral capacity of HIP units must be considered if post-cast HIP is going to be required to meet mechanical property requirements.

Effect of Weld Repair Given the difficulties in filling molds during titanium casting, it is clear that weld repair is an integral step in the manufacturing process for titanium castings. Weld repair is used to repair surface-related defects. HIP is used to repair nonsurface-connected defects. Weld repair of titanium castings must be carefully executed because titanium can become embrittled owing to pickup of oxygen, hydrogen, and other contaminants during welding. Gas-tungsten arc welding (GTAW) is used with alloy filler rods to fill pores—cold shuts, such as HIP-induced surface depressions or surface-connected pores, that did not close during the HIP cycle. These filler rods may be extra-low interstitial (ELI) or normal interstitial to prevent excess oxygen buildup in the weld metal. Excellent quality weld deposits are routinely obtained when proper practice is used. Generally, all weld-repaired castings are stress-relief annealed after welding.

Design Considerations There are a number of broad guidelines to be followed when designing titanium castings:

• The supplier and customer must work to•

gether to identify the desired properties and to define the intended shape. The design must ensure that the mold is filled as completely as possible. (Weld repair, if it is required at all, should be limited as far as possible to noncritical areas.)

Brake torque tubes, landing arrestor hook, and optic housing components used in aerospace applications and cast using the rammed-graphite process

Fig 6.4

Fig. 6.5

Cast titanium alloy knee and hip implants

Weld deposits can have higher strength than the parent metal owing to microstructural differences resulting from the fast cooling rate of the weld process and some oxygen pickup. These differences can be eliminated by a high-temperature post-weld heat treatment, but stress-relief or anneal heat treatment is standard practice after weld repair. Properly executed weld repair does not degrade the fatigue resistance of cast titanium. Studies also have demonstrated that welding does not drastically affect the creep properties of cast Ti-6Al-4V, and similar results can be assumed for other titanium alloys. Rupture times for welded and unwelded Ti-6Al-4V bars were similar at 315 °C (600 °F) and at 650 °C (1200 °F). Strain rates at 2% creep strain and 650 °C (1200 °F) were the same for welded and unwelded bars.

Hot Isostatic Pressing In order to effectively sinter nonsurface-connected voids in the castings back together, HIP, the application of a hydrostatic pressure, is used to treat titanium castings. This process is performed at high temperature in a nonreactive medium such as argon. Fatigue strength is a vital property for typical titanium alloy applications. HIP results in a substantial improvement in fatigue strength of cast titanium alloys by a significant reduction in porosity. The hot isostatic pressing of titanium castings became a production reality in the late 1970s. Although HIP at 960 °C (1750 °F) seemed to produce superior properties for some

42 / Titanium: A Technical Guide applications of Ti-6Al-4V, the HIP schedule that has become the industry standard is 2 hours at 900 °C (1650 °F) under argon pressurized to 105 MPa (15 ksi). Specifications calling for 960 °C (1750 °F) HIP are being replaced by the more universal 900 °C (1650 °F) HIP. Initially, HIP was used with excellent results to salvage parts that had been rejected after radiographic inspection. The effectiveness of the technique gave rise to plans to use HIP for routine parts, but high cost made such plans economically questionable. However, for certain titanium casting configurations, adequate feeding by use of conventional risering is virtually impossible. Therefore, in the interest of maximum product integrity and mechanical properties, virtually all aerospace castings are hot isostatically pressed. HIP enables castings to meet aerospace nondestructive inspection standards (NDT). Gross section defects, such as shrinkage, subsequently are closed by welding. HIP becomes a means of avoiding, or at least minimizing, weld repair in many instances and provides increased surety of meeting specification requirements. HIP is considered by many to be a process that simplifies the problem of defining a standard for internal casting quality. Hot isostatically pressed parts also are aesthetically more acceptable. At the same time, use of HIP ensures that subsurface microporosity will be healed and, therefore, will not become exposed on a subsequently machined or polished surface to mar the finish or to act as a possible site for fatigue crack propagation. Fatigue-limited titanium castings always are HIP processed.

Heat Treatment From a technical viewpoint, HIP is a heat treatment, although some studies have claimed that HIP alone does little, if anything, to enhance mechanical properties of Ti-6Al-4V castings. Properties of hot isostatically pressed alloys are a function of the HIP temperature relative to the beta transus and the post-HIP heat treatment. With castings of marginal to substandard quality, HIP raises the lower limit

Table 6.1

of data scatter and raises the degree of confidence in the reliability of cast products. As noted above, a higher-temperature HIP cycle can result in better properties, but practical considerations for production operations mitigate against using cycles closer to the beta transus. After casting, but before hot isostatic pressing, a stress-relief step may be applied. However, because HIP itself is a heat treatment and, in turn, is usually followed by a high-temperature solution treatment at or above the HIP temperature, stress relief may not have any significant effect on final mechanical properties of hot isostatically pressed titanium castings. Heat treatment after HIP usually is necessary owing to the slow cooling rate from the HIP temperature. Reheat treatment is necessary to modify the structure of the HIP component. The heat treatment temperature is close to, and perhaps above, the beta transus (beta solution heat treatment). One heat treatment for Ti-6Al-4V consists of beta solution (in vacuum) at 1038 ± 14 °C (1900 ± 25 °F) for 2 to 3 hours plus an oil quench. This is followed by overaging in vacuum at 704 ± 14 °C (1300 ± 25 °F) for 2.5 to 3 hours and furnace cooling in argon to room temperature. This whole process is called beta solution treatment/overaging (beta-STOA). A more conventional heat treatment for Ti-6Al4V castings is an alpha-beta solution at 954 °C (1750 °F) for 1 hour. The casting is then fan cooled with an inert gas. It is subsequently aged at 621 °C (1150 °F) for 2 hours. Although many of the titanium castings produced commercially are supplied in the annealed condition, use of solution treatment for modifying structure and enhancing properties can significantly affect the potential for use of cast titanium. Most heat treatment schemes for titanium castings can be applied equally to powder metallurgy titanium parts. (Powder metallurgy is described in Chapter 7.) The main goal is to eliminate grain boundary alpha phase, large alpha plate colonies, and individual alpha plates to produce a finer structure and resultant property uniformity and an overall increase in strength. This can be accomplished by solution treatments or by temporarily alloying the casting with hydrogen. The details of some of the

Typical solution treatment

Titanium castings now are used extensively in the aerospace industry and, to a lesser but increasing extent, in chemical-process, marine, biomedical, sporting goods, and other industries Aerospace applications include major structural components weighing over 135 kg (300 lb) each and small switch guards weighing less than 30 g (1 oz) each. Titanium castings are used for the space shuttle; in wings, engine components, brake components, optical-sensor housings, ordnance, and other parts for military aircraft and missiles; and in gas turbine engines and brake components for commercial passenger aircraft. Additional aerospace applications include rotor hubs for helicopters and flap tracks for fighters. In the chemical-process industry, components for pumps, valves, and compressors are made of cast titanium. Marine applications include water-jet inducers for hydrofoil propulsion and seawater valve balls for nuclear submarines. Titanium castings are also used in various other industrial applications, such as well-logging hardware for the petroleum industry, special automotive parts, boat deck hard-

Dehydrogenation temperature

Typical annealing

°F

°C

°F

°C

°F

or aging treatment

Applied to product forms

… …

… …

… …

… …

Cast, P/M, I/M Cast

… … 760

… … 1400

845 °C (1550 °F) for 24 h 845 °C (1550 °F) for 1 2 h and 705 °C (1300 °F) for 2 h 540 °C (1000 °F) for 8 h 540 °C (1000 °F) for 8 h …

760 815

1400 1500

… …

Cast, P/M, I/M Cast

705

1300

…

Cast, P/M, I/M

1040 °C (1900 °F) for 1 2 h 1050 °C (1925 °F) for 1 2 h

··· …

··· …

BST ABST HVC

1040 °C (1900 °F) for 1 2 h and GFC(b) 955 °C (1750 °F) for 11 2 h and GFC …

… … 650

… … 1200

TCT CST

1040 °C (1900 °F) for 1 2 h …

595 870

1100 1600

900

1650

…

Intermediate treatment

°C

BUS GTEC

HTH

Cast Titanium Applications

Some heat treatment methods for modifying microstructure and properties of alpha-beta titanium alloy net shape products Hydrogenation temperature

Method(a)

methods tried and their areas of application are given in Table 6.1. Typical results of alpha-beta solution treatment (ABST), beta solution treatment (BST), broken-up structure (BUS) and high-temperature hydrogenation (HTH) methods are the elimination of large alpha plate colonies and grain boundary alpha phase. A substantial improvement in tensile and fatigue properties results. Stress-relief heat treatment is carried out below the intended HIP temperature, typically in the range of 704 to 843 °C (1300–1550 °F) for 2 hours. This type of treatment has no noticeable effect on the cast structure, although this temperature range would affect the wrought structure. Treatment is carried out in either vacuum or an inert atmosphere to minimize oxidation. Some large castings cool so slowly that no stress relief is needed.

… … … … 1600 870 (glass encapsulated) Cool to RT(c) No intermediate step (continuous process) Cool to RT

Cast, I/M Cast, I/M P/M, I/M

BUS, broken-up structure; GTEC, Garrett treatment; BST, beta solution treatment; ABST, alpha-beta solution treatment; HVC, Hydrovac process; TCT, thermochemical treatment; CST, constitutional solution treatment; HTH, high-temperature hydrogenation; P/M, powder metallurgy; I/M, ingot metallurgy. (a) Most data apply to Ti-6Al-4V, beta transus temperature approximately 995 °C (1825 °F). (b) GFC, gas fan cooled. (c) RT, room temperature

Castings / 43 ware, and medical implants. Titanium castings have been used for golf club heads and components of lightweight bicycles. An additional appreciation of some of the complex shapes available in cast-plus-HIP titanium alloys can be achieved by studying Fig. 6.6.

Cost Comparisons A major aircraft manufacturer made an in-depth study in which costs of precision titanium alloy castings were compared with costs of pans machined from forgings and blocks of both titanium and aluminum. On the average, metal-removal (machining) costs constitute about 60% of total fabrication cost of an airplane. The use of precision investment castings reduces machining cost to about 5% of total part cost compared to as much as 70 to 80% for the same part made from a forging or hogged out of a block. Figure 6.7 illustrates the relation of cost to number of units produced for a specific design

of an aircraft fitting. For all quantities, it was least expensive to produce the fitting as an investment casting. For a series of 16 parts from one model of commercial aircraft, the average cost of a single part was $749 (1988 dollars) when 200 units were hogged from titanium alloy blocks. The average cost for investment castings in the same production quantity was $227. This represented a saving of $835,100 for each lot of 100 airplanes constructed, if the parts were made from castings. For a series of eight parts from another model, average cost was $316 when the parts were machined from aluminum forgings but only $179 when the parts were made from titanium investment castings. This represented a saving of $109,800 for each lot of 100 airplanes.

Mechanical Properties Basic Properties. Because most castings used in aerospace applications are Ti-6Al-4V,

Table 6.2 Typical room-temperature tensile properties of titanium alloy castings (bars machined from castings) Ultimate strength

Yield strength

Alloy(a)(b)

MPa

ksi

MPa

ksi

Elongation,%

Reduction of area, %

Commercially pure (grade 2) Ti-6Al-4V, annealed Ti-6Al-4V-ELI Ti-6Al-2.75Sn-4Zr-0.4Mo-0.45Si, β-STA(c) Ti-6Al-2Sn-4Zr-2Mo, annealed Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.7Nb-0.35Si, β-STA(c) Ti-6Al-2Sn-4Zr-6Mo, β-STA(c) Ti-3Al-8V-6Cr-4Zr-4Mo, β-STA(c) Ti-15V-3Al-3Cr-3Sn, β-STA(c)

552 930 827 938 1006 1069 1345 1330 1275

80 135 120 136 146 155 195 193 185

448 855 758 848 910 952 1269 1241 1200

65 124 110 123 132 138 184 180 174

18 12 13 11 10 5 1 7 6

32 20 22 20 21 8 1 12 12

Specification minimums are less than these typical properties. (a) Solution treated and aged (STA) heat treatments can be varied to produce alternate properties. (b) ELI, extra low interstitial. (c) β-STA, solution treatment within the beta-phase field followed by aging

the most extensive data have been developed for this alloy. Typical room-temperature tensile properties are given in Table 6.2 for cast CP titanium and for eight cast titanium alloys. Generally, cast titanium alloys are equal, or nearly equal, in static strength to wrought alloys of the same compositions. However, typical ductilities are below the typical values for comparable wrought alloys, yet they are still above the guaranteed minimum values for the wrought metals. While cast property values compare favorably with those of wrought alloys, fatigue behavior is not always quite so favorable, as can be seen in Fig. 6.8. HIP helps considerably to raise the fatigue design limits, but not to the level of wrought alloys. Generally, improvement in fatigue properties and reduction in the scatter of fatigue data are achieved through HIP. Also, heat treatment modification, such as the beta-STOA, may contribute to a general improvement in the level of fatigue strength for alloy castings. Although castings of alloys such as Ti-6Al-4V generally will have static properties somewhat lower and fatigue properties lower than wrought products, properties such as fracture toughness, fatigue crack growth rate, and stress-corrosion resistance can be superior to those of mill-annealed wrought Ti-6Al-4V. Figure 6.9 compares plane-strain fracture toughness values for Ti-6Al-4V castings with values for Ti-6Al-4V plate and for other wrought titanium alloys. The high toughness is due to the beta-processed-type microstructure inherent in castings after post-HIP heat treatment. Figure 6.10 compares fatigue crack growth rate for wrought beta-annealed Ti-6Al-4V alloy with cast and cast-plus-HIP versions of the alloy. Note that the data generally all fall in the same approximate scatter band. As mentioned above, special heat treatments to modify the microstructure of HIP-processed titanium alloy castings have been developed. Table 6.3 and Fig. 6.11 give some mechanical property results for Ti-6Al-4V heat treated as shown in Table 6.1. Design Properties. One consideration that should not be overlooked when determining the properties of cast titanium alloys is the origin of test material. Separately cast test bars, bars cast on parts, and bars machined from castings

Cost comparison for one titanium alloy aerospace design machined from blocks, forgings, and precision investment cast

Fig. 6.7 Fig. 6.6

Typical complex shapes cast in titanium alloys. Courtesy of Precision Castparts Corp.

44 / Titanium: A Technical Guide Table 6.3 Some mechanical properties of wrought beta-annealed product and castings of an alpha-beta titanium alloy (Ti-6Al-4V) given special heat treatments (see Table 6.1) Yield strength Material condition(a)

As-cast Cast HIP BUS GTEC BST ABST TCT CST HTH Typical wrought β-annealed

Ultimate tensile strength

KIc

MPa

ksi

MPa

ksi

Elongation, %

Reduction of area, %

ksi in.

MPa m

896 869 938 938 931 931 1055 986 1055 860

130 126 136 136 135 135 153 143 153 125

1000 958 1041 1027 1055 1020 1124 1055 1103 955

145 139 151 149 153 148 163 153 160 139

8 10 8 8 9 8 6 8 8 9

16 18 12 11 15 12 9 15 15 21

97 99 ··· ··· ··· ··· ··· ··· ··· 83

107 109 ··· ··· ··· ··· ··· ··· ··· 91

HIP, hot isostatic pressing; BUS, broken-up structure; GTEC, Garrett treatment; BST, beta solution treatment; ABST, alpha-beta solution treatment; TCT, thermochemical treatment; CST, constitutional solution treatment; HTH, high-temperature hydrogenation. (a) All conditions (except as-cast) are cast plus HIP.

Yield strength, ksi 120 140 160 180 200 Range of 80 test values for wrought titanium alloys

80

60 60 40

40

20

Plate

20

Fracture toughness, ksi √in.

Fracture toughness, MPa √m

100

100

Castings 0 600

800

1000

1200

0 1400

Yield strength, MPa

Fig. 6.8

Comparison of smooth axial room-temperature fatigue in cast, cast/plus-HIP, and a wrought alpha-beta titanium alloy (Ti-6Al-4V)

Scatterband comparison of fatigue crack growth rate for an alpha-beta titanium alloy (Ti-6Al-4V) in beta annealed wrought form, and in cast and cast-plus-HIP forms

Fig. 6.10

Fracture toughness of an alpha-beta titanium alloy (Ti-6Al-4V) casting compared to that of plate and other titanium alloys

Fig. 6.9

Comparison of smooth axial fatigue behavior of Ti-6Al-4V investment castings subjected to various heat treatments (see Table 6.1). BUS, broken-up structure; HTH, high-temperature hydrogenation; BST, beta solution treatment; ABST, alpha-beta solution treatment; CST, constitutional solution treatment; GTEC, Garret treatment

Fig. 6.11

Castings / 45 have been used for the determination of properties. Typically, data are reported from separately cast test bars, which are the cheapest source. The least amount of data is derived from test bars machined from castings, which are the most expensive source. Property differences can be noted depending on test specimen origin (Table 6.4), a common fact of life in the generation of design data. A second consideration is that the design for an integrally cast titanium component may not require quite the same strength level as would wrought ingot metallurgy material.

Table 6.4 Comparison of cast Ti-6A1-4V room-temperature tensile properties from three sources of test material Mechanical property

Ultimate tensile strength (UTS), MPa (ksi) Yield strength (0.2%), MPa (ksi) Elongation, % Reduction in area, %

Separately cast

Cast on part

Machined from casting

907 (113.6) 821 (119.1) 10.6 20.8

885 (128.5) 810 (117.5) 10.1 22.2

850 (123.4) 780 (113.2) 8.6 15.6

Heat treatment: HIP at 899 °C (1650 °F), 103 MPa (15 ksi), 2 h plus annealing at 732 °C (1350 °F), 2 h

Only after casting trials are run and properties are determined should judgments be

made concerning the merits of any casting technique.

Titanium: A Technical Guide Matthew J. Donachie, Jr., p47-53 DOI:10.1361/tatg2000p047

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 7

Powder Metallurgy FAR LESS TITANIUM is used in production applications than might be anticipated based on its performance durability. Special high-performance application areas, such as aerospace and sporting goods (e.g., golf club heads and racing bicycles) applications, biomedical implants, and other industrial and marine corrosion service, will pay for the higher price of titanium alloy components. However, the initial cost of titanium or titanium alloys, the costs of processing and forging, and the cost of machining often combine to make it difficult to decide in favor of titanium. As indicated in Table 7.1, for three recent United States military aircraft, a very large difference existed between the planned and realized titanium content. A drive developed, therefore, to reduce the net cost of titanium use by producing net shape and near-net shape (NNS) technologies. One result of these cost reduction efforts was the introduction and acceptance of cast titanium components. (See Chapter 6 for further information on cast components.) Powder metallurgy (P/M) technology was developed as an alternative process to produce components. P/M products having properties similar to those of other forms are now being manufactured. Table 7.2 compares room-temperature properties of titanium and several titanium alloys in wrought, cast, and powder forms. The processes for manufacture of titanium powders are slow and costly, however, and this has resulted in slow growth of powder metallurgy as a means of manufacturing titanium parts. The most important considerations in producing titanium P/M components are oxygen content, purity, and contaminants. Oxygen has the same undesirable effects on P/M parts as it has on wrought products. Powders, especially very fine powders, must be handled very carefully because they have a high affinity for oxygen and can be highly pyrophoric. Purity is important for all powder products and is critical for the consolidation of blended elemental fines where the void content must be minimal—the residual chloride content is a major factor in the amount of residual porosity of the final product. Contaminants are detrimental to fatigue

performance and are key in terms of the final fatigue properties that can be obtained.

Benefits of Powder Metal Processing Titanium P/M fabrication offers the potential for true net shape capability combined with mechanical properties that are equal to, or exceed, cast and wrought products. This is due to a lack of texture and segregation and to the fine, uniform grain structure inherent in titanium P/M products. Equivalent strength levels to wrought products, along with substantially reduced ma-

chining and scrap, combine to make P/M titanium products attractive alternatives to conventional ingot metallurgy, involving wrought titanium alloys, and to castings. In order to fully exploit the P/M potential of titanium, substantial effort has been made to reduce the cost of powder and powder-base components. Costs for optimum powder and for Table 7.1 Titanium content of some recent military airframes System

Early design, wt%

Final concept, wt%

24 42 50

3 22 34

C-5 (cargo) B-1 (bomber) F-15 (fighter)

Table 7.2 Comparison of typical room-temperature properties of wrought, cast, and P/M titanium alloy products Tensile strength

Yield strength

Charpy impact strength

Product and condition

MPa

ksi

MPa

ksi

Unalloyed titanium Wrought bar, annealed Cast bar, as-cast P/M compact, annealed(b)

550 635 480

80 92 70

480 510 370

70 74 54

18 20 18

33 31 22

815 795 795

118 115 115

710 725 715

103 105 104

19 10 16

34 17 27

… … …

875 875

127 127

13 16

25 27

860 895 825 825–855 855–900 860–925 870 740–785 840

125 130 120 120–124 124–131 125–134 126 107–114 122

9 8 12 6–10 5–8 5–8 8 5–8 12

895

130

4

Ti-5Al-2.5Sn-ELI Wrought bar, annealed Cast bar, as-cast P/M compact, annealed and forged(c)

Ti-6Al-4V Wrought bar, mill annealed 965 140 Wrought bar, recrystallize 970 141 annealed Wrought bar, beta annealed 955 139 Cast bar, as-cast 1000 145 Cast bar, annealed 930 135 Cast bar, annealed(d) 895–930 130–135 Cast bar, STA(e) 935–970 136–141 Cast bar, STA(f) 965–1025 140–149 Cast bar, HIP 1000 145 P/M compact, annealed(b) 825–855 120–124 P/M compact, annealed 925 134 and forged(c) P/M compact, STA(g) 965 140

Elongation, Reduction % in area, %

J

ft ⋅ lbf

Fracture toughness MPa m

ksi in.

… … …

… … …

… … …

… … …

… … …

… 27

… 20

… 52

… 47

21 16 22 10–15 6–14 10–14 16 8–14 27

… … 17.5 … … … … … …

… … 24 … … … … … …

91 107 103 … … … 109 … …

83 97 94 … … … 99 … …

6

…

…

…

…

35(a) 26(a) 26(a) 19(a) … …

P/M, powder metallurgy; STA, solution treated and aged; HIP, hot isostatically pressed. (a) Charpy values at –40 °C (–40 °F). (b) ~94% dense. (c) Almost 100% dense. (d) Annealed at 730 or 845 °C (1345 or 1555 °F). (e) Alpha-beta STA: 955 °C, 1 h, cool + 620 °C, 2 h (1750 °F, 1 h, cool + 1150 °F, 2 h). (f) Beta solution treated and aged STA: 1025 °C, 1 h, cool, + 620 °C, 2 h (1875 °F, 1 h, cool + 1150 °F, 2h)

48 / Titanium: A Technical Guide consolidation to produce fully dense, highquality compacts remain an obstacle to powder use in the titanium alloy field. Improved low-cost powder production and fabrication procedures, coupled with improved nondestructive testing (NDT) techniques and realistic NDT standards, are still required.

Alloys Used in Powder Metallurgy Applications Many alloy compositions have been produced in powder form. Alloys include:

• • • • • • • •

Ti-6Al-4V Ti-6Al-6V-2Sn Ti-5Al-5Mo-1.5Cr Ti-5Al-2Sn-2Zr-4Cr-4Mo Ti-6Al-2Sn-4Zr-2Mo Ti-6Al-2Sn-4Zr-6Mo Ti-10V-2Fe-3Al Ti-11.5Mo-6Zr-4.5Sn

Well over 90% of the P/M developmental efforts have employed only the alpha-beta alloy Ti-6Al-4V, and most references in this Chapter involve that alloy. Titanium P/M chemistries are based on those of common wrought alloys, so no distinct alloys exist exclusively for P/M. This approach mirrors that for castings. It is a recognition of the extreme difficulty of introducing both a new chemistry and a new process to the manufacturing cycle. This difficulty is especially pertinent in mission-critical applications, such as those in the aerospace industry, and has driven the titanium business since its inception around the middle of the past century. This conservative approach also results in part from the existence of ingot metallurgy products and a known foundation of data that encourages direct substitution according to product chemistry. However, another reason for the conservative approach is the availability of barstock and wrought mill products, which often are the sources of feedstock in powder making. One of the other important features of P/M processing is the potential for developing unique, nonstandard chemistries that may not be able to be processed by any other techniques. Rapid solidification processing has been investigated for nearly two decades at this point and does offer unique opportunities, but at a significant cost disadvantage. Chapter 14 discusses some aspects of the continuing search for improved properties by the rapid solidification route.

Titanium Powder Metallurgy Production Processes Titanium alloy P/M technology has been developed as a net shape technique only in the past quarter century, although P/M techniques have existed for more common industrial met-

als, such as ferrous alloys, aluminum alloys, and copper alloys, for years. In general, P/M titanium components are produced by two different processes. In the blended elemental (BE) method, a blend of elemental powders, along with master alloy or other desired additions, is cold pressed into shape and subsequently sintered to higher density and uniform chemistry. In the prealloyed (PA) method, hot consolidation is performed on powder produced from prealloyed stock. In general, the BE method produces parts with lower property levels at a lower cost. Basically, the BE method is a cold press (CP) or cold isostatic press (CIP) and vacuum sinter process that results in less than fully dense material. As a result, this method customarily provides relatively lower-cost products that have good tensile strength, fracture toughness, and fatigue crack growth rates, but also have lower fatigue strength. Developments in powder selection, compaction techniques, and postcompaction processing have made it possible to produce fully dense BE compacts, and it has been claimed that properties equaling or surpassing those of ingot metallurgy products can be achieved. PA powder compacts, on the other hand, are always fully dense with good mechanical properties, including fatigue strength. BE components are relatively inexpensive and can be suitable for noncritical applications. The PA method is intended to produce high-performance components in complex shapes with properties comparable to or exceeding those of ingot metallurgy versions of the same alloys.

Powder-Making Process

tilled is more pure than any of the previous sponge fines. Owing to plant closings that occurred in the titanium industry during the late 1980s and the 1990s, sponge fines are less available than in prior years, and alternate sources of elemental titanium powder are being developed. Of course, elemental powders can also be produced by the same methods used to produce prealloyed powder. Powder based on sponge fines has an irregular shape, which is an advantage in producing green (pressed but not sintered) shapes of sufficient strength to be handled in the subsequent sintering operations. Parts produced with BE powders are shown in Fig. 7.1 Prealloyed Powder. Each particle of a PA powder exhibits the same alloy chemistry as the desired alloy. This is because the feed stock for the PA powder production processes utilizes cast or wrought alloy material. Although the superalloy industry managed to adapt gas atomization to powder production, titanium alloys have relied not only on gas atomization but also on other processes unique to the chemistry and metallurgy of titanium, which is a very reactive metal. Some of the PA powder production processes are:

• Rotating-electrode process (REP), a centrifugal atomization process

• Plasma rotating-electrode process (PREP), a centrifugal atomization process

• Hydride/dehydride (HDH) process • Gas atomization (GA) process Other processes exist or are under development but have no current commercial use. Those evaluated methods include:

• Powder under vacuum (PSV, from pulverizaElemental Powder. By necessity, the powder production processes for titanium and its alloys are limited by the inherently high reactivity of the metal. Thus, nontraditional and, therefore, high-cost processes have been the norm in the industry. Sponge fines of titanium and aluminum-vanadium master alloy powder produced by conventional P/M techniques have been used in the BE process to produce P/M titanium alloy parts. The titanium sponge fines are obtained as byproducts of the Kroll magnesium reduction process for titanium. The sponge is crushed before consolidation and, although most of the sponge is of acceptable size for further conventional processing, sponge fines exist that are not conveniently incorporated into the vacuum arc remelted (VAR) sponge consolidation process. Consequently, such fines represent a relatively low-cost source of elemental titanium powder. Sodiumreduced sponge fines were more pure than magnesium-produced sponge fines, but sodium reduction is not a current manufacturing technique for titanium, and powders from that source are no longer available. Powder from magnesium-reduced sponge that is vacuum dis-

tion sous vide)

• Continuous shot casting (CSC) • Pendant drop (P-D) • Flash reduction of titanium (alloy) vapors Some additional effort has been directed to elemental titanium and PA powder production by chemical methods, and other entirely different techniques have also been given some consideration. Still, the development of a new technique that produces an inexpensive, high-quality starting powder is a prerequisite to an expansion of the titanium P/M products market Current PA powder production by the HDH process uses the concept of comminution of brittle materials to produce powder. Titanium and its most common alloys are hydrogen embrittled by heating in a hydrogen atmosphere. A variety of solids can be used as starting stock, although light-gage stock has a greater surface-to-volume ratio and hydrides more rapidly. After hydriding, the product is extremely friable and either spontaneously reduces to powder or is easily pulverized. The powder is then dehydrided by heating in a vacuum.

Powder Metallurgy / 49 HDH powder is similar in morphology to sponge fines. Both are irregular particles that have low packing density and low powder flow rates into dies or cans. The HDH process tends to increase oxygen content, and other contaminants can be present. Thus, HDH powders may not be suitable for critical applications. GA and rotating electrode-type processes (REP and PREP) tend to produce spherical powders. Such powders flow easily and pack to a very consistent high density but do not bond well in cold pressing. GA does not use centrifugal atomization but REP and PREP do. In GA, a molten metal stream flows through a nozzle

into a ring of inert gas jets where it is atomized by the gas pressure. REP uses a tungsten arc to melt the titanium or its alloy from a rotating feedstock. The liquid is rapidly spun off as droplets to cool in the atmosphere. In a hardened form, these droplets collect in the bottom of a chamber. PREP uses a plasma arc to melt the alloy from a rotating feedstock to produce a powder, much as occurs in REP. (GA, REP, and PREP are covered in various powder metallurgy texts if further information is required. GA is also covered in books about superalloy processing, where the process is extensively used.)

The principal feature of both REP and PREP is the ability to retain low interstitial element content with minimal contamination. One advantage of the PREP method over REP is the elimination of tungsten inclusions, which in the REP method are produced by the tungsten electrode heat source. Both processes have a cleanliness advantage over GA, where inclusions can be produced from any ceramic used in the container nozzle. For PA powders, a number of processes have been developed to improve the performance of the end product by removing contaminants or adjusting the final microstructure. These include:

• Jet classification • Electrostatic separation • Electrodynamic degassing

(a)

(b)

(c)

(d)

Characterization of both the as-produced powder particles and the foreign particles that may be present at the loose powder stage can assist in quality control. It has been clearly demonstrated that both the basic microstructure and contaminants present influence mechanical properties, particularly fatigue. A method that is useful in separating out foreign particles for subsequent classification (but not as a cleaning method for titanium) is water elutriation, which distinguishes between particles on a density basis. Powder produced by the REP and PREP processes is characteristically coarser than GA superalloy powders. Sieve and chemical analyses of Ti-6Al-4V REP powder used to make some demonstration aerospace components are given in Tables 7.3(a) and (b). Figure 7.2 shows some parts made from PA powder.

Consolidation and Shapemaking Several processes of consolidation and shapemaking are available. Consolidation processes are:

• Mechanical die pressing (CP) plus vacuum sintering

• Cold isostatic pressing (CIP) plus vacuum sintering

• Vacuum hot pressing (VHP) • Hot isostatic pressing (HIP) • CIP plus vacuum sintering plus HIP (CHIP)

(e)

Fig. 7.1

Aerospace and automotive Ti-6Al-4V parts produced using blended elemental powder. (a) Impeller. (b) F-18 pivot fitting. (c) Missile housing. (d) Lens housing. (e) Automotive cylinder

Of these, it is claimed that the latter three are capable of producing fully dense compacts. Of those three procedures, HIP within a heated pressure vessel or autoclave is the most common procedure for critical parts. By simultaneously applying temperature and hydrostatic pressure, full density in the part is attained. Press consolidation allows rapid (or lowertemperature) compaction of powder inside a shaped, evacuated can. Very high pressures are attainable and, with certain die designs, close to

50 / Titanium: A Technical Guide 100% density is claimed after pressing and vacuum sintering. Powder can be compacted by VHP. In this process, powder is hot compacted in a forge press that is adapted to a vacuum system. Dies press the powder to an essentially 100% density in the required shape. The major disadvantages of this process appear to be the lack of flexibilTable 7.3(a) Sieve analysis of Ti-6Al-4V rotating-electrode process powder Sieve size

35 45 60 80 120 170 230 325 >325

Radius, μm

Amount retained, %

500 354 250 177 125 88 63 44 <44

0.01 1.70 14.95 38.28 33.64 8.95 1.87 0.57 0.03

ity in shapes that are pressable and the size of parts that can be produced. With respect to HIP, this process uses the same consolidation equipment as that used for closing casting porosity, although pressure and temperature conditions differ. Most HIP processes use metal can technology, and fairly complex shapes are produced. Limited machining envelopes are incorporated in the design of the cans or dies used, but the requirements of Table 7.3(b)

Fig. 7.2

Chemical analysis of Ti-6Al-4V rotating-electrode process powder Composition, %

State during analysis

Powder batch Typical wrought (MSRR 8681) As-HIP

Al

V

5.97 5.5–6.75

3.95 3.5–4.5

6.22

4.01

Composition, ppm Fe

O

0.20 0.3(b)

1070 2000(b)

0.19

N

4 500(b)

1860–1930 124–176

C

(a) 800(b) 130–156

H

7 100(b) 40–87

W

36 … …

(a) No reliable value available. (b) Maximum value

(a)

(c)

NDT limit the extent to which near net shape (NNS) can be approached. Practical considerations of component complexity also affect the final compact volume and geometry. The metal can is shaped to the desired configuration by state-of-the-art sheet metal methods. These include brake bending, press forming, spinning, and superplastic forming. Carbon steel is the best suited container material because it reacts minimally with titanium. It forms titanium car-

(b)

(d)

(e)

Prealloyed powder aerospace parts. (a) F-14 fuselage brace. (b) Engine mount support fitting for the F-18 aircraft. (c) Cruise missile engine impeller. (d) Four section welded nacelle frame structure. (e) Titanium aluminide demonstration impeller. Parts were produced by the crucible ceramic mold method.

Powder Metallurgy / 51 bide, thereby inhibiting further reaction. A limitation for all HIP applications is the size of the largest HIP chamber. The maximum diameter available is a little over 1.2 m (4 ft) while the maximum length is approximately 2.4 m (8 ft). A variation of the HIP process, the crucible ceramic mold process (CCMP) has similarities to the technology used for the investment casting process. Shaped wax patterns are made and a ceramic mold is prepared. After dewaxing and firing, the mold is evacuated, filled, outgassed, and sealed. (This is similar to the way metal cans used in the standard HIP process are treated.) The sealed mold is then hot isostatically pressed. HIP-CCMP is capable of producing more complex shapes than those produced by HIP with standard can technology. Shapes also can be produced by means of cold isostatic pressing (CIP) and molds are much less expensive than those required for HIP. CIP, while similar to HIP is much less elaborate and less expensive than HIP. With CIP, vacuum sintering (high-temperature heating for a long period) is required in order to reach 95 to 99% density. HIP processes generally are required to reach 100% density. Blended Elemental Powders. The basic BE powder compaction methods are CIP and cold press (CP) consolidation. These methods may be followed by vacuum sintering in order to reach 95% density. They also may be followed by HIP to achieve almost 100% density. Considerable emphasis has been placed on CIP, CIP plus vacuum sintering, and CIP plus vacuum sintering plus HIP. Cost savings realized in BE powder compaction and shapemaking result from reduced raw material requirements and reduced handlingand-process cycle time. BE use tends to assume that less than 100% density is acceptable. BE compacts typically have a density before sintering (green density) of >85%. Vacuum sintering can produce densities of about 95%, and careful control of powder size and size distribution can produce densities of 99%.

Fig. 7.3 nology, Inc.

Impeller made from Ti-6Al-4V blended elemental powder. Courtesy of Dynamet Tech-

Porosity in BE compacts is the result of chloride residues in the sponge. Use of vacuum-distilled sponge fines or other low-chloride sponge is claimed to produce essentially 100% dense compacts. Sintering is performed at temperatures in the range of 1100 to 1315 °C (2100–2400 °F) in a vacuum to prevent gas contamination. The high sintering temperature is needed to create good particle bonds and to homogenize the chemistry. The sintering temperature is well above the beta transus of all common titanium alloys. CP plus sintering is currently the preferred method for producing low to about 80% dense parts for noncritical applications. Higher-density parts are made using CIP plus sintering. Elastomeric molds have been used to produce extremely complex shapes, such as the impeller shown in Fig. 7.3. Part size is limited to a maximum diameter of about 60 cm (24 in.); length is limited by the availability of CIP equipment. Dimensional length tolerance using CIP plus sintering is about ±0.02 mm/mm (±0.02 in/in.). For maximum BE density and properties in a finished part, the CHIP process is used. A 15.3 kg (34 lb), 100% dense airframe component made by means of the CHIP method from BE Ti-6Al-4V powder (with an extra-low chloride content) is shown in Fig. 7.4. By contrast, a 45 kg (100 lb) wrought billet would have been needed for more traditional ingot metallurgy methods. Prealloyed Powders. The principal method of consolidating PA powders appears to be HIP. CCMP and VHP also have been evaluated. Direct processing of PA powders to mill products can be accomplished. (This also is possible with BE powders.) Plate and barstock have been produced, although cost effectiveness is questionable. Preforms for subsequent forging also have been considered. (Use of preforms is common in the P/M field; preconsolidated billets—from HIP or extrusion—are common in the superalloy field.) Preconsolidated billets are used as stock for the isothermal forging of aircraft gas turbine components.

Conventional CP plus sintered BE P/M titanium might achieve a theoretical density of 94 to 96%. Further working or processing is required to achieve full density and to maximize properties. The use of high-density (but less than fully dense) titanium alloys as preforms could offer advantages. A prototype compressor blade preform was cold isostatically pressed with blended elemental Ti-6Al-4V powder and sintered to approximately 95% density. The finished forged product was achieved with only one blow, resulting in minimal flash (Fig. 7.5). Consequently, minimal scrap resulted. Conventional forging of this part would have required substantially more barstock and several sets of breakdown tooling. A substantial improvement in economics thus was realized with P/M processing. Compaction by HIP is commonly carried out at a temperature below the beta transus to better control microstructure and minimize reactions with the can. Powder cleanliness is a major factor governing the properties of consolidated PA components. Even a very low level of foreign particles can lead to a substantial loss of fatigue properties.

Postcompaction Treatments P/M titanium alloys are sometimes subjected to postcompaction working. Compacts to be subsequently worked are known as preforms. The use of P/M preforms can promote more confidence in property levels of P/M titanium alloy products because many engineers feel that some level of working (i.e., deformation) enhances inspectability of the product and increases uniformity of products. Unfortunately, process economics do not allow subsequent working because it nullifies the objectives of powder technology by increasing costs. Heat treatment response after compaction depends on the particular alloy and the P/M processing method. In the case of BE Ti-6Al-4V alloy, for example, the only successfully used heat treatment has been the bro-

Cold isostatically pressed-plus-sintered compressor blade preform and final part forged from preform. At left, a preform; at right, finished part. Courtesy of Imperial Clevite Technology Center

Fig. 7.5

Fig. 7.4

Connector link arm for F100 gas turbine engine. Courtesy of Imperial Clevite, Inc.

52 / Titanium: A Technical Guide ken-up structure (BUS) heat treatment, in which a quench from the beta field is followed by long-term annealing at 850 °C (1560 °F). After such heat treatment, the microstructure of the alloy shows a broken-up alpha phase in a matrix of beta. This microstructure provides a significant improvement in tensile and fatigue strengths over the standard heat treatments—solution treated and aged (STA) or solution treated, overaged (STOA)—for the alloy.

Applications Although titanium P/M technology normally is associated with the aerospace industry, it also has received use in other industries. It is used in the chemical industry for filters, fasteners, fittings, and valve components. It has been considered for use for possible automotive applications.

Cost Factors Sufficient data are now on hand to allow both PA and BE powder compacts of Ti-6Al-

4V to be used with confidence. Cost remains the major concern. BE P/M processes can be cost effective for less critical parts, when parts that are not fully dense are acceptable. Table 7.4 lists the forging weight, P/M product weight, final part weight, and, thus, anticipated potential cost savings estimated for a few parts produced by using PA powder and the CCMP processing technique. These estimates suggest that cost savings realized by P/M processing compared to forged parts could range between 20 and 50%, depending on the size and complexity of the part and production quantity. Costs of titanium components are greatly influenced by the volume of the production run (as is common in all P/M applications). One must add to this factor the costs of achieving critical properties by means of super-clean powders and the even more costly compacting techniques (e.g., HIP and VHP). Powder costs still do not prove competitive with cast or wrought processing for many titanium applications. As discussed previously, cost reduction often is the major reason for using P/M processing instead of conventional alloy production. Generally, P/M processing can be attractive for large, complex parts that have a high buy-to-fly ratio when fabricated by conven-

Table 7.4 Typical titanium parts produced from prealloyed powder using hot isostatic pressing-crucible ceramic mold process (HIP-CCMP), showing weight and cost savings using powder Part weight Forged billet Component

kg

F-14 fuselage brace F-18 engine mount support F-18 arrestor hook support F107 radial-compressor impeller F-14 nacelle-frame

Fig. 7.6

2.8 7.7 79.4 14.5 142.8

P/M part

Final part

lb

kg

lb

6.2 17.0 175.0 32.0 315.0

1.1 2.5 24.9 2.8 82.1

2.5 5.5 55.0 6.2 181.0

kg

0.77 0.5 12.8 1.6 24.1

lb

% save

1.7 1.1 28.4 3.6 53.2

50 20 25 40 50

tional methods; however, casting is a competing and proven technology. Only a significantly lower cost for PA P/M compacts will enable them to compete with castings and replace wrought alloys. For specialized applications in which powder with a rapid solidification rate is required, costs are likely to be much greater than with current titanium powder technology. However, there will be a performance payback that might justify powder use in such instances.

Mechanical Properties Mechanical properties of titanium P/M parts are determined by the type of powder (PA or BE) used, along with the sophistication of the consolidation techniques employed. When high-temperature, long-time processes with slow cooling rates—HIP, for example—are used, microstructures “as-HIPed” are more coarse than desirable. When the microstructure is refined by heat treatment, working, combinations of both, or other techniques, optimum properties result. Tensile and creep-rupture properties also are moderately affected when less than full densification is achieved. Porosity and small inclusions do not affect static properties as much as microstructure does. Cyclic properties such as fatigue are critically dependent on defects such as inclusions or porosity in the P/M parts as well as on microstructure. Tensile properties of several titanium alloys produced from BE powders compacted by cold pressing and sintering are shown in Fig. 7.6. Strength and ductility levels of the pressed and sintered materials are comparable to wrought materials. Tensile and fatigue properties for PA P/M compacts prepared using different processing conditions are shown in Table 7.5.

Typical tensile properties of blended elemental titanium alloy powder compacts. Shaded areas represent observed ranges.

Powder Metallurgy / 53 The fatigue properties of BE powder compacts and hot isostatically pressed PA powder are compared with wrought annealed material in Fig. 7.7. The fatigue properties of PA pow-

Table 7.5

sult in lower fatigue capability. The application of CHIP to BE powder and the reduction of salt content should increase fatigue strength.

der, when pressed to 100% density and with optimized microstructure, can be equivalent to wrought alloy product. Remnant salt and porosity in customary BE powder compacts re-

Tensile and fracture toughness properties of Ti-6Al-4V prealloyed P/M compacts processed under various conditions 0.2% yield strength

Ultimate tensile strength

Titanium PA powder preparation

Reduction KIc or (KQ)

Compaction temperature

MPa

ksi

MPa

ksi

Elongation, %

in area, %

MPa m

ksi in.

Powder process

°C

°F

HIP HIP (PSV) and β annealed

861 1020

125 148

937 1095

136 159

17 9

42 21

(85) (67)

(77) (61)

PREP PSV

925 950

1695 1740

HIP and BUS treated HIP and TCP treated HIP and annealed (700 °C, or 1290 °F) (REP) HIP, annealed (700 °C, or 1290 °F), and STA (955–480 °C, or 1750–855 °F) HIP and annealed (700 °C, or 1290 °F) (PREP) ELI; HIP (as-compacted) ELI; HIP and β annealed

965 931 820 1034

140 135 119 150

1048 1021 889 1130

152 148 129 164

8 10 14 9

17 16 41 34

… … (76) …

… … (69) …

PREP PREP REP REP

925 925 955 955

1695 1695 1750 1750

882 855 896

128 124 130

944 931 951

137 135 138

15 15 10

40 41 24

(73) (99) 93

(67) (90) 85

PREP REP REP

955 955 955

1750 1750 1750

HPLT and HIP (as–compacted) HPLT, HIP, and RA (815 °C,or 1500 °F) HIP and rolled (955 °C, or 1750 °F)(T) HIP, rolled (955 °C, or 1750 °F), and β annealed L or LT T or TL HIP, rolled (950 °C, or 1740 °F), and STA (960–700 °C, or 1760–1290 °F) HIP, forged (950 °C, or 1740 °F), and STA (960–700 °C, or 1760–1290 °F) VHP (830 °C, or 1525 °F) (as-compacted) VHP (760 °C, or 1400 °F) (as-compacted) ROC (900 °C, or 1650 °F) (as-compacted) ROC (900 °C, or 1650 °F) and RA (925 °C, or 1695 °F) ROC (650 °C, or 1200 °F) (as-compacted) ROC (600 °C, or 1100 °F) and RA (815 °C, or 1500 °F) Minimum properties (MIL-T-9047)

1082 937 958

157 136 139

1130 1013 992

164 147 144

8 22 12

19 38 35

… … …

… … …

PREP PREP REP

650 650 925

820 813 924

119 118 134

896 896 1041

130 130 151

13 11 15

31 23 35

73 61 …

66 55 …

REP REP REP

925 925 950

1200 1200 1695 , 1695 1695 1740

1000

145

1062

154

14

35

…

…

REP

915

1680

945 972 882 827

137 141 128 120

993 1014 904 882

144 147 131 128

19 16 14 16

38 38 50 46

… … … …

… … … …

REP REP PREP PREP

830 760 900 900

1525 1400 1650 1650

56% forging reduction … … As-ROC 925 °C (1695 °F) RA

1131 965

164 140

1179 1020

171 148

10 15

23 43

… …

… …

PREP PREP

600 600

1110 1110

As-ROC 815 °C (1500 °F) RA

827

120

896

130

10

25

…

…

…

…

…

…

Condition(a)

Other variables

… 975 °C (1785 °F) anneal … … … … … 1300 ppm O2 1020 °C (1870 °F) anneal 315 MPa (46 ksi) 315 MPa (46 ksi) 75% rolling reduction 75% rolling reduction 75% rolling reduction 60% rolling reduction

(a) HIP, hot isostatic pressing; PSV, pulverization sous vide (powder under vacuum), French-made powder; BUS, broken-up structure; TCP, thermochemical processing; REP, rotating-electrode process; STA, solution treated and aged; PREP, plasma rotating-electrode process; ELI, extra-low interstitial; HPLT, high-pressure low-temperature compaction; RA, recrystallization annealed; L, longitudinal; T, transverse; LT, longitudinal-transverse; TL, transverse-longitudinal; VHP, vacuum hot pressing; ROC, rapid omnidirectional compaction

Fig. 7.7

Room-temperature smooth axial fatigue behavior of blended elemental and prealloyed powder metallurgy powder compacts of Ti-6Al-4V compared with wrought annealed material

Titanium: A Technical Guide Matthew J. Donachie, Jr., p55-63 DOI:10.1361/tatg2000p055

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 8

Heat Treating Why Heat Treat?

Various types of annealing treatments (e.g., single, duplex, mill, beta, and recrystallization) and solution treating and aging regimens are imposed to achieve selected mechanical properties. Stress relieving and annealing may be employed to prevent preferential chemical attack in some corrosive environments, to prevent distortion, and to condition the metal for subsequent forming and fabricating operations.

Alpha and near-alpha alloys cannot be dramatically changed by heat treatment. Stress relief and annealing are most likely for this class. The cycles for beta alloys differ significantly from those for the alpha and alpha-beta alloys. The commercial beta alloys (in reality, metastable beta alloys) not only can be stress relieved or annealed, but also can be solution treated and aged. The alpha-beta alloys are two-phase alloys, comprising both alpha and beta phases at room temperature. Phase compositions, sizes, and distributions of phases in alpha-beta alloys can be manipulated within certain limits by heat treatment. A summary of typical heat treatments for alpha-beta alloys is given in Table 8.1. The table indicates the heat treatment cycle and also the resultant microstructure expected. It is always desirable to have a positive method to track the progress of a manufacturing process. In some alloy systems, hardness is a realistic and relatively inexpensive nondestructive method to track the results of heat treatment. It should be noted that hardness testing is not recommended as a nondestructive method of checking the effectiveness of heat treatment in titanium alloys. The correla-

Response to Heat Treatment

Table 8.1

TITANIUM AND TITANIUM ALLOYS are heat treated for several reasons:

• To reduce residual stresses developed during fabrication (stress relieving)

• To produce the most acceptable combination • •

of ductility, machinability, and dimensional and structural stability, especially in alphabeta alloys (annealing) To increase strength by solution treatment and aging To optimize special properties, such as fracture toughness, fatigue strength, and hightemperature creep strength

Summary of heat treatments for alpha-beta titanium alloys

Heat treatment designation

The response of titanium and titanium alloys to heat treatment depends on the composition of the metal. The basic alpha, near-alpha, alpha-beta, or beta alloys have heat treatment responses attuned to the microstructure (phases and distribution) that can be produced in a given alloy. In simpler terms, heat treatment response is determined, to a major degree, by alloy chemistry. (Refer to Chapter 3 for background on this concept.) Not all heat treating cycles are applicable to all titanium alloys. Furthermore, different alloys serve different purposes, and heat treatments normally reflect the intended use of, purposes for, or processes (such as welding) that are to be employed on the alloy.

Duplex anneal

Solution treat and age

Beta anneal

Beta quench

Recrystallization anneal Mill anneal

tion between strength and hardness is poor. Whenever verification of a property is required, the appropriate mechanical test should be used. Alpha and Near-Alpha Alloys. Because alpha alloys undergo little in the way of phase change, microstructure of alpha alloys cannot be manipulated much by heat treatment. Consequently, high strength cannot be developed in the alpha alloys by heat treatment. Alpha and near-alpha titanium alloys can be stress relieved and annealed. Depending on the exact definition of near-alpha at issue, some of the near-alpha alloys such as Ti-8Al-1Mo-1V can be solution treated and aged in order to develop higher strengths. Alpha-Beta Alloys. By working (forging) and/or heat treating alpha-beta alloys below or above the beta transus, substantial microstructural changes can be effected. Consequently, alpha-beta alloys can be hardened by heat treatment. Solution treatment plus aging is used to produce maximum strengths in alphabeta alloys. However, a significant number of other heat treatments, including stress-relief heat treatments, are practiced for this, the largest class of titanium alloys.

Heat treatment cycle

Solution treat at 50–75 °C (90–135 °F) below Tβ(a), air cool and age for 2–8 h at 540–675 °C (1000–1250 °F) Solution treat at ~40 °C (70 °F) below Tβ, water quench(b) and age for 2–8 h at 535–675 °C (995–1250 °F) Solution treat at ~15 °C (30 °F) above Tβ, air cool and stabilize at 650–760 °C (1200–1400 °F) for 2 h Solution treat at ~15 °C (30 °F) above Tβ, water quench and temper at 650–760 °C (1200–1400 °F) for 2 h 925 °C (1700 °F) for 4 h, cool at 50 °C/h (90 °F/h) to 760 °C (1400 °F), air cool α – β hot work plus anneal at 705 °C (1300 °F) for 30 min to several hours and air cool

Microstructure

Primary α, plus Widmanstätten α – β regions Primary α, plus tempered α′ or a β – α mixture Widmanstätten α – β colony microstructure Tempered α′ Equiaxed α with β at grain–boundary triple points Incompletely recrystallized α with a small volume fraction of small β particles

(a) Tβ is the β transus temperature for the particular alloy in question. (b) In more heavily β-stabilized alloys such as Ti-6Al-2Sn-4Zr-6Mo or Ti-6Al-6V-2Sn, solution treatment is followed by air cooling. Subsequent aging causes precipitation of α phase to form an α – β mixture.

56 / Titanium: A Technical Guide Beta Alloys. In commercial (metastable) beta alloys, stress-relieving and aging treatments can be combined; also, annealing and solution treating can be identical operations. Beta Transus. The beta transus temperature for an alloy is very significant for heat treating purposes, especially when heat treatment involves heating near or above the beta transus. Table 8.2 lists the beta transus temperatures for a number of titanium alloys and some commercially pure (CP) titanium. When the heat treatment of an alloy involves heating near the beta transus, the transus temperature of each heat in a lot must be accurately determined. Titanium mill producers generally certify the beta transus temperature for each heat supplied. The beta transus of a given alloy varies from heat to heat due to small differences in chemistry, particularly in the oxygen level. Heat Treating Cycles. Because the various alloys are designed for different purposes, not all heat treating cycles are applicable to all titanium alloys. For example, the following alloys have different applications and are, consequently, heat treated in different ways:

• Alloys Ti-5Al-2Sn-2Zr-4Mo-4Cr (commonly called Ti-17) and Ti-6Al-2Sn-4Zr-6Mo are designed for strength in heavy sections.

Table 8.2 Beta transus for commercially pure titanium and selected titanium alloys Beta transus Alloy

Commercially pure Ti, 0.25 O2 max Commercially pure Ti, 0.40 O2 max α or near-α alloys Ti-5Al-2.5Sn Ti-8Al-1Mo-1V Ti-2.5Cu (IMI 230) Ti-6Al-2Sn-4Zr-2Mo Ti-6Al-5Zr-0.5Mo-0.2Si (IMI 685) Ti-5.5Al-3.5Sn-3Zr-1Nb-0.3Mo0.3Si (IMI 829) Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo0.3Si (IMI 834) Ti-6Al-2Cb-1Ta-0.8Mo Ti-0.3Mo-0.8Ni (Ti code 12) α-β alloys Ti-6Al-4V Ti-6Al-7Nb (IMI 367) Ti-6Al-6V-2Sn (Cu + Fe) Ti-3Al-2.5V Ti-6Al-2Sn-4Zr-6Mo Ti-4Al-4Mo-2Sn-0.5Si (IMI 550) Ti-4Al-4Mo-4Sn-0.5Si (IMI 551) Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17) Ti-7Al-4Mo Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.25Si Ti-8Mn β or near-β alloys Ti-13V-11Cr-3Al Ti-11.5Mo-6Zr-4.5Sn (Beta III) Ti-3Al-8V-6Cr-4Zr-4Mo (Beta C) Ti-10V-2Fe-3Al Ti-15V-3Al-3Cr-3Sn (a) ±20. (b) ±30. (c) ±35. (d) ±50

°C, ±15

°F, ±25

910 945

1675 1735

1050 1040 895 995 1020 1015

1925 1900 1645 1820 1870 1860

1045

1915

1015 880

1860 1615

1000(a) 1010 945 935 940 975 1050 900 1000 970 800(c)

1830(b) 1850 1735 1715 1720 1785 1920 1650 1840 1780 1475(d)

720 760 795 805 760

1330 1400 1460 1480 1400

• Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-5Zr-0.5Mo• • •

0.25Sn are designed for creep resistance. Ti-6Al-2Cb-1Ta-1Mo and Ti-6Al-4V-ELI are designed to resist stress corrosion in aqueous salt solutions and to have high fracture toughness. Ti-5Al-2.5Sn and Ti-2.5Cu are designed for weldability. Ti-6Al-6V-2Sn, Ti-6Al-4V, and Ti-10V-2Fe-3Al are designed for high strength at lowto-moderate temperatures.

Special Considerations in Heat Treatment Any heat treatment at temperatures above about 427 °C (800 °F) must provide the titanium or titanium alloy with an atmospheric protection that prevents pickup of oxygen or nitrogen and formation of alpha case. The protection also obviates the possibility of undesirable scale formation. (Contamination during heat treatment is discussed later in this Chapter.) A few key considerations in the heat treatment of titanium and its alloys (practices that should be followed or avoided) are:

• Clean components, fixtures, and furnaces • • •

prior to heat treatment. (Do not use ordinary tap water in cleaning of titanium components.) Take care to prevent temperatures from exceeding the beta transus unless specified. Remove alpha case after all heat treating is completed. Provide sufficient stock for post-heat treatment metal removal requirements, such as contaminated metal removal.

Stress Relieving Stress-relief heat treatments probably are the most common heat treatments given to the broad classes of titanium and titanium alloys. Titanium and its alloys can be stress relieved without adversely affecting strength or ductility. Stress-relief treatments decrease the undesirable residual stresses that result from:

• Nonuniform hot forging deformation • Nonuniform cold forming and straightening • Asymmetric machining of plate (hogouts) or forgings

• Welding of wrought, cast, or powder metallurgy (P/M) articles and cooling of castings

Removal of such stresses helps maintain shape stability and eliminates unfavorable conditions such as the loss of compressive yield strength, commonly known as the Bauschinger effect, which can be particularly noticeable in titanium alloys. When symmetrical shapes are machined in the annealed condition, employing modest cuts

and uniform stock removal, it has been found that stress-relief annealing may not be required. However, the greater the depth of cut and/or the more nonuniform the cut, the more likely it is that stress relief will be required either to complete the machining and fabrication cycle successfully or to ensure maximum service life. Alternately, separate stress relieving may be omitted when the manufacturing sequence can be adjusted to employ annealing or hardening as the stress-relief process. For example, forging stresses can be relieved by annealing prior to machining. Large, thin rings have been effectively processed with minimum distortion by rough machining in the annealed state. This is followed by solution treating, quenching, partial aging, finish machining, and final aging. Partial aging relieves quenching stresses, and final aging relieves stresses developed during finish machining. Adjustments of Time and Temperature. Combinations of time and temperature that are used for stress relieving titanium and titanium alloys are given in Table 8.3. More than one combination in both time and temperature can yield satisfactory results. The higher temperatures usually are used with shorter times and the lower temperatures with longer times for most effective stress relief. The effects of stress relieving Ti-6Al-4V at five temperatures ranging from 260 to 620 °C (500–1150 °F) for periods of time ranging from five minutes to 50 hours are illustrated in Fig. 8.1. Care should be taken, during stress relief of solution treated and aged titanium alloys, to prevent overaging, which would cause lower strength. This usually involves selection of a time-temperature combination that provides partial stress relief. The parts, in bulk or in fixtures, may be charged directly into a furnace operating at the stress-relief temperature. If a part is mounted in a massive fixture, a thermocouple should be attached to the largest part of the fixture. Cooling Rate Effects. Cooling rate from the stress-relief temperature is not critical for titanium alloys. Uniformity of cooling, however, is critical. This is particularly true in the temperature range from 480 to 315 °C (900–600 °F). Moreover, oil or water quenching should not be used to accelerate cooling. Such quenching, commonly used in heat treating after solution treatment, can induce residual stress by unequal cooling. Furnace or air cooling is acceptable. Metallurgical Responses. The metallurgical response of the alloy involved plays a major role in the selection of stress-relief cycles. To reduce stresses in a reasonable time, the maximum temperature consistent with limited change in microstructure is used. Stress relief involves holding a part at a temperature sufficiently high to relieve stresses without causing an undesirable amount of precipitation or strain aging in alpha-beta and beta alloys, or without producing undesirable recrystallization in singlephase alpha alloys that rely on cold work for strength.

Heat Treating / 57 Table 8.3

Selected stress-relief heat treatments for titanium and titanium alloys Temperature

Alloy

Commercially pure titanium (all grades)

°C

°F

480–595

900–1100

Time, h 1

4 –4

540–650 595–705 400–600 595–705 530–570 610–640 625–750 595–650 480–595

1000–1200 1100–1300 750–1110 1100–1300 980–1050 1130–1190 1160–1380 1100–1200 900–1100

1

4 –4

1

4 –4

24–48 1–3 1–3 1 –2 4 1 –4 4

480–650 500–600 480–650 540–650 595–705 600–700 600–700 480–650 480–705 480–650 480–595

900–1200 930–1110 900–1200 1000–1200 1100–1300 1110–1290 1110–1290 900–1200 900–1300 900–1200 900–1100

1–4 1–4 1–4 1 –2 4 1 –4 4 2–4 2–4 1–4 1–8 1–4 1 –2 4

705–730 720–730 705–760 675–705 790–815

1300–1350 1325–1350 1300–1400 1250–1300 1450–1500

α or near-α titanium alloys Ti-5Al-2.5Sn Ti-8Al-1Mo-1V Ti-2.5Cu (IMI 230) Ti-6Al-2Sn-4Zr-2Mo Ti-6Al-5Zr-0.5Mo-0.2Si (IMI 685) Ti-5.5Al-3.5Sn-3Zr-1Nb-0.3Mo-0.3Si (IMI 829) Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.3Si (IMI 834) Ti-6Al-2Cb-1Ta-0.8Mo Ti-0.3Mo-0.8Ni (Ti Code 12)

1

2–24

1

4 –4

α-β titanium alloys Ti-6Al-4V Ti-6Al-7Nb (IMI 367) Ti-6Al-6V-2Sn (Cu + Fe) Ti-3Al-2.5V Ti-6Al-2Sn-4Zr-6Mo Ti-4Al-4Mo-2Sn-0.5Si (IMI 550) Ti-4Al-4Mo-4Sn-0.5Si (IMI 551) Ti-5Al-2Sn-4Mo-2Zr-4Cr (Ti-17) Ti-7Al-4Mo Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.25Si Ti-8Mn β or near-β titanium alloys Ti-13V-11Cr-3Al Ti-11.5Mo-6Zr-4.5Sn (Beta III) Ti-3Al-8V-6Cr-4Zr-4Mo (Beta C) Ti-10V-2Fe-3Al Ti-15V-3Al-3Cr-3Sn

1

1 2– 4 1 2– 4 1 –1 6 4 1 –2 2 1 –1 2 4 1

Parts can be cooled from stress relief by either air cooling or slow cooling.

Some alloys are heat treated to enhance strength. Alloys such as the beta alloys and the more highly alloyed alpha-beta compositions rely on microstructural control to optimize strength properties. Consequently, they would best be stress relieved using a thermal exposure that is compatible with annealing, solution treating, stabilization, or aging processes. Stress-relief heat treatment is not used to control microstructure except where it is performed in conjunction with other thermal treatments, as previously suggested. Assessment of Stress-Relief Efficiency. There are no nondestructive testing methods that can measure the efficiency of a stress-relief

Fig. 8.1

cycle other than direct measurement of residual stresses by x-ray diffraction. No significant changes in microstructure due to stress-relief heat treatments can be detected by optical microscopy. While x-ray stress measurement is effective in the determination of the degree of stress reduction, very limited data are available. Most of these data were generated in the first two decades of the commercial development of titanium. The residual stress-versus-time curve shapes at each stress-relief temperature are likely to differ for every alloy and should be a function of prior processing. Nevertheless, with limited data available on alloys, relative stress reduction as a function of time at temperature is

Relationship between time and amount of residual stress relief at various stress-relief anneal temperatures for Ti-6Al-4V alpha-beta alloy

routinely treated as an invariant function, and the relative stress curves are applied to alloys for which actual measurements are limited or nonexistent. Stress Relieving of Weldments. Simple weldments of CP titanium often are used without stress relief. Titanium alloy weldments and complex weldments of CP titanium are routinely given a stress-relief heat treatment. Complex weldments have multiple welds in complex configurations. These configurations can involve combinations of machine and manual welding. In order to stress relieve complex weldments of alpha or alpha-beta alloys, the temperatures used should be near the high ends of the ranges given in Table 8.3. In complex weldments made with CP titanium, Ti-5Al2.5Sn alloy, or Ti-6Al-4V alloy, more than 70% of the residual stress is relieved during the first hour at temperature.

Process Annealing Annealing is a generic term and may be applied differently by different producers. Solution treatment is frequently considered an annealing process, as is mill annealing. Even stress-relief heat treatment frequently is called stress-relief annealing. Techniques that serve primarily to increase toughness, ductility at room temperature, dimensional and thermal stability, and, sometimes, creep resistance are considered as process annealing in this Chapter. Occasionally in the Chapter, the term process annealing will be shortened to annealing. Annealing Treatments. Common treatments identified as annealing are:

• • • •

Mill annealing Duplex annealing Recrystallization annealing Beta annealing

Either air or furnace cooling can be used in cooling from higher-temperature annealing; however, the two methods can result in different levels of tensile properties. For example, air cooling of Ti-6Al-6V-2Sn from the mill annealing temperature results in lower tensile strength than that obtained by furnace cooling. If distortion is a problem, the cooling rate should be uniform down to 315 °C (600 °F). Because process annealing treatments usually are less closely controlled, more property variability, or “scatter,” is found in annealed titanium alloys than in solution treated and aged alloys. However, many titanium alloys are placed in service in the annealed state. Because improvement in one or more properties generally is obtained at the expense of some other property, the annealing cycle should be selected according to the objective of the treatment. Duplex annealing is one example of multiple anneals that sometimes are performed on titanium alloys. Triplex annealing also has been practiced. Such treatments frequently are used

58 / Titanium: A Technical Guide Alloy Phase Stability. In beta and alpha-beta titanium alloys, thermal instability is a function of beta-phase transformations. In alpha-beta alloys during cooling from the annealing temperature, or in isothermal exposure of beta alloys, beta can transform to undesirable phases. Beta can, under certain conditions and in certain alloys, form the (brittle) intermediate phase, omega. Beta alloy chemistries are controlled to prevent omega formation and alpha-beta alloys are given a stabilization annealing treatment. This treatment is designed to produce a stable beta phase capable of resisting further transformation when exposed to elevated temperatures in service. In the case of alloys that are solution treated and then aged, the aging treatment can serve, in some cases, as a stabilization heat treatment. Alpha-beta alloys that are lean in beta, such as Ti-6Al-4V, can be air cooled from the annealing temperature without impairing their stability. Furnace (slow) cooling, however, may promote formation of Ti3Al, a reaction that can degrade resistance to stress corrosion. To obtain maximum stability in the near-alpha alloys Ti-8Al-1Mo-1V and Ti-6Al-2Sn4Zr-2Mo, a duplex annealing treatment is employed. This treatment begins with solution annealing at temperatures high in the alpha-beta range, usually 25 to 35 °C (50–100 °F) below the beta transus for Ti-8Al-1Mo-1V alloy and 15 to 25 °C (25–50 °F) below the beta transus for a Ti-6Al-2Sn-4Zr-2Mo alloy. Forgings are held for one hour (nominal) and then air or fan cooled, depending on section size. This treat-

in the context of solution treatment and aging. Duplex heat treatment usually does not occur in the area of process annealing. Mill annealing is a general-purpose treatment given to all mill products. It is not a full anneal and can leave traces of cold or warm working in the microstructures of heavily worked products (particularly sheet). Recrystallization annealing and beta annealing treatments are used to improve toughness. In recrystallization annealing, the alloy is heated into the upper end of the alpha-beta range, held for a time, and then very slowly cooled. Recrystallization annealing has replaced beta annealing for fracture-critical airframe components. Beta annealing is done at temperatures above the beta transus of the alloy being annealed. To prevent excessive grain growth, the temperature for beta annealing should be only slightly higher than the beta transus. Annealing times are dependent on section thickness and should be long enough to permit complete transformation of the component to beta when heated. Time at temperature after transformation to beta should be held to a minimum to control grain growth of the beta phase. Beta annealing can be followed by an air cool from the annealing temperatures. However, larger sections may need to be fan cooled or even water quenched to prevent the formation of a detrimental alpha phase at grain boundaries. Some representative annealing treatments for titanium and titanium alloys are given in Table 8.4.

Table 8.4

Selected annealing treatments for titanium and titanium alloys Temperature

Alloy

Time, h

Cooling method

°C

°F

Commercially pure Ti (all grades)

650–760

1200–1400

0.10–2

Air

α or near-α titanium alloys Ti-5Al-2.5Sn Ti-8Al-1Mo-1V Ti-2.5Cu (IMI 230) Ti-6Al-2Sn-4Zr-2Mo Ti-6Al-5Zr-0.5Mo-0.2Si (IMI 685) Ti-5.5Al-3.5Sn-3Zr-1Nb-0.3Mo-0.3Si (IMI 829) Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.3Si (IMI 834) Ti-6Al-2Cb-1Ta-0.8Mo

720–845 790(a) 780–800 900(b) (c) (c) (c) 790–900

1325–1550 1450(a) 1450–1470 1650(b) (c) (c) (c) 1450–1650

0.167–4 1–8 0.5–1 0.5–1 … … … 1–4

Air Air or furnace Air Air … … … Air

α-β titanium alloys Ti-6Al-4V Ti-6Al-7Nb (IMI 367) Ti-6Al-6V-2Sn (Cu + Fe) Ti-3Al-2.5V Ti-6Al-2Sn-4Zr-6Mo Ti-4Al-4Mo-2Sn-0.5Si (IMI 550) Ti-4Al-4Mo-4Sn-0.5Si (IMI 551) Ti-5Al-2Sn-4Mo-2Zr-4Cr (Ti-17) Ti-7Al-4Mo Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.25Si Ti-8Mn

705–790 700 705–815 650–760 (c) (c) (c) (c) 705–790 705–815 650–760

1300–1450 1300 1300–1500 1200–1400 (c) (c) (c) (c) 1300–1450 1300–1500 1200–1400

1–4 1–2 0.75–4 0.5–2 … … … … 1–8 1–2 0.5–1

Air or furnace Air Air or furnace Air … … … … Air Air (d)

β or near-β titanium alloys Ti-13V-11Cr-3Al Ti-11.5Mo-6Zr-4.5Sn (Beta III) Ti-3Al-8V-6Cr-4Zr-4Mo (Beta C) Ti-10V-2Fe-3Al Ti-15V-3Al-3Cr-3Sn

705–790 690–760 790–815 (c) 790–815

1300–1450 1275–1400 1450–1500 (c) 1450–1500

0.167–1 0.167–1 0.25–1 … 0.0833–0.25

Air or water Air or water Air or water … Air

(a) For sheet and plate, follow by 0.25 h at 790 °C (1450 °F), then air cool. (b) For sheet, follow by 0.25 h at 790 °C (1450 °F), then air cool (plus 2 h at 595 °C, or 1100 °F, then air cool, in certain applications). For plate, follow by 8 h at 595 °C (1100 °F), then air cool. (c) Not normally supplied or used in annealed condition. (d) Furnace or slow cool to 540 °C (1000 °F), then air cool.

ment is followed by stabilization annealing for eight hours at 595 °C (1100 °F). Final annealing temperature should be at least 56 °C (100 °F) above the anticipated service temperature so that no further alloy microstructural changes will occur during service operation. Maximum creep resistance can be developed in Ti-6Al2Sn-4Zr-2Mo by beta annealing or beta processing (and by adding silicon to produce Ti-6Al-2Sn-4Zr-2Mo+Si). Straightening, Sizing, and Flattening. Straightening, sizing, and flattening of titanium alloys are often necessary to meet dimensional requirements because it can be difficult to prevent distortion of close-tolerance thin sections during annealing. Because titanium alloys have excessive springback, the straightening of bar to close tolerances and the flattening of sheet present major problems for titanium producers and fabricators. Straightening, sizing, and flattening can be conducted independently of other related processes or can be combined with annealing (or stress relief) by use of appropriate fixtures. Unlike aluminum alloys, titanium alloys are not easily straightened when cold, as explained previously. (See the section “Forming” in Chapter 5.) Because of springback and resistance to straightening at room temperature, it is necessary to employ elevated-temperature forming. Therefore, titanium alloys are straightened primarily by creep straightening processes. Creep straightening uses the concept that at annealing temperatures, many titanium alloys have low creep resistance. The creep resistance can be sufficiently low enough to permit the alloys to be straightened during annealing. With proper fixturing and, in some instances, with judicious weighting, sheet metal fabrications and thin complex forgings have been straightened with satisfactory results. Again, uniform cooling to below 315 °C (600 °F) after straightening can improve results. Creep flattening consists of heating titanium sheet between two clean, flat sheets of steel in a furnace containing an oxidizing or inert atmosphere. Various jigs and processing techniques have been proposed for annealing titanium in a manner that yields a flat product. Creep flattening and vacuum creep flattening are two such techniques. Vacuum creep flattening is used to produce stress-free flat plate for subsequent machining. The plate is placed on a large, flat, ceramic bed that has integral electric heating elements. Insulation is placed on top of the plate, and a plastic sheet is sealed to the frame. The bed is slowly heated to the annealing temperature while a vacuum is pulled under the plastic. Atmospheric pressure is used to creep flatten the plate.

Solution Annealing (Treatment) and Aging Maximum strength levels are achieved in titanium alloys by solution annealing (commonly

Heat Treating / 59 called “solution heat treating”) followed by aging. A wide range of strength levels can be obtained in alpha-beta or beta alloys by these processes. With the exception of alloys such as Ti-2.5Cu, the origin of heat treating responses of titanium alloys to solution treatment and aging lies in the instability of the high-temperature beta phase at lower temperatures. Solution treatment and aging does not mean the same thing in titanium as it does in traditional age hardening systems, such as aluminum or nickel superalloys. Ti-2.5Cu is a rare exception for titanium alloys in that it produces precipitates from a supersaturated alpha phase formed when it is quenched from high-temperature solutioning. At lower temperatures, after solution treatment, Ti2Cu compound precipitates with the formation of zones (as in aluminum alloys) that lead to increased lower-temperature strength. Zones occur after appropriate times of holding at an appropriate aging temperature. Ti-2.5Cu alloy, however, does not produce the precipitate particles, such as gamma prime, that characterize the truly high-temperature alloys formed in nickel superalloys. No titanium alloy of conventional composition has been found to be truly age hardenable. However, it should be noted that the addition of silicon to titanium alloys produces improved high-temperature strength, presumably by for-

Table 8.5

mation of a silicide phase during the solution and aging processes customarily used for titanium near-alpha and alpha-beta alloys. Solution treatment and aging (stabilization) usually, but not always, follow working operations to generate optimum and mechanical properties. Heating an alpha-beta alloy to the solution treating temperature produces a higher ratio of beta phase to alpha phase. This partitioning of phases is maintained by quenching; on subsequent aging, decomposition of the unstable beta phase and of the martensite (if any) occurs, providing high strength. Commercial beta alloys, generally supplied in the solution-treated condition, need only be aged to achieve properties. Solution treating of titanium alloys normally involves heating to temperatures either slightly above or slightly below the beta transus of the alloy. If the beta transus is exceeded when an alpha-beta titanium alloy is solution heat treated, tensile properties (especially ductility) are reduced and cannot be fully restored by subsequent thermal treatment. Because alpha-beta solution treating involves heating to temperatures only slightly below the beta transus, proper control of temperature is essential. As noted, Table 8.2 supplies the beta transus temperatures for some commercial alloys. Furnace Conditions. After being cleaned, titanium components should be loaded into fix-

Some solution treating and aging regimens for titanium alloys Solution temperature

Alloy

α or near-α alloys Ti-8Al-1Mo-1V Ti-2.5Cu (IMI 230) Ti-6Al-2Sn-4Zr-2Mo Ti-6Al-5Zr-0.5Mo-0.2Si (IMI 685) Ti-5.5Al-3.5Sn-3Zr-1Nb0.3Mo-0.3Si (IMI 829) Ti-5.8Al-4Sn-3.5Zr-0.7Nb0.5Mo-0.3Si (IMI 834) α-β alloys Ti-6Al-4V Ti-6Al-6V-2Sn (Cu + Fe) Ti-6Al-2Sn-4Zr-6Mo Ti-4Al-4Mo-2Sn-0.5Si (IMI 550) Ti-4Al-4Mo-4Sn-0.5Si (IMI 551) Ti-5Al-2Sn-2Zr-4Mo-4Cr Ti-6Al-2Sn-2Zr-2Mo-2Cr0.25Si β or near-β alloys Ti-13V-11Cr-3Al Ti-11.5Mo-6Zr-4.5Sn (Beta III) Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) Ti-10V-2Fe-3Al Ti-15V-3Al-3Cr-3Sn

°C

°F

980–1010(a) 1800–1850(a) 795–815 1465–1495

Aging temperature

Solution time, h

Cooling rate

°C

°F

Aging time, h

1

565–595 390–410 870–905 595 540–560

1050–1100 ... 735–770 8–24 (step 1) 8 (step 2) 1100 8 1005–1040 24

955–980 1040–1060

1750–1800 1905–1940

1

2–1

Oil or water Air or water 465–485 Air Oil

1040–1060

1905–1940

1

2–1

Air or oil

615–635

1140–1175

2

2

Oil

625

1155

2

955–970(c)(d) 1750–1775(c)(d) 955–970 1750–1775 885–910 1625–1675 845–890 1550–1650 890–910 1635–1670

1 1 1 1 1 –1 2

Water Water Water Air Air

480–595 705–760 480–595 580–605 490–510

900–1100 1300–1400 900–1100 1075–1125 915–950

4–8 2–4 4–8 4–8 24

890–910

1635–1670

1

Air

490–510

915–950

24

845–870 870–925

1550–1600 1600–1700

Air Water

580–605 480–595

1075–1125 900–1100

4–8 4–8

1020(b)

1

2–1

1

1870(b)

2–1

1 1

tures or racks that permit free access to the heating and quenching media. Thick and thin components of the same alloy may be solution treated together, but the time at temperature (soaking time) is determined by the thickest section. To determine the required temperature for most alloys, the rule is 20 to 30 minutes for every 25 mm (1 in.) of thickness, followed by the required soak time. Time-temperature combinations for solution treating are given in Table 8.5. A load can be charged directly into a furnace operating at the solution treating temperature. Although preheating is not essential, it can be used to minimize distortion of complex parts. Beta Alloy Solution Treating. Solution treating temperatures for beta alloys can be above the beta transus. Beta alloys normally are obtained from producers in the solution-treated condition. If reheating is required, soak times should be only as long as necessary to obtain complete solutioning as grain growth can proceed rapidly under these conditions (because no second phase is present). For near-beta alloys, solution heat treatment may have to be carried out below the beta transus (alpha-beta anneal). Such a solution-treated product contains globular alpha plus retained beta. The final aged product would contain a bimodal alpha distribution (primary alpha plus alpha from aging). Alpha-Beta Alloy Solution Treating. Selection of a solution treatment for alpha-beta alloys is made after consideration of the combination of mechanical properties desired from the aging treatment. Selection usually is based on practical considerations, such as the desired level of tensile properties and the amount of ductility to be obtained after aging. A change in the solution treating temperature of alpha-beta alloys alters the amount of beta phase and, consequently, changes the response to aging (Table 8.6.). To obtain high strength with adequate ductility, it generally is necessary to solution treat at a temperature high in the alpha-beta field, normally 25 to 85 °C (50–150 °F) below the beta transus of the alloy. If higher fracture toughness or improved resistance to stress corrosion is required, beta annealing or beta solution Table 8.6 Effect of solution treating temperature on tensile properties of Ti-6Al-4V barstock Room-temperature tensile properties(a) Solution-treating temperature

1

775–800 690–790

1425–1475 1275–1450

815–925

1500–1700

1

Water

760–780 790–815

1400–1435 1450–1500

1 1

Water Air

1

2–1 8–1

4

Air or water 425–480 Air or water 480–595

800–900 900–1100

4–100 8–32

455–540

850–1000

8–24

495–525 510–595

925–975 950–1100

8 8–24

(a) For certain products use solution temperature of 890 °C (1650 °F) for 1 h. then air cool or faster. (b) Temperature should be selected from transus approach curve to give desired α content. (c) For thin plate or sheet, solution temperature can be used down to 890 °C (1650 °F) for 6 to 30 min; then water quench. (d) This treatment is used to develop maximum tensile properties in this alloy.

Tensile strength

Yield strength (b)

Elongation in 4D(c),

°C

°F

MPa

ksi

MPa

ksi

%

845 870 900 925 940

1550 1600 1650 1700 1725

1025 1060 1095 1110 1140

149 154 159 161 165

980 985 995 1000 1055

142 143 144 145 153

18 17 16 16 16

(a) Properties determined on 13 mm (1 2-in.) bar after solution treating, quenching, and aging. Aging treatment 8 h at 480 °C (900 °F), air cool. (b) At 0.2% offset. (c) D, specimen diam

60 / Titanium: A Technical Guide treating may be desirable. However, heat treating alpha-beta alloys in the beta range causes considerable loss in ductility, as noted previously. These alloys are usually solution treated below the beta transus to obtain an optimum balance of ductility, fracture toughness, creep and, stress rupture resistance. (See Chapter 12 for more information on mechanical properties, their dependence on microstructure, and the tradeoffs possible.) Near-Alpha Alloy Solution Treating. As in the case for alpha-beta alloys, solution treatment above the beta transus provides optimum creep resistance at the expense of reduced ductility and fatigue strength. To obtain the best combination of creep and fatigue strength, the solution temperature must be very close to, but still below, the beta transus. Only about 10 to 15% of primary (untransformed) alpha should persist at the solution treating temperature. The necessity for a close approach to the beta transus poses production concerns. In some alloys, these concerns can be overcome by alloy composition modifications to produce a flattened beta approach curve. Alloy IMI 834 uses carbon additions to achieve the desired purpose. Cooling after Solution Treating. The cooling rate from the solution treating temperature has an important effect on strength of alpha-beta titanium alloys. Appreciable diffusion can occur during cooling if the rate is too low. This diffusion will change the phase chemistry and/or ratios, and subsequent decomposition of the altered beta phase during aging may not provide effective strengthening. For alloys that have a relatively high beta stabilizer content and for products that have a small section size, air or fan cooling may be adequate. Where allowed by specified mechanical properties, such slower cooling is preferred because it minimizes distortion. Beta alloys generally are air cooled from the solution treating temperature. Rapid cooling (quenching) is required after most alpha-beta alloy solution treatment. Water, 5% brine, or a caustic soda solution is preferred for quenching alpha-beta alloys. Maximum response to subsequent aging is achieved when decomposition of the beta phase present at the end of solution treating is minimized. The above quench agents provide the cooling rates necessary to prevent decomposition of beta. The need for rapid quenching is emphasized by requirements of short quench delay times. Some alpha-beta alloys can only tolerate a maximum delay of seven seconds, depending on the mass of the sections being heat treated. The more highly beta-stabilized alpha-beta alloys can tolerate quench delay times of up to 20 seconds. The effect of quench delays on Ti-6Al-4V alpha-beta alloy bar is shown in Fig. 8.2. When a Ti-6Al-4V part section thickness exceeds 75 mm (3 in.), it is difficult to cool the center of the part fast enough to maintain an unstable beta phase for later transformation during aging. For this reason, the solution treated and aged properties of Ti-6Al-4V parts with large section sizes usually are similar to the

properties of process-annealed material. Alloys such as Ti-6Al-2Sn-4Zr-6Mo and Ti-5Al-2Sn2Zr-4Mo-4Cr in which fan air cooling develops good strength through 100 mm (4 in.) sections are less sensitive to delayed quenching. It is very important, therefore, to recognize that section size influences effectiveness of quenching and, in turn, the response of an alloy to aging. It is handy to remember these guidelines:

The property levels of alpha-beta alloys that are not highly stabilized with beta formers vary greatly with oxygen content. The precise strength values for Ti-6Al-4V shown in Table 8.7 and Fig. 8.3 would be typical of alloys with oxygen contents between about 0.27 and 0.20% A lower oxygen content tends to result in strength levels below those shown, particularly for parts with smaller section sizes.

• The amount and type of beta stabilizer in the •

alloy determine depth of hardening or strengthening. Unless an alloy is highly alloyed with beta stabilizers, thick sections exhibit lower tensile properties.

The practical significance of section size for some titanium alloys is shown in Table 8.7. The effects of quenched section size on the tensile properties of Ti-6Al-4V alloy are illustrated in Fig. 8.3.

Fig. 8.2

Aging The final step in heat treating titanium alloys to high strength consists of reheating to an aging temperature between 425 and 650 °C (800 and 1200 °F). Again, the reader is cautioned that terminology such as aging is not equivalent to the aging process in aluminum and nickel alloys. In titanium alpha-beta or beta alloys, aging causes decomposition of the supersaturated

Effect of quench delay on tensile properties of Ti-6Al-4V alpha-beta alloy. Bar, 13 mm ( 12 in.) in diameter, was solution treated 1 h at 955 °C (1750 °F), water quenched, aged 6 h at 480 °C (900 °F), and air cooled.

Table 8.7 Effect of section size on tensile strength of some solution tested and aged titanium alloys Tensile strength of square bar in section size of: 13 mm (1 2 in.)

25 mm (1 in.)

50 mm (2 in.)

75 mm (3 in.)

100 mm (4 in.)

150 mm (6 in.)

Alloy

MPa

ksi

MPa

ksi

MPa

ksi

MPa

ksi

MPa

ksi

MPa

ksi

Ti-6Al-4V Ti-6Al-6V-2Sn(Cu + Fe) Ti-6Al-2Sn-4Zr-6Mo Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17) Ti-10V-2Fe-3Al Ti-13V-11Cr-3Al Ti-11.5Mo-6Zr-4.5Sn (Beta III) Ti-3Al-8V-6Cr-4Zr-4Mo (Beta C)

1105 1205 1170 1170 1240 1310 1310 1310

160 175 170 170 180 190 190 190

1070 1205 1170 1170 1240 1310 1310 1310

155 175 170 170 180 190 190 190

1000 1070 1170 1170 1240 1310 1310 1240

145 155 170 170 180 190 190 180

930 1035 1140 1105 1240 1310 1310 1240

135 150 165 160 180 190 190 180

… … 1105 1105 1170 1310 1310 1170

… … 160 160 170 190 190 170

… … … 1105 1170 1310 … 1170

… … … 160 170 190 … 170

Heat Treating / 61 beta phase retained on quenching and the transformation of any martensite (in alpha-beta alloys) to alpha. As noted, a summary of aging times and temperatures is presented in Table 8.5. The time-temperature combination selected for a specific alloy composition depends on required strength. Aging above the standard aging temperature for an alloy, yet still several hundred degrees below the beta transus temperature, results in overaging. The transformation proceeds much farther than in normal aging of titanium. This condition produces the solution-treated and overaged (STOA) condition. It sometimes is used to obtain modest increases in strength while maintaining satisfactory toughness and dimensional stability. STOA of Ti-6Al-4V alloy can be accomplished by the following cycle: heat one hour at 955 °C (1750 °F), water quench, hold two hours at 705 °C (1300 °F), and air cool. The advantages of this STOA cycle on the alloy are improved notch strength, improved fracture toughness, and creep strength similar to that obtained by regular annealing. Heat treatment of alpha-beta alloys for high strength frequently involves a series of compromises and modifications, depending on the type of service and on special properties that are required, such as ductility and suitability for fabrication. This has become especially true where fracture toughness is important in design and where strength is lowered to improve design life. The aged condition is not necessarily one of equilibrium in titanium alloys. However, proper aging produces high strength with adequate ductility and metallurgical stability.

Fig. 8.3

It has long been known that beta phase (in highly beta-stabilized alpha-beta alloys or in beta alloys) can form omega phase, a metastable transition phase. During aging of some highly beta-stabilized alpha-beta alloys, beta transforms first to omega phase before alpha phase is produced. Retained omega phase, which produces brittleness unacceptable in alloys heat treated for service, can be avoided by severe quenching and rapid reheating to aging temperatures above 425 °C (800 °F). Because a coarse alpha phase forms, however, this treatment might not produce optimum strength properties. An aging practice that ensures that aging time and temperature are adequate to carry any omega-alpha reaction to completion usually is employed. Aging above 425 °C (800 °F) generally is adequate to complete the reaction. Omega phase formation is not a problem in contemporary titanium alloy aging. The metastable beta alloys usually do not require solution treatment. Final hot working, followed by air cooling, leaves these alloys in a condition comparable to a solution-treated state. In some instances, however, solution treating at 790 °C (1450 °F) has produced better uniformity of properties after aging. Short aging times can be used on cold-worked material to produce a significant increase in strength over that obtained by cold working. Aging for longer times on hot-worked or solution-treated beta alloys may provide higher strengths but decrease ductility and fracture toughness in alloys containing chromium when titanium-chromium compounds are formed. The use of beta alloys at service temperatures

Effect of section size on tensile properties of Ti-6Al-4V alpha-beta alloy

above 315 °C (600 °F) for prolonged periods is not recommended because the loss of ductility caused by metallurgical instability is progressive.

Atmospheres, Contamination, and Post-Heat Treatment Processing Titanium reacts with the oxygen, water, and carbon dioxide normally found in the oxidizing heat treating atmospheres. It also reacts with hydrogen formed by decomposition of water vapor. Unless the heat treatment is performed in a vacuum furnace or in an inert atmosphere, and unless surface cleanliness is maintained, there is a direct effect on the properties of titanium. While properties can be recovered by vacuum heat treatment (hydrogen removal) or stock removal (of oxygen/nitrogen enriched surface), depending on the situation, it is more efficient to prevent or to minimize interactions through the surface where possible. Even when, for example, coatings are used in forging to protect as well as to lubricate a billet, some oxygen/nitrogen pickup occurs, and stock removal is required. In some cases, surface contamination can render a piece unfit for use. Pre-Heat Treatment Precautions. Before being subjected to any thermal treatment, titanium components should be cleaned and dried. Caution must be taken not to use ordinary tap water for cleaning such components. Oil, fingerprints, grease, paint, and other foreign matter should be removed from all surfaces. Cleaning is required because the chemical reactivity of titanium at elevated temperatures can lead to its contamination or embrittlement and can increase its susceptibility to stress corrosion. After cleaning, parts should be handled with clean gloves to prevent recontamination. If a component is to be sized, straightened, or heat treated in a fixture, the fixture also should be free of any foreign matter and loosely adhering scale. Oxygen and Alpha Case. Oxygen and nitrogen react with the titanium at the surface of the metal. Oxygen (or nitrogen) pickup during heat treatment results in a surface structure composed predominantly of alpha phase (oxygen and nitrogen are alpha stabilizers). The interstitial-enriched layer is commonly called “alpha case.” (See Fig. 11.1 for a microsection showing alpha case.) Of the two alpha case formers, oxygen is the more potent; oxygen is absorbed at a much greater rate than nitrogen. Alpha case is detrimental because of the brittle nature of the oxygen-enriched alpha structure. This layer must be removed before the component is put into service; it can be removed by machining, but certain machining operations may result in excessive tool wear because the layer is very abrasive to either carbide or high-speed steel machine tools. The standard practice is to remove alpha case by other mechanical methods or by chemical methods, or by both. At 955 °C (1750 °F), the alpha struc-

62 / Titanium: A Technical Guide

Fig. 8.4

Scaling rates of titanium and some titanium alloys in air at various temperatures

ture can extend 0.2 to 0.3 mm (0.008–0.012 in.) below the surface. Titanium is chemically active at elevated temperatures and will oxidize in air, resulting in the formation of a scale. However, oxidation is not of primary concern in heat treating of titanium, although it may be a problem in sheet forming operations. An antioxidant spray coating can be applied beforehand to clean sheet metal pans in order to minimize oxygen pickup during heat treatment. Such coatings work effectively at temperatures up to about 760 °C (1400 °F), but such use does not fully eliminate the need for removing the surface structure after heat treating. Titanium alloy oxidation rates vary considerably. A comparison of the scaling rates of CP titanium and titanium alloys in air at temperatures from 650 to 980 °C (1200–1800 °F) is given in Fig. 8.4. Table 8.8 indicates the measurable thickness of oxide formed on CP titanium after one-half hour at various temperatures in air. Oxidation rates of commercial titanium alloys vary. Table 8.9 can be used to determine how much metal must be removed from a titanium alloy surface to return to unaffected base metal. Temperature and total time of exposure to an oxidizing atmosphere must be known. One method used to check for the complete removal of alpha case formed by oxygen pickup is to etch the component in an ammonium bifluoride solution. Etching characteristics of oxygen-enriched case differ from those of uncontaminated material. Another more sensitive procedure is an etch-anodize process known as “blue etch” for the characteristic color of the Table 8.8 Thickness of oxide formed on commercially pure titanium as a function of temperature Temperature

Table 8.9 Estimated minimum metal removal required after thermal exposure of titanium alloys in an oxidizing atmosphere Heat-treating temperature °C

°F

480–593 594–648

900–1100 1101–1200

649–704

1201–1300

705–760

1301–1400

761–787

1401–1450

788–815

1451–1500

816–871

1501–1600

872–898

1601–1650

899–926

1651–1700

927–954

1701–1750

872–898

1601–1650

899–926

1651–1700

927–954

1701–1750

955–982

1751–1800

983–1010

1801–1850

1011–1038

1851–1900

1039–1066

1901–1950

Time at temperature, h

Measurable thickness

°C

°F

mm

in.

315 425 540 650 705 760 815 870 925 980 1040 1095

600 800 1000 1200 1300 1400 1500 1600 1700 1800 1900 2000

None None None <0.005 0.005 0.008 <0.025 <0.025 <0.05 0.05 0.10 0.36

None None None <0.0002 0.0002 0.0003 <0.001 <0.001 <0.002 0.002 0.004 0.014

Heated for 1 2 h in air

oxygen-enriched area. Blue etch anodize was used for many years as an inspection procedure for the detection in forged titanium alloys of oxygen-enriched surface-connected defects re-

lated to melting problems. For other mill products, such as plate, blue etch or other surface etching is replaced by microexamination of representative samples removed from the product. Hydrogen. Current specifications limit hydrogen content to a maximum of 100 to 200 ppm, depending on alloy and mill form. Small amounts of hydrogen can be tolerated in titanium alloys with the specific limiting amount determined by the type of alloy. The danger of hydrogen pickup is of greater importance than that of oxidation because hydrogen does not create a visible surface condition that can be used as a check against excess hydrogen. Above the limits shown, hydrogen embrittles some titanium alloys, thereby reducing impact strength and notch tensile strength and causing

(a) Values shown are typical; actual values may vary with alloy type.

≤12 ≤4 4–12 ≤1 1–8 8–12 ≤1 1–4 4–8 8–12 ≤1 1–2 2–4 4–8 8–12 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2 ≤1 2 1 –1 2 1–2

Minimum stock removal per surface(a) mm

in.

0.005 0.008 0.015 0.013 0.020 0.025 0.025 0.036 0.038 0.043 0.030 0.038 0.046 0.051 0.056 0.036 0.041 0.051 0.058 0.066 0.076 0.066 0.081 0.089 0.086 0.091 0.107 0.097 0.107 0.122 0.066 0.081 0.089 0.076 0.091 0.107 0.097 0.107 0.122 0.114 0.137 0.160 0.145 0.178 0.216 0.178 0.229 0.292 0.229 0.305 0.406

0.0002 0.0003 0.0006 0.0005 0.0008 0.0010 0.0010 0.0014 0.0015 0.0017 0.0012 0.0015 0.0018 0.0020 0.0022 0.0014 0.0016 0.0020 0.0023 0.0026 0.0030 0.0026 0.0032 0.0035 0.0034 0.0036 0.0042 0.0038 0.0042 0.0048 0.0026 0.0032 0.0035 0.0030 0.0036 0.0042 0.0038 0.0042 0.0048 0.0045 0.0054 0.0063 0.0057 0.0070 0.0085 0.0070 0.0090 0.0115 0.0090 0.0120 0.0160

Heat Treating / 63 delayed cracking. High hydrogen content can lead to premature failure of a component. Hydrogen pickup occurs not only during heat treatment but also during pickling or chemical cleaning operations used to remove alpha case. The amount of hydrogen pickup can only be determined by chemical analysis. If high hydrogen content is found, vacuum annealing is required. A typical vacuum annealing cycle consists of heating at, or close to, the annealing temperature for two to four hours in a vacuum of not less than 10 μm. With the exceptions of high vacuum, salt baths, and chemically inert gases such as argon, all heat treating atmospheres contain some hydrogen at temperatures used for annealing titanium. Hydrocarbon fuels produce hydrogen as a byproduct of incomplete combustion; electric furnaces with air atmospheres contain hydrogen from breakdown of water vapor. Because small amounts of hydrogen can be tolerated in titanium and because inert media are expensive, most titanium heat treating operations are performed in conventional furnaces employing oxidizing atmospheres with at least 5% excess oxygen in the flue gas. An oxidizing atmosphere serves in two ways to reduce hydrogen pickup: it reduces the partial pressure of hydrogen in the surrounding atmosphere, and it provides the titanium with a protective surface oxide that retards hydrogen pickup. Nitrogen, Carbon Monoxide, and Carbon Dioxide. Nitrogen is absorbed by titanium during heat treatment at a much slower rate than oxygen and, thus, does not present a serious contamination problem. Dry nitrogen has been used successfully as a lower-cost protective atmosphere for heat treating of titanium forgings that are to be fully machined after treatment. If absorbed in sufficient quantities, however, nitrogen can lead to alpha case and form a hard, brittle compound. The gases CO and CO2 decompose in the presence of hot titanium and produce surface oxidation; they are not recommended for titanium alloy heat treating.

Chlorides. Titanium alloys are subject to stress corrosion when parts with high residual stress are exposed to chlorides at temperatures above 290 °C (550 °F). Salt from fingerprints and the chlorides contained in some degreasing solutions can cause stress-corrosion cracking at temperatures above 315 °C (600 °F). Although this phenomenon is readily produced in laboratory testing and is known to occur during heat treatment, hot-salt cracking in service has not been a significant problem. Care is required during thermal processing to ensure freedom from chloride contamination.

Growth during Heat Treatment Due to microstructural changes effected during heat treatment, component growth can occur. Solution treating of large parts requires allowances for growth during heat treatment. The growth due to heating can be retained after cooling, and this growth can be increased either by longer holding times at solution temperature or by lower heating rates. Table 8.10 gives examples of net growth of Ti-6Al-4V alpha-beta alloy specimens heated to 955 °C (1750 °F).

Hot Isostatic Pressing Hot isostatic pressing (HIP) has become an accepted method for the closure of internal solidification shrinkage or gas porosity in titanium castings. It also is used in P/M processing. Because thermal conditions between 899 and 955 °C (1650 and 1750 °F) are used for two to four hours, HIP clearly functions as a heat treatment. HIP is conducted on chemically clean components, in a heated, argon-filled pressure vessel, usually at pressures of 69 to 103 MPa (10–15 ksi). Higher HIP pressures of 206 MPa (30 ksi) have been employed for some high-

Table 8.10 Effect of heating rate and time on growth of Ti-6Al-4V alpha-beta alloy heat treated at 955 °C (1750 °F) Heating rate

Mill heat(a)

°C/min

°F/min

Holding time(b), h

Net growth(c), %

A B A B A B B B(e)

3.3 3.3 3.3 3.3 3.3 3.3 10 10

6 6 6 6 6 6 18 18

0 0 1 1 2 2 1 1

0.27 0.22 0.60 0.49 1.00 0.90(d) 0.32 0.35

Test conditions: 50 mm (2 in.) specimens were taken in the longitudinal direction (except where otherwise indicated) from material annealed 2 h at 705 °C (1300 °F) and air cooled. No growth was observed in specimens tested during annealing. (a) Beta transus temperatures (determined metallographically) were 990 °C (1810 °F) for heat A and 1015 °C (1860 °F) for heat B. (b) All specimens water quenched after holding for time indicated. (c) As determined by Leitz-Wetzler dilatometer. (d) Calculated from curve. (e) Specimen taken in transverse direction

temperature titanium alloys. The temperatures used are in the high end of the alpha-beta range for the few alloys (principally Ti-6Al-4V) that are cast plus hot isostatically pressed. Heat treatment after HIP generally is close to, yet below, the beta transus. Properties for Ti-6Al-4V vary with the HIP temperature. A HIP temperature of 955 °C (1750 °F) was thought by some investigators to produce a better structure and properties than the lower HIP temperature of 899 °C (1650 °F). However, after a number of years where both temperatures were in use, specification consolidation has lead to the acceptance of the lower-temperature HIP cycle. The cooling rate from HIP can affect subsequent post-heat treatment properties of titanium alloys. HIP has been shown to reduce the scatter band of fatigue property results and to improve minimum fatigue life. HIP temperatures can coarsen the alpha platelet structure, causing a slight loss in tensile strength, but the overall benefits of HIP normally exceed the potential detriment to some alloy properties. (See Chapter 6 for other discussion on the effects of HIP.)

Titanium: A Technical Guide Matthew J. Donachie, Jr., p65-78 DOI:10.1361/tatg2000p065

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 9

Joining Technology and Practice This chapter considers the subject of titanium joining with respect to its three broad categories:

• Fusion welding • Solid-state welding • Brazing Fusion welding, as is well known, relies on the melting of the base alloy(s), or a filler plus the alloy, to produce a solidified region of weld metal that effects a bond or joint between the respective workpieces. Solid-state welding does the same thing without producing a formerly melted bond area, although solid-state welding may use an interlayer for diffusion bonding. The interlayer invariably will be a different alloy than the pieces being bonded. Brazing relies on the melting and subsequent solidification of an interlayer (braze metal) without any melting of the base metal. Most fabrication welding on titanium and its alloys is on wrought material that has been heat treated or otherwise thermomechanically processed. Cast alloy welding generally is done for purposes of casting repair (see Chapter 6).

Joining a Reactive Metal Titanium has a strong chemical affinity for oxygen, and a stable, tenacious oxide layer forms rapidly on a clean surface, even at room temperature. This behavior leads to a natural passivity that provides a high degree of corrosion resistance. The strong affinity of titanium for oxygen increases with temperature and the surface oxide layer increases in thickness at elevated temperatures (Table 8.8). At temperatures exceeding 500 °C (930 °F), the oxidation resistance of titanium decreases rapidly and, as noted previously, the metal becomes highly susceptible to embrittlement by oxygen, nitrogen, and hydrogen, which dissolve interstitially in titanium. Therefore, the melting, solidification, and solid-state cooling associated with fusion welding must be conducted in completely inert or vacuum environments. Similarly, the

temperatures and times used for solid-state bonding or for brazing require that processing be conducted in an inert or vacuum environment. Open-air techniques can be used with fusion welding when the area to be joined is well shielded by an inert gas. By and large, however, atmospheric control by means of a “glove box,” temporary bag, or chamber is preferred. Temperatures for all of the customary metallic joining processes can range from low in the alpha-beta range, above approximately 538 °C (1000 °F), to above the melting temperature of the respective alloys. Solidified cast structures can arise in the cast weld metal area. Coarse structures can form in the weld fusion zone or in the heat-affected zone (HAZ) of a fusion-welded joint, due to holding at high temperatures or due to slow cooling rates from the joining temperatures. Coarse structures can arise in solid-state bonding processes, especially because the joining temperature can be high in the alpha-beta range, and cooling rates from joining can be low. Special Considerations. Because titanium is a very reactive material and interacts with many atmospheres, special considerations are required both before and during joining to ensure successful joints and acceptable strength of titanium and its alloys. Titanium and titanium alloys can be successfully joined for applications ranging from subzero levels to elevated temperatures when proper precautions are taken and correct preparations are made. Most welding techniques are available for titanium. Titanium alloys can be fusion and solid-state welded, as well as brazed. No fluxes are used when fusion or solid-state welding titanium and its alloys, but fluxes can be used in some situations for brazing. Because titanium alloy welds are commonly used in fatigue-critical applications, a stress-relief operation is generally required following welding. Specific stress-relief temperatures and times depend on the base-metal (Table 8.3). Three principal conditions need to be met in titanium joining:

• Detrimental interstitial elements must be excluded from the joint region

• Contaminants (e.g., scale and oil) must be excluded from the joint region

• Detrimental phase changes must be avoided to maintain joint ductility The essence of welding titanium and its alloys is adherence to these principles.

Weldability Alpha and near-alpha alloys such as Ti-5Al-2.5Sn, Ti-6Al-2Sn-4Zr-2Mo, Ti-5Al-5Sn2Zr-2Mo, Ti-6Al-2Cb-1Ta-1Mo, and Ti-8AllMo-1V are always welded in the annealed condition. Unalloyed titanium and alpha titanium alloys have good weldability because they are insensitive to heat treatment. They are readily weldable if joined in the annealed condition. They have good weldability due to their good ductility. Welding operations have little effect on the mechanical properties of annealed material in the heat-affected zone. Fusion welding of cold-worked alloys anneals the HAZ adjacent to the weld metal and is detrimental to the strength of a cold-worked alloy. Therefore, all grades of unalloyed titanium and the alpha alloys are normally welded only in the annealed condition. Stress relieving of weldments is commonly recommended. Alpha-Beta Alloys. Welding alpha-beta alloys can significantly change their strength, ductility, and toughness characteristics as a result of the thermal cycle to which they are exposed. Alpha-beta alloys, such as Ti-6Al-4V and other weakly beta-stabilized alloys, can be joined successfully in the annealed condition or in the solution-treated and partially aged condition, with aging completed during the postweld stress-relief heat treatment. Low ductility results from welding of many alpha-beta alloys. The low ductility of most alpha-beta alloy welds is caused by phase transformations.

66 / Titanium: A Technical Guide In contrast to unalloyed titanium and the alpha alloys, which can be strengthened only by cold work, the alpha-beta (and beta) alloys can be strengthened by heat treatment; this factor adds a complication to the choice of a joining process. Although the alpha-beta alloy Ti-6Al-4V is weldable, strongly beta-stabilized alpha-beta alloys are difficult to join by fusion welding techniques. Strongly beta-stabilized alpha-beta alloys generally are embrittled by welding, but solid-state techniques can be used. The lower weld ductility of most alpha-beta alloys is caused by phase transformations in the weld metal or the heat-affected zone, or both. Alpha-beta alloys can be welded autogenously (no filler) or with unalloyed titanium or alpha-titanium alloy filler metal to produce a weld metal that is low in beta phase. It is common to weld some of the lower-alloyed materials with matching filler metals. Where strength is not critical and more toughness is desired, unalloyed titanium filler metals can be used. The use of filler metals may improve ductility of the solidified weld metal but will not prevent embrittlement of the HAZ in susceptible alloys. In particular, such procedures do not overcome the low ductility of the HAZ in alloys that contain large amounts of beta stabilizers. In addition, low-alloy welds can be embrittled by hydride precipitation. It should be noted, however, that with proper preparation of joints, storage of filler metal, and shielding, hydride precipitation can be avoided. Ti-6Al-4V has the best weldability of the alpha-beta alloys. This weldability can be attributed to two principal factors. First, the alpha-prime martensite that forms in Ti-6Al-4V is not as hard and brittle as that exhibited by more heavily beta-stabilized alloys, such as Ti-6Al-6V-2Sn. Secondly, Ti-6Al-4V exhibits a relatively low hardenability on cooling from solution treatment temperatures. This behavior allows the formation of higher proportions of the more desirable Widmanstätten alpha-plus-retained beta microstructure even at relatively high rates of weld cooling. Ti-6Al-4V alloy is welded with filler metal of matching composition in the extra-low-interstitial (ELI) grade to improve ductility and toughness. Due to its single-phase mode of solidification (i.e., absence of low-melting point eutectics), Ti-6Al-4V is also highly resistant to solidification-related and liquation-related cracking. However, the occurrence of solid-state cracking and the formation of porosity can be encountered during welding. Fortunately, these defects are not metallurgically inherent in Ti-6Al-4V, but rather they originate from readily correctable deficiencies in preweld cleaning of the workpieces and shielding of the weld zone from atmospheric contamination. Alpha-beta alloys that are highly beta stabilized, such as Ti-6Al-2Sn-4Zr-6Mo and Ti-6Al6V-2Sn, have limited weldability. They tend to crack when welded under high restraint or when minor defects are present in the weld

zone. The resistance to cracking can be improved by preheating in the range of 150 to 175 °C (300–350 °F) before welding and then stress relieving immediately after welding. Beta Alloys. Metastable beta alloys, such as Ti-13V-11Cr-3Al, Ti-11.5Mo-6Zr-4.5Sn, Ti-8Mo8V-2Fe-3Al, Ti-15V-3Cr-3Al-3Sn, and Ti-3Al-5V6Cr-4Zr-4Mo, are weldable in the annealed or solution heat-treated condition. Welded joints have good ductility but relatively low strength in the as-welded condition. They are, however, used most often in this condition because the welded joint can respond differently to heat treatment than the base metal, and heat treatment of welded beta alloys thus can lead to difficulties in joint ductility. Aging can take place if the welds are exposed to elevated temperatures in service, and aged welds in beta alloys can be quite brittle. Heat treatment to strengthen welded beta alloys by age hardening should be used with caution. To obtain full strength, some metastable beta alloys are welded in the annealed condition; the weld is cold worked by peening or planishing, and the weldment is then solution treated and aged. This procedure obtains adequate ductility in the weld.

Brazeability It should be recognized that the tensile properties of heat-treatable titanium alloys can be adversely affected by brazing unless the assembly can be heat treated after brazing (e.g., alpha-beta titanium alloys must be solution treated, quenched, and aged to develop maximum strength). It is difficult to select a filler metal that is suitable for brazing and solution treating in a single operation. Similarly, it is not always possible to quench a brazed assembly at the desired cooling rate, and certain configurations, such as honeycomb-sandwich structures, cannot be quenched rapidly without distortion. Brazing at the aging temperature is impractical because few filler metals melt and flow at these temperatures. Selection of filler metal for brazing titanium alloys is critical because titanium alloys react with many of the constituents of brazing filler metals to form undesirable intermetallic compounds. Also, the possibility of galvanic corrosion must be considered when filler metals are selected for brazing titanium-base metals. While titanium is an active metal, its activity tends to decrease in an oxidizing environment because its surface undergoes anodic polarization similar to that of aluminum. Thus, in many environments, titanium becomes more chemically inactive than most structural alloys. The corrosion resistance of titanium is generally not affected by contact with structural steels, but other metals, such as copper, corrode rapidly in contact with titanium under oxidizing conditions. Thus, filler metals must be chosen carefully to avoid preferential corrosion of the brazed joint.

In general, the concepts on weldability developed earlier in this Chapter apply to brazing. However, chemical interaction with braze filler metal or corrosion of the braze filler metal must be considered. Generally, exclusive of such interaction, temperature of brazing is the important concern for property effects. If brazing is carried out under conditions similar to those of welding, then similar property results should be expected. Alpha and Near-Alpha Alloys. Brazing of alpha and near-alpha alloys is easily effected. Material properties of such alloys are not affected greatly by brazing, and assemblies are not heat treatable. Alpha-Beta Alloys. Wrought alpha-beta titanium alloys generally are fabricated to obtain a fine-grain, equiaxed, duplex microstructure to produce maximum ductility. It is desirable to maintain this microstructure by requiring that the brazing temperature not exceed the beta transus, which varies from about 599 to about 1038 °C (1650–1900 °F) in alpha-beta alloys. Ideally, brazing is done no higher than 50 to 80 °C (100–150 °F) below the beta transus. The ductility of alpha-beta alloys can be impaired if this temperature is exceeded. Beta Alloys. Numerous beta alloys are available. In the annealed condition, these metals are unaffected by brazing. However, if heat treated, the brazing temperature can have an effect on the properties of the beta alloy. Optimum ductility in the base metal is obtained by brazing at the solution treating temperature. The ductility of a base metal beta alloy decreases as braze temperature increases.

Weld Microstructure The microstructure of a weldment, as well as the extent to which it differs from the thermomechanically processed wrought base material or cast and heat-treated base material, is strongly influenced by the thermal cycle of welding. Two characteristics that are vitally important are the size and shape of the priorbeta grains and the phase transformations that take place during weld cooling. These characteristics are described for both alpha-beta (Ti-6Al-4V) and metastable beta alloys in this section. Also described are weld defects (macrosegregation, microsegregation, and solidification-defect formation) and the effects of postweld heat treatment on welded titanium structures. Alpha-Beta Alloys. Mechanical properties of composite weld structures in titanium alloys depend on structural characteristics of each weld region, which in turn depend on the specific thermal cycle(s) imposed during welding and on subsequent postweld heat treatment. As the weld macrographs in Fig. 9.1 to 9.4 illustrate, the weld fusion zone in titanium alloys is characterized by coarse, columnar prior-beta grains that originated during weld solidification. The size and morphology of these grains

Joining Technology and Practice / 67 depend on the nature of the heat flow that occurs during weld solidification. Under simple, uniaxial heat flow (such as occurs in a spot weld), the beta grains nucleate epitaxially on beta grains in the base-metal substrates and solidify preferentially in a direction parallel to the maximum temperature gradient (i.e., parallel to the welding electrodes) until they impinge at a horizontal weld centerline (Fig. 9.1). Under two-dimensional heat-flow conditions characteristic of full-penetration plasma arc, laser beam, and electron beam welds, the columnar beta grains solidify inward from the base metal in a direction nearly parallel to the sheet or plate surface, ultimately impinging to form a vertical grain boundary at the weld centerline (Fig. 9.2, 9.3). Three-dimensional or mixed two-dimensional and three-dimen-

sional heat-flow conditions, such as those present in single-pass and multipass gas-tungsten arc-welded (GTAW) and gas-metal arc-welded (GMAW) structures, promote the formation of more complex, multidirectional beta grain morphologies (Fig. 9.4). The fusion-zone beta grain size depends primarily on the weld energy input, with a higher energy input promoting a larger grain size. Due to epitaxial grain growth, the fusion-zone beta grain size may also depend on the beta grain size in the near-HAZ directly adjacent to the fusion line. This latter effect of base-metal grain size is most significant in the welding of extremely coarse-grained cast or beta-annealed alloys, as shown in Fig. 9.3 for an electron beam weld produced in a coarse-grained forging. Because weld mechanical properties, particularly ductility, can be degraded by a coarse prior-beta grain size, it is important to maintain as fine a grain structure as possible by minimizing the weld energy input. As just indicated, appreciable beta grain growth occurs in the near-HAZ directly adjacent to the weld fusion line where peak temperatures range from between the alloy solidus down to the beta transus. The transus is approximately 995 °C (1825 °F) for Ti-6Al-4V. As in the fusion zone, the extent of this growth increases with energy input into the weld zone.

Consequently, this region can vary markedly in width, being almost unresolvable in electron beam and laser beam welds and yet being several beta grains wide in gas-tungsten arc welds (Fig. 9.2, 9.4). Further from the fusion line, temperatures below the beta transus are encountered. These lower temperatures promote transformation of alpha phase in the mill-annealed microstructure to various proportions of the high-temperature beta phase. The presence of even small quantities of alpha phase at peak temperatures in the weld thermal cycle is sufficient to prevent beta grain growth, thereby contributing to the improved ductility of this region as compared with the coarser-grained fusion zone and near-HAZ. During the past several decades, investigators have evaluated methods for promoting beta grain refinement in titanium alloy fusion welds. This work used electromagnetic stirring techniques and inoculation with rare-earth (RE) elements and titanium “microcooler” particles to promote heterogeneous nucleation of beta grains during solidification and thereby provide a refined fusion-zone grain structure. Several of these approaches were effective in refining the beta grain structure and correspondingly improving fusion-zone mechanical properties. Figure 9.5 shows the equiaxed prior-beta grain structure in the fusion zone of a gas-tungsten

(a)

Macrograph showing coarse prior-beta grain size in weld metal of an electron beam-welded Ti-6Al-4V forging

Fig. 9.3

(b)

Fig. 9.1

Columnar beta grains in a spot weld of alpha-beta alloy Ti-6Al-4V. (a) 10×. (b) 240×

Fig. 9.2

Macrograph showing columnar beta grains in a Ti-6Al-4V laser beam weld. 13×

Macrograph showing equiaxed prior-beta grain structure in the fusion zone of a Ti-6Al-4V weld joint produced by gas-tungsten arc welding using titanium microcooler additions. 12×

Fig. 9.5 Fig. 9.4

Macrograph of a multidirectional beta grain morphology in a Ti-6Al-4V gas-tungsten arc weld. 30×

68 / Titanium: A Technical Guide arc weld produced in a Ti-6Al-4V joint using titanium powder microcooler additions. Despite the success of these techniques, particularly in thin-sheet materials, commercial application has been limited. In addition to prior-beta grain size, weld-zone mechanical properties in Ti-6Al-4V are significantly influenced by the manner in which the high-temperature, beta phase transforms on cooling to the low-temperature, hexagonal close-packed phase. Characteristics of this “transformed-beta” microstructure depend principally on the cooling rate from above the beta transus temperature, which is correspondingly influenced by the welding process, process parameters, and other welding conditions (such as workpiece geometry and fixturing). (See Chapter 3 for more details on the effects of temperature and cooling rate on microstructure.) In the near-HAZ regions, high cooling rates associated with low-energy input welding processes, such as laser beam, electron beam, and resistance welding (100–10,000 °C/s, or 180–18,000 °F/s), promote transformation of beta to alpha-prime martensite. This extremely fine, acicular transformation product exhibits high strength and hardness but relatively low ductility and toughness. At the lower cooling rates associated with gas-tungsten, gas-metal, or plasma arc welding (10–100 °C/s, or 18–180 °F/s), a coarser structure of Widmanstätten alpha plus retained beta, or a mixture of this structure and alpha-prime, is produced, which exhibits yield and tensile strengths superior to those of the mill-annealed base metal and a ductility and toughness greater than those of an entirely martensitic microstructure. In the far-HAZ regions, microstructures are comprised of primary alpha phase, originating from the base-metal microstructure, dispersed in a matrix of transformed beta. Weld microstructure and mechanical properties also can be influenced by postweld heat treatment, with specific postweld heat treatment effects depending on the heat treatment time and temperature and on the as-welded microstructure. Metastable Beta Alloys. The weld HAZ and fusion-zone beta grain macrostructures in metastable beta titanium alloys are essentially identical to those observed in alpha-beta alloys. Due to the appreciable beta stabilizer content in metastable beta titanium alloys, and the relatively slow diffusivity of these elements, the high-temperature beta phase is retained on weld cooling to room temperature (although a thermal transformation to omega phase may occur in certain alloys). Subsequent postweld aging heat treatment at temperatures ranging from about 450 to 650 °C (840–1200 °F) promotes the precipitation of fine alpha phase both intragranularly and along prior-beta grain boundaries. Through proper control of the aging temperature and time, a wide range of base metal and weld-zone strength/ductility combinations can be achieved.

The relatively uniform precipitation of extremely fine alpha phase during low-temperature aging at 482 °C (900 °F) for 24 h, as shown in Fig. 9.6(a) and (b) for a gas-tungsten arc weld fusion zone in Beta-C, promotes high fusion-zone hardness and ultimate tensile strength (UTS) of 1382 MPa (200 ksi) and low ductility (2.5 % elongation). As shown in Fig. 9.6(c) and (d), an increased aging temperature promotes coarser alpha precipitation and results in softening of the alloy with a UTS of only 1121 MPa (163 ksi), and an increase in ductility (8.0% elongation) for the gas-tungsten arc weld fusion zone in Beta-C aged at 593 °C (1100 °F) for 8 h. It should be noted that in contrast to alpha-beta alloys, residual microsegregation from weld solidification in beta alloys can influence alpha precipitation on aging, particularly for low-temperature aging heat treatments (Fig. 9.6).

• Solidification segregation (macrosegregation • • • • •

and microsegregation) Solidification cracking Contamination cracking Hydrogen embrittlement Subsolidus (ductility dip) cracking Porosity

In many alloy systems, weldability is determined by the capability of the alloy to produce a weld that is free of discontinuities or defects. Defects that may be encountered when welding titanium alloys include:

Macrosegregation in weldments is defined as segregation that extends over distances of several grain diameters. In titanium alloy fusion weldments, macrosegregation occurs primarily in the form of transverse solute banding. These solute-enriched or solute-depleted bands normally appear as curvilinear contours on the polished and etched weldment surface and are attributed to thermal variations in the weld pool, which periodically change the solid-liquid interface velocity. Transverse solute banding has occurred using both arc and high-energy welding processes. Studies on solute redistribution in Ti-6Al-4V gas-tungsten arc welds found distinct metallographic evidence of transverse solute banding. Electron microprobe analysis determined that the bands resulted from vanadium and aluminum segregation. The effect of macrosegregation on subsequent beta-phase decomposition during cooling depends on the extent of residual segregation at

(a)

(b)

(c)

(d)

Weld Defects

Postweld heat-treated gas-tungsten arc-welded fusion zone in beta-C sheet. (a) Aged at 482 °C (900 °F) for 24 h, 275×. (b) Same heat treatment as (a). 690×. (c) Aged at 593 °C (1100 °F) for 8 h. 275×. (d) Same heat treatment as (c). 690×

Fig. 9.6

Joining Technology and Practice / 69 the transformation temperature and on the local alloy chemistry. Solute diffusion that occurs after solidification and prior to solid-state phase transformations reduces the magnitude of macrosegregation. In near-alpha and alpha-beta alloys, little effect of macrosegregation has been reported. However, in the more heavily beta-stabilized alloys, strong macrosegregation effects have been observed. This effect is shown in Fig. 9.7 for a gas-tungsten arc weld fusion zone produced between the alpha-beta alloy Ti-6Al-4V and the metastable beta alloy Ti-15V-3Cr3Al-3Sn. Transverse solute bands in the weld fusion zone, which were found to be depleted in the beta stabilizers vanadium and chromium, transformed to martensite while the remaining, more heavily beta-stabilized regions were retained as beta phase during weld cooling. A similar effect of macrosegregation due to transverse solute banding and incomplete mixing was recently observed for dissimilar alloy laser welds produced between Ti-6Al-4V and the metastable beta alloys Beta-C and Beta-21S. It should be noted that the degradation of weld integrity, structure, or properties due to macrosegregation and/or microsegregation is generally not significant in titanium alloys as in other alloy systems due to the limited extent of segregation of common alloying elements and the appreciable diffusional homogenization of alloying elements during weld cooling through the beta-phase field. Microsegregation. The nonequilibrium solidification conditions experienced during fusion welding result in a breakdown of the advancing solid-liquid interface into cellular, cellular-dendritic, and dendritic substructures. Interface breakdown in commercial titanium alloy welds is associated with the segregation of alloying elements on an intercellular or interdendritic scale. Microsegregation is much more evident in metastable beta titanium alloy weldments than in alpha-beta weldments. This behavior is due primarily to the appreciably

higher alloying levels (and therefore higher absolute compositional differences in segregated regions) and the absence of a transformed structure in the completely retained-beta fusion zone. Microsegregation effects have also become significant in the joining of advanced, elevated-temperature titanium alloys that contain rare-earth elements for dispersoid strengthening. As indicated earlier, local variations in beta stabilizer content due to microsegregation can affect the alpha-phase precipitation response during subsequent postweld heat treatment. Solidification Cracking. Relative to many other structural alloys, such as aluminum alloys and many austenitic stainless steels, titanium alloys generally are not considered susceptible to fusion-zone solidification cracking. However, under severe conditions of restraint, solidification cracking along columnar beta grain boundaries can occur. Some work on the solidification cracking of Ti-6Al-4V indicated that solidification cracking must be considered when designing joints in Ti-6Al-4V structural components. However, this observation generally conflicts with the well-known excellent cracking resistance of the alloy. Test restraint and strain conditions can dramatically alter perceptions of crack resistance. There is an absence in most titanium alloys of second-phase dispersoids or precipitate particles such as those of aluminum and nickel found in age-hardened alloys. In conjunction with the fact that impurities at grain boundaries are limited, conventional titanium alloys are generally very resistant to HAZ or weld-metal liquation cracking. In RE dispersion-strengthened titanium alloys, liquation of the dispersoid particles in the weld HAZ can occur, with this liquid subsequently wetting adjacent beta grain boundaries. Although cracking along these boundaries has not been observed, it may be expected in the arc welding of these alloys under conditions of high weld restraint.

Contamination Cracking. When titanium is exposed to air, moisture, or hydrocarbons at temperatures exceeding 500 °C (930 °F), it will readily pick up oxygen, nitrogen, carbon, and hydrogen. These small atoms of the interstitial elements will enter the crystal lattice in monatomic form and will migrate to interstitial sites (sites located between titanium atoms). As noted previously, these interstitial elements inhibit plastic deformation and increase strength, but cause a substantial loss in ductility. If contamination levels exceed a certain amount, cracking can ensue from the stresses generated during welding. Levels of oxygen on the order of 3000 ppm in the weld have been known to result in transverse cracking, with the alpha phase being particularly susceptible to contamination cracking. Contamination cracking can be avoided by minimizing exposure of the molten weld pool and the heated weld region to interstitial elements. This is accomplished by:

• Thoroughly degreasing the joint prior to welding

• Providing sufficient inert gas shielding to •

the torch, trailing shoe, and back side of the joint Using shielding gas with a sufficiently low dew point

When titanium is oxidized, it assumes different colors depending on alloy content and the degree of oxidation. These colors range from silver to straw, to blue, to white (severe oxidation). While the presence of a blue or white oxide serves as a good indicator that unacceptable contamination has occurred, its absence is no guarantee that the weld is interstitial-free. Hydrogen Embrittlement. While hydrogen can play a role in contamination cracking, as previously discussed, it can also lead to hydrogen embrittlement or hydrogen-delayed cracking by being introduced into titanium alloys in other ways. (See Chapters 8 and 12 for more information on the effects of hydrogen.)

Welding Specifications

(a)

(b)

Micrographs showing martensitically transformed solute bands (small arrows) in dissimilar alloy gas-tungsten arc welding between Ti-6Al-4V and Ti-15V-3Cr-3Al-3Sn sheets. (a) Visible light microscope; large arrow indicates fusion line. (b) Scanning electron microscope

Fig. 9.7

The American Welding Society has published specifications related to welding of titanium. For example, AWS 5.16, “Specification for Titanium and Titanium Alloy Bare Welding Rods and Electrodes,” provides requirements for titanium and titanium alloy welding rods for use with GTAW and GMAW processes. Other specifications exist for welding and brazing of titanium alloys. Government and industry have developed numerous additional specifications related to the joining of titanium. These specifications can be quite general or very specific, often describing in detail the fabrication or weld repair of an individual component. While there is a continuing trend toward standardization of specifications, unique specification require-

70 / Titanium: A Technical Guide ments could be encountered by designers planning to use titanium and its alloys. This situation is not restricted to titanium but is characteristic of the more technologically sophisticated alloys used in high-performance applications.

Joint Design Criteria and Limitations Designers of titanium fabricated structures must consider both joining process applicability and the physical characteristics and mechanical properties of the joints. From a joining process standpoint, an efficient design uses a process optimally suited to a particular material thickness and joint configuration. Process suitability must consider component size and shape. For example, will the component fit in an available electron beam welding (EBW) chamber or brazing furnace? Can the entire part be suitably protected from the atmosphere during diffusion bonding, GTAW, or PAW? What is the cost of producing the joint (including both capital equipment and operating costs) and postjoining processing requirements. The design of titanium fabricated structures also is influenced by the characteristics and mechanical properties of a joint produced by a particular joining process. For example, physical characteristics of the weld, including undercut or underfill in fusion welds, upset in solid-state welds, and weld distortion are important considerations. These characteristics affect not only the physical dimensions of the component but also joint mechanical properties. Obviously, the mechanical properties of the joint, as

influenced by the integrity and metallurgical structure of the joint, are the principal considerations in joint design. Such behavior as low fusion-zone ductility, low toughness in rapidly cooled welds, or poor axial fatigue behavior when defects occur are important characteristics of joints that should influence component design.

Precautions in Welding Practice Production of high-quality welds in titanium and titanium alloys requires meticulous preweld cleaning of the workpiece and consumable and adequate gas shielding to prevent atmospheric contamination. Surface Cleaning and Scale Removal. Mill-annealed titanium sheet and plate generally are supplied in a condition that requires only the removal of surface grease, oil, and dirt. As shown in Fig. 9.8, the cleaning procedure depends on whether the oxide layer in the joint area is light or heavy. Light cleaning is normally accomplished by wiping with or dipping in a nonchlorinated solvent such as acetone or methyl-ethyl-ketone (MEK). Chlorinated solvents, such as trichlorethylene, should not be used for degreasing titanium alloys because the chlorine residues cause intergranular attack in subsequent heating operations. All handling should be performed with clean white gloves. For scaled oxide surfaces, titanium alloys can be treated in molten salt baths or by abrasive blasting, especially if scales are heavy, such as might result from high-temperature heat treatment or thermomechanical process-

ing. Materials that exhibit a light oxide scale as a result of heat treatment below about 600 °C (1110 °F) or that contain entrapped oil from machining operations should be pickled for 5 to 10 min in a solution of 30 to 40% nitric acid and 4 to 5% hydrofluoric acid in water at a temperature between 20 and 70 °C (68 and 160 °F). Alternative procedures suggest that chemical cleaning can be performed by pickling for 1 to 20 min in solutions containing 20 to 47% nitric acid plus 2 to 4% hydrofluoric acid in water, or about a 10 to 1 ratio of nitric acid in hydrofluoric acid; bath temperature should be 27 to 71 °C (80–160 °F). Pickled pieces should be rinsed in water, dried, and either directly welded or wrapped in clean plastic. Cleaning also may be required for weld filler metal that has become dirty due to inadequate storage or careless handling. Degreasing the filler rod or wire is necessary to eliminate subsequent weld contamination problems originating from these sources. Surface Protection. Effective shielding of the weld zone from the atmosphere during welding is extremely important in ensuring maximum weld ductility and toughness and in reducing the potential for solid-state weld cracking. Optimum shielding conditions are provided by welding within a permanent or collapsible clear plastic enclosure that has been evacuated and purged with argon at a dew point of –24 °C (–75 °F). Alternatively, localized trailing and backing shields can be used, particularly for automatic welding of simple joint geometries (for example, automatic butt welding of sheet). Use of localized shielding for manual welding of complex parts, although feasible, requires specially designed shielding fixtures and generally is not recommended. (Shielding gases and methods are discussed further later in this Chapter.) Fortunately, evidence of titanium weld contamination is readily apparent by discoloration of the weld surface, with a change from bright silver to straw, to magenta, and then to blue, with a gradual increase in the level of contamination. Severe contamination is associated with a white or gray powdery-appearing weld surface, and is often accompanied by solid-state cracking in the weld metal. In many high-performance applications, a bright silver color is required, although a light straw color may be accepted in less critical applications.

Fusion Welding Practice Titanium and most titanium alloys can be welded by the following fusion welding techniques:

Fig. 9.8

Flow chart of cleaning procedure for titanium alloys

• • • • •

Gas-tungsten arc welding (GTAW) Gas-metal arc welding (GMAW) Plasma arc welding (PAW) Electron beam welding (EBW) Laser beam welding (LBW)

Joining Technology and Practice / 71 Procedures and equipment are generally similar to those used for welding austenitic stainless steel or aluminum. Because titanium and titanium alloys are extremely reactive above 538 °C (1000 °F), however, additional precautions, ones exceeding those required during the welding of austenitic stainless steel or aluminum alloys, must be taken to shield the weld and hot root side of the joint from air. EBW involves an evacuated chamber to permit electrons to be generated and delivered to the workpiece or it involves inert gas shielding of the workpiece in nonvacuum EBW. Arc welding fusion processes such as GTAW may involve a chamber such as an inert, gas-filled, large Mylar bag in which the welding is performed. With the arc and laser welding processes, protection of the weld zone can be provided by localized inert gas shielding. Complete enclosure in a protective chamber of the high-vacuum environment associated with the electron beam welding process inherently provides better atmospheric protection but at a higher cost and with less flexibility. In addition to proper shielding, welded component cleanliness (including filler metals) is necessary to avoid weld contamination. The welding of thin to moderate section thicknesses in titanium alloys can be accomplished using all of the aforementioned processes. The GTAW process offers the greatest flexibility for both manual and automatic application at minimum capital investment. If production volume is large, the high capital investment required for LBW and EBW systems can be acceptable, based on higher welding rates and improved productivity. For titanium plate thickness exceeding about 5 mm (0.20 in.), the high-energy density processes are the most efficient. PAW, for producing welds up to about 15 mm (0.6 in.) thick, and EBW, which can readily generate single-pass welds in plates over 50 mm (2 in.) thick, are used in current aerospace practice. Complex geometries may require manual welding or the use of extensive fixturing. The automatic welding of extremely large components can also prove difficult, particularly with the EBW process. Table 9.1

Residual stresses in titanium welds can greatly influence the performance of a fabricated aerospace component by degrading fatigue properties, while distortion can cause difficulties in the final assembly and operation of high-tolerance aerospace systems. Thus, the use of high-energy density welding processes to produce full-penetration, single-pass autogenous welds, rather than multiple conventional arc welding, is desirable to minimize these difficulties. Arc Processes. GTAW is the most widely used process for joining titanium and titanium alloys, except when large thicknesses are involved. Square-groove butt joints can be welded without filler metal in base metal up to 2.54 mm (0.10 in.) thick. With thicker base metal, the joint should be grooved, and filler metal is required. Where possible, welding should be done in the flat position. GMAW is employed to join titanium and titanium alloys more than 3.18 mm (0.125 in.) thick. It is less costly than GTAW, especially when base-metal thickness is greater than 12.7 mm (0.5 in.). PAW is also applicable to the welding of titanium and titanium alloys. It is faster than GTAW and can be used on thicker sections, such as one-pass welding of titanium alloy plate up to 12.7 mm (0.5 in.) thick, using squaregroove butt joints and the keyhole technique. Resistance welding, which is another fusion welding process, occurs when heat is generated by resistance to electrical current at two surfaces in contact with each other. When heat is generated, the metal melts in the vicinity of the current flow. Pressure keeps the faces together. When the current is interrupted, a solidified weld nugget is formed. The nugget is contained within the metal being joined and does not reach an external surface. Resistance welding is fast. When done locally, a spot results—hence “spot” welding. When spots overlap, the result is resistance seam welding. Electron beam welding is a high-energy density fusion welding process that works by bombarding the joint to be welded with an intense beam of high-voltage electrons. The electron energy is converted to thermal energy as

they impact and penetrate into the workpiece. This process causes the weld-seam interface surfaces to melt and produces the weld joint coalescence desired. Originally, EBW generally was performed only under high-vacuum (1 × 10–4 torr, or lower) conditions. Currently, there are three distinct modes of EBW employed:

• High vacuum (EBW-HV), where the • •

workpiece is at a high vacuum ranging from 10–6 to 10–3 torr Medium vacuum (EBW-MV), where the workpiece can be in a “soft” or “partial” vacuum ranging from 10–3 to 25 torr Nonvacuum (EBW-NV), which is also referred to as atmospheric EBW, where the workpiece is at atmospheric pressure in air or protective gas

In all EBW applications, the region of the electron beam gun is maintained at a pressure of l0–4 torr or lower. Laser beam welding is a fusion welding process that produces coalescence of materials with the heat obtained from the application of a concentrated coherent light beam impinging upon the surfaces to be welded. The word laser is an acronym for light amplification by stimulated emission of radiation. The laser is a unique source of thermal energy, precisely controllable in intensity and position. For welding, the beam must be focused by optical elements (mirrors or lenses) to a small spot size to produce a high-power density. This controlled power density melts the metal and, in the case of deep penetration welds, vaporizes some of it. When solidification occurs, a fusion zone, or weld joint, results. A laser beam can be transmitted through the air for appreciable distances without serious power attenuation or degradation. Filler Metals for Fusion Welding. For welding titanium thicker than approximately 2.54 mm (0.10 in.) by the GTAW process, a filler metal must be used. For PAW, a filler metal may or may not be used for welding metal less than 12.7 mm (0.5 in.) thick. Filler metal compositions are shown in Table 9.1.

Chemical compositions of titanium and titanium alloy filler metals Composition, %

AWS classification

ERTi-1(a) ERTi-2 ERTi-3 ERTi-4 ERTi-0.2Pd ERTi-3Al-2.5V ERTi-3Al-2.5V-1(a) ERTi-5Al-2.5Sn ERTi-5Al-2.5Sn-1(a) ERTi-6Al-2Nb-1Ta-1Mo ERTi-6Al-4V ERTI-6Al-4V-1(a) ERTi-8Al-1Mo-1V ERTi-13V-11Cr-3Al

C

O

H

N

0.03 0.05 0.05 0.05 0.05 0.05 0.04 0.05 0.04 0.04 0.05 0.04 0.05 0.05

0.10 0.10 0.10–0.15 0.15–0.25 0.15 0.12 0.10 0.12 0.10 0.10 0.15 0.10 0.12 0.12

0.005 0.008 0.008 0.008 0.008 0.008 0.005 0.008 0.005 0.005 0.008 0.005 0.008 0.008

0.012 0.020 0.020 0.020 0.020 0.020 0.012 0.030 0.012 0.012 0.020 0.012 0.03 0.03

Single values are maximum. (a) Extra-low interstitials for welding similar base metals

Al

V

… … … … … … … … … … 2.5–3.5 2.0–3.0 2.5–3.5 2.0–3.0 4.7–5.6 … 4.7–5.6 … 5.5–6.5 … 5.5–6.75 3.5–4.5 5.5–6.75 3.5–4.5 7.35–8.35 0.75–1.25 2.5–3.5 12.5–14.5

Sn

Cr

Fe

Mo

Nb

Ta

Pd

Ti

… … … … … … … 2.0–3.0 2.0–3.0 … … … … …

… … … … … … … … … … … … … 10.0–12.0

0.10 0.20 0.20 0.30 0.25 0.25 0.25 0.40 0.25 0.15 0.25 0.15 0.25 0.25

… … … … … … … … … 0.5–1.5 … … 0.75–1.25 …

… … … … … … … … … 1.5–2.5 … … … …

… … … … … … … … … 0.5–1.5 … … … …

… … … … 0.15–0.25 … … … … … … … … …

rem rem rem rem rem rem rem rem rem rem rem rem rem rem

72 / Titanium: A Technical Guide Five of these are essentially commercially pure (CP) titanium, and the remainder are titanium alloy filler metals. Maximums are set on carbon, oxygen, hydrogen, and nitrogen contents. Filler metal composition usually is matched to the grade of titanium being welded. For improved joint ductility when welding the higher-strength grades of unalloyed titanium, filler metal of yield strength lower than that of the base metal occasionally is used. Because of the dilution that occurs during welding, the weld deposit acquires the required strength. Unalloyed filler metal is sometimes used to weld Ti-5Al-2.5Sn and Ti-6Al-4V for improved joint ductility. The use of unalloyed filler metals lowers the beta content of the weldment, thereby reducing the extent of the transformation that occurs and, thus, improving ductility. When employing pure titanium as filler metal, engineering approval is recommended to ensure that the weld meets strength requirements. Another option is normal chemistry filler metal containing lower interstitial content (oxygen, hydrogen, nitrogen, and carbon) or filler metal with alloying contents that are lower than the base metal being used. Note that the use of filler metals that improve fusionzone ductility does not preclude embrittlement of the HAZ in susceptible alloys. In addition, low-alloy welds may enhance the possibility of hydrogen embrittlement. The filler metal, as well as the base metal, should be clean at the time of welding. Wires of the size used for filler metals have a large surface-to-volume ratio. Therefore, if the wire surface is slightly contaminated, the weld can be severely contaminated. Some procedures require that the filler wire be cleaned immediately before use. An acetone-soaked, lint-free cloth serves to remove surface contamination caused by the die lubricant used in the wire drawing operation, in addition to cleaning the filler wire. Pickling in nitric-hydrofluoric acid solution is also used for cleaning. If the iron content of weld metal is above about 0.05%, preferential corrosive attack of weld metal can occur in nitric acid solutions. Welds are particularly vulnerable because of the acicular nature of any retained beta phase that is stabilized by the iron. Galvanic cells between the beta and the contiguous alpha phase initiate corrosion of the weld metal. This behavior is not true for the base metal, where retained beta is finely divided and discontinuous and corrosive attack is slight. Filler metal with low iron content should be used, and all sources of iron contamination during preparation and welding should be avoided to minimize such corrosion problems. Shielding Gases for Fusion Welding. Just as it occurs in the heat treatment of titanium and titanium alloys, pickup of detrimental gases can happen in fusion welding processes. Shielding is required. When welding titanium and titanium alloys, only argon or helium (and occasionally a mixture of these two gases) are used for shielding. Because it is more readily

available and less costly, argon is more widely used. Because of high purity (99.985% min) and low moisture content, liquid argon is often preferred. The argon gas should have a dew point of –24 °C (–75 °F) or lower. The hose used for shielding gas should be clean, nonporous, and flexible. The recommended materials are Tygon or vinyl plastic. Because rubber hose absorbs air, it should not be used. Excessive gas flow rates that cause turbulence should be avoided, and flow meters are usually employed for all gas shields. Pressure (psi) gages can be employed for trailing and backup shields. The type of shielding gas used affects the characteristics of the arc. At a given welding current, the arc voltage is much greater with helium than with argon. Because the heat energy liberated in helium is about twice that in argon, higher welding speeds can be obtained, weld penetration is deeper, and thicker sections can be welded more rapidly using helium shielding. However, when using pure helium for welding, arc stability and control of weld metal are sacrificed. Argon is used in the welding of thin and thick sections where the arc length can be altered without appreciably changing the heat input. Argon-helium mixtures are also employed, particularly 75% argon (which improves arc stability) with 25% helium (which increases penetration). The 75%Ar-25%He mixture is also frequently utilized as the shielding gas at the torch in automatic operations. Helium is used in shielding of out-of-position welds. Joint Preparation. If welding is done outside a controlled-atmosphere welding chamber, joints must be carefully designed so that both the top and the underside of the weld can be shielded. Dimensions of typical joints are given in Table 9.2. For welding titanium alloys, joint fit-up should be better than for welding other metals due to the possibility of air entrapment in the joint. To prevent separation during welding, the joint should be clamped.

Table 9.2

Cleaning. To obtain a good weld, the joint and the surfaces of the workpiece at least 50mm (2 in.) beyond the width of the gas trailing shield on each side of the weld groove must be meticulously cleaned. (See the previous discussion on cleaning in the section “Precautions in Welding Practice” in this Chapter.) Welding in Chambers. For successful arc welding of titanium and titanium alloys, complete shielding of the weld is necessary due to the high reactivity of titanium to oxygen and nitrogen at welding temperatures. Excellent welds can be obtained in titanium and its alloys in a welding chamber where welding is done in a protective gas atmosphere, thus giving adequate shielding. Welding in a chamber, however, is not always practical. For example, when manual welding within a metal chamber, the location of the glove ports and the presence of a chamber wall impose limitations on visibility, movement, and accessibility. For large assemblies, welding in a chamber requires unloading the chamber after each weldment is completed; this implies the loss or controlled removal of purging gas. The chamber must be repurged before welding the next assembly. Such procedures are time consuming and expensive. Various types of modified chambers, such as clamp-on chambers, have been tried to remedy these problems. Experimental GTAW of titanium was first done in metal chambers that can be evacuated and then backfilled with argon or helium. Such chambers are equipped with glove ports so that the welder can handle the torch and separate filler metal (if used) and the weldment without admitting air to the chamber. Viewing ports enable the welder to see the welding operation. Although expensive to operate, especially for large weldments, metal chambers frequently are used in aerospace applications. Generally, shielding gas is not supplied to the welding torch when welding titanium in a metal chamber. Excellent welds can be made if the chamber atmosphere is maintained prop-

Dimensions of typical joints for welding titanium and titanium alloys Root opening, mm (in.)

Groove angle, o

Weld bead width, mm (in.)

Square-groove butt joint 0.254–2.286 (0.010–0.90) 0.787–3.175 (0.031–0.125)

0 0–2.54t (0–0.10t)

… …

… …

Single-V-groove butt joint 1.574–3.175 (0.062–0.125) 2.286–3.175 (0.090–0.125) 3.175–6.350 (0.125–0.250)

0–2.54t (0–0.10t) (a) 0–2.54t (0–0.10t)

30–60 90 30–60

2.54–6.35t (0.10–0.25t) … 2.54–6.35t (0.10 –0.25t)

Double-V-groove butt joint 6.350–12.700 (0.250–0.500)

0–5.08t (0–0.20t)

30–120

2.54–6.35t (0.10–0.25t)

Single-U-groove butt joint 6.350–19.050 (0.250–0.750)

0–2.54t (0–0.10t)

15–30

2.54–6.35t(0.10–0.25t)

Double-U-groove butt joint 19.050–38.100 (0.750–1.500)

0–2.54t (0–0.10t)

15–30

2.54–6.35t (0.10–0.25t)

Fillet weld 0.787–3.175 (0.031–0.125) 3.175–12.700 (0.125–0.500)

0–2.54t (0–0.10t) 0–0.54t (0–0.10t)

0–45 30–45

0–6.35t (0–0.25t) 2.54–6.35t (0.10–0.25t)

Base-metal thickness (t), mm (in.)

(a) Root face, 0.76 mm (0.030 in.)

Joining Technology and Practice / 73 erly. In some applications, however, where heavy or long welds are required, gas is supplied to the torch to improve shielding. With flow-purged chambers, the atmosphere is often tested by welding a piece of scrap titanium before making the assembly weld. The color of the solidified weld metal is observed by gradually pulling the torch away from the molten pool. The colors of the weld metal, in increasing order of contamination, are bright silver, light straw, dark straw, light blue, dark blue, gray-blue, gray, and white loose powder. A light straw color is generally considered acceptable for all but the most stringent requirements, although a bright silvery color like a newly minted dime is preferred. To continuously monitor the inert atmosphere, a heated tungsten filament can be placed inside the chamber. Any discoloration or ignition of the filament indicates that the purity of the atmosphere has become degraded. Rigid or collapsible chambers made of transparent plastic can be used when production

Setup for inert gas shielding for gas-tungsten arc welding of titanium alloys outside a welding chamber. Gas shielding is from the torch and through ports in hold-down bars, backing bars, and from trailing and backup shields.

Fig. 9.9

runs are short, the assembly is large or complicated, and when manual welding is required. Rigid plastic chambers are flow-purged before welding is started with argon or helium in volumes equal to five to ten times the volume of the chamber. Collapsible plastic chambers are first collapsed and then flow-purged with argon or helium; they require less gas for purging than do rigid chambers. It is of interest that collapsible plastic chambers were used on the titanium production line of a major gas turbine manufacturer for over 30 years. Advantages of plastic chambers (either rigid or collapsible) are low cost and good visibility of the work. Because there is generally a greater probability of leakage occurring in a plastic chamber than in a metal chamber, the atmosphere must be checked frequently to ensure that it is of proper purity. In addition, torch shielding is usually employed to make certain that the weld zone is adequately protected. Out-of-Chamber Welding. With proper tooling, joints in titanium can be adequately shielded for welding without using a chamber. However, both the weld and the HAZ must be temporarily shielded during welding and until the temperature of the metal in the area of the weld is below 538 °C (1000 °F). If shielding is inadequate, the welds absorb oxygen and become brittle. With the out-of-chamber method, welding can be done manually or automatically using backup shields (Fig. 9.9) or a trailing shield (Fig. 9.10) that provides a diffuse, nonturbulent flow of gas to the solidifying weld. For the typical trailing shield shown in Fig. 9.10, the length of the trailing shield must be adjusted to the speed of welding. Both straight and curvilinear welding can be shielded. In addition, the welding station must be shielded by curtains to prevent drafts. Most shields are designed and/or hand crafted for the particular weld. Stress Relief of Fusion Welds. Most titanium weldments are stress relieved after welding to prevent weld cracking and susceptibility to stress-corrosion cracking in service. Stress relief also improves fatigue strength. An as-

Table 9.3 Material thickness (a), mm (in.)

sembly subjected to a substantial amount of welding and severe fixturing restraint may require intermediate stress relieving of the partially welded structure, which should be done in an inert atmosphere; if not done in an inert atmosphere, the unwelded joints may have to be recleaned before being further welded. With unalloyed titanium and alpha titanium alloys, time and temperature should be controlled to prevent grain growth. Stress-relief times and temperatures for selected titanium alloys are given in Table 8.3. Stress relieving of some beta alloys, such as Ti-13V-11Cr-3Al weldments, can cause aging and subsequent embrittlement of the weld and HAZ and, therefore, is not recommended. Resolution heat treatment (reannealing) can be used to relieve stresses if the welded assembly is amenable to such treatment. Again, it is essential to note that all titanium surfaces should be free of dirt, fingerprints, grease, and residues before stress relieving. Contaminated surface metal must be removed from the entire weldment by machining or descaling and pickling to remove 0.025 to 0.051 mm (0.001 to 0.002 in.) per surface. (See Chapter 11 for additional information.)

Arc Welding Gas-Tungsten Arc Welding. The power supply should include accessories for arc initiation because of the danger of tungsten contamination of the weld if the arc is struck by torch starting. If welding is to be done in air, controls for extinguishing the arc without pulling the torch away from the workpiece are needed so that shielding-gas flow continues and the hot weld metal is not contaminated by air. The conventional thoriated tungsten types of electrodes (EWTh-l or EWTh-2) are used for GTAW of titanium. Electrode size is governed by the smallest diameter able to carry the welding current. To improve arc initiation and to control the spread of the arc, the electrode should be ground to a point. The electrode can

Suggested welding procedure schedule for gas-tungsten arc welding of titanium Tungsten electrode diameter, mm (in.)

Filler rod diameter, mm (in.)

Nozzle size ID, mm (in.)

Shielding gas flow, L/min (ft3/h)

Welding current(b), A

Number of passes

Travel speed(c), mm/min (in./min)

… … 1.6 (1 16) 1.6 (1 16) 3.2 (1 8)

9.5 (3 8) 15.9 (5 8) 15.9 (5 8) 15.9 (5 8) 15.9 (5 8)

8.5 (18) 8.5 (18) 11.8 (25) 11.8 (25) 11.8 (25)

20–35 85–140 170–215 190–235 220–280

1 1 1 1 2

152.4 (6) 152.4 (6) 203.2 (8) 203.2 (8) 203.2 (8)

3.2 (1 8) 3.2 (1 8) 4.0 (5 32)

15.9 (5 8) 19.0 (3 4 ) 19.0 (3 4 )

14.2 (30) 16.5 (35) 18.9 (40)

275–320 300–350 325–425

2 2 3

203.2 (8) 152.4 (6) 152.4 (6)

Square-groove and fillet welds 0.610 (0.024) 1.600 (0.063) 2.362 (0.093) 3.175 (0.125) 4.775 (0.188)

1.6 (1 16) 1.6 (1 16) 2.4 (3 32) 2.4 (3 32) 2.4 (3 32)

V-groove and fillet welds 6.35 (0.25) 9.53 (0.375) 12.70 (0.50)

Fig. 9.10

Shielding arrangement for automatic welding of titanium alloys in air using a trailing shield

3.2 (1 8) 3.2 (1 8) 3.2 (1 8)

Tungsten used for the electrode; first choice 2% thoriated EWTh2, second choice 1% thoriated EWTh1. Use filler metal one or two grades lower than the base metal. Adequate gas shielding is essential not only for the arc, but for heated material also. Backing gas is recommended at all times. A trailing gas shield is also recommended. Argon is preferred. For higher heat input, or thicker material, use argon-helium mixture. Without backing or chill bar, decrease current 20%. (a) Or fillet size. (b) Direct current electrode negative. (c) Per pass

74 / Titanium: A Technical Guide extend one and one-half times the size of the diameter beyond the end of the nozzle. To ensure a diffuse, nonturbulent flow of shielding gas, nozzles of torches for welding titanium are larger than those used for welding other metals. With a 1 32 in. diam electrode, a nozzle with an inside diameter of 9 16 in. is ordinarily used. With a 1 16 in. diam electrode, a nozzle with an inside diameter of 3 4 in. is used. (For metric equivalents, consult the authorized equipment dealer or titanium supplier.) Phenolic or other plastic nozzles should not be used to avoid the danger of contaminating the weld with carbon. Because titanium has low thermal conductivity, the area ahead of the arc does not become heated above 538 °C (1000 °F). Therefore, leading shields are seldom required when welding is done by GTAW. For welding operations where a trailing shield is not adaptable, the nozzle of the torch is fitted with a concentric outer shroud through which a supplementary supply of shielding gas is fed. Shielding of the underside of a weld is provided by slotted backing bars, usually copper, through which a diffuse flow of argon or helium is maintained. Gas channels in the clamping fixtures also provide diffuse flow of inert gas to the weld area. These fixtures are placed close to the weld to avoid the danger of air contamination. Copper fixtures are usually employed for GTAW. Although other metals are used, they should be nonmagnetic; arc blow tends to occur with magnetic metal fixtures. Metal fixtures are sometimes water cooled, but this method introduces the possibility of moisture from the air condensing on the fixtures. Gas-Tungsten Arc Welding of Titanium and Its Alloys. Generally, procedures for GTAW of titanium alloys are similar to those used for austenitic stainless steel. Preheating is not required for titanium alloys. Although cracking can occur in titanium alloy weldments, it is most often related to contamination and cannot be prevented by preheating. Also, maintenance of a specific interpass temperature is not necessary. Preheating from 982 to 1093 °C (1800–2000 °F) can be used to eliminate surface moisture. Rather than an open-flame torch, the usual method is a heat lamp, hot air gun, or infrared heater. Tack welding is used to preposition parts or subassemblies for final welding operations. Table 9.4 plate

Elaborate fixturing often can be eliminated when tack welds are used to their full advantage. Various tack welding procedures can be used, but in any procedure good cleaning practices and adequate shielding must be provided to prevent contamination of the welds. Contamination or cracks developed in tack welds can be transferred to the finish weld. One procedure is to tack weld in such a way that the finish weld never crosses over a previous tack weld. To accomplish this, sufficient filler metal is used in tack welding to completely fill the joint at a particular location. The finish weld beads can then be blended into the ends of the tack welds. Arc length for welding without filler metal (as with stainless steel and the nickel-base alloys) should have a maximum size about equal to the electrode diameter. With longer arc length, there is danger of turbulence, which may draw air into the weld pool. In addition, increasing the arc length produces wider weld beads. When filler metal is used, the maximum arc length should be about one and one-half times the electrode diameter, depending on the thickness of the base metal. Suggested welding conditions or schedules for GTAW of sheet are given in Table 9.3. In welding titanium alloys, the best heat input to use is a temperature just above the minimum required to produce the weld. If heat input is greater, the possibility that the weld will become contaminated, distorted, or embrittled increases. Avoiding porosity in welds is an important consideration in welding titanium alloys. If the joint and filler wire are properly cleaned and the tooling does not chill the weld too rapidly, porosity can be reduced or eliminated by using a slower welding speed. This retards weld solidification and allows entrained gases to escape. Gas-metal arc welding generates the heat for welding by an arc between a consumable electrode and the work metal, whereas GTAW uses a separate tungsten electrode and separately fed filler wire. The GMAW electrode, a bare, solid wire that is continuously fed to the weld area, becomes the filler metal as it is consumed. As in GTAW, it is necessary to protect the filler (electrode), weld pool, arc, and adjacent areas of the base metal from atmospheric contamination by a gaseous shield. This protection is provided by a stream of gas, or mixture of gases, fed through the welding gun. GMAW

Typical conditions for manual and automatic gas-metal arc welding of Ti-6Al-4V

Plate thickness, mm (in.)

Current (DCEP)(a), A

Manual welding 15.875 (0.625) 50.800 (2.00)(b) Automatic welding 15.875 (0.625)(c) 50.800 (2.00)(c)

Argon flow rate, L/min (ft3h)

Voltage, V

Welding speed, mm/min (in./min)

Torch

Trailing

Backing

310 310

38 38

… …

17 (36) 17 (36)

(b) (b)

(b) (b)

360 325

45 33

381 (15) 635 (25)

24 (50) (d)

28 (60) (d)

3 (6) (d)

Welding uses a 0.062 in. diam electrode. (a) DCEP, direct current electrode positive. (b) Not reported. (c) Multiple passes. (d) Argon chamber

overcomes the restriction of using an electrode of limited length and overcomes the inability to weld in various positions. Gas-Metal Arc Welding of Titanium and Its Alloys. GMAW normally is used for welding titanium and titanium alloys 3.18 mm (0.175 in.) or more in thickness. This process is frequently used for welding 12.7 mm (0.5 in.) plate. There are some concerns with GMAW. Metal transfer through the arc in GMAW can lead to difficulty in meeting stringent aerospace quality requirements. For example, weld spatter is often associated with inferior weld quality and arc instability. It is a potential cause of weld contamination and defect formation. Some users of titanium alloys prefer GTAW to GMAW (even for joining thick plate) because with the GTAW process, more uniform and predictable transverse shrinkage is obtained. Typical conditions for GMAW of Ti-6A-4V and Ti-5Al-2.5Sn plate are given in Tables 9.4 and 9.5. Electrode wires for GMAW are available in several grades of unalloyed titanium and titanium alloys that match the composition of the base metal. Joint preparation is the same as in Table 9.3. Shielding for out-of-chamber GMAW is provided by inert gas being fed through the nozzle of the electrode holder, through the backing bar or plate, and as a trailing shield, much as in GTAW (Fig. 9.2). The electrode holder is basically the same as the GMAW of steel. To avoid contamination and porosity in GMAW, a leading shield is necessary, as well as a trailing shield and a suitable baffle added on the leading edge of the electrode holder (Fig. 9.2). A leading shield prevents oxidation of spatter before it is melted in the weld metal. Plasma arc welding generates heat by a constricted arc between an electrode and a workpiece (transferred arc), or between a nonconsumable tungsten electrode and a constricting orifice (nontransferred arc). Shielding generally is obtained from the hot, ionized gas issuing from the orifice of the constricting nozzle, which may be supplemented by an auxiliary source of shielding gas. Shielding gas can be an inert gas or a mixture of gases. PAW is closely related to GTAW. Table 9.5 Typical conditions for gas-metal arc welding of Ti-5Al-2.5Sn 12.7 mm ( 12 in.) thick plate Condition

Electrode wire Wire-feed rate Current Voltage Nozzle Backing bar Shielding gas flow At torch Trailing Backing Welding speed

Description

1.6 mm (1 16 in.) diam ERTi-5Al-2.5Sn 7620 mm/min (300 in./min) 300 A (DCEP)(a) 30 V 25.4 mm (1 in.) inside diameter Copper, with 1.6 mm (1 16 in.) deep by 6.4 mm (1 4 in.) wide groove Argon, at 24 L/min (50 ft3/h) Argon, at 24 L/min (50 ft3/h) Helium, at 9 L/min (20 ft3/h) 508 mm (20 in./min)

(a) DCEP, direct current electrode positive

Joining Technology and Practice / 75 Plasma Arc Welding of Titanium and Its Alloys. The joining of titanium alloys is one of the major applications of PAW. Because titanium has a lower density, keyhole welds can be made through thicker titanium square butt joints than for steel. As with GTAW, PAW requires backing gas and a trailing gas shield to prevent atmospheric contamination of the weld and adjacent weld metal. Typical operating conditions for PAW of titanium alloys are given in Table 9.6. Procedures for Repair of Arc Welds. Repair welds should follow the established specification requirements for the original welds and be made prior to final heat treatment. Manual or automatic GTAW is generally used for repairing butt and fillet welds. Repairs can also employ a combination of welding processes, such as GTAW and the initial welding process (GMAW or PAW). Repair welds always must be carefully executed, and all traces of liquid-penetrant inspection material must be removed. Generally, inspection is performed on both faces of the repair weld and several inches beyond the repaired area. Repair welds to correct fabrication weld deficiencies should not be confused with repair welding done in the casting industry where casting defects are being corrected.

Electron Beam, Laser Beam, and Resistance Spot Welding Electron Beam Welding. One of the prime advantages of EBW is the ability to make welds that are deeper and narrower than arc welds, with a total heat input that is much lower than that required in arc welding. This ability to achieve a high depth-to-width ratio for the weld eliminates the need for multiple-pass welds, as is required in arc welding. The lower heat input results in a narrow workpiece HAZ and noticeably fewer thermal effects on the workpiece. Equipment costs for EBW generally are higher than those for conventional welding processes. However, when compared to other types of high-energy density welding (such as LBW), production costs are not as high. The cost of joint preparation and tooling is more than that encountered in arc welding processes because of the relatively small electron beam spot size that is used requires precise joint gap and position.

Table 9.6 Thickness, mm (in.)

3.175 (0.125) 4.750 (0.187) 9.906 (0.390) 12.700 (0.500) 15.240 (0.600)

Electron Beam Welding of Titanium and Its Alloys. All of the commercial alloys of titanium that can be joined by arc welding can also be joined by EBW. Their relative weldability and response to heat cycling in EBW are generally the same as in arc welding. The vacuum environment of EBW prevents exposure to the atmospheric contaminants that cause embrittlement of titanium alloys, whereas arc welding processes must use elaborate and costly shielding methods to accomplish this. Cost studies show that direct labor costs for EBW of titanium sections more than 25.4 mm (1 in.) thick are less than for arc welding, provided a suitably large vacuum chamber is available. Filler metal is not ordinarily used, and the work is not preheated. Tack welding, contrary to experience in GTAW, presents no difficulties in EBW. For optimum results, welding is done in a high vacuum, but medium-vacuum welding is satisfactory for many applications. Nonvacuum welding is not a preferred technique. Ti-6Al-4V, the alloy most frequently used in assemblies to be welded, can be electron beam welded in either the annealed or solutiontreated-and-aged condition. For weldments that will be used at elevated temperatures, a preferred process sequence is anneal, weld, solution treat, and age. For other service conditions, a process sequence of solution treat, age, and weld gives almost the same strength properties and only slightly lower fracture toughness. Laser Beam Welding. The application of the laser technique to a metal such as titanium alloy, which requires extreme cleanliness for attainment of sound welds, is of great interest to the aerospace and chemical industries. The importance and the need for better joining methods for titanium lead to the use of LBW techniques. Laser Beam Welding of Titanium and Its Alloys. During the past decade, LBW has become increasingly competitive as a joining process for titanium sheet and thin plate. In LBW, melting of the workpieces is produced by the impingement of a high-intensity, coherent beam of light. Because the laser beam can be readily transmitted through air, the LBW process offers significant practical advantages over conventional EBW, which requires welding in a high vacuum. However, the LBW process is more limited than EBW from the standpoint of joining thick titanium plate, with 15

Typical conditions for plasma arc welding of titanium alloys

kW required to produce a full-penetration weld in 13 mm (0.5 in.) thick Ti-6Al-4V. The relationship between LBW parameters and the metallurgical and mechanical properties of laser-welded Ti-6Al-4V and CP titanium was studied. Welding speeds in excess of 15.24 m/min (50 ft/min) were obtained for 1.02 mm (0.04 in.) thick Ti-6Al-4V using 4.7 kW of laser power. X-ray radiographs of successful laser butt welds of Ti-6Al-4V and CP titanium show no cracks, porosity, or inclusions. Low porosity in a laser-welded titanium alloy was also observed, and radiographically sound welds were produced. Undercutting was not prominent. Resistance Spot Welding. Resistance welding, which is another fusion welding process, occurs when heat is generated by resistance to electrical current at two surfaces in contact with each other. When heat is generated, the metal melts in the vicinity of the current flow. Pressure keeps the faces together. When the current is interrupted, a solidified weld nugget is formed. The nugget is contained within the metal being joined and does not reach an external surface. When done locally, a spot results—hence, “spot welding.” When spots overlap, the result is resistance seam welding. The thickness of metal that can be joined by resistance welding is a function of the base alloy together with the actual chemistry. Spotwelded lap joints have been made up to a total thickness in excess of 12.7 mm (0.5 in.) of steel; however, resistance welding of thick stock is generally not economical. Resistance Spot Welding of Titanium Alloys. Titanium alloy sheet can be resistance welded. The thermal conductivity of titanium alloys compares favorably with the conductivity of stainless steel. The processing techniques for titanium alloys are similar to those used to weld stainless. It is claimed that spot and seam welding do not require inert gas shielding because electrode pressure excludes air and also because there is a very short weld duty cycle. Inevitably there is some oxygen pickup; however, even when fully cleaned surfaces are resistance welded, properties of resistance welded joints made in air are not as good as those made with a shielding gas. During spot welding operation, an oxide film can form around the weld area of the touching surfaces of the sheet. With respect to seam welding, it is claimed that the speed of continuous welding and the pressure prevent film formation ahead of the weld. If a nugget dissolves an oxide film, the ductility of the weld is reduced.

Gas flow, L/min (ft3/h)

Travel speed, mm/min (in./min)

Current (DCEN)(a), A

Arc voltage, V

Gas

Orifice gas

Shielding gas

Joint type

508 (20) 330 (13) 254 (10) 254 (10) 178 (7)

185 175 225 270 250

21 25 38 36 39

Argon Argon 75He-25A 50He-50A 50He-50A

4 (8) 8 (18) 15 (32) 13 (27) 14 (30)

28 (60) 28 (60) 28 (60) 28 (60) 28 (60)

Square butt Square butt Square butt Square butt V-groove(b)

Backing gas and trailing shield required; keyhold technique used with orifice-to-work distance of 4.76 mm (3 16 in.). (a) DCEN, direct current electrode negative. (b) 30° included angle; 9.53 mm (3 8 in.) root face

Some Fusion Welding Process Comparisons Electron Beam Welding, Laser Beam Welding, and Plasma Arc Welding for Titanium Alloys. A comparative study of EBW, LBW, and PAW applied to Ti-6Al-4V alloy

76 / Titanium: A Technical Guide was conducted. Radiographically sound welds were produced by all three techniques. EBW joints were produced by all three EBW techniques. EBW produced joints that were quite narrow and exhibited a somewhat nonuniform radiographic appearance due to lower surface weld spatter, whereas the PAW joints were considerably broader but also quite uniform in density. LBW produced narrower joints than arc welds did, and the LBW joints were comparable to, but more uniform than, EBW joints. Following stress relieving for 2 h at 538 °C (1000 °F), the welds produced by all three techniques had tensile strengths equivalent to or exceeding those of the base metal. Electron Beam Welding versus Laser Beam Welding for Titanium Alloys. The EBW technique has been used more frequently than LBW for the welding of Ti-6Al-4V, an alloy widely used in the aerospace industries for its high strength-to-weight ratio. However, the deep penetration of EBW can be obtained only up to a short distance under nonvacuum conditions. For optimum efficiency, EBW is carried out in an evacuated chamber. In contrast, CO2 laser beams can be transmitted for appreciable distances through the atmosphere without serious attenuation or optical degradation. Thus, the laser offers an easily maneuvered, chemically clean, high-intensity, atmospheric welding process that produces deep-penetration welds (aspect ratio greater than 1:1) with a narrow HAZ and subsequent low distortion.

Solid-State Welding Practice A wide variety of specialized solid-state welding processes have been used to join titanium, including flash welding (FW), diffusion bonding, continuous-drive and inertia friction welding, ultrasonic welding, and explosive welding. In general, these processes have been effective, producing defect-free joints with properties that depend principally on the cooling rates from high temperatures and the characteristics of the resulting transformed-beta microstructure. A limited number of solid-state welding processes are in use for titanium and its alloys. Flash welding commonly is used to join sections of metals and alloys in production quantities. It is a resistance-forge welding process in which the items to be welded are securely clamped to electric current-carrying dies, butted together, heated by the electric current, and then upset to squeeze out any molten metal present. The resultant joint is made between two solid surfaces. Flash Welding of Titanium Alloys. An inert gas shield is needed to prevent embrittlement of titanium alloys. Appropriate flash schedules or welding schedules must be developed for each alloy to be welded. While not the major technique for weld processing, at least with respect to aerospace alloys, flash welding has been used for alloys such as CP Ti,

Ti-6Al-4V, Ti-8Al-1Mo-1V, Ti-5Al-2.5Sn, Ti-6Al-2n-4Zr-2Mo, and Ti-6Al-2Sn-4Zr-6Mo. Diffusion bonding (DB), at times called diffusion welding, has found significant application for the fabrication of complex titanium alloy components. DB is a solid-state welding process in which the surfaces are placed in proximity under a moderate pressure at an elevated temperature. Coalescence occurs across the interface. Prerequisites for accomplishing bonding include a clean and smooth surface combined with a low applied pressure and moderate-to-high temperatures. Because DB requires heat and pressure, plus a vacuum, inert gas, or reducing atmosphere, DB equipment is frequently custom built by the user. Surface cleanliness is essential to DB. Prior surface deformation⎯by scratch brushing, for example⎯can be beneficial. Cleanliness must be maintained up to and including the application of heat and pressure. In many instances no intermediate layer is required to effect satisfactory DB. In other cases, intermediate layers of foil (or some sort of surface activation) may be necessary to develop a sound bond. Recrystallization can occur across the bond line, but it is not necessary for achieving a full-strength joint. There is no gross deformation of the parts being joined by DB. Stop-off can be used with this technique to prevent a specific portion of the bond line from being welded. Under actual shop conditions, surface contaminants are invariably present, and, depending on the materials being joined, mechanisms must exist for dispersion of contaminants away from, or into, localized areas on the faying surface. Metals that have a high solubility for such interstitial contaminants as oxygen can easily accommodate removal of these contaminants from the faying surfaces by assimilation into the base metal through volume diffusion. Thus, the surface is decontaminated during welding by diffusion. Metals such as titanium fall into this class and are among the easiest to diffusion bond. DB is usually performed at a bonding temperature equal to, or greater than, one-half the melting temperature of the material being welded. However, the choice of welding temperature is strongly influenced by the time required for surface contaminants to diffuse away, the tendency to weld above or below a phase transformation, and the amount of load available at the faying surfaces. Diffusion Bonding of Titanium Alloys. More DB has been conducted on titanium and its alloys than any other material. Titanium DB was readily accepted for production applications for several reasons:

• The yield and creep strengths of titanium are •

low at welding temperatures, thus enhancing the DB process. Most titanium structures or components are high-technology items used in aerospace applications, and extra costs for DB can be justified based on improved performance.

Diffusion bonding of Ti-6Al-4V is generally performed at temperatures ranging from about 900 to 950 °C (1650–1740 °F), at pressures ranging from 1.3 to 13.8 MPa (200–2000 psi), and for times ranging from about 1 to 6 h. In combination with superplastic forming, DB has been used to produce a wide variety of complex Ti-6Al-4V shapes, such as honeycomb panels for aerospace applications. (See the following section “Superplastic Forming Diffusion Bonding of Titanium Components” in this Chapter.) An example of DB involves the production of Ti-6Al-4V alloy turbofan aircraft engine disks with hollow hubs. Figure 9.11 shows a schematic illustration of the disk profile, including the location of the diffusion welds. Figure 9.12 shows the hot press used for bonding. Fabrication of this disk by diffusion bonding resulted in joint properties equivalent to the base metal and a weight savings of 47.25 kg (105 lb), or approximately 30%, without sacrificing stiffness or durability. Other titanium alloys that have been successfully diffusion welded include: Ti-8Al-1Mo-1V, Ti-13V11Cr-3Al, Ti-8Mo-8V-3Al-2Fe, Ti-6Al-6V2Sn, Ti-6Al-2Sn-4Zr-6Mo, and Ti-11.5Mo6Zr-4.5Sn. As many as 66 different titanium components were fabricated successfully by DB for use in the United States Air Force B-1 bomber. Very large parts were fabricated in this manner. Figure 9.13 shows a wing carry-through section that contains 533 individual parts that were diffusion welded together. A 61 m (200 ft) diam titanium alloy chamber for the zero gradient

• Titanium and its alloys have a high solubility •

for interstitial oxygen and can assimilate contaminant films into the bulk material during welding. Conventional fusion welds in titanium are not as strong as the base metal, whereas titanium diffusion welds possess properties equivalent to the base metal.

Fig. 9.11

Diffusion welds in hollow fan hub for a gas turbine engine

Joining Technology and Practice / 77

Fig. 9.13 Fig. 9.12

Vacuum hot press used for diffusion bonding of turbofan disks and/or hubs. Courtesy of Pratt & Whitney Aircraft Group

synchrotron at Argonne National Laboratory also was produced by DB. Superplastic Forming Diffusion Bonding of Titanium Components. Superplastic forming (see Chapter 5) of titanium plate and sheet was developed as a reduced-cost method for processing of material. A combination of superplastic forming and diffusion bonding (SPFDB) has been used on titanium to produce complex structures. An example of SPFDB is the bonding of three Ti-6Al-4V sheets and, in the same single operation, their expansion to form an integrally stiffened structure. An illustration of this technique is shown in Fig. 9.14 in a variety of specific applications. Figure 9.14(a) shows the method described in

Fig. 9.14

Wing carry-through fabricated by diffusion bonding of 533 individual details. Courtesy of Rockwell International Corp.

the preceding paragraph. The application shown in Fig. 9.14(c) requires that three cleaned and treated alloy sheets be created. Two are treated with stop-off at the indicated points. A third sheet is inserted between them. The edges are welded to exclude air, but a pipe is attached for later pressurization. Initial bonding occurs under pressure at temperature and then internal pressure, through the pipe, causes superplastic flow of the bottom two sheets to fill the die and create the configuration shown. For some years now, SPFDB has been used to produce an extraordinary rotating part for gas turbine engines. A hollow fan blade of convoluted configuration (Fig. 9.15) was created using vacuum DB along with superplastic forming of Ti-6Al-4V alpha-beta alloy. These

Basic shapes of superplastically formed, diffusion-bonded structures. (a) Reinforced sheet; one sheet. (b) Integrally stiffened structure; two sheets. (c) Sandwich; multiple sheets

types of blades currently are in use for commercial large aircraft gas turbines and are flying in preproduction models of the military gas turbine engine for the F-119. Argon pressures needed to effect the superplastic forming are less than 6.9 MPa (1000 psi).

Brazing Practice Brazing, the third broad category of joining, is the bonding of metal that occurs when a high-temperature filler is allowed to melt and flow into a joint by capillary action before the filler solidifies. For reactive metals such as titanium, brazing processes should be used that do

Fig. 9.15

Hollow shroudless fan blade produced by superplastic forming and diffusion bonding

78 / Titanium: A Technical Guide Table 9.7 Type

Filler metals for brazing titanium Form

10Pd-Ag

Prealloyed ring

95Ag-5Al

Powder, wire, foil Powder, wire, foil Foil Powder, foil

9Pd-9Ga-Ag 3003 Al 15Cu-15Ni-Ti 20Cu-20Ni-Ti

48Zr-48Ti-4Be Powder, ring 48Zr-48Ti-4Be Powder with 2% Ni 76.5Al-16.5Cu- Foil, wire, 4.0Sn-3.0Si powder

Description

Douglas developed— no brittle intermediate layer Considered ductile Furnace braze at 870 °C (1600 °F) ductile Considered ductile Brittle when used only as a braze, useful diffusion bonding mechanism Brittle but strong Brittle but strong Developed for bicycle and aerospace furnace braze at 730 °C (1350 °F), ductile

not allow joint surfaces to come in contact with air during heating. Because titanium can become embrittled by the interstitial absorption of hydrogen, nitrogen, and oxygen gases, brazing should be done in a vacuum. Induction and furnace brazing in inert gas or vacuum atmospheres can be used successfully, but torch brazing is difficult and requires special precautions and techniques. Induction brazing of small, symmetrical parts is very effective, because its speed minimizes reaction between braze filler metal and base metal. Furnace brazing is favored for large parts, because uniformity of temperature throughout the heating and cooling cycle can be readily controlled. Brazing Titanium Alloys. Argon, helium, and vacuum atmospheres are satisfactory for brazing titanium. For torch brazing, special fluxes must be used on the titanium. Fluxes for titanium are primarily mixtures of fluorides and chlorides of the alkali metals, sodium, potassium, and lithium. Vacuum and inert gas atmospheres protect titanium during furnace and induction-brazing operations. Titanium assemblies frequently are brazed in high-vacuum, cold-wall furnaces. A vacuum of l0–3 torr or more is required to braze titanium. Ideally, brazing should be done in a vacuum at a pressure of about 10–5 to 10–4 torr or done in a dry inert gas atmosphere if vacuum brazing is not possible. However, a dew point of –21 °C (–70 °F) or less is necessary to prevent discoloration of the titanium in a brazing temperature range of 760 to 927 °C (l400–1700 °F). Braze Process Selection. Selection of filler metals and brazing cycles that are compatible with the heat treatment required for alpha-beta and beta titanium-base metals can present some

Fig. 9.16

Brazed titanium honeycomb-sandwich aerospace assembly

difficulty. Ideally, brazing should be conducted from 38 to 66 °C (100–150 °F) below the beta transus. When titanium is brazed, precautions must be taken to ensure that the brazing retort or chamber is free of contaminants from previous brazing operations. Mechanical properties of titanium can deteriorate because of gaseous contamination from the brazing furnace. Also, the choice of materials to be used in fixtures must be carefully considered. Nickel, or materials containing high amounts of nickel, generally should be avoided; nickel and titanium form a low-melting eutectic (28.4 wt% Ni) at about 942 °C (1728 °F). If titanium workpieces come in contact with fixtures or a retort made of a nickel-base alloy, the parts can fuse together if the brazing temperature exceeds 942 °C (1728 °F). If a fixture material such as stainless steel, which may contain a high nickel content, is used, it should be oxide coated. In most applications, coated graphite or carbon steel fixture materials are used. Braze Filler Metals. Some compositions of filler metals for brazing titanium alloys are shown in Table 9.7. Braze filler metals initially used for brazing titanium and its alloys were silver with additions of lithium, copper, aluminum, or tin. Most of these braze filler metals were used in low-temperature applications from about 538 to 593 °C (1000–1l00 °F). Commercial braze filler metals, including Ag-Pd, Ti-Ni, Ti-Ni-Cu, and Ti-Zr-Be are now available. These can be used in the 871 to 927

°C (1600–1700 °F) range. Although silver-base brazing alloys are most often used, some United States Air Force and NAVAIR specifications restrict their use. Higher strengths and improved resistance to crevice-type corrosion are desirable characteristics that current braze filler metals enjoy. For joining applications requiring a high degree of corrosion resistance, the 48Ti-48Zr-4Be and 43Ti-43Zr-12Ni-2Be braze filler metals were developed. An Ag-Pd-Ga braze filler metal (Ag-9Pd-9Ga), which flows at temperatures of 899 to 913 °C (1650–675 °F), is an excellent filler metal with which to fill large gaps. In general, aluminum-silicon filler metals are unsuitable for brazing aluminum to uncoated titanium due to the formation of brittle intermetallic compounds. Titanium can be hot-dip coated with aluminum, however, after which it can be brazed to aluminum with the usual aluminum filler metals. Methods to braze titanium honeycomb-sandwich assemblies with aluminum braze filler metal were developed. A typical titanium honeycomb assembly used for aircraft structures is shown in Fig. 9.16. Aircraft structures up to 7 m (23 ft) in length were brazed successfully using 3003 brazing foils. Use of aluminum brazing filler metal (3003) provided satisfactory strength up to about 316 °C (600 °F). If temperatures of 538 to 593 °C (1000–1l00 °F) are required, high-strength, corrosion-resistant Ti-Zr-Be or Ti-Zr-Ni-Be braze filler metals should be used

Titanium: A Technical Guide Matthew J. Donachie, Jr., p79-84 DOI:10.1361/tatg2000p079

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 10

Machining The term machining has broad application and refers to all types of metal removal and cutting processes. Conventional machining methods include turning, face milling, peripheral end milling, and climb cutting; drilling; tapping; reaming; wheel grinding, belt grinding, abrasive cutting, and hand abrasive grinding; hack sawing; and band sawing. Widely used nontraditional methods include electrochemical machining (ECM), chemical milling (CHM), and laser beam machining (LBM). Titanium once was perceived as a material that is difficult to machine. A broad base of titanium machining knowledge now exists, and manufacturers know that with proper procedures titanium can be fabricated using techniques comparable to those used for machining 316 stainless steel. Machining of titanium alloys requires cutting forces only slightly higher than those needed to machine steels, but titanium alloys do have

Fig. 10.1

Cutting resistance of various titanium alloys

metallurgical characteristics that make them more difficult and, consequently, more expensive to machine than steels of equivalent hardness. Reasonable production rates and excellent surface finish can be obtained with conventional machining methods if the unique characteristics of this metal (such as its reactivity) are taken into account. Figure 10.1 shows the cutting resistance of selected titanium alloys. The alloy types vary from alpha to near-alpha to alpha-beta to beta as one views Fig. 10.1 from left to right. Notice that the cutting forces increase from left to right and that the beta alloys are the most difficult titanium alloys to machine. When machining conditions are selected properly for a specific alloy composition and processing sequence, reasonable production rates of machining for titanium and its alloys can be achieved at acceptable cost levels. Table 10.1 shows machinability comparisons of several titanium alloys with other materials (higher

numbers indicate improved/lower-cost machinability). Success in machining titanium Table 10.1 Machinability comparisons of several titanium alloys with other materials Alloy

Aluminum alloy 2017 B1112 resulfurized steel 1020 carbon steel 4340 alloy steel Commercially pure titanium 302 stainless steel Ti-5Al-2.5Sn Ti-6Al-4V Ti-6Al-6V-2Sn Ti-6Al-4V HS25 (Co-base) René 41 (Ni-base)

Condition(a)

Machinability rating(b)

STA HR CD A A A A A A STA A STA

300 100 70 45 40 35 30 22 20 18 10 6

(a) STA, solution treated and aged; HR, hot rolled; CD, cold drawn; A, annealed. (b) Based on a rating of 100 for B1112 steel

80 / Titanium: A Technical Guide depends largely on overcoming several of its inherent properties, which are described in the following sections. Heat Conduction. Titanium is a poor conductor of heat. Heat, generated by the cutting action, does not dissipate quickly. Therefore, most of the heat is concentrated on the cutting edge and the tool face. Tool life is adversely affected. Alloying Tendency. Titanium has a strong alloying tendency, or chemical reactivity, with materials in the cutting tools at tool operating temperatures. This causes welding to the tool during the machining operation and consequent galling, smearing, and chipping of the machined surface, along with rapid destruction of the cutting tool. Elastic Modulus. Titanium has a lower elastic modulus than steel and superalloys and thus has more “springiness” than these metals. The result is greater deflections of a workpiece. Proper backup may be required to improve stiffness. Rigidity of the entire system is consequently very important, as is the use of sharp, properly shaped cutting tools. Greater clearances of cutting tools are also required due to these deflections. Surface Damage Susceptibility. Titanium and its alloys are susceptible to surface damage during machining operations; this is particularly true during grinding. Titanium alloys are less forgiving of surface defects in fatigue-limited operations than are some metals. Care must be exercised to avoid the loss of surface integrity, especially during grinding, because even properly conducted grinding operations can result in surfaces that appreciably lower fatigue life. Maintaining a sharp tool during machining is very critical to optimize fatigue life in titanium. Work Hardening Characteristics. The work hardening characteristics of titanium are such that its alloys demonstrate a complete ab-

sence of “built-up edge.” The lack of a built-up edge ahead of the cutting tool causes changes that result in an increase in heat on a very localized portion of the cutting tool. High bearing forces are also produced, and the combination of heat and force results in rapid tool breakdown.

•

Although the basic machining properties of titanium metal cannot be altered significantly, their effects can be greatly minimized by decreasing temperatures generated at the tool face and cutting edge. Economical production techniques have been developed through application of the previously mentioned basic rules in machining titanium. Tool Life. Tool life data have been developed experimentally for a wide variety of titanium alloys. A common way of representing such data is shown in Fig. 10.2, where tool life (as time) is plotted against cutting speed for a given cutting tool material at a constant feed and depth in relation to Ti-6Al-4V. It can be seen that tools for machining titanium alloys are very sensitive to changes in feed. At a high cutting speed, tool life is extremely short; as the cutting speed decreases, tool life dramatically increases. Industry generally operates at cutting speeds promoting long tool life. Forces and Power Requirements. Cutting force is important because, when multiplied by the cutting velocity, it determines the power requirements in machining. For general approximations, the power requirements in turning and milling can be obtained by measuring the power input to the drive motor of the machine tool during a cutting operation and by subtracting from it the tare, or idle power. A good approximation of the horsepower required in most machining operations can be predicted from unit power requirements. Table 10.2 shows the power requirements for titanium in comparison with other alloys. Tool Materials. Cutting tools used to machine titanium require abrasion resistance and adequate hot hardness. Despite the use of new tool materials—such as special ceramics, coated carbides, polycrystalline diamonds, and cubic boron nitride—in metal removal of steels, cast irons, and heat-resistant alloys, none of these newer developments have found application in increasing the productivity of titanium machined parts. Generally, only straight carbide and general-purpose high-speed or highly alloyed tool

Traditional Machining of Titanium The technology supporting the machining of titanium alloys is basically very similar to that for other alloy systems. Efficient metal machining requires access to data relating the machining parameters of a cutting tool to the work material for the given operation. The important parameters include:

• • • •

Tool life Forces Power requirements Cutting tools and fluids

Guidelines. The following guidelines, based in large part on the inherent factors affecting the machinability of titanium described above, contribute to the efficient machining of titanium:

• Use low cutting speeds: A low cutting speed

•

• • •

dwell when it is in moving contact with titanium causes work hardening and promotes smearing, galling, and seizing. This can lead to a total tool breakdown. Use rigid setups: Rigidity of the machine tool and workpiece ensures a controlled depth of cut.

helps to minimize tool edge temperature and maximize tool life. Tool tip temperature is strongly affected by cutting speed. Lower speeds are required for alloys such as Ti-6Al-4V than are necessary for unalloyed titanium. Maintain high feed rates: The highest rate of feed consistent with good practice should be used. Tool temperature is affected less by feed rate than by speed. The depth of each succeeding cut should be greater than the work-hardened layer resulting from the previous cut. Use a generous quantity of cutting fluid: A coolant provides more effective heat transfer. It also washes away chips and reduces cutting forces, thus improving tool life. Maintain sharp tools: Tool wear results in a buildup of metal on the cutting edges and causes poor surface finish, tearing, and deflection of the workpiece. Never stop feeding while tool and titanium are in moving contact: Allowing a tool to

Table 10.2 Average unit power requirements for turning, drilling, or milling of titanium alloys compared with other alloys systems Unit power for sharp tools (a), hp/in.3 per min Material

Steels Titanium alloys High-temperature nickel and cobalt-base alloys Aluminum alloys

Fig. 10.2 alloy

Effect of cutting speed and feed on tool life during the turning of Ti-6Al-4V alpha-beta

Hardness, HB (3000 kg)

Turning HSS and carbide tools

Drilling HSS drills

Milling HSS and carbide tools

35–40 HRC 250–375 200–360

1.4 1.2 2.5

1.4 1.1 2.0

1.5 1.1 2.0

30–150 (500 kg)

0.25

0.16

0.32

(a) Power requirements at spindle drive motor, corrected to 80% spindle drive efficiency. Dull tools may require 25% more power. HSS, high-speed steel

Machining / 81 steels can be used. Carbide tools (such as grades C-2 and C-3), if feasible, optimize production rates. General-purpose high-speed tool steels (such as grades Ml, M2, M7, and M10) also are used. However, better results are generally obtained with more highly alloyed tool steel grades, such as T5, T15, M33, and the M40 series. Cutting tool performance is influenced by many factors. Setup, processing methods, grinding techniques, material quality, and the condition of the machine tool and fixturing all influence cutter performance. In early studies, the straight tungsten carbide cutting tools, typically C-2 grades, performed best in operations such as turning and face milling, while the high-cobalt, high-speed steels were most applicable in drilling, tapping, and end milling. The situation remains much the same today. C-2 carbides are used extensively in engine and airframe manufacturing for turning and face milling operations. Solid C-2 end mills and end mills with replaceable C-2 carbides find application, particularly in aerospace plants. M7 and the M42 and M33 high-speed steels are recommended for end milling, drilling, and tapping of titanium alloys. Cutting Fluids. The correct use of coolants during machining operations greatly extends cutting tool life, and this is particularly true for titanium alloys. Chemically active cutting fluids transfer heat efficiently and reduce cutting forces between tool and workpiece. Of course, cutting fluids should not cause any degradation of the properties of the workpiece. Chlorine at one time was considered a suspect element in cutting fluids, regardless of the concentration and specific conditions used in titanium alloy manufacturing operations. The aversion to cutting fluids containing chlorine was based on the early discovery of hot-salt stress-corrosion damage in titanium alloys through mechanical property studies (see Chapter 13) and on the unexpected cracking of titanium alloys in cleaning and heat-treatment operations. Although the presence of chlorine ions (e.g., those found in fingerprints on a part) can cause stress corrosion in some alloys during processing, it is not thought to always damage titanium alloys during machining. Nevertheless, cutting fluids used in machining titanium alloys require special consideration. If chlorinated cutting fluids are used on alloys that may be subject to stress-corrosion cracking, carefully controlled postmachining cleaning operations must be followed. The general prohibition against the use of cutting fluids containing chlorine is not universally observed. When specifying cutting fluids for machining titanium, some companies have practically no restrictions other than the use of controlled-washing procedures on parts after machining. Other manufacturers do likewise, except that they do not use cutting fluids containing chlorine on parts that are subjected to higher temperatures in welding processes or in service. Also, when assemblies are machined, the same restrictions apply due to the difficulty of doing a good cleaning job after

machining. Still other organizations in aerospace manufacturing permit no active chlorine in any cutting fluid used for machining titanium alloys. Mechanical property evaluations to define the effect of experimental chlorinated and sulfurized cutting fluids on Ti-6Al-4V alloy indicated that no degradation of mechanical properties relative to those obtained from neutral cutting fluids occurred. Similar results were obtained by using chlorinated and sulfurized fluids in machining, or by having those cutting fluids present as an environment during testing. These results and others suggest that under certain conditions, chlorine-containing cutting fluids are not detrimental to titanium alloys. Usually the heavy chlorine-bearing fluids excel in operations such as drilling, tapping, and broaching. The use of chlorine-containing (or halogen-containing) cutting fluids generally is not a recommended practice, however. There are excellent cutting fluids available that do not contain any halogen compounds. Actually, for certain alloys and operations, dry machining is preferred. Figure 10.3 shows the effect of various cutting fluids on tool life in drilling Ti-6Al-4V. Machining Speeds and Feeds. Cutting speed and feed are two of the most important parameters for all types of machining operations. Table 10.3 gives some speed and feed data on turning of selected titanium alloys. Because speed and feed rates have a direct influence on tool life, it is desirable to have charts or graphs for all possible tool and titanium alloy combinations, as well as machining techniques. Considering the range of alloys, tool compositions, and machining techniques possible, such charts are not likely to be available for all situations. However, charts such as Table 10.3 have been compiled for some other machining techniques. (See Appendix G for more detailed information on machining of titanium and its alloys.) Machining recommendations, such as noted above in Table 10.3 and similar sources, can require modification to fit particular circumstances in a given shop. For example, cost, storage, or other requirements can make it impractical to accommodate a very large number of different cutting fluids. Savings achieved by making a change in cutting fluid can be offset by the cost of changing fluids. Likewise, it might not be economical to inventory cutting tools that have only infrequent use. Furthermore, the design of parts can limit the rate of metal removal in order to minimize distortion (e.g., of thin flanges) and to corner without excessive inertia effects. An illustration of typical machining parameters used to machine Ti-6Al-4V bulkheads containing deep pockets, thin flanges, and floors at an airframe manufacturer is given in Table 10.4. A bulkhead frequently contains numerous pockets and some flanges as thin as 0.76 mm (0.030 in.). Typical bulkhead rough forgings can weigh in excess of 450 kg (1000 lb), but the finished part is less than 67.5 kg

(150 lb) after machining. Extensive machining is done on gas turbine engine components, just as is done on the larger airframe components. Table 10.5 lists typical parameters for machining Ti-6Al-4V jet engine components, such as fan disks, spacers, shafts, and rotating seals. Increased Productivity with Special Techniques. The inability to improve cutting tool performance for titanium alloys by developing new cutting tool materials—coatings in particular—has been very frustrating. Likewise, very little improvement in productivity has been experienced by exploring new combinations of speeds, feeds, and depths. Some developments of interest include specially designed turning tools and milling cutters, along with the use of a special end-mill pocketing technique. One of the practical techniques for increasing productivity is to determine the optimum cost in machining a given titanium part for a specific machining operation. If specific data are available relating tool life to speed, feed, and depth for a given operation and cutter, it is possible to calculate the overall cost and time of machining as a function of the cutting parameters. Some companies are using computers to perform such cost analyses and to arrive at minimum costs and optimum production rates for specific machining operations. Fire Prevention. Fine particles of titanium can ignite and burn. Use of water-base coolants or large volumes of oil-base coolants generally eliminates the danger of ignition during machining operations. However, an accumulation of titanium fines can pose a fire hazard. Chips, turnings, and other titanium fines should be collected regularly to prevent undue accumulation and should always be removed from machines at the end of the day.

Effect of various cutting fluids and speeds on tool life when drilling Ti-6Al-4V (375 HB). HSS, high-speed steel

Fig. 10.3

82 / Titanium: A Technical Guide Salvageable material should be placed in covered, labeled, clean, dry, steel containers and stored, preferably in an outside yard area. Unsalvageable fines should be properly disposed. Titanium sludge should not be permitted Table 10.3

to dry out before being removed to an isolated, outside location. Dry powders developed for extinguishing combustible metal fines are recommended for the control of titanium fires. For maximum

safety, such extinguishers should be readily available to each machinist working with titanium. Dry sand retards, but does not extinguish, titanium fires. Carbon dioxide and chlorinated hydrocarbons are not recommended.

Nominal speeds and feeds for turning titanium and titanium alloys with high-speed tool steel and carbide tools Carbide tool, uncoated High-speed tool steel

Material

Hardness, HB

Condition

Commercially pure: Ti (99.0)

110–170

Annealed

140–200

200–275

Alpha alloys: Ti-5Al-2.5Sn, Ti-5Al-2.5Sn-ELI, Ti-6Al-2Nb-1Ta-0.80Mo

300–340

Alpha-beta alloys: Ti-6Al-4V, 310–350 Ti-6Al-4V-ELI, Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-2Sn-4Zr-2Mo-0.25Si, Ti-6Al-2Sn-4Zr-6Mo 320–380

Beta alloys: Ti-3Al-8V-6Cr-4Mo-4Zr, Ti-8Mo-8V-2Fe-3Al, Ti-11.5 Mo-6Zr-4.5Sn, Ti-10V-2Fe-3Al, Ti-13V-11Cr-3Al

275–350

350–440

Depth of cut(a), mm (in.)

1.0 (0.040) 4.0 (0.150) 7.5 (0.300) 16.0 (0.625) Annealed 1.0 (0.040) 4.0 (0.150) 7.5 (0.300) 16.0 (0.625) Annealed 1.0 (0.040) 4.0 (0.150) 7.5 (0.300) 16.0 (0.625) Annealed 1.0 (0.040) 4.0 (0.150) 7.5 (0.300) 16.0 (0.625) Annealed 1.0 (0.040) 4.0 (0.150) 7.5 (0.300) 16.0 (0.625) Solution treated and 1.0 (0.040) aged 4.0 (0.150) 7.5 (0.300) 16.0 (0.625) Annealed or solution 1.0 (0.040) treated 4.0 (0.150) 7.5 (0.300) 16.0 (0.625) Solution treated and 1.0 (0.040) aged 4.0 (0.150) 7.5 (0.300) 16.0 (0.625)

Speed, m/min (sfm)

Feed, mm/rev (in./rev)

76 (250) 67 (220) 53 (175) … 58 (190) 52 (170) 46 (150) … 35 (115) 32 (105) 29 (95) … 24 (80) 21 (70) 18 (60) … 21 (70) 18 (60) 15 (50) … 20 (65) 17 (55) 14 (45) … 12 (40) 9 (30) 7 (25) … 11 (35) 7 (25) … …

0.13 (0.005)(b) 0.25 (0.010) 0.38 (0.015) … 0.13 (0.005) 0.25 (0.010) 0.38 (0.015) … 0.13 (0.005) 0.25 (0.010) 0.38 (0.015) … 0.13 (0.005) 0.25 (0.010) 0.38 (0.015) … 0.13 (0.005) 0.25 (0.010) 0.38 (0.015) … 0.13 (0.005) 0.25 (0.010) 0.38 (0.015) … 0.13 (0.005) 0.25 (0.010) 0.38 (0.015) … 0.13 (0.005) 0.25 (0.010) … …

Tool

Tool material grade(b), AISI

T15, M42 T15, M42 T15, M42 … T15, M42 T15, M42 T15, M42 … T15, M42 T15, M42 T15, M42 … T15, M42 T15, M42 T15, M42 … T15, M42 T15, M42 T15, M42 … T15, M42 T15, M42 T15, M42 … T15, M42 T15,M42 T15, M42 … T15, M42 T15, M42 … …

Speed, m/min (sfm) Brazed Indexable

160 (525) 137 (450) 104 (340) 52 (170) 137 (450) 119 (390) 88 (290) 44 (145) 88 (290) 76 (250) 58 (190) 29 (95) 66 (215) 56 (185) 43 (140) 21 (70) 52 (170) 44 (145) 34 (110) 17 (55) 49 (160) 41 (135) 26 (85) 15 (50) 38 (125) 32 (105) 24 (80) 12 (40) 36 (110) 27 (90) 21 (70) 11 (35)

172 (565) 148 (485) 110 (360) 55 (180) 152 (500) 130 (425) 98 (320) 49 (160) 113 (370) 98 (320) 73 (240) 37 (120) 76 (250) 66 (215) 49 (160) 24 (80) 69 (225) 59 (195) 44 (145) 21 (70) 58 (190) 50 (165) 37 (120) 18 (60) 49 (160) 41 (135) 26 (85) 15 (50) 38 (125) 32 (105) 24 (80) 12 (40)

Feed, mm/rev (in./rev)

material grade

0.13 (0.005) 0.25 (0.010) 0.38 (0.015) 0.50 (0.020) 0.13 (0.005) 0.25 (0.010) 0.38 (0.015) 0.50 (0.020) 0.13 (0.005) 0.20 (0.008) 0.38 (0.015) 0.50 (0.020) 0.13 (0.005) 0.20 (0.008) 0.25 (0.010) 0.38 (0.015) 0.13 (0.005) 0.20 (0.008) 0.25 (0.010) 0.38 (0.015) 0.13 (0.005) 0.20 (0.008) 0.25 (0.010) 0.38 (0.015) 0.13 (0.005) 0.20 (0.008) 0.25 (0.010) 0.38 (0.015) 0.13 (0.005) 0.20 (0.008) 0.25 (0.010) 0.38 (0.015)

C-3 C-2 C-2 C-2 C-3 C-2 C-2 C-2 C-3 C-2 C-2 C-2 C-3 C-2 C-2 C-2 C-3 C-2 C-2 C-2 C-3 C-2 C-2 C-2 C-3 C-2 C-2 C-2 C-3 C-2 C-2 C-2

ELI, extra-low interstitial. (a) Caution: check power requirements on heavier depths of cut. (b) Any premium high-speed tool steel can be used. Source: Metcut Research Associates Inc.

Table 10.4

Some typical machining parameters used to machine airframe bulkheads from an alpha-beta (Ti-6Al-4V) alloy

Operation

Milling rough/finish Milling rough Milling finish Milling finish

Table 10.5

Part surface

Cutter description and material

Speed, m/min (ft/min)

Feed, mm/tooth (in./tooth)

Peripheral ML flanges Thin flanges, walls Thin flanges Pocket floor

50.8 mm (2 in.) diam × 152.4 mm (6 in.) flute length, 6 flute, 35° helix, M42 31.8 mm (1.25 in.) diam × 50.8 mm (2 in.) flute length, 4 flute, 35° helix, M42 19.1 mm (0.75 in.) diam × 63.5 mm (2.5 in.) flute length, 4 flute, 35° helix, M42 31.8 mm (1.25 in.) diam × 50.8 mm (2 in.) flute length, 4 flute, 35° helix, M42

15 (50) 15 (50) 15 (50) 15 (50)

0.2/0.0096 (0.0066/0.0096) 0.2/0.009 (0.0062/0.009) 0.1/0.0034 (0.0024/0.0034) 0.2/0.009 (0.0062/0.009)

Example of typical parameters for machining gas turbine components from an alpha-beta (Ti-6Al-4V) alloy

Operation

Tool material

Cutting speed, m/min (ft/min)

Turn (rough) Turn (finish) Turn (finish) End mill (19.05–25.4 mm, or 3 4–1 in. diam) End mill (19.05–25.4 mm, or 3 4–1 in. diam)

C-2 C-2 C-2 M42 HSS (a) C-10

45 (150) 60 (200) 90 (300) 18 (60) 60 (200)

0.254 mm (0.010 in.)/rev 0.152–0.203 mm (0.006–0.008 in.)/rev 0.152–0.203 mm (0.006–0.008 in.)/rev 0.076 mm (0.003 in.)/tooth 0.127 mm (0.005 in.)/tooth

Drill (6.35–12.70 mm, or 1 4 –1 2 in. diam) Drill (6.35–12.70 mm, or 1 4 –1 2 in. diam) Ream

M42 HSS(a) C-2 M42 HSS (a) C-2 M7 HSS M3 HSS M42 HSS

9 (30) 12 (40) 6 (20) 10.5 (35) 4.5 (15) 3.6 (12) 3.6 (12)

0.127 mm (0.005 in.)/rev 0.102 mm (0.004 in.)/rev 0.254 mm (0.010 in.)/rev 0.254 mm (0.010 in.)/rev … 0.076 mm (0.003 in.)/tooth max 0.305 mm (0.012 in.)/stroke

Tap Broach Spline shape

(a)Designates tool material most widely used. HSS, high-speed steel

Feed

Depth of cut, mm (in.)

5.207 (0.250) 0.254–0.762 (0.010–0.030) 0.254–0.762 (0.010–0.030) Axial depth 3.175 (0.125) Radial depth: up to two-thirds cutter diameter Axial depth: 3.810–5.080 (0.150–0.200) Radial depth: up to two-thirds cutter diameter

Machining / 83 Water should never be applied directly to a titanium fire.

Nontraditional Machining Methods The production of titanium alloy components sometimes requires the use of the so-called nontraditional machining methods. Among these, electrochemical machining (ECM), chemical milling (CHM), and laser beam machining (LBM) are probably the most widely used. Technical information on procedures and techniques is generally proprietary. Chemical and electrochemical methods of metal removal are used because of their many favorable features. They are particularly useful for rapid removal of metal from the surface of formed or complex-shaped parts, from thin sections, and from large areas down to shallow depths. These processes have no damaging effect on the mechanical properties of the metal. There is no hydrogen entry into the metal to cause embrittlement or loss of ductility. ECM is the removal of electrically conductive material by anodic dissolution in a rapidly flowing electrolyte that separates the workpiece from a shaped electrode. ECM can generate difficult contours and provide distortion-free, high-quality surfaces. For ECM of titanium alloys, a very common electrolyte is sodium chloride used at concentrations of about 0.12 kg/L (1 lb/gal). CHM is the controlled dissolution of a workpiece material by contact with a strong chemical reagent. The part being processed is cleaned thoroughly and covered with a strippable, chemically resistant mask. Areas where chemical action is desired are stripped of the mask, and then the part is submerged in the chemical reagent to dissolve the exposed material. In LBM, material is removed by focusing a laser beam and a gas stream on a workpiece. The laser energy causes localized melting, and an oxygen gas stream promotes an exothermic reaction and purges the molten material from the cut. Titanium alloys are cut at very rapid rates using a continuous-wave carbon dioxide laser with oxygen assist.

Fig. 10.4 sweep speed

Laser beam heating of titanium steel, and aluminum, showing melt depth versus beam

Electrochemical Machining. The electrolyte for typical ECM operating conditions is a sodium chloride or potassium chloride solution of 0.12 kg/L (1 lb/gal) of water. Voltage must be greater than 11 V for potassium chloride electrolytes. In one application, the maximum starting voltage was 3.2 V for annealed Ti-6Al6V-2Sn in a sodium chloride electrolyte solution. A typical metal removal rate is approximately 1.64 cm3/min./l000 A (0.10 in.3/min./1000 A) at an electrolyte temperature of 40 °C (100 °F). Chemical Machining. Typical operating conditions for titanium alloys are: Principal etchant

Etch rate, mm/min (in./min) Optimum etch depth, mm (in.) Etchant temperature, °C (°F) Average surface roughness (RA), µm (µin.)

Hydrofluoric acid

0.015–0.030 (0.0006–0.0012) 3.18 (0.125) 46 ± 2.7 (115 ± 5) 0.40–2.50 (16–100)

Tolerances on depth of cut up to 12.7 mm (0.5 in.) for titanium alloys are: Depth of cut

The surface of titanium alloys is thought to be easily damaged during some traditional machining operations. Damage appears in the form of microcracks, built-up edges, plastic deformation, heat-affected zones, and tensile-residual stresses. In service, this damage can lead to degraded fatigue strength and stress-corrosion resistance. In a study of grinding effects on Ti-6Al-4V alloy, gentle or low-stress grinding parameters displayed no readily identifiable changes at the surface, while conventional and abusive practices altered the surface layer noticeably. There was an appreciable drop in hardness in the gently ground specimen, but very good high-cycle fatigue values were noted. Figure 10.5 indicates an endurance limit of 372 MPa (54 ksi) for the gentle grinding and Table 10.6 Cutting rates for laser beam machining of titanium alloys

Tolerance

Work thickness

mm

in.

mm

in.

0–1.25 1.25–2.55 2.55–6.35

0–0.050 0.050–0.100 0.100–0.250

0.05 0.075 0.10

0.002 0.003 0.004

Laser Beam Machining. Contours can be cut rapidly with laser beams (Table 10.6) as compared to conventional methods such as band sawing. For a given power level and sweep speed, the melt depth in titanium is slightly greater than that of steel and aluminum (Fig. 10.4).

Fig. 10.5

Surface Integrity

Type of cut

Contour Contour Contour Straight Contour Contour Contour Contour

Cutting speed(a)

mm

in.

mm/min

0.5 1.6 3.1 6 6 13 25 50

0.020 0.062 0.125 0.250 0.250 0.50 1.0 2.0

5080 4060 3050 5080 1520 1020 380 130

in./min

200 160 120 200 60 40 15(b) 5(b)

(a)Data are based on use of a continuous wave CO2 laser with an oxygen assist. (b) 16 kW (21 hp) laser was used. Source: Metcut Research Associates Inc.

Summary of machining effects on high-cycle fatigue behavior of Ti-6Al-4V (annealed, 32–34 HRC). EDM, electrical discharge machining; CHM, chemical milled

84 / Titanium: A Technical Guide values of 83 and 97 MPa (12 and 14 ksi) for conventional and abusive conditions, respectively. Figure 10.5 also presents values for other machining operations, including electrical discharge machining and chemical milling. As can be seen, in operations such as end-mill cutting or turning, the same sensitivity to abu-

sive conditions was not observed, possibly due to residual surface compressive stresses. Machinists and companies specializing in the machining of aerospace materials generally have developed techniques to maximize surface integrity of titanium alloys. Thus, optimum properties usually are achieved during the pro-

duction machining of titanium. In those areas of application where maximum fatigue strength is required, not only are appropriate machining parameters used, but also selected surface areas of components can be glass-bead blasted to restore, or to retain, a high level of favorable compressive surface stress.

Titanium: A Technical Guide Matthew J. Donachie, Jr., p85-93 DOI:10.1361/tatg2000p085

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 11

Cleaning and Finishing Cleaning procedures serve to remove scale, tarnished films, and other contaminants that form or are otherwise deposited on the surface of titanium and titanium alloys during processing operations such as hot working and heat treatment. Cleaning and finishing processes for titanium and its alloys are similar in some ways to those for other metals. However, the differences in processes, methods, and cleaning solutions compared with other less reactive metals are significant when it is desirable to maximize metal application performance and/or maintain safe procedures during working of titanium alloys. Descaling and cleaning of titanium alloys are often necessary preliminaries for other operations. Before being subjected to any thermal treatment, titanium components should be cleaned and dried. Caution: Do not use ordinary tap water in cleaning titanium components. Oil, fingerprints, grease, paint, and other foreign matter should be removed from all surfaces. Cleaning is required because the chemical reactivity of titanium at elevated temperatures can lead to its contamination or embrittlement and can increase its susceptibility to stress corrosion. After cleaning, parts should be handled with clean gloves to prevent recontamination. If a component is to be sized, straightened, or heat treated in a fixture, the fixture also should be free of any foreign matter and loosely adhering scale.

Special Coatings and Surface Finishes Because their resistance to many corrosive environments is excellent, titanium alloys do not require special surface treatments to improve corrosion resistance. However, wear resistance and/or lubricity are common concerns in the surface behavior of titanium alloys. Titanium alloys can have high wear rates when in contact with titanium, titanium alloys, or other metal alloys, due to high friction coefficients and galling. Methods of surface hardening and

the application of coatings for lubrication are thus areas of interest. Different coatings can be applied to the surface of titanium alloys to develop or to enhance specific properties, such as lubricity or wear resistance. In addition to coatings for lubricity, titanium is coated or plated with corrosion-resistant metals (e.g., copper and platinum) as an alternative to oxide formation or as the basis for subsequent plating. Coatings are applied for emissivity improvement. Unique titanium alloy combinations have been bonded to the surface of titanium alloys. Other surface treatments have been considered to improve various properties of titanium alloys.

Cleaning and Descaling Problems Most surface treatments and operations require the removal of surface oxides, which can be in the form of a case scale or a thin oxide tarnish. Any oxide formed under 600 °C (1100 °F) on titanium alloys can be removed with a nitric-hydrofluoric acid pickle bath. Oxides formed at temperatures above 600 °C (1100 °F) can be removed either mechanically or chemically by immersion in molten salt baths. The metallurgical and chemical properties of titanium create a number of very special cleaning problems. These include:

• Affinity of titanium to common gases • Galvanic effects caused by discontinuities in scaled surfaces

• Metallurgical restrictions on the temperature of the descaling media

• Variety of scales encountered in titanium descaling

• Protective coatings used in titanium manufacturing

Gas Absorption. The capacity of titanium to absorb common gases, including oxygen, hydrogen, and nitrogen (all of which tend to embrittle the product) is the property that causes the most difficulty in the descaling and finishing of titanium and its alloys. Because

tightly packed, hot rolling scale acts as partial protection against additional gas absorption, some mills perform two or three heat treatments over the scale. Each additional heat treatment toughens the scale and compounds the descaling difficulties. A further problem is that heat treating furnace atmospheres are maintained on the oxidizing side to minimize chances for hydrogen pickup. However, this practice promotes oxygen absorption and scale formation. A layer of oxygen-rich metal, as shown in Fig. 11.1 develops beneath the resulting scale formation. It varies in thickness from 0.05 to 0.07 mm (0.002–0.003 in.) in the heat-treated condition to as much as 0.15 to 0.20 mm (0.006–0.008 in.) in the hot-rolled condition. Because oxygen (and nitrogen) interstitials increase hardness and decrease ductility of titanium, the resultant oxygen-rich area becomes a brittle layer. This brittle layer is removed, usually by acid or electrolytic chemical pickling. Galvanic effects and discontinuities in the surface scale are encountered in all types of metal descaling, but they appear to be more pronounced in titanium. Although the exact cause of small pits or cells formed in descaled material is a debatable issue, possibilities include alloy or nonmetallic segregations, scale porosity, and surface contamination. A more severe galvanic attack problem is created by patch scale conditions on titanium surfaces when areas of heavy scale flake away from an apparently uniform surface. The same problem has been observed with superimposed oxides, even though the surface layer can be quite thin and powderlike. Surface contamination with oil, grease, or fingerprints can also create a patch scale condition. All of these factors promote severe localized attack when areas of the basis metal are exposed selectively during descaling. Some producers have considered, as a possible solution, reoxidation of the product during processing. Metallurgical Restrictions on Descaling. Solution-treated, age-hardenable alloys of titanium are sensitive to time-temperature reactions, and the temperatures of descaling media,

86 / Titanium: A Technical Guide which can induce a subsequent aging effect and change mechanical properties. For example, metastable beta or beta alloys, which are solution treated and aged at temperatures ranging from 370 to 540 °C (700–1000 °F) for times of 8 h or more, can suffer a subsequent aging effect and a significant change in mechanical properties if descaled at the higher temperatures. Changes can be particularly noticeable in thin-gage sheet materials where descaling temperature-time conditions can cause property changes of as much as 70 MPa (10 ksi) in tensile strength. Alloy descaling temperatures normally should not be allowed to exceed 260 °C (500 °F). Variety of Scale. Another factor that contributes appreciably to the problems of descaling titanium is the wide variety of scale encountered, including scale formed by annealing, forging, solution treating, stress relieving, extruding, rolling, aging, hot forming, or a combination of several of these operations. With processing temperatures ranging from 425 to 1150 °C (800–2000 °F), the scale spectrum for titanium is far broader than for most other materials that are difficult to descale. In-Process Coating Effects. Coatings, often used in titanium manufacturing operations to facilitate working, are frequently an asset and a necessity. Unfortunately, they become a liability and a contaminant in postworking cleaning operations. The coatings are soluble and removable if the proper techniques are used. Protective coatings are applied to titanium surfaces during manufacturing operations for several reasons:

• To lubricate and aid in metal flow, good die contouring, and forming operations

• To act as barrier films, reducing gas contam•

ination during high-temperature forming and heat-treating cycles To reduce surface flaws caused by nicking and scratching during manufacturing operations

Gas-protective films are usually applied directly to the surface of the titanium. They are silicate-base materials that deposit uniform, fusible films through solvent evaporation. These films form glassy barriers at treatment temperatures up to 8l5 °C (1500 °F) and are quite effective in reducing oxygen, hydrogen, and nitrogen contamination. Above about 815 °C (1500 °F), most of these films are less effective. Lubricant films or abrasion-protective films are applied over a silica-base coating. This process has the advantage of providing double protection against scratching and scoring. During hot forming operations and metal surface stretching, some voiding and penetration of the coating occurs, creating a titanium oxide on the surface. The contaminant to be removed after the working operations then consists of organic bond or residues, graphite, molybdenum disulfide, silicates, and titanium oxides.

Removal of Scale Scale is removed from titanium products by several mechanical methods. Abrasive methods, such as grinding and grit blasting, are preferred for removing heavy scale from large sections. Centerless grinding is used for finishing round bars, and wide belt grinding is used for finishing sheet and strip. Grinding is usually most efficient when it is performed at low wheel and belt speeds. Belt Grinding. Most alloy sheet materials with a high aluminum content, such as Ti-5Al2.5Sn, are ground to eliminate pits and a rippled condition that develops in hot rolling as a result of discontinuous slip during plastic deformation. Grinding is frequently used to eliminate surface defects before cold rolling. Dry belt grinding is dangerous because of the hazards of explosion and fire. It is also not economical because of poor belt life. When stock is removed during dry grinding, small globules of molten metal and oxide roll along the sheet, causing a type of pitting by burning that is not removed by the grinding. Embedded grit and weld grit scratches result when titanium welds to the dry grit. Originally, strip was ground on standard strip grinders, using various oil lubricants; however, oils contributed to fire hazard and several grinding machines were partially or wholly destroyed when the oil ignited. When titanium was ground with aluminum oxide belts, a water lubricant was less effective than air. The water reacted with the aluminum oxide to form a weak hydroxide that proved ineffective as a grinding lubricant. A 5% aqueous solution of potassium orthophosphate (K3PO4) is widely used as a grinding lubricant. It is applied as a flood at both the entrance and exit side of the contact line. Water-soluble oils, particularly highly chlorinated and sulfochlorinated oils, also have been successful as lubricants. These compounds should be used with care because of the possibility that chloride residues remain as an integral part of

Fig. 11.1

Ti-6Al-4V alpha case. 250×

the surface. Both types of lubricants improve grinding efficiency when the belts are coated with aluminum oxide or silicon carbide. Flooding the work with lubricant is recommended; however, machines built for flooding are equipped with a recirculating and filtering system and waterproof cloth belts, and they are expensive. An alternative is to spray a water-soluble wax fog through atomizing nozzles on the line of contact at both the entrance and exit sides of the belt. The solution should not be sprayed through an ejector that mixes it with air because that increases the fire hazard. Instead, the solution should be sprayed as an atomized liquid. Application of the spray can be controlled to volatilize the lubricant during grinding. This eliminates the need for waterproof belts. Care must be exercised to avoid a buildup of titanium chips that can cause a fire. The spray does not remove chips that would wash away in a flood. Titanium should be ground at belt speeds not exceeding rates of 8 m/sec (1500 ft/min). Using a 5% solution of potassium orthophosphate as a lubricant, maximum efficiency is achieved at about 6 m/sec (1100 ft/min). Both billy-roll and flat table grinding machines have been successful in grinding titanium. Sheet grinding machines, equipped with feed rolls, sometimes leave a ground line on the sheet. A high degree of grinding uniformity is obtained on machines equipped with a flat table and vacuum chuck. On these machines, the table holding the sheet usually oscillates. Traveling-head machines are available also. The sequence for the belt grinding of Ti-6Al-4V sheet is shown in Fig. 11.2. The belt grinding sequence (see Fig. 11.2) is usually begun with an 80-grit belt when it is necessary to remove more than 0.07 mm (0.003 in.) of stock from the surface of the sheet. Descaling and pickling of the sheet before grinding prolongs belt life. Following the initial grit, each successive grit must remove enough stock to eliminate the scratches caused by the previous grit. The alpha alloys, such as Ti-5Al-2.5Sn, are less sensitive to surface con-

Cleaning and Finishing / 87

Fig. 11.2

Cleaning and belt grinding sequences for Ti-6Al-4V sheet

dition than the alpha-beta alloys, such as Ti-6Al-4V. Surface pits on Ti-6Al-4V sheet, caused by weld grit scratches, seriously detract from bend ductility and might impact fatigue strength. Abrasive Blasting. Abrasive-blast cleaning techniques, either wet or dry, are convenient for removing scale from a variety of titanium products ranging from massive ingots to small parts. Because it can be used at lower velocities and is less likely to be embedded in the surface, alumina sand is preferred to silica sand. Sheet in thicknesses to about 0.50 mm (0.020 in.) can be descaled without distortion if fine sand and low velocities are used. Mill scale on titanium semiproducts can be removed with coarse, high-carbon steel shot or grit, while finished compressor blades can be cleaned with zircon sand of 150 to 200 mesh. The type of product to be cleaned, the cleaning rate, and the cost of the abrasive must be balanced in the selection of a specific blast cleaning method. Mineral abrasive particles, such as silica, zircon, or alumina sands, are used more com-

Fig. 11.3

monly than metal abrasives for blasting finished or semifinished products. Although these abrasives are more expensive, they produce the finer finish that is required in final processing or service. Adequate safety precautions must be observed to avoid inhalation of fine sand particles. Air circulating and dust collecting systems must be cleaned frequently. They must be equipped to cope with the re hazard associated with titanium dust. A fine dust remains on the titanium from the blasting operation, particularly when mineral abrasives have been used. This is not considered detrimental, although a washing or pickling cycle following the blast is desirable if the part is to be welded subsequently. Both wet blasting and dry blasting procedures are used for descaling titanium parts. Wet Blasting. Parts are wet-blast cleaned using a slurry that consists of 400-mesh aluminum oxide, 40 vol%, and water. Air pressure of 655 kPa (95 psi) is used to pump the slurry in a steady stream with a pressure of about 34 kPa (5 psi). The descaling rate, normally about 50

Artist’s rendering of effect of surface condition on etched metal surface

min/m2 (5 min/ft2), depends on the complexity of the part. Distortion and the need for planishing are held to a minimum by placing the blast nozzle at a distance of approximately 50 mm (2 in.) from the workpiece and by using an angle of impingement of 60°. Dry Blasting. Rocket motor-case assemblies have been dry blasted after final stress relieving at 480 to 540 °C (895–1005 °F). Blasting is accomplished with 100- to 150-mesh zircon sand at an air pressure of 275 kPa (40 psi). Each assembly is rotated at 2.5 rev/min and is passed at a speed of 65 mm/min (2.5 in./min) between two diametrically opposed, fixed-position blasting nozzles. The nozzles blast the inside and outside surfaces simultaneously at the same wall location. To prevent distortion, each nozzle is placed at the same distance, 300 mm (12 in.), from the metal surface.

Molten Salt Descaling Baths Molten salt descaling baths are primarily used for descaling bar, sheet products, and tubing. Even with the most effective barrier films available today, some gas penetration of titanium surfaces can be expected at the elevated temperatures required for working and heat treatment. The alpha case, or oxygen-enriched layer, resulting from this gas reaction is extremely hard and brittle and must be removed. Bar products used for machining finished pans must have this hard scale and oxide removed because these are very abrasive and cause rapid tool wear. Material used for welding or forming must have these scales removed, or poor and small welds are made; subsequent forming (hot or cold) is virtually impossible without surface rupture or failure of parts. Removal presents no serious problems because chemical milling techniques have been perfected by the aircraft industry to effect weight savings. In the case of titanium, the purpose is to improve the structural soundness of metal, and the solvent materials applied are of a different chemical composition. One specific problem encountered in alphacase removal is that the titanium oxide formed is substantially more insoluble in the nitric hydrofluoric etchant than the base metal is. Residues of oxide on the surface develop areas resembling craters on the finished product. Examination of the artist’s conception sketch shown in Fig. 11.3 indicates the surface as a result of a nonuniform cleaning operation. Where alpha-case removal is a required part of a manufacturing operation, salt bath cleaning is specified because proper cycling practically guarantees a chemically clean surface. Conditioning salt baths fall into two basic categories: high-temperature salt baths and low-temperature salt baths. Alternatively, grit blasting can be used to break up the scale so the nitric-hydrofluoric etchant or chemical milling solution removes scale more evenly.

88 / Titanium: A Technical Guide High-Temperature Molten Salt. High-temperature salt baths can vary in chemical reaction and effectiveness depending on composition. All types operate at a range of 370 to 480 °C (700–895 °F). The temperature range is sufficiently high to produce the most rapid reaction possible for soiled and oxide films. The range also is sufficiently high to possibly promote metallurgical changes in some alloys, as, for example, omega-phase precipitation in metastable beta alloys. High-temperature oxidizing salt baths are also capable of reacting chemically with organic films to destroy them. These baths are also excellent solvents for silicate barrier films. They do require special fixturing to reduce the strong galvanic effects present at these temperatures, and, for this reason, they are used in cleaning primary-forming operation products, such as forgings, extrusions, rolled plate, and sheet. The major advantage of high-temperature oxidizing or reducing salt baths for titanium descaling is their great speed in removing extremely tenacious scale. Although reducing baths have the inherent disadvantage of promoting hydrogen absorption, this can be overcome or minimized by chemical additions. Vacuum degassing is another solution to the hydrogen problem. A primary producer of titanium sheet uses an oxidizing salt bath for removing the hot-work scale in the following sequence of operations: 1. Immerse in oxidizing salt for 5 to 20 min at 400 to 480 °C (750–895 °F). 2. Quench with water. Hold 1 min. 3. Immerse in sulfuric acid, 10 to 40 vol%, for 2 to 5 min at 50 to 60 °C (120–140 °F). 4. Rinse with water for 1 min. 5. Repeat if necessary. 6. Pickle in nitric-hydrofluoric acid solution, time and concentration as required. The same producer also uses a sodium hydroxide reducing salt bath for descaling highbeta or metastable beta alloys. A typical cycle using this type of salt is: 1. Immerse in reducing salt for 1 to 3 min at 370 °C (700 °F). 2. Quench in water 1 min. 3. Immerse in sulfuric acid, 10 to 40 vol%, for 2 to 5 min at 50 to 60 °C (120–140 °F). 4. Rinse in water.

Table 11.1

5. Pickle in nitric-hydrofluoric acid solution, time and concentration as required. 6. Vacuum degas or decontaminate titanium beta alloys that absorb hydrogen in reducing baths. These baths are used by one of the major aerospace contractors for cleaning titanium blades for jet engines. Blade materials are Ti-6Al-4V and Ti-8Al-1Mo-1V. A descaling cycle for removing oxides and proprietary glass-like compounds from these blades is: 1. Immerse in oxidizing salt for 15 min at 455 °C (850 °F). 2. Rinse in cold water. 3. Pickle in solution of 35% nitric acid and 3.5% hydrofluoric acid for 1 min max at 20 °C (70 °F). 4. Rinse in hot water. Low-Temperature Baths. The temperature range used with low-temperature baths for cleaning fabricated parts is 200 to 220 °C (390–430 °F). Descaling systems based on salts in this temperature range eliminate some of the possible problems associated with higher-temperature baths:

• • • • •

Age hardening Dissimilar metal reactions Chemical attack Metal distortion Hydrogen embrittlement

Salts in this range have a very limited composition because of the effect of various compounds on the melting point. Although they contain oxidizing agents, the effect of these materials is not as aggressive as it is in the high-temperature fused salts. Consequently, organic materials are not destroyed, but they are saponified and absorbed. Silicate barrier films and molybdenum disulfide are soluble in these low-temperature salts. The temperature range permits cycling between salt and acid to reduce cleaning times and costs. Examples of salt bath and acid cycle times are given in Table 11.1. Aqueous Caustic Descaling. Aqueous caustic descaling baths have been developed to remove light scale and tarnish from titanium alloys, except beta titanium alloys. Aqueous caustic solutions containing 40 to 50% sodium hydroxide have been used successfully to

Low-temperature salt bath and acid bath conditions Scale formation temperature

Salt bath immersion

Acid cleaning bath

Acid cleaning bath

Sample composition

°C

°F

time(a), min

time(b), min

time(c), sec

Ti-6Al-4V Ti-8Al-1Mo-1V Ti-8Al-1Mo-1V Ti-6Al-4V(d) Ti-6Al-4V(e) Ti-8Al-1Mo-1V(e)

650 650 820 820 950 950

1200 1200 1510 1510 1745 1745

2 2 5 5 5 5

2 2 2 5 5 5

30 30 30 30 60 60

(a) Salt bath temperature 205 °C (400 °F). (b) Bath composition, 30% sulfuric acid. (c) Bath composition, 30% nitric acid, 3% hydrofluoric acid. (d) Sample recycled in salt bath for 5 min, in sulfuric acid bath for 5 min, in nitric acid-hydrofluoric acid bath for 30 sec. (e) Sample recycled in salt bath for 5 min, in sulfuric acid bath for 5 min, in nitric acid-hydrofluoric acid bath for 60 sec

descale many titanium alloys. One bath containing 40 to 43% sodium hydroxide operates at a temperature near its boiling point, 125 °C (260 °F). Descaling normally requires from 5 to 30 min. Immersion time is not critical because little weight loss is encountered after the first 5 min. Caustic descaling conditions the scale so that it is removed readily during subsequent acid pickling. Caution: this procedure is not recommended for beta alloys. They can absorb hydrogen so quickly in concentrated caustics that a 30 min exposure could cause hydrogen levels to exceed specification. A more effective aqueous solution contains either copper sulfate or sodium sulfate in addition to sodium hydroxide. This bath operates at a lower temperature, 105 °C (220 °F). A composition of this solution by weight is as follows: 50% sodium hydroxide, 10% copper sulfate pentahydrate (CuSO4-5H2O), and 40% water. Using immersion times of 10 to 20 min, this bath has proved effective in descaling Ti-6Al-4V and Ti-2.5Al-16V alloys.

Pickling Procedures Following Descaling All advantages gained through proper conditioning and handling of titanium parts during cleaning can be lost if the composition and temperature of the final pickling acid bath is not properly controlled. Cold, spent acid solutions will not only increase the time requirements for pickling appreciably but also the possible quality problems experienced with hydrogen pickup. On the other hand, highly concentrated hot acids can be overly aggressive, resulting in surface finish problems, such as a rough and pitted surface caused by preferential acid attack. Sulfuric acid (35 vol% at 65 °C, or 150 °F) is recommended for pickling immediately following salt bath conditioning and rinsing to remove molten salt and residual softened scales. An acid of this formula has very little effect on titanium metal. Metal salts in the original and additional acid solutions further minimize these base-metal attacks. Table 11.2 gives conditions for corrosion of titanium in various sulfuric acid pickle baths. Pickling solutions for cleaning can be weaker than descaling solutions. A nitric-hydrofluoric acid solution, which is the final stage brightening in most alloy cleaning lines, should be maintained at a minimum ratio of 15 parts nitric acid to 1 part hydrofluoric acid to reduce hydrogen pickup effects. The concentration of hydrofluoric acid can vary from 1 to 5%, or be even higher, as long as the ratio is not exceeded. The activity of these pickle solutions is affected by titanium content, and the acids are frequently discarded at a level of 22 g/L (3 oz/gal); the solution used for final brightening can be used for the required alpha-case removal, as well, with careful monitoring of titanium content.

Cleaning and Finishing / 89 Table 11.2 Sulfuric acid concentration, %

Corrosion of titanium in sulfuric acid pickle baths Bath temperature

Corrosion rate

Acid addition

°C

°F

μm/yr

mils/yr

0.5%(a) 1%(a) 10%(a) 0.25%(a) 2%(b) 7–8%(b)

38 38 38 95 Boiling point 60

100 100 100 205 Boiling point 140

100 20 400 76 125 125

4.0 0.8 16.0 3.0 5.0 5.0

30 30 30 30 10 17

A nitric-hydrofluoric acid solution, which is the final stage brightening in most alloy cleaning lines, should be maintained at a minimum ratio of 15 parts nitric acid to 1 part hydrofluoric acid to reduce hydrogen pickup effects; the concentration of hydrofluoric acid may vary from 1–5%, or even higher, as long as the ratio is not exceeded; the activity of these pickle solutions is affected by titanium content, and the acids are frequently discarded at a level of 26 g/L (3 oz/gal); the solution used for final brightening can be used for the required alpha-case removal also, assuming a careful watch on the titanium content. (a) Copper sulfate. (b) Ferrous sulfate

Removal of Tarnish Films Tarnish films are thin oxide films that form on titanium in air temperatures between 315 and 650 °C (600 and 1200 °F) after exposure at 315 °C (600 °F). The film is barely perceptible, but with increasing temperature and time at temperature it becomes thicker and darker. The film acquires a distinct straw yellow color at about 370 °C (700 °F) and a blue color at 480 °C (900 °F). At about 650 °C (1200 °F), it assumes the dull gray appearance of a light scale. Alloying elements and surface contaminants also influence the color and characteristics. Tarnish films are readily removed by abrasive methods, and all but the heaviest films can be removed by acid pickling. Prolonged exposures at temperatures above about 595 °C (1104 °F), in combination with surface contaminants, result in heavier surface films that are not removed satisfactorily by acid pickling, but require descaling treatments for their removal.

Acid Pickling Acid pickling removes a light amount of metal, usually a few tenths of a mil. It is used to remove smeared metal, which could affect

Table 11.3 Effect of titanium alloy composition on hydrogen pickup in acid pickling Hydrogen pickup Thickness

(gage removed),

penetrant inspection. Titanium and titanium alloys can be satisfactorily pickled by the following procedure: 1. Clean thoroughly in alkaline solution to remove all shop soils, soap drawing compounds, and identification inks. If coated with heavy oil, grease, or other petroleumbased compounds, parts can be degreased in trichlorethylene before alkaline cleaning. Degreasing will not be harmful to the part in subsequent processing. 2. Rinse thoroughly in clean, running water after alkaline immersion cleaning. 3. Pickle for 1 to 5 min in an aqueous nitric-hydrofluoric acid solution containing 15 to 40 wt% nitric acid and 1.0 to 2.0 wt% hydrofluoric acid, and operated at a temperature of 24 to 60 °C (75–140 °F). The ratio of nitric acid to hydrofluoric acid should be at least 15 to 1. The preferred acid content of the pickling solution, particularly for alpha-beta and beta alloys, is usually near the middle of the ranges mentioned. A solution of 33.2% nitric acid and 1.6% hydrofluoric acid has been found effective. When the buildup of titanium in the solution reaches 15 g/L (2 oz/gal), discard the solution. 4. Rinse the parts thoroughly in clean water. 5. High-pressure spray wash thoroughly with clean water at 55 ± 6 °C (130 ± l0 °F). 6. Rinse in hot water to aid drying. Allow to dry. To avoid excessive stock removal, the recommended immersion times for pickling solutions should not be exceeded. It is equally important to maintain the composition and operating temperature of the bath within the limits prescribed to prevent an excessive amount of hydrogen pickup. Gage loss from

Alloy

mm

in.

ppm/0.0250 mm (ppm/0.001 in.)

Alpha alloy Ti-5Al-2.5Sn Ti-5Al-2.5Sn

0.50 1.00

0.020 0.040

0–4 0–3

Alpha-beta alloy Ti-6Al-4V 0.50 Ti-6Al-4V 1.00

0.020 0.040

4–7 3–5

Capacity,

10–15 5–8

0.02 0.75 0.07 2.33 0.25 8.85

Beta alloy Ti-13V-11Cr-3Al Ti-13V-11Cr-3Al

Table 11.4

m3

0.50 1.00

0.020 0.040

Pickling bath is an aqueous solution containing 15% nitric acid and 1% hydrofluoric acid by weight; operating temperature is 49–60 °C (120–140 °F).

ft3

all-acid pickling after descaling is estimated to be less than 0.025 mm/min (0.001 in./min), as determined by the combination of variables used. Depending on alloy composition and gage material pickled, hydrogen contamination is estimated to be 0 to 15 ppm per 0.025 mm (0.001 in.) of metal removed. Data on hydrogen pickup for an alpha, an alpha-beta, and a beta alloy pickled in a 15% nitric acid, 1% hydrofluoric acid bath at 49 to 60 °C (120–140 °F) are given in Table 11.3. Hydrogen contamination can be held to a minimum by maintaining a ratio of nitric acid to hydrofluoric acid equal to, or greater than, 10 to 1. Hydrogen diffuses more rapidly into the beta phase. Alpha-beta alloys that have been heat treated to complete equilibrium pick up less hydrogen than alpha-beta alloys with microstructures of transformed beta and/or with simple mill-annealed structures. Mass (Barrel) Finishing. Oxide films formed by heating to temperatures as high as 650 °C (1200 °F) for 30 min were effectively removed from Ti-8Mn alloy parts by wet mass finishing, also known as barrel finishing. Parts were randomly loaded in the barrel and rotated at relatively low barrel speeds to minimize distortion and nicking. Conditions for mass finishing of titanium parts are given in Table 11.4. At barrel speeds of 43,000 to 51,000 mm/min (1700–2000 in./min), parts have been cleaned satisfactorily in about 1 h. When mass finishing titanium parts, the ratio of abrasive medium to parts should be between 10 to 1 and 15 to 1, depending on the size of the parts. Proportionately more medium is required as part size increases. Water is used to cover parts and medium. Surface finish is improved when more water is added, but cycle time required to obtain a given finish is increased. The rate of descaling increases directly with barrel speed but is limited by the fragility of the parts being processed. Aluminum oxide mediums are the most satisfactory. They do not contaminate the work, yet they have a long, useful life. For oxide removal, small, well-worn mediums produce the highest finish. To avoid possible metallic contamination, the medium used for titanium should not be used in processing other metals. Strong acid forming compounds are to be avoided, principally because they are corrosive and contribute to hydrogen embrittlement. Because of the fire hazard created by fine, dry titanium particles, dry mass finishing of titanium parts is not recommended.

Mass (barrel) finishing conditions for titanium parts Barrel size diam

Width

Part load

Speed,

mm

in.

mm in. rev/min

381 559 813

15 22 32

178 7 240 10 457 18

36 28 20

kg

Medium(a) lb

1–2 3–4 4–5 8–12 14–18 30–40

kg

lb

18 54 209

40 120 460

Water L

qt

1.2 1.25 4 4 14 15

Abrasive compound(b) kg

lb

0.2 0.7 2.3

0.5 1.5 5

Alkaline cleaner(c) kg

lb

0.2 0.5 0.34 0.75 0.5 1

(a) Aluminum oxide nuggets 6.4–38 mm (0.25–1.5 in.) or preformed vitrified chips 4.8 × 9.5 to 7.9 × 28.6 mm (3 16 × 3 8 to 5 16 × 1 1 8 in.). (b) Dry, mildly alkaline compound. (c) Mild cleaner with high soap content

90 / Titanium: A Technical Guide

Polishing and Buffing The polishing and buffing of titanium and its alloys is accomplished with the same equipment used for other metals. Polishing frequently is done wet with mineral oil lubricants and coolants. Dry polishing is more appropriate than wet for some applications Polishing. Silicon carbide abrasive cloth belts have been effective. It is common to polish in two or more steps. Use a coarser-grit belt initially, such as a 60- or 80-grit belt, to remove gross surface roughness. Follow this with a 120- or 150-grit belt to provide a smooth finish. Titanium tends to wear the sharp edges of the abrasive particles and also to load the belts more rapidly than steel, so frequent belt changes are required for effective cutting. A good flow of coolant improves polishing and extends the life of the abrasives. For dry operations, belts or cloth wheels with silicon carbide abrasive may be used. Soaps and proprietary compounds can be applied to the belts to improve polishing and to extend belt life. Abrasive belt materials that incorporate solid stearate lubricants offer improved results for dry polishing operations. Fine polishing of titanium articles for extremely smooth finishes requires several progressive polishing steps with finer abrasives until pumice or rouge types of abrasive are applied. With the softer grades of titanium, such as unalloyed material, fine polishing requires more time and care to prevent scratching. The harder alloy grades can be polished more readily to a surface of high reflectivity. If a matte finish is desired, wet blasting with a fine slurry can be used after initial polishing. Buffing. Titanium alloys can be buffed safely. The purpose of buffing is to improve the surface appearance of the metal and to produce Table 11.5

a smooth, tight surface. Buffing is used as a final finishing operation and is particularly adaptable to finishing a localized area of a part. Items such as body prostheses, pacemakers, and heart valves require a highly buffed, tight surface to prevent entrapment of particles. Close fitting parts for equipment, such as the modern guidance systems and electronics applications, require highly polished surfaces obtained by buffing. In addition, sheet sizes too large to be processed by other abrasive finishing methods, such as mass finishing or wet blasting, can be economically processed by buffing. The principal limitations of buffing are:

• Distortion, caused by the inducement of localized stress

• Surface burning, resulting from prolonged dwell of the buff

• Inability to process inner or restricted surfaces

• Feathering of holes and edges Proper care of the buffing wheel is essential. Buffing with insufficient compound or a loaded wheel produces a burning or distortion of the part. After buffing, no further cleaning of parts is required, except for degreasing to remove the buffing compound. Electropolishing can completely remove all traces of worked metal remaining from mechanical grinding and polishing operations used in specimen preparation. When electropolishing is used in metallography, it is preceded by mechanical grinding (and sometimes polishing) and followed by etching. The conditions and electrolytes required to obtain a satisfactory polished surface differ for different alloys. Even minor alloying additions to a metal can significantly affect the response of the metal to polishing in a given electrolyte.

Electrolytes and voltages for electropolishing of titanium and titanium alloys

Electrolyte

Cell voltage

Time

Notes

15–60 s

(b)

5–30 s

…

45 s

(c)

~3 min

(d)

20–60 12–70 40–100

1

1–5 min 2–2 min 1–15 min

(e) … …

30–60

1–6 min

…

24–35

…

(f)

Electrolytes composed of HClO4 and alcohol with or without organic additions(a) 30–65 700 mL ethanol (absolute), 120 mL distilled H2O, 100 mL 2-butoxyethanol, 80 mL HClO4 (60%) 60–150 600 mL methanol (absolute), 370 mL 2-butoxyethanol, 30 mL HClO4 (60%) 58–66 590 mL methanol (absolute), 6 mL distilled H2O, 350 mL 2-butoxyethanol, 54 mL HClO4 (70%) 11 mL HClO4 (60%), 65 mL methanol (absolute), 24 mL 26–28 butyl cellosolve Electrolytes composed of HClO4 (60%) and glacial acetic acid 940 mL acetic acid, 60 mL HClO4 900 mL acetic acid, 100 mL HClO4 800 mL acetic acid, 200 mL HClO4 Electrolytes composed of mixed acids or salts 995 mL ethanol (absolute), 100 mL n-butyl alcohol, 109 g AlCl3 ⋅ 6H2O (hydrated aluminum chloride), 250 g ZnCl2 (zinc chloride) (anhydrous) 11.1% hydrofluoric acid, 59% lactic acid, 24.6% sulfuric acid, 3.6% dimethyl sulphoxide, 1.7% glycerine

(a) Chemical components of electrolytes are listed in the order of mixing. Except where otherwise noted the electrolytes are intended for use at ambient temperatures in the approximate range of 18–38 °C (65–100 °F), and with stainless steel cathodes. Absolute SD-3A or SD-30 ethanol can be substituted for absolute ethanol. (b) One of the best electrolytes for universal use. (c) Polish only. (d) Electrolyte and voltage for electropolishing as described in Metallography and Microstructure, Vol 9, Metals Handbook, 9th ed., (e) Good general-purpose electrolyte. (f) Source: J. Delleg, Metallography, Vol 7, 1974, p 357–360

In developing a suitable procedure for electropolishing a metal or alloy, it is generally helpful to compare the position of the major component of the alloy with elements of the same general group in a periodic table and to study the phase diagram, if available, to predict the number of phases and their characteristics. Single-phase alloys generally are easy to electropolish, whereas multiphase alloys are likely to be difficult or impossible to polish with electrolytic techniques. In multiphase alloys, the rates of polishing of different phases often are not the same. Polishing results depend significantly on whether the second or third phases are strongly cathodic or anodic with respect to the matrix. The matrix is dissolved preferentially if the other phases are relatively cathodic, thus causing the latter to stand in relief. Preferential attack can also occur at the interface between two phases. For titanium and titanium alloys, electropolishing can be effectively done with mixtures of perchloric acid (HClO4). However, mixtures of HClO4 and acetic anhydride are extremely dangerous to prepare and are even more unpredictable to use. Many industrial firms and research laboratories and some municipalities forbid the use of such potentially explosive mixtures, which have caused fatalities and property damage in some accidents. These mixtures also are highly corrosive to the skin, and the vapors of acetic anhydride can cause severe damage by inhalation. These hazards are considered sufficient reason for recommending that mixtures of HClO4 and acetic anhydride not be used, despite their effectiveness as electropolishing electrolytes. To avoid using mixtures of acetic and perchloric acid, electrolytes based on mixed acids or salts have been developed (see Table 11.5). For example, pure titanium (99.9% titanium) has been successfully electroplated with an electrolyte solution of 11.1% hydrofluoric acid, 59% lactic acid, 24.6% sulfuric acid, 3.6% dimethyl sulfoxide, and 1.7% glycerine. Polishing occurs with an applied voltage of 24 to 35 V at 97 mA/cm2 (see Fig. 11.4).

Current-voltage curve for electropolishing of commercially pure titanium in a mixed acid solution. Polishing occurs on the plateau.

Fig. 11.4

Cleaning and Finishing / 91

Wire Brushing Wire brushing of titanium alloys is not recommended when other finishing methods, such as buffing, can accomplish the objective. Wire brushing with a silicon carbide abrasive grease has been used successfully to remove burrs, break sharp edges from edge radii, and blend chamfers. However, wire brushing of titanium to remove surface scratches or oxide films has resulted in serious defects. In one instance, a stiff-bristled wire brush removed surface scratches and oxide films, but the surface was pitted by the wire tips. To avoid pitting, softer wire bristles were tried. The surface of the titanium acquired a burnished appearance, surface layers were cold worked, and grinding scratches, instead of being removed, were filled with smeared metal. These conditions are clearly detrimental to the fatigue properties of titanium alloys.

Removal of Grease and Other Soils Removal of grease, oil, and other shop soils from titanium parts normally is accomplished with the same type of equipment and the same cleaning procedures used for stainless steel and high-temperature alloy components. Certain aspects of conventional processing, however, must be modified or omitted when titanium alloys are being cleaned. Vapor degreasing normally employs either trichlorethylene or perchlorethylene. Under certain conditions, these solvents are known to be a cause of stress-corrosion cracking in titanium alloys. Methylethyl ketone is used as a cleaner in situations where chlorinated solutions are not desired. Moreover, environmental conditions can dictate ability to use some solutions. All titanium parts should be acid pickled after vapor degreasing to remove residual chlorine. Other cleaning methods use chemicals that, if they are left to dry on the part, can have a harmful effect on the properties of titanium. These chemicals include:

Coating thickness depends on immersion time. In all three baths, a specific time is reached after which the coating weight remains essentially constant. In the fluoride-phosphate baths, a maximum coating weight is reached at some time before this equilibrium point. The maximum coating weight is obtained in about 2 min in the low-temperature bath and in about 10 min in the two other baths. Results of extensive wire-drawing experiments, given in Table 11.7, illustrate the effectiveness of conversion coatings when used with various lubricants. Reciprocating wear tests showed that conversion coatings and oxidized surfaces provided some improvement in wear characteristics, but when conversion-coated samples were also oxidized, a marked improvement was noted. The conversion coating increases the oxidation rate of titanium at about 425 °C (800 °F) and can increase oxidation rates at temperatures up to 595 °C (1104 °F). The original coating is retained above the titanium oxide layer. High-speed rotary tests have indicated marked improvement in the wear characteristics of the metal after conversion coating and lubricating with one part of molybdenum disulfide and two parts thermosetting eponphenolic resin. Conversion coatings are easily removable without excessive loss of metal by pickling in an aqueous solution containing 20 wt% nitric acid and 2 wt% hydrofluoric acid.

for the retention of lubricants. Titanium has a severe tendency to gall, as noted previously. Lack of lubricity creates serious problems in applications involving the contact of moving parts in various forming operations. Conversion coatings are applied to titanium alloys by immersing the material in a tank containing the coating solution. Spraying and brushing are alternate methods of application. One coating bath consists of an aqueous solution of sodium orthophosphate, potassium fluoride, and hydrofluoric acid. It can be used with various constituent amounts, immersion times, and bath temperatures. The resultant coatings are composed primarily of titanium and potassium fluorides and phosphates. Several bath coating solutions are listed in Table 11.6. The control of pH and immersion time is important. Dissolved titanium and the active fluoride ion make it impossible to use glass electrodes for pH measurements. Indicator paper and colorimetry are the most satisfactory methods for measuring in the degreasing and chemical immersion baths, which are held in the pH range from 5 to 7. The pickling bath is quite acidic, and titrametric analysis offers the most practical method of control. When the bath is in the proper coating range, a 20 mL (0.70 fluid oz) sample in 100 mL (3.4 fluid oz) of water neutralizes 11.8 to 12.0 mL (0.4–0.41 fluid oz) of normal sodium hydroxide when using a phenolphthalein indicator.

Table 11.6

Conversion coating baths for titanium alloys Amount

Bath No.

Bath solution

Composition

1

Degreasing solution

2

Pickling solution

3

Chemical immersion solution

Na3PO4·12H2O KF⋅2H2O HF solution(a) Na3PO4⋅12Η2O KF⋅2H2O HF solution(a) Na2B4O7⋅10H2O KF⋅2H2O HF solution(a)

g/L

50 20 11.5 50 20 26 40 18 16

Temperature

oz/gal

°C

°F

pH

Immersion time, min

6.5 2.6 1.5 6.5 2.6 3.4 5.2 2.3 2.1

85

185

5.1–5.2

10

27

81

<1.0

1–2

85

185

6.3–6.6

20

(a) Hydrofluoric acid, 50.3% by weight

• Soda ash, borate, silicates, and wetting agents commonly used in alkaline cleaners

• Kerosene and other hydrocarbon solvents •

used in emulsion cleaners Mineral spirits employed in hand-wiping operations

Table 11.7 Comparisons of the effectiveness of some conversion coatings in the wire drawing of titanium Coating

Bare

Residues of all these cleaning agents must be completely removed by thorough rinsing. In order to ensure a surface that is free of contaminants, rinsing is frequently followed by acid pickling.

Chemical Conversion Coatings

Bare Degreasing bath Pickling bath Pickling bath Pickling bath(a) Chemical immersion bath Chemical immersion bath

Chemical conversion coatings are used on titanium to improve lubricity by acting as a base

Drawing compound

Total reduction, %

No. of passes

No. of coats

Final condition

Molybdenum disulfide with grease Soapy wax Molybdenum disulfide with grease Molybdenum disulfide with grease Soapy wax Molybdenum disulfide with grease Lacquer molybdenum disulfide Molybdenum disulfide with grease

…

0

…

Galled

… 85

0 8

… 2

Galled Smooth

94

17

7

Smooth

68 70

7 7

3 1

Galled Smooth

63

8

2

Smooth

63

8

3

Smooth

(a) Coating heated for 1 h at 425 °C (795 °F)

92 / Titanium: A Technical Guide treatment can be done in an air atmosphere, and a light oxide film forms on unplated areas.

Other Coatings and Procedures

Solution No.

1 2

Type of solution(a)

Composition of solution

Acid dip Dichromate dip

60% HF, 1 vol, 69% HNO3, 3 vol Na2Cr3O7 ⋅ 2H2O, 290 g/L (39 oz/gal), 60% HF, 55 g/L (7.3 oz/gal), H2O, remainder(b)

Operating temperature

Solution No. 1 2

°C

°F

Cycle time, s

Room temperature 82–100 180–212

(c) 20

(a) For preparation of Ti-6Al-4V and Ti-4Al-4Mn. (b) Distilled or deionized water. (c) Immerse to evolution of red fumes

Fig. 11.5

Processing sequence for electroplating copper on titanium alloy parts

Electroplating on Titanium Copper Plating. The electrodeposition of copper on titanium and titanium alloys provides a basis for subsequent plating. A flowchart outlining the processing sequence for copper plating titanium is shown in Fig. 11.5. After cleaning and before plating, the surface of the titanium must be chemically activated by immersion in both an acid dip and a dichromate dip to obtain adequate adhesion of the plated coating. The compositions and operating temperatures of these activating solutions are in the tabular area of Fig. 11.5. Water purity is critical in the composition of activating solutions, although technical-grade chemicals are as effective as, and can be substituted for, chemicals of the chemically pure grade. In both the acid and dichromate baths, hydrofluoric acid content is most critical and must be carefully controlled. After proper activation, titanium can be plated in a standard acid copper sulfate bath. The adhesion of the deposited copper is better than that of 60-40 solder to copper, and the deposit successfully withstands the heat of a soldering iron. The normal thickness of the plated deposit is about 25 μm (1 mil). Copper-plated titanium wire is available commercially. The outstanding property of this material is the lubricity of its copper-plated surface. The wire can be drawn easily and can be threaded on rolls. Such wire has been used in applications that require electrical surface conductivity. The titanium wire is plated continuously at a speed of about 60 m/min (200 ft/min) in a copper fluoborate acid bath at a current density of 7.5 to 12.5 A/dm2 (75–125 A/ft2). The final copper deposit is a thin flash coating. Higher current densities up to 150 A/dm2 (1500 A/ft2) have been tried, but if the resultant copper coating is too thick, adhesion is poor.

Platinum Plating. Although titanium is not satisfactory as an anode material because of an electrically resistant oxide film that forms on its surface, application of a thin film of platinum to titanium results in a material with excellent electrochemical properties. Theoretically, the thinnest possible film is sufficient to give the highly desirable low-overvoltage characteristics of platinum; furthermore, the film need not be continuous or free of defects to be effective. A particularly significant use for platinumcoated titanium is for anodes in the chlorinecaustic industry. Some horizontal-type chlorine cells use expanded metal anodes. From 1.3 to 2.5 μm (0.05–0.1 mil) of platinum is applied to the anode surface. Replating of the anodes may be required after about 2 years, depending on the operating conditions. The attrition rate for platinum appears to be about 0.6 g/tonne (0.5 g/ton) of chlorine. Several platinum and electrode suppliers developed reliable methods for platinum plating of titanium. Most use proprietary solutions. A platinum diamino nitrite bath has been used successfully to apply platinum plate to titanium. In this and other procedures, certain precautionary steps are required to achieve adherent, uniform plates. The surface must be cleaned thoroughly and etched in hydrochloric or hydrofluoric acid to produce a roughened surface. Some procedures also involve a surface activating treatment just before plating. Immersion for 4 min in a solution of glacial acetic acid (895 mL, or 30 fluid oz) containing hydrofluoric acid (125 mL, or 4 fluid oz, of 52% hydrofluoric acid), followed by a prompt rinse, appears to be an effective activating treatment if performed immediately before plating. A postplating treatment, consisting of heating to between 400 and 540 °C (750 and 1000 °F) for a period of 10 to 60 min, stress relieves the plate and improves adhesion. This

Coatings for Emissivity. Electrodeposits and sprayed coatings of gold on titanium are being used to provide a heat-reflecting surface that reduces the temperature of the base metal. Gold-coated titanium has been used for jet engine components. The gold coating is applied by spraying a gold-containing liquid on chemically clean titanium sheet. This is followed by a baking treatment. Normal coating thickness is about 25 μm (1 mil). Ion Implantation Processes. Wear resistance of titanium and titanium alloys can be improved by ion implantation. Ion species, such as boron, carbon, and nitrogen, create hard phases when implanted in titanium and titanium alloys. The most commonly implanted species are nitrogen and carbon, and implantation in titanium has been done commonly on Ti-6Al-4V. An improvement in wear behavior is effected by the increase in surface hardness that is achieved by ion implantation. The hardening effect achieved in implantation of nitrogen into Ti-6Al-4V is shown in Fig. 11.6; the maximum hardness increase is in excess of 170% at a depth of 50 nm below the surface. In this case, the microstructure of nitrogen-implanted Ti-6Al-4V consisted of a fine dispersion of TiN precipitates in a deformed nitrogen-rich matrix, which resulted in a hardening of the surface region and the presence of surface compressive residual stresses. The relative effects on hardness of nitrogen- and carbon-implanted Ti-6Al-4V are shown in Fig. 11.7. The ion implantation process involves being able to accelerate ions of elements to a suffi-

Percent increase in hardness with depth into material for nitrogen ion implanted in the alpha-beta alloy Ti-6Al-4V

Fig. 11.6

Cleaning and Finishing / 93

Percent increase in hardness with depth into material for nitrogen ion or carbon ion implanted in the alpha-beta alloy Ti-6Al-4V

Fig. 11.7

ciently high velocity so that they are able to penetrate the surface of the material in which the ions are being implanted. The depth of penetration and the total number of ions delivered into the surface are a function of many variables, including the atomic masses of the implant atom (ion) and the target species. Machin-

ery is now available commercially to provide the necessary ion implantation on a wide range of materials. In the titanium field, the principal interest is in the enhancement of wear resistance in critical applications, such as joints in biomedical prosthetics. An example of the application of an ion-implanted titanium alloy is in total joint replacement, where the excellent biocompatibility combined with its specific mechanical properties make the use of Ti-6Al-4V desirable. The combination of this alloy and ultrahigh-molecular weight polyethylene is unsatisfactory because of unacceptably high levels of wear in the joint. Ion implantation can significantly improve this situation, and the use of the process in the improvement of titanium alloy biomaterials has reached some degree of commercial maturity. A more mundane commercial application is titanium gears for a variety of low-load aircraft applications. Titanium alloys are used because of weight savings, and they are successfully used because problems of scuffing can be reduced by nitrogen implantation on titanium components. Titanium in hydraulic systems is often used because of the corrosion-resistant nature of the metal and its alloys, but ion implantation has been used to reduce galling

against both steel and other titanium alloy counterface materials. Salt Bath Processes. A number of salt bath treatments have been developed for titanium, the oldest of which is probably the Tiduran process. In this process, the titanium component is immersed in a cyanide-base salt bath at 800 °C (1470 °F), usually for 2 h. Carbon and nitrogen, and sometimes small amounts of oxygen, diffuse into the surface where they interact with titanium ions to produce a hardened diffusion zone. The maximum hardness achieved in the process is in the range of 750 to 800 HV, falling progressively into the substrate, giving a case depth of about 50 μm. A uniform 10 μm is removed from the surface of the metal during the process. Components can usually be used in the as-coated condition, or they can be given a light pickle to remove the black surface. Liquid-State Alloying. This process involves surface melting (to a depth of about 0.5 mm, or 0.02 in., or more) by rapid heating with an electron beam or laser. The liquid pool thus allows alloying with hardening species, which are either predeposited on the surface or deposited on the surface during heating. An example of liquid-state alloying is a laser-assisted gas nitriding process that produced case depths of 0.5 mm (0.02 in.) in titanium.

Titanium: A Technical Guide Matthew J. Donachie, Jr., p95-121 DOI:10.1361/tatg2000p095

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 12

Relationships among Structures, Processing, and Properties The microstructures of titanium can be complex. They are a direct result of composition, processing, and postprocessing heat treatment. Properties of particular interest are:

several factors, or by a combination of factors, including composition, that lead to a specific microstructure. The most important of these factors include:

• Tensile yield strength (TYS) and ultimate

• Amounts of specific alloying elements and

• • •

• Melting process used to make primary ingot • Number of melting steps • Method for mechanically working ingots

•

tensile strength (UTS) Ductility Toughness Cyclic properties, including low-cycle fatigue (LCF) and high-cycle fatigue (HCF) Crack propagation in fatigue (da/dN) or under environmental constraints (da/dt)

The mechanical properties of titanium alloys in a finished shape can be affected by one of

impurities

into mill products

• Steps in forging a shape • Casting process and volume of cast article • • • •

plus use of densification techniques, such as hot isostatic pressing (HIP), to reduce casting porosity Powder metallurgy (P/M) process, including method of making powder Joining process used to fabricate a structure Postprocessing heat treatment or final step employed in working or fabrication Machining process and surface treatment

Microstructure of titanium alloy classes (e.g., alpha-beta) is covered in Chapter 3, and that Chapter should be used as a reference when reading the current Chapter. As a reminder, titanium alloys are grouped into classes: alpha, near alpha, alpha-beta (alpha plus beta), and beta. This grouping reflects the customary room-temperature presence of the alpha phase (hexagonal close-packed) and/or the beta phase (body-centered cubic) structure in a particular alloy. Transformations on heat-

ing and cooling (from the high-temperature beta region) and phase compositions are altered by alloying additions, which are typically classified as alpha stabilizers or beta stabilizers. Vanadium, molybdenum, iron, and hydrogen are beta stabilizers, while aluminum, oxygen, and nitrogen are examples of alpha stabilizers.

Basic Properties of Titanium and Its Alloys Pure titanium can be strengthened appreciably by alloying, processing, and postprocessing heat treatment, and the alloys still retain low density levels. Consequently, their mechanical properties are attractive, particularly with respect to ratios of strength to density. Figure 12.1 indicates this ratio for pure titanium, steel, and high-strength aluminum- and magnesium-base alloys. Table 12.1 compares typical properties for pure titanium and two titanium alloys with those of ultrahigh-strength steel on an absolute and on a density-adjusted basis. The table shows that titanium alloys are remarkably strong in a comparison of strength to density (weight). The physical properties of titanium are largely unaffected by processing. However, the kinetics of the titanium beta-phase transformations that occur during heating, cooling, and aging strongly influence microstructure and,

Table 12.1 Comparison of typical strength-to-density values for several titanium alloys and a steel at 20 °C (68 °F) Density

of yield strength to density as a funcFig. 12.1 Ratio tion of temperature for several titanium alloys, compared to some steel, aluminum, and magnesium alloys

Tensile strength

Tensile strength/density

Metal

g/cm3

lb/in.3

MPa

ksi

MPa ÷ g/cm3

ksi ÷ lb/in.3

CP titanium Ti-6Al-4V Ti-4Al-3Mo-1V Ultrahigh-strength steel (4340)

4.51 4.43 4.51 7.9

0.163 0.160 0.163 0.29

400 895 1380 1980

58 130 200 287

89 202 306 251

356 813 1227 990

96 / Titanium: A Technical Guide therefore, mechanical properties. Thus the mechanical properties of titanium alloys can be directly related to the processing and postprocessing heat treating sequences. Elastic properties are affected by chemistry and texture, but they are not particularly affected by heat treatment. The modulus of titanium can vary with alloy type (beta versus alpha) from as low as approximately 93 GPa (13.5 × 106 psi) up to approximately 120.5 GPa (17.5 × 106 psi). For reference, this is about 50% greater than the modulus for aluminum alloys and approximately 60% of the modulus for steels and nickel-base superalloys. For a given phase, the modulus is a function of direction of measurement in the crystal. Consequently, by arranging crystal orientation through grain alignment (texturing) of titanium alloys, one can achieve certain grain orientations that result in the attainment of higher modulus (or lower modulus) than customarily found for an alloy.

Structure and Hardening of Titanium Structure, for our purposes, is defined as the macrostructure and microstructure (i.e., macroappearance and microappearance) of a polished and etched cross section of metal visible at magnifications up to and including 10,000×. Two other microstructural features that are not determined visually but are determined by other means, such as x-ray diffraction or chemistry, are phase type (e.g., alpha, beta) and texture (orientation) of grains. The grain size, grain shape, and grain boundary arrangements in titanium have a very significant influence on mechanical properties; it is the ability to manipulate the phases/grains present as a result of alloy composition that is responsible for the variety of properties that

Fig. 12.2 drogen

Ductility of alpha titanium versus test temperature showing embrittling effects of hy-

can be produced in titanium and its alloys. Transformed beta-phase products in alloys can affect tensile strengths, ductility, toughness, and cyclic properties. The basic strengthening effects of alloy elements must be added to these effects. Role of Alloy Elements with Comparable Atom Size. Some alloy elements are more or less comparable in atom size to the atom size of titanium and can dissolve as a mixture in titanium, substituting for titanium atoms. Alternately, they can act to form: 1) another competing phase, such as the intermetallic compound Ti3Al or 2) a different mixture (of titanium and the second element), which takes the crystal structure of the second, but comparably sized, alloy element. Certain alloy elements favor alpha-phase stabilization, and other alloy elements favor beta phase. The actual situation is somewhat more complex than this (see Chapter 3). Alloy elements that dissolve in titanium alloys produce strengthening by interfering with the plastic deformation process. Such strengthening is known as solid-solution strengthening (SSS). In the case of comparably sized alloy elements dissolved in titanium, the hardening is referred to as substitutional SSS. Elements that produce second phases generally interfere with deformation more effectively than those that dissolve, and so second phases generally produce greater hardening of titanium than is produced by SSS. The normal role of comparably sized elements in strengthening titanium is not only to provide direct SSS, but also to assist in controlling the microstructure through their effect on the amounts of alpha and beta phases, tendency to form compounds, and rate of phase transformation, among other characteristics. Role of Interstitial Elements. Interstitial elements are those elements that are significantly smaller than the titanium atom and so can dissolve in the titanium phase crystal lattice as solid solutions without substituting for titanium atoms. Of course, some interstitial elements also can form second phases with titanium. As is the case for comparably sized elements, in-

Fig. 12.3

terstitial elements can have a preference for one phase over another in titanium. A significant influence on mechanical behavior of commercially pure (CP) titanium is brought about by hydrogen, nitrogen, carbon, and oxygen, which dissolve interstitially in titanium and have a potent effect on mechanical properties. These effects carry over to titanium alloys in varying degrees.

Interstitial Effects in Titanium Hydrogen in Commercially Pure Titanium. The solubility of hydrogen in alpha titanium at 300 °C (572 °F) is approximately 8 at.% (~0.15 wt%, or ~1000 ppm by weight). Hydrogen in solution has little effect on mechanical properties. Damage is caused by hydrides, which form as hydrogen diffuses into the material during exposure with either gaseous or cathodic hydrogen. Upon precipitation of the hydride, the ductility suffers. Hydrogen damage of titanium and titanium alloys, therefore, is manifested as a loss of ductility (embrittlement) and/or a reduction in the stress intensity threshold for crack propagation. Figure 12.2 shows the effect of hydrogen on reduction of area. Note that no embrittlement is found at 20 ppm of hydrogen; 20 ppm corresponds to approximately 0.1 at.% H. The data in Fig. 12.3 and 12.4 show that, independent of the heat treatment, a concentration as low as 20 ppm has little effect on the impact strength, another measure of embrittlement. Note, however, that as little as 0.5 at.% H (~100 atom ppm) can cause measurable embrittlement. Slow cooling from the alpha region—for example, 400 °C (752 °F)—allows sufficient hydride to precipitate to reduce the impact energy. Because the phenomenon depends on both hydrogen diffusion and hydride formation, there may be a peak in hydrogen embrittlement as a function of temperature. The exact level of hydrogen at which a separate hydride phase is formed depends on the composition of the alloy

Effects of hydrogen content and heat treatment on the impact energy of alpha titanium

Relationships among Structures, Processing, and Properties / 97 and the previous metallurgical history. Hydrogen, if picked up during processing, can be removed by vacuum annealing, but this poses an added expense and processing step. Rapid cooling by water quenching from 400 °C (752 °F) suppresses hydride precipitation, thereby retaining the high impact energy. However, aging at room temperature, even for a few days, allows sufficient hydride to precipitate, thus lowering the impact energy (Fig. 12.3). Therefore, even though hydride precipitation can be controlled by heat treatment, aging at 25 °C (77 °F) results in sufficient precipitate formation and coarsening to embrittle an alloy. The only practical approach to control the hydrogen problem is to maintain a low concentration of the element. As a result, CP titanium usually has a maximum allowable hydrogen content of about 0.015 wt% (approximately 100 ppm by weight). For example, for the grades of CP titanium shown in Table 12.2, the level is about 0.01%. Oxygen and nitrogen in commercially pure titanium have a potent effect on strength, as shown in Fig. 12.5. As the amounts of oxygen and nitrogen increase, the toughness decreases until the material eventually becomes quite brittle. Embrittlement occurs at a concentration considerably below the solubility limit. Note that the allowed oxygen content is higher than the allowed nitrogen content, according to Table 12.2. This is consistent with the relative effects shown in Fig. 12.5. This figure also indicates why grades of titanium with higher allowable oxygen and nitrogen contents have higher tensile strengths. (See Table 12.2 for comparison among grades.) It should be noted that even the CP titanium grade with the highest interstitial content has 40 Slow cooled Quenched from 400 °C Quenched and aged at room temperature

good ductility. However, due to the oxygen and nitrogen present, in a pure titanium, which contains oxygen and nitrogen, the alpha formed from beta has a much more distinctive Widmanstätten structure than does a titanium essentially free of these elements (Fig. 12.6). This effect, however, can have little direct bearing on the mechanical properties. The addition of carbon, up to about 0.3%, strengthens titanium greatly and reduces ductility somewhat (Fig. 12.5). Interstitials in Titanium Alloys. Although the two preceding discussions deal with interstitial effects in CP titanium, the concepts can be carried over to the commercially available titanium alloys. The concepts are valid for any titanium alloy because the oxygen and nitrogen levels play a role in defining alloy strength and, in particular, ductility. The extra low interstitial (ELI) levels specified for some titanium alloys implicitly recognize the effect of reduced interstitials on ductility. ELI-type material is used for critical applications where enhanced ductility and toughness are produced by keeping interstitials at a very low level. Hydrogen is always kept at a low level to avoid embrittlement, yet there still remains concern about the most reasonable level to specify in both CP and alloyed titanium to protect against embrittlement while keeping manufacturing cost low.

Pure Titanium Mechanical Properties Structure. High-purity (99.9% or better) titanium is not a widely used commercial commodity. CP titanium grades, where the titanium content is less than about 99.55% by specification, are used and do not differ in general mechanical property response from that of the high-purity metal. High-purity and grades are treated as a single entity here for property discussion purposes. Pure titanium is single-phase alpha. As with any single-phase alloy, the microstructure of CP titanium depends on whether or not it has been cold worked and on the specific type of annealing employed. In addition, upon cooling from the beta region, which begins at 882 °C (l620 °F), the structure depends on the cooling process followed because the process directly affects the progression of the beta-to-alpha transformation and the final alpha grain size and shape. The equiaxed microstructure of titanium after annealing at 800 °C (1472 ° F) in the alpha region is shown in Fig. 12.7(a). Here the grain size—and, hence, properties—can be varied only by cold working and annealing. Properties typical of this microstructure are listed in the figure caption.

Table 12.2 Maximum interstitial content plus minimum mechanical properties for some titanium alloy grades Max interstitial content allowed, wt%

Max tensile strength

Min yield strength

N

C

O

H

MPa

ksi

MPa

ksi

Elongation, %

Reduction in area, %

1

0.03

0.10

0.18

241

35

172

25

24

30

2

0.03

0.10

0.25

345

50

276

40

20

30

3

0.05

0.10

0.35

448

65

379

55

18

30

4

0.05

0.10

0.40

0.0125(b) 0.0100(c) 0.0125(b) 0.0100(c) 0.0125(b) 0.0100(c) 0.0125(b) 0.0100(c)

552

80

483

70

15

25

Grade(a)

(a) Commercially pure alpha titanium for bars and billets (ASTM B 348-78). (b) Bars only. (c) Billets only

Room temperature impact strength, in./lb.

30

As quenched

20

Aged 1 day Aged 1 week

10 Aged 6 months

Aged 1 month Slow cooled 0

0

0.5

1.0 1.5 Atom, % hydrogen

2.0

2.5

Effects of hydrogen content and heat treatment on the impact energy of commercial purity titanium

Fig. 12.4

Effects of hydrogen, nitrogen, and carbon content on tensile properties and hardness of alpha titanium. Data of Jaffee are for samples annealed at 850 °C (1562 °F); those of Finlay are for samples annealed at 700 °C (1292 °F). Thus both sets refer to data well annealed in the α region. TS, tensile strength; YS, yield strength

Fig. 12.5

98 / Titanium: A Technical Guide Annealing in the beta region at 1000 °C (1832 °F) and then rapidly cooling to 25 °C (77 °F) by means of a water quench produces the typical structure shown in Fig. 12.7(b). Even rapid cooling does not suppress the beta-to-alpha transformation; the structure is entirely transformed to alpha. Note that the alpha grain boundaries are serrated and quite irregular. Properties typical of this structure are listed in the caption. This structure is stronger than the equiaxed structure developed by annealing only in the alpha region. For both treatments, the titanium is still quite ductile. Cooling slowly—for example, 20 h to 25 °C (77 °F)—produces the structure in Fig. 12.7(c). The structure is, again, completely alpha, but the grain boundaries are less irregular than those

produced upon cooling rapidly. This structure is somewhat weaker than that produced upon cooling rapidly, but it is still stronger than the equiaxed structure shown in Fig. 12.7(a). Properties. The titanium grades have varying amounts of impurities (e.g., carbon, hydrogen, iron, nitrogen, and oxygen). Some “modified” grades also contain small palladium additions (0.2Pd) and nickel-molybdenum additions (0.3Mo-0.8Ni). Because small amounts of interstitial impurities greatly affect the mechanical properties of pure titanium, it is not convenient to distinguish between the various grades of unalloyed titanium on the basis of chemical analysis. Titanium grade products are more readily distinguished by mechanical properties.

For a given level of interstitials and/or minor alloy element, properties of commercial grade titanium materials are primarily a function of grain size, grain shape, and amount of cold work in the metal. Annealed pure titanium (99.9%) has a level of flow stress comparable to that of mild steel. Figure 12.8 compares the

(a)

(b)

(a)

(b)

(c) Microstructure of commercially pure titanium after annealing in the alpha region or the beta region and cooling to ambient temperatures. (a) Annealed 1 h at 800 °C (1472 °F), water quenched, 0.2% yield strength: 124 MPa (18 ksi), tensile strength: 248 MPa (36 ksi), elongation: 80%; 100×. (b) Annealed 1 h at 1000 °C (1832 °F), water quenched, 0.2% yield strength: 228 MPa (33 ksi), tensile strength: 290 MPa (42 ksi), elongation: 60%; 100×. (c) Annealed at 1000 °C (1832 °F), furnace cooled, 0.2% yield strength: 165 MPa (24 ksi), tensile strength: 262 MPa (38 ksi), elongation: 60%; 100×. All optical micrographs

Fig. 12.7

(c)

Microstructures of commercial purity titanium with and without interstitial oxygen or nitrogen. (a) Relatively pure titanium, 150×. (b) Ti-0.3 wt% O alloy obtained after annealing in the beta region then cooling to 25 °C (77 °F), 150×. (c) Ti-0.3 wt% N alloy, 150×. All optical micrographs

Fig. 12.6

Relationships among Structures, Processing, and Properties / 99 stress-strain curves for high-purity titanium, an alpha-beta titanium alloy, and a beta titanium alloy with several mild steels and pure aluminum. Minimum room-temperature tensile properties are presented in Table 12.3 for various grade specifications. Figure 12.9 presents UTS as a function of temperature for CP and modified titanium grades. Although data are not provided here for grain size effects on titanium grades, it is generally accepted that fineness of structure (smaller grain size) is more desirable from the point of view of TYS in metallic materials. The UTS is not particularly affected by grain size, but ductility, as represented by elongation or reduction in area, generally is improved with smaller grain sizes. Ductility is a measure of toughness, but toughness is not normally at issue in CP titanium grades. Another measure of toughness is Charpy impact strength, which is compared for several grades in Fig. 12.9. T = 20 °C Ti-6Al-4V Ti-13V-11Cr-3Al 0.35% C steel Ti 99.9 0.15% C steel Al 99.5

Stress-strain curves for several titanium materials plus steel and aluminum. Titanium impurities (wt%) were 0.04 O2, 0.01 N2, 0.002 H2, 0.04 Fe, and 0.010 C.

Fig. 12.8

Elevated-temperature behavior of titanium grades has been studied, but these alloys are not customarily used at high temperatures. The near-alpha or alpha-beta alloys are the preferred materials where high-temperature mechanical properties are desired. With allowance for grain size effects and possible minor chemistry variations, cast CP titanium materials should behave in much the same way as wrought.

Alpha/Near-Alpha Alloys Alpha alloys, such as Ti-5Al-2.5Sn, Ti-6Al2Sn-4Zr-2Mo+Si, and Ti-8Al-1Mo-1V (see Table 2.2), are used primarily in gas turbine applications. Ti-8Al-1Mo-1V and Ti-6Al-2Sn4Zr-2Mo+Si are useful at temperatures above the normal range for the workhorse alpha-beta alloy, Ti-6Al-4V. Ti-8Al-1Mo-1V and Ti-6Al2Sn-4Zr-2Mo+Si alloys have better creep resistance than Ti-6Al-4V, and creep resistance is enhanced with a fine acicular (Widmanstätten) structure. In its normal heat-treated condition, Ti-6Al-2Sn-4Zr-2Mo+Si actually has a structure better described as alpha-beta, the alloy will continue to be considered in the alpha/near-alpha category here. Structures and Strengthening Concepts. The alpha alloys have alpha as their common phase at lower temperature, below approximately 800 °C (1472 °F). Generally speaking, alpha alloys contain much less beta phase than Ti-6Al-4V. Thus their properties in general are not altered greatly by heat treatment. Age hardening treatments are not very effective because they depend on beta-phase transformations to

Table 12.3 Chemistry and minimum tensile properties for various specifications for commercially pure and modified titanium grades at room temperature Tensile properties(a) Chemical composition, % max Designation

JIS class 1 ASTM grade 1 (UNS R50250) DIN 3.7025 GOST BT1-00 BS 19 –27t/in.2 JIS class 2 ASTM grade 2 (UNS R50400 DIN 3.7035 GOST BT1-0 BS 25–35 t/in.2 JIS class 3 ASTM grade 3 (UNS R50500) ASTM grade 4 (UNS R50700) DIN 3.7055 ASTM grade 7 (UNS R52400) ASTM grade 11 (UNS R52250) ASTM grade 12 (UNS R53400)

Ultimate strength

Yield strength

C

O

N

Fe

MPa

ksi

MPa

ksi

Minimum elongation, %

… 0.10

0.15 0.18

0.05 0.03

0.20 0.20

275–410 240

40–60 35

165(b) 170–310

24(b) 25–45

27 24

0.08 0.05 … … 0.10

0.10 0.10 … 0.20 0.25

0.05 0.04 … 0.05 0.03

0.20 0.20 0.20 0.25 0.30

295–410 295 285–410 343–510 343

43–60 43 41–60 50–74 50

175 … 195 215(b) 275–410

25.5 … 28 31(b) 40–60

30 20 25 23 20

0.08 0.07 … … 0.10

0.20 0.20 … 0.30 0.35

0.06 0.04 … 0.07 0.05

0.25 0.30 0.20 0.30 0.30

372 390–540 382–530 480–617 440

54 57–78 55–77 70–90 64

245 … 285 343(b) 377–520

35.5 … 41 50(b) 55–75

22 20 22 18 18

0.l0

0.40

0.05

0.50

550

80

480

70

15

0.10 0.10

0.25 0.25

0.06 0.03

0.30 0.30

460–590 343

67–85 50

323 275–410

47 40–60

18 20

0.10

0.18

0.03

0.20

240

35

170–310

25–45

24

0.10

0.25

0.03

0.30

480

70

380

55

12

(a) Unless a range is specified, all listed values are minimums. (b) Only for sheet, plate, and coil

effect strength improvements. Age hardening heat treatments can be deleterious to creep resistance. Therefore, alpha and near-alpha alloys are usually employed in the solution-annealed and stabilized condition. Solution annealing can be done at a temperature some 35 °C (63 °F) below the beta transus temperature, while stabilization is commonly produced by heating for 8 h at about 590 °C (1100 °F). These alloys are more susceptible to the formation of ordered Ti3Al, which promotes stress-corrosion cracking (SCC). (For more information on SCC, see Chapter 13.) The only strengthening mechanisms are cold work, cold work and annealing (to control the grain size), and solute additions for solid-solution strengthening. Alpha formers, such as aluminum and tin, can increase the strength of titanium by solid-solution strengthening. Both aluminum and tin have a significant effect on the mechanical properties of titanium: there is an increase in strength of approximately 55 MPa (8 ksi) for each 1% Al, and 28 MPa (4 ksi) for each 1% Sn. However, for zirconium the effect is only about 3.5 MPa (0.5 ksi) for each 1% addition. Thus, zirconium is not used to strengthen alpha titanium alloys.

Alpha-Beta Alloys The most important titanium alloy is the alpha-beta alloy Ti-6Al-4V. This alloy has found application for a wide variety of aerospace components and fracture-critical parts. With a strength-to-density ratio of 25 × 106 mm (1 × 106 in.), Ti-6Al-4V is an effective lightweight structural material and has strength-toughness combinations between those of steel and aluminum alloys. High-strength alpha-beta alloys include Ti-6Al-6V-2Sn and Ti-6Al-2Sn-4Zr-6Mo. Alpha is the dominant phase in all of these alloys, but it is dominant to a lesser extent in the high-strength alloys than in Ti-6Al-4V. These alloys are stronger and more readily heat treated than Ti-6Al-4V. This capability arises from the increased solid-solution strengthening afforded by tin and zirconium, which have relatively small effects on the transformation tem-

Commercially pure (CP) and modified titanium typical ultimate tensile strength (UTS) versus temperature

Fig. 12.9

100 / Titanium: A Technical Guide

Fig. 12.10

Distorted Widmanstätten alpha remaining as a result of limited working in the alpha-beta field. Rolled at 955 °C (1750 °F); 100×

perature, and from the increased amounts of beta phase that result from the larger vanadium and molybdenum additions. Structures and Strengthening Concepts. The alpha stabilizers aluminum and tin are added to titanium to promote stabilization of alpha phase over beta phase and to increase strength of titanium alloys by solid-solution hardening. The aluminum is balanced by beta stabilizers so that the resultant product has a mixture of alpha and beta phases available to control properties. The effectiveness of tin as a strengthener soon begins to level off, whereas it does not with aluminum. Still, a practical upper limit to the aluminum content is about 7%. Above this value, the alloy is difficult to hot work and susceptibility to environmental embrittlement is high. Embrittlement can occur at low temperatures as well when the aluminum content is excessively high. Alpha-favoring elements can be added to aid solid-solution hardening but should be kept to reasonable levels. The addition of beta-favoring elements can permit solution heat treatment at lower temperatures and can solid-solution harden the alloy still further. Beta-favoring elements can also retard alpha formation so that beta is transformed to martensite or is retained to transform

Fig. 12.11 °F); 250×

later into alpha upon reheating (stabilizing, aging) to temperatures from 427 to approximately 816 °C (800–1500 °F). The relative amounts of primary alpha (present at high-temperature solution anneal), retained beta, and martensitic alpha are a function of chemistry and prior thermal treatment. However, they are also a function of mechanical processing history. One of the main purposes of wrought processing of titanium alloys, as indicated in Chapter 5, is to control microstructure and, thus, the properties themselves. Tensile strength, fatigue strength, and toughness, as well as creep resistance, all can be better in forgings than in cast, powder, or other wrought forms. Proper working of titanium alpha-beta alloys enables the microstructure at working temperature to be more homogenous, while any gross microstructural anomalies, as shown in Fig. 12.10 and 12.11, are removed or prevented from forming. The effects of prior processing on microstructure are quite varied. Extensive hot working in the alpha-plus-beta field is required to produce the proper microstructure typified by Fig. 12.12 for Ti-6Al-4V alpha-beta alloy. If hot working of the alpha-plus-beta phases has been limited, microstructures, such as that shown in Fig. 12.10, will occur. As can be ob-

Grain boundary alpha remnants not broken up by forging due to improper cooling from the beta region. Rolled at 940 °C (1725

served, the Widmanstätten platelets are quite distorted but are not yet broken up. This condition is not particularly detrimental to fracture toughness, although it can affect fatigue crack propagation (FCP). When alloy Ti-6Al-4V is processed improperly after heating into the beta field, alpha phase can form preferentially along the priorbeta grains. Extensive hot work is required to break up such structures. An example of grain boundary alpha not completely broken up is shown in Fig. 12.11. Because cracks tend to propagate in, or near, interfaces, this type of structure can provide loci for crack initiation and propagation and thereby lead to premature failure. Microstructural control is effected by using proper combinations of hot work and heat treatment. Heat treatment alone does not suffice to convert the Widmanstätten structure to an equiaxed form; therefore, heat treatment alone is not used unless a transformed structure is desired. Grain refinement cannot be obtained by heat treatment, and, after one beta to alphaplus-beta sequence has been accomplished, additional cycles (alpha-plus-beta to beta to alpha-plus-beta) have no effect on the basic crystallographic texture, although the structure may be coarsened as a consequence of beta grain growth. Table 8.1 gives a summary of heat treatments used for alpha-beta titanium alloys. Property Development. When alpha-beta titanium alloys are heat treated high in the alpha-beta range and then cooled, the resulting structure is called equiaxed because of the presence of globular (equiaxed) primary alpha in the transformed beta (platelike) matrix. When a 100% transformed beta structure is achieved by cooling from above the beta transus, the structure can be called acicular, or needlelike. Table 12.4 lists the strength advantages and disadvantages of both structural types. Table 12.5 clearly indicates that higher yield strength is favored by equiaxed structures. Table 12.5 also indicates that better toughness is characteristic of transformed, or acicular, structures.

Typical microstructure of alpha-beta titanium alloy Ti-6Al-4V solution treated close to the beta transus. 1010 °C (1850 °F), 1 h, encapsulated cool; 500×

Fig. 12.12

Relationships among Structures, Processing, and Properties / 101 Generally speaking, alpha-beta alloys would be annealed just below the beta transus to produce a maximum of transformed acicular beta with approximately 10% of equiaxed alpha present. Some titanium alloys—for example, Ti-6Al-2Sn-4Zr-2Mo—are given beta heat treatments to enhance high-temperature creep resistance. (Castings and powder products can be given a beta anneal, too, in order to break up the structure, though not necessarily to optimize creep strength.) Alpha-Beta Alloy Hardenability. In actual components, the structure of titanium alphabeta-type alloys is controlled not only by how much working is done and by how close to, or how much above, the beta transus the alloy is processed, but also by the section size of the component. Ideally, alloys should have good hardenability, that is, the ability to reach desired cooling rates and attendant microstructures in fairly thick sections. Many alpha-beta alloys do not have great hardenability. Ti-6Al-4V only has sufficient hardenability to be effectively heat treated to full property levels in sections less than 25 mm (1 in.) thick. Thicker sections can be heat treated, but center regions will not achieve desired microstructures and so optimum property levels may not be achieved. For alpha-beta alloys with low hardenability, the effective cooling rates for optimum property achievement can be dramatically reduced. Thick sections can behave as if they were furnace cooled, while thinner ones can display, at room temperature, a microstructure more characteristic of a rapid cooling. Rapid cooling, in general, promotes finer structure and better properties; thus, thick sections possess lower tensile strengths than thinner ones. The effects of variations in cooling rates can be seen in Table 12.6 for alloy Ti-6Al-4V. It is seen that furnace cooling produces lower strengths than does water quenching.

Microstructure

Equiaxed

Acicular

Ti-6Al-4V Ti-6Al-6V-2Sn Ti-6Al-2Sn4Zr-6Mo

An alloy is considered to be a beta alloy if it contains sufficient beta stabilizer alloying element to retain the beta phase without transformation to martensite on quenching to room temperature. A number of titanium alloys (see

Yield strength

Thermal treatment

Tensile strength

MPa

ksi

MPa

ksi

Elongation at fracture, %

Reduction, in area, %

834

121

937

136

19

46

90% alpha; 10% beta

951

138

1117

162

17

60

855

124

965

140

17

43

50% primary alpha; 50% alpha prime + alpha double prime + retained beta 90% alpha; 10% beta

923

134

1117

162

15

54

955 °C (1751 °F) furnace cooled 955 °C (1751 °F) water quenched

Microstructure at 25 °C (77 °F), ~vol% phases

60% primary alpha; 40% alpha prime + alpha double prime + retained beta

Advantage

Higher ductility and formability Higher threshold stress for hot-salt stress corrosion Higher strength (for equivalent heat treatment) Better hydrogen tolerance Better low-cycle fatigue (initiation) properties Superior creep properties Higher fracture toughness values

Table 12.5 Typical yield and fracture toughness of several alpha-beta titanium alloys

Alloy

Beta Alloys

Table 12.6 Typical room-temperature tensile properties and corresponding microstructure for Ti-6Al-4V for different thermal treatments

900 °C (1652 °F) furnace cooled 900 °C (1652 °F) water quenched

Table 12.4 Relative advantages of equiaxed and acicular microstructures

sponse is the ability to cool all section locations to produce a fine martensitic structure before aging. See the section “Alpha-Beta Alloy Hardenability”. Aging of titanium alpha-beta alloys can be used to stabilize the alloy during service exposure against additional transformation of unstable martensite and retained beta. While true aging tends to occur at temperatures in the approximate range of 538 to 593 °C (1000–1100 °F), stabilization can occur at that point, or up to 38 °C (100 °F) higher. Longitudinal versus Transverse Properties. Another influencing factor about titanium alloy strengthening is the effect of testing direction. The texture and mechanical working effects on directionality of structure can be significant, especially in bar, plate, or sheet mill products. Table 12.8 shows the effect of test direction on properties of textured Ti-6Al-2Sn4Zr-6Mo plate. Substantial differences are obtained with test direction.

Table 12.6 also indicates a characteristic of higher-temperature thermal treatment. Here the temperature that is closer to, but below, the beta transus promotes better yield strengths than a treatment lower in the alpha-beta temperature range. Aging and Stability in Alpha-Beta Alloys. One of the least understood concepts in the behavior of alpha-beta titanium alloys is that of aging. With few exceptions, titanium alloys do not age in the classical sense, where a secondary, strong intermetallic compound appears and strengthens the matrix by its dispersion. A dispersion is produced on aging of alpha-beta alloys, but it is thought to be beta dispersed in the alpha or martensitic alpha prime. Beta is not materially different from alpha phase with respect to strength; however, the effectiveness of strengthening in titanium alloys appears to center in the number and fineness of alpha-beta phase boundaries. Annealing and rapid cooling, which maximize alpha-beta boundaries for a fixed primary alpha content, along with aging, which can promote additional boundary structure, can significantly increase alloy strength (Table 12.7). It is interesting to note that, owing to solution treatment temperature variations, the strength for Ti-6Al-4V alloy may be varied by about 10% while ductility remains unchanged. Also, there can be a slight variation in strength after aging treatment. The key to aging re-

Alpha morphology

Yield strength MPa

ksi

Equiaxed 910 130 Transformed 875 125 Equiaxed 1085 155 Transformed 980 140 Equiaxed 1155 165 Transformed 1120 160

Fracture toughness (KIc) MPa m ksi in.

44–66 88–110 33–55 55–77 22–23 33–55

40–60 80–100 30–50 50–70 20–30 30–50

Table 12.7 Effect of aging on room-temperature tensile properties of alpha-beta titanium alloy Ti-6Al-4V Yield strength

Tensile strength

Thermal treatment

MPa

ksi

MPa

ksi

Elongation at fracture, %

Reduction in area, %

955 °C (1751 °F) water quenched + age 1 955 °C (1751 °F) water quenched + age 2 900 °C (1652 °F) water quenched + age 1 900 °C (1652 °F) water quenched + age 2

951 1069 924 1013

138 155 134 147

1117 1186 1117 1117

162 172 162 162

17 17 15 15

60 56 54 48

Table 12.8 Effect of test direction on mechanical properties of textured Ti-6Al-2Sn-4Zr-6Mo plate Test direction(a)

L T S

Tensile strength

Yield strength

MPa

ksi

MPa

ksi

Elongation, %

Reduction in area, %

1027 1358 938

149 197 136

952 1200 924

138 174 134

11.5 11.3 6.5

18.0 13.5 26.0

KIc

Elastic modulus

KIc specimen

GPa

106 psi

MPa m

ksi in.

orientation(b)

107 134 104

16 19 15

75 91 49

68 83 45

L-T L-T S-T

(a) High basal pole intensities reported in the transverse direction, 90° from normal, and also intensity nodes in positions. L, longitudinal; T, transverse; S, short transverse direction. (b) 45° from the longitudinal (rolling) direction and about 40° from the plate normal

102 / Titanium: A Technical Guide Table 2.2) contain more than this minimum amount of beta stabilizer alloy addition. The more highly beta-stabilized alloys are alloys such as Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) and Ti-15V-3Cr-3Al-3Sn. Solute-lean beta alloys are sometimes classified as beta-rich alpha-beta alloys, and this class includes Ti-10V-2Fe-3Al and proprietary alloys, such as Ti-17 (Ti-5Al2Sn-2Zr-4Mo-4Cr) and Beta CEZ (Ti-5Al2Sn-4Zr-4Mo-2Cr). Structures and Strengthening Concepts. In a strict sense, there is no truly stable beta alloy because even the most highly alloyed beta will, on holding at elevated temperatures, begin to precipitate omega, alpha, Ti3Al, or silicides, depending on temperature, time, and alloy composition. All beta alloys contain a small amount of aluminum, an alpha stabilizer, in order to strengthen alpha that may be present after heat treatment. The composition of the precipitating alpha is not constant and depends on the temperature of heat treatment. The higher the temperature in the alpha-beta phase field, the higher the aluminum content of alpha. The processing window is tighter than that normally used for the other alloy types (alpha and alpha-beta alloys). For the less highly beta-stabilized alloys, such as Ti-10V-2Fe-3Al, the thermomechanical process is critical to the property combinations achieved because this has a strong influence on the final microstructure and the resultant tensile strength and fracture toughness that can be achieved. Exacting control of thermomechanical processing (TMP) is somewhat less important in the more highly beta-stabilized alloys, such as Ti-3Al8V-6Cr-4Mo-4Zr and Ti-15V-3Cr-3Al-3Sn. In these alloys, the final microstructure, precipitated alpha in the beta phase, is so fine that microstructural manipulation through TMP is not as effective. In the case of these alloys, the aging heat treatments, including sequence and temperature, are more critical. The key is to obtain a uniform level of precipitation. This level can be obtained by a low-high aging sequence or, with residual cold or warm work, possibly a high-low aging sequence. When highly alloyed beta alloys, such as Beta C, are cold worked prior to aging, high strength can be obtained with good ductility because cold work induces finer and more uniform precipitation. The TMP must, however, be controlled to provide a uniform microstructure throughout the cross section of the material and, in conjunction with the heat treatment, avoid the occurrence of extensive grain boundary alpha or a precipitate-free zone near the grain boundaries. In the case of solute-lean beta alloys, such as Ti-10V-2Fe-3Al, microstructural objectives range from fully transformed, aged beta structures to controlled amounts of elongated primary alpha in an aged beta matrix, characterized by extremely fine secondary (aged) alpha. The latter microstructure is preferred for most aerospace applications (specifications) and forms the basis for most commercial use of the alloy in forgings.

Relationships among Alloy Properties and Structures Ti-6Al-4V Alpha-Beta Alloy. In the annealed condition, the alpha-beta alloy Ti-6Al4V derives its annealed strength from several sources; the principal source is substitutional and interstitial alloying of elements in solid solution in both alpha and beta phases. Oxygen, nitrogen, hydrogen, and carbon are the interstitial elements, which generally increase strength and decrease ductility. Aluminum is the most important substitutional solid-solution strengthener. Its effect on strength is linear. Other, less important sources of strengthening are interstitial solid solution strengthening, grain size effects, second-phase (beta) effects, ordering in alpha, age hardening, and effects of crystallographic texture. Aluminum in Ti-6Al-4V gives rise to some tendency toward ordering in the alpha phase; the ordered product is Ti3Al, alpha-2. Ordering in the alpha phase contributes perhaps 15 to 35 MPa (2–5 ksi) to the strength of standard Ti-6Al-4V and contributes less than this to the strength of the ELI grade. Ordering also appears to degrade toughness. The effect of crystallographic texture is to introduce directionality into the strength equation. Relative to the hexagonal axis in alpha, strength (and modulus) is high in the parallel direction and low in the normal direction. Because metalworking operations tend to produce preferred crystallographic orientations in alpha grains, strength becomes an anisotropic quantity in most product forms. This feature can be minimized by proper processing and is rarely of direct concern. In some instances, it can be an advantage. At room temperature, Ti-6Al-4V is about 90 vol% alpha, and thus the alpha phase dominates the physical and mechanical properties of the alloy. However, the overall effects of processing history and heat treatment on microstructure are complex. The microstructure depends on both processing history and heat treatment, and the microstructure that combines highest static strength and ductility is not necessarily the microstructure that provides optimum fracture toughness, fatigue strength, or resistance to crack growth. Because the beta phase present in alloy Ti-6Al-4V can be manipulated in amount and composition by heat treatment, the alloy is responsive to heat treatment. The beta to alphaplus-beta reaction at low temperature leads to increased strength. The key is to quench from high in the alpha-plus-beta field and then age at a lower temperature. A typical strengthening heat treatment consists of heating for 1 h at 955 °C (1750 °F) and water quenching, followed by heating for 4 h at 540 °C (1000 °F) and air cooling. Response is limited in a practical sense, however, by two factors: the small amount of beta in Ti-6Al-4V and section size (see the section “Alpha-Beta Alloy Hardenability” above). The first factor puts an intrinsic ceiling on the

increased strengthening response available—approximately 280 MPa (40 ksi) in thin-gage material. The second factor relates to depth of hardening because Ti-6Al-4V is not effectively hardenable in sections greater than 25 mm (1 in.) in thickness. The Ti-6Al-4V alloy is, therefore, most commonly used in the annealed condition. When alloy Ti-6Al-4V is processed improperly after heating into the beta field, alpha phase can form preferentially along the priorbeta grains. Extensive hot work is required to break up such structures. Because cracks tend to propagate in or near interfaces, this type of structure can provide loci for crack initiation and propagation and thereby lead to premature failure. Other Alpha-Beta Alloys. Two alloys that fall in the high-strength alpha-beta class are Ti-6Al-6V-2Sn, which is used in airframes, and Ti-6Al-2Sn-4Zr-6Mo, which is used in jet engines. Both of the latter alloys are stronger and more readily heat treated than Ti-6Al-4V. These features arise from the increased solid solution strengthening afforded by tin and zirconium, which have relatively small effects on the transformation temperature, and from the increased amounts of beta phase that result from the larger vanadium and molybdenum additions. (Both vanadium and molybdenum are beta stabilizers.) The Ti-6Al-6V-2Sn alloy contains the beta stabilizers copper and iron in combined amounts up to 1.4 wt% for enhanced strength and response to aging. Alloy Ti-6Al2Sn-4Zr-6Mo also is useful not only at low temperatures but also at moderately elevated temperatures from 425 to 480 °C (800–900 °F). This alloy combines high tensile strength with good creep resistance. The alpha phase tends to order more readily in these alloys than in alloy Ti-6Al-4V. Moreover, the transformed alpha platelets in Ti-6Al-2Sn-4Zr-6Mo tend to be narrower than those in Ti-6Al-4V, and formation of packets of parallel platelets is less likely. For both Ti-6Al-6V-2Sn and Ti-6Al-2Sn-4Zr-6Mo, martensite does not form in ordinary situations. Alpha is the dominant phase in these alloys, but to a lesser extent than in Ti-6Al-4V. The metallurgy of these alloys is otherwise very similar to that of Ti-6Al-4V. Alpha and Near-Alpha Alloys. Ti-8Al1Mo-1V alloy is in the near-alpha class. The Ti-8Al-1Mo-1V alloy has the highest modulus and the lowest density of any commercial titanium alloy. Ti-6Al-2Sn-4Zr-2Mo-0.08Si is one of the most creep-resistant titanium alloys and has an outstanding combination of tensile strength, creep strength, toughness, and hightemperature stability for long-term applications at temperatures up to 425 °C (800 °F). Alloy Ti-6Al-2Sn-4Zr-2Mo can be modified with silicon additions of up to 0.1%, and, when beta annealed (i.e., annealed by heating above the transformation temperature), the modified alloy for many years provided one of the highest creep strength and temperature capabilities of commercial titanium alloys in the United States. Each of these alloys tends to order in the

Relationships among Structures, Processing, and Properties / 103 alpha phase more readily than does Ti-6Al-4V. Martensite forms more readily in either of these alloys than in Ti-6Al-4V. These alloys, therefore, are usually employed as solution annealed and stabilized. At high temperatures, strain aging arising from aluminum, silicon, and tin, and perhaps from oxygen and zirconium, is thought to contribute to the creep resistance of these materials. The alpha phase dominates the properties of these alloys to a greater extent than it does in Ti-6Al-4V. The metallurgy of the near-alpha alloys is otherwise similar to that of Ti-6Al-4V. Beta Alloys. There is no single beta alloy with the same broad applicability as Ti-6Al4V. Consequently, specific beta alloys are used because their properties suit a particular application. In general, beta alloys are used for workability, corrosion resistance, and the ability to heat treat larger section sizes than the alpha-beta alloys. The beta and beta-rich alpha-beta alloys offer the opportunity to tailor the combinations of strength and toughness properties to a specific application. That is, moderate strength with high toughness or high strength with moderate toughness can be

Table 12.9 interest Composition, wt%

Some beta alloys of current Common name

Principal uses

Ti-3Al-8V-6CrBeta C or 38-6-44 Springs 4Zr-4Mo Ti-10V-2Fe-3Al Ti-10-2-3 Air frames Ti-15V-3Cr-3Sn-3Al Ti-15-3 Strip producible, cold formable, age hardenable, weldable Ti-15Mo-2.7NbBeta 21S Oxidation resistant 3Al-0.2Si and candidate for composite matrix

Table 12.10 Alloy name

Static Properties of Alloys

achieved. This is generally not possible for other types of titanium alloys because they cannot be heat treated over a very wide range. Beta alloys also tend to have higher densities and lower elastic moduli than alpha or alpha-beta alloys. A moderate database has been developed for beta titanium alloys starting with Ti-13V11Cr-3Al and continuing with more recent efforts on Ti-10V-2Fe-3Al, as a forging alloy, and Ti-15V-3Al-3Sn-3Cr, as a sheet alloy. The Ti-10V-2Fe-3Al alloy also has been cast-plusHIP processed and powder HIP processed. Other beta alloys have been evaluated; Ti-13V-11Cr-3Al is one of the few alloys other than Ti-10V-2Fe-3Al with a significant published database. Ti-10V-2Fe-3Al is a deep-hardening, metastable, near-beta alloy that can be thermomechanically processed to a range of strength levels combined with excellent fracture toughness. The preferred forging process to meet the mechanical property criteria is to use controlled beta forging followed by controlled alpha-beta forging. This, in combination with final thermal treatment, provides the optimum combination of strength, ductility, toughness, fatigue, and fracture-related properties. Ti10V-2Fe-3Al can be conventionally alpha-beta forged and thermally treated. With such conventional processes, the alloy achieves high strength and fatigue properties and superior ductility, but poor toughness and fracture-related properties. With respect to the reputed greater hardenability of beta alloys relative to alpha-beta alloys, it has been claimed that forgings of Ti-10V-2Fe-3Al have achieved equivalent strengths at greater section sizes than with alpha-beta Ti-6Al-4V alloy. Some beta alloys of current interest are indicated in Table 12.9.

Tensile and Creep-Rupture Properties. Typical property levels for titanium alloy mill products are listed in Table 12.10. The effects of temperature on strength for the same alloys are shown in Table 12.11. Data for unalloyed titanium are included in Table 12.11 to illustrate that the alloys not only have higher room-temperature strengths but also retain much larger fractions of that strength at elevated temperatures. In terms of the principal heat treatments used for titanium, beta annealing of alpha-beta alloys decreases strength by 35 to 100 MPa (5–15 ksi) depending on prior grain size, average crystallographic texture, and testing direction. Solution treating and aging can be used to enhance strength at the expense of fracture toughness in alloys containing sufficient beta stabilizer (i.e., 4 wt% or more). Typical tensile strengths and 0.1% creep strengths as functions of temperature of some selected alloys are shown in Fig. 12.13 and 12.14, respectively. Fracture Toughness. There are significant differences among titanium alloys in fracture toughness, but there also is appreciable overlap in their properties. Table 12.5 gives examples of typical plane-strain fracture toughness ranges for alpha-beta titanium alloys. From these data, it is apparent that the basic alloy chemistry affects the relationship between strength and toughness. From Table 12.5 it also is evident, as noted earlier, that transformed microstructures can greatly enhance toughness while only slightly reducing strength. It is well known that toughness depends on TMP to provide the desired structure. Fracture toughness behavior of solute-lean beta titanium alloy

Room-temperature tensile properties for selected titanium alloys Nominal composition

5-2.5 3-2.5 6-2-1-1 8-1-1 Corona 5 Ti-17 6-4

Ti-5Al-2.5Sn Ti-3Al-2.5V Ti-6Al-2Nb-1Ta-1Mo Ti-8Al-1Mo-1V Ti-4.5Al-5Mo-1.5Cr Ti-5Al-2Sn-2Zr-4Mo-4Cr Ti-6Al-4V

6-6-2

Ti-6Al-6V-2Sn

6-2-4-2 6-2-4-6

Ti-6Al-2Sn-4Zr-2Mo Ti-6Al-2Sn-4Zr-6Mo

6-22-22 10-2-3

Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.25Si Ti-10V-2Fe-3Al

15-3-3-3

Ti-15V-3Cr-3Sn-3Al

13-11-3

Ti-13V-11Cr-3Al

38-6-44

Ti-3Al-8V-6Cr-4Mo-4Zr

β-III

Ti-4.5Sn-6Zr-11.5Mo

Ultimate strength

Yield strength

Condition

MPa

ksi

MPa

ksi

Elongation, %

Annealed (0.25–4 h/700–870 °C, or 1300–1600 °F) Annealed (1–3 h/650–760 °C, or 1200–1400 °F) Annealed (0.25–2 h/700–930 °C, or 1300–1700 °F) Annealed (8 h/790 °C, or 1450 °F) α-β annealed after β processing α-β or β processed plus aged Annealed (2 h/700–870 °C, or 1300–1600 °F) Aged Annealed (3 h/700–820 °C, or 1300–1500 °F) Aged Annealed (4 h/700–840 °C, or 1300–1550 °F) Annealed (2 h/820–870 °C, or 1500–1600 °F) Aged α-β processed plus aged Annealed (1 h/760 °C, or 1400 °F) Aged Annealed (0.25 h/790 °C, or 1450 °F) Aged Annealed (0.5 h/760–820 °C, or 1400–1500 °F) Aged Annealed (0.5 h/820–930 °C, or 1500–1700 °F) Aged Annealed (0.5 h/700–870 °C,or 1300–1600 °F) Aged

830–900 650 860 1000 970–1100 1140 970 1170 1070 1280 1000 1030 1210 1120 970 1240–1340 790 1140 930–970 1210 830–900 1240 690–760 1240

120–130 95 125 145 140–160 165 140 170 155 185 145 150 175 162 140 180–195 115 165 135–140 175 120–130 180 100–110 180

790–830 620 760 930 930–1030 1070 900 1100 1000 1210 930 970 1140 1010 900 1140–1240 770 1070 860 1140 780–830 1170 650 1170

115–120 90 110 135 135–150 155 130 160 145 175 135 140 165 147 130 165–180 112 155 125 165 113–120 170 95 170

13–18 22 14 12 12–15 8 17 12 14 10 15 11 8 14 9 7 20–25 8 18 7 10–15 7 23 7

104 / Titanium: A Technical Guide (Ti-10V-2Fe-3Al) forgings is shown in Table 12.12 and Fig. 12.15. Fracture toughness can be varied within a nominal alpha-beta titanium alloy by as much as a multiple of two or three. This can be accomplished by manipulating alloy chemistry, microstructure, and texture. Some tradeoff of

Table 12.11

other desired properties may be necessary to achieve high fracture toughness. Plane-strain fracture toughness, KIc, is of special interest because the critical crack size at which unstable growth can occur is proportional to (KIc)2. Strength is often achieved in titanium alloys at the expense of KIc.

Microstructural objectives in beta titanium alloys range from fully transformed, aged beta structures to controlled amounts of elongated primary alpha phase in an aged beta matrix, characterized by extremely fine secondary (aged) alpha. The latter is preferred from a toughness standpoint for most aerospace ap-

Percent of room-temperature strength retained at elevated temperature for several titanium alloys Room-temperature strength retained, %

Temperature

Unalloyed Ti

Ti-6Al-4V

Ti-6Al-6V-2Sn

°C

°F

TS

YS

TS

YS

TS

YS

Ti-6Al-2Sn-4Zr-6Mo TS

YS

Ti-6Al-2Sn-4Zr-2Mo TS

YS

TS

Ti-1100 YS

TS

IMI-834 YS

93 204 316 427 482 538 593

200 400 600 800 900 1000 1100

80 57 45 36 33 30 …

75 45 31 25 22 20 …

90 78 71 66 60 51 …

87 70 62 58 53 44 …

91 81 76 70 … … …

89 74 69 63 … … …

90 80 74 69 66 61 …

89 80 75 71 69 66 …

93 83 77 72 69 66 …

90 76 70 65 62 60 …

93 81 76 75 72 69 66

92 85 79 76 74 69 63

… 85 … … … … 63

… 78 … … … … 61

Short time tensile test with less than 1 h at temperature prior to test. TS, tensile strength; YS, yield strength

190 100

170

Ti-6Al-2Sn–4Zr-6Mo 80 Ti-8Al-1Mo-1V

130

Stress, ksi

Stress, ksi

150

Ti-6Al-6V-2Sn

110

60

Ti-5Al-2.5Sn

Ti-6 Al-2Sn-4Zr-2Mo

40

Ti-6Al-2Sn-4Zr-2Mo 90

Ti-6 Al-2Sn-4Zr-6Mo

Ti-8Al-1Mo-1V

Ti-6Al-6V-2Sn 20

70

Ti-5Al-2.5Sn

Ti-6Al-4V Ti-6Al-4V

50

0

200

400

600

800

0 500

1200

1000

600

Approximate temperature, °F

Fig. 12.13

700

800

900

1000

1100

Approximate temperature, °F

Fig. 12.14

Comparison of typical ultimate tensile strengths of selected titanium alloys as a function of temperature

Comparison of typical 150 h, 0.1% creep strengths for selected titanium alloys

Table 12.12 Typical data on room-temperature tensile and toughness properties for Ti-10V-2Fe-3Al beta titanium alloy Ultimate tensile strength

Tensile yield strength

Plane-strain fracture toughness

MPa

ksi

MPa

ksi

Elongation, %

High-strength condition Isothermal forgings Conventional forgings Pancake forgings Extrusions

1300–1380 1230–1350 1275–1310 1240

188–200 178–196 185–190 179

1200–1255 1145–1280 1150–1160 1170

174–182 166–186 167–168 169

3–6 4–10 5–8 4

29 44–60 47 …

26 40–54 43 …

Reduced-strength condition Isothermal forgings Pancake forgings Extrusions

1060–1100 965 1110–1170

153–159 140 161–169

985–1060 930 1000–1105

143–153 135 145–160

8–12 16 6–7

70 100 45–48

64 91 41–44

AMS specification (forgings) AMS 4984 AMS 4986 AMS 4987

1190 1100 965

173 160 140

1100 1000 895

160 145 130

4 (in 4D)(a) 6 (in 4D)(a) 8 (in 4D(a)

44 60 88

40 55 80

Forgings

(a) D, specimen diam

MPa m

ksi in.

Toughness versus yield strength of a solutelean beta titanium alloy, Ti-5Al-2Sn-4Zr4Mo-2Cr, processed to two different structures

Fig. 12.15

Relationships among Structures, Processing, and Properties / 105 Table 12.13 Room-temperature fracture toughness of Ti-6Al-4V (0.11% O) alpha-beta titanium alloy in welds and heat-affected zones KIc heat-affected zone

Weld Post stress relief

2 h at 590 °C (1100 °F), AC 1 h at 650 °C (1200 °F), AC 1 h at 760 °C (1400 °F), AC

MPa m

ksi in.

MPa m

87(b) 85(d) …

79(b) 77(d) …

81(c) 77(d)(e) 76(d)

ksi in.

74(c) 70(d)(e) 69(d)

Base metal(a) MPa m

ksi in.

92 92 92

84 84 84

AC, air cool. (a) Recrystallization anneal at 0.11 wt % O. (b) Base on data from 2 samples. (c) Based on data from 20 samples. (d) Based on data from 1 sample. (e) Annealed for 2 h at 650 °C (1200 °F)

plications. There would appear to be an optimum amount of primary alpha to achieve a maximum toughness. TMP of Ti-10V-2Fe-3Al achieves its desired final microstructure through this manipulation of alpha-phase morphology. At moderate strength levels—for instance, say 965 MPa (140 ksi) and above—the beta alloys can be processed to achieve higher fracture toughness values than possible for the other types (alpha and alpha-beta alloys). Structure influence on toughness versus strength tradeoffs in solute-lean beta alloys are further illustrated in Fig. 12.15, which gives KIc versus

yield strength for Ti-5Al-2Sn-4Zr-4Mo-2Cr alloy. The figure shows that a necklace structure (more boundaries) is the tougher structure at lower yield strengths. Within the permissible range of chemistry for a specific titanium alloy and grade, oxygen is the most important variable insofar as its effect on toughness is concerned. In essence, if high fracture toughness is required, oxygen must be kept low, other things being equal. Reducing nitrogen, as in Ti-6Al-4V-ELI, is also indicated, but the effect is not as strong as it is with oxygen. Improvements in KIc can be obtained by providing either of two basic types of microstructures:

• Ti-6Al-4V transformed structures, or struc•

tures transformed as much as possible, because such structures provide tortuous crack paths Ti-6Al-4V equiaxed structures composed mainly of regrowth alpha that have both low dislocation-defect densities and low concentrations of nitrogen and oxygen (the so-called “recrystallization-annealed” structures)

Transformed structures appear to be tough primarily because fractures in such structures must proceed along tortuous, many-faceted crack paths. According to some work on alpha-beta alloys, KIc is proportional to the fraction of transformed structure, from the beta, in the alloy. The subject is a complex one without clear-cut empirical rules. Furthermore, the enhancement of fracture toughness at one stage of an operation—for example, a forging billet—does not

Curves depicting stress versus cycles to failure for pure titanium as affected by (a) grain size, (b) oxygen content, and (c) cold work

Fig. 12.16

Curves depicting room-temperature stress versus cycles to failure for grade 2 titanium (0.03 wt% iron) at two temperatures. UTS, ultimate tensile strength

Fig. 12.17

necessarily carry over to a forged part. Because welds in Ti-6Al-4V contain transformed products, one would expect such welds to be relatively high in toughness. This is, in fact, the case, as shown in Table 12.13. In addition to welding, many other factors, such as environment, cooling rates in large sections (i.e., hardenability, a factor that affects structural fineness), and hydrogen content, can affect KIc.

Cyclic Properties of Alloys Fatigue of Unalloyed Titanium. Fatigue is the cyclic degradation of the strength capability of a material. Fatigue damage depends on the alloy chemistry, the alloy structure, surface treatment, and the stress levels and mode of application of stress. Failure cycles in the range of less than approximately 5 × 104 cycles are termed low-cycle fatigue (LCF), while failures at and above approximately 106 cycles are termed high-cycle fatigue (HCF). Fatigue cycles can be induced by mechanical means, thermal means, and combined thermal and mechanical (thermomechanical) means. The latter is designated TMF. Fatigue that is solely thermally induced is known as thermal fatigue. LCF and HCF are the dominant fatigue areas for titanium alloys. Fatigue life in unalloyed titanium depends on grain size, interstitial level, and degree of cold work, as illustrated in Fig. 12.16, where the interstitial element is oxygen. A decrease in grain size in unalloyed titanium from 110 down to 6 μm improves the 107 cycle fatigue endurance limit by 30%. HCF limits of unalloyed titanium depend on interstitial contents just as do the TYS and UTS. The ratio of HCF endurance limit and TYS at ambient temperature appears to remain relatively constant because TYS changes with interstitial content but shows a temperature dependence. Temperature effects on unalloyed titanium are somewhat described by the behavior of grade 2 titanium alloy (with low iron content) at two temperatures over the region about 5 × 104 to 107 cycles for failure, as shown in Fig. 12.17. Fatigue in Titanium Alloys. In addition to the alpha grain size, degree of aging, and oxygen content for near-alpha and alpha-beta alloys, the fatigue properties are strongly affected by the morphology and arrangement of both alpha and beta phases. In fact, although static properties depend on these same features, titanium fatigue (and toughness) can be even more dependent on structure than are the static properties. Important parameters of microstructure affecting fatigue of titanium alloys are the prior-beta grain size or colony size of the alpha and beta lamellae and the width of the alpha lamellae in fully lamellar microstructures. Figure 12.18 gives curves showing stress versus cycles to failure for several different microstructures and variants on the alpha-beta titanium alloy Ti-6Al-4V. Lamellar structures re-

106 / Titanium: A Technical Guide sult from the transformation decomposition of the high-temperature beta phase. The finer the lamellae are in the transformed beta phase, the stronger is the alloy in fatigue (Fig. 12.18a). The finer the prior-beta grain size is, the correspondingly smaller the lamellar colony sizes are that can be realized. Typical crack nucleation sites for the Ti-6Al-4V material tested in Fig. 12.18 are shown in Fig. 12.19. Due to high silicon content (0.45 wt%) in a different alloy, the high-temperature high-strength alloy Ti 1100, fine prior-beta grain sizes and small lamellar colony sizes can be produced. These structures are produced in the alloy on transformation during cooling from the solution treating or beta-anneal temperature. Curves showing stress versus cycles to failure for Ti 1100 are given in Fig. 12.20. Reduction of the prior-beta grain size in a fully lamellar structure (Fig. 12.20a),

as well as decreased primary alpha volume fraction in duplex structures (Fig. 12.20b), improves fatigue life in both the LCF and HCF ranges. Considering specific regimes of an S-N curve, results of an LCF study on the alpha-beta alloy Ti-6Al-4V are shown in Fig. 12.21. As shown, the time to the first crack (at a fixed strain) varies with the microstructure of the alpha-beta alloy. Note that the time to crack initiation is optimized with a structure that has high amounts of transformed beta, yet still has approximately 10% of primary alpha. (It should be noted, however, that the crack propagation resistance of the beta-processed structure still exceeds that of alpha-processed material.) The fatigue lives of titanium alloys are quite interesting in their response to R-value, that is, preload. (R = –1 indicates similar tension and compression stresses.) Also, notch concentrations and surface conditions play a very signifi-

cant role. The beneficial aspects of peening and glass-bead blasting on Ti-6Al-4V LCF at 21 °C (70 °F) are shown in Fig. 12.22. The effects of notch factor, Kt, and crack propagation on life of preloaded Ti-6Al-4V at 204 °C (400 °F) in the LCF range are shown in Fig. 12.23. (Surface processing effects and surface defects on fatigue behavior of titanium alloys are discussed more later.) LCF behavior of titanium alloys is very difficult to quantify due to the wide range of vari-

(a)

Curves depicting stress versus cycles to failure (R = –1) for Ti-1100 near-alpha titanium alloy. (a) Full lamellar microstructures showing range of effects of prior-beta grain sizes. (b) Duplex microstructures showing range of effects of primary alpha content

Fig. 12.20

(b)

Curves depicting room-temperature stress versus cycles to failure for alpha-beta titanium alloy Ti-6Al-4V in a variety of conditions. (a) Fully lamellar structure. (b) Fully equiaxed structure. (c) Duplex microstructure. In (a), width of alpha lamellae is at issue; in (b), effect of alpha grain size is at issue; in (c), width of alpha lamellae is at issue. Note: R = –1; B/T-RD, basal/transverse texture, rolling direction; WQ, water quench; AC, air cooled

Fig. 12.18

(c) Fatigue crack nucleation sites in Ti-6Al-4V alpha-beta alloy. (a) Fully lamellar microstructure. (b) Fully equiaxed microstructure. (c) Duplex microstructure

Fig. 12.19

Low-cycle fatigue life of Ti-6Al-4V alphabeta titanium alloy with different structures: beta forged (100% transformed beta); 10% primary alpha (balance transformed beta); 50% primary alpha

Fig. 12.21

Relationships among Structures, Processing, and Properties / 107 The effect of temperature is rarely reported; the stress capability of Ti-6Al-4V at R = 0 (cyclic = steady, preloaded stress) was about 11% less at 204 °C (400 °F) than it was at 21 °C (70 °F). In HCF, depending on the alloy, the fatigue endurance limit tends to be relatively flat with temperatures out to 316 °C (600 °F), or above, as shown in Fig. 12.24. This figure also illustrates the benefits of titanium alloys over steels in fatigue strength capability. This figure indicates, in a broad way, the range of data scatter that can be found in a given titanium alloy at a single Kt and temperature. The figure clearly indicates again that surface condition affects HCF. The preceding discussion has centered largely on near-alpha and alpha-beta titanium alloys. Fatigue of beta alloys also is influenced by microstructure. Dependent on alloy class

Cyclic = steady stress, ksi

ables and to the limited amount of published data. In general, available data are for loadcontrolled, not strain-controlled, tests. Much testing in producer laboratories was done on mill products, such as barstock. Specimens machined from forgings tended to be used in customer laboratories. Results from barstock differ from those on forgings. This can be a very serious issue because titanium is a relatively expensive material and the destruction of full-scale forgings, such as those used in the aerospace industry, is not to be taken lightly. Structures produced in actual forgings differ from those in barstock. Surface residual stress and structure can differ in forgings or finished components from those in barstock. Property results for titanium fatigue should fully take into consideration the surface condition, as well as microstructure, when design properties are being developed. Although barstock and forged component results do not necessarily agree, it has been found that component full-scale test results on forgings generally agree with test results on specimens machined from forgings, provided surface treatments (e.g., machining and peening) are the same.

First crack

60

40 Failure First crack

20

103

Fig. 12.22

Effects of surface condition on low-cycle fatigue life of Ti-6Al-4V at 21 °C (70 °F)

Kt = 1 Kt = 2 104 Cycles

(solute-rich or solute-lean alloy), the following microstructural parameters are important in determining fatigue life of beta alloys: beta grain size, degree of age hardening, and precipitate-free regions in the solute-rich alloys. Further, grain boundary alpha, primary alpha size, and primary alpha volume fraction are important in solute-lean alloys, such as Ti-10V2Fe-3Al. Ti-10V-2Fe-3Al represents the class of solute-lean beta alloys that can have microstructure manipulated to a greater degree than other beta alloys by the possible presence of primary alpha in volume fractions similar to those in alpha-beta alloys. The curves showing stress versus cycles to failure for various microstructures in Ti-10V-2Fe-3Al are shown in Fig. 12.25. The superior performance of the microstructures with the lower primary alpha contents was related to the concurrent absence of grain boundary alpha. Fatigue properties for Ti-10V-2Fe-3Al also are compared to the solution-treated and annealed alpha-beta alloy Ti-6Al-4V in Fig. 12.26. The discussion and data presented above are indicative of trends in alloy performance. However, especially due to the variety of microstructures and the potential sensitivity to surface condition in fatigue, applications of titanium alloys to fatigue-limited components should include verification of the fatigue strength under expected service conditions. Surface Treatment and Fatigue. It should be apparent from the preceding fatigue discussion that titanium alloy fatigue capability can be significantly affected not just by micro-

105

Low-cycle fatigue properties of alpha-beta titanium alloy Ti-6Al-4V showing effects of notch acuity and time to first crack

Fig. 12.23

Curves depicting stress versus cycles to failure for various microstructures in Ti-10V-2Fe-3Al beta alloy for various levels of primary alpha. R = –1.

3

σ max, 10 psi (9 MPa)

Fig. 12.25

70 (483) 60 (414)

50 (345) 40 (276) 30 STA Ti-6A1-4V plate (207) 104 105 Cycles to failure

Fig. 12.24

steels once used in the compressor sections of gas turbines

106

Comparison of notched fatigue curves for beta alloy Ti-10V-2Fe-3Al and alphabeta alloy Ti-6Al-4V. For Ti-10V-2Fe-3Al, R = 0.05, F = Kt = 2.9. For STA Ti-6Al-4V plate, R = 0.1; Kt = 3.

Fig. 12.26

High-cycle (5 × 107 cycles) fatigue strength to density of several titanium alloys compared with some

Ti-10V-2Fe-3Al forgings

108 / Titanium: A Technical Guide structure, but also by surface condition or treatment. Fatigue data reported in the literature often can be on material with favorable surface residual stress induced by processes such as turning and milling. Fully stress-relieved or chemical-milled surfaces generally have fatigue strengths below the reported alloy capabilities because most reported values have been biased upward by the favorable—that is, compressive—surface stresses. Mechanical surface treatments, such as shot peening, polishing, or surface rolling, can be used to improve the endurance limit in titanium-base materials by altering surface roughness, degree of cold work (dislocation density), and residual stresses. The surface roughness determines whether fatigue strength is primarily controlled by crack nucleation (smooth) or by crack propagation (rough). For smooth surfaces, a work-hardened surface layer can delay crack nucleation due to the increase in strength. On rough surfaces, the crack initiation phase can be absent and a work-hardened surface layer will be more prone to crack propagation due to reduced ductility. Near-surface residual compressive stresses are clearly beneficial because they can significantly retard crack growth once cracks are present (although subsequent stress relief or cyclic plastic deformation can reduce beneficial compressive residual stresses). Great care must be taken in the preparation of titanium surfaces so as not to introduce any defects in the form of excessive scratches or arc burns, for example, which might cause nucleation of fatigue cracks and reduction in fatigue capability of a given alloy. Ordinary machining seems to be beneficial to fatigue strength, as does surface modification by peening to induce favorable residual stresses. Another method of surface treatment is to modify surface microstructure by thermomechanical processing (TMP). TMP treatments are widely used to optimize the bulk mechanical properties of high-strength titanium alloys.

It can make sense to “tailor” microstructural variations from the surface to the interior to meet differing requirements (e.g., in the carburizing of steels). Cold working induced by mechanical surface treatments can be used to develop a surface microstructure that is different from that in the bulk. This processing enables use of the features of TMP even in cases where conventional TMP may not be practical, as in thick sections. A distinct advantage to be gained by altering the surface microstructure is that such alterations are more stable than those induced by mechanical surface treatments alone. In the case of alpha alloys, a mechanical surface treatment in combination with subsequent recrystallization offers the possibility to combine the high strengths and endurance limits associated with fine grains with the superior long through-crack fatigue crack growth behavior and fracture toughness of coarse grains. To maximize the total fatigue life in thicker sections, fine grains are needed on the surface where good resistance to crack initiation is critical. Coarse grains are needed in the interior where they can reduce the driving force for long crack growth. To accomplish the above, shot peening followed by a heat treatment for 1 h at 820 °C (1510 °F) was performed on coarse-grained Ti-8Al to cold work and recrystallize the surface. Figure 12.27 indicates a significant improvement in fatigue limit roughly 50 MPa (7.25 ksi) at 350 °C (665 °F) due to the 20 μm fine grain size produced at the surface. Because alpha-beta and near-alpha alloys are often intended for high-temperature service (for example in gas turbines), creep resistance is an important consideration. On this basis, lamellar microstructures would be preferable. However, these microstructures have poor fatigue resistance, particularly in the LCF regime, where surface crack growth determines fatigue life. In such cases, a variation in phase morphology between the surface and the

Curves depicting stress versus cycles to failure for coarse-grained Ti-8Al alpha alloy with and without thermomechanical processing to produce local grain refinement at the surface

Fig. 12.27

core can be desirable. For an alpha-beta and a near-alpha alloy, fine surface microstructures were obtained by mechanically working the surface by shot peening and then heat treating. The improvement in S-N behavior (at high temperature) gained by this thermomechanical surface treatment is shown in Fig. 12.28 for Ti-6Al-2Sn-4Zr-2Mo with a creep-resistant, fine lamellar core and a fatigue-resistant, fine equiaxed surface layer. In the case of beta alloys, both shot peening and surface rolling in combination with specially developed aging treatments have been applied to Ti-3Al-8V-6Cr-4Mo-4Zr alloy to selectively age harden only the surface. Fatigue Crack Propagation. Just as KIc is important in calculating loads that a structural member can carry in the presence of a flaw, it is also important in many cases to know what the remaining fatigue life is in the presence of a fatigue crack or other sharp crack. In a very general way, fatigue crack propagation (FCP) behavior in titanium parallels fracture toughness; that is, for a given alloy, those conditions giving highest toughness tend also to give, under fatigue loading, lowest cyclic growth rates. In FCP measurements, there can be a significant amount of scatter in the data. The example shown in Fig. 12.29 is one of the more extreme cases encountered and arises for the mill-annealed condition where uncertainties of microstructure, texture, and strength can exist. Part of the scatter is due to test reproducibility. There also can be a point-to-point material variability due to minor processing and material inhomogeneities. Variations in chemistry, microstructure, and texture effects within a given lot can, in some cases, be additive even under controlled conditions. There are, of course, differences from lot to lot. For design purposes, users are well advised to use statistical data derived from information from several lots. Titanium alloys have different FCP characteristics just as they have different KIc charac-

Curves depicting stress versus cycles to failure for Ti-6Al-2Sn-4Zr-2Mo alloy with and without thermomechanical processing to produce local grain refinement at the surface

Fig. 12.28

Relationships among Structures, Processing, and Properties / 109 In general, only the more severe environments (such as a 3.5% NaCl solution) affect FCP rates by an order of magnitude or more. Gaseous atmospheres also can play a role in affecting FCP rates. All chemical or gaseous environmental effects undoubtedly are sensitive to some degree both microscopically and chemically. With the increased application of damage-tolerant design criteria, fatigue crack growth rate data for weldments are of increased

MA Ti-6Al-4V

105 (0.25)

Ti-10V-2Fe-3Al

RA Ti-6Al-4V

106 (0.025)

10 (11)

20 30 40 (22) (33) (44) ΔK, ksi

in. (MPa m)

of fatigue crack growth rates Fig. 12.30 Comparison for beta alloy Ti-10V-2Fe-3Al and alpha alloy Ti-6Al-4V. For Ti-10V-2Fe-3Al, R = 0.05; F = 1–30 Hz. For MA Ti-6Al-4V, R = 0.08; F = 1–25 Hz. For RA Ti-6Al-4V, R = 0.08; F = 6 Hz. MA, mill annealed; RA, recrystallization annealed

Fatigue crack propagation data for millannealed alpha-beta alloy Ti-6Al-4V showing data scatter. Data are for six heats of mill-annealed Ti-6Al-4V. T-L, transverse-longitudinal

Fig. 12.29

importance. A comparison of fatigue crack propagation rates between gas-tungsten arc, laser beam, and electron beam welds in alpha-beta Ti-6Al-4V and beta alloy Ti-15V3Al-3Cr-3Sn indicated that average fatigue crack growth rates through the postweld

104 (2.5)

da/dN, in./cycle (μm/cycle)

teristics. Selected data indicate that fatigue cracks propagate more rapidly in Ti-6Al2Sn-4Zr-6Mo than in Ti-8Al-1Mo-1V or Ti-6Al-2Sn-4Zr-2Mo under the same test conditions. This may be a simple effect of strength. However, the relative amounts of beta phase can lead to intrinsically different fatigue crack propagation characteristics. The Ti-6Al-2Sn4Zr-6Mo alloy is also more easily textured. In addition, different phases, such as orthorhombic alpha-double-prime martensite, can exist and could effect FCP problems after aging. FCP rates are shown comparing an alphabeta and a beta alloy in Fig. 12.30. Microstructure variations also produce general parallels between KIc and FCP. As is the case for KIc, FCP is favorably influenced by transformation microstructure and also by application of thermal cycles of the recrystallization-anneal type. Microstructure in a given lot of Ti-6Al-4V can affect FCP by a factor of more than ten and can affect ΔK by 5 to 30 MPa m (4–27 ksi in) depending on where these parameters are measured on the da/dN curve. Generally speaking, beta-annealed microstructures in near-alpha and alpha-beta alloys have the lowest fatigue crack growth rates, whereas mill-annealed microstructures yield the highest growth rates. A typical example of such behavior for an alpha-beta alloy is shown in Fig. 12.31. It should come as no surprise that environment affects FCP rates in titanium just as it affects fracture toughness. The only surprise in the available data is that the chemical environment does not have a larger effect than it does.

Effect of heat treatment on fatigue crack growth rate in Ti-6Al-4V alloy. L-T, longitudinal-transverse

Fig. 12.31

Effect of welding processes on fatigue crack growth rate of longitudinally oriented titanium alloys. (a) Ti-6Al-4V alpha-beta alloy. (b) Ti-15V-3Cr-3Al-3Sn beta alloy. GTAW, gas-tungsten arc welding; EBW, electron beam welding; LBW, laser beam welding

Fig. 12.32

110 / Titanium: A Technical Guide heat-treated weld zones did not differ appreciably with the welding process (Fig. 12.32). The scatter bands were narrower for the high-energy density versus the arc welding processes. For Ti-6Al-4V alpha-beta alloy, it was found

Cast Titanium Alloy Properties

that the average crack growth rates were lower than those in the base metal, while in Ti-15V3Al-3Cr-3Sn beta alloy there were nearly equivalent base metal and weld metal crack growth rates (Fig. 12.32).

Static Properties. Cast titanium alloys are generally alpha-beta alloys. They are equal, or nearly equal, in strength to wrought alloys of the same compositions. Typical room-temperature tensile properties of several cast titanium alloys are shown in Table 12.14. Although a number of titanium alloys have been studied in cast form (Table 12.15), virtually all existing data have been generated from alloy Ti-6Al-4V. Consequently, the basis for most cast alloy property data is Ti-6Al-4V. A distribution of room-temperature tensile properties for separately cast test bars of Ti-6Al-4V alloy is shown in Fig. 12.33. Note that oxygen, a carefully controlled alloy addition that can increase tensile strengths, is in the 0.16 to 0.20 wt% range. This is a common range for many aerospace specifications. Some specifications allow a 0.25 wt% maximum oxygen level. The resultant tensile prop-

Table 12.14 Typical room-temperature tensile properties of several cast titanium alloys (bars machined from castings) Yield strength Alloy (a)(b)

Commercially pure (grade 2) Ti-6Al-4V, annealed Ti-6Al-4V-ELI Ti-1100, Beta-STA(c) Ti-6Al-2Sn-4Zr-2Mo, annealed IMI-834, Beta-STA(c) Ti-6Al-2Sn-4Zr-6Mo, Beta-STA(c) Ti-3Al-8V-6Cr-4Zr-4Mo, Beta-STA(c) Ti-15V-3Al-3Cr-3Sn, Beta-STA(c)

Ultimate strength

MPa

ksi

MPa

ksi

Elongation, %

Reduction of area, %

448 855 758 848 910 952 1269 1241 1200

65 124 110 123 132 138 184 180 174

552 930 827 938 1006 1069 1345 1330 1275

80 135 120 136 146 155 195 193 185

18 12 13 11 10 5 1 7 6

32 20 22 20 21 8 1 12 12

Specification minimums are less than these typical properties. (a) Solution-treated and aged (STA) heat treatments can be varied to produce alternate properties. (b) ELI, extra low interstitial. (c) Beta-STA, solution treatment with beta-phase field followed by aging

Table 12.15

Cast titanium alloys with estimates of relative casting usage Estimated relative use of castings

Alloy

Ti-6Al-4V Ti-6Al-4V-ELI(b) Commercially pure titanium (grade 2) Ti-6Al-2Sn-4Zr-2Mo Ti-6Al-2Sn-4Zr-6Mo Ti-5Al-2.5Sn Ti-3Al-8V-6Cr-4Zr-4Mo (Beta-C) Ti-15V-3Al-3Cr-3Sn (Ti-15-3) Ti-1100 IMI-834 Total

85% 1% 6% 7% <1% <1% <1% <1% <1% <1% 100%

Nominal composition, wt% O

N

C

H

0.18 0.11 0.25 0.10 0.10 0.16 0.10 0.12 0.07 0.10

0.015 0.010 0.015 0.010 0.010 0.015 0.015 0.015 0.015 0.015

0.04 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.04 0.06

0.006 0.006 0.006 0.006 0.006 0.006 0.006 0.006 0.006 0.006

Al

6 6 ... 6 6 5 3.5 3 6.0 5.8

Fe

V

Cr

Sn

Mo

Nb

Zr

Si

0.13 0.10 0.15 0.15 0.15 0.2 0.2 0.2 0.02 0.02

4 4 ... ... ... ... 8.5 15 ... ...

... ... ... ... ... ... 6 3 ... ...

... ... ...

... ... ... 2 6 ... 4 ... 0.4 0.5

... ... ... ... ... ... ... ... ... 0.7

... ... ... 4 4 ... 4 ... 4.0 3.5

... ... ... ... ... ... ... ... 0.45 0.35

2 2 2.5 ... 3 2.75 4.0

(a) Superior, relative to Ti-6Al-4V. (b) RT, room temperature. (c) ELI, extra low interstitial

Fig. 12.33

Typical distribution of room-temperature tensile properties for cast plus hot isostatically pressed Ti-6Al-4V alloy

Special properties(a)(b)

General purpose Cryogenic toughness Corrosion resistance Elevated-temperature creep strength Elevated-temperature tensile strength Cryogenic toughness RT strength RT strength Elevated-temperature properties Elevated-temperature properties

Relationships among Structures, Processing, and Properties / 111

Fig. 12.34

Typical elevated-temperature tensile properties of cast Ti-6Al-4V alloy

erties with oxygen in the 0.20 to 0.25 wt% range are typically about 69 to 83 MPa (10–12 ksi) higher than those shown in Fig. 12.33.

Comparison of short-time tensile properties for wrought and cast forms of Ti-6Al-2Sn4Zr-2Mo. Test bars were cut from castings that were duplex annealed: 1 h at 900 °C (1650 °F) and air cool, plus 1 h at 790 °C (1450 °F) and air cool. Published data on forgings are for material annealed and aged: 1 h at 900 °C and air cool, plus 8 h at 595 °C (1100 °F) and air cool. Published data for 57 mm diam (2 14 in. diam) bar stock are for material annealed and aged: 1 h at 955 °C (1750 °F) and air cool, plus 8 h at 595 °C (1100 °F) and air cool.

However, as would be expected of the higher interstitial level, the ductility is slightly reduced. Because the microstructure of cast titanium alloy parts is comparable to that of wrought (ingot metallurgy) material, many properties of cast-plus-HIP parts are at similar levels to those for wrought alloys. These properties include tensile strength, creep strength, fracture toughness, and FCP. Room-temperature tensile properties and fracture toughness of Ti-6Al-4V castings that have been postcast processed in a variety of ways (see Table 6.1) are compared in Table 6.3 with typical wrought beta-annealed material. It should be noted that the test results shown in Table 6.3 were on small separately cast test coupons and do not necessarily reflect the property level achievable with similar processing on a full-scale cast part. Property levels of actual cast parts, especially larger components, probably will be somewhat lower, the result of coarser grain structure or slower quench rates achieved.

Elevated-temperature tensile properties for Ti-6Al-4V are shown in Fig. 12.34. Tensile properties for cast and wrought alloy Ti-6Al2Sn-4Zr-2Mo are indicated in Fig. 12.35. Figure 12.36 compares the band of tensile properties achievable with cast high-temperature alloys, such as IMI 834, to those of Ti-6Al-4V alloy. Recently, Ti-6Al-2Sn-2Zr-2Mo-2Cr+Si alpha-beta alloy has been evaluated in cast form. Table 12.16 gives properties of the alloy for several heat treating conditions. Comparison with Table 12.14 indicates that cast Ti-6Al-2Sn-2Zr-2Mo-2Cr+Si can provide superior tensile strengths to cast Ti-6Al-4V and does so with a good balance of toughness. The plane-strain fracture toughness values for Ti-6Al-4V castings are compared with values for Ti-6Al-4V plate and with other wrought titanium alloys in Fig. 12.37. Creep-rupture properties of cast alloys are very sparse. Table 12.17 shows creep strength for cast-plus-HIP Ti-6Al-4V generated on specimens cut from cast centrifugal compressor impellers. Impellers were hot isostatically

Fig. 12.35

Fig. 12.36

Scatter band for yield strength versus temperature of several cast titanium high-temperature alloys (Ti-6Al-2Sn-4Zr-2Mo, IMI 834, and Ti 1100) compared with cast Ti-6Al-4V

112 / Titanium: A Technical Guide Table 12.16

Cast-plus-HIP Ti-6Al-2Sn-2Zr-2Mo-2Cr+Si room-temperature tensile properties for several heat treatment conditions

Heat treatment

Thickness, mm (in.)

Ultimate strength, MPa (ksi)

Yield strength, MPa (ksi)

Elongation, %

Reduction in area, %

Fracture toughness, MPa m (ksi in. )

Average fracture toughness, MPa m (ksi in. )

Triplex 1 h at 1000 °C (1840 °F), GFC 1 h at 950 °C (1740 °F), GFC 8 h at 540 °C (1000 °F), SC 1 h at 1000 °C (1840 °F), GFC 1 h at 950 °C (1740 °F), SC 8 h at 540 °C (1000 °F), SC

12.5 (0.5) 25.0 (1.0) 37.5 (1.5) 12.5 (0.5) 25.0 (1.0) 37.5 (1.5)

1049 (152) 1063 (154) 1028 (149) 1028 (149) 1014 (147) 994 (144)

918 (133) 931 (135) 911 (132) 890 (129) 883 (128) 876 (127)

7.3 8.8 7.5 10.7 11.2 10.9

14.1 11.3 11.7 13.6 14.1 13.9

132.3–122.1 (120.3–111.0) 114.1–113.6 (103.8–103.3) 111.2–110.5 (101.1–100.5) 139.0–136.7 (126.4–124.3) 117.9–113.6 (107.2–103.3) 114.8–113.9 (104.4–103.6)

127.1 (115.6) 113.9 (103.6) 110.8 (100.8) 37.9 (125.4) 115.7 (105.2) 114.4 (104.0)

12.5 (0.5) 25.0 (1.0) 37.5 (1.5) 12.5 (0.5) 25.0 (1.0) 37.5 (1.5)

1035 (150) 1035 (150) 1007 (146) 1000 (145) 994 (144) 980 (142)

918 (133) 918 (133) 911 (132) 876 (127) 890 (129) 883 (128)

9.6 8.3 6.8 11.9 8.9 6.7

15.1 10.9 12.2 17.2 13.8 11.0

117.0–114.0 (106.4–103.7) 103.5–111.5 (94.1–101.4) 110.1–115.3 (100.1–104.9) 134.8–121.0 (122.6–110.0) 107.9–111.8 (98.1–101.7) 111.2–112.6 (101.1–102.4)

115.5 (105.0) 107.5 (97.8) 112.7 (102.5) 127.9 (116.3) 109.8 (99.9) 11.9 (101.8)

Duplex 1 h at 950 °C (1740 °F), GFC 8 h at 540 °C (1000 °F),SC 1 h at 950 °C (1740 °F), SC 8 h at 540 °C (1000 °F), SC GFC, gas fan cooled; SC, static cooled

pressed at 900 °C (1650 °F) for 2 h under a pressure of 103.5 MPa (15.0 ksi), then aged 1.5 h at 675 °C (1250 °F). The properties shown may not be optimal for all casting configurations and postcast heat treatments. Cyclic Properties. Although properties of Ti-6Al-4V alloy castings generally meet the properties of beta-annealed, forged wrought (ingot metallurgy) products, forged material has superior HCF properties. As-cast helicopter rotors showed an endurance capability of about 63% of that for forged rotors. Forged products typically are processed in the alpha-beta phase field, yielding a refined alpha-plus-beta microstructure with good fatigue resistance. By contrast, castings cool slowly from the beta phase field, producing a coarse microstructure; this is aggravated by additional coarsening during HIP. Generally, an improvement in fatigue resistance is gained by HIP of cast material, primarily by closing or reduction of pores that can initiate fatigue failure. In addition, results of research suggest that substantial improvement in resistance to FCP can be obtained by beta

heat treating and overaging of cast alloys. Actual crack growth rates will be influenced by casting quality and postcasting heat treatment, including HIP. Baseline microstructure of cast plus HIP parts consists of colonies of alpha plates and grain boundary alpha phase. Baseline data generally are for HIP at 900 °C (1650 °F) 2 h under a pressure of 103.5 MPa (15.0 ksi). Both of the microstructural features noted above reduce resistance to fatigue crack initiation. Heat treating after HIP (Table 6.1) is intended to break up this structure. Heat treatments include beta solution treatment with various rates of cooling from the solution temperature. This is followed by annealing or aging in the alpha-beta region, although temperatures of final heat treatment can vary from 540 to 845 °C (1000–1550 °F). Fatigue strength (and tensile strength) is improved significantly above the cast-plus-HIP levels by all heat treatments (see Table 6.3 for tensile properties). However, this is at the expense of tensile ductility.

Table 12.17

Creep strength of cast alpha-beta titanium alloy Ti-6Al-4V

Test temperature

Fracture toughness of cast and plate of Ti-6Al-4V alloy, with range of values for wrought titanium alloys shown

Fig. 12.37

Water quenching and gas fan cooling from a beta solution temperature of 1025 °C (1880 °F) produce the best combination of strength and ductility with tensile strengths of 1035 MPa (150 ksi) or better and ductilities of 7% or better. Fine martensite produced by a beta quench is transformed into a fine “basketweave” lenticular alpha structure called “broken-up structure” (BUS). This can be contrasted with an alpha colony arrangement in a cast-plus-HIP product. Although grain boundary alpha still exists, it is not continuous like that in the cast-plus-HIP condition. While grain boundary alpha may continue to be a potential source for fatigue crack initiation, fatigue life is improved (Fig. 12.38) due to the absence of continuous alpha-beta interfaces. The general fatigue capability of cast-plusHIP Ti-6Al-4V alloy is shown in Fig. 6.8 to 6.10 and in Fig. 12.39 and 12.40. Although smooth (and notched) HCF data (Fig. 12.39) for castings are lower than smooth data for wrought products, HCF data for smooth and

Stress

Time to reach creep values listed, h

°C

°F

MPa

ksi

Plastic strain on loading, %

Test duration, h

0.1%

0.2%

1.0%

455 425 425 400 370 315 260 205 205 175 150 150 120

850 800 800 750 700 600 500 400 400 350 300 300 250

276 276 345 448 414 517 534 552 531 517 517 517 517

40.0 40.0 60.0 65.0 60.0 75.0 77.5 80.0 77.0 75.0 75.0 75.0 75.0

0 0 0 0.7 0.3 2.04 2.1 0.56 0.8 0.01 … … 0.0

611.2 500.0 297.5 251.4 500 330.9 307.9 138.0 18.2 1006.0 500 500 1006.1

2.0 15.0 3.5 7.5 240.0 0.02 0.01 0.1 0.02 0.4 0.25 1.7 9.8

9.6 60.0 11.0 22.0 … 0.04 0.02 0.13 0.04 2.2 1.2 12.2 160.0

610.0 … 291.5 … … 0.1 0.1 1.5 0.16 … … … …

Specimens were from hubs of centrifugal compressor impellers that were cast, hot isostatically pressed (2 h at 900 °C, or 1650 °F, and 103.5 MPa, 15.0 ksi), and aged 1.5 h at 675 °C (1250 °F). Specimen blanks approximately 5.72 × 0.95 × 0.96 cm (2.25 × 0.37 × 0.37 in.) in section size, with the long axis oriented tangential to the hub section, were machined to standard-type creep specimens 3.81 mm (0.150 in.) in diameter. The specimens were lathe turned and then polished with 320-grit emery paper. The creep rupture tests were performed at 120–455 °C (250–850 °F) using dead-load-type creep frames in air over a stress range of 276–552 MPa (40–80 ksi). The microstructure consisted of transformed β grains with discontinuous grain boundary α and colonies of transformed β that contained packets of parallel-oriented α platelets separated by a thin layer of aged β.

Relationships among Structures, Processing, and Properties / 113

Curves depicting room-temperature stress versus cycles to failure for Ti-6Al-4V cast plus hot isostatically pressed (HIP) alloy showing the effect of postcast heat treatment that produced a broken-up structure. WQ, water quench; AC, air cool

Fig. 12.38

Fig. 12.39

Room-temperature smooth fatigue data of smooth and notched casting specimens

Fig. 12.40

Smooth fatigue data of castings compared to wrought annealed Ti-6Al-4V specimens

114 / Titanium: A Technical Guide notched castings are comparable to those for notched wrought products (Fig. 12.40). With current casting techniques, followed by HIP and a post-HIP heat treatment, static strength properties of cast-plus-HIP material generally are comparable to those in wrought material, and smooth fatigue endurance limit properties come closer to those for wrought products. Of continuing concern, however, is the ability to verify for all properties of castplus-HIP titanium that test bar properties are representative of component values. (At times

Fig. 12.41

this is a problem with wrought ingot metallurgy material, too.)

Powder Metallurgy Titanium Alloy Properties Static Properties. Property data exist for P/M titanium alloys but are still limited despite extensive work on powder processing techniques. Selection of the powder source—blended elemental (BE) or prealloyed (PA) powder—and the pro-

Fracture toughness versus density for pressed and sintered compacts from blended elemental powders of Ti-6Al-4V alloy. Note that the toughness values are not valid KIc and thus are labeled as KQ.

cessing technique(s)—for example, cold isostatic pressing (CIP) + sinter or CIP + sinter + HIP—and postconsolidation-process heat treatment all greatly influence mechanical property capability. Mechanical properties of P/M structural materials depend on the composition, density, and heat treatability of the material, as well as on processing and design considerations. Final density has the greatest effect on properties of P/M materials. P/M parts with theoretical densities of less than 75% are considered to be low density, those above 90% are high density, and those in between are classified as medium density. (Theoretical density is the ratio of the density of a P/M material to that of its wrought counterpart.) Generally, structural parts have densities ranging from 80% to above 95%. However, fatiguecritical, and aircraft-quality parts aim for 100% density. The role of density is evident in Fig. 12.41, which shows that toughness increases dramatically as density increases from about 95% to 99.5% in Ti-6Al-4V compacts made from BE powders. Tensile and fracture toughness properties of Ti-6Al-4V compacts made from BE powders are given in Table 12.18. One of the more important considerations in the manufacture of a titanium P/M product is control of oxygen content, because oxygen has the same effects on properties of P/M parts as it has on those of cast and wrought products. Powders, with their high surface-to-volume ratio, must be handled very carefully, as they have a very great affinity for oxygen. Table 12.19 gives room-temperature tensile properties of compacts made from Ti-6Al-4V powders of varying oxygen

Table 12.18 Room-temperature tensile and fracture toughness properties of Ti-6Al-4V compacts made from blended elemental powders and processed under various conditions 0.2% yield strength Condition(a)

Pressed and sintered (96% dense) Pressed and sintered (98% dense) Pressed and sintered (MR-9 process)(99.2% dense) Pressed and sintered plus HIP CIP and sintered plus HIP Pressed and sintered plus α/β forged Pressed and sintered plus α/β forged Pressed and sintered (92% dense) Plus α/β 30% isothermally forged Plus α/β 70% isothermally forged CIP and sintered plus HIP (low chlorine) CIP and sintered plus HIP (ELCl) Plus BUS treated Plus TCP treated Rolled plate, CIP and sintered plus HIP Mill annealed (L or TL) Mill annealed (T or LT) Recrystallization annealed (L or TL) Recrystallization annealed (T or LT) β annealed (L or TL) β annealed (T or LT) Minimum properties (MIL-T-9047)

Ultimate tensile strength

KIc or (KQ)

MPa

ksi

MPa

ksi

Elongation, %

Reduction in area, %

MPa

ksi

Density, %

758 827 847 806 827 841 951 827 841 896 827 882 951 1007

110 120 123 117 120 122 138 120 122 130 120 128 138 146

827 896 930 875 916 923 1027 910 930 999 923 985 1034 1062

120 130 135 127 133 134 149 132 135 145 134 143 150 154

6 12 14 9 13 8 9 10 30 30 16 11 7 14

10 20 29 17 26 9 24 ... ... ... 34 36 15 20

... ... 38 41 ... ... 49 ... ... ... ... ... ... ...

... ... 35 37 ... ... 45 ... ... ... ... ... ... ...

96 98 99.2 ≥99 99.4 ≥99 99 92 99.7 99.8 99.8 100 ... ...

903 923 888 868 841 875 827

131 134 129 126 122 127 120

958 965 916 937 937 958 896

139 140 133 136 136 139 130

10 14 4 5 10 7 10

26 31 8 9 26 20 25

(72)(b) (71)(b) (75)(b) (67)(b) (89)(b) (92)(b) ...

(65)(b) (64)(b) (68)(b) (61)(b) (81)(b) (84)(b) ...

≥99 ≥99 ≥99 ≥99 ≥99 ≥99 ...

O2,

Chlorine, ppm

ppm

1200 1200 1200 1500 1500 1500 1200 1500 1500 1500 160 <10 ... ...

… ... ... 2400 2400 ... ... 2100 2100 2100 ... ... ... ...

200 200 200 200 200 200 ...

1600 1600 1600 1600 1600 1600 ...

(a) HIP, hot isostatic pressing; CIP, cold isostatic pressing; ELCl, extra-low chlorine powder; BUS, broken-up structure; TCP, thermochemical processing; L, longitudinal; TL, transverse longitudinal; T, transverse; LT, longitudinal transverse (TL and LT per ASTM E 399). (b) Precracked Charpy, Kv.

Relationships among Structures, Processing, and Properties / 115 content. The results presented illustrate the importance of low oxygen content in obtaining satisfactory ductility in hot-pressed powder compacts. Tensile tests, conducted on HIP Ti-6Al-4V compacted from samples of rotating electrode-processed powder, indicated excellent properties, as shown in Table 12.20. Table 12.21 provides additional data on PA powder compact tensile and toughness properties. PA powder or low-chloride PA or BE powder appear to be the optimum starting materials for highest-quality titanium parts, but cost factors promote use of lesser-quality powder. HIP produces the best consolidation for higheststrength parts, but other techniques are available. When no special treatment is applied to reduce chloride content, HIP PA powders with post-HIP heat treatment have the better properties among P/M products. Cyclic Properties. BE or PA powders treated to reduce chlorine show properties at the high end of the scatter band for fatigue behavior of P/M and ingot metallurgy products (see Fig. 12.42). Subsequent improvements in powder manufacturing processes, which include plasma torch melting, have provided plasma rotating electrode-processed Ti-6Al-4V P/M compacts, which also are reported to have fatigue properties that are comparable, or superior, to those for cast and wrought materials. For a given alloy composition, densification and structural control are the prime factors influencing cyclic properties. Fatigue-fracture life of powder compacts can be comparable to wrought product, and FCP characteristics can

be comparable to those for wrought materials having the same chemistry and structure (Fig. 12.43). Density is a major factor in fatigue, as

noted previously. The effect of density on room-temperature fatigue strength of Ti-6Al4V powder compacts is given in Fig. 12.44

Table 12.19 Typical room-temperature tensile properties of HIP consolidated titanium alloy compacts as influenced by oxygen content(a) Powder manufacturing process

Tensile strength

Yield strength

Oxygen content, ppm

MPa

ksi

MPa

ksi

Elongation, %

Ti-6Al-4V Mechanical attrition Rotating electrode Hydride-to-hydride

1750 900 1570

1000 1000 1025

145 145 149

940 925 970

136 134 141

1.5 7.5 2.0

Ti-5Al-2.5Sn Rotating electrode Gas attrition

980 3530

905 895

131 130

905 …

131 …

4.0 …

(a) All data are for compacts hot pressed to 1380 MPa (200 ksi) at 1010 °C (1850 °F).

Table 12.20 Typical room-temperature tensile properties of hot isostatically pressed consolidated Ti-6Al-4V alloy made from prealloyed powders produced under various conditions Tensile strength

Yield strength

Orientation

MPa

ksi

MPa

ksi

Elongation(a), %

Reduction in area, %

Longitudinal

938.4 936.3

136.1 135.8

850.8 868.1

123.4 125.9

Transverse

950.8 936.3 932.9 941.9 896.4(a)

137.9 135.8 135.3 136.6 130(b)

863.3 848.8 843.3 848.8 827.4(b)

125.2 123.1 122.3 123.1 120(a)

20.0 18.0 18.0 18.0 23.0 20.0 10.0

37.0 37.4 40.2 35.6 42.2 39.1 25(a)

S AMS 4928-H

(a) Minimum. (b) Consolidated material made by hot isostatic pressing at 950 °C (1750 °F) for 10 h at 100 MPa (15 ksi). Vacuum annealed for 10 h at 700 °C (1300 °F). Hydrogen after vacuum annealing equals 0.0057%.

Table 12.21 Typical room-temperature tensile properties and toughness of hot isostatically pressed consolidated Ti-6Al-4V alloy made from prealloyed powders produced under various conditions Titanium prealloyed powder preparation 0.2% yiel d strength

Ultimate tensile strength

KIc or KQ

Compaction temperature

Condition(a)

MPa

ksi

MPa

ksi

Elongation, %

MPa m

ksi in.

Powder process

°C

°F

Other variables

HIP HIP (PSV) and β annealed HIP and BUS treated HIP and TCP treated HIP and annealed (700 °C, or 1290 °F) (REP) HIP, annealed (700 °C, or 1290 °F), and STA (955-480 °C, or 1750-855 °F) HIP and annealed (700 °C, or 1290 °F) (PREP) ELI; HIP (as-compacted) ELI; HIP and β annealed HPLT and HIP (as-compacted) HPLT, HIP, and RA (815 °C, or 1500 °F) HIP and rolled (955 °C, or 1750 °F) (T) HIP, rolled (955 °C, or 1750 °F), and β annealed L or LT T or TL HIP, rolled (950 °C, or 1740 °F), and STA (960-700 °C, or 1760-1290 °F) HIP, forged (950 °C, or 1740 °F), and STA (960-700 °C, or 1760-1290 °F) VHP (830 °C, or 1525 °F) (as-compacted) VHP (760 °C, or 1400 °F) (as-compacted) ROC (900 °C, or 1650 °F) (as-compacted) ROC (900 °C, or 1650 °F) and RA (925 °C, or 1695 °F) ROC (650 °C, or 1200 °F) (as compacted) ROC (600 °C, or 1100 °F) and RA (815 °C, or 1500 °F) Minimum properties (MIL-T-9047)

861 1020 965 931 820 1034

125 148 140 135 119 150

937 1095 1048 1021 889 1130

136 159 152 148 129 164

17 9 8 10 14 9

42 21 17 16 41 34

(85) (67) ... ... (76) ...

(77) (61) ... ... (69) ...

PREP PSV PREP PREP REP REP

925 950 925 925 955 955

1695 1740 1695 1695 1750 1750

... 975 °C (1785 °F) anneal ... ... ... ...

882 855 896 1082 937 958

128 124 130 157 136 139

944 931 951 1130 1013 992

137 135 138 164 147 144

15 15 10 8 22 12

40 41 24 19 38 35

(73) (99) 93 ... ... ...

(67) (90) 85 ... ... ...

PREP REP REP PREP PREP REP

955 955 955 650 650 925

1750 ... 1750 1300 ppm O2 1750 1020 °C (1870 °F) anneal 1200 315 MPa (46 ksi) 1200 315 MPa (46 ksi) 1695 75% rolling reduction

820 813 924

119 118 134

896 896 1041

130 130 151

13 11 15

31 23 35

73 61 ...

66 55 ...

REP REP REP

925 925 950

1695 1695 1740

75% rolling reduction 75% rolling reduction 60% rolling reduction

1000

145

1062

154

14

35

...

...

REP

915

1680

56% forging reduction

945 972 882 827 1131 965 827

137 141 128 120 164 140 120

993 1014 904 882 1179 1020 896

144 147 131 128 171 148 130

19 16 14 16 10 15 10

38 38 50 46 23 43 25

... ... ... ... ... ... ...

... ... ... ... ... ... ...

REP REP PREP PREP PREP PREP ...

830 760 900 900 600 600 ...

1525 1400 1650 1650 1110 1110 ...

... ... As-ROC 925 °C (1695 °F) RA As ROC 815 °C (1500 °F) RA ...

Reduction in area, %

(a) HIP, hot isostatic pressing: PSV, pulverization sous vide (powder under vacuum), French-made powder; BUS, broken-up structure; TCP, thermochemical processing; REP, rotating electrode process; STA, solution treated and aged; PREP, plasma rotating electrode process; ELI, extra-low interstitial; HPLT, high-pressure low-temperature compaction; RA, recrystallization annealed; T, transverse; L, longitudinal; LT, longitudinal-transverse; TL, transverse-longitudinal; VHP, vacuum hot pressing; ROC, rapid omnidirectional compaction.

116 / Titanium: A Technical Guide where properties of compacts with varying densities are compared to the wrought alloy scatter band. The fracture toughness of compacts

Fig. 12.42

made of blended elemental and plasma rotating electrode powder are frequently claimed to be the equivalent of, or superior to, wrought

Comparison of Ti-6Al-4V alloy room-temperature fatigue life scatter bands for several powder compact types (prealloyed, PA, and blended elemental, BE, powders) with wrought mill-annealed material (IM, in-

got metallurgy)

Comparison of room-temperature fatigue crack propagation rate for a Ti-6Al-4V powder metallurgy compact with the scatter bands for wrought ingot metallurgy products of the alloy. I/M, ingot metallurgy; P/M, powder metallurgy

Fig. 12.43

mill-annealed forgings. Equivalence or superiority of powder to wrought product is likely only to be achieved when low-chloride powder is used. Powder versus Cast versus Wrought Titanium Alloys. Typical room-temperature properties of P/M, cast, and wrought titanium products from a variety of alloys are compared in Table 12.22. A comparison of the fatigue properties of the same three material forms for Ti-6Al-4V is illustrated in Fig. 12.45. Notch behavior is a concern for normal titanium applications, and smooth results, as given in Fig. 12.45, may not sufficiently define alloy capability in fatigue. Figure 12.46 gives a “busy” comparison of the notch and smooth behavior of all three product forms (wrought, cast, and P/M). Head-to-head comparisons of any alloy are difficult to find, so property comparisons such as these tend to involve, for example, different heats, processing sources, and test sources. Under ideal conditions, the mechanical properties of cast or PA P/M material of Ti-6Al-4V can be close to those of wrought ingot metallurgy product. The effects of heat treatment, including cast HIP or powder HIP cycles, along with cooling rates within a given component, markedly affect properties. When comparable microstructures are produced, properties of fully densified castings or P/M material should be identical to wrought material. Usually only beta-annealed structures can be

Effect of density on room-temperature fatigue strength of cold isostatically pressed (CIP) and sintered Ti-6Al-4V compacts made from blended elemental powders. Note that the higher densities are only possible in the low-chloride material with broken-up structure (BUS). TCP, thermochemical processing; HIP, hot isostatically pressed

Fig. 12.44

Relationships among Structures, Processing, and Properties / 117 Many of the available alpha and alpha-beta titanium alloys have been evaluated at subzero temperatures, but service experience at such temperatures has been gained only for a few alloys. Ti-5Al-2.5Sn and Ti-6Al-4V have very high strength-to-weight ratios at cryogenic temperatures and have been the preferred alloys for special applications at temperatures from –196 to –269 °C (–320 to –452 °F).

comparably produced in all three product forms. Note, however, that the alpha-beta processed condition is more frequently used for alloys such as Ti-6Al-4V. Explicit comparisons of cast or P/M products with the best alpha-beta processed wrought alloys are not readily available.

Among these applications have been spherical pressure vessels that are part of the propulsion and reaction control systems for rockets and launch boosters. These pressure vessels were fabricated by welding together hemispherical forgings that had been machined to the desired thickness. The Ti-5Al-2.5Sn alloy also has been used for fuel pump impellers for pumping liquid hydrogen. CP titanium has been

Low-Temperature Service All structural metals undergo changes in properties when cooled from room temperature to temperatures below 0 °C (32 °F) in the “subzero” range. The greatest changes in properties occur when the metal is employed in cryogenic applications and cooled to very low temperatures near the boiling points of liquid hydrogen and liquid helium. Cryogenic applications for titanium alloys include components for spacecraft and high-pressure rocket engines. Most metals and alloys with body-centered cubic crystal structure (the structure of the beta phase in titanium) undergo a ductile to brittle transformation at sufficiently low temperatures. Beta titanium alloys are metastable and want to revert to alpha and other phases, so they may not be completely brittle at low temperatures. However, the low-temperature ductility of beta titanium alloys will be limited. Consequently, titanium alloys, which are all beta or contain substantial amounts of beta phase, are not generally considered very useful for low temperatures. Ductility is a consideration, as noted, and Table 12.23 shows how the ductility of even alloys considered ductile is reduced at cryogenic temperatures.

Table 12.22

1200 160

1000 120

800 Cast HIP prealloyed parts powder

600

Wrought anneal

80

400 40 200 0 102

103

104

105

106

107

0 108

Cycles to failure, Nf

Fig. 12.45

Fatigue scatter bands for ingot metallurgy, castings, and powder metallurgy products of Ti-6Al-4V alloy

Comparison of typical room-temperature properties of wrought, cast, and powder metallurgy titanium products Tensile strength

Yield strength

Impact strength(a)

Elongation,

Reduction in

MPa

ksi

MPa

ksi

%

area, %

J

ft · lbf

Unalloyed Ti Wrought bar, annealed Cast bar, as cast P/M compact, annealed(b)

550 635 480

80 92 70

480 510 370

70 74 54

18 20 18

33 31 22

35 26 …

26 19 …

Ti-5Al-2.5Sn-ELI Wrought bar, annealed Cast bar, as cast P/M compact, annealed and forged(c)

815 795 795

118 115 115

710 725 715

103 105 104

19 10 16

34 17 27

… … …

… … …

1000

145

925

134

16

34

22

16

1025 1015 1180

149 147 171

880 890 1085

128 129 157

12 10 6

19 16 11

19 … …

14 … …

825–855 925 965

120–124 134 140

740–785 840 895

107–114 122 130

5–8 12 4

8–14 27 6

… … …

… … …

1125 1105 965

163 160 140

1055 965 840

153 140 122

16 6 5

38 11 5

20 14 …

15 10 …

Product and condition

Ti-6Al-4V Wrought bar, annealed Cast bar As cast Annealed Solution treated and aged(d) P/M compact Annealed (b) Annealed and forged(c) Solution treated and aged(d) Ti-6Al-6V-2Sn Wrought bar, annealed Cast bar, as cast P/M compact, annealed(b)

Maximum stress, ksi

Maximum stress, MPa

Cast plus HIP

P/M, powder metallurgy. (a) Charpy, at –40 °C (–40 °F). (b) Approximately 94% dense. (c) Almost 100% dense. (d) Aging treatment not specified

118 / Titanium: A Technical Guide used for tubing and other small-scale cryogenic applications that involve only low stresses in service.

The Ti-5Al-2.5Sn alloy usually is used in the mill-annealed condition and has a 100% alpha microstructure. The Ti-6Al-4V alloy can be

1000 Wrought (smooth) [R = 0.06–0.1]

140

Powder pressed and forged (smooth) [R = 0.1]

120

Stress, MPa

Wrought (KT = 3) [R = 0.06 – 0.1]

100

600 80 400

200

Stress, ksi

800

60

As cast (notched, KT = 3) [R = 0.06]

40

20

Powder pressed and forged (notched, KT = 4) [R = 0.1] 0

• Titanium and its alloys must not be used for

0 104

105

106

107

transfer or storage of liquid oxygen.

Lifetime, cycles

Fig. 12.46

Table 12.23 Ti-8Al-1Mo-1V Ti-6Al-3Nb-2Zr Ti-6Al-4V Ti-6Al-4V

• Titanium must not be used where it will be

exposed to air while below the temperature at which oxygen will condense on its surfaces.

Notch effect on wrought, cast, and powder metallurgy forms of Ti-6Al-4V alloy

Low-temperature ductility of some alpha-beta titanium alloys

Composition

Condition(a)

Elongation(b)

8 h at 790 °C (1450 °F) + FC + 15 min at 790 °C (1450 °F) + AC 1 h at 800 °C (1470 °F) + AC 1 h at 1050 °C (1920 °F)(c) + AC

1.2% at 20 K 4 to 5% at 4.2 K 4% at 4 K (ELI) 1.5% at 4 K (normal) 2.9% at 20 K (ELI) 2.4% at 20 K (normal)

1

2

to 4 h at 710–820 °C (1310–1510 °F)

(a) FC, furnace cool; AC, air cool. (b) ELI, extra-low interstitial content. (c) β anneal

Fig. 12.47

Young’s modulus for Ti-5Al-2.5Sn and Ti-6Al-4V alloys versus temperature in the low-temperature region

used in the annealed condition or in the solution-treated and aged condition. For maximum toughness in cryogenic applications, the annealed condition usually is preferred. Impurities, such as iron and the interstitials oxygen, carbon, nitrogen, and hydrogen, tend to reduce the toughness of these alloys at both room temperature and subzero temperatures. For maximum toughness, extra low interstitial (ELI) grades are specified for critical applications. Note that the iron and oxygen contents of the ELI grades are substantially lower than those of the normal interstitial (NI) grades. Iron is a strong stabilizer of the beta phase. The NI grades are suitable for service to –l96 °C (–320 °F). For temperatures below –l96 °C (–320 °F), ELI grades generally are specified. For ELI grades, reduced strength at room temperature must be considered in design for pressure vessel service. There are two precautions that should be emphasized in considering titanium and titanium alloys for service at cryogenic temperatures:

Fig. 12.48

Any abrasion or impact of titanium that is in contact with liquid oxygen causes ignition. (Pressure vessels in contact with liquid oxygen in the Apollo launch vehicles were produced from Inconel 718 rather than from Ti-6Al-4V alloy to avoid this problem.) Tensile properties typical of titanium and of titanium alloys Ti-5Al-2.5Sn and Ti-6Al-4V at room temperature and at subzero temperatures are presented in Table 12.24. Marked increases in yield and tensile strengths are evi-

Poisson’s ratio for Ti-5Al-2.5Sn and Ti-6Al-4V alloys versus temperature in the low-temperature region

Relationships among Structures, Processing, and Properties / 119 Table 12.24

Typical tensile properties of titanium and titanium alloys from room temperature to subzero temperatures

Temperature

Tensile strength

Yield strength Elongation, %

Reduction in area, %

67.6 89.2 136 173

25 25 18 8

69.0 93.4 140 182

Ti-5Al-2.5Sn sheet, nominal interstitial annealed, longitudinal orientation 24 75 850 123 795 –78 –108 1080 156 1020 –196 –320 1370 199 1300 –253 –423 1700 246 1590

Notch tensile strength(a)

Young’s modulus

MPa

ksi

GPa

106 psi

… … … …

785 … 1100 875

114 … 159 127

… … … …

… … … …

25 20 14 7

… … … …

800 905 1120 880

116 131 163 128

… … … …

… … … …

115 148 188 231

16 13 14 7

… … … …

1130 1310 1630 1430

164 190 236 208

105 115 120 130

15.4 16.6 17.7 18.5

Ti-5Al-2.5Sn sheet, nominal interstitial annealed, transverse orientation 24 75 895 130 860 –78 –108 1050 152 1020 –196 –320 1430 208 1370 –253 –423 1670 242 1610 –268 –450 1590 231 …

125 148 198 234 …

14 12 12 6 1.5

… … … … …

1170 1250 1630 1290

170 181 236 187

… … … …

… … … …

Ti-5Al-2.5Sn-ELI sheet, annealed, longitudinal orientation 24 75 800 116 –78 –108 960 139 –196 –320 1300 188 –253 –423 1570 228

740 880 1210 1450

107 128 175 210

16 14 16 10

… … … …

1060 1190 1560 1670

154 173 226 242

115 125 130 130

16.4 18.0 18.6 19.2

Ti-5Al-2.5Sn-ELI sheet,annealed, transverse orientation 24 75 805 117 –78 –108 950 138 –196 –320 1300 188 –253 –423 1570 228

760 895 1230 1480

110 130 179 214

14 12 14 8

… … … …

1100 1260 1570 1530

159 182 228 222

110 125 130 140

16.0 18.1 18.9 20.1

Ti-5Al-2.5Sn-ELI sheet/weldment, annealed, electron beam weld 24 75 815 118 –196 –320 1300 189 –253 –423 1510 219

785 1210 1380

114 176 200

… … …

… … …

… … …

… … …

… … …

… … …

Ti-5Al-2.5Sn-ELI plate, annealed, longitudinal orientation 24 75 765 111 –253 –423 1430 208

705 1390

102 202

33 17

43 32

… …

… …

… …

… …

Ti-5Al-2.5Sn-ELI forgings, as forged, tangential orientation 24 75 835 121 –78 –108 980 142 –196 –320 1260 182 –253 –423 1420 206

760 905 1100 1260

110 131 159 182

15 12 15 13

36 31 30 22

… … … …

… … … …

… … … …

… … … …

Ti-6Al-4V-ELI sheet, annealed, longitudinal orientation 24 75 960 139 –78 –108 1160 168 –196 –320 1500 217 –253 –423 1770 256

890 1100 1420 1700

129 160 206 246

12 9 10 4

… … … …

1120 1220 1460 1500

162 177 211 217

110 115 120 130

16.2 16.6 17.5 18.6

Ti-6Al-4V-ELI sheet, annealed, transverse orientation 24 75 960 139 –78 –108 1170 169 –196 –320 1500 218 –253 –423 1750 254

895 1100 1460 1700

130 160 212 246

12 12 11 4

… … … …

1130 1260 1440 1550

164 183 209 225

110 115 125 130

16.0 16.5 18.2 19.2

Ti-6Al-4V-ELI plate, annealed, longitudinal orientation 24 75 890 129 –253 –423 1640 238

840 1600

122 232

15 …

37 8

… …

… …

… …

… …

Ti-6Al-4V-ELI forgings, as forged, longitudinal orientation 24 75 970 141 –78 –108 1160 168 –196 –320 1570 227 –253 –423 1650 239

915 1120 1480 1570

133 163 214 227

14 13 11 11

40 31 31 24

1330 1560 1900 1820

193 226 276 264

… … … …

… … … …

Ti-6Al-4V-ELI forging, recrystallization annealed(b) 24 75 890 129 –196 –320 1430 207

825 1370

120 198

14 10

41 16

… …

… …

110 120

16.1 17.5

°C

°F

MPa

ksi

MPa

ksi

Ti-75A sheet, annealed, longitudinal orientation 24 75 580 –78 –108 750 –196 –320 1050 –253 –423 1280

84.3 109 152 186

465 615 940 1190

Ti-75A sheet, annealed, transverse orientation 24 75 585 –78 –108 760 –196 –320 1060 –253 –423 1340

85.1 110 153 194

475 645 965 1260

(a) Kt = 6.3 for all three sheet forms; Kt = 5–8 for Ti-6Al-4V-ELI forgings. (b) FC, furnace cool; AC, air cool. Recrystallization annealing treatment: 930 °C (1700 °F) 4 h, FC to 760 °C (1400 °F) in 3 h, cooled to 480 °C (900 °F) in 3 h, AC. 4

120 / Titanium: A Technical Guide Table 12.25

Fracture toughness of two titanium alloys and weldments Room temperature yield strength

Fracture toughness (KIc),

Alloy and condition

Form

MPa

ksi

Specimen design

Ti-5Al-2.5Sn-NI, annealed

Plate

Ti-5Al-2.5Sn-ELI, annealed

Bar Plate

Ti-5Al-2.5Sn-ELI, as forged Forging

876 876 876 871 703 703 760

127 127 127 126 102 102 110

CT Bend Bend CT CT Bend CT

Ti-5Al-2.5Sn-ELI Ti-6Al-4V-NI, annealed Ti-6Al-4V-ELI, as forged Ti-6Al-4V-ELI, RA

Forging(a) Bar Forging Forging

779 942 830 830

113 136 120 120

CT CT CT CT

Ti-6Al-4V-ELI, RA,electron beam welded, SR

Forging

830

120

CT

Weldment

…

…

…

24 °C (75 °F) Orientation

MPa m

ksi in.

L-T L-T L-S T-S L-T L-T R-L R-C … T-L T-L M-L(b) M-R(b) M-R(b)

71.8 … … 77.2 … … … … … 47.4 … … … …

M-L(b) M-R(b) M-R(b)

… … …

–196 °C (–320 °F)

–253 °C (–423 °F)

MPa m

ksi in.

MPa m

65.4 … … 70.3 … … … … … 43.2 … … … …

53.4 … … 42.1 111 … … … … 38.8 61.0 62.8 62.0 61.1(c)

48.6 … … 38.3 101 … … … … 35.3 55.5 57.2 56.4 55.6(c)

… … …

56.9(c) 57.1(d) 51.0(e)

51.8(c) 52.0(d) 46.4(e)

–269 °C (–452 °F)

ksi in.

… … 51.4 46.8 50.2 45.7 … … … … 89.6 81.5 79.4 72.3 58.5 53.2 54.4–75.3 49.5–68.5 … … … … … … … … … … … … …

… … …

MPa m ksi in.

… … … 42.0 … … … … … 38.5 54.1 … … …

… … … 38.2 … … … … … 35.1 49.2 … … …

… … …

… … …

NI, normal interstitial content; ELI, extra low interstitial content; AC, air cool; FC, furnace cool; RA, recrystallization annealed: 930 °C (1700 °F) 4 h, FC to 810 °C (1400 °F) in 3 h, cool to 480 °C (900 °F) in 0.75 h, AC; SR, stress relieved: 540 °C (1000 °F) 50 h, AC; CT, compact tension. R-C and R-L are specific orientations in cylindrical sections. L-T, L-S, T-S, and T-L are specific orientations in rectangular specimens. (a) Range for 18 tests. (b) M-L and M-R are specific orientations in a spherical forging. (c) Fusion zone. (d) Heat-affected zone. (e) Heat-affected zone boundary

dent for commercial titanium and for titanium alloys because test temperature is reduced from room temperature to –253 °C (–423 °F). In the cryogenic temperature range, these alloys have the highest strength-to-weight ratios of all fusion-weldable alloys that retain nearly the same strength in the weld metal as in the base metal. Yield and tensile strengths of an electron beam weld of Ti-5Al-2.5Sn-ELI sheet also are presented in Table 12.24. The notch strengths given in Table 12.24 indicate that Ti-5Al-2.5Sn and Ti-6Al-4V alloys retain sufficient notch toughness for use in temperatures as low as –253 °C (–423 °F). However, the tensile data do not show any substantial improvement in ductility or notch toughness for the ELI grade of Ti-5Al-2.5Sn

Table 12.26

sheet over the normal interstitial grade—except at very low temperatures. The recrystallization annealing treatment used for the Ti-6Al-4VELI forging was developed as a means of improving fracture toughness in large forgings and thick plate. Values of Young’s modulus for titanium alloys increase substantially as test temperature is decreased, as shown in Table 12.24 and by the data plotted in Fig. 12.47. Values of Poisson’s ratio for Ti-5Al-2.5Sn and Ti-6Al-4V alloys are plotted in Fig. 12.48. Fracture Toughness. Available data on plane-strain fracture toughness, KIc, at subzero temperatures for alloys Ti-5Al-2.5Sn and Ti-6Al-4V are presented in Table 12.25 along with corresponding data for weldments. These

data indicate that there is a modest reduction in fracture toughness as test temperature is reduced from room temperature to subzero temperatures. However, the ELI grades have better toughness than the corresponding normal interstitial grades at subzero temperatures. The limited data for electron beam weldments indicate that at –l96 °C (–320 °F) there is a slight reduction in toughness in both fusion and heat-affected zones when compared to the base metal in Ti-6Al-4V-ELI welds. Fatigue Strength. Values of fatigue strength at 106 cycles for titanium alloy base metal and weldments at room temperature and at subzero temperatures, based on results of axial and flexural fatigue tests, are presented in Table 12.26. For the unnotched specimens of parent metal,

Fatigue properties of two titanium alloys in various conditions tested at room temperature and cryogenic temperatures Fatigue strengths at 106 cycles 24 °C (75 °F)

–196 °C (–320 °F)

–253 °C (–423 °F)

Stressing mode

Stress ratio

Kt

MPa

ksi

MPa

ksi

MPa

ksi

Ti-5Al-2.5Sn-ELI sheet, annealed

Axial

0.01

Ti-5Al-2.5Sn-ELI sheet(a) Ti-5Al-2.5Sn-ELI bar, annealed(b) Ti-6Al-4V-ELI sheet(c)

Axial Axial Axial

0.01 0 0.01

Ti-6Al-4V-ELI sheet(a) Ti-6Al-4V sheet, annealed

Axial Flex

0.01 –1.0

1 3.5 1 1 1 3.5 1 1 3.1

495 220 485 760 505 285 600 345 170

72 32 70 110 73 41 87 50 25

815 205 565 985 675 295 595 550 185

118 30 82 143 98 43 86 80 27

760 160 425 925 895 275 560 530 255

110 23 62 134 130 40 81 77 37

Alloy and condition

(a) Gas-tungsten arc welded, base-metal filler. (b) Cyclic frequency, 28 Hz. (c) Solution treated and annealed: 900 °C (1650 °F) 5 min, water quench; 540 °C (1000 °F) 4 h, air cool

Relationships among Structures, Processing, and Properties / 121 fatigue strength increased substantially when the test temperature was reduced from room temperature to –l96 °C (–320 °F). When the test temperature was reduced to –253 °C (–423 °F), the fatigue strengths for some series of alloys were lower than at –l96 °C (–320 °F). Fatigue strengths were much lower in the notched specimens than in the corresponding unnotched specimens. At about –196 and –253 °C (–320 and –423 °F), the welded specimens had lower fatigue strengths than the base metal specimens. Therefore, in designing welded structures of titanium alloys that will be subjected to fatigue loading at subzero temperatures, the weld areas usually should be thicker than the remaining areas. Hemispheres for spherical pressure vessels are machined so that the butting sections for the equatorial welds are thicker than the remaining sections, excluding inlet and discharge ports. Fatigue Crack Propagation Rates. Data on FCP rates for Ti-5Al-2.5Sn and Ti-6Al4V alloys at low temperature are plotted in Fig. 12.49. Over part of the stress intensity range, the fatigue crack growth rates for Ti-6Al-4V-ELI are higher at cryogenic temperatures than at room temperature at the same ΔK values.

Fig. 12.49

Fatigue crack propagation rates for Ti-5Al-2.5Sn and Ti-6Al-4V alloys in the low-temperature region. NI = normal interstitial content; ELI = extra low interstitial content

Titanium: A Technical Guide Matthew J. Donachie, Jr., p123-130 DOI:10.1361/tatg2000p123

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 13

Corrosion Resistance Corrosion is a process that results in the degradation of a metal or an alloy by removal of atoms. It can occur by the interaction of a gas, such as oxygen, which converts the surface atoms to oxides that can adhere or be scaled off. Alternately, it can occur electrochemically as a coupled reaction between an anode and at least one cathode. The various forms of corrosion are myriad but can often be reduced to a few types. We recognize general corrosion, pitting or crevice corrosion, and other forms of attack on titanium and its alloys. Additional information about corrosion and specific information about corrosion rates for titanium alloys can be found in Appendix F. Although titanium and its alloys are used chiefly for their desirable mechanical properties, among which the most notable is their high strength-to-weight ratio, another important characteristic of titanium and its alloys is their outstanding resistance to corrosion. Commercially pure (CP) titanium offers excellent corrosion resistance in most environments, except those media that contain fluoride ions. Titanium is more corrosion resistant than stainless steel in many industrial environments, and its use in the chemical process industry has been gradually increasing. Titanium exhibits excellent resistance to atmospheric corrosion in both marine and industrial environments. Successful application of titanium and its alloys can be expected in mildly reducing to highly oxidizing environments in which protective oxide films spontaneously form and remain stable. Titanium and its alloys have been found to be largely immune to corrosion-related failure in most environments, although titanium alloys are generally less resistant to corrosion than CP titanium. In unalloyed titanium and many titanium alloys, weld zones are just as resistant to corrosion as the base metal is. Other fabrication processes (such as bending or machining) also appear to have no influence on basic corrosion resistance. The major corrosion problem with titanium alloys appears to be crevice corrosion, which occurs in locations where the corroding media

are virtually stagnant. Pits, if formed, can progress in a similar manner. A general comparison of corrosion resistance for titanium and some of its alloys with other metals is provided in Fig. 13.1.

Corrosion Behavior and Corrosion Resistance Gases. Titanium has limited oxidation resistance in air at temperatures above approximately 650 °C (1200 °F) and interacts with oxygen to dissolve it interstitially at temperatures as low as approximately 427 °C (800 °F). Chlorides or hydroxides deposited on the surface of titanium can accelerate oxidation. Titanium and its alloys resist H2S and CO2 gases at temperatures up to approximately 260 °C (500 °F). Exposure to liquid or gaseous oxygen, nitrogen tetroxide, or red fuming nitric acid can cause titanium to react violently under impact

Fig. 13.1

Range of corrosion resistance of metal systems

loading. Wet chlorine has essentially no effect on titanium; titanium is used extensively for handling wet chlorine gas. On the other hand, dry chlorine gas is especially harmful. Liquids. Unalloyed titanium is highly resistant to the corrosion normally associated with many natural environments, including seawater, body fluids, and fruit and vegetable juices. Titanium exposed continuously to seawater for about 18 years has undergone only superficial discoloration. Molten sulfur, many organic compounds (including acids and chlorinated compounds), and most oxidizing acids have essentially no effect on this metal. Consequently, titanium is used extensively for handling salt solutions (including chlorides, hypochlorides, sulfates, and sulfides) and nitric acid solutions. On the other hand, hot, concentrated, low-pH chloride salts (such as boiling 30% AlCl3 and boiling 70% CaCl2) corrode titanium. Warm or concentrated solutions of hydrochloric, sulfuric, phosphoric, and oxalic acids also are damaging. In general, all acidic solutions that are

124 / Titanium: A Technical Guide reducing in nature corrode titanium unless they contain inhibitors. Strong oxidizers, including anhydrous red fuming nitric acid and 90% hydrogen peroxide, also cause attack. Ionizable fluoride compounds, such as NaF and HF, activate the surface and can cause rapid corrosion. Commercially pure (CP) titanium is the preferred material of construction for much of the equipment built to handle industrial brines. It is used for pumps, piping, thermowells, heat exchangers, crystallizers, evaporators, condensers, and many other items that are subject to the corrosive action of these brines. Some titanium alloys find use in biomedical applications where they appear to be the most corrosion resistant of the structural metals used as prostheses. Ti-6Al-4V again is the metal of choice and has been particularly successful in hip joint replacement surgery. Interaction with Hydrogen. Titanium has been used to contain liquid or supercritical hydrogen at cryogenic temperatures, but above –l00 °C (–150 °F), hydrogen can be absorbed and go on to diffuse into an alloy. If it does, the dissolved hydrogen can severely embrittle tita-

Table 13.1 Species that inhibit the corrosion of titanium alloys in reducing acids Inhibitor category

Species

Oxidizing metal cations

Oxidizing anions

Precious metal ions Oxidizing organic compounds

Others

Ti4+, Fe3+, Cu2+, Hg4+, Ce4+, Sn4+, VP2+ , Te4+, Te6+, Se4+, Se6+, Ni2+ 2– 2− ClO2− 4 , Cr 2 O 7 , MoO 4 , − − MnO2− 4 , WO 4 , IO 3 , − − − VO3− 4 , VO 3 , NO 3 , NO 2 , S2 O2− 3 Pt2+, Pt4+, Pd2+, Ru3+, Ir3+, Rh3+, Au3+ Picric acid, o-dinitrobenzene, 8-nitroquinoline, m-nitroacetanilide, trinitrobenzoic acid, and certain other nitro, nitroso, and quinone organics O2, H2O2, C lO–3 , OCl–

nium. The potential for embrittlement is increased where hydrogen flow rates are high or where coatings on the titanium become damaged. Minor Alloy Element Changes. Titanium that is intentionally alloyed with trace amounts of palladium or molybdenum and nickel also is used to provide corrosion resistant service. For example, the Ti-0.2Pd alloy and the Ti-0.3Mo-0.8Ni alloy are characterized by improved crevice corrosion resistance, as well as improved corrosion resistance in reducing environments. Product Form and Welding. Weldments and castings of CP grades and alpha-beta alloys such Ti-6Al-4V generally exhibit corrosion resistance similar to that of their unwelded, wrought counterparts. These titanium alloys contain so little alloy content and second phase that metallurgical instability and thermal response are not significant. Therefore, titanium weldments and associated heat-affected zones generally do not experience corrosion limitations in welded components when normal passive conditions prevail for the base metal. However, under marginal or active conditions, for corrosion rates greater than or equal to 100 µm/year, weldments can experience accelerated corrosion attack relative to the base metal, depending on alloy composition. The increasing impurity (e.g., iron, sulfur, oxygen) content associated with the coarse, transformed beta microstructure of weldments appears to be a factor. Few published data are available concerning the corrosion resistance of titanium alloy weldments and castings other than Ti-6Al-4V, and limited information on other product forms has been reported.

Corrosion Technology Protective Oxide Layer. Although titanium is chemically reactive, the thin oxide film that forms on titanium surfaces in most corrosive media is relatively impervious and, therefore,

Table 13.2 Effect of certain multivalent metal ions on the corrosion of titanium in boiling reducing acids Corrosion rate

Inhibiting ion

Fe3+

Cu2+

Mo6+

Cr6+

V5+

Concentration of inhibiting ion, ppm

mm/yr

mils/yr

mm/yr

mils/yr

0 100 500 0 100 500 0 100 500 0 100 500 0 100 500

29 0.025 0.02 29 0.033 nil 29 nil nil 29 nil nil 29 0.02 0.008

1142 1 0.8 1142 1.3 nil 1142 nil nil 1142 nil nil 1142 0.8 0.3

>76.2 0.208 0.069 >76.2 0.419 0.361 >76.2 0.001 nil >76.2 0.001 0.001 >76.2 0.005 0.005

>3000 8.2 2.7 >3000 16.5 14.2 >3000 0.04 nil >3000 0.04 0.04 >3000 0.2 0.2

Boiling 5% HCl

Boiling 10% H2SO4

quite protective. The excellent corrosion resistance of titanium alloys results from the formation of this very stable, continuous, highly adherent, and protective oxide film. Because titanium metal is highly reactive and has an extremely high affinity for oxygen, these beneficial surface oxide films form spontaneously and instantly when fresh metal surfaces are exposed to air and/or moisture. In fact, a damaged oxide film can generally reheal itself instantaneously if at least traces (i.e., parts per million) of oxygen or water (moisture) are present in the environment. When titanium is not corrosion resistant, it is because the film is not fully protective. Reducing conditions, very powerful oxidizing environments, and the presence of fluoride ions diminish the protective nature of the oxide film, but its stability and integrity can be improved substantially by adding inhibitors to the environment. If titanium is exposed to strongly oxidizing or reducing environments, severe attack of the metal can ensue. Moisture and a source of oxygen are important in retaining protectivity. In the complete absence of moisture under oxidizing conditions, any surface film that is formed is not protective, and oxidation in depth can take place, often in the form of a violent exothermic reaction. Another possibility for lack of surface protection is that under continuous wear or sliding contact conditions with other metals, the protective oxide may not reform, thereby allowing accelerated corrosion of titanium. Oxide Breakdown and the Role of Inhibitors. Various oxidizing species can effectively inhibit the corrosion of titanium in reducing acid environments when present in very small concentrations. The dissolved oxidizing species serve to depolarize cathodic reactions. On titanium alloy surfaces this passivates the alloy by shifting the alloy potential in the noble direction. These inhibiting species often occur as natural process stream constituents or contaminants and need not be intentionally added to achieve complete titanium alloy passivation. (See the section “Passivation” in this Chapter.) Many of these species, which include a host of multivalent transition-metal ions, are very potent inhibitors and can be effective at concentrations of 100 ppm or less (Tables 13.l and 13.2). Metallic ions and oxygen from the air are apparently absorbed into the surface of titanium; the oxygen combines with titanium to form the protective oxide. Strong oxidizing conditions (such as nitric acid, air at moderately high temperatures, and anodic treatments) promote corrosion resistance of titanium and its alloys through growth of the oxide film. Dissolved oxygen is an important inhibitor in hot or mildly reducing chlorine solutions, but if its supply is restricted, as in deep crevices, corrosion can be accelerated. Breakdown of the protective oxide layer (passive layer) can occur from dry corrosive media (such as red fuming nitric acid), nonoxidizing aqueous environments as defined by a Pourbaix diagram, and

Corrosion Resistance / 125 pitting or crevice attack in near-neutral aqueous solutions (particularly in the presence of halides). Most acidic solutions (except those containing soluble fluorides) can be inhibited by the presence of even small amounts of oxidizing agents and heavy-metal ions. Thus, titanium can be used in certain industrial process solutions (including hydrochloric and sulfuric acids) that otherwise would be corrosive. Nitric and chromic acids, along with dissolved salts of iron, nickel, copper, and chromium, are especially effective inhibitors. Attack by red fuming nitric acid and chlorine gas can be inhibited by small amounts of water. Passivation. Titanium is not corrosion resistant in the same way that gold or other noble metals are corrosion proof. Rather, as stated above, titanium relies on the formation of a strongly protective oxide for protection against the environment. When a satisfactory oxide surface film is present then, in electrochemical parlance, titanium is made passive and not subject to further oxidation or corrosion attack. The nature, composition, and thickness of the protective surface oxides that form on titanium alloys depend on environmental conditions. In most aqueous environments, the oxide is typically TiO2,Ti2O3, or TiO. High-temperature oxidation tends to promote the formation of the chemically resistant form of TiO2 known as rutile, whereas lower temperatures often generate the more amorphous form of Ti2O3 known as anatase, or promote formation of a mixture of rutile and anatase. Although these naturally formed films are typically less than 10 nm thick and are invisible to the eye, the TiO2 oxide is generally chemically resistant and is attacked by very few substances, including hot, concentrated HCl, H2SO4, NaOH, H3PO4, and, most notably, HF. This thin surface oxide also is resistant to hydrogen permeation. An understanding of the corrosion behavior of titanium can be obtained by recognizing the conditions under which the oxides are thermodynamically stable. The Pourbaix (electrical potential versus pH) diagram for the titanium-water system (Fig. 13.2) depicts the wide regime over which the passive TiO2 oxide film is predicted to be stable, based on thermodynamic considerations. Oxide stability over the full pH scale is indicated over a wide range of highly oxidizing to mildly reducing potentials, whereas oxide film breakdown and the resultant corrosion of titanium occur under reducing acidic conditions. (Note that under strongly reducing, or cathodic, conditions, undesirable titanium hydride formation is predicted.)

Uniform Corrosion Processes General corrosion is characterized by a relatively uniform attack over the exposed surface of a metal. At times, general corrosion in aqueous media can take the form of mottled, severely roughened metal surfaces. This condi-

Fig. 13.2

Pourbaix diagram for titanium-water system showing areas of passivity and corrosion

tion often results from variations in the corrosion rates of localized surface patches due to variations in process scales, corrosion products, or gas bubbles. When titanium is in the fully passive condition, corrosion rates are typically much lower than 40 µm/year—well below the 130 µm/year maximum corrosion rate commonly accepted by designers as a standard for general corrosion. This very small, acceptable corrosion rate is attributable to the thin steadystate film on titanium alloy surfaces as previously indicated. As a result of the low general corrosion rate, titanium is often designed with a zero corrosion allowance in normal passive environments. In many environments in which titanium is fully resistant, slight surface oxide growth can occur. This oxide growth manifests itself as colored surfaces and very slight weight gain by test coupons. General corrosion becomes a concern in reducing acid environments, particularly as acid concentration and temperature increase. In strong and/or hot reducing acids (in the absence of inhibitors), the oxide film of titanium can deteriorate and dissolve, and the unprotected metal is oxidized to the soluble trivalent ion (Ti3+ + 3e–). This ion has a characteristic violet color in acid solutions. If dissolved oxygen or other oxidizing species are present in hot acid,

then the 3+ ion is readily oxidized to a less soluble (pale yellow) Ti4+ ion, which may subsequently hydrolyze to form insoluble TiO2 precipitates. Titanium ion hydrolysis often produces highly colored metal surfaces involving thin titanium oxide films that can inhibit subsequent corrosion. Matte gray or dull silver surface finishes can also be observed in reducing acid exposures involving severe corrosion attack. In reducing media, these are titanium hydride surface films that are typically on the order of 50 µm thick. Galvanic Corrosion. Coupling titanium to dissimilar metals usually does not accelerate corrosion of the titanium except in reducing environments, where titanium does not become passivated. Under reducing conditions, it has a galvanic potential similar to that of aluminum and undergoes accelerated corrosion when coupled to more noble metals. One version of the galvanic series in seawater is indicated in Table 13.3. In this environment, titanium exhibits a potential of about –0.1 V versus a saturated calomel reference cell, a behavior that places titanium high on the passive (noble) end of the series just below platinum, gold, and silver. In most environments, titanium is the cathodic member of any galvanic couple. Titanium can accelerate corrosion of the other member,

126 / Titanium: A Technical Guide Table 13.3 Series

Cathodic end (noble metals)

Anodic end (active metals)

Galvanic series in seawater Metal

Platinum Gold Silver Titanium Cr-Ni stainless steels, passive Straight Cr stainless steels, passive Ni-Cu alloys (Monels) Ni-Cr-Fe alloys (Inconels), passive Nickel, passive Silver solder Tin bronzes Copper nickels Silicon bronzes Copper Red and yellow brasses Aluminum bronzes Ni-Cr-Fe alloys (Inconels), active Nickel, active High-Zn yellow brasses (>30% Zn) Manganese bronzes Tin Lead Cr-Ni stainless steels, active Cast iron Wrought iron Low-carbon steel 2xxx and 7xxx aluminum alloys Cadmium Alclad aluminum alloys 6xxx aluminum alloys Galvanized steel Zinc Magnesium alloys Magnesium

but in most instances, it is itself unaffected. If the surface area of the titanium exposed to the environment is small in relation to the exposed surface area of the other metal, the effect of the titanium on the corrosion rate of the other metal is negligible. If, however, the exposed area of titanium greatly exceeds that of the other metal, severe corrosion of the other metal can result. Because titanium is nearly always the cathodic member of any galvanic couple, hydrogen can be evolved at its surface in an amount proportional to the galvanic current flow. This can result in formation of surface hydride films that generally are stable and cause no problems. At temperatures above 75 °C (170 °F), however, the hydrogen can diffuse into the metal, causing embrittlement. In some environments, titanium hydride is unstable and decomposes, or reacts, causing a loss of metal.

Alloying Additions and Corrosion The nature of the oxide film on titanium alloys basically remains unaltered in the presence of minor alloying constituents; thus, small additions (<2–3%) of most commercially used alloying elements or trace alloy impurities generally have little effect on the basic corrosion resistance of titanium in normally passive environments. For example, despite small differences in interstitial elements (carbon, oxygen, and nitrogen) and iron content, all unalloyed grades of titanium have the same useful range

of resistance to environments in which corrosion rates are normally very low. However, under active conditions in which titanium exhibits significant general corrosion, certain alloying elements can accelerate corrosion. Increasing the iron and sulfur content, for example, increases corrosion rates when corrosion rates exceed 130 µm/year. Depending on conditions, then, alloying titanium with other metals can have pronounced effects on its chemical properties. The influence of certain major alloying elements on the general and crevice corrosion behavior of various commercial titanium alloys has been determined in reducing aqueous acid media. Results indicate that vanadium and, especially, molybdenum additions (greater than ~4% Mo) improve corrosion resistance but that increasing the aluminum content appears to be detrimental. Minor variations in alloy chemistry may be of concern only under conditions in which the passivity of titanium is borderline or when the metal is fully active. Minor nickel and palladium additions are highly effective in expanding the corrosion resistance of titanium alloys under reducing conditions. Moreover, small palladium additions can significantly increase crevice corrosion resistance in hot aqueous chlorides. Enhancing Resistance to General Corrosion. Successful use of titanium alloys can be expected in mildly reducing to highly oxidizing environments in which protective TiO2 and Ti2O3 films form spontaneously and remain stable. On the other hand, uninhibited, strongly reducing acidic environments can attack titanium, particularly as temperature increases. Reducing conditions obviously are the principal concern for titanium and its alloys. By shifting the alloy potential in the noble (positive) direction through various means, it is possible to induce stable oxide film formation, often overcoming the corrosion resistance limitations of titanium alloys in normally aggressive reducing media. Anodic control of the corrosion reaction predominates when titanium is exposed to reducing acids, such as hydrochloric or sulfuric acid. Therefore, alloying with elements that reduce anodic activity should improve corrosion resistance. This can be accomplished by using alloying elements that:

• Shift the corrosion potential of the alloy in • •

the positive direction (cathodic alloying) (as previously discussed) Increase the thermodynamic stability of the alloy and, thus, reduce the ability of the titanium to dissolve anodically Increase the tendency of titanium to passivate

The first group includes noble metals, such as platinum, palladium, and rhodium. The second includes nickel, molybdenum, and tungsten. The third group includes zirconium, tantalum, chromium, and, possibly, molybdenum.

Cathodic Alloying. Considerable work has been done on the use of noble metals as alloying additions in titanium. An outgrowth of this work has been the development of Ti-0.2Pd, mentioned previously, which has considerably greater resistance to corrosion in reducing environments than does CP titanium. Alloying for Thermodynamic Stability. In studying corrosion of titanium in aqueous salt solutions, it was noted that titanium alloys containing nickel, molybdenum, or palladium were more resistant to nonoxidizing acid solutions than was CP titanium. It was concluded that they also should be more resistant to crevice corrosion. An alloy containing 2% Ni was developed and recommended for service in hot brine environments where crevice corrosion is sometimes a problem. Subsequent studies confirmed that this alloy has much better resistance to crevice corrosion than the unalloyed metal. However, the nickel addition has detrimental effects that diminish its overall value. Ti-2Ni is very susceptible to hydrogen embrittlement and is subject to severe edge cracking during rolling, a characteristic that makes it difficult to produce. Passivation Alloying. Various studies have demonstrated that corrosion resistance of titanium is improved by addition of molybdenum. The principal problem with Ti-Mo alloys is the difficulty of obtaining uniform distribution of the molybdenum in large ingots. Because titanium and molybdenum have such widely different melting points, molybdenum is difficult to dissolve and can segregate as high-density inclusions when large amounts are added. The commercial alloy Ti Code 12, which contains 0.3% Mo and 0.8% Ni, combines some of the favorable properties of nickel and molybdenum additions but avoids the negative aspects. This alloy has excellent resistance to pitting and crevice corrosion in high-temperature brines that sometimes attack CP titanium. It also has better resistance to oxidizing environments, such as nitric acid. The alloy resists corrosion in reducing environments, such as HCl and H2SO4, better than CP titanium but not as well as the titanium-palladium alloy. Surface Treatment. Precious metals, such as platinum and palladium, have been ion plated, ion implanted, or thermal diffused into titanium alloy surfaces to achieve improved resistance to reducing acids. This approach has not been used commercially for industrial components because of high cost, coating application limitations, and the limitations (mechanical and corrosion damage) normally associated with very thin surface films. However, ion-plated platinum or gold surface films also impart significant improvements in titanium alloy oxidation resistance at temperatures up to 650 °C (1200 °F). Protective thermal oxide films can form when titanium is heated in air at temperatures of 600 to 800 °C (1110–1470 °F) for 2 to 10 min. The rutile TiO2 film formed measurably improves resistance to dilute reducing acids as well as absorption of hydrogen under cathodic

Corrosion Resistance / 127 charging or gaseous hydrogen conditions. Corrosion studies in hot, dilute HCl solutions have confirmed the superior protective benefits of a rutile TiO2 film compared with as-pickled, polished, or anodized surfaces on unalloyed titanium. Corrosion and hydrogen uptake resistance was afforded by thermal oxidation in molten urea at 200 °C (390 °F). Enhanced protection from dry chlorine attack can also be expected. As in the case of anodizing, thermal oxidation offers no improvements in titanium resistance to highly alkaline or oxidizing aqueous media. Surface films of titanium nitrides and carbides are highly resistant to reducing acids. Studies have shown that the dense adherent nitride films produced by reactive plasma ion plating provide superior protection in deaerated H2SO4 solutions when compared with several other film-forming methods. Methods of applying nitride surface films to titanium include ion implantation. Because of the cost and limitations of film application and the inherent thin film performance limitations, these films are generally not used solely for corrosion resistance. The improved wear resistance offered by these hard films is generally the primary incentive for application. General Corrosion Improvement Efforts. Methods of expanding the corrosion resistance of titanium into reducing environments include:

can diffuse into the crevice from the bulk solution. As a result, the corrosion potential of metal in the crevice becomes more electronegative than the potential of metal exposed to the bulk solution. Metal in the crevice acts as the anode and dissolves under the influence of the resulting galvanic current. This produces an excess of positive ions at the anode that is balanced by the migration of chloride ions into the crevice. The titanium chlorides formed in the crevice are unstable and tend to hydrolyze, forming small amounts of HCl. This reaction is very slow at first, but in the very restricted volume of the crevice it can reduce the pH to values as low as 1, which reduces the potential still further until corrosion becomes severe. Although crevice corrosion of titanium is observed most often in hot chloride solutions, it also occurs in iodide, bromide, and sulfate solutions. Susceptibility increases with increasing temperature, increasing concentration of chloride ions, decreasing concentration of dissolved oxygen, and decreasing pH. In solutions with neutral pH, crevice corrosion of titanium has not been observed at temperatures below 120 °C (250 °F) but, at lower pH values, crevice corrosion sometimes is encountered below this temperature. Iron-Induced Crevice Corrosion. Although frequently interpreted as a pitting phenomenon, smeared surface iron pitting of unal-

• Increasing the surface oxide film thickness by anodizing or thermal oxidation

• Applying precious metal (or certain metal oxide, carbide, or nitride) surface coatings

• Alloying titanium with certain elements • Adding oxidizing species (inhibitors) to the reducing environment to permit oxide film stabilization

Of these methods, the last two have been very practical, effective, and most widely used in actual service. Separately deposited coatings and anodizing/thermal oxidation have not proved particularly practical. One problem with coatings and artificially induced surface films in addition to high cost is that they are not regenerated if they are removed by corrosion, erosion, or wear during service.

Localized Corrosion Processes Crevice Corrosion. Crevices can stem from adhering process stream deposits or scales, metal-to-metal joints (for example, poor weld joint design on tube-to-tube sheet joints), and gasket-to-metal flanges and other seal joints. The mechanism for crevice corrosion of titanium is similar to the process for stainless steels in which oxygen-depleted reducing acid conditions develop within tight crevices (Fig. 13.3). Titanium is subject to crevice corrosion in brine solutions containing oxygen because the oxygen in the crevice is consumed faster than it

Fig. 13.3

Schematic of crevice corrosion mechanism

loyed titanium in hot brines appears to be a special case of crevice corrosion. It results when iron, carbon steel, or low-alloy steel is gouged, scratched, smeared, and embedded into a titanium surface, breaching the titanium oxide film. During hot brine exposure (80 °C, or 175 °F), the embedded iron can either corrode off the surface and permit repassivation or develop local acidic conditions if occluded by titanium metal smears or laps in the titanium. Localized attack initiated by this mechanism creates a very characteristic circular pit morphology and can involve local hydrogen absorption. During fabrication and installation of titanium equipment, the titanium must be handled with enough care to avoid contaminating it with embedded iron particles. Pitting failures of titanium tubing have been traced to scratches in which traces of iron were detected; the failures were attributed to smearing of iron particles into the passive film of TiO2 until the particles had penetrated the film. The difference in corrosion potential between low-carbon steel and unalloyed titanium is nearly 0.5 V in saturated brine at temperatures near the boiling point. This difference is sufficient to establish an electrochemical cell in which the iron is consumed at the anode. Before the iron is completely consumed, however, a pit begins to grow in the titanium. Once the pit becomes established, acid conditions de-

128 / Titanium: A Technical Guide velop in it. These conditions prevent the passive film from reforming, and corrosion continues until the titanium is perforated. Pit initiation has not been observed with copper, nickel, or austenitic stainless steel alloys smeared into titanium surfaces. Titanium grades 7 and 12 appear to be much more resistant to this form of localized attack. Enhancing Crevice Corrosion Resistance. Several effective strategies for preventing titanium alloy crevice corrosion and smeared iron pitting are alloying titanium, precious metal surface treatments, metallic coatings, thermal oxidation, noble alloy contact, and surface pickling (for smeared surface iron). In all cases, the basic remedy aims at maintaining creviced metal surfaces at noble potentials sufficient enough to maintain titanium alloy passivity. Pitting corrosion is a form of localized corrosion closely related to crevice corrosion. Both are observed mainly on passive metals, such as aluminum, stainless steels, and titanium. Pitting initiates at imperfections in the oxide film. Aggressive ions such as Cl– concentrate at these sites until they are able to displace the oxygen in the passive film. A small crevice is soon formed by an insoluble corrosion product, TiO2, which fills and covers the pit, thus restricting diffusion into the growing pit and permitting acid conditions to develop. Erosion-Corrosion and Cavitation. For most materials, there are critical velocities beyond which protective films are swept away and accelerated corrosion attack occurs. This accelerated attack is known as erosion-corrosion. The critical velocity differs greatly from one material to another and can be as low as 0.6 to 0.9 m/sec (2–3 ft/sec). For titanium, the critical velocity in seawater is high—more than 27 m/sec (90 ft/sec). Numerous erosion-corrosion tests have shown titanium to have outstanding resistance to this form of attack. Erosion-corrosion can be greatly aggravated by the presence of abrasive particles (such as sand) in a flowing fluid. Titanium exhibits superior resistance to this type of attack in seawater containing fine sand that flowed through conventional titanium condenser tubes at 1.8 m/sec (6 ft/sec). Cavitation is a phenomenon that occurs in flowing liquids wherein the relative motion between the liquid and a surface across which it flows is great enough to locally reduce the pressure below the vapor pressure of the liquid. At the reduced pressure, bubbles form in the liquid. When the liquid containing cavitation bubbles flows into a region of higher pressure, the bubbles collapse, inflicting severe, highly localized forces on the surface against which they collapse. This can produce deep, rounded pits in the surface of almost any solid. Cavitation resistance tests performed in seawater proved titanium to be one of the metals most resistant to this type of damage.

Hydrogen in Titanium Hydrogen Damage. Titanium alloys are widely used in hydrogen-containing environments and under conditions in which galvanic couples or cathodic charging (impressed current) causes hydrogen to be reduced on metal surfaces. In most cases, these alloys display excellent resistance to damage. Hydrogen can be supplied by a number of sources, including water vapor, pickling acids, and hydrocarbons. The amount of absorption depends primarily on the titanium oxide film on the metal surface; an adherent unbroken film can significantly retard hydrogen absorption. Alpha and alpha-beta titanium alloys suffer hydrogen damage primarily by hydride phase formation. Pure alpha titanium is relatively unaffected by small concentrations (<200 ppm) of hydrogen; however, the purity of the alpha titanium is important to its behavior in hydrogen. CP titanium is much more sensitive to hydrogen than is pure titanium. The amount of hydrogen necessary to induce ductile-to-brittle transition behavior in CP titanium is much less than one-half the amount needed in pure titanium. Severe embrittlement can occur in the commercial grades at hydrogen levels as low as 30 to 40 ppm in the presence of a high residual stress or a stress raiser and elevated temperature. These conditions induce migration of the hydrogen to the stress raiser, resulting in a much higher local concentration of hydrogen and the precipitation of hydrides, which can lead to failure. Beta titanium alloys have a very high solubility for hydrogen such that embrittlement is generally not a result of hydriding. Significant losses in ductility or formability may not occur below levels of several thousand parts per million of hydrogen. The tolerance to hydrogen decreases somewhat in the aged (high-strength) condition. This increased tolerance of the beta alloys must be weighed against the significantly higher hydrogen uptake rates that result from the much larger hydrogen diffusion coefficient for beta titanium. Hydrogen Damage Failures. Most metals and alloys are susceptible to hydrogen damage, and many are susceptible to more than one type of hydrogen damage. As noted, titanium and its alloys become embrittled by hydrogen at concentrations that produce a hydride phase in the matrix. The exact level of hydrogen at which a separate hydride phase is formed depends on the composition of the alloy and the previous metallurgical history. In commercial, unalloyed material, this hydride phase is normally found at levels of 150 ppm of hydrogen; however, hydride formation has been observed at levels as low as 30 or 40 ppm of hydrogen, as noted previously. At temperatures near the boiling point of water, the diffusion rate of hydrogen into the metal is relatively slow, and the thickness of the layer of titanium hydride formed on the surface rarely exceeds about 0.4 mm (0.015 in.)

because spalling takes place when the hydride layer reaches thicknesses in this range. Hydride particles form much more rapidly at temperatures above approximately 250 °C (480 °F) due to the decrease in hydrogen solubility within the titanium lattice. Under these conditions, surface spalling does not occur; the formation of hydride particles through the entire thickness of the metal results in complete embrittlement and high susceptibility to failure. This type of embrittlement is often seen in material that has absorbed excess hydrogen at elevated temperatures—such as during heat treatment or welding—and subsequently has formed hydride particles during cooling. There have been instances of localized formation of hydrides in environments where titanium has otherwise performed well. Investigations of such instances suggest that the formation is the result of impurities in the metal (particularly the iron content) and the amount of surface contamination introduced during fabrication. There is a strong link between surface iron contamination and formation of hydrides of titanium. Severe hydride formation has been noted in high-pressure, dry, gaseous hydrogen around particles of iron present on the surface. Anodizing in a 10% ammonium sulfate solution removes surface contamination and leads to thickening of the normal oxide film. In chemical plant service, where temperatures are such that hydrogen can diffuse into the metal if the protective oxide film is destroyed, severe embrittlement can occur. For example, in highly reducing acids where the titanium oxide film is unstable, hydrides can form rapidly. Hydrogen pickup also has been noted under high-velocity conditions where the protective film erodes away as rapidly as it forms. Hydrogen contents of 100 to 200 ppm can cause severe losses in tensile ductility and notched tensile strength in titanium alloys, and they can even cause brittle, delayed failure under sustained loading conditions. The sensitivity to hydrogen embrittlement from formation of hydrides varies with alloy composition and is reduced substantially by alloying with aluminum. Care should be taken to minimize hydrogen pickup during fabrication. Welding operations generally require inert gas shielding to minimize hydrogen pickup.

Stress-Corrosion Cracking Stress-corrosion cracking (SCC) is a fracture, or cracking, phenomenon caused by the combined action of tensile stress, a susceptible alloy, and a specific corrosive environment. The metal can show little evidence of general corrosion attack, although slight localized attack in the form of pitting or crevice corrosion may be visible. Usually, only specific combinations of metallurgical and environmental conditions cause SCC. This is important because it is often possible to eliminate or reduce SCC sen-

Corrosion Resistance / 129 sitivity by modifying either the metallurgical characteristics of the metal or the makeup of the environment. Another important characteristic of SCC is the requirement that tensile stress be present. These stresses can be provided by cold work, residual stresses from fabrication, or externally applied loads. Mechanism of Stress-Corrosion Cracking. Over the years, a variety of mechanisms or models have been proposed to explain SCC phenomena in titanium alloys. In general, lower-temperature SCC is the anodic dissolution of atoms in highly localized areas that, aided by an applied tensile stress, propagates cracks into the metal. Crack advance occurs by discontinuous rupture of the oxide film at the crack tip. SCC generally begins from a corrosion pit or a crevice. In the presence of a tensile stress, the pit will produce a crack if corrosion is not rapid enough to blunt the advancing crack tip. Once a crack initiates, the balance among the crack tip corrosion rate, the crack tip environment, and the repassivation kinetics is critical to either continued crack propagation or crack arrest. The mechanism varies slightly for hot salt stress-corrosion cracking (HSSCC). It is generally agreed that HSSCC stems from pyrohydrolytic formation of a hydrogen halide from its corresponding halide salt. This halide subsequently attacks the metal producing titanium chloride corrosion products and atomic hydrogen. This hydrogen diffuses into the metal under stress, causing local embrittlement and incremental crack growth. Chemistry and Processing. In alpha titanium alloys, SCC behavior primarily depends on composition. The SCC behavior is especially sensitive to aluminum and oxygen content. In alpha-beta alloys it is also still the alpha phase that exhibits SCC susceptibility. Increased alpha stabilizers tend to promote SCC, while increased beta stabilizers tend to reduce or eliminate SCC susceptibility. Unalloyed titanium generally is immune to SCC unless it has a high oxygen content (0.3% or more). It is important to distinguish between the two classes of titanium alloys. The first class, which includes ASTM grades 1, 2, 7, 11, and 12, is immune to SCC except in a few specific environments. These specific environments include anhydrous methanol/halide solutions, nitrogen tetroxide, red fuming nitric acid, and liquid or solid cadmium. For this reason, stress-corrosion cracking is of little concern in the chemical process industries where unalloyed titanium is most commonly used. On the other hand, the second class of titanium alloys, including the aerospace titanium alloys, are subject to stress-corrosion cracking. The susceptibility has been found for several additional environments beyond those listed above—most notably aqueous chloride solutions and hot salts. However, this susceptibility is often associated with high stress concentrations typical of laboratory testing with loaded, precracked specimens, and generally is not ob-

served with smooth specimens. Field stress-corrosion failures are rare to nonexistent. One of the most important variables affecting susceptibility to SCC is alloy composition. Aluminum additions increase susceptibility to SCC; alloys containing more than 6% Al generally are susceptible to stress corrosion. The role of aluminum has been related to the formation of the intermetallic phase, Ti3Al (also known as alpha-2). The more Ti3Al in the microstructure, the greater the SCC potential, particularly in the case of HSSCC. Additions of tin, manganese, and cobalt are detrimental to SCC, whereas zirconium appears to be neutral. Beta stabilizers, such as molybdenum, vanadium, and niobium, are beneficial. Susceptibility to SCC also can be affected by processing. Studies on near-alpha and alpha-beta titanium alloys showed that beta processing to produce Widmanstätten structures can be beneficial to HSSCC resistance. Other properties are affected by beta processing and the best processing (e.g., forging, heat treatment) for an application may not produce optimum HSSCC resistance. Because the incidence of service failures is minuscule, processing solely to increase HSSCC resistance is not normally considered. A number of environments in which some titanium alloys are susceptible to SCC, along with the temperatures at which cracking has been observed, are listed in Table 13.4. Some of these environments are discussed in the following sections. Hot, Dry Chloride Salts. HSSCC of titanium alloys is a function of temperature, stress, and time of exposure. In general, hot salt cracking has not been encountered at temperatures below approximately 260 °C (500 °F). The greatest susceptibility occurs at approximately 290 to 425 °C (550–800 °F) based on laboratory tests. Time to failure decreases as either temperature or stress level is increased. All commercial alloys (but not unalloyed titanium) have some degree of susceptibility to hot salt cracking. Residual salts cause surface pitting and even cracking of certain alloys under high tensile loads. Although rarely encountered in service, cracking of titanium parts due to hot salt corrosion has been encountered by fabricators during stress relieving operations. Responsibility was traced to vapors of chlorinated cleaning fluids that were not completely removed prior to ther-

mal processing, chloride traces from other process fluids (including tap water), and even to salt residues from fingerprints. Since the original finding that hot halogenated salts can damage titanium, the phenomenon has been studied extensively. Although much has been learned about the reaction, relative susceptibility, and related variables, it is generally agreed that laboratory tests do not simulate service conditions well and thus do not correctly predict field performance. The extent of damage by salts is directly related to temperature exposure time and level of tensile stress. Processing history, alloy composition, salt composition, and other environmental conditions also have important effects. Susceptibility to hot salt corrosion appears to be influenced considerably by processing and alloy additions. Therefore, control of these factors should make it possible to avoid the phenomenon in service. An unusual source of HSSCC was the breakdown of a halide-containing gasket. Its constituents were trapped in a crevice of sorts on an adjacent titanium part where the subsequent heat, stress, and halide ion concentration produced a crack, though not a total fracture of the part. HSSCC has been associated with use of silver as an antigallant for titanium because silver has an affinity for chloride ions. Despite the ordinary resistance of titanium to in-service, low-salt SCC failure, the silver caused HSSCC to occur by trapping chloride ions as AgCl2 and altering the environment seen by the titanium alloy. Silver is no longer used in this application, yet the experience suggests that field failures are possible under certain conditions. Silver can participate in liquid metal embrittlement, which is discussed later in this Chapter. Figure 13.4 and Tables 13.5 and 13.6 show some of the characteristic behavior of selected titanium alloys in HSSCC. Chlorine, Hydrogen Chloride, and Hydrochloric Acid. With respect to environments containing chlorine, hydrogen chloride, or hydrochloric acid, it appears that both oxygen and water must also be present for cracking to occur. Nitrogen tetroxide (N2O4) containing small amounts of dissolved oxygen causes cracking of titanium and some titanium alloys. No cracking occurs if the nitrogen tetroxide contains a

Table 13.4 Environments and temperatures that can be conducive to stress-corrosion cracking of titanium alloys Environment Hot dry chloride salts Seawater, distilled water, and aqueous solutions Nitric acid, red fuming Nitrogen tetroxide Methanol, ethanol Chlorine Hydrogen chloride Hydrochloric acid, 10% Trichloroethylene Trichlorofluoroethane Chlorinated diphenyl

Temperature

260–480 °C (500–900 °F) Ambient Ambient Ambient to 75 °C (165 °F) Ambient Elevated Elevated Ambient to 40 °C (105 °F) Elevated Elevated Elevated

130 / Titanium: A Technical Guide Table 13.5 Hot salt stress-corrosion cracking threshold stress levels for selected titanium alloys after 100 h exposure Threshold stress, MPa (ksi) Alloy

Condition

Unalloyed Ti Ti-4Al-3Mo-1V Ti-6Al-4V Ti-5Al-2.5Sn Ti-8Al-1Mo-1V

Annealed Aged Annealed Annealed Annealed

288 °C (550 °F) 426 °C (800 °F)

None 579 (84) 345 (50) 193 (28) 172 (25)

None 338 (49) 165 (24) 138 (20) 124 (18)

Table 13.6 Relative susceptibility of selected titanium alloys to hot salt stress corrosion cracking Alloy

Ti-8Al-1Mo-1V Ti-5Al-2.5Sn Ti-13V-11Cr-3Al Ti-6Al-6V-2Sn Ti-6Al-4V Grade 4 Ti-8Mo-8V-2Fe-3Al Ti-11.5Mo-6Zr-4.5Sn Ti-4Al-3Mo-1V Ti-2.25Al-1Mo-11Sn-5Zr-0.25Si Grades 1 and 2 Grades 7 and 11 Grade 9 Grade 12

Susceptibility

High High Intermediate Intermediate Intermediate Intermediate More resistant More resistant More resistant More resistant Immune Immune Immune Immune

small percentage of nitric oxide. The cracking can be transgranular, intergranular, or both, depending on alloy composition. Methyl and ethyl alcohols containing small amounts of water, chloride, bromide, and iodide promote cracking at ambient temperatures. Greater concentrations of water inhibit cracking. Higher alcohols can induce cracking, but to a lesser extent; the longer the chain, the less reactive the alcohol becomes. Accelerated Crack Propagation in Seawater. Titanium is known to be highly resistant to corrosion by seawater. However, for certain alloys, components containing very sharp notches or cracks exhibit accelerated crack propagation and, thus, lose resistance to fracture when exposed to seawater. Failure of titanium due to loss of fracture resistance appears to be similar to delayed fracture of highstrength steels, containing sharp notches or cracks, on exposure to various liquid environments. Exposure to seawater does not appear to diminish service life of titanium alloys, such as

Fig. 13.4

Parametric (Larson-Miller type) relationships for hot salt stress-corrosion cracking of selected titanium alloys

Ti-8Mn and Ti-5Al-2.5Sn, that exhibit this phenomenon in laboratory testing. These two alloys have been employed successfully in aircraft during the past 25 years without reported failures. Apparently, the conditions leading to accelerated crack propagation (primarily, the existence of a crack) have not been encountered in service. Accelerated crack propagation in seawater can be avoided by proper alloy selection. As would be expected, alloys containing more than 6% Al are particularly susceptible. Additions of tin, manganese, cobalt, and oxygen are detrimental, whereas beta stabilizers, such as molybdenum, niobium, and vanadium, tend to reduce or eliminate susceptibility to this phenomenon. Unalloyed titanium is not susceptible unless it contains more than approximately 0.3% O.

Liquid Metal Embrittlement Some titanium alloys crack under tensile stress when in contact with liquid cadmium, mercury, or silver-base brazing alloys. This

type of embrittlement differs from SCC, although there are some similarities. Liquid metal embrittlement appears to result from diffusion along grain boundaries and formation of brittle phases, which in turn produce the loss of ductility. Titanium also can be embrittled by contact with certain solid metals (e.g., cadmium and silver) when the titanium is under tensile stress. The failure mechanism is not completely understood, although many investigators believe it is similar to liquid metal embrittlement. Service failures have occurred in cadmium-plated titanium alloys at temperatures as low as 65 °C (150 °F) and in silver-brazed titanium parts at temperatures above 315 °C (600 °F). Silver-plated components should not be used in contact with titanium under stress at temperatures above 230 °C (450 °F). (Refer to the discussion of HSSCC in the section “Mechanism of Stress-Corrosion Cracking.”) Cadmium-plated parts, such as interference-fit fasteners or press-fit bushings, should not be used in contact with titanium at any temperature. Other cadmium-plated parts and fasteners should not be used in contact with titanium at temperatures above 230 °C (450 °F).

Titanium: A Technical Guide Matthew J. Donachie, Jr., p131-137 DOI:10.1361/tatg2000p131

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Chapter 14

Advanced Alloys and Future Directions Scarcely a half century after their introduction into the technical arena, titanium and its alloys have a wide range of application in many industries, from aerospace to sports. Titanium metallurgy, as it exists today, grew out of the application of titanium to gas turbines. From there, the metal was applied to airframes and then to other sophisticated and critical areas, as well as to more mundane uses that benefit from light weight (low-density), exceptional uncoated corrosion resistance, and good strength. The golf club and the high-speed racing bicycle are examples of uses benefiting from good strength. The record of accomplishment has been remarkable. The future directions of a quarter century ago are now the commonplace materials and applications of this versatile but expensive metal. Cast titanium (see Chapter 6) was thought of as a “future” advance for over a decade before it evolved into an acceptable production technique for critical aerospace component applications. Limitations on Future Advances. The designer or potential user planning to employ titanium should know what can be possible with this metal system. The advanced materials and technologies mentioned in this chapter, for the most part, owe their current status to the support of the United States government. Many initial titanium metallurgy concepts were brought to fruition with government support, including the very early use of the metal in military gas turbines and in supersonic aircraft. Lockheed’s SR-71 supersonic spy plane was the very first use of a beta titanium alloy for structural aerospace applications. It is important to recognize that the developmental costs of many technologies today, as in the past, cannot be exclusively supported by the limited industrial market perceived at the point in time when the technology or application was conceived. Government support (e.g., NASA and the military) for development and use of advanced technologies is critical for increased application of new concepts but may not be adequate (in light of government funding restrictions) to carry the day. Of course, some materi-

als and technologies may just have too much technical risk and, hence, cost and liability risk for any company to employ them in commercial ventures. Thus, interesting concepts now available in a limited way may not make their way into the commercial arena for many years, if ever. A great deal of credit is due to those original titanium producing companies that expended so many research and development dollars in alloy development projects. Commercial applications of titanium, in most cases, have tracked military developments. The requirements of the steam turbine, chemical, automotive, biomedical, and sports industries (as well as others) have been secondary causes contributing to the enrichment of the technological base of titanium. Realistically speaking, however, materials such as titanium aluminides and titanium matrix composites or technologies such as powder metallurgy have been, and will continue to be, spurred by military requirements. The preceding discussion pertains to advanced alloy and process development. It should not be inferred that conventional alloy development is stagnent. In the biomedical industry, the increased use of prosthetics has encouraged producers not only to supply the conventional pure titanium and Ti-6Al-4V for use by biomedical device companies but also to develop and/or market more aggressively newer alloys, such as Ti-6Al-7Nb and Ti-15Mo-3Nb. The claim of titanium to the biomedical market lies in its lower modulus (relative to cobalt-chromium alloys used for prosthetics), high strength, and remarkable biocompatibility. Applications for titanium and its alloys range from dental implants to femoral prostheses and knee replacements to facio-maxillary bone plates. Biomedical applications should see continued growth and the potential introduction of additional alloys. Advanced Titanium Alloys and Processing. As previously noted, the current temperature limit of conventionally processed wrought and cast titanium alloys is about 595 °C (1100 °F). This limit is due mainly to long-term surface and bulk metallurgical stabil-

ity problems, though creep strength obviously decreases continuously with temperature. In order to improve this limit to 700 °C (1290 °F) and above, titanium matrix composites and titanium-aluminide intermetallic alloys have been developed. Other advanced compositions have been studied through the use of high-technology rapid-solidification rate (RSR) powder metallurgy processing and mechanical alloying. In addition to these advances in alloy development, other interesting aspects of titanium use are evolving. Spray processing of powder to create preforms, wider use of superplastic forming, and physical vapor deposition (PVD) are several areas that promise to enhance titanium applications.

Titanium Aluminides With the temperature limitations on conventional titanium alloys, superalloys are required in the higher-temperature regions of gas turbines and other aerospace structures. Replacement of the superalloys in later stages of gas turbine hot sections, for example, could lead to significant weight reductions. In the low-pressure turbine (LPT), as engine thrust increases the turbine blades become bigger, causing both the disk that holds the blades and the shaft that turns with the disk to become heavier. Replacement of conventional nickel-base superalloys with titanium aluminides would alleviate this engine weight-increase problem. For reasons such as this, extensive research and development has been carried out for over three decades to answer this question: can ductile titanium-aluminide intermetallic compounds be made that will compete with the nickel-base superalloys? Aluminide Compositions and Properties. New classes of materials based on titanium-aluminide intermetallic compounds have been developed. There initially were two candidates for aluminide intermetallic bases: alpha-2 (Ti3Al) and gamma (TiAl). They were followed

132 / Titanium: A Technical Guide by a third, Ti2AlNb-base orthorhombic intermetallics. These materials have essentially the same density as titanium, but can be used at much higher temperatures. They also have high melting temperatures and moduli, and they retain their modulus better with temperature. The titanium aluminides have higher moduli at 816 °C (1500 °F) than titanium does at room temperature! Aluminides probably will have even better strength retention at higher temperatures than is currently available with conventional titanium alloys. Aluminides are characterized by the tendency to form TiO2 rather than the more protective Al2O3 that characterizes the most oxidation-resistant superalloys. Consequently, aluminides have excellent intrinsic oxidation resistance at lower temperatures, but there is a real limiting tendency for the oxide scales formed on these aluminides at temperatures above 871 °C (1600 °F) to spall on cooling. The key to expanding the maximum use temperature of titanium aluminides is to enhance their oxidation resistance while maintaining adequate levels of creep and strength retention at elevated temperatures. The potential service temperatures for the titanium aluminides currently are expected to range from 600 to 760 °C (1110–1400 °F). The gamma class of aluminides offers more oxidation resistance than alpha-2 alloys. Although alloy developments were tried to further increase the oxidation resistance of gamma alloys, the greatest benefits for titanium aluminides of all types seems to lie in the development of suitable protective coatings. Three general coating alloy approaches have been taken for protecting titanium aluminides: aluminizing, metal-chromium-aluminum-yttrium overlay coatings and silicides/ceramics. The former two approaches are adaptations of coating technology developed for superalloys while the latter approach is adapted from technology for refractory metal alloys. Protection of titanium aluminides under oxidizing conditions has been achieved with all three approaches;

however, the fatigue life of coated material is often less than that of uncoated material. The alpha-2 alloys typically contain 23 to 25 at.% Al and 11 to 18 at.% Nb. Other alloying elements include up to 3 at.% V and approximately 1.0 at.% Mo. The gamma alloys contain 48 to 54 at.% Al and 1 to 10 at.% of one of the following: vanadium, chromium, manganese, niobium, tantalum, tungsten, or molybdenum. The orthorhombics typically contain 21 to 25 at.% Al and 25 to 30 at.% Nb. Aluminides have low ductility at ambient temperatures, although the elevated-temperature ductility generally is satisfactory. For processing and service installation and refurbishment, though, low ductility at ambient temperatures can present a problem. Creep and other high-temperature properties are good, although not necessarily at the levels expected in the early years of development of aluminides. Figure 14.1 gives a comparison of the creep behavior of conventional titanium alloys and the alpha-2 and gamma titanium aluminides. Strength property levels expected for alpha-2 and gamma in the early years of development were intended to be comparable to Inconel 713 and IN-100 nickel-base superalloys, respectively. These were ambitious goals that were not truly realized. For low-end high-temperature applications up to approximately 649 °C (1200 °F), titanium alloys might also hope to compete with the gas turbine industry standard static-application alloy, Inconel 718. Although alpha-2 alloys did not adequately meet the standard, the orthorhombic intermetallic alloys show promise of reaching the Inconel 718 goal. Figure 14.2 compares several orthorhombic titanium intermetallics with Alloy 718 and some alpha-2 alloys. For full utilization of mechanical property capabilities of alpha-2 and gamma titanium aluminides, compositions must be optimized and control of microstructure must be maintained. Thermomechanical processing can be used to control the phase morphology and distribution in the wrought aluminides. Cast alloys

must rely on heat treatment for microstructural adjustments to a specific composition. Processing and Application. Melting, casting, forging, rolling and bonding of titanium aluminides have been extensively studied. Other processing technologies, such as machining, have not been neglected. Alloys can be processed by conventional methods, including casting, ingot metallurgy, and powder metallurgy. Precision investment castings have been made from an alpha-2 base alloy, and a ring for a combustor liner was rolled successfully from it. In one instance, a rolled ring of this type of alloy was made into a compressor case component and successfully ran for 65 h. Other components for high-temperature use have been made and tested. The weight savings in one application alone amounted to 43% when compared with the more conventional superalloy commonly used. As gamma aluminides emerged from the wide-composition group of titanium intermetallics, cast Ti-48Al-2Cr-2Nb alloy was extensively evaluated for use in commercial gas turbine engines. Figure 14.3 shows the cast alloy in the form of low-pressure turbine (LPT) blades for high-bypass ratio, high-thrust commercial gas turbine engines. Figure 14.4 shows a rotor with cast LPT blades of Ti-48Al-2Cr2Nb that were tested uncoated at 700 °C (1292 °F) in a General Electric simulation engine. Larger cast structures are more difficult to produce due to the need to hot isostatically press the cast structure for optimum properties. It is claimed that cast Ti-48Al-2Cr-2Nb alloy can be welded by the gas-tungsten arc welding process and by electron beam welding. By casting large structures in segments, hot isostatic pressing, and repair welding them, then joining the segments by welding, it has been indicated that cast aluminide technology can be extended to more massive sections of commercial and military gas turbines.

2.5

Yield strength/density, 105 m2/sec2

Ti-22Al-27Nb (O + βo) 2.0

Ti-24.5Al-23.5Nb (O + βo)

1.5 Ti-24Al-17Nb-1Mo (α2) Alloy 718 1.0 Ti-25Al-10Nb-3V-1Mo (α2) 0.5

Ti-24Al-11Nb (α2)

200

Comparison of the creep behavior of titanium aluminides with conventional titanium alloys

800

Strength-to-weight ratio comparison for orthorhombic and alpha-2 titanium intermetallics with superalloy Inconel Alloy 718

Fig. 14.2

Fig. 14.1

400 600 Temperature, °C

Advanced Alloys and Future Directions / 133

Fig. 14.3

Cast low-pressure turbine gamma aluminide blades for General Electric gas turbine engines. (a) Crude shape for CFC-80C. (b) Cast-to-size blade for GE90

A number of gas turbine engine components have been identified as potential applications for the gamma alloy technology described above. These include stationary and rotating high-pressure compressor (HPC) blades, stators, vanes, cases, stationary components (such as diffuser cases), turbine components (such as cases), and LPT blades. Automotive applications have been sought for titanium aluminides and demonstration cast and wrought components have been made. It is claimed that wrought gamma alloys show the better balance of mechanical properties with processing capability. The Future of Aluminides. One may wonder why aluminide-base materials are not already in use. The answer is found in the general tendency of many metal aluminides in all types of systems to have limited room-temperature ductility and poor fracture toughness. Aluminides are difficult to process and fabricate into structural components because of their limited ductility and toughness at lower temperature ranges; therefore, they require very high processing temperatures. These drawbacks are significant when working aluminides into product forms that require a large amount of deforma-

Low-pressure turbine rotor with cast gamma aluminide alloy blades after rigorous test in General Electric gas turbine

tion, such as sheet for honeycomb-panel or trusspanel cores in aircraft and/or aerospace structures. Titanium aluminides are expensive compositions to make. Cost reductions have been claimed for gamma alloys used for casting that will take the basic alloy (precasting) cost down to the range of conventional alloys. It is not clear if these cost reductions will materialize because they are predicated not just on technical improvements and a broadening of the specification requirements but also on volume of use. Titanium aluminides still represent a questionable technical application (properties, processing) and are not likely to be widely applied in the near future.

Titanium Matrix Composites Titanium matrix composite (TMC) materials are conventional titanium alloys strengthened by a reinforcement of continuous fibers. Composite material concepts have been explored for close to four decades using polymer matrices and metal matrices with some success, but have

not particularly been explored for titanium matrix composites. The very high stiffness and strength of fibers that can be used in TMC means that a titanium composite could be almost twice as stiff as conventional titanium, actually exceeding the stiffness of steel and half again as strong as the conventional titaniumbase alloy. The continued pressure for increased performance of aircraft and aircraft engines has led to research and development studies on titanium matrix composite materials. These materials are considered a possible future option for key applications, particularly in civil gas turbines. During the middle of the 1990s, the three major gas turbine manufacturers (Pratt & Whitney, General Electric, and Rolls Royce) initiated significant efforts to decrease costs and increase quality and performance of TMC materials in gas turbine engines. TMC materials are not restricted to continuous fibers. Short fibers and whiskers or other ceramic particulates have been considered for reinforcements of titanium matrices. Titanium matrix composite materials are strengthened generally by a reinforcement of continuous fibers of silicon carbide (SiC). These composite materials have been developed to extend the elevated-temperature performance of titanium and its alloys. Matrix materials used to date include Ti-6Al-4V, Ti-15V-3Sn-3Cr-3Al, and Beta 21S (Ti-3Al-8V-6Cr-4Mo-4Zr). Beta 21S can withstand temperatures as high as 800 °C (1500 °F) when reinforced with SiC. Silicon carbide fibers generally constitute 35 to 40 vol% of the composite. Particulate-reinforced titanium matrix composites, representing discrete, noncontinuous reinforcement, are another source of composite material strengthening. This family of materials includes a choice of several ceramic or intermetallic additions (e.g., TiC, TiB2, or TiAl) at various loading levels (e.g., 10–20 wt%) in a select titanium alloy matrix, such as Ti-6Al-4V. Titanium-aluminide materials also have been employed in ongoing efforts to produce TMC materials. One particulate-reinforced application consisted of producing a gamma titanium aluminide reinforced by 7 vol% of TiB2 particles. The particles were introduced to the

Fig. 14.4

Fig. 14.5

Investment cast, hot isostatically pressed, and heat treated particulate-reinforced aluminide missile fin

134 / Titanium: A Technical Guide matrix in the original vacuum arc remelting process of creating the gamma alloy chemistry. The TMC was cast, hot isostatically pressed, and heat treated to produce a part (Fig. 14.5). Processing Options. Although matrix-fiber compatibility and resulting strength, ductility, and durability are always of concern in creating TMC materials, the principal barrier to their application is the processing necessary to create parts of TMC. Silicon carbide fibers are not capable of being formed around sharp radii. In addition, handling of individual fiber strands is not practical. Consequently, TMC materials that are continuous fiber-reinforced are most easily manufactured into comparatively simple geometry parts where the stress field also is relatively simple. A key to the performance of any part made of TMC material is good control of possible microstructural defects. A material with 35 vol% of a relatively brittle second phase offers significant potential for introducing defects and flaws. Cracked fibers and local matrix cracks are potential problems. These problems purportedly have been overcome by the current processes of coating fibers with a titanium matrix material before lay-up and consolidation. Composite materials by nature tend to be batch-process oriented and often require labor-intensive lay-up of prepared tapes to produce the desired part dimensions. Tapes are important as a way to provide for a consistent dispersion of the fibers in the matrix. Tapes greatly simplify the handling and lay-up processes. For continuous fiber reinforcement schemes, plasma spraying or electron beam physical vapor deposition has been used to deposit a titanium matrix onto fibers. The fibers can be used directly for lay-up or combined to form a high-density tape product. Other processes are available to deposit powder of the desired titanium matrix on the fibers to create a tape product. A number of processing techniques have been evaluated to consolidate continuously reinforced titanium composites, but only high-temperature/short-time roll bonding, hot isostatic pressing, and vacuum hot pressing have been used to any substantial degree. Particulate-reinforced titanium matrix composites are produced by powder metallurgy processing. These materials are processed to near-net shape by cold isostatic pressing and can be further consolidated and/or refined by forging or extrusion of the powder preform. Compared with titanium alloys that are not reinforced, particulate-reinforced materials offer improved tensile strength and elastic modulus, both at room and elevated temperature, thereby increasing the use temperature at approximately the same density. The Future of Titanium Matrix Composites. Interesting work has been done on TMC materials and extensive efforts funded by government and industry continue. The particulate-reinforced part shown in Fig. 14.5 offers strong evidence of what might be accom-

plished. The TMC part was half the density of the stainless component it replaced and was stronger at operating temperatures. While this project demonstrated feasibility for a singular application, the application was a single-use one. So, although two advanced material concepts (aluminides and composites) were used, military or even commercial repeat use is not a near-term possibility. The cost of TMC is heavily driven by the fiber cost as well as the actual component lay-up and consolidation costs. Costs of fiber are high due to relatively low volume. It may be possible to reduce fiber cost, but there is still the cost of coating the fiber and producing tapes to consider. Cost of production, consistency of product properties, oxidation resistance of fibers and matrices, and repairability are major concerns in the application of TMC materials. It is unlikely that these materials will be useful for any standard commercial applications for many years to come and may never be cost-effective substitutes for other metallic components.

Other Process Techniques Superplastic forming/diffusion bonding (SPFDB) was discussed briefly in Chapter 9. For designs that use reinforced sheet components of the honeycomb type, or for similar applications, the opportunity to combine forming and bonding operations by the SPFDB technique has become a viable manufacturing technique. Structures that can be accessed internally by gas under pressure are conceptually all that are required to create a complex structure containing ribs, doublers, or other reinforcement. Designers should give serious consideration to the application of SPFDB techniques to new construction. The fact that major aircraft engine manufacturers will use SPFDB to create critical rotating parts, such as hollow fan blades for large gas turbines, suggests that the technology could be considered acceptable for virtually any application using conventional titanium alloy compositions. Cost may still be a problem depending on how critical the component application is. Large structures require large furnaces, and the diffusion bonding aspect of the process is critically dependent on cleanliness and lay-up of mating components. Spray Forming and Laser Forming. One of the most important considerations in producing titanium powder metallurgy components is oxygen content. Near-net shape processing by powder methods continues to be a goal for titanium alloys. Various spray forming techniques have been advanced as methods to create a given shape directly without a die or a can, such as those used in hot isostatic pressing. The part is built up by successive continuous deposition of powder by spraying. Spray techniques have included thermal spray, the Osprey process, and low-pressure plasma spray. Despite

the best precautions, these processes typically introduce supplementary oxygen that adversely affects the properties of the sprayed component. Solid-state spray forming (SSF) has been introduced as another approach beyond those previously considered. The SSF process uses oxide-free titanium powder produced by the hydride-dehydride (HDH) process and is a low-temperature deposition operation. The essence of the SSF process is reported to be the use of the special HDH-produced powders and the high-speed collisions of these powder particles produced by the SSF accelerator. The result is said to produce instant solid-state bonding. Initial work on SSF (with powders that are not oxide-free) required subsequent annealing and hot isostatic pressing for completion of component fabrication processes. Spray processes have interesting potential but are unlikely to be particularly cost-effective. Powder costs are a significant item in the production process. Furthermore, it is uncertain that non-symmetrical articles can be produced with the same level of properties throughout as symmetrical articles. Other processes related to SSF have been reported. The cold-gas spray method (CGSM) has been claimed to have promise for low-temperature deposition of coatings or to build up “billets” of titanium alloys. The CGSM is claimed also to have benefits in health, safety, and environmental aspects compared with traditional high-temperature spraying processes. It has been suggested that CGSM can be used to effect repairs on titanium components without causing any damage to the substrate material. Despite the claims for these low-temperature processes, it is likely that the economic aspects of powder spraying will make such processes marginal in the production of titanium alloy components. A related process is the laser forming of titanium components, which is claimed to reduce lead times for the fabrication of complex titanium structures by 50 to 75%. Lasform is the name for a direct metal deposition process that combines high-power laser cladding technologies with advanced rapid prototyping methods to directly manufacture three-dimensional components. The approach is similar to rapid prototyping techniques, such as stereolithography and selective laser sintering. However, it is different in that a fully dense, high-integrity part is claimed to be made without the use of intermediate processing steps such as casting or hot isostatic pressing. A laser provides the power necessary to transfer the selected titanium alloy powder to the form where it is deposited. The process is accomplished in a large oxygen-free inert gas atmosphere. The lasform process, as in all net-shape processing, claims to reduce machining steps and material waste. Properties of a lasformed Ti-6Al-4V alloy are shown in Table 14.1. One interesting suggestion for laser forming is the selective deposition of varying alloy chemistries to optimize mechanical properties for specific locations on a part. Comments about the other powder spray forming pro-

Advanced Alloys and Future Directions / 135 Table 14.1 Mechanical properties of lasformed alpha-beta titanium alloy Ti-6A1-4V Property

Ultimate tensile strength(a) Yield strength(a) Elongation(a)(b) Reduction in area(a) Fracture toughness(c) Charpy impact strength(a) Hardness(d)

Value

1030 MPa (150 ksi) 900 MPa (130 ksi) 12.3% 23.5% 90 MPa m (81.5 ksi in.) 19 J (14 ft · lbf) 36 HRC

(a) Laser formed + vacuum mill anneal + sub beta transus + solution treat and age. (b) 25 mm (1 in.) gage length. (c) Laser formed + vacuum mill anneal + supra beta transus + solution treat and age. (d) Laser formed + vacuum mill anneal

cesses apply here as well. It may be difficult to prove that mechanical properties are equivalent to those of forged or even cast titanium alloys, and the economics of powder and the spraying and postspray processes are apt to make such processes unacceptable for commercial applications.

Nanostructure Technology and Rapid-Solidification Rate Processing Nanostructured materials are materials with at least one dimension in the nanostructure range. This means one dimension of less than 100 nm (some authors suggest smaller values). Certain titanium enthusiasts have advocated the use of nanostructure processing as a new means for extending the capabilities of titanium alloys. Investigations into nanostructured titanium alloys have included the use of mechanical alloying as well as other techniques. Much has been made of the ability of the extremely fine structures of nanostructured materials to introduced significant improvements in ductility and plastic deformation capabilities of titanium, but lower-temperature properties generally have not been a big issue in titanium use. The elevated-temperature range is what needs to be extended, and nanostructured fine-grain alloys are not likely to meet the demands of improved high-temperature creep resistance. Rapid-solidification rate (RSR) processing is a separate category from nanostructured materials but is related in the sense that microstructures can be produced that cannot be produced by conventional technology. In particular, it is believed that useful dispersion-strengthened alloys might be possible with RSR. Dispersion strengthening is the production of particulate materials, usually by in situ development, in the matrix of an alloy. Nickel-base superalloys and aluminum alloys are base systems that depend on precipitation of a second phase particulate to greatly increase strength. Usually, elements are added to the molten alloy in the ingot metallurgy process and, at a later stage in processing, dissolved (a solution heat treatment) and reprecipitated (an aging process)

to create small particles of a second phase dispersed in the matrix. Dispersed particles can be produced by introduction of solid particles or the creation of such particles during the melting process rather than by precipitation. Oxide or silicide dispersions are among those that have been used in metal systems. They are not as effective in raising strength as the conventional in situ techniques, but their benefits usually last longer at elevated temperatures. Dispersion strengthening could greatly contribute to the goal of increasing the temperature capability of titanium. Although improvement in high-temperature strength capability is the stated goal of dispersions in titanium-base systems, improvements can occur throughout the temperature range if conventional dispersions could be produced by precipitation processes. Conventional dispersions are difficult to achieve in titanium-base alloys, although silicon has proved useful in the improvement of the high-temperature capability of conventional systems. Most conventional titanium alloys for high-temperature use have silicon added (e.g., Ti-6Al-2Sn-4Zr-2Mo+Si) to produce a strengthening dispersion, with about 0.25 to 0.5% silicon being used. Unfortunately, the production of dispersoids in situ by conventional ingot metallurgy has not resulted in satisfactory product. It may be possible to retain potential precipitating elements in supersaturated solution in titanium by extremely fast cooling. RSR involves a number of different schemes for very-rapid-cooling molten titanium alloys. Using such schemes, desired alloy elements that would otherwise be rejected on normal solidification, even by rotating electrode process atomization, remain in solution. They can thus be dispersed in a favorable manner in subsequent processing steps. RSR techniques have been applied through the formation of titanium powders for processing into usable components. True RSR powder is essentially limited to one dimension at this time in order to facilitate heat extraction. This fact means that RSR is an extension of powder metallurgy technology and is a relatively expensive process to implement. Significant improvements in alloy properties must occur to justify its use. RSR processing has been used for the introduction of high fractions of metalloid (carbon, boron, silicon, gallium) compounds. Rare-earth (RE) elements have been added, but they can serve more to scavenge oxygen (present from the powder-making process) than to produce RE precipitates with titanium. RE oxides have been formed, and they are suitable for dispersion hardening. In RSR-processed alloys with boron, a titanium boride phase is precipitated. Although conventional alpha titanium alloys can be dispersion strengthened by RSR-induced precipitation, it has been claimed that the greatest benefits will accrue from specially designed alloys. A dispersion must be reasonably stable at the operating temperature of a system, so the crite-

rion for improving titanium-base systems is not only to create a dispersion but to create a stable one for use above approximately 700 °C (1290 °F). RSR is a high-cost process and results have not justified the expense. Not only have no significant alloys resulted after decades of work, but there is also the underlying concern that it will not be possible to retain dispersion effects so as to provide for good high-temperature alloys. There may be some future application of RSR to titanium, but RSR is unlikely to play any significant near-term role in expanding the temperature range of the metal.

Higher-Temperature Conventional Titanium Alloys Use of conventional titanium alloys at higher temperatures has been studied for many years. The operating temperature of titanium alloys relative to the melting point of the base metal is quite low. If it could be increased to a fraction similar to that for nickel-base superalloys, great design changes possibly could be effected. (Note that surface stability and resistance to embrittlement by oxygen pickup would have to be addressed.) Four decades ago, there were many claims about the better creep-rupture strength of the near-alpha or superalpha alloys, such as Ti-5Al-5Sn-5Zr, with substantially improved creep resistance over the widely used alloy, Ti-6Al-4V. One of the reasons that the early superalpha alloys, such as Ti-5Al-5Sn-5Zr, did not succeed was that such alloys seemed to be much more susceptible to hot salt stress-corrosion cracking (HSSCC), which was a design concern at the time. Later, the introduction of new titanium alpha-beta compositions significantly enhanced creep resistance with low tendency to HSSCC. The appearance of Ti-6Al2Sn-4Zr-2Mo and the addition of small amounts of silicon (0.25%) substantially increased the creep capability. Beta processing was used as well to improve creep resistance. Over the years, substantial additional effort was expended to increase the temperature capability of conventional alloys. For such alloys, the ultimate developments at present seem to be embodied in IMI 834 and Ti 1100, both of which are usable to slightly higher temperatures than their predecessor conventional alloys—approximately 595 °C (1100 °F) compared with approximately 566 °C (1050 °F) for alloys such as Ti-6Al-2Sn-4Zr-2Mo+Si. Even if new conventional alloys could be developed with higher creep capability than present alloys have, there is no indication that resistance to oxygen pickup has been increased, nor that metallurgical stability has been improved. A condition remains in which environmental and exposure restrictions limit the upper application-temperature point for conventional titanium alloys. One solution to the problem of surface stability could be the introduction of coatings, but there is little indi-

136 / Titanium: A Technical Guide cation of significant improvement in that area in the near future.

Closing Comments Lower-Cost Alloys. For over a decade, the titanium industry has experimented with the development of alloys and processes specifically designed to reduce costs for use of titanium. In the early 1990s, a series of titanium alloys was introduced (see Table 14.2) that claimed to provide reduced cost without significant property reductions. These lower costs were achieved through modifications to arc melting practices and to subsequent fabrication steps. Use of scrap was increased in one instance, and alloy element substitution was done. The alloy Ti-6Al-1.7Fe-0.1Si was introduced with claims that mechanical properties were comparable to Ti-6Al-4V. The latter alloy, however, still continues to hold its place as the dominant titanium alloy in commercial and military use. Lower-cost alloys, as with any new alloys, have a difficult time supplanting existing alloys because of the costs associated with generating a new property database. It is all well and good to portray an alloy as comparable to another with room-temperature tensile data. It is quite another situation to generate the data to substantiate comparability across the board so a designer will feel comfortable using a new alloy. With the resurgence of the titanium industry in the middle to end of the last decade, perhaps any urgency for reduced costs to promote titanium use was tempered by the excellent business climate. The question of whether or not lower-cost alloys are used in the future to a great extent will be determined by producer capacity (or over capacity) to make sponge and the extent to which producers and users are willing to devote resources to generate design data. Applications for less demanding or less potential life-threatening situations (e.g., in the automotive industry) have a fairly good chance of adopting lower-cost titanium alloys.

Mergers, Consolidations, and Business Practices. Perhaps one of the more significant changes taking place in the titanium (and other) industries is the trend to consolidation of specifications. This does not necessarily mean fewer alloys, but it does mean that the same alloy will be governed by fewer specifications. By agreeing to use more industry-wide standards, customers will enable producers and processors (e.g., forgers and casters) to reduce their costs; therefore, costs to customers will be reduced accordingly. While this is a good business practice, it remains to be seen whether or not it is a good technical practice. Generally, standardization always trends to the lowest common denominator. Property levels are not going to be improved by consolidation of specifications. New Outlets. There are various outlets for titanium and its alloys that will continue to increase, but not at the incredible rate at which titanium recently was accepted (and then replaced to a significant degree) in the golf industry. It is always difficult to predict application trends, and the titanium industry has suffered through many ups and downs over its more than half century of commercial existence. An interesting application announced in 1999 was the planned construction in Japan of an all-titanium fishing boat. According to its developers, the all-titanium ship offers improved fuel efficiency, reduced maintenance costs, and increased speed. Plans were also announced for future production of pleasure boats, yachts, and high-speed police boats, as well as additional fishing boats if the initial all-titanium boat is a success. Perhaps all-titanium ships will be an economic success and create a new commercial outlet for the metal. The all-titanium automobile is not around the corner, but there undoubtedly will be increased usage for the metal in automotive applications. Nonburning Titanium. Another interesting aspect of titanium technology is the concern for production of a nonburning titanium alloy that would make all-titanium compressor rotor sections in gas turbines more safe. In rotors, wear or defects in mating components can cause

blades (rotating components) to impinge on stator vanes (nonrotating components). The frictional heating can quickly cause a very intense fire to occur. In current design, titanium fire considerations prohibit use of titanium rotors and titanium stator vanes in close proximity when applied in the high-pressure compressor (HPC) of a gas turbine. Thin section titanium alloy parts can burn in air when ignited by a strong heat source, such as that resulting from a heavy rub between blades and stator vanes. The thermodynamics of the rapid oxidation of titanium drive towards extremely intense combustion if a fire starts in the presence of conventional titanium alloys. Increasing the burn resistance of titanium alloys would allow more extensive use and could result in weight savings of nearly 50% (for each component) through the use of titanium alloys to replace the current steels and nickel-base superalloys. Several nonburning titanium alloy development programs were run during the 1990s. A burn-resistant beta alloy, Alloy C (Ti-35V15Cr), was developed by Pratt & Whitney in partnership with Wah Chang for use in the F119 gas turbine engine. Burn tests produced results, as shown in Fig. 14.6, where it is obvious that Alloy C provides a substantial temperature advantage over Ti-6Al-4V. Work has been carried on in England to produce a more cost-competitive alloy to Alloy C. It may be that these alloys will find substantial military applications, but it is doubtful that safety considerations for commercial gas turbine engine design will permit incorporation of nonburning titanium. The Status Quo on Alloy Development. The wave of mergers and acquisitions at the end of the 1990s signaled a sea of change in the business climate. New alloys are no longer coming from the producers with much regularity. Virtually all the more recently applied conventional alloys were invented prior to 1990. Ti-6Al-4V alloy, around for nearly a half century, is still the most-used composition. Manufacturers of sporting goods (e.g., golf clubs and

Table 14.2 Properties of some lower-cost titanium alloys compared with Ti-6A1-4V Alloy

Ti-6A1-4V(a) Oremet auto-grade(b)(c) RMI RM(b)(c) RMI VM(e) Timetal-62S

Yield strength, MPa (ksi)

Ultimate tensile strength, MPa (ksi)

Elongation, %

Reduction in area, %

950 (138) 1025 (149)

985 (143) 1115 (162)

14 15

37 38

1005 (146) 895 (130) 1040 (151)

1070 (155) 1000 (145) 900 (144)

13 19 15

ND(d) 40 34

(a) Beta rolled. (b) Alpha-beta rolled. (c) Average. (d) Not determined. (e) Alpha-beta annealed

Pressure, kPa (psi)

1035 (150)

345 (50)

93 (200)

200 (400)

315 (600)

425 (800)

540 (1000)

650 (1200)

Temperature, °C (°F)

Fig. 14.6

Locus of burn and no-burn regions for Alloy C and workhorse alpha-beta titanium alloy Ti-6Al-4V

Advanced Alloys and Future Directions / 137 bicycles) all use long-standing alloys for their products. Except in certain areas of application, any person desiring to apply titanium alloys to a product will have few, if any, new conventional-type alloys to choose from in the next decade, although more availability of lower-cost

alloys may be achieved. Lack of new alloy development may not be such a bad thing because the existing alloys will have an even longer history of successful application on which to build. Growth Potential. The largest area of growth for titanium in the near future undoubtedly will be the continued increase in the appli-

cation of castings for commercial products. Near-net shape can cut the cost of titanium products, and casting is a proven technology to produce such shapes. Expanded use of titanium scrap is likely, and the relaxation and consolidation of specifications should help to further enable producers to reduce costs.

Titanium: A Technical Guide Matthew J. Donachie, Jr., p283-288 DOI:10.1361/tatg2000p283

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Appendix C

Cross Reference to Equivalent Titanium Alloys THE FOLLOWING LISTING was developed to cross index chemically similar specifications. The selected specifications are listed alphanumerically by country of origin. It is recommended that this index serve only as a guide.

Any determination of the true equivalence of any two alloys should only be made after careful comparison of their chemical compositions. For further information on the chemical compositions and mechanical properties of the alloys

Designation

Designation

China GB 3620 TA-1 GB 3620 TA-2 GB 3620 TA-3 GB 3620 TA-7 GB 3620 TC-10 Ti-3Al-2.5V Ti-8Al-1Mo-1V

Alloy name

prEN3443 Ti-P04 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700 Ti-5Al-2.5Sn Ti-6Al-6V-2Sn Ti-3Al-2.5V Ti-8Al-1Mo-1V

prEN3451 Ti-P02 prEN3452 Ti-P02 prEN3453 Ti-P04 prEN3456 prEN3457 prEN3458 prEN3460 Ti-P02

Europe AECMA prEN2517 Ti-P63 prEN2518 Ti-P02 prEN2519 Ti-P04 prEN2520 Ti-P04 prEN2525 P01 prEN2526 Ti-P02 prEN2527 Ti-P04 prEN2530 prEN2531 prEN3120 prEN3310 prEN3311 prEN3312 prEN3313 prEN3314 prEN3315 prEN3316 Ti-P64 prEN3317 Ti-P64 prEN3318 Ti-P64 prEN3319 Ti-P64 prEN3320 Ti-P64 prEN3352 prEN3353 prEN3354 prEN3355 prEN3378 Ti-P02 prEN3441 P01 prEN3442 Ti-P02

prEN3461 Ti-P04 Ti-6Al-4V Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, astm grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-6Al-4V Ti-P69, Ti-3Al-2.5V Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-6Al-6V-2Sn Ti-6Al-6V-2Sn Ti-6Al-6V-2Sn Ti-6Al-6V-2Sn Ti-6Al-6V-2Sn Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400

prEN3464 prEN3467 prEN3487 P01 prEN3496 Ti-P04 prEN3498 Ti-P02 prEN3499 Ti-P04

Alloy name

Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM, grade 2, UNS R50400 Unalloyed titanium, ASTM, grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-6Al-4V Unalloyed titanium, ASTM, grade 1, UNS R50250 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM, grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700

France AIR 9182 T-35 9182 T-35 9182 T-40 9182 T-50 9182 T-60 9183 T-A6V 9184 T-A6V Ugine TD12ZrE UT35 UT35-02

UT40 UT50

listed in this index, the reader may find it useful to consult such publications as the Worldwide Guide to Equivalent Nonferrous Metals and Alloys, 3rd edition, ASM, 1995 and Woldman’s Engineering Alloys, 9th edition, ASM, 2000. Designation

UT60 UT662 UT6242 UTA5E UTA5EL UTA6V UTA7D UTA8DV

17850 3.7165 17850 Ti I 17850 Ti II 17850 Ti III 17850 Ti IV 17850 WL 3.7035

17850 WL 3.7065

Ti-11.5Mo-6Zr-4.5Sn Unalloyed titanium, ASTM grade 2, UNS R50400 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 (continued)

Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-6V-2Sn Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-6Al-4V Ti-7Al-4Mo Ti-8Al-1Mo-1V

Germany DIN 17850 3.7025

17850 WL 3.7055

Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM, grade 2, UNS R50400 Unalloyed titanium, ASTM, grade 2, UNS R50400 Unalloyed titanium, ASTM, grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-6Al-4V

Alloy name

17851 3.7165 17851 3.7225

17851 3.7235

17851 3.7255

17851 Ti-5Al-2.5Sn 17851 WL 3.7115 17860 3.7025 17860 3.7035 17860 3.7055 17860 3.7065 17860 3.7615 17862 3.7025

Unalloyed titanium, ASTM grade 1, UNS R50250 Ti-6Al-4V Unalloyed titanium, ASTM, grade 1, UNS R50250 Unalloyed titanium, ASTM, grade 2, UNS R50400 Unalloyed titanium, ASTM, grade 2, UNS R50400 Unalloyed titanium, ASTM, grade 3, UNS R50550 Unalloyed titanium, ASTM, grade 2, UNS R50400 Unalloyed titanium, ASTM, grade 2, UNS R50400 Unalloyed titanium, ASTM, grade 3, UNS R50550 Ti-6Al-4V Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-5Al-2.5Sn Ti-5Al-2.5Sn Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Unalloyed titanium, ASTM grade 1, UNS R50250

284 / Titanium: A Technical Guide Designation

Germany (continued) 17862 3.7035 17862 3.7055 17862 3.7065 17862 3.7615 17863 3.7025 17863 3.7035 17863 3.7055 17863 3.7065 17864 3.7025 17864 3.7035 17864 3.7055 17864 3.7065 17864 3.7615 Otto Fuchs T2 T3 T6 TL52 TL62 TL64 TL64 ELI Thyssen Contimet 30 35 35 D 55 AlMoV8-1-1 AlSn52 AlSn52 ELI AlSnZrMo 6-2-4-2 AlV 32 AlV 64 AlV 64 ELI AlVSn 6-6-2 Pd 02/30

Pd 02/35

Pd 02/35 D

TiNiMo83 Thyssen LT 24 31 33 Thyssen RT 12(Pd)

15(Pd)

Alloy name

Designation

Alloy name

18(Pd) Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700 Ti-5Al-2.5Sn Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-4V Ti-6Al-4V

Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250

Titan RT 20

Unalloyed titanium, ASTM grade 3, UNS R50550

Werkstoff-Nr 3.7064

Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-6Al-4V

3.7164 3.7264

Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Ti-5Al-2.5Sn Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-6V-2Sn

3.7034 3.7114 3.7144 3.7174

Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-4V Ti-6Al-6V-2Sn

Daido DT1

Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V

DT2 DT3 DT4 DT5 JIS Class 1 Ti class 1

Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250

Class 3 H 4361 TTH 35D, class 2 H 4600 TP 28 H/C, class 1 H 4600 TP 35 H/C, class 2 H 4600 TP 49 H/C, class 3 H 4600 TR 28 H/C, class 1 H 4600 TR 35 H/C, class 2,

H 4631 TTH 28, W/WD class 1 H 4631 TTH 35, W/WD class 2 H 4631 TTH 49, D class 3 H 4631 TTH 49, W/WD class 3 H 4635 type 11, TTP28PdD

H 4635 type 11, TTP28PdW H 4635 type 11, TTP28PdWD H 4635 type 12, TTP35PdD

H 4635 type 12, TTP35PdW H 4635 type 12, TTP35PdWD H 4635 type 13, TTP49PdD

Japan

H 4600 TR 49 H/C, class 3 H 4630 TTP 28, D/E class 1 H 4630 TTP 28, W/WD class 1 H 4630 TTP 35, D/E class 2 H 4630 TTP 35, W/WD class 2 H 4630 TTP 49, D/E class 3 H 4630 TTP 49, W/WD class 3 H 4631 TTH 28, D class 1

H 4635 type 11, TTP28PdE

H 4635 type 12, TTP35PdE

WL 3.7024

Class 2 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Ti-8Al-1Mo-1V Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-3Al-2.5V Ti-6Al-4V Ti-6Al-4V Ti-6Al-6V-2Sn Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400

Designation

Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 3, UNS R50550 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250

(continued)

H 4635 type 13, TTP49PdE H 4635 type 13, TTP49PdW H 4635 type 13, TTP49PdWD H 4636 type 11, TTH28PdD H 4636 type 11, TTH28PdW H 4636 type 11, TTH28PdWD H 4636 type 12, TTH35PdD H 4636 type 12, TTH35PdW H 4636 type 12, TTH35PdWD H 4636 type 13, TTH49PdD H 4636 type 13, TTH49PdW H 4636 type 13, TTH49PdWD H 4650 TB 28, C/H class 1 H 4650 TB 35, C/H class 2 H 4650 TB 49, C/H class 3 H 4655 type 11, TB28PdC H 4655 type 11, TB28PdH H 4655 type 12, TB35PdC H 4655 type 12, TB35PdH

Alloy name

Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250

Cross Reference to Equivalent Titanium Alloys / 285

Designation

H 4655 type 13, TB49PdC H 4655 type 13, TB49PdH H 4670 TW 28, class 1 H 4670 TW 35, class 2 H 4670 TW 49, class 3 H 4675 type 11, TW28Pd H 4675 type 12, TW35Pd H 4675 type 13, TW49Pd Kobe KS3-2.5 KS5-2-2-4-4 KS5-2.5 KS5-2.5ELI KS6-2-4-2 KS6-2-4-6 KS6-4 KS6-4ELI KS6-6-2 KS8-1-1 KS10-2-3 KS13-11-3 KS15-3-3-3 KS40 KS40LF KS40PdA

KS40PdB

KS40S KS50 KS50LF KS50PdA

KS50PdB

KS60 KS60LF KS70 KS70LF KS70PdA

KS70PdB

KS85 KSG12 KSG12S

Alloy name

Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250

Designation

MMA 5137 Nippon T1X Sumitomo SAT-325 SAT-525 ST-6 ST-40 ST-40P

ST-50 ST-50P

ST-60P Ti-3Al-2.5V Ti-5Al-2Sn-2Zr-4Mo-4Cr Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-6Mo Ti-6Al-4V Ti-6Al-4V Ti-6Al-6V-2Sn Ti-8Al-1Mo-1V Ti-10V-2Fe-3Al Ti-13V-11Cr-3Al Ti-15V-3Cr-3Al-3Sn Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 1, UNS R50250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 1, UNS R50250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 3, UNS R50550 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, grade 4, UNS R50700 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400

ST-70 ST-80 Ti-6Al-6V-2Sn Toho 15PAT

15PBT

20PAT

20PBT

64AT 325AT 525AT 662AT TIB TIBLF TIC TICLF TID Russia 4200 GOST 1.90000-70 VT6 1.90000-76 VT1-0 1.90013-71 VT1-00 1.90060-72 VT6L 1.90060-72 VTIL 19807-74 VT5-1 19807-74 VT6S AK2 IMP-7 IMP-10 VT5-1KT

Alloy name

Designation

Alloy name

Spain Ti-5Al-2.5Sn Unalloyed titanium, ASTM grade 2, UNS R50400 Ti-3Al-2.5V Ti-5Al-2.5Sn Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 2, UNS R50400 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-6V-2Sn

UNE 38-711 L-7001 38-712 L-7002 38-714 L-7004 38-715 L-7021

38-716 L-7101 38-717 L-7102 38-718 L-7103 38-723 L-7301 38-725 L-7303 38-729 L-7701 38-730 L-7702 United Kingdom BS TA14 TA15 TA16 TA17 TA56 TA59 2TA1 2TA2

Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-6Al-4V Ti-3Al-2.5V Ti-5Al-2.5Sn Ti-6Al-6V-2Sn Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-6Al-4V Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Ti-6Al-4V Unalloyed titanium, ASTM grade 2, UNS R50400 Ti-5Al-2.5Sn Ti-6Al-4V Ti-3Al-2.5V Ti-3Al-2.5V Ti-13V-11Cr-3Al Ti-5Al-2.5Sn

(continued)

Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-5Al-2.5Sn Ti-8Al-1Mo-1V Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-4V Ti-6Al-6V-2Sn Ti-13V-11Cr-3Al Ti-11.5Mo-6Zr-4.5Sn

2TA3 2TA4 2TA5 2TA6 2TA6 2TA7 2TA7 2TA8 2TA8 2TA9 2TA9 2TA10 2TA11 2TA12 2TA13 2TA28 DTD 5013 5023 5073 5273 5283 5303 5313 5323 5363 IMI 110

Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-6Al-4V Ti-6Al-4V Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 3, UNS R50550 Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Unalloyed titanium, ASTM grade 1, UNS R50250

286 / Titanium: A Technical Guide Designation

Alloy name

United Kingdom (continued) 115 Unalloyed titanium, ASTM grade 1, UNS R50250 125 Unalloyed titanium, ASTM grade 2, UNS R50400 130 Unalloyed titanium, ASTM grade 2, UNS R50400 130 Unalloyed titanium, ASTM grade 3, UNS R50550 155 Unalloyed titanium, grade 4, UNS R50700 160 Unalloyed titanium, grade 4, UNS R50700 260 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 262 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 318 Ti-6Al-4V United States … … … … … … … … …

…

… … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … …

… …

IMI 230; Ti-2.5Cu; AECMA Ti-P11 IMI 367; Ti-6Al-7Nb IMI 417 IMI 550; Ti-4Al-4Mo-2Sn-0.5Si IMI 551; Ti-4Al-4Mo-4Sn-0.5Si IMI 679; Ti-11Sn-5Zr-2.25Al-1Mo-0.25Si IMI 685; Ti-6Al-5Zr-0.5Mo-0.25Si IMI 829; Ti-5Al-3.5Sn-3.0Zr-1Nb-0.3Si IMI 834; Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo -0.35Si Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400 Ti-3Al-2.5V Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) Ti-4.5Al-3V-2Mo-2Fe Ti-5Al-2.5Fe Ti-5Al-2.5Sn Ti-5Al-2Sn-2Zr-4Mo-4Cr Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe Ti-5Al-5Sn-2Zr-2Mo-0.25Si Ti-6-22-22S; Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.25Si Ti-6Al-2Nb-1Ta-0.8Mo Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-6Mo Ti-6Al-4V Ti-6Al-6V-2Sn Ti-7Al-4Mo Ti-8Al-1Mo-1V Ti-8Mo-8V-2Fe-3Al Ti-8V-5Fe-1Al Ti-10V-2Fe-3Al Ti-11.5Mo-6Zr-4.5Sn Ti-11.5V-2Al-2Sn-11Zr Ti-12V-2.5Al-2Sn-6Zr Ti-13V-11Cr-3Al Ti-13V-2.7Al-7Sn-2Zr Ti-15Mo-5Zr Ti-15Mo-5Zr-3Al Ti-15V-3Cr-3Al-3Sn Ti-16V-2.5Al TIMETAL 21S; Ti-15Mo-3Al-2.7Nb-0.25Si TIMETAL 62S; Ti-6Al-1.7Fe-0.1Si TIMETAL 1100; Ti-6Al-2.75Sn-4Zr-0.4Mo-0.45Si; Ti-1100 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400

Designation

… … AMS 4900J 4901L 4902E 4905A 4906 4907D 4909D 4910J 4911F 4914 4915C 4915F 4916E 4917D 4918F 4919C 4919G 4920 4921F 4924D 4926H 4928K 4930C 4931 4933A 4934A 4935E 4936B 4936C 4941C 4942C 4943D 4944D 4945 4951E 4951E AMS 4951 4953D 4954D 4955B 4956B 4957 4958 4959B 4965E 4966J 4967F 4970E 4971C 4972C 4973C 4975E 4975F 4976C 4976D 4978B 4978C 4979B 4980B 4981B 4983A 4984 4985A 4986 4987 4991A 4993A

Alloy name

Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 2, UNS R50400 Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-6Al-4V Ti-15V-3Cr-3Al-3Sn Ti-8Al-1Mo-1V Ti-8Al-1Mo-1V Ti-8Al-1Mo-1V Ti-13V-11Cr-3Al Ti-6Al-6V-2Sn Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-4V Unalloyed titanium, grade 4, UNS R50700 Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-8Al-1Mo-1V Ti-6Al-4V Ti-6Al-4V Ti-6Al-6V-2Sn Ti-6Al-6V-2Sn Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 2, UNS R50400 Ti-3Al-2.5V Ti-3Al-2.5V Ti-3Al-2.5V Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 1, UNS R50250 Ti-5Al-2.5Sn Ti-6Al-4V Ti-8Al-1Mo-1V Ti-6Al-4V Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) Ti-13V-11Cr-3Al Ti-6Al-4V Ti-5Al-2.5Sn Ti-6Al-4V Ti-7Al-4Mo Ti-6Al-6V-2Sn Ti-8Al-1Mo-1V Ti-8Al-1Mo-1V Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-6V-2Sn Ti-6Al-6V-2Sn Ti-6Al-6V-2Sn Ti-11.5Mo-6Zr-4.5Sn Ti-6Al-2Sn-4Zr-6Mo Ti-10V-2Fe-3Al Ti-10V-2Fe-3Al Ti-6Al-4V Ti-10V-2Fe-3Al Ti-10V-2Fe-3Al Ti-6Al-4V Ti-6Al-4V (continued)

Designation

4995 4996 4997 4998 ASME SB265 grade 3 SB265 Ti grade 1 SB265 Ti grade 2 SB381 F-1 SB381 F-2 SB381 F-3 ASTM B 265 grade 3 B 265 grade 4 B 265 grade 5 B 265 grade 6 B 265 grade 7

B 265 grade 10 B 265 grade 11

B 265 grade 12 B 265 Ti grade 2 B 265-79 B 265-79 Ti grade 1 B 337 grade 3 B 337 grade 7

B 337 grade 9 B 337 grade 10 B 337 grade 11

B 337 grade 12 B 337 Ti grade 2 B 337-87 Ti grade 1 B 338 grade 3 B 338 grade 7

B 338 grade 9 B 338 grade 10 B 338 grade 11

B 338 grade 12 B 338 Ti grade 2 B 338-87 Ti grade 1 B 348 grade 3 B 348 grade 4 B 348 grade 5 B 348 grade 6 B 348 grade 7

Alloy name

Ti-5Al-2Sn-2Zr-4Mo-4Cr Ti-6Al-4V Ti-5Al-2Sn-2Zr-4Mo-4Cr Ti-6Al-4V Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-5Al-2.5Sn Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-11.5Mo-6Zr-4.5Sn Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, grade 12, R53400 Unalloyed titanium, grade 2, UNS R50400 Ti-3Al-2.5V Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 3, UNS R50550 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-3Al-2.5V Ti-11.5Mo-6Zr-4.5Sn Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 3, UNS R50550 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-3Al-2.5V Ti-11.5Mo-6Zr-4.5Sn Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-5Al-2.5Sn Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250

Cross Reference to Equivalent Titanium Alloys / 287 Designation

B 348 grade 9 B 348 grade 11

B 348 grade 12 B 348 Ti grade 2 B 348(10)-87 B 348-87 Ti grade 1 B 367 grade C-2 B 367 grade C-3 B 367 grade C-5 B 367 grade C-6 B 367, grade Ti-Pd 7B

B 367-87 C-3 B 367-87 Ti, grade 2 B 381 grade F-3 B 381 grade F-4 B 381 grade F-5 B 381 grade F-6 B 381 grade F-7

B 381 grade F-9 B 381 grade F-11

B 381 grade F-12 B 381 Ti grade F-2 B 381-87 F-1 F 136 F 467-84 grade 4 F 467-84 grade 5 F 467-84 grade 7

F 467-84, Ti grade 2 F 467-84a Ti, grade 1 F 467M-84a, grade 7

F 467M-84a, Ti grade 2 F 467M-84b, Ti grade 1 F 468-84 F 468-84 grade 4 F 468-84 grade 7

F 468-84, Ti grade 2 F 468-84a, Ti grade 1 F 468M-84b, grade 7

F 468M-84b, Ti grade 1 F 468M-84b, Ti grade 2 F 67 grade 3

Alloy name

Designation

Ti-3Al-2.5V Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400 Unalloyed titanium, ASTM grade 2, UNS R50400 Ti-11.5Mo-6Zr-4.5Sn Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-5Al-2.5Sn Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Ti-5Al-2.5Sn Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-3Al-2.5V Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Ti-6Al-4V Unalloyed titanium, grade 4, UNS R50700 Ti-6Al-4V Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM Ti grade 1, UNS R50250 Ti-6Al-4V Unalloyed titanium, grade 4, UNS R50700 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM Ti grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550

F 67 grade 4 F 67 Ti grade 2 F 67-88 Ti grade 1 Astro Ti-3Al-8V-6Cr-4Zr-4Mo Ti-6Al-2Sn-4Zr-6Mo Ti-13V-11Cr-3Al

Alloy name

Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) Ti-6Al-2Sn-4Zr-6Mo Ti-13V-11Cr-3Al

AWS A5.16-70 ERTi-0.2Pd grade 7 A5.16-70 ERTi-1

Modified Ti (Ti-0.2Pd), UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 1, UNS R50250 A5.16-70 ERTi-2 Unalloyed titanium, ASTM grade 1, UNS R50250 A5.16-70 ERTi-3 Unalloyed titanium, ASTM grade 1, UNS R50250 A5.16-70 ERTi-3Al-2.5V Ti-3Al-2.5V A5.16-70 ERTi-3Al-2.5V-1 Ti-3Al-2.5V A5.16-70 ERTi-4 Unalloyed titanium, ASTM grade 2, UNS R50400 A5.16-70 ERTi-5Al-2.5Sn Ti-5Al-2.5Sn A5.16-70 Ti-5Al-2.5Sn ERTi-5Al-2.5Sn-1 A5.16-70 Ti-6Al-2Nb-1Ta-0.8Mo ERTi-6Al-2Cb-1Ta-1Mo A5.16-70 ERTi-6Al-4V Ti-6Al-4V A5.16-70 ERTi-6Al-4V-1 Ti-6Al-4V A5.16-70 Ti-8Al-1Mo-1V ERTi-8Al-1Mo-1V A5.16-70 Ti-13V-11Cr-3Al ERTi-13V-11Cr-3Al Cabot Ti-3Al-2.5V Chase Ext. CDX 8Al-1Mo-1V GR-1 GR-2 GR-4 R-32 Crucible 3Al-2.5V A-40 Pd

A-70 Beta III

Ti-3Al-2.5V Ti-8Al-1Mo-1V Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 3, UNS R50550 Ti-3Al-2.5V Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, grade 4, UNS R50700 Ti-11.5Mo-6Zr-4.5Sn

Howmet Ti-6Al-2Sn-4Zr-6Mo Martin Mar Martin Mar MIL A-46077D F-83142 comp 1 F-83142A comp 2 F-83142A comp 3 F-83142A comp 5 F-83142A comp 6 F-83142A comp 7 F-83142A comp 8 F-83142A comp 9 F-83142A comp 11 F-83142A comp 12 F-83142A comp 13 T-0946J code CP-4 T-81556A code A-1

Ti-6Al-2Sn-4Zr-6Mo

Designation

Ti-5Al-2.5Sn Ti-8Al-1Mo-1V Ti-6Al-4V Ti-6Al-4V Ti-6Al-6V-2Sn Ti-6Al-2Sn-4Zr-2Mo-0.08Si Unalloyed titanium, grade 4, UNS R50700 T-81556A, code CP-2 Unalloyed titanium, ASTM grade 3, UNS R50550 T-81556A, code CP-3 Unalloyed titanium, ASTM grade 2, UNS R50400 T-81556A, code CP-4 Unalloyed titanium, ASTM grade 1, UNS R50250 T-81915 Type I, comp A Unalloyed titanium, ASTM grade 2, UNS R50400 T-81915 Type II, comp A Ti-5Al-2.5Sn T-81915 Type III, comp A Ti-6Al-4V T-81915 Type III, comp B, Ti-6Al-2Sn-4Zr-2Mo-0.08Si T-81915A Unalloyed titanium, ASTM grade 1, UNS R50250 T-9046J code A-1 Ti-5Al-2.5Sn T-9046J code A-2 Ti-5Al-2.5Sn T-9046J code A-3 Ti-6Al-2Nb-1Ta-0.8Mo T-9046J code A-4 Ti-8Al-1Mo-1V T-9046J code AB-1 Ti-6Al-4V T-9046J code AB-2 Ti-6Al-4V T-9046J code AB-3 Ti-6Al-6V-2Sn T-9046J code AB-4 Ti-6Al-2Sn-4Zr-2Mo-0.08Si T-9046J code AB-5 Ti-3Al-2.5V T-9046J code B-1 Ti-13V-11Cr-3Al T-9046J code B-2 Ti-11.5Mo-6Zr-4.5Sn T-9046J code B-3 Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) T-9046J code CP-1 Unalloyed Titanium, grade 4, UNS R50700 T-9046J code CP-2 Unalloyed titanium, ASTM grade 3, UNS R50550 T-9046J code CP-3 Unalloyed titanium, ASTM grade 2, UNS R50400 T-9047G Ti-6Al-4V T-9047G SP-70 Unalloyed titanium, grade 4, UNS R50700 T-9047G Ti-3Al-2.5V Ti-3Al-2.5V T-9047G Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) Ti-3Al-8V-6Cr-4Mo-4Zr T-9047G Ti-11.5Mo-6Zr-4.5Sn Ti-4.5Sn-6Zr-11.5Mo T-9047G Ti-5Al-2.5Sn Ti-5Al-2.5Sn T-9047G Ti-5Al-2.5Sn ELI Ti-5Al-2.5Sn T-9047G Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-2Mo T-9047G Ti-6Al-2Sn-4Zr-6Mo Ti-6Al-2Sn-4Zr-6Mo T-9047G Ti-6Al-6V-2Sn Ti-6Al-6V-2Sn T-9047G Ti-7Al-4Mo Ti-7Al-4Mo T-9047G Ti-8Al-1Mo-1V Ti-8Al-1Mo-1V T-9047G Ti-13V-11Cr-3Al Ti-13V-11Cr-3Al T-9047G Ti-CP-70 Unalloyed titanium, grade 4, UNS R50700 OREMET Ti Beta 3 Ti-1 Ti-2

Ti-6Al-4V Unalloyed titanium, grade 4, UNS R50700 Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-8Al-1Mo-1V Ti-6Al-4V Ti-6Al-4V Ti-6Al-6V-2Sn Ti-7Al-4Mo Ti-6Al-2Sn-4Zr-6Mo Ti-13V-11Cr-3Al Ti-11.5Mo-6Zr-4.5Sn Unalloyed titanium, ASTM grade 1, UNS R50250 Ti-5Al-2.5Sn (continued)

Alloy name

T-81556A code A-2 T-81556A code A-4 T-81556A code AB-1 T-81556A code AB-2 T-81556A code AB-3 T-81556A code AB-4 T-81556A, code CP-1

Ti-3 Ti-3-25 Ti-4 Ti-5-2.5 Ti-6-6-2 Ti-6Al-4V Ti-8-1-1 Ti-11

Ti-12

Ti-11.5Mo-6Zr-4.5Sn Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Ti-3Al-2.5V Unalloyed titanium, grade 4, UNS R50700 Ti-5Al-2.5Sn Ti-6Al-6V-2Sn Ti-6Al-4V Ti-8Al-1Mo-1V Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400

288 / Titanium: A Technical Guide Designation

OREMET (continued) Ti-17

Ti-17 Ti-38-6-44 Ti-6242 Ti-6246

Alloy name

Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-5Al-2Sn-2Zr-4Mo-4Cr Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-6Mo

RMI 0.2%Pd

Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 3Al-2.5V Ti-3Al-2.5V 3Al-8V-6Cr-4Zr-4Mo Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) 5Al-2.5Sn Ti-5Al-2.5Sn 5Al-2.5Sn ELI Ti-5Al-2.5Sn 6Al-2Cb-1Ta-1Mo Ti-6Al-2Nb-1Ta-0.8Mo 6Al-2Sn-4Zr-2Mo-0.10Si Ti-6Al-2Sn-4Zr-2Mo-0.08Si 6Al-2Sn-4Zr-6Mo Ti-6Al-2Sn-4Zr-6Mo 6Al-4V Ti-6Al-4V 6Al-4V-ELI Ti-6Al-4V 6Al-6V-2Sn Ti-6Al-6V-2Sn 8Al-1Mo-1V Ti-8Al-1Mo-1V 13V-11Cr-3Al Ti-13V-11Cr-3Al 25 Unalloyed titanium, ASTM grade 1, UNS R50250 40 Unalloyed titanium, ASTM grade 2, UNS R50400 55 Unalloyed titanium, ASTM grade 3, UNS R50550 70 Unalloyed titanium, grade 4, UNS R50700 Ti-7Al-4Mo Ti-7Al-4Mo

Designation

TIMET Ti-0.2Pd

Ti-75A TIMETAL 3-2.5 TIMETAL 3-8-6-4-4 TIMETAL 5-2.5 TIMETAL 5-2.5 ELI TIMETAL 6-2-1 TIMETAL 6-2-4-2 TIMETAL 6-2-4-6 TIMETAL 6-4 TIMETAL 6-4 ELI TIMETAL 6-4 STA TIMETAL 6-6-2 TIMETAL 6-6-2 STA TIMETAL 7-4 TIMETAL 8-1-1 TIMETAL 10-2-3 TIMETAL 13-11-3 TIMETAL 15-3 TIMETAL 17 TIMETAL 35A TIMETAL 35A Pd

TIMETAL 50A TIMETAL 50A Pd

SAE

TIMETAL 65A

Teledyne Tel-Ti-3Al-8V-6Cr-4Mo- Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) 4Zr Tel-Ti-13V-11Cr-3Al Ti-13V-11Cr-3Al

TIMETAL 100A

Teledyne AllVac Tel.AllVac Allvac 6-4

TMCA Ti-1

Teledyne Rodney A35 A40 A40 A55

Ti-6Al-2Sn-4Zr-6Mo Ti-6Al-4V

TIMETAL code 12

Ti-2 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, grade 4, UNS R50700 Unalloyed titanium, ASTM grade 3, UNS R50550

Ti-3 Ti-4 Ti-7

Alloy name

Designation

Ti-11 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, grade 4, UNS R50700 Ti-3Al-2.5V Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-6Al-2Nb-1Ta-0.8Mo Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-6Mo Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-6Al-6V-2Sn Ti-6Al-6V-2Sn Ti-7Al-4Mo Ti-8Al-1Mo-1V Ti-10V-2Fe-3Al Ti-13V-11Cr-3Al Ti-15V-3Cr-3Al-3Sn Ti-5Al-2Sn-2Zr-4Mo-4Cr Unalloyed titanium, ASTM grade 1, UNS R50250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 2, UNS R50400 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250

Ti-12 Ti-325 UNS R50100 R50120 R50125 R50130 R50250 R50400 R50550 R50700 R52250

R52400

R52401

R53400 R54520 R54521 R54522 R54523 R54620 R54621 R54810 R56210 R56260 R56320 R56321 R56400 R56401 R56402 R56740 R58010 R58030 R58640 R58650

Alloy name

Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400 Ti-3Al-2.5V Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2, UNS R50400 Unalloyed titanium, ASTM grade 1, UNS R50250 Unalloyed titanium, ASTM grade 2,UNS R50400 Unalloyed titanium, ASTM grade 3, UNS R50550 Unalloyed titanium, grade 4, UNS R50700 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS R52250 Modified Ti (Ti-0.2Pd), grade 7, UNS R52400; grade 11, UNS 52250 Modified Ti (Ti-0.2Pd),grade 7, UNS R52400; grade 11, UNS R52250 Ti-0.3Mo-0.8Ni, ASTM grade 12, R53400 Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-5Al-2.5Sn Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-6Al-2Sn-4Zr-2Mo-0.08Si Ti-8Al-1Mo-1V Ti-6Al-2Nb-1Ta-0.8Mo Ti-6Al-2Sn-4Zr-6Mo Ti-3Al-2.5V Ti-3Al-2.5V Ti-6Al-4V Ti-6Al-4V Ti-6Al-4V Ti-7Al-4Mo Ti-13V-11Cr-3Al Ti-11.5Mo-6Zr-4.5Sn Ti-3Al-8V-6Cr-4Mo-4Zr (Beta C) Ti-5Al-2Sn-2Zr-4Mo-4Cr

Titanium: A Technical Guide Matthew J. Donachie, Jr., p289-294 DOI:10.1361/tatg2000p289

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Appendix D

Listing of Selected Specification and Standardization Organizations THIS APPENDIX provides information about selected organizations that issue specifications and standards related to titanium and titanium alloys. Property data and composition requirements for selected metals and alloys as specified by several of these organizations are provided in the tables in Appendix B, “Titanium

Table D.1

Alloy Data Sheets.” A cross-reference listing of equivalent alloys is provided in Appendix C. The listings in this Appendix are organized into two groups: organizations based in the United States (listed in alphabetical order by organization name) and organizations outside the United States (listed in alphabetical order

by country). The non-U.S. organizations are typically the primary standardization body for the country listed. Details about the type and scope of the standards issued by each organization are provided in the listings. Not all countries and standardization organizations are included in this Appendix.

Specification and standardization organizations in the United States

Organization and address

Contact information

Aerospace Industries Association of America (AIA) 1250 Eye Street, NW, Suite 1200 Washington, DC 20005

Tel: 202-371-8400 Internet: www.aia-aerospace.org

American National Standards Institute (ANSI) 11 West 42nd Street, 13th Floor New York, NY 10036

Tel: 212-642-4900 Fax: 212-398-0023 e-mail: [email protected] Internet: www.ansi.org

(continued)

Description

Trade association representing U.S. manufacturers of commercial, military, and business aircraft, helicopters, aircraft engines, missiles, spacecraft, materials, and related components and equipment. As part of the AIA, the Aerospace Technical Council, Technical Specifications Division, directs the National Aerospace Standards Committee. Issues various aerospace-related standards, which are proposed guidelines for the aerospace industry. These National Aerospace Standards (NASS) are intended to eliminate misunderstandings between manufacturers and purchasers and may also be used to assist a purchaser with selection of a product for a specific application. National Aerospace Standards are available from several document resellers, including Global Engineering Documents (www.global.ihs.com) and the Document Engineering Company, Inc. (www.doceng.com). Acts as administrator and coordinator of the U.S. private sector voluntary standardization system. Represents the interests of its company, organization, government agency, institutional, and international members through an office in New York City and headquarters in Washington, D.C. ANSI does not itself develop American National Standards (ANSs); rather, the organization facilitates development by establishing consensus among qualified groups. Works to ensure that consensus, due process, and openness are employed by the more than 175 distinct entities currently accredited by the Federation. In 1999, the number of separate ANSs totaled 14,650. Promotes the use of U.S. standards internationally, advocates U.S. policy and technical positions in international and regional standards organizations, and encourages the adoption of international standards as national standards where these meet the needs of the user community. ANSI is the sole U.S. representative to the two major international standards organizations, the International Organization for Standardization (ISO) and, via the U.S. National Committee (USNC), the International Electrotechnical Commission (IEC). In many instances, U.S. standards are taken forward, through ANSI or its USNC, to the ISO or IEC, where they are adopted in whole or in part as international standards.

290 / Titanium: A Technical Guide

Table D.1

(continued)

Organization and address

Contact information

American Society for Testing and Materials (ASTM) 100 Barr Harbor Drive West Conshohocken, PA 19428

Tel: 610-832-9585 Fax: 610-832-9555 e-mail: [email protected] Internet: www.astm.org

American Society of Mechanical Engineers (ASME International) Three Park Avenue New York, NY 10016

Tel: 800-843-2763 973-882-1167 Internet: www.asme.org

American Welding Society (AWS) 550 NW LeJeune Road Miami, FL 33126 National Fire Protection Association (NFPA) 1 Batterymarch Park Quincy, MA 02269

Tel: 800-443-9353 305-443-9353 e-mail: [email protected] Internet: www.aws.org Tel: 617-770-3000 Fax: 617-770-0700 Internet: www.nfpa.org

National Institute of Standards and Technology (NIST) Standard Reference Materials Program Building 202, Room 204 Gaithersburg, MD 20899

Tel: 301-975-6478 Fax: 301-926-1630 e-mail: [email protected] Internet: www.nist.gov

Society of Automotive Engineers (SAE) 400 Commonwealth Drive Warrendale, PA 15096

Tel: 724-776-4841 Fax: 724-776-0790 e-mail: [email protected] Internet: www.sae.org

U.S. Department of Defense Document Automation and Production Service 700 Robbins Avenue Philadelphia, PA 19111

Tel: 215-697-2179 Internet: www.dodssp.daps.mil

Description

An industry-based standardization organization that publishes the Annual Book of ASTM Standards. Standards related to titanium and titanium alloys are contained in Volume 2.04 of Section 2, Nonferrous Metal Products. The Unified Numbering System (UNS) is a joint effort of ASTM and the Society of Automotive Engineers (see separate listing for SAE). The UNS is intended to provide a listing in which each distinct metal or alloy has a unique identification number. The publication Metals and Alloys in the Unified Numbering System lists these designations along with the nominal chemical composition for each entry as well as a cross reference to other specifications systems. In the UNS system, titanium alloys are designated R5XXXX; for example, Ti-6Al-4V (normal interstitial grade) is designated as UNS R56400. Issues standards that are used by personnel in research, testing, and design of power-producing machines such as internal combustion engines, steam and gas turbines, etc. ASME standards are also used in the design of power-using machinery such as refrigeration units and air-conditioning equipment. ASME publishes the Boiler and Pressure Vessel Code, which contains the determinations of “code cases” presented to an ASME committee; several of these cases provide guidelines concerning the use of titanium products. Develops codes, recommended practices, and guides according to American National Standards Institute (ANSI) procedures. The principal AWS specification related to welding of titanium is AWS A5.16, “Specification for Titanium and Titanium Alloy Welding Electrodes and Rods.” Issues the primary publication related to titanium safety, Standard for the Production, Processing, Handling, and Storage of Titanium (NFPA 481). Has been confirmed as an American National Standard (see separate listing for ANSI). Formerly the National Bureau of Standards (NBS), makes available Standard Reference Materials (SRMs), which are samples of a material certified with respect to chemical composition, chemical properties, or physical properties. SRMs are used in the calibration of an apparatus, the assessment of a measuring method, or for assigning values to materials. A professional engineering organization that issues approved standards and recommended practices (which are advisory in nature only). These documents are used primarily by designers, manufacturers, and maintenance personnel in the ground transportation and aerospace industries. In addition to SAE standards and recommended practices, SAE also issues Aerospace Material Specifications (AMSs), which focus on materials intended for aerospace applications. These standards are frequently used worldwide in industry and government procurement. The U.S. Department of Defense has adopted selected AMS specifications as MIL specs. AMS standards have been accepted as American National Standards. In some instances, non-U.S. agencies also have adopted AMS specifications. The Unified Numbering System (UNS) is a joint effort of SAE and the American Society for Testing and Materials (for a description of the UNS system, see the separate listing for ASTM). Military specifications are issued by the U.S. Department of Defense to define materials, products, and/or services used only, or predominantly, by military entities. All military specifications begin with the uppercase letters MIL. The next part of the designation is an uppercase letter representing the first letter of the title for the item specified. (Thus, T is used for titanium and F for forgings.) A serial number follows. Military standards also are issued that provide procedures for design, manufacturing, and testing. A standard designation is formatted MIL-STD-, followed by a serial number. The serial number for a MIL spec or standard may include a revision letter suffix (e.g., MIL-T-9046J). The revision levels of titanium specifications are important because many changes have occurred over the years. Many manufacturer and product manuals continue to reference earlier, superseded versions of the documents (in some cases as an aid to the customer and in other instances because the product may continue to be produced according to the requirements of the earlier version of the specification or standard). At times, amendments are issued to correct or qualify, not supersede, an existing revision level. It is important to determine whether amendments exist, because they often do much to clarify the basic specification or standard.

Listing of Selected Specification and Standardization Organizations / 291 Table D.2

Specification and standardization organizations outside the United States

Organization and address

Contact information

Description

Argentina Instituto Argentino de Normalizacion (IRAM) Peru 552/556 1068 Buenos Aires Argentina

Tel: 54 11 4345 6606 Fax: 54 11 4345 3468 e-mail: [email protected] Internet: www.iram.com.ar

IRAM is the Argentine standardization institute and is authorized by the government to deal, both in national and international ambits, with all the affairs related to standardization and quality control certification. Argentine standards will be preceded by IRAM. Some standards in Argentina will be regional for Pan America and will use the prefix COPANT.

Australia Standards Australia (SAA) P.O. Box 1055 Strathfield NSW 2135 Australia

Tel: 61 (02) 9746 4700 Fax: 61 (02) 9746 8450 e-mail: [email protected] Internet: www.standards.com.au

Issues standards used primarily by firms doing business in Australia and the southwest Pacific area. Standards Australia represents Australia on International Standards Organization (ISO), and International Electrotechnical Commission (IEC). Standards Australia maintains a strong relationship with Standards New Zealand, and the two organizations have a formal agreement on preparing and publishing joint Standards (AS/NZS).

Austria Osterreichisches Normungsinstitut (ON) (Austrian Standards Institute) Heinestrasse 38 A-1021 Wien Austria

Tel: 43 1 213 00-627 Fax: 43 1 213 00-360 e-mail: [email protected] Internet: www.on-norm.at

The Austrian Standards Institute (ON) represents Austria to the European Committee for Standardization (CEN) and the International Organization for Standardization (ISO). The Austrian standards begin with ONORM if just an Austrian standard or ONORMEN if the standard has been adopted by CEN and its members.

Tel: 32 2 738 01 11 Fax: 32 2 733 42 64

IBN designations are prefixed with the letters NBM.

Tel: 55 (021) 210 3122 Fax: 55 (021) 220 6436 55 (021) 220 1762 e-mail: [email protected] Internet: www.abnt.org.br

The Brazilian Association of Technical Standards (ABNT) issues national standards. These designations may begin with uppercase letters NBR or ABNT.

Tel: 359 2 989 84 88 Fax: 359 2 986 17 07 e-mail: [email protected]

Bulgarian standards are issued by the State Agency for Standardization and Metrology. The designations begin with the uppercase letters BDS and are followed by the numerical code of the standard.

Tel: 416 747 4000 Fax: 416 747 4149 E-mail: [email protected] [email protected] Internet: www.csa-international.org

All Canadian standards are preceded by the uppercase letters CSA. The standard or designation then follows.

Tel: 86 10 6 203 24 24 Fax: 86 10 6 203 37 37 e-mail: [email protected] Internet: www.csbts.cn.net

Responsible for materials standards in China. All standards are preceded by the uppercase letters GB, JB, and YB. A/T following the letters means that the standard is pending. The numeric standard identification then follows with a dash and then the year the standard was approved.

Czech Republic Cesky Normalizacni Institut (CSNI) (Czech Standard Institute) Biskupsky dvur 5 113 47 Praha Czech Republic

Tel: 42 (02) 21 802 111 Fax: 42 (02) 21 802 301 e-mail: [email protected] Internet: www.csni.cz

The Czech Standards Institute (CSNI) is concerned with standardization, metrology, testing, certification, and accreditation. The CSNI is a member of the ISO, IEC, CEN, and CENELEC. Czech standards are arranged according to classes and subgroups by a six-digit reference number. All standards are preceded by CSN.

Denmark Dansk Standard (DS) Danish Standardization Commission Kollegievej 6 Charlottenlund 2920 Denmark

Tel: 45 39 96 61 01 Fax: 45 39 96 61 02 e-mail: [email protected] Internet: www.ds.dk

The Danish Standards Association (DS) is involved in the standardization of all fields except telecommunications.

Tel: 358 0 149 9331 Fax: 358 9 146 4925 e-mail: [email protected] or [email protected] Internet: www.sfs.fi

SFS Standards are voluntary documents drawn by technical committees of SFS. SFS and its standards-writing bodies are members of the European standards organizations CEN, CENELEC, and ETSI. Finnish standards and designations are preceded by the letters SFS or SFSEN if European standard has been adopted.

Belgium Institut Belge de Normalisation (IBN) (Belgian Standardization Institute) Avenue de la Brabanconne 29 B-1040 Bruxelles Belgium Brazil Associacao Brasileira de Normas Tecnicas (ABNT) (Brazilian Association for Technical Standards) Avenida Treze de Maio, 13, 27o andar - Centro 20003-900 Rio de Janeiro-RJ Brazil Bulgaria State Agency for Standardization and Metrology (BDS) 21, 6th September Str. 1000 Sofia Bulgaria Canada CSA International (CSA) 178 Rexdale Blvd. Etobicoke (Toronto) ON M9W 1R3 Canada

China China State Bureau of Quality and Technical Supervision (CSBTS) 4 Zhichun Road Haidian District P.O. Box 8010 Beijing 100088 China

Finland Finnish Standard Association (SFS) P.O. Box 116 Fin-00241 Helsinki Finland

(continued)

292 / Titanium: A Technical Guide Table D.2

(continued)

Organization and address

France Association Francaise de Normalisation (AFNOR) (French Association for Standardization) Tour Europe 94049 Paris la Defense Cedex France

Contact information

Description

Tel: 33 1 42 91 55 55 Fax: 33 1 42 91 56 56 e-mail: [email protected] Internet: www.afnor.fr

AFNOR is the French representative to the European Committee for Standardization (CEN) and to International Standards Organization (ISO). AFNOR standards usually begin with NF, and if a CEN standard has been adopted, the prefix is NFEN.

Tel: 33 1 4552 45 24 Fax: 33 1 4552 45 74

The French Ministry of Defense issues AIR standards. The prefix AIR in uppercase letters appears with these designations.

Germany Deutsches Institut fur Normung e.V. (DIN) (German Standardization Institute) Burggrafenstrasse 6-10 D-10787 Berlin Germany

Tel: 49 30 26 01-0 Fax: 49 30 260 12 31 e-mail: [email protected] Internet: www.din.de

A member of the European Committee for Standardization (CEN) and the International Standards Organization (ISO).

Hungary Magyar Szabvanyugyi Testulet (MSZT) (Hungarian Standards Institution) Postafiok 24 1450 Budapest 9 Hungary

Tel: 36 1 218 30 11 Fax: 36 1 218 51 25 e-mail: [email protected] Internet: www.mszt.hu

A member body of the ISO, IEC, ETSI, and affiliate member in CEN and CENELEC. Hungarian standards are preceded by the letters MSZ.

India Bureau of Indian Standards (BIS) Manak Bhavan 9 Bahadur Shah Zafar Marg New Delhi 110002 India

Tel: 91 11 3230131 Fax: 91 11 323 4062 e-mail: [email protected] Internet: wwwdel.vsnl.net.in/bis.org

Indian standards begin with the prefix IS and are followed by a numerical code. BIS is a member of International Standards Organization (ISO) and International Electrotechnical Commission (IEC).

International International Organization for Standardization (ISO) 1 rue de Varembe Case postale 56 CH-1211 Geneve 20 Switzerland

Tel: 41 22 749 01 11 Fax: 41 22 733 34 30 e-mail: [email protected] Internet: www.iso.ch

A worldwide federation of national standards bodies.

Italy Ente Nazionale Italiano di Unificazione (UNI) (Italian National Standardization Office) Via Battistotti Sassi 11/b 20133 Milano Italy

Tel: 39 (02) 70 02 41 Fax: 39 (02) 70 10 61 49 e-mail: [email protected] Internet: www.unicei.it

UNI, the Italian National Standards Body, is a nonprofit organization involved in the area of standardization in all industrial, commercial, and tertiary sectors except for electrical and electrotechnical areas, and is legally recognized both at the national and European levels. Italian standards are preceded by the uppercase letters UNI and followed by an alphanumeric code.When UNI takes over an international standard, the uppercase letter UNI is followed by ISO or EN and by an alphanumeric code.

Japan Japanese Industrial Standards Committee (JISC) c/o Secretariat: Standards Department, Ministry of International Trade and Industry 1-3-1, Kasumigaseki, Chiyoda-ku Tokyo 100-1921 Japan

Tel: 81 3 3501 2096 Fax: 81 3 3580 8637 e-mail: [email protected] Internet: www.jisc.org

Issues standards that cover industrial or mineral products with the exception of those regulated by their own special standards organizations. JISC standards begin with the uppercase letters JIS and are followed by an uppercase letter that designates the division of the standard. This is then followed by a space and a series of digits.

Tel: 81 3 3583 8000 Fax: 81 3 3586 2014 Internet: www.jsa.or.jp

Works closely with the Japanese Industrial Standards Committee to publish Japanese standards and make them available to the public.

Mexico Direccion General de Normas (DGN) (General Directorate of Standards) Av. Puente de Tecamachalco No 6 Lomas de Tecamachalco, Seccion Fuentes Naucalpan de Juarez Mexico

Tel: 52 5 729 9300 exts. 4134 and 4157 Fax: 52 5 729 94 84 e-mail: [email protected] Internet: www.secofi.gob.mx/normas

The General Directorate of Standards (DGN) issues national standards for the country. Mexican standards begin with the uppercase letters NOM (Normas Officiales Mexicanas) or NMX (Normas Mexicanas).

Netherlands Nederlands Normalisatie-instituut (NNI) (Dutch Standardization Institute) Kalfjeslaan 2 P.O. Box 5059 2600 GB Delft Netherlands

Tel: 31 15 2 69 03 90 Fax: 31 15 2 69 01 90 e-mail: [email protected] Internet: www.nni.nl

Helps prepare Dutch standards and cooperates in the development of international standardization. Dutch standards are prefixed by the letters NEN and are followed by a numerical code.

Delegation Generale pour l’Armement (AIR) Centre de Documentation de l’Armement 26, Boulevard Victor 00460-Armees France

Japanese Standards Association (JSA) 1-24 Akasaka 4 Minato-ku Tokyo 107-8440 Japan

(continued)

Listing of Selected Specification and Standardization Organizations / 293 Table D.2

(continued)

Organization and address

Contact information

Description

New Zealand Standards New Zealand (NZS) 155 The Terrace Private Bag 2439 Wellington New Zealand

Tel: 64 (04) 498 5990 Fax: 64 (04) 498 5994 e-mail: [email protected] Internet: www.standards.co.nz

Involved with the development and application of national, regional, and international standards, of which many are developed in partnership with Australia. SNZ is New Zealand’s representative to ISO and IEC.

Norway Norges Standardiseringsforbund (NSF) (Norwegian Standards Association) P.O. Box 7020 Homansbyen N-0306 Oslo Norway

Tel: 47 2209 9200 Fax: 47 2204 9211 e-mail: [email protected] Internet: www.standard.no

The Norwegian Standards Association (NSF) is the national member of ISO and CEN and the body responsible for the approval and publishing of all Norwegian Standards. Norsk Standards are preceded by the uppercase letters NS.

Tel: 58 2 574294 1 Fax: 58 2 574294 1

Comprises national standards bodies of 18 countries from the United States and many Central and South-American countries. For its designations, the acronym COPANT in uppercase letters precedes the numeric code and the year of its adoption.

Poland Polish Committee for Standardization (PKN) ul. Elektoralna 2 P.O. Box 411 PL-00-950 Warszawa Poland

Tel: 48 22 620 54 34 Fax: 48 22 624 71 22 e-mail: [email protected] Internet: www.pkn.pl

Represents Poland in international (ISO and IEC) and regional (EN) standards organizations and participates in and is responsible for harmonizing Polish standards with the European standards. The Polish standards are prefixed with the uppercase letters PN or PNH. The designations or standards may appear in a number of ways.

Romania Asociatia de Standardizare Din Romania (ASRO) Str. Mendeleev nr.21-25 70168 Bucharest 1 Romania

Tel: 40 1 211 32 96 Fax: 40 1 210 08 33 e-mail: [email protected]

Asociatia de Standardizare din Romania (ASRO) is the national standardization body in Romania. The Romanian standards are preceded by the capital letters STAS followed by a numerical code that may be followed by the year the standard was adopted.

Russia State Committee of the Russian Federation for Standardization and Metrology Gosstandart of Russia (GOST) Leninsky Prospekt 9 Moskva 117049 Russian Federation

Tel: 7 095 236 40 44 Fax: 7 095 237 60 32 e-mail: [email protected] Internet: www.gost.ru

Gosstandart of Russia is the national certification body of the Russian Federation. The standards are prefaced with the uppercase letters GOST and are followed by a numerical code.

South Africa South African Bureau of Standards (SABS) 1 Dr Lategan Rd., Groenkloof Private Bag X191 Pretoria 0001 South Africa

Tel: 27 12 428 6925/6 Fax: 27 12 344 1568 e-mail: [email protected] Internet: www.sabs.co.za

South Africa’s official body for the preparation and publication of standards. The number of the South African standard is preceded by the letters SABS and followed by the numeric or alphanumeric material type or grade designation.

Spain Asociacion Espanola de Normalizacion y Certificacion (AENOR) (Spanish Association for Standardization and Certification) C Genova, 6 28004 Madrid Spain

Tel: 34 91 432 60 00 Fax: 34 91 310 45 96 e-mail: [email protected] Internet: www.aenor.es

The Spanish Association for Standardization and Certification (AENOR) is designated as a recognized body to develop Standardization and Certification (S+C) activities in Spain. The designations begin with the letters UNE, representing the Spanish words une norm Espanola.

Sweden Standardiseringen i Sverige (SIS) (Swedish Standards Institution) S:t Eriksgatan 115 Box 6455 SE-113 82 Stockholm Sweden

Tel: 46 8 610 30 00 Fax: 46 8 30 77 57 e-mail: [email protected] Internet: www.sis.se

The Swedish member of the international organizations ISO and CEN. SIS Publishing (SIS Forlag AB) publishes, markets and sells Swedish standards. Standards begin with the prefix SS or, if the standard was written prior to 1978, SIS. More than 95% of all new Swedish standards are based on international (global or European), and the prefix will then be SS-ISO or SS-EN.

Tel: 41 1 254 54 54 Fax: 41 1 254 54 74 e-mail: [email protected] Internet: www.snv.ch

The division of Schweizerische Normen-Vereinigung (SNV) that deals with the metals industry is Verein Schweizerischer Maschinen-Industrieller (VSM). These two organizations now share a joint address and Web site under the name SWISSMEM. More information on Swiss metals standards can be obtained by contacting VSM at Kirchenweg 4, 8032 Zurich, Switzerland, telephone 41 (01) 384 41 11, fax 41 (01) 384 42 42, email [email protected], or internet www.swissmem.ch.

Pan America Pan American Standards Commission (COPANT) Avenida Andres Bello, Torre Fondo Comun Piso 11 Caracas 1050 Venezuela

Switzerland Schweizerische Normen-Vereinigung (SNV) Mnhlebachstrasse 54 8008 Zurich Switzerland

(continued)

294 / Titanium: A Technical Guide Table D.2

(continued)

Organization and address

Contact information

Description

Turkey Turk Standardlari Enstitusu (TSE) (Turkish Standardization Institute) Necatibey Cad. 112 06100 Bakanliklar, Ankara Turkey

Tel: 90 312 417 83 30 Fax: 90 312 425 43 99 e-mail: [email protected] Internet: www.tse.org.tr

The Turkish Standards Institution (TSE) is a nongovernment state agency dedicated to the preparation and publication of standards. TSE is also a member of the ISO and affiliate member of CEN. The prefix for Turkish Standards are the letters TS which are followed by a code number or, in the case of a designation, an alphanumeric code.

United Kingdom British Standards Institution (BSI) British Standards House 389 Chadwick High Road London W4 4Al United Kingdom

Tel: 44 (0) 181 996 9000 Fax: 44 (0) 181 996 7400 e-mail: [email protected] Internet: www.bsi.org.uk

Develops and publishes standards that are used extensively by exporters and importers. They are used both in government and industry by those involved in engineering, designing, production, testing, and construction. BSI represents the British industry to the ISO, IEC, CEN, and CENELEC. These bodies develop the international and European standards. The letters BS precede the numerical code of the standard and may also include the designation of the alloy.

Tel: 381 11 361 31 50 Fax: 381 11 361 73 41 e-mail: [email protected]

The Yugoslavian Standardization Institute (SZS) is concerned with the adoption and application of standards. Yugoslavian standards begin with the prefix JUS, which is followed by an alphanumeric code. The first letter of the code denotes the section under which the standard is classified. Most standards relating to metallurgy are in section C.

Yugoslavia Savezni Zavod za Standardizaciju (SZS) (Yugoslavian Standardization Institute) Kneza Milosa 20 Post Pregr. 933 11000 Beograd Yugoslavia

Titanium: A Technical Guide Matthew J. Donachie, Jr., p295-306 DOI:10.1361/tatg2000p295

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Appendix E

Selected Manufacturers, Suppliers, Services THIS APPENDIX is neither an endorsement of a product nor a recommendation of a specific trade association, manufacturer, company, or process. Regarding the organizations listed in this Appendix, it should be understood that names of organizations are often changed, and companies cease to exist owing to business mergers and so on. The best sources for current listings for product and service providers in the titanium industry are the trade associations listed in Table E.1. An alternate source is Thomas Register (Products & Services volume, titanium entry, current edition) or a search of the World Wide Web via appropriate search engines. Some warnings should be issued relative to Web searching:

• It may be difficult to narrow a search. Thousands of “hits” may appear.

• The same organization may appear in multiple “hits” in the results of a given search.

• Data provided on the Web are not guaran•

teed to be accurate. Errors are found frequently. E-mail addresses, links to other sites, and other information may no longer be active.

Table E.1

• Updates of Web sites are sometimes infrequent. Check the date for the last update, if possible; several years between updates have been noted.

Table E.2 lists member companies of the Titanium Information Group (TIG) as provided from and reproduced courtesy of TIG. It is current in the year 2000 and may be found on the TIG Web site or procured directly from TIG using the address given in Table E.1. Similar information is available from the International Titanium Association (ITA). It may be procured by accessing the ITA Web site or by contacting ITA at the address provided in Table E.1. Changes in company names, affiliations, business climate, and so on have made it difficult, if not impossible, to continue tracking the operations of business organizations engaged in titanium and titanium alloy production, manufacture, or service. If Web access is not available, trade organization contact is not desired, or response is unsatisfactory, Table E.3 is provided as a starting point. Table E.4 provides a listing of manufacturers and suppliers by their primary products or services lines.

Note that these lists may comprise only a partial listing and, therefore, are possibly incomplete. Further, relative to business listings, there is no guarantee that an individual company currently makes the particular form as listed. Additional services frequently offered by various companies have not been listed in Tables E.3 and E.4, but typically these areas are:

• • • • • • • • • • • • • • • • •

Research and development Alloy development Applications assistance Custom melting Analytical and testing Heat treating Sawing Shearing Plasma cutting Machining Chemical milling Sand, grit blasting Laser drilling, cutting Cold-, hot-working operations Custom welding Hot isostatic pressing and atomizing for powder metallurgy Cold, hot isostatic pressing

Titanium trade (information) associations

Association and address

Titanium Information Group 5, The Lea Kidderminster, DY11 6JY UK International Titanium Association 350 Interlocken Boulevard Suite 390 Broomfield, CO 80021-3485 USA Japan Titanium Society 22-9 Kanda Nishiki-Cho Chiyoka-Ku, Tokyo ZIP 101 Japan

Contact information

Trevor J. Glover, Secretary Tel: +44 (0) 1562 60276 Fax: +44 (0) 1562 824851 e-mail: [email protected] Internet: www.titaniuminfogroup.co.uk Brian Simpson, Executive Director Tel: 303-404-2221 Fax: 303-404-9111 e-mail: [email protected] Internet: www.titanium.org Tel: 081 (3) 3293 5958 Fax: 081 (3) 3293 6187 Internet: www.titan-japan.com

Association and address

Titanium Technology Forum Institute for Energy Technology P.O. Box 40 N-2007 Kjeller Norway

Contact information

Liv Lunde, Head Dept. of Materials and Corrosion Tel: 47 63 80 62 65 Fax: 47 63 81 11 68 e-mail: [email protected] or Marion Seiersten, Sr. Research Scientist Dept. of Materials and Corrosion

Tel: 47 63 80 62 67 Fax: 47 63 80 62 58 e-mail: [email protected]

296 / Titanium: A Technical Guide

Table E.2

Associates of the Titanium Information Group

Associate and address

Contact information

Products and/or services description

Timet UK Limited P.O. Box 704 Witton Birmingham B6 7UR

Simon Dutta Tel: +44 (0) 121 356 1155 Fax: +44 (0) 121 356 5413 Internet: www.timet.com

Manufacturer and stockist of titanium mill products

Doncasters PLC 28-30 Derby Road Melbourne Derby DE73 1 FE

Peter Bridges Tel: +44 (0) 1332 864900 Fax: +44 (0) 1332 864888 e-mail: [email protected] Internet: www.doncasters.com

Manufacturer of titanium forgings and castings. Specialist fabricator including superplastic forming/diffusion bonding

Wyman Gordon Ltd Houston Road Livingston West Lothian EH54 5BZ

Douglas Armet Tel: +44 (0) 1506 446200 Fax: +44 (0) 1506 446330

Manufacturer of large titanium forgings including large diameter extruded pipe

Aerospace Forgings Ltd Churchbridge Road Oldbury, Warley West Midlands B69 2AU

Kevin Woodbine Tel: +44 (0) 121 552 2921 Fax: +44 (0) 121 544 5731

Manufacturer of closed die and hand-forged titanium forgings

TWI Limited Granby Park Great Abington Cambridge CB1 6AL

Philip Threadgill Tel: +44 (0) 1223 891162 Fax: +44 (0) 1223 892588 e-mail: [email protected] Internet: www.twi.co.uk

Research, development, and consultancy on joining techniques for materials including titanium

Metal Improvements Co Inc. Navigation House Hambridge Lane Newbury Berkshire RG14 STU

Peter O’Hara Tel: +44 (0) 1635 31071 Fax: +44 (0) 1635 31474

Surface treatment of titanium components to improve mechanical properties and to prolong service life

Orchard Cottage Back Lane Shenstone Kidderminster Worcestershire DY10 4DW

Ray Portman Tel: +44 (0) 1562 777432 Fax: +44 (0) 1562 777825 e-mail: [email protected] Internet: www.yell.co.uk/sites/rayportman

Designer, consultant on fabrication and procurement of titanium components

RTI International Metals Ltd Riverside Estate Fazeley Tamworth Staffordshire B78 3RW

David Hall Tel:+44 (0) 1827 262266 Fax: +44 (0) 1827 262267

Manufacturer and stockist of a full range of titanium mill products including piping and OCTG tubulars

VSMPO Tirus Unit 8 The Quadrangle Abbey Park Romsey, Hants S051 9AQ

Brent Barnes Tel: +44 (0) 1794 514888, Fax: +44 (0) 1794 514145

Stockist of titanium mill products

Aurora Forgings Ltd Parkgate Steelworks P.O. Box 16 Rotherham South Yorkshire S62 6EB

Ken Wrigley Tel: +44 (0) 114 261 5000 Fax: +44 (0) 114 261 5025 e-mail: [email protected] Internet: www.ani-aurora.com

Open and closed die forgings, extrusions, and rolled rings

Euro-Titan Handels A-G Katternberger Strasse 155-159 Solingen 426455 Germany

Dietmar Fischer Tel: +49 (0) 201 188 2593 Fax: +49 (0) 201 188 3520

Stockist of titanium ingot, bar, plate, sheet, profile, tube, and wire products

Rolls Laval P.O. Box 100 Wolverhampton WV4 6JY

Steve Sproson Tel: +44 (0) 1902 353353 Fax: +44 (0) 1902 403334 e-mail: [email protected]

Manufacturers of compact heat exchangers

SuperAlloys International Ltd 5 Garamonde Drive Clarendon Industrial Estate Wymbush Milton Keynes MK8 8DF

Martin Burnham Tel: +44 (0) 1908 260707 Fax: +44 (0) 1908 260404 e-mail: [email protected] Internet: www.superalloys.co.uk

Stockist of titanium wrought products

Sumitomo Corporation Europe Pic Vintners Place 68 Upper Thames Street London EC4V 3BJ

John Fryer Tel: +44 (0) 171 246 3737 Fax: +44 (0) 171 246 3953

Fabricator and international trader of titanium mill products and sponge

(continued)

Selected Manufacturers, Suppliers, Services / 297 Table E.2

(continued)

Associate and address

Contact information

Products and/or services description

D.E.R.A. Griffith Building (A7) Structural Materials Centre D.E.R.A. Farnborough Hampshire GU14 0LX

Professor Malcolm Ward-Close Tel: +44 (0) 1252 392540 Fax: +44 (0) 1252 397303 e-mail: [email protected] Internet: www.dera.gov.uk

Research and development on materials including titanium

Bunting Special Metals Ltd. 34 Middlemore Industrial Estate Smethwick, Warley West Midlands B66 2EE

Peter Hesketh Tel: +44 (0) 121 558 5814 Fax: +44 (0) 121 558 8072

Titanium fabricator specializing in pipe spools and manufacturer of a range of titanium valves

Oremet-Wah Chang c/o Titanium International Ltd. Keys House Granby Avenue Garretts Green Birmingham B33 0SP

Nick Aston Tel: +44 (0) 121 789 8030 Fax: +44 (0) 121 784 8054

Manufacturer and stockist of titanium mill products and castings

Rolls Royce Plc P.O. Box 2000 Derby DE21 7XX

John Fowler Tel: +44 (0) 1332 661461 Fax: +44 (0) 1332 622948

Fabrication and design of components for marine power systems

TECVAC Ltd. Buckingway Business Park Swavesey Cambridge CB4 5UG

Rhod Turner Tel: +44 (0) 1954 233700 Fax: +44 (0) 1954 233733 e-mail: [email protected]

All types of heat treatment, hard coatings, and ion implantation

ALBA AS Lilleakerveien 23 0283 OSLO

Jan Erik Thoresen Tel: 00 47 22500020 Fax: 00 47 22500111 e-mail: [email protected] Internet: www.alba.no

Titanium castings

Titanium Mill Products Ltd. Lowe House 1 Ranmoor Crescent Sheffield S10 3GU

Bernd Klein Tel: +44 (0) 1142 308 855 Fax: +44 (0) 1142 302 832

Stockists of titanium wrought products

Deutsche Titan GmbH Altendorfer Strasse 104 45143 Essen Germany

Dietmar Fischer Tel: 00 49 0201 188 2593 Fax: 00 49 0201 188 2593

Manufacturers of a wide range of titanium mill products

Allvac Limited Atlas House Attercliffe Road Sheffield S4 7UY

Terry Dockerty Tel: 00 44 (0) 114 2720081 Fax: 00 44 (0) 114 2731673

Stockist of titanium mill products

Hanseatische Waren Handelsgesellschaft GmbH Postfach 10 50 24 D-28050 Bremen Germany

Robert Hempel Tel: 00 49 (0) 421 16227-0 Fax: 00 49 (0) 421 12056

Converter of titanium ingot to mill products including bar, forgings, and rings

Tetronics 5 Lechlade Road Faringdon Oxfordshire SN8 9AJ

Dr. Tim Johnson Tel: 00 44 (0) 1367 240224 Fax: 00 44 (0) 1367 241445

Manufacturers of titanium melting equipment

Materials Information Service Institute of Materials 1 Carlton House Terrace London SW1Y 5DB

David Arthur Tel: 00 44 (0) 207 4517300 Fax: 00 44 (0) 207 8395513

Advisory service on engineering materials

Titanium Marketing & Advisory Services 5 the Barnsway Kings Langley Hertfordshire WD4 9PW

David Peacock Tel: 00 44 (0) 1923 269564 Fax: 00 44 (0) 1923 269564 e-mail: [email protected]

Consultant on corrosion and engineering with titanium

Aeromet International Pic Watchmead Welwyn Garden City Hertfordshire AL7 ILT

Robert Vickers Tel: 00 44 (0) 1795 415000 Fax: 00 44 (0) 1795 415050

Fabricator specializing in superplastic forming and diffusion bonding

Maher Limited Superalloys Edward Street Sheffield S3 7GD

Graham Franklin Tel: 00 44 (0) 114 290 9212 Fax: 00 44 (0) 114 290 9290 e-mail: [email protected]

Stockist of titanium mill products

(continued)

298 / Titanium: A Technical Guide Table E.2

(continued)

Associate and address

Contact information

Products and/or services description

Akso Nobel Permascand AB Box 42 S-840 10 Ljungaverk Sweden

Anders Hagstom Tel: 00 46 (0) 691 35500 Fax: 00 46 (0) 691 33040

Fabricator and stockist of mill products and a supplier of castings

AirCo Metals Limited Falcon Business Park Ivanhoe Road, Hogwood Lane Estate Finchampstead, Berks RG40 RQQ

Bob Rowles Tel: 00 44 (0) 118 973 0509 Fax: 00 44 (0) 118 973 1031

Stockist of mill products and other metals for aerospace and corrosion environments

Northern Special Metal (Fabricators) Ltd. Unit 5, Waleswood Industrial Estate Mansfield Road, Waleswood Sheffield S26 5PY

Brian Mason Tel: 00 44 (0) 1909 770799 Fax: 00 44 (0) 1909 515032 e-mail: [email protected]

Fabricator in titanium and special metals

International Titanium Association 350 Interlocken Boulevard, Suite 390 Broomfield, CO 80021-3485

Brian Simpson Tel: 303-404-2221 Fax: 303-404-9111 Internet: www.titanium.org

Trade association

Titanium Technology Forum Institute for Energy Technology P.O. Box 40 N-2007 Kjeller Norway Marine Corrosion Club

Marion Seirsten Tel: 47 63 80 62 67 Fax: 47 63 80 62 58 e-mail: [email protected]

A forum for information in titanium and exchange of information between member companies. The forum maintains a database on titanium publications and passes on information on titanium to the members. Alone, or in cooperation with others (mainly the Titanium Information Group), TTF makes designers’ and users’ handbooks.

Variable, may change each year. Consult Web site for latest information. Internet: www.marinecorrosionclub.org.uk

A forum for discussion of materials and corrosion matters relevant to the marine and offshore and associated industries. Occasional titanium information

Table E.3

Manufacturers, suppliers, services

Company and address

Contact information

A-1 Alloys 1401 Cleveland Ave. National City, CA 91950

Tel: 800-266-2569 Fax: 619-474-3276

Titanium, all shapes and sizes: tubing, foil, wire mesh, grating; fabrication and manufacturing

Products and/or services description

AAA Metals Co., Inc. 68 Industrial Blvd. Hanson, MA 02341-1547

Tel: 781-447-1220 Fax: 781-447-0899

…

Advanced Alloys Inc. 9852 Crescent Center Dr. Unit 802 Cucamonga, CA 91730

Tel: 800-521-1661 Fax: 909-980-4806

Titanium sheet, plate, bars, billet, wire, tubing and pipe, forged shapes, rolled rings. Certified to AMS, MIL, QQS, QQA, ASTM, GE, DMS, EMS, and PWA

Advanced Alloys, Inc. 1014 Grand Blvd. Deer Park, NY 11729

Tel: 800-645-1462 Fax: 631-595-7030

Titanium alloys: sheet, plate, bars, billet, wire, tubing and pipe, forged shapes, rolled rings. Certified to AMS, MIL, QQS, QQA, ASTM, GE, DMS, EMS, and PWA

Aerodyne Ulbrich Alloys, Inc. 125 S. Satellite Rd. South Windsor, CT 06074

Tel: 888-244-8642 Fax: 860-289-2841

Supplier of titanium bars, plate, and sheet. Water jet cutting and plate sawing, precision shearing, and precision sawing specialists

Aero Specialties Materials Corp. 20 Burt Dr. Deer Park, NY 11729

Tel: 800-645-9530 631-242-7200 Fax: 631-242-7652

ISO 9002, full-line center. Inventory of sheet, plates, bars, tubing, forgings

Aerotech Industries P.O. Box 2186 St. James, NY 11780-2186

Tel: 800-725-6556 Fax: 631-584-8203

Specialists in nonstandard items, including titanium bars, rods, wire, forgings, tubing/pipes, plates, sheets, fittings to ASM, MIL, ASTM, QQ-S, ASME, and corporate specifications

All-Chemie, Ltd. 501-D La Mesa Rd. Mount Pleasant, SC 29464

Tel: 843-884-4400 Fax: 843-884-0560

…

Allegheny Rodney Strip Div. 1357 E. Rodney French Blvd. P.O. Box 6915 New Bedford, MA 02742

Tel: 800-927-0398 Fax: 847-676-5909

All Metal Sales, Inc. 1260 Moore Rd. Avon, OH 44011

Tel: 888-333-0101 Fax: 888-333-0017

Producer and distributor of stainless steel, high-tech alloys, electronic alloys, and titanium engineered strip and foil products. Extensive range of specialty metals. Production capabilities: coil coating services, oscillate winding, tension leveling, conditioned edges, cut-tolength, and special finished. Technical support and just-in-time programs Metals distributor of every size, type, and form. Low minimums through mill runs of everyday materials. Supplier of nonstandard items just in time. Slitting, shearing, sawing, grinding, and cutting (continued)

Selected Manufacturers, Suppliers, Services / 299 Table E.3

(continued)

Company and address

Contact information

Alloy Fabricators, Inc. 102 S. Industrial Dr. Trenton, GA 30752

Tel: 800-275-7565 Fax: 706-657-4777

Custom fabrications, ASME code tanks, pressure vessels, columns, and reactors

Products and/or services description

Alloys International, Inc. (Aii) 85-J. S. Hoffman Ln. Islandia, NY 11749

Tel: 631-342-0043 Fax: 631-342-0051

Conversion and supply of metals for critical performance alloys for high-strength, high-temperature, and corrosion resistance. Aerospace, nuclear, and medical. Difficult sizes and specifications

Allvac P.O. Box 5030 Monroe, NC 28111-5030

Tel: 704-289-4511 Fax: 704-289-4018

…

Altemp Alloys, Inc. 1630 S. Sunkist St. Anaheim, CA 92806

Tel: 800-959-0904 Fax: 714-938-0971

Warehouse and mill production specializing in high-temperature and exotic alloys, including titanium-base alloys. Complete service center offering sheet, plate, bar, forgings, and precision shearing

American Aerospace Materials 665 Monterey Pass Rd. Monterey Park, CA 91754-2418

Tel: 626-281-7075 Fax: 626-281-4321

Distributor of titanium sheet, plate, coil, rod, bar. Aerospace specialists. Leveling, slitting, sawing, precision planning, heat treating, shearing, certification

AmeriCana Metal Service, Inc. 7913 Plainfield Rd. Cincinnati, OH 45236-2503

Tel: 800-932-9444 Fax: 513-984-9005

Full-line metals distributor specializing in hard-to-obtain materials, bar, casting, forgings, plate, shapes, sheet, tube

AstroCosmos Metallurgical, Inc. 3225 W. Old Lincoln Way Wooster, OH 44691-1229

Tel: 888-402-7876 Fax: 330-264-4316

Same day shipping of titanium sheet, plate, bar, pipe, fittings, fasteners. Full-service fabrications, machining, welding, and design also available

Astrolite Alloys Div. of AstroCosmos Metallurgical, Inc. 1201 Vanguard Dr. Oxnard, CA 93033

Tel: 888-278-7644 Fax: 805-487-9694

ISO 9002 welding wire for aerospace and industrial applications; titanium drawing, annealing

Atlantic Equipment Engineers A Div. of Micron Metals, Inc. 13 Foster St. P.O. Box 181 Bergenfield, NJ 07621

Tel: 201-384-5606 Fax: 201-387-0291

High-purity metals, metal powders and compounds, oxides, borides and silicides, nitrides, and carbides. Wide range of purities and particle sizes

Atlantic Stainless Co., Inc. 140 John L. Dietsch Sq. North Attleboro, MA 02763

Tel: 800-876-2700 Fax: 508-699-8311

Titanium in bar, plate, pipe, tubing, angle, and other shapes; all sizes and lengths. Plasma burning to 3 in., shearing up to 3/8 in. and 12 ft long, saw cutting up to 17 in. in diam, and fabrications

Atomergic Chemetals Corp. 222 Sherwood Ave. Farmingdale, NY 11735-1718

Tel: 631-694-9000 Fax: 631-694-9177

Crystal bar and sponge 99.9%

B & L Metals, Inc. 200 E. Second St., Suite 39 Huntington Station, NY 11746

Tel: 800-216-2494 Fax: 631-421-6178

Titanium bar, sheet, plate, pipe, tubing, wire, forgings

Belmont Metals Inc. 320 Belmont Ave. Brooklyn, NY 11207-4000

Tel: 718-342-4900 Fax: 718-342-0175

Metallic, commercially pure grade, 96% minimum. Clips, powder, turnings; metallurgical assistance in product selection and application;titanium shapes, quantities, titanium aluminum, titanium copper

B & S Aircraft Alloys, Inc. 110 Aerial Way Syosset, NY 11791

Tel: 800-645-2401 Fax: 516-681-2439

Full-service center, LCS approved, ISO 9002 compliant, all specifications; export specialists. Titanium and hard-to-find items, sheet, plate, bar, tube, pipe fittings, forgings, fabrications

California Fine Wire Co. 338-40 S. Fourth St. P.O. Box 446 Grover Beach, CA 93483

Tel: 805-489-5144 Fax: 805-489-5352

Titanium and titanium alloys, 0.0008 in. and larger, spooled or cut to length, ribbon, square, sheets, and special shapes, for aerospace, military/defense, medical, and other electronic instrumentation and applications

Cast Alloys Inc. 703 Palomar Airport Rd., Suite 260 Carlsbad, CA 92009-1040

Tel: 760-603-8282 Fax: 760-603-7667

Titanium alloy castings

Coastcast Corp. P.O. Box 9076 Rancho Dominguez, CA 90224

Tel: 310-532-2060 Fax: 310-532-9341

Manufacturer of titanium products

Coltwell Industries 55 Winans Ave. Cranford, NJ 07016

Tel: 908-276-7600 Fax: 908-276-2679

Titanium for aircraft and aerospace industries

(continued)

300 / Titanium: A Technical Guide Table E.3

(continued)

Company and address

Contact information

Products and/or services description

Complete Metalworks Corp. 5 Acorn P.O. Box 803 Highland Lakes, NJ 07422

Tel: 973-764-1800 Fax: 973-764-1804

Open die forgings of titanium

Crucible Research A Div. of Crucible Materials Corp. 6003 Campbells Run Rd. Pittsburgh, PA 15205-1022

Tel: 412-923-2955 Fax: 412-788-4665

Manufacturers of specialized powdered metals by inert gas atomizers for iron, nickel base superalloys, titanium, and stainless steel. P/M research and development

CSM Industries Inc. 21803 Tungsten Rd. Cleveland, OH 44117

Tel: 800-692-4416 Fax: 216-692-0029

Titanium extrusions; 5500 ton press extrudes rounds, rectangles, solids, tubing, back extrusions

DiamondTel Steel 99 Mt. Bethel Rd. Warren, NJ 07059-5645

Tel: 800-805-9080 Fax: 908-769-7850

Titanium plate, bar, sheet, tubing, pipe, shapes

Diversified Industrial Products Corp. 40 Skyline Dr. Plainview, NY 11803

Tel: 800-822-5461 Fax: 800-822-5469

Standard and hard-to-find metals: bars, extrusions, foils, forgings, plates, shapes, sheets, strips, tubes, and wire. MIL-I-45208A standards

Diversified Metals, Inc. 49 Main St., P.O. Box 65 Monson, MA 01057-0065

Tel: 888-618-9779 Fax: 413-267-3151

Titanium rod, bar, wire, sheets, plates, tubing, extruded shapes, forgings

Dynamet, Inc., A Carpenter Co. 195 Museum Rd. Washington, PA 15301

Tel: 724-228-1000 Fax: 724-229-4195

Manufacturer and distributor of titanium coil, bar, fine wire, engineered shapes, and powder products. Supplier of exacting titanium alloy products: aerospace, medical, sports, and other industries

Dynamet Technology, Inc. 8 A St. Burlington, MA 01803-3405

Tel: 781-272-5967 Fax: 781-229-4879

P/M parts, preforms including isostatic pressing

Eagle Alloys Corp. 105 S.W. 39th Pl. Cape Coral, FL 33991

Tel: 800-237-9012 Fax: 423-586-7456

Titanium alloy bars, blocks, coil, extrusions, forgings, plate, rod, sheet, strip, tubes, wire

Ed Fagan, Inc. 769 Susquehanna Ave. Franklin Lakes, NJ 07417

Tel: 800-348-6268 Fax: 201-891-3207

Commercially pure grades 1, 2, and 3. Alloy 6Al4V. Mill forms from stock sheet, plate, rod, and strip. Specialist to the aerospace, medical, and electronic industries

Elgiloy Specialty Metals 11777 Bee St. Dallas, TX 75234

Tel: 888-403-2091 Fax: 972-247-2243

Source for high-quality alloys

Ellett Industries, Ltd. 1575 Kingsway Ave. Port Coquitlam BC V3C4E5 Canada

Tel: 604-941-8211 Fax: 604-941-7669

Worldwide designers and fabricators of heat- and corrosion-resistant process equipment including heat exchangers, towers, reactors, and tanks. Metals inventory includes titanium. Meets all ASME, ASTM, TEMA, and API standards and codes

Excelco Developments, Inc. 4274 Mill St. Silver Creek, NY 14136-0230

Tel: 716-934-2651 Fax: 716-934-2646

Titanium: machining, fabrication, welding, NDE and testing for high-tech applications such as nuclear, aerospace, and seawater; ISO-9001/Mil specifications

Express Metals Co. 5583 Parkmor Rd. Calabasas, CA 91302-1034

Tel: 800-555-4202 Fax: 818-880-1542

Titanium sheet, plate, bar, forgings, weldwire, and tubing in commercially pure and alloyed grades. All material certified to AMS, MIL, DMS, and ASTM specifications

Extrusion Technology Corp. of America 6130 Cochran Rd. Solon, OH 44139

Tel: 888-557-0305 Fax: 440-498-0519

Manufacturer of titanium in special shapes, bars, and hollows, produced by 5000 and 1800 ton presses. Shapes that fit within a 14 in. diam circle

Falcon Stainless & Alloys Corp. 39 Hewson Ave. Waldwick, NJ 07463

Tel: 888-814-5631 Fax: 888-853-5027 201-670-6461

Titanium, all forms: coil/foil, sheet; plate; bar; shapes; tube; pipe and fittings; forgings; flat, shaped, and round wire; cutting; polishing; edging; and expanding

Ferguson Metals, Inc. Dept. 82, 3475 Symmes Rd. Hamilton, OH 45015

Tel: 800-347-2376 Fax: 513-874-6857

Titanium alloys in sheet, strip, coil, plate, and bar

Fort Wayne Metals Research Products Corp. 9609 Indianapolis Rd. P.O. Box 9040 Fort Wayne, IN 46809-9625

Tel: 219-747-4154 Fax: 219-747-0398

Manufacturer of titanium alloys in round wire, flat wire, strands and cables, for the medical industry and other applications. Diameters 0.001 to 0.109 in.

(continued)

Selected Manufacturers, Suppliers, Services / 301 Table E.3

(continued)

Company and address

Contact information

Products and/or services description

FPD Company 124 Hidden Valley Rd. McMurray, PA 15317

Tel: 724-941-5540 Fax: 724-941-8322

G & S Titanium, Inc. 1550 Spruce St. Ext. Wooster, OH 44691

Tel: 800-860-0564 Fax: 330-262-1550

General Titanium Inc./BIAM 9645 Telstar Ave. El Monte, CA 91731

Tel: 888-606-2426 Fax: 626-575-6558

Global Titanium, Inc. 19300 Filer Ave. Detroit, MI 48234-2881

Tel: 313-366-5300 Fax: 313-366-5305

Great Lakes Alloys Inc. 645 N. Michigan Ave., Suite 800 Chicago, IL 60611

Tel: 312-649-0470 Fax: 312-649-1796

Harvey Titanium Ltd. 1330 Colorado Ave. Santa Monica, CA 90404

Tel: 310-664-0040 Fax: 310-664-1961

IMI Titanium, Inc. 4000 W. Valley Blvd. Pomona, CA 91769

Tel: 909-595-7455 Fax: 909-598-3005

Titanium castings for the aerospace, marine, and chemical process industries

Industrial Metals International, Ltd. 2065 Fifth Ave. Ronkonkoma, NY 11779-6905

Tel: 631-981-1300 Fax: 631-981-1339

Interstate Metals 66 S. Second St. Bay Shore, NY 11706

Tel: 888-300-8053 Fax: 631-242-9561

Titanium grades available in bar, sheet, tube, forgings, extrusions, rolled rings. Just-in-time delivery. Special cutting and heat treating. Custom export packing. Daily shipments to airports and seaports. Technical staff Titanium bar, plate, sheet, and tubing. Specialty metals and forgings. Serving aerospace, military, chemical, electronic, and marine industries. Specializing in hard-to-find items

KPK Stainless 341 Owen Ave. Fair Lawn, NJ 07410

Tel: 800-374-6575 Fax: 201-797-4485

Titanium ion plated super No. 8 mirror prefinished

LauBeck Corp. P.O. Drawer 507 Carbondale, PA 18407

Tel: 800-872-7373 Fax: 800-232-9737

Manufacturers of all perforated metals for industrial, mining, and screening applications. Over 200 stock items; over 2000 tools for custom perforating and fabrication; all holes and shapes; foil to 1½ in. thick

Material Net 170 Great Neck Rd. Great Neck, NY 11021

Tel: 516-504-1830 Fax: 516-504-1826

Metal Cutting Corp. 89 Commerce Rd. Cedar Grove, NJ 07009

Tel: 800-783-6382 Fax: 973-239-6651

E-commerce service for metals buyers, buyer-driven metals marketplace. Submit RFQ to receive bids for metal needs. “Reverse auction” with over 150 industrial metals suppliers. Tracks orders shipment to delivery. Secure site Burr-free abrasive cutting, grinding, lapping, and polishing of all small diam metal tubes, wire, and rods to precision tolerances, lengths, parallelism, flatness, squareness, and surface finished

Metalmart, Inc./Mark Metals 12225 Coast Dr. Whittier, CA 90601

Tel: 800-888-7766 Fax: 562-699-6868

Distributor of 6Al-4V, commercially pure, and ELI grades, sheets, plates, bars, forgings, tubing

Metalmen Sales, Inc. 31-29 Twelfth St. Long Island City, NY 11106

Tel: 800-767-9494 Fax: 718-204-1703

Stocking distributor of titanium. Temper rolling, slitting, cutting, edging, polishing, gage reduction, specialty processing

Metalpure LLC 240 N. Church Rd. Hardyston, NJ 07460

Tel: 973-328-3228

High-purity and commercial grade alloys, 99.99%; iodide crystal bar, billet, powder, sheet, rod

Metalsource, Inc. 2726 Kanasita Dr. Chattanooga, TN 37343

Tel: 800-487-6382 Fax: 423-870-7800

Titanium tubing, grinding, milling, turning burnouts, blanchard-surface, centerless grinding, cut pieces; no minimum

Metal Technology, Inc. 173 Queen Ave., S.E. Albany, OR 97321

Tel: 800-394-9979 Fax: 541-928-0596

MSC Industrial Supply Co. 75 Maxess Rd. Melville, NY 11747-3151

Tel: 800-753-7937 Fax: 800-255-5067

Precision manufacturer of machined and deep draw formed titanium components and assemblies. Products include seamless nozzles, vessels, tubing, cones, hemispheres, and aerospace components; QA conforms to MIL-1-45208, MIL-Q-9858, and others Supplier of 372,000 products from 1900 manufacturers: cutting, machine, hand, power tools; MRO supplies, abrasives, fasteners, precision instruments, machinery, electrical supplies, safety equipment, HVAC, welding, hose, tubing, fittings, material handling, pumps, power transmission; janitorial; same day shipping

Precision forging, high-speed machining, sintering, finishing, and advanced engineering for aerospace, medical, and recreational marketings. Specializing in titanium, stainless steel, cobalt chrome, aluminum Manufacturer of custom sizes and shapes from 0.005 to 3 in. diam for aerospace, medical, nuclear, orthodontic, and petrochemical applications. Inhouse annealing, acid cleaning, salt descaling, and fabrication Manufacturer of titanium castings for aerospace and industrial; precision titanium forgings for aircraft, orthopedics, and industrial; titanium-gold coatings for hardware, building furnishings, and cutting tools Titanium metallurgical products; ferrotitanium

Titanium castings

…

(continued)

302 / Titanium: A Technical Guide Table E.3

(continued)

Company and address

Contact information

Products and/or services description

National Electronic Alloys 5 Fir Ct. Oakland, NJ 07436

Tel: 201-337-9400 Fax: 201-337-9698

Alloys from stock for electronics and aerospace

National Speciality Alloys, Inc. 1320 Upland Houston, TX 77043-4719

Tel: 888-419-7701 Fax: 713-467-5959

Bar, rod, shapes, pipe, tubing. Precision grinding and other services

Oremet-Wah Chang, An Allegheny-Teledyne Co. 1600 N.E. Old Salem Rd. P.O. Box 460 Albany, OR 97321-0460

Tel: 541-967-6977 Fax: 541-967-6994

Producer of titanium and its alloys in high-purity bar stock, sheet and plate, wire, tube and pipe, and powders. Produces NiTi, Tiadyne 3515, Ti-45Nb, Ti3Al12.5V, Ti6-2-4-2, Ti-1270, and TiNb alloys

The Perryman Co. 213 Vandale Dr. Houston, PA 15342

Tel: 724-746-9390 Fax: 724-746-9392

Titanium products: wire, bar, fine wire, and titanium drawn net shapes

Plymouth Extruded Shapes A Member of The Plymouth Tube Co. 201Commerce Ct. Hopkinsville, KY 42240

Tel: 800-718-7590 Fax: 270-886-6662

Titanium extruded shapes and hollow products produced by 2000 ton press

Precision Shapes, Inc. 8835 Grissom Pky., P.O. Box 5099 Titusville, FL 32783-5099

Tel: 321-269-2555 Fax: 321-267-6719

Continuous millings in any lengths of intricate shapes on all metals, standard extrusions, and bar stock milled to close tolerances, milling shapes into strip stock, secondary operations, and assembly of finished parts

President Titanium 243 Franklin St. Hanson, MA 02341-1506

Tel: 800-225-0304 Fax: 781-293-3753

All forms of titanium for commercial and aircraft applications

Rickard Specialty Metals & Engineeering Inc. 1707 S. Grove Ave. Ontario, CA 91761

Tel: 800-966-4922 Fax: 909-947-4909

Suppliers of titanium forgings, sheet, plate, bars, rods, and strips. All materials meet current AMS, MIL, ASTM, and other OEM specifications

RJ Enterprise, LLC 89 Common Rd. Willington, CT 06279

Tel: 800-277-9979 Fax: 860-429-0008

Supplier of all commercially pure and alloy grades of titanium in tube, pipe, bar, plate, sheet, coil, wire, shapes, to AMS, ASTM, military, and corporate specifications. Specializes in hard-to-find aerospace items

RMI Titanium Co. 1000 Warren Ave. Niles, OH 44446

Tel: 330-544-7633 Fax: 330-544-7796

Producer of titanium and titanium alloys in sheets, strip, ingots, plates

SAES Getterrs/U.S.A., Inc. 1122 E. Cheyenne Mountain Blvd. Colorado Springs, CO 80906

Tel: 719-576-3200 Fax: 719-576-5025

Ultrapure titanium films from Ti-Ta wire

Sandvik Special Metals Corp. P.O. Box 6027 Kennewick, WA 99336-0027

Tel: 509-586-4131 Fax: 509-582-3552

Titanium tubing for aerospace, chemical, and nuclear process industries

Servi-Sure Corp. 2020 W. Rascher Ave. Chicago, IL 60625

Tel: 773-271-5900 Fax: 773-271-3777

Manufacturers of titanium fasteners

Sierra Alloys Co., Inc. 5467 Ayon Ave. Irwindale, CA 91706

Tel: 800-423-1897 Fax: 626-969-6719

Specializing in on-site open die forgings and hot-rolling titanium alloys etc. Comprehensive ingot/billet inventory. Forged bar, block and slabs, hand forgings, and hot-rolled bar

SMC Metal Inc. 620 S. State College Blvd. Fullerton, CA 92831

Tel: 714-738-8700 Fax: 714-738-8080

Distributor of metals for aerospace, military, and commercial applications, including titanium; available in all forms

Specialty Steel & Forge, Inc. 26 Law Dr. Fairfield, NJ 07004-3293

Tel: 800-600-9290 Fax: 973-808-4488

Special hard-to-find alloys and obsolete grades and specifications. All mill forms (bar, sheet, plate, tube) and forged shapes and rolled seamless rings up to 200 in. diam, 5500 min, ISO 9002, SGS-94-3136

Sterling Aircraft Materials Ltd. 157 Keyland Ct. Bohemia, NY 11716

Tel: 800-247-2410 Fax: 631-567-0236

Titanium, aircraft, and high-temperature alloys (sheet, plate, coil, tubing, round and flat bar, wire, rings, forgings). All material certified to government, MIL, AMS, ASTM, AISI, QQ, and corporate specifications

Superior Tube Co. 3900 Germantown Pike Collegeville, PA 19426-3112

Tel: 610-489-5200 Fax: 610-489-5252

Small diam precision metal tubing in over 45 analyses (stainless steels, nickels, nickel alloy, MP35N, titanium, and other reactive metals). In seamless forms, most analyses. Also in weld drawn form: 0.010 to 0.750 in. OD (0.218 in. max wall to 0.025 in.)

(continued)

Selected Manufacturers, Suppliers, Services / 303 Table E.3

(continued)

Company and address

Contact information

Products and/or services description

Supra Alloys, Inc. 351 Cortez Circle Camarillo, CA 93012-8630

Tel: 800-893-4450 Fax: 805-987-6492

Supplier of commercially pure and alloy titanium foil, sheet, and plate. Also seamless and welded commercially pure titanium pipe and tube for industrial and aerospace applications

Talbot Associates, Inc. (TAI) 13 Cleveland Pl. Springfield, NJ 07081

Tel: 800-376-9570 Fax: 973-376-7617

All casting processes for all metals

Tara Metals Inc. 227 Progress Dr. Manchester, CT 06040

Tel: 860-649-5711 Fax: 860-649-5333

Supplier of domestic raw materials including titanium available in bar, sheet, and plate. MIL 45208A, level 1-Navy, LCS, QSL approved; shearing and sawing services

TechSpec Inc. Y Street P.O. Box 69 Derry, PA 15627

Tel: 724-694-2716 Fax: 724-694-5305

Manufacturer of titanium and titanium alloy mill products

Textron Specialty Materials Sub. of Textron, Inc 2 Industrial Ave. Lowell, MA 01851

Tel: 978-452-8961 Fax: 978-454-5619

…

Textron Systems 201 Lowell St. Wilmington, MA 01887-2941

Tel: 978-657-2963 Fax: 978-657-2930

ISO 9001 registered manufacturer of advanced materials (fibers, preforms, prepegs) and composite structure. Silicon carbide fiber reinforced titanium composites

Tico Titanium, Inc. 52900 Grand River Ave. New Hudson, MI 48165

Tel: 248-446-0400 Fax: 248-446-1995

…

Titanium & Alloys Corp. 21601-A Hoover Rd. Warren, MI 48089

Tel: 810-755-1900 Fax: 810-755-5109

…

Titanium Distribution Services, Inc. 979 Oakcrest St. Brea, CA 92821

Tel: 877-751-1997 Fax: 877-843-0120

Titanium mill products including sheet, strip, plate, and bar

Titanium Fabrication Corp. 110 Lehigh Dr. Fairfield, NJ 07004

Tel: 973-227-5300 Fax: 973-227-6541

Titanium mill products; engineering and fabrication of titanium products including heat exchangers, piping systems, tanks, vessels

Titanium Finishing Co. 248 Main St. P.O. Drawer 22 East Greenville, PA 18041

Tel: 215-679-4182 Fax: 215-679-2399

High-technology metal finishing services

Titanium Hearth Technologies 900 Hemlock Rd. Morgantown Business Park Morgantown, PA 19543

Tel: 610-286-6100 Fax: 610-286-3831

…

Titanium Hearth Technologies 403 Ryder St. Vallejo, CA 94590

Tel: 707-552-4850 Fax: 707-552-8320

…

Titanium Industries, Inc. 48 South St. Morristown, NJ 07960

Tel: 973-984-8200 Fax: 973-984-8206

Titanium Industries, Inc. 16030 S. Carmenita Rd. Cerritos, CA 90707

Tel: 562-802-2889 Fax: 562-404-8972

…

Titanium Ltd. Sub. of Titanium Fabrication Corp. 5055 Rue Levy Ville St. Laurent Quebec, PQ H4R 9N7 Canada

Tel: 514-334-5781 Fax: 514-334-3410

…

Titanium Metals Corp. (TIMET) 1999 Broadway, Suite 4300 Denver, CO 80202-5744

Tel: 303-296-5600 Fax: 303-296-5640

Fully integrated producer of titanium metal products

Titanium Metals Corp. W. Lake Mead & Atlantic Ave. P.O. Box 2128 Henderson, NV 89009

Tel: 702-564-2544 Fax: 702-564-1704

Fully integrated producer of titanium metal products

Distributor of alloy and commercially pure titanium including fasteners, fittings, piping systems, rings, shafts and agitators, titanium bar, rod, billets, foil, plate, sheet, slab strip, seamless tube, welded tube, wire

(continued)

304 / Titanium: A Technical Guide Table E.3

(continued)

Company and address

Contact information

Titanium Metals Corp. Central 46 N. Central Dr. O’Fallon, MO 63366

Tel: 636-272-2240 Fax: 636-272-2233

Fully integrated producer of titanium metal products

Titanium Metals Corp. East 7 Craftsman Rd. East Windsor, CT 06088

Tel: 860-627-7051 Fax: 860-627-8132

Fully integrated producer of titanium metal products

Titanium Metals Corp. Southwest 2910 Skyway Circle Irving, TX 75062

Tel: 972-273-6149 Fax: 972-273-6160

Fully integrated producer of titanium metal products

Titanium Metals Corp. West 14281 Franklin Ave. Tustin, CA 92780

Tel: 714-573-2666 Fax: 714-573-2777

Fully integrated producer of titanium metal products

Titanium Metals Corp., Northwest P.O. Box 908 Albany, OR 97321

Tel: 541-926-6162 Fax: 541-926-6164

Manufacturer and fully integrated producer of titanium metal products

Titanium Wire Corp. 235 Industrial Park Rd. Frackville, PA 17931-2703

Tel: 570-874-0311 Fax: 570-874-3198

…

Trans World Alloys 334 E. Gardena Blvd. Gardena, CA 90248

Tel: 888-208-8777 Fax: 310-217-0066

Tricor Industrial, Inc. 823 W. Bowman St. Wooster, OH 44691

Tel: 800-421-5141 Fax: 330-264-1181

Stocking warehouses and service centers of aluminum, titanium, stainless steel, and other alloys. Products sold are plate, sheet, bar, rounds, squares, rectangles, extrusions, and tube. Cut to size and just in time. Services and certifications to aerospace and commercial specifications International supplier of titanium. Extensive inventories include pipe, plate, sheet fittings, tubing, bar, expanded sheet, and fasteners in commercially pure titanium

Ulbrich Stainless Steels & Special Metals, Inc. 57 Dodge Ave. North Haven, CT 06473

Tel: 877-205-1332 Fax: 203-239-7479

Titanium and titanium alloys, bar, sheet, plate

United Titanium, Inc. 3434 Old Airport Rd. Wooster, OH 44691

Tel: 800-321-4938 Fax: 330-263-1336

Manufacturer of titanium fasteners and small fabrications; precision parts for aerospace, medical, and dental applications

U.S. Chrome Corp. 175 Garfield Ave. Stratford, CT 06615

Tel: 800-637-9019 Fax: 203-386-0067

Venture Metals Technology 22820 I-45 N, Suite 9-P Spring, TX 77373

Tel: 281-288-0023 Fax: 281-288-3424

Precision hard chromium, electroless nickel and nickel composites on wide variety of basis metals, including titanium, aircraft, aerospace, federal, military, space, FAA repair, grinding, honing, polishing, research and development facilities Titanium mill products precision cut to specifications. Fabrication and machine shops with full NDE and export capabilities. ASME certified U and R stamps

Vulcanium Metals International 3045 Commercial Ave. Northbrook, IL 60062

Tel: 888-326-7556 Fax: 847-498-2810

Western Titanium, Inc. 8830 Recho Rd., Suite A San Diego, CA 92121

Tel: 858-678-0990 Fax: 858-678-0880

Table E.4

Products and/or services description

Titanium mill products: sheet, plate, wire, bar, tube, pipe, fasteners in all grades and sizes. Inhouse metallurgical support and fabrication services: shearing, bending, cutting, CNC stamping, milling, deburring, inert gas welding, and custom fabrication …

Manufacturers and suppliers of titanium products by primary product(s) or service(s) line(s)

Bars Advanced Alloys Aerodyne Ulbrich Alloys, Inc. Aero Specialties Materials Corp. Aerotech Industries Altemp Alloys, Inc. American Aerospace Materials AmeriCana Metal Service, Inc. AstroCosmos Metallurgical, Inc. Atlantic Stainless Co., Inc. B & L Metals, Inc. B & S Aircraft Alloys, Inc. DiamondTel Steel Diversified Industrial Products Corp. Diversified Metals, Inc.

Bars (continued) Dynamet, Inc. Eagle Alloys Corp. Express Metals Co. Extrusion Technology Corp. of America Falcon Stainless & Alloys Corp. Ferguson Metals, Inc. Industrial Metals International, Ltd. Interstate Metals Metalmart, Inc./Mark Metals Metalpure LLC National Specialty Alloys, Inc. Oremet-Wah Chang The Perryman Co. Rickard Specialty Metals & Engineering, Inc. (continued)

Bars (continued) RJ Enterprise, LLC Specialty Steel & Forge, Inc. Sterling Aircraft Materials Ltd. Tara Metals, Inc. Titanium Distribution Services, Inc. Titanium Industries, Inc. Titanium Metals Corp. (TIMET) Trans World Alloys Tricor Industrial, Inc. Ulbrich Stainless Steels & Special Metals, Inc. Vulcanium Metals International Billets Advanced Alloys

Selected Manufacturers, Suppliers, Services / 305 Table E.4

(continued)

Billets (continued) Metalpure LLC Sierra Alloys Co., Inc. Titanium Industries, Inc. Titanium Metals Corp. (TIMET) Castings AAA Metals Co., Inc. A-1 Alloys Advanced Alloys All-Chemie, Ltd. Alloys International, Inc. (Aii) AmeriCana Metal Service, Inc. Cast Alloys, Inc. Coastcast Corp. General Titanium, Inc./BIAM Global Titanium, Inc. Great Lakes Alloys, Inc. IMI Titanium, Inc. National Speciality Alloys, Inc. Sierra Alloys Co., Inc. Talbot Associates, Inc. (TAI) Tico Titanium, Inc. TIMET Castings Corp. Coil A-1 Alloys Advanced Alloys Allegheny Rodney Strip Div. Alloys International, Inc. (Aii) Allvac American Aerospace Materials AstroCosmos Metallurgical, Inc. Astrolite Alloys Diversified Metals, Inc. Dynamet, Inc. Eagle Alloys Corp. Extrusion Technology Corp. of America Falcon Stainless & Alloys Corp. Ferguson Metals, Inc. G & S Titanium, Inc. National Electronic Alloys RJ Enterprise, LLC Sterling Aircraft Material Ltd. Supra Alloys Titanium Fabrication Corp. Titanium Hearth Technologies Titanium Metals Corp. (TIMET) Trans World Alloys Vulcanium Metals International Extrusions Aero Specialties Materials Corp. CSM Industries, Inc. Diversified Industrial Products Corp. Diversified Metals, Inc. Eagle Alloys Corp. Extrusion Technology Corp. of America Harvey Titanium Ltd. Industrial Metals International, Inc. Metal Technology, Inc. Plymouth Extruded Shapes Titanium Metals Corp. (TIMET) Trans World Alloys Fasteners AstroCosmos Metallurgical, Inc. MSC Industrial Supply Co. Servi-Sure Corp. Titanium Industries, Inc. Tricor Industrial, Inc. Vulcanium Metals International Foil A-1 Alloys Advanced Alloys Allegheny Rodney Strip Div. All-Chemie, Ltd All Metal Sales, Inc.

Foil (continued) Alloys International, Inc. (Aii) Elgiloy Specialty Metals Diversified Industrial Products Corp. Falcon Stainless & Alloys Corp. Supra Alloys, Inc. Titanium Industries, Inc. Forgings AAA Metals Col., Inc. Advanced Alloys Aero Specialties Materials Corp. Aerotech Industries Altemp Alloys, Inc. AmeriCana Metal Service, Inc. AstroCosmos Metallurgical, Inc. B & L Metals, Inc. B & S Aircraft Alloys, Inc. Cast Alloys Inc. Complete Metalworks Corp. Diversified Industrial Products Corp. Diversified Metals, Inc. Eagle Alloys Corp. Express Metals Co. Extrusion Technology Corp. of America Falcon Stainless & Alloys Corp. FPD Company General Titanium Inc./BIAM Industrial Metals International, Ltd. Interstate Metals Material Net Metalmart, Inc./Mark Metals Rickard Specialty Metals & Engineering, Inc. Sierra Alloys Co., Inc. Specialty Steel & Forge, Inc. Sterling Aircraft Materials Ltd. Titanium Metals Corp. (TIMET) Trans World Alloys United Titanium, Inc. Ores Extrusion Technology Corp. of America Global Titanium, Inc. Supra Alloys, Inc. Pipe Advanced Alloys AstroCosmos Metallurgical, Inc. B & L Metals, Inc. B & S Aircraft Alloys, Inc. DiamondTel Steel Falcon Stainless & Alloys Corp. Oremet-Wah Chang RJ Enterprise, LLC Supra Alloys, Inc. Titanium Fabrication Corp. Titanium Industries, Inc. Tricor Industrial, Inc. Vulcanium Metals International Plate Advanced Alloys Aerodyne Ulbrich Alloys, Inc. Aerotech Industries Altemp Alloys, Inc. American Aerospace Materials AmeriCana Metal Service, Inc. AstroCosmos Metallurgical, Inc. Atlantic Stainless Co., Inc. B & L Metals, Inc. B & S Aircraft Alloys, Inc. DiamondTel Steel Diversified Industrial Products Corp. Diversified Metals, Inc. Eagle Alloys Corp. Ed Fagan, Inc. Express Metals Co. Falcon Stainless & Alloys Corp. (continued)

Plate (continued) Ferguson Metals, Inc. Interstate Metals Metalmart, Inc./Mark Metals Oremet-Wah Chang Rickard Specialty Metals & Engineering, Inc. RJ Enterprise, LLC RMI Titanium Co. Specialty Steel & Forge, Inc. Sterling Aircraft Materials Ltd. Supra Alloys, Inc. Tara Metals, Inc. Titanium Distribution Services, Inc. Titanium Metals Corp. (TIMET) Trans World Alloys Tricor Industrial, Inc. Ulbrich Stainless Steels & Special Metals, Inc. Vulcanium Metals International Powders Atlantic Equipment Engineers Belmont Metals, Inc. Crucible Research Dynamet, Inc. Dynamet Technology, Inc. Metalpure LLC Rings Advanced Alloys Industrial Metals International, Ltd. Specialty Steel & Forge, Inc. Sterling Aircraft Materials Ltd. Titanium Industries, Inc. Rod A-1 Alloys AAA Metals Co. Inc. Advanced Alloys Aerodyne Ulbrich Alloys, Inc. Aero Specialties Materials Corp. Aerotech Industries All-Chemie, Ltd. All Metal Sales, Inc. Alloys International, Inc. (Aii) Allvac Altemp Alloys, Inc. American Aerospace Materials AmeriCana Metal Service, Inc. AstroCosmos Metallurgical, Inc. Astrolite Alloys Atlantic Equipment Engineers Atlantic Stainless Co., Inc. B & S Aircraft Alloys, Inc. Coltwell Industries DiamondTel Steel Diversified Industrial Products Corp. Diversified Metals, Inc. Dynamet, Inc. Eagle Alloys Corp. Ed Fagan, Inc. Extrusion Technology Corp. of America Falcon Stainless & Alloys Corp. G & S Titanium, Inc. General Titanium, Inc./BIAM Global Titanium, Inc. Harvey Titanium Ltd. Interstate Metals Metalmart, Inc./Mark Metals Metalmen Sales, Inc. Midwest Metals, Inc. National Electronic Alloys National Specialty Alloys, Inc. Oremet-Wah Chang Rickard Specialty Metals & Engineering, Inc. Sierra Alloys Co., Inc. Specialty Steel & Forge, Inc. Tico Titanium, Inc. Titanium & Alloys Corp.

306 / Titanium: A Technical Guide Table E.4

(continued)

Rod (continued) Titanium Distribution Services Titanium Fabrication Corp. Titanium Finishing Co. Titanium Industries, Inc. Titanium Ltd. Titanium Metals Corp. (TIMET) Trans World Alloys Tricor Industrial, Inc. United Titanium, Inc. Vulcanium Metals International Sheet Advanced Alloys Aerodyne Ulbrich Alloys, Inc. Aero Specialties Materials Corp. Aerotech Industries All Metal Sales, Inc. Altemp Alloys, Inc. American Aerospace Materials AmeriCana Metal Service, Inc. AstroCosmos Metallurgical, Inc. B & L Metals, Inc. B & S Aircraft Alloys, Inc. DiamondTel Steel Diversified Industrial Products Corp. Diversified Metals, Inc. Eagle Alloys Corp. Ed Fagan, Inc. Express Metals Co. Falcon Stainless & Alloys Corp. Ferguson Metals, Inc. Industrial Metals International, Ltd. Interstate Metals Metalmart, Inc./Mark Metals Oremet-Wah Chang Rickard Specialty Metals & Engineering, Inc. RJ Enterprise, LLC RMI Titanium Co. Specialty Steel & Forge, Inc. Sterling Aircraft Materials Ltd. Supra Alloys, Inc. Tara Metals Inc. Titanium Distribution Services, Inc. Titanium Industries, Inc. Titanium Metals Corp. (TIMET) Trans World Alloys Tricor Industrial, Inc. Ulbrich Stainless Steels & Special Metals, Inc. Vulcanium Metals International Sponge A-1 Alloys All-Chemie, Ltd. Atlantic Equipment Engineers Atomergic Chemetals Corp. Extrusion Technology Corp. of America Global Titanium, Inc. Sierra Alloys Co., Inc.

Sponge (continued) Titanium Hearth Technologies Titanium Metals Corp. (TIMET) Strip Advanced Alloys Allegheny Rodney Strip Div. Alloys International, Inc. (Aii) Aerotech Industries AmeriCana Metal Service, Inc. B & S Aircraft Alloys, Inc. Coltwell Industries DiamondTel Steel Diversified Industrial Products Corp. Eagle Alloys Corp. Ed Fagan, Inc. Elgiloy Specialty Metals Extrusion Technology Corp. of America Falcon Stainless & Alloys Corp. Ferguson Metals, Inc. G & S Titanium, Inc. Harvey Titanium Ltd. Industrial Metals International, Inc. Interstate Metals Midwest Metals, Inc. Metalmen Sales, Inc. National Electronic Alloys Rickard Specialty Metals & Engineering, Inc. RMI Titanium Co. Sierra Alloys Co., Inc. Specialty Steel & Forge, Inc. Sterling Aircraft Materials Ltd. Supra Alloys, Inc. Tico Titanium, Inc. Titanium & Alloys Corp. Titanium Distribution Services, Inc. Titanium Fabrication Corp. Titanium Hearth Technologies Titanium Industries, Inc. Titanium Metals Corp. (TIMET) Ulbrich Stainless Steels & Special Metals, Inc. Vulcanium Metals International Tube, tubing A-1 Alloys Advanced Alloys Aero Specialties Materials Corp. Aerotech Industries AmeriCana Metal Service, Inc. Atlantic Stainless Co., Inc. B & L Metals, Inc. B & S Aircraft Alloys, Inc. DiamondTel Steel Diversified Industrial Products Corp. Diversified Metals, Inc. Eagle Alloys Corp. Express Metals Co. Falcon Stainless & Alloys Corp. Industrial Metals International, Ltd.

Tube, tubing (continued) Interstate Metals Metalmart, Inc./Mark Metals Metal Technology, Inc. National Specialty Alloys, Inc. Oremet-Wah Chang RJ Enterprise, LLC Sandvik Special Metals Corp. Specialty Steel & Forge, Inc. Sterling Aircraft Materials Ltd. Superior Tube Co. Titanium Industries, Inc. Titanium Metals Corp. (TIMET) Trans World Alloys Tricor Industrial, Inc. Vulcanium Metals International Wire A-1 Alloys Advanced Alloys Inc. Aero Specialties Materials Corp. Aerotech Industries All-Chemie, Ltd. All Metals Sales, Inc. Alloys International, Inc. (Aii) AmeriCana Metal Service, Inc. Astrolite Alloys B & L Metals, Inc. B & S Aircraft Alloys, Inc. California Fine Wire Co. DiamondTel Steel Diversified Industrial Products Corp. Diversified Metals, Inc. Dynamet, Inc. Eagle Alloys Corp. Extrusion Technology Corp. of America Falcon Stainless & Alloys Corp. Fort Wayne Metals Research Products Corp. G & S Titanium, Inc. Material Net Metalmen Sales, Inc. National Electronic Alloys National Specialties Corp. Oremet-Wah Chang The Perryman Co. Rickard Specialty Metals & Engineering Inc. RJ Enterprise, LLC Specialty Steel & Forge, Inc. Sterling Aircraft Materials Ltd. Tico Titanium, Inc. Titanium Hearth Technologies Titanium Industries Titanium Metals Corp. (TIMET) Trans World Alloys Tricor Industrial, Inc. Ulbrich Shaped Wire, Inc. Vulcanium Metals International

Titanium: A Technical Guide Matthew J. Donachie, Jr., p307-312 DOI:10.1361/tatg2000p307

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Appendix F

Corrosion Data ALTHOUGH TITANIUM is a highly anodic material, titanium and titanium alloys are remarkably resistant to corrosion owing to the formation of stable, self-healing oxide films on their surfaces. Unalloyed titanium is highly resistant to general corrosion normally associated with many natural environments, including body fluids. Because titanium metal has a high affinity for oxygen, the protective oxide film formed on the metal or its alloys can effectively reheal itself almost instantly when fresh metal surfaces are exposed to air or water. Under anhydrous conditions, in the absence of oxygen, corrosion of titanium may result because the protective oxide film may not be regenerated if damaged. General corrosion resistance of titanium and titanium alloys is exceptional among the stronger structural metals. The major corrosion problem with titanium alloys may be in crevice corrosion, which occurs when the corroding media become stagnant as in crevices or pits. Mention also has been made in Table F.1

Chapter 13 of the tendency of certain titanium alloys to be susceptible to stress corrosion cracking in selected media and at selected temperatures. Titanium and titanium alloys are not used at exceptionally high temperatures, so high-temperature oxidation is normally not an issue. The successful application of titanium and titanium alloys under general corrosion conditions has been studied. Tables F.1, F.2, and F.3 provide data on the general corrosion of titanium and titanium alloys.

Corrosion Rates This Appendix is a compilation of general corrosion rate values for the two broad groupings of titanium-base alloys:

• Commercially pure, ASTM grades 1 through

• Other titanium alloys (Table F.2) These values were derived from various published sources and from in-house laboratory tests. Table F.3 supports the user by breaking out into more readable forms the abbreviated designations used in Table F.2. These data should be used only as a starting point or initial guideline for the corrosion performance of titanium. Actual rates may vary, depending on changes in media chemistry, temperature, length of exposure, and various other factors. Also, note that the suitability of a specific commercially pure grade or alloy for an application cannot necessarily be inferred from these values alone, since other modes of corrosion, such as localized attack, may be limiting. In complex, variable, and/or dynamic environments, in situ testing may provide more reliable data.

4 (Table F.1)

Commercially pure titanium corrosion rates

Medium

Acetaldehyde Acetate, n-propyl Acetic acid

Acetic acid + 3% acetic anhydride Acetic acid + 1.5% acetic anhydride Acetic acid + 109 ppm Cl Acetic acid + 106 ppm Cl Acetic acid + 5% formic acid Acetic anhydride Adipic acid + 15–20% glutaric + 2% acetic acid Adipic acid Adipylchloride and chlorobenzene solution

Concentration, %

Temperature, °C (°F)

Corrosion rate, mm/year

75 100 … 5–99.7 33–vapor 99 65 58 99.7 Glacial Glacial 31.2 62.0 58 100 100 99.5 25

149 (300) 149 (300) 87 (189) 124 (255) Boiling Boiling 121 (250) 130 (266) 124 (255) 204 (399) 204 (299) Boiling Boiling Boiling 21 (70) 150 (302) Boiling 199 (390)

0.001 Nil Nil Nil Nil 0.003 0.003 0.381 0.003 1.02 0.005 0.259 0.272 0.457 0.025 0.005 0.013 Nil

67 …

240 (464) …

Nil Nil

Medium

Adiponitrile Aluminum chloride, aerated Aluminum chloride

Aluminum Aluminum fluoride Aluminum nitrate Aluminum sulfate Aluminum sulfate + 1% H2SO4 Ammonium acid phosphate Ammonium aluminum chloride Ammonia, anhydrous Ammonia, steam, water Ammonium acetate Ammonium bicarbonate Ammonium bisulfite, pH 2.05

Concentration, %

Temperature, °C (°F)

Vapor 10 25 10 10 25 25 Molten Saturated Saturated Saturated 10 10 Saturated 10 Molten 100 … 10 50 Spent pulping liquor

371 (700) 100 (212) 100 (212) 100 (212) 150 (302) 60 (140) 100 (212) 677 (1251) Room Room Room 80 (176) Boiling Room Room 350–380 (662–716) 40 (104) 222 (432) Room 100 (212) 71 (160)

(continued) Data apply to unalloyed titanium, ASTM grades 1–4. (See Appendix B, ASTM Specification B 265.) Room temperature assumed to be 25 °C (77 °F). Source: TIMET Corp.

Corrosion rate, mm/year

0.008 0.002 3.15 0.002 0.03 Nil 6.55 164.6 Nil Nil Nil 0.05 0.12 Nil Nil Very rapid attack <0.127 11.2 Nil Nil 0.015

308 / Titanium: A Technical Guide Table F.1

(continued)

Medium

Ammonium carbamate Ammonium chloride Ammonium chlorate Ammonium fluoride Ammonium hydroxide Ammonium nitrate Ammonium nitrate + 1% nitric acid Ammonium oxalate Ammonium perchlorate Ammonium sulfate Ammonium sulfate + 1% H2SO4 Aniline Aniline + 2% AlCl3 Aniline hydrochloride Antimony trichloride Aqua regia Arsenous oxide Barium carbonate Barium chloride Barium hydroxide Barium nitrate Barium fluoride Benzaldehyde Benzene (traces of HCl) Benzene Benzoric acid Bismuth Bismuth/lead Boric acid Bromine Bromine, moist Bromine gas, dry Bromine-water solution Bromine in methyl alcohol N-butyric acid Calcium bisulfite Calcium carbonate Calcium chloride

Calcium hydroxide Calcium hypochlorite

Carbon dioxide Carbon tetrachloride Carbon tetrachloride + 50% H2O Chlorine gas, wet Chlorine saturated water Chlorine gas, dry Chlorine dioxide Chlorine dioxide + HOCl, H2O + Cl2 Chlorine dioxide in steam Chlorine dioxide Chlorine monoxide (moist) Chlorine trifluoride Chloracetic acid Chlorosulfonic acid

Concentration, %

Temperature, °C (°F)

50 Saturated 300 g/L 10 28 28 28 28 Saturated 20 10 Saturated 100 98 5 20 27 3:1 3:1 3:1 Saturated Saturated 5 20 25 Saturated 10 Saturated 100 Vapor and liquid Liquid Liquid Saturated Molten Molten Saturated 10 Liquid Vapor … … 0.05

100 (212) 100 (212) 50 (122) Room Room 100 (212) Boiling Boiling Room 88 (190) 100 (212) Room Room 158 (316) 100 (212) 100 (212) Room Room 80 (176) Boiling Room Room 100 (212) 100 (212) 100 (212) Room Room Room Room 80 (176) 50 (122) Room Room 816 (1500) 300 (572) Room Boiling 30 (86) 30 (86) 21 (70) Room 60 (140)

Undiluted Cooking liquor Saturated 5 10 20 55 60 62 73 Saturated Saturated 2 6 18 Saturated 100 99 Liquid Vapor 50 >0.7 H2O >0.95 H2O >1.5 H2O Saturated <0.5 H2O 5 15 5 10 Up to 15 100 30 100 100

Room 26 (79) Boiling 100 (212) 100 (212) 100 (212) 104 (219) 149 (300) 154 (309) 175 (347) Room Boiling 100 (212) 100 (212) 21 (70) 21 (70) … Boiling Boiling Boiling 25 (77) Room 140 (284) 200 (392) 97 (207) Room 82 (180) 43 (109) 99 (210) 70 (158) 43 (109) 30 (86) 82 (180) Boiling Room

Corrosion rate, mm/year

Nil <0.013 0.003 0.102 0.003 Nil Nil Nil Nil Nil Nil 0.010 Nil >1.27 Nil Nil Nil Nil 0.86 1.12 Nil Nil Nil Nil Nil Nil Nil Nil Nil 0.005

Medium

Chloroform Chloroform + 50% H2O Chloropicrin Chromic acid

Chromic acid + 5% nitric acid Citric acid

Citric acid (aerated) Copper nitrate Copper sulfate Copper sulfate + 2% H2SO4 Cupric carbonate + cupric hydroxide Cupric chloride Cupric cyanide Cuprous chloride Cyclohexylamine Cyclohexane (plus traces of formic acid) Dichloroacetic acid Dichlorobenzene + 4–5% HCl Diethylene triamine Ethyl alcohol

0.025 Nil Nil Ethylene dichloride High Ethylene dichloride + 50% water Good resistance Ethylene diamine Nil Ferric chloride Nil Rapid attack <0.003 Dissolves rapidly Nil Ferric chloride 0.03 (cracking Ferric sulfate possible) Ferrous chloride + 0.5% HCl Nil Ferrous sulfate 0.001 Fluoboric acid Nil Fluorine, commercial 0.005 Fluorine, HF free 0.007 0.015 Fluorosilicic acid 0.001 Formaldehyde <0.003 Formamide vapor 0.406 Formic acid, aerated 0.80 Nil Nil 0.001 Formic acid, nonaerated 0.001 Nil Nil Excellent Formic acid 0.005 Furfural Nil Gluconic acid Nil Glycerin Hydrogen chloride, gas 0.005 Hydrochloric acid, aerated Nil Nil Nil Nil May react <0.003 Nil Nil Hydrochloric acid 0.03 Nil Hydrochloric acid + 4% FeCl3 + 4% Vigorous reaction <0.127 MgCl2 <0.127 Hydrochloric acid + 4% FeCl3 + 4% 0.312 MgCl2 + Cl2 saturated (continued)

Concentration, %

Temperature, °C (°F)

Corrosion rate, mm/year

Vapor and liquid 50 100 10 15 15 50 50 5 10 25 50 50 672 50 Saturated 50 Saturated Saturated 20 40 55 Saturated 50 100 …

Boiling

0.000

25 (77) 95 (203) Boiling 24 (75) 82 (180) 24 (75) 82 (180) 21 (70) 100 (212) 100 (212) 60 (140) Boiling 149 (300) 100 (212) Room Boiling Room Ambient Boiling Boiling 118 (244) Room 90 (194) Room 150 (302)

0.000 0.003 0.003 0.006 0.015 0.013 0.028 <0.003 0.009 0.001 0.000 0.127–1.27 Corroded <0.127 Nil Nil 0.018 Nil Nil 0.005 0.003 Nil <0.003 Nil 0.003

100 … 100 95 100 100 50 100 10–20 1–30 10–40 1–30 50 10 10 30 Saturated 5–20 Gas-liquid Liquid Gas 10 37 … 10 25 50 90 10 25 50 90 9 100 50 … Air mixture 1 2 5 1

Boiling 179 (354) Room Boiling Room Boiling 25 (77) Room Room 100 (212) Boiling Boiling 150 (302) Boiling Room 79 (174) Room Elevated Gas, 109 (228) 196 (385) 196 (385) Room Boiling 300 (572) 100 (212) 100 (212) 100 (212) 100 (212) 100 (212) 100 (212) Boiling 100 (212) 50 (122) Room Room Room 25–100 (77–212) 60 (140) 60 (140) 60 (140) 100 (212)

0.007 0.102 Nil 0.013 Nil 0.005–0.127 0.005 Nil Nil 0.004 Nil Nil 0.003 0.00 Nil 0.006 Nil Rapid attack 0.864 0.011 0.011 47.5 Nil Nil 0.005 0.001 0.001 0.001 Nil 2.44 3.20 3.00 <0.127 Nil Nil Nil Nil 0.004 0.016 1.07 0.46

5 10 20 0.1 1 19

35 (95) 35 (95) 35 (95) Boiling Boiling 82 (180)

0.01 1.02 4.45 0.10 1.8 0.51

19

82 (180)

0.46

Corrosion Data / 309 Table F.1

(continued)

Medium

Hydrochloric acid, chlorine saturated Hydrochloric acid, chlorine saturated Hydrochloric acid + 200 ppm Cl2 Hydrochloric acid + 1% HNO3 + 1% HNO3 + 5% HNO3 + 5% HNO3 + 10% HNO3 + 10% HNO3 + 3% HNO3 + 5% HNO3 Hydrochloric acid + 2.5% NaClO3 + 5.0% NaClO3 Hydrochloric acid + 0.5% CrO3 + 0.5% CrO3 + 0.1% CrO3 + 1% CrO3 Hydrochloric acid + 0.05% CuSO4 + 0.05% CuSO4 + 0.5% CuSO4 + 0.5% CuSO4 + 1% CuSO4 + 1% CuSO4 + 5% CuSO4 + 5% CuSO4 + 0.05% CuSO4 + 0.5% CuSO4 Hydrochloric acid + 0.05% CuSO4 + 0.20% CuSO4 + 0.5% CuSO4 + 1% CuSO4 + 0.05% CuSO4 + 0.5% CuSO4 Hydrochloric acid + 0.1% FeCl3 Hydrochloric acid + 1 g/L Ti4+ Hydrochloric acid + 5.8 g/L Ti4+ Hydrochloric acid + 18% H3PO4 + 5% HNO3 Hydrofluoric acid Hydrofluoric acid, anhydrous Hydrofluoric-nitric acid 5 vol% HF-35 vol% HNO3 Hydrofluoric-nitric acid 5 vol% HF-35 vol% HNO3 Hydrogen peroxide Hydrogen peroxide + 2% NaOH Hydrogen peroxide pH 4 pH 1 pH 1 pH 11 Hydrogen sulfide (water saturated) Hydrogen sulfide, steam, and 0.077% mercaptans Hydroxy-acetic acid Hypochlorous acid + ClO and Cl2 gases Iodine, dry or moist gas Iodine in water + potassium iodide Iodine in alcohol Lactic acid Lead Lead acetate Linseed oil, boiled Lithium, molten Lithium chloride Magnesium Magnesium chloride

Concentration, %

Temperature, °C (°F)

Corrosion rate, mm/year

5 10 36

190 (374) 190 (374) 25 (77)

<0.025 28.5 0.432

5 5 5 5 5 5 8.5 1

40 (104) 95 (203) 40 (104) 95 (203) 40 (104) 95 (203) 80 (176) Boiling

Nil 0.091 0.025 0.030 Nil 0.183 0.051 0.074

10.2 10.2

80 (176) 80 (176)

0.009 0.006

5 5 5 5

38 (100) 95 (203) 38 (100) 95 (203)

Nil 0.031 0.018 0.031

5 5 5 5 5 5 5 5 5 5

38 (100) 93 (199) 38 (100) 93 (199) 38 (100) 93 (199) 38 (100) 93 (199) Boiling Boiling

0.040 0.091 0.091 0.061 0.031 0.091 0.020 0.061 0.064 0.084

10 10 10 10 10 10 5 10 20 18

66 (151) 66 (151) 66 (151) 66 (151) Boiling Boiling Boiling Boiling Boiling 77 (171)

0.025 Nil 0.023 0.023 0.295 0.290 0.01 0.000 0.000 0.000

1 100 …

26 (79) Room 25 (77)

127 0.127–1.27 452

…

35 (95)

571

3 6 30

Room Room Room

1

60 (140)

5 5 20 0.08 … 7.65

66 (151) 66 (151) 66 (151) 70 (158) 21 (70) 93–110 (199–230)

… 17 … … Saturated 10–85 10 … … Saturated … … 50 Molten 5–20

Medium

Magnesium hydroxide Magnesium sulfate Manganous chloride Maleic acid Mercuric chloride

Mercuric cyanide Mercury Methyl alcohol Mercury + iron Mercury + copper Mercury + zirconium Mercury + magnesium Monochloracetic acid Nickel chloride Nickel nitrate Nitric acid, aerated

Nitric acid

Nitric acid, not refreshed

<0.127 <0.127 <0.305 Nitric acid, white fuming

55.9 0.061 0.152 0.69 0.42 <0.003 Nil

Nitric acid, red fuming

40 (104) 0.003 38 (100) 0.000 25 (77) 0.1 Room Nil Room Pitted 100 (212) <0.127 Boiling <0.127 816 (1501) Attacked 324–593 (615–1099) Good Room Nil Room Nil 316–482 (601–900) Nil 149 (300) Nil 760 (1400) Limited resistance 100 (212) <0.010

Nitric acid + 0.01% K2Cr2O7 + 0.01% CrO3 + 0.01% FeCl3 + 1% FeCl3 + 1% NaClO3 + 1% NaClO3 + 1% Ce(SO4)2 + 0.1% K2Cr2O7 Nitric acid, saturated with zirconyl nitrate Nitric acid + 15% zirconyl nitrate Nitric acid + 179 g/L NaNO3 and 32 g/L NaCl Nitric acid + 170 g/L NaNO3 and 2.9 g/L NaCl

Concentration, %

Temperature, °C (°F)

5–40 Saturated Saturated 5–20 18–20 1 5 10 Saturated Saturated 100 100 … 91 95 … … … … 30 100 5 20 50 10 30 40 50 60 70 10 20 30 40 50 60 70 40 70 20 35 70 17 35 70 5–60 5–60 30–50 5–20 30–60 70 20 70 Liquid or vapor … … … About 2% H2O 40 40 40 40

Boiling Room Room 100 (212) 35 (95) 100 (212) 100 (212) 100 (212) 100 (212) Room Up to 38 (up to 100) Room 371 (700) 35 (95) 100 (212) 371 (700) 371 (700) 371 (700) 371 (700) 80 (176) Boiling 100 (212) 100 (212) Room Room Room Room Room Room Room 40 (104) 40 (104) 50 (122) 50 (122) 60 (140) 60 (140) 70 (158) 200 (392) 270 (518) 290 (554) 80 (176) 80 (176) Boiling Boiling Boiling 35 (95) 60 (140) 100 (212) 100 (212) 190 (374) 270 (518) 290 (554) 290 (554) Room 82 (180) 122 (252) 160 (320) Room

0.005 Nil Nil Nil 0.002 0.000 0.011 0.001 0.001 Nil Satisfactory Nil 3.03 Nil <0.01 0.079 0.063 0.033 0.083 0.02 0.013 0.004 0.003 Nil 0.005 0.004 0.002 0.002 0.001 0.005 0.003 0.005 0.015 0.016 0.037 0.040 0.040 0.610 1.22 0.305 0.051–0.102 0.025–0.076 0.076–0.102 0.127–0.508 0.064–0.900 0.002–0.007 0.01–0.02 0.10–0.18 0.02 1.5–2.8 1.2 0.4 1.1 Nil 0.152 <0.127 <0.127 Ignition sensitive

Room Boiling Boiling Boiling Boiling

Not ignition sensitive 0.63 0.01 0.01 0.68

40 40 40 40 40 33–45 65 20.8

Boiling Boiling Boiling Boiling Boiling 118 (244) 127 (261) Boiling

0.14 0.31 0.02 0.10 0.016 Nil Nil 0.127–0.295

27.4

Boiling

0.483–2.92

(continued) Data apply to unalloyed titanium, ASTM grades 1–4. (See Appendix B, ASTM Specification B 265.) Room temperature assumed to be 25 °C (77 °F). Source: TIMET Corp.

Corrosion rate, mm/year

310 / Titanium: A Technical Guide

Table F.1 Medium

Oxalic acid

(continued) Concentration, %

1 5 1 Oxalic acid (continued) 25 Saturated Perchloroethylene + 50% H2O 50 Perchloryl fluoride + liquid ClO3 100 99 Perchloryl fluoride + 1% H2O … Pheonol Saturated solution Phosphoric acid 10–30 30–80 5.0 6.0 0.5 1.0 12 20 50 9 10 5 10 Phosphoric acid + 3% nitric acid 81 Phosphorus oxychloride 100 Phosphorus trichloride Saturated Photographic emulsions … Phthalic acid Saturated Potassium bromide Saturated Potassium chloride Saturated Saturated Potassium dichromate Saturated Potassium ethyl xanthate 10 Potassium ferricyanide Saturated Potassium hydroxide + 13% potassium 13 chloride Potassium hydroxide 50 10 25 50 50 anhydrous Potassium iodide Saturated Potassium permanganate Saturated Potassium perchlorate 20 0–30 Potassium sulfate 10 Potassium thiosulfate 1 Propionic acid Vapor Pyrogallic acid 355 g/L Salicylic acid Saturated Seawater … Seawater, 4 1 2 yr test … Sebacic acid … Silver nitrate 50 Sodium 100 Sodium acetate Saturated Sodium aluminate 25 Sodium bifluoride Saturated Sodium bisulfate Saturated 10 Sodium bisulfite 10 25 Sodium carbonate 25 Sodium chlorate Saturated Sodium chlorate + NaCl 80–250 g/L 0–721 g/L Sodium chloride Saturated pH 7 23 pH 1.5 23 pH 1.2 23 pH 1.2, some dissolved chlorine 23 Sodium citrate Saturated Sodium cyanide Saturated Sodium dichromate Saturated Sodium fluoride Saturated pH 7 1 pH 10 1

Temperature, °C (°F)

Corrosion rate, mm/year

35 (95) 35 (95) Boiling 60 (140) Room 25 (77) 30 (86) 30 (86) … 25 (77)

0.03 0.13 107 11.9 0.508 Nil 0.002 Liquid 0.290 Vapor 0.003 0.102

Room Room 66 (151) 66 (151) Boiling Boiling 25 (77) 25 (77) 25 (77) 52 (126) 52 (126) Boiling 80 (176) 88 (190) Room Room … Room Room Room 60 (140) Room Room Room 29 (84)

0.020 –0.051 0.051–0.762 0.005 0.117 0.094 0.266 0.005 0.076 0.19 0.03 0.38 3.5 1.83 0.381 0.004 Nil <0.127 Nil Nil Nil Nil Nil Nil Nil Nil

29 (84) Boiling Boiling Boiling 241–377 (466–711) Room Room Room 50 (122) Room Room 190 (374) Room Room 24 (75) Ambient 240 (464) Room To 593 Room Boiling Room Room 66 (151) Boiling Boiling Boiling Room

0.010 <0.127 0.305 2.74 1.02–1.52 Nil Nil 0.003 0.003 Nil Nil Rapid attack Nil Nil Nil Nil 0.008 Nil Good Nil 0.091 Rapid Nil 1.83 Nil Nil Nil Nil

40 (104) Room Boiling Boiling Boiling Boiling Room Room Room Room Boiling Boiling

0.003 Nil Nil Nil 0.71 Nil Nil Nil Nil 0.008 0.001 0.001

Medium

pH 7 Sodium hydrosulfide + sodium sulfide and polysulfides Sodium hydroxide Sodium hydroxide (continued)

Sodium hypochlorite Sodium hypochlorite + 15% NaCl + 1% NaOH Sodium nitrate Sodium perchlorate Sodium phosphate Sodium silicate Sodium sulfate Sodium sulfide Sodium sulfite Sodium thiosulfate Sodium thiosulfate + 20% acetic acid Soils, corrosive Stannic chloride Stannic chloride, molten Stannic chloride Steam + air Steam + 7.65% hydrogen sulfide Stearic acid, molten Succinic acid Sulfanilic acid Sulfamic acid Sulfamic acid + 0.375 g/L FeCl3 Sulfur, molten Sulfur monochloride Sulfur dioxide, dry Sulfur dioxide, water saturated Sulfur dioxide gas + small amount SO3 and approximately 3% O2 Sulfuric acid, aerated

Sulfuric acid Sulfuric acid + 0.25% CuSO4 Sulfuric acid + 0.5% CuSO4 Sulfuric acid + 1.0% CuSO4 Sulfuric acid + 0.5% CrO3 Sulfuric acid + 1.0% CuSO4 Sulfuric acid vapors Sulfuric acid + 10% HNO3 Sulfuric acid + 50% HNO3 Sulfuric acid + 70% HNO3

(continued)

Concentration, %

Temperature, °C (°F)

Corrosion rate, mm/year

1

204 (399)

0.000

5–12 5–10 10 28 40 50 50 73 50–73 50 6 1.5–4

110 (230) 21 (70) Boiling Room 80 (176) 57 (135) Boiling 129 (264) 188 (370) 38 (100) Room 66–93 (151–199)

<0.003 0.001 0.021 0.003 0.127 0.013 0.051 0.178 >1.09 0.023 Nil 0.030

Saturated 900 g/L Saturated 25 10–20 Saturated 10 Saturated Saturated 25 20 … 5 24 100 100 Saturated … … 100 100 Saturated Saturated 3.75 g/L 7.5 g/L 7.5 g/L 100 … … Near 100 18

Room 50 (122) Room Boiling Boiling Room Boiling Room Boiling Boiling Room Ambient 100 (212) Boiling 66 (151) 35 (95) Room 82 (180) 93–110 (199–230) 180 (356) 185 (365) Room Room Boiling Boiling Boiling 240 (464) 202 (396) 21 (70) Room 316 (601)

Nil 0.003 Nil Nil Nil Nil 0.027 Nil Nil Nil Nil Nil 0.003 0.045 Nil Nil Nil Nil Nil 0.003 Nil Nil Nil Nil 2.74 0.030 Nil >1.09 Nil 0.003 0.006

1 3 5 10 40 75 75 1 3 Concentrated Concentrated 1 3 1 5 5 30 30 30 30 30 30 5 30 30 96 96 96 90 50 30

60 (140) 60 (140) 60 (140) 35 (95) 35 (95) 35 (95) Room 100 (212) 100 (212) Room Boiling 100 (212) 100 (212) Boiling Boiling 95 (203) 38 (100) 95 (203) 38 (100) 95 (203) 38 (100) 95 (203) 95 (203) 95 (203) Boiling 38 (100) 66 (151) 200–300 (392–572) Room Room Room

0.008 0.013 4.83 1.27 8.64 1.07 10.8 0.005 23.4 1.57 5.38 7.16 21.1 17.8 25.4 Nil 0.061 0.088 0.067 0.823 0.020 0.884 Nil Nil 1.65 Nil Nil 0.013 0.457 0.635 0.102

Corrosion Data / 311

Table F.1

(continued) Concentration, %

Medium

Sulfuric acid + 90% HNO3 Sulfuric acid + 90% HNO3 Sulfuric acid + 95% HNO3 Sulfuric acid + 50% HNO3 Sulfuric acid + 20% HNO3 Sulfuric acid saturated with chlorine

Sulfuric acid + 4 g/L Ti4+ Sulfurous acid Tannic acid Tartaric acid

Temperature, °C (°F)

10 10 5 50 80 45 62 5, 10 82 40 6 25 10–50 10 25 50 10 25 50

Corrosion rate, mm/year

Room 60 (140) 60 (140) 60 (140) 60 (140) 24 (75) 16 (61) 190 (374) 50 (122) 100 (212) Room 100 (212) 100 (212) 60 (140) 60 (140) 60 (140) 100 (212) 100 (212) 100 (212)

Medium

Terephthalic acid Tetrachloroethane, liquid and vapor Tetrachloroethylene + H2O Tetrachloroethylene Tetrachloroethylene, liquid and vapor Titanium tetrachloride Trichloroacetic acid Trichloroethylene Trichloroethylene + 50% H2O Uranium chloride Uranyl ammonium phosphate filtrate + 25% chloride + 0.5% fluoride + 1.4% ammonia + 2.4% uranium Uranyl nitrate containing 25.3 g/L Fe3+, 6.9 g/L Cr3+, 2.8 g/L Ni2+, 4.0 M HNO3 + 1.0 M Cl Uranyl sulfate + 3.1 M Li2SO4 + 100–200 ppm O2

Nil 0.011 0.005 0.399 1.59 0.003 0.002 <0.025 >1.19 Nil Nil Nil <0.127 0.003 0.003 0.001 0.003 Nil 0.0121

Concentration, %

Temperature, °C (°F)

Corrosion rate, mm/year

77 100 … 100 100 99.8 100 99 50 Saturated 20.9

218 (424) Boiling Boiling Boiling Boiling 300 (572) Boiling Boiling 25 (77) 21–90 (70–194) 165 (329)

Nil 0.001 0.127 Nil 0.001 1.57 14.6 0.003–0.127 0.001 Nil <0.003

120 g/L

Boiling

Nil

3.1 M

250 (482)

<0.020

Data apply to unalloyed titanium, ASTM grades 1–4. (See Appendix B, ASTM Specification B 265.) Room temperature assumed to be 25 °C (77 °F). Source: TIMET Corp.

Table F.2

Titanium alloy corrosion rates

Medium

Acetic acid Acetic acid + 5% formic acid Ammonium hydroxide Aluminum chloride

Ammonium chloride Ammonium hydroxide Aqua regia

Calcium chloride Chlorine, wet Chromic acid

Citric acid

Ferric chloride

Formic acid Formic acid, nitrogen- sparged Formic acid

Alloy(a)

Grade 9 Grade 12 Grade 12 Grade 12 Grade 7 Grade 7 Grade 12 Grade 9 Grade 7 Grade 12 Grade 9 Grade 9 Grade 7 Grade 7 Grade 7 Grade 7 Grade 9 Grade 9 Grade 9 Grade 7 Grade 12 Grade 9 Grade 7 Grade 12 Ti-5Ta Grade 7 Ti-6-4 Ti-3-8-6-4-4 Ti-10-2-3 Ti-6-2-4-6 Transage 207 Ti-550 Grade 9 Ti-6-2-1-0.8 Grade 9 Grade 9 Grade 9 Grade 7 Grade 12 Grade 7

Concentration, Temperature, Corrosion rate, % % mm/yr

99.7 58 30 10 10 25 10 8, 28 3:1 3:1 3:1 3:1 62 73 … 10 10 30 50 50 50 50 10 10 10 30 10 10 10 10 10 10 10 10 25 25 50 45 45, 50 50

Boiling Boiling Boiling Boiling 100 (212) 100 (212) Boiling 150 (302) Boiling Boiling Boiling 25 (77) 150 (302) 177 (351) 25 (77) Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling 88 (190) 35 (95) Boiling Boiling Boiling Boiling

Nil Nil Nil Nil <0.025 0.025 Nil Nil 1.12 0.61 1.29 0.015 Nil Nil Nil Nil 0.008 0.053 0.26 0.025 0.013 0.38 Nil Nil Nil Nil Nil Nil Nil 0.06 0.19 Nil Nil Nil <0.13 <0.13 5.08 Nil Nil 0.01

Medium

Ti-6-4 Transage 207 Ti-6-2-4-6 Ti-3-8-6-4-4 Ti-5Ta Ti-550 Grade 12 Grade 7 Hydrochloric acid Ti-550 Ti-550 Transage 207 Transage 207 Ti-6-2-4-6 Ti-6-2-4-6 Hydrochloric acid, aerated Ti-6-2-4-6 Hydrochloric acid Ti-10-2-3 Ti-3-8-6-4-4 Ti-3-8-6-4-4 Ti-3-8-6-4-4 Hydrochloric acid, aerated Ti-3-8-6-4-4 Hydrochloric acid Ti-5Ta Ti-5Ta Ti-6-4 Hydrochloric acid, aerated Ti-6-4 Hydrochloric acid Grade 9 Grade 9 Grade 9 Hydrochloric acid, deaerated Grade 7 Grade 7 Grade 7 Hydrochloric acid Grade 9 Hydrochloric acid, aerated Grade 9 Hydrochloric acid, nitrogen saturated Grade 9 Hydrochloric acid Ti-6-2-1-0.8 Ti-6-2-1-0.8 Grade 7 Grade 7 Grade 7 Grade 7 Grade 12

Formic acid (continued)

(continued) (a) For unabbreviated designations, see Table F.3. Source: TIMET Corp.

Alloy(a)

Concentration, %

50 50 50 50 50 50 90 90 0.5 1.0 0.5 1.0 0.5 1.0 pH 1 0.5 0.5 1.0 1.5 pH 1 0.5 1.5 1.0 pH 1 0.5 1 3 3 5 10 1 5 5 0.5 1.0 0.5 1.0 1.5 5.0 0.5

Temperature, %

Corrosion rate, mm/yr

Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling 88 (190) 88 (190) 82 (180) 82 (180) 82 (180) Boiling 35 (95) 35 (95) Boiling Boiling Boiling Boiling Boiling Boiling Boiling

7.92 0.90 0.62 0.98 3.16 0.02 0.56 0.056 0.056 0.64 0.005 0.025 Nil 0.03 0.01 1.10 0.003 0.058 0.26 Nil 0.013 2.10 2.52 0.60 1.08 0.009 3.10 0.013 0.051 0.419 2.79 0.001 0.185 0.020 1.07 Nil 0.008 0.03 0.23 Nil

312 / Titanium: A Technical Guide Table F.2

(continued)

Medium

Hydrochloric acid (continued) Hydrochloric acid, hydrogen saturated

Hydrochloric acid, oxygen saturated Hydrochloric acid, chlorine saturated Hydrochloric acid, aerated

Alloy (a)

Grade 12 Grade 12 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7

Hydrochloric acid + 4% FeCl3 + 4% MgCl2 Grade 7 Hydrochloric acid + 4% FeCl3 + 4% MgCl2, chlorine saturated Hydrochloric acid Grade 7 + 5 g/L FeCl3 + 16 g/L FeCl3 Grade 7 + 16 g/L CuCl2 Grade 7 Hydrochloric acid + 2 g/L FeCl3 Grade 12 + 0.2% FeCl3 Grade 9 Grade 9 + 0.2% FeCl3 + 0.2% FeCl3 Grade 9 + 0.1% FeCl3 Grade 9 + 0.1% FeCl3 Ti-550 + 0.1% FeCl3 Transage 207 + 0.1% FeCl3 Ti-6-2-4-6 + 0.1% FeCl3 Ti-10-2-3 Ti-3-8-6-4-4 + 0.1% FeCl3 + 0.1% FeCl3 Ti-5Ta + 0.1% FeCl3 Ti-6-4 + 0.1% FeCl3 Ti-6-2-1.-0.8 + 0.1% FeCl3 Grade 7 + 0.1% FeCl3 Grade 12 Hydrochloric acid + 18% Grade 7 H3PO4 + 5% HNO3 Hydrogen peroxide pH 1 Grade 7 pH 4 Grade 7 pH 1 Grade 7 pH 4 Grade 7 Grade 7 + 500 ppm Ca2+, pH 1 Grade 7 + 500 ppm Ca2+, pH 1 Hydrogen peroxide, pH 1 + 5% NaCl Grade 7 Magnesium chloride Grade 7 Methyl alcohol Grade 9 Oxalic acid Grade 7 Nitric acid Grade 9 Grade 9 Phosphoric acid, naturally aerated Grade 12 Grade 12 Grade 12 Grade 12 Grade 12 Grade 12 Grade 12 Grade 12

Concentration, Temperature, Corrosion rate, % % mm/yr

1.0 1.5 1–15 20 5 10 15 3 5 10 3, 5 10 3, 5 10 1, 5 10 15 19

Boiling Boiling 25 (77) 25 (77) 70 (158) 70 (158) 70 (158) 190 (374) 190 (374) 190 (374) 190 (374) 190 (374) 190 (374) 190 (374) 70 (158) 70 (158) 70 (158) 82 (180)

0.04 0.25 <0.025 0.102 0.076 0.178 0.33 0.025 0.102 8.9 0.127 9.3 <0.03 29.0 <0.03 0.05 0.15 0.49

19

82 (180)

0.46

10 10 10

Boiling Boiling Boiling

0.279 0.076 0.127

4.2 1 5 10 5 5 5 5 5 5 5 5 5 5 5 18

91 (196) Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling 77 (171)

0.058 0.005 0.033 0.305 0.008 0.393 0.048 0.068 0.008 0.018 0.020 0.015 0.051 0.013 0.020 Nil

5 5 5 5 5 20 20 Saturated 99 1 10 30 25 30 45 8 13 15 5 7

23 (73) 23 (73) 66 (151) 66 (151) 66 (151) 66 (151) 66 (151) Boiling Boiling Boiling Boiling Boiling 25 (77) 25 (77) 25 (77) 52 (126) 52 (126) 52 (126) 66 (151) 66 (151)

0.062 0.010 0.127 0.046 Nil 0.76 0.008 Nil Nil 1.14 0.084 0.497 0.019 0.056 0.157 0.02 0.066 0.52 0.038 0.15

Medium

Alloy(a)

Phosphoric acid, naturally aerated (continued)

Potassium hydroxide Seawater Sodium chloride, pH 1 Sodium fluoride pH 7 pH 7 Sodium hydroxide Sodium sulfate, pH 1 Sulfamic acid Sulfuric acid, naturally aerated

Sulfuric acid, nitrogen saturated

Sulfuric acid, oxygen saturated Sulfuric acid, chlorine saturated Sulfuric acid, nitrogen saturated Sulfuric acid, aerated Sulfuric acid, nitrogen saturated Sulfuric acid, naturally aerated Sulfuric acid, aerated Sulfuric acid + 5 g/L Fe2(SO4)3 Sulfuric acid + 16 g/L Fe2(SO4)3 Sulfuric acid + 16 g/L Fe2(SO4)3 Sulfuric acid + 15% CuSO4 Sulfuric acid + 3% Fe2(SO4)3 Sulfuric acid + 1 g/L FeCl3 Sulfuric acid + 50 g/L FeCl3 Sulfuric acid + 1% CuSO4 Sulfuric acid + 100 ppm Cu2+ + 1% thiourea (deaerated) Sulfuric acid + 100 ppm Cu2+ + 1% thiourea (deaerated) Sulfuric acid + 1000 ppm Cl-–

Concentration, %

0.5 1.0 40 60 15 23 8 15 0.5 1.0 5.0 50 … Saturated

Boiling Boiling 25 (77) 25 (77) 52 (126) 52 (126) 66 (151) 66 (151) Boiling Boiling Boiling 150 (302) Boiling 93 (199)

0.071 0.14 0.008 0.07 0.036 0.15 0.076 0.104 0.050 0.107 0.228 9.21 Nil Nil

Grade 12 Grade 7 Grade 9 Grade 7 Grade 12 Grade 7 Grade 12 Grade 12 Grade 12 Grade 12 Grade 12 Grade 12 Grade 12 Grade 12 Grade 12 Grade 7 Grade 7 Grade 12 Grade 9 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 9 Grade 9 Ti-3-8-6-4-4 Ti-3-8-6-4-4 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Ti-3-8-6-4-4 Ti-3-8-6-4-4 Ti-3-8-6-4-4 Grade 7 Grade 7

1 1 50 10 10 10 9 9.5 10 3.5 3.75 2.75 3.0 0.75 1.0 1.0 2.0 1.0 0.5 5 10 1, 5 10 1–10 10 20 10 40 5 5 1 5 10 40 10 10 20 15 50 10 10 30 1

Boiling Boiling 150 (302) Boiling Boiling Boiling 24 (75) 24 (75) 24 (75) 52 (126) 52 (126) 66 (151) 66 (151) Boiling Boiling 204 (399) 204 (399) 204 (399) Boiling 70 (158) 70 (158) 190 (374) 190 (374) 190 (374) 190 (374) 190 (374) 25 (77) 25 (77) 35 (95) 35 (95) Boiling Boiling 70 (158) 70 (158) Boiling Boiling Boiling Boiling Boiling Boiling Boiling Boiling 100 (212)

0.001 0.002 0.49 Nil 11.6 0.37 0.003 0.006 0.38 0.013 1.73 0.015 1.65 0.003 0.91 0.005 Nil 0.91 8.48 0.15 0.25 0.13 1.50 0.13 0.051 0.38 0.025 0.23 0.025 0.405 Nil 1.85 0.10 0.94 0.178 <0.03 0.15 0.64 <0.03 0.15 0.05 1.75 Nil

Grade 12

1

100 (212)

0.23

Grade 7

15

49 (120)

0.015

Table F.3 Alloy abbreviations used in Table F.2

Grade 7 Grade 9 Grade 12 Ti-6-4 Ti-3-8-6-4-4 Ti-10-2-3

Alloy

Ti-0.2Pd Ti-3Al-2.5V Ti-0.3Mo-0.8Ni Ti-6Al-4V Ti-3Al-8V-6Cr-4Mo-4Zr Ti-10V-2Fe-3Al

Abbreviation

Ti-6-2-4-6 Ti-6-2-1-0.8 Ti-10-2-3 Ti-550 Transage 207

Corrosion rate, mm/yr

Grade 12 Grade 12 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 7 Grade 9 Grade 9 Grade 9

(a) For unabbreviated designations, see Table F.3. Source: TIMET Corp.

Abbreviation

Temperature, %

Alloy

Ti-6Al-2Sn-4Zr-6Mo Ti-6Al-2Nb-1Ta-0.8Mo Ti-10V-2Fe-3Al Ti-4Al-4Mo-2Sn Ti-2.5Al-2Sn-9Zr-8Mo

Titanium: A Technical Guide Matthew J. Donachie, Jr., p313-325 DOI:10.1361/tatg2000p313

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Appendix G

Machining Data TITANIUM is one of the more difficult metals to machine. However, as indicated in Chapter 10, reasonable production rates and excellent surface finish are possible with conventional machining methods. The following section contains specific data related to a number of titanium machining processes. The topics covered are:

• • • • • • • • • • •

Sawing Turning Drilling Reaming Tapping Broaching Face milling End milling: slotting End milling: peripheral Surface grinding Thermal cutting

(Chapter 10 contains a general overview of the topic.)

Specific Data Listings Data contained in these tables must be considered as typical and representative. Although Table G.1

all specifics were compiled from widespread experience by two major producers, the data may be seen only as a starting point both for individual operating conditions and for a given manufacturer’s particular titanium or titanium alloy product. Fabricators involved in titanium machining should begin building a documented database for each type of machining operation encountered, and work closely with suppliers. Manufacturers provide extensive technical data, which should be requested before initiating the kind of operations described here. (Some of the following material is reprinted with the generous permission of RMI Company. Other material was contributed by Industrial Titanium Corporation. The data represent a synthesis of experiences and recommendations on the topic of machining titanium and its alloys.)

Sawing Titanium may be sawed using abrasive cutting wheels, hacksaws, or bandsaws. Chip formation is the most important gage in determining the success of any sawing operation. The formation of nearly invisible, flakelike chips can cause early blade failure. Fortunately, pre-

ventative measures are available to control the formation of these chips. Liberal use of proper coolants, ones providing good lubricity and antichip-weld characteristics, is recommended. In addition, the use of special brush attachments on cutting apparatus will help prevent accumulation of chips as the work passes through the saw. Table G.1 presents sawing data typical of data that manufacturers can provide. Data presented in Table G.2 and similar tables are based on average conditions and are intended only as typical starting points. Higher titanium speeds and feeds are being realized in plants using high-power tools and advanced technology methods. Abrasive Cutting. Titanium is easily cut with abrasive wheels when proper wheel compositions are employed and the work is flooded with coolant. Abrasive grains should fracture to expose fresh, sharp cutting edges. The wheel should be of the proper hardness to prevent rapid wear (too soft) or loading up (too hard). Cutting rates will probably vary from 6.5 to 19.5 cm2/min (1 to 3 in.2/min). Only silicon carbide wheels are recommended for titanium cutout operations. Aluminum oxide wheels are not satisfactory. Table G.2 lists recommended wheel types.

Hacksawing, band sawing data Power hacksaw

Material

Brinell hardness No.

Pitch, teeth per in., minimum thickness of material, in. Condition

Under 1 4

1

3 4 to 4

3

4 to 2

Power band saw Pitch, teeth per in., minimum thickness of material, in.

Over 2

Speed, strokes/min

Feed, in./stroke

Under 1 4

1

1 4 to 1 2

Over 11 2

Speed, fpm

Grade 1 Grade 2, grade 3, Ti-Pd Grade 4, 3Al-2.5V 5Al-2.5Sn, 5Al-2.5Sn-ELI, 6Al-2Nb-1Ta-1Mo, 4Al-3Mo-1V 6Al-4V, 6Al-4V-ELI, 8Mn 7 Al-4Mo, 8Al-1Mo-1V, 6Al-6V-2Sn 1Al-8V-5Fe 6Al-4V

110–170 140–200 200–275 300–340

Annealed Annealed Annealed Annealed

10 10 10 10

6 6 6 6

6 6 6 6

4 4 4 4

180 150 120 70

0.009 0.009 0.009 0.006

8–10 8–10 8–10 8–10

6–8 6–8 6–8 6–8

3–6 3–6 3–6 3–6

200 175 130 100

310–350 320–370

Annealed Annealed

10 10

6 6

6 6

4 4

60 50

0.006 0.005

8–10 8–10

6–8 6–8

3–6 3–6

90 80

320–375 350–375

10 10

6 6

6 6

4 4

30 30

0.003 0.003

8–10 8–10

6–8 6–8

3–6 3–6

70 70

13V-11Cr-3Al

310–350

Annealed Solution treated and aged Solution treated

10

6

6

4

25

0.003

8–10

6–8

3–6

60

fpm, feet per min. Use of a high-speed steel blade is assumed. Courtesy of RMI Company

314 / Titanium: A Technical Guide Table G.2 Recommended cutoff wheel material characteristics; titanium abrasive cutting Wheel characteristics

Value

Abrasive material Wheel width, in. Abrasive type Abrasive size Wheel hardness Structure Bond

Silicon carbide 1 to 3 8 16 37C(a) 60 L 6 Rubber Bar diameter

Machine setting

Up to 3.00 in.

Feed, in.2/min Speed, sfpm Cutting motion

2–4 7000–12,000 Oscillating wheel

Over 3.00 in.

5–6 6000–7000 Oscillating wheel and work rotation 10% water solution of rust inhibitor (nitrite-amine types); 10% water solution of soluble oil

Coolant

sfpm, surface feet per minute. (a) Norton code. Courtesy of Industrial Titanium Corp.

Machines with cutting heads capable of oscillating and plunging motions are best. For work with a cross-sectional area greater than 7.62 cm (3 in.), work rotation is necessary to minimize wheel wear, wheel breakage, and workpiece burning. Work rotation and use of oscillating heads minimize the amount of titanium surface being cut, thereby greatly reducing the tendency for the cutoff wheel to load up. Generous amounts of a water solution of nitrite rust inhibitor must be applied to the work during cutting. This is necessary to keep the cutting temperatures to a minimum and to avoid burning or heat checking the titanium. Although a 10% solution of nitrite rust inhibitor in water is recommended, soluble oils may be used if necessary. However, some soluble oils have a tendency to foam and lose a good part of their cooling power. Hacksawing. Hacksawing of titanium metal is basically a roughing operation. Problems encountered from galling, smearing, and high temperatures generated at the cutting edge of the teeth have, however, largely been overcome. Heavier, more rugged machine designs (for example, the Marvel heavy-duty No. 6 or 9 machine), blades, and full recognition of the value of the proper coolant—sulfo-chlorinated oil— have doubled blade life.

As in most titanium machining operations, surface speed must be kept low, and continual positive feed rates are to be employed. Coarse-pitched (3, 4, or 6 teeth/in.), high-speed steel blades have proved most successful. It is recommended that 3 or 4 teeth/in. be used on solid stock and 6 teeth/in. for tubing and shapes. Blade tension should be maintained at about 20 kN (4500 lbf). Successful blade characteristics are shown in Table G.3. The positive feed mechanism should govern the feed rate. The friction or variable feed should be kept medium. On alloy and heat-treatable grades, cutting rates of 6.5 to 13 cm2/min (1 to 2 in.2/min) can be obtained. Total area cut before a blade change is required will be about 1300 to 1936 cm2 (200 to 300 in.2). On commercially pure titanium grades, blade life and cutting rate are increased 50 to 100%. (See Table G.4). Forging Skin Caution. Initial cutting should never be attempted on scale or forging skin since a forging skin thickness of less than 0.025 mm (0.001 in.) may completely ruin a blade in a few strokes of the saw frame. Forging skin is best removed by turning or pickling. Satisfactory results also have been obtained by use of portable grinders to remove the skin. Some shops have used the expedient of trying an old blade to get under the skin and then substituting a new blade to complete the work. In general, this approach is never recommended since the danger of work hardening is ever-present. Band Sawing. Band sawing of titanium—on horizontal or vertical machines—is generally a freer operation than band sawing heat-resistant materials such as stainless steel. Further, if equipment is available, the band saw offers certain advantages over the hacksaw in cut-off operations on commercially pure grades of titanium. Four basic recommendations apply to band sawing operations, regardless of whether vertical or horizontal equipment is used:

• Work thickness determines the number of

blade teeth/mm (teeth/in.): 3 to 10 for inches. In general, the thicker the workpiece is, the less the number of teeth recommended.

Table G.4 Machine setting

Table G.3

Successful blade characteristics

Characteristic Teeth per in., number Blade width, in. Blade thickness, in.

Value

3, 4, and 6 1 1 2 (up to 10 in. capacity machine) 2 (over 10 in. capacity machine) 0.072 –0.075 (up to 10 in. capacity machine) 0.100 (over 10 in. capacity machine)

Courtesy of Industrial Titanium Corp.

Operational information Work size

Speed, … strokes/min Feed, 4–6 in./stroke Feed, 6–8 in./stroke Feed, 8–10 in./stroke Feed, 10 & over in./stroke

Commercially pure

90–100

All alloy grades

• •

fore the feed is fully increased. This will provide the greatest accuracy of cuts and prolong blade life. Positive feeds must be maintained once the work has been started. Use of coolant is required.

Saws employed for cutting stock up to 12.7 cm (5 in.) of cross section (for example, the Do All Company’s C-57 or C-58 automatic indexing model) have a blade life of 3900 to 6500 cm2 (600 to 1000 in.2). On equipment employed for larger stock (for example, the Do All C-24), the blade life is estimated at 6500 to 11 700 cm2 (1000 to 1800 in.2). Horizontal Band Sawing Machines (Cut-Off Sawing). Pitch selection is determined by the work thickness involved. As a general rule, the greater the work thickness is, the coarser the pitch will be. For example, for work thicknesses ranging from 10 to 15 cm (4 to 6 in.), coarse-pitched (6 teeth/in.), high-speed steel blades 2.5 cm (1 in.) wide, employed at speeds of 24 to 27 m2/min (80 to 90 ft2/min) have yielded the best results. Optimum cutting rates, providing a balance of good tool life and quality of cut have been established at 6.5 sq cm/min (1 sq in./min). With rigid setups, thin slabs are easily cut from barstock with an accuracy within 0.05 mm (0.002 in.) thickness variation per mm (in.) of work area. Effective feed force ranges from medium to medium-heavy. Table G.1 provides typical manufacturer’s data for sawing. A summary of blade characteristics found effective for band sawing either commercially pure or alloy grades of titanium is shown in Table G.5. Vertical Band Sawing Machines. Vertical band sawing machines are employed for either cut-off or contour operations. As in horizontal band sawing, coarse-pitched (6 teeth/in.), high-speed steel blades are employed at speeds of about 24 to 27 m2/min (80 to 90 ft 2/min). Blade width is 25.4 mm (1 in.) and the thickness is 0.889 mm (0.035 in.). Medium to medium-heavy feeding force is used. (Metric here is the approximate equivalent.)

Table G.5 Recommended blade characteristics

Annealed Heat treated

60–90

30–60

0.012

0.009

0.009

0.009

0.006

0.006

0.006

0.003

0.003

0.003

0.003

0003

Courtesy of Industrial Titanium Corp.

• The blade should be eased into the work be-

Characteristic

Blades Saw gage, in. Saw set, in. Pitch, teeth/in. Width, in. Velocity, surface ft/min Lubricant Feed force Cutting rate, in.2/min Courtesy of Industrial Titanium Corp.

Value

High-speed steel 0.042 0.065 raker 6 1 80 Sulfochlorinated oil Medium to medium-heavy 1.00

Machining Data / 315 Blade life is estimated at about 3870 to 6452 cm3 (600 to 1000 in.2). Equipment is constantly being improved, and a wide variety of refinements are available. Contour Sawing. Conventional contour sawing of titanium is an effective method for cutting shapes of all kinds, including bevelling, recessing, and so on. Fine-pitched (10 teeth/in.), high-speed steel bands have met with success in shaping material up to 19.1 mm (0.750 in.) thick. Blades of 6 to 8 teeth/in. are generally advised for material from 19.1 to 101.6 mm (0.750 to 4 in.) thick. Heavier work requires 2, 3, and 4 pitch blades. Medium-to-heavy feeding force is required with saw velocity geared to about 24 to 27 m2/min (80 to 90 ft2/min). Life expectancy of vertical band saw blades is about 3870 to 6452 cm2 (600 to 1000 in.2).

Table G.6

Turning Commercially pure and alloyed titanium can be turned with little difficulty. Carbide tools of the throwaway type should be used, wherever possible, for turning and boring titanium and titanium alloys because of the higher production rates attainable with them. The “straight” tungsten, carbide grades of standard designations C1 to C4, such as Metal Carbides C-91 and similar types, give the best results. Cobalt-type, high-speed steels appear to be the best of the many types of high-speed steel available. Cast-alloy tools may be used when carbide is not available and when the cheaper high-speed steels are not satisfactory. Overhang should be kept to a minimum in all cases to avoid deflection, thereby reducing the tendency of titanium to smear on the tool flank.

A heavy stream of cutting fluid should be applied constantly to the tool. Live centers must be used in turning, since seizing occurs on dead centers. It should be noted that manufacturers provide extensive technical data, which should be requested before initiating the kind of operations described here. Tool data are presented in Table G.6, based on average conditions, and are intended only as typical starting points. (Higher titanium speeds and feeds are being realized in plants using high-power tools and advanced technology methods.)

Drilling Successful drilling of titanium and titanium alloys requires the use of low surface speeds, heavy cuts (with controlled down feed if available), sharp tools of the correct geometry, rigid setups, and liberal amounts of coolant.

Single-point and box tools(a) Carbide tool High-speed steel tool Depth of cut, in.

Speed, fpm

Feed, ipr

Tool material

Tool geometry (a)

110–170

0.250 0.100 0.025

175 200 250

0.015 0.010 0.005

T-15 or M-3

Grade 2, grade 3, Ti-Pd Annealed

140–200

0.250 0.100 0.025

140 160 180

0.015 0.010 0.005

T-15 or M-3

Grade 4

Annealed

200–275

0.250 0.100 0.025

90 100 110

0.015 0.010 0.005

T-15 or M-3

5Al-2.5Sn, 5Al-2.5Sn-ELI(b), 6Al-2Nb-1Ta-1Mo, 4Al-3Mo-1V

Annealed

300–340

0.250 0.100 0.025

60 70 80

0.015 0.010 0.005

T-15 or M-3

6Al-4V, 6Al-4V-ELI(b)

Annealed

310–350

0.250 0.100 0.025

50 60 70

0.015 0.010 0.005

T-15 or M-3

7Al-4Mo, 8Al-1Mo-1V, 6Al-6V-2Sn

Annealed

320–370

0.250 0.100 0.025

40 50 60

0.015 0.010 0.005

T-15 or M-3

1Al-8V-5Fe

Annealed

320–380

0.250 0.100 0.025

15 20 30

0.015 0.010 0.005

T-15 or M-3

6Al-4V

Solution treated and aged

350–400

0.250 0.100 0.025

45 55 65

0.015 0.010 0.005

T-15 or M-3

SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief: 5°, NR:0.030 in. SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief: 5°, NR: 0.030 in. SR:5° BR:0°, SCEA: 15°, ECEA: 15°, Relief: 5°, NR: 0.030 in. SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief: 5°, NR:0.030 in. SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR: 0.030 in.

Material

Condition

Grade 1

Annealed

Brinell hardness No.

Speed, fpm Brazed tool

Throwaway tool

Feed, ipr

Tool material

400 450 500

450 500 550

0.015 0.010 0.005

C-2 C-2 C-3

325 375 425

375 425 475

0.015 0.010 0.005

C-2 C-2 C-3

225 250 275

275 310 350

0.015 0.010 0.005

C-2 C-2 C-3

150 180 215

185 220 250

0.015 0.010 0.005

C-2 C-2 C-3

125 150 170

160 180 210

0.015 0.010 0.005

C-2 C-2 C-3

110 130 155

150 165 185

0.015 0.010 0.005

C-2 C-2 C-3

70 90 115

90 110 135

0.015 0.010 0.005

C-2 C-2 C-3

100 120 145

140 160 185

0.015 0.010 0.005

C-2 C-2 C-3

Tool geometry(a)

SR: –5° BR: –5°, SR: –5° BR: –5, SR: –5° BR: –0,° SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in., SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR: 0.030 in. SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief: 5°, NR:0.030 in. SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in.

(continued) fpm, feet per min; ipr, in. per revolution; SR, side rake; BR, back rake; SCEA, side cutting edge angle; ECEA, end cutting edge angle; NR, nose radius. (a) Nominal tool life to be expected for the recommended turning conditions. High-speed steel or brazed carbide tool bits, 60 min.; throwaway carbide inserts, 30 min. (b) When 15° SCEA and ECEA are specified, it is assumed that throwaway tooling providing this geometry can be applied. Courtesy of RMI Company

316 / Titanium: A Technical Guide Table G.6

(continued) Carbide tool High-speed steel tool

Material

Condition

Brinell hardness No.

Depth of cut, in.

Speed, fpm

Feed, ipr

Tool material

6Al-6V-2Sn, 7Al-4Mo, Solution treated 4Al-3Mo-1V and aged

375–420

0.250 0.100 0.025

30 40 50

0.010 0.010 0.005

T-15

1Al-8V-5Fe

Solution treated and aged

375–440

0.250 0.100 0.025

20 25 35

0.010 0.010 0.005

T-15

13V-11Cr-3Al

Solution annealed

310–350

0.250 0.100 0.025

20 25 35

0.015 0.010 0.005

T-15 or M-3

13V-11Cr-3Al

Solution treated and aged

375–440

0.250

20

0.010

T-15

0.100 0.025

25 35

0.010 0.005

Speed, fpm Tool geometry(a)

Brazed tool

SR:15° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:15° BR:0°, SCEA:45°, ECEA:10°, Relief:5°, NR:0.030 in. SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:15° BR:0°, SCEA:45°, ECEA:10°, Relief:5°, NR:0.030 in.

Throwaway tool

Feed, ipr

Tool material

Tool geometry(a)

SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:–5° BR:–5°, SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in. SR:–5° BR:–5°,

80 100 120

100 120 150

0.010 0.010 0.005

C-2 C-2 C-3

60 80 100

80 100 120

0.010 0.010 0.005

C-2 C-2 C-3

80 100 125

100 120 150

0.015 0.010 0.005

C-2 C-2 C-3

60

80

0.010

C-2

80 100

100 120

0.010 0.005

C-2 C-3

SR:–5° BR:–5°, SR:5° BR:0°, SCEA:15°, ECEA:15°, Relief:5°, NR:0.030 in.

fpm, feet per min; ipr, in. per revolution; SR, side rake; BR, back rake; SCEA, side cutting edge angle; ECEA, end cutting edge angle; NR, nose radius. (a) Nominal tool life to be expected for the recommended turning conditions. High-speed steel or brazed carbide tool bits, 60 min.; throwaway carbide inserts, 30 min. (b) When 15° SCEA and ECEA are specified, it is assumed that throwaway tooling providing this geometry can be applied. Courtesy of RMI Company

These procedures reduce the amount of heat generated during cutting operations, thereby providing protection against dulling of the drill and galling and smearing on the cutting faces and margins. The major factors in successful titanium drilling are chip flow, clogging, and point smearing. These factors are determined by the depth of the hole drilled, which, in turn, determines drill life. Successful drilling can be accomplished with ordinary high-speed steel drills. One of the most important factors in drilling titanium is the length of the unsupported section of the drill. This portion of the drill should be no longer than necessary to drill the required depth, yet still allow the chips to flow unhampered through the flutes and out of the hole. This permits application of maximum cutting pressure, as well as rapid removal and re-engagement to clear chips, without drill breakage. Chip Flow. It is very important that drills be kept sharp and clean. (Titanium alloys may be difficult to drill unless correct cutting conditions are employed.) A dull drill, or one with smeared lips and margins, impedes the flow of chips along the flutes. A freshly ground drill will produce good chips; no drilling difficulty will be apparent. As the drill starts to become dull, chips flow with increasing difficulty, and some titanium remains stuck to the drill lips and margins. Soon the chips become packed and wedged in the flutes. The drill will fail, either by overheating or by seizing in the hole. Careful attention to chip formation in drilling of titanium should provide an accurate gage of the condition of the drill employed.

Uniform, smooth chips are produced by a sharp drill. When chips become shirred or feathered, the drill has dulled. When chips become discolored and irregular, the tool has failed. If the hole being drilled is to be tapped subsequently, generation of discolored chips may mean the workpiece has been ruined. Recommended Drilling Tools. Cobalt (T-4 or T-5) or molybdenum (M-10) high-speed steel drills have been found suitable for most drilling operations, while carbide drills seem especially useful for deep-hole drilling on long production runs. Stub-type screw machine drills or the shortest drills with shortest possible length of flute should be used. If the required hole depth makes such use impractical, drill jigs should be used to align the drill and prevent deflection. Without this protection, drills have a tendency to drift or break off in the hole. Increasing the web thickness also will increase the rigidity of the drill and help prevent deflection that causes chatter and uneven cutting action. Flutes should be large enough to prevent chips from clogging the drill. Drills should be long enough to provide unrestricted chip flow through the hole. All drill angles should be machine ground to assure correct tool geometry. (Hand grinding is not recommended.) Point angle is dependent on the hole diameter and operation involved (deep holes, sheet drilling, etc.). Blunt points (140°) are better suited to smaller diameter holes (6.35 mm, or 0.25 in., and less), while sharp points (90°) are more suited to large-diameter holes where higher pressures are employed to feed the drill. Double-point angle drills are recommended over single-point angle drills for

larger-size holes. The increased cutting surface on the double-point drill, which thins the chip and distributes the cutting load over a greater area of the cutting lip, provides approximately 25% greater drill life over single-point angle drills. Relief angles are important to drill life. Too small a relief angle causes smearing and galling on the cutting lips, while too high an angle causes tool failure by chipping on the cutting edge. Sheet drilling is best accomplished by a drill with no body clearance. The same general rules apply to the drilling of sheet as deep holes (i.e., use drills only long enough to accomplish the required job and use positive feeds). To reduce the required pressure to keep the drill cutting, it is sometimes wise to clear the web to the center, leaving no chisel point. Table G.7 arranges drilling data according to specific titanium grades and /or alloys. A more general approach, one organized according to operations, is given in Table G.8. Spiral-Point Drills. Grinding of spiral points on drills produces a tool with a marked superiority for most titanium drilling operations over the conventional chisel edge. Equipment is available for grinding the spiral point on any two-fluted, high-speed steel drill up to 50.8 mm (2 in.) diameter. Companies employing spiral-point drills report these type drills reduce the large negative rake angle of the chisel-edge drill; provide a proper clearance angle along the entire surface of the cutting edge; reduce thrust loading about 30%; and, because the spiral point terminates at its center in a sharp point, automatically center themselves on the axis of the drill when first engaging the workpiece. Use of spiral-point geometry also has made it largely unnecessary for

Machining Data / 317 When sheets are stack drilled, they should be clamped firmly together for optimum results. Operation. A positive feed must be maintained to prevent smearing and galling of the cutting lips, which produce rapid drill failure. Although hand-drilling operations are necessary in some cases, they should be kept to a minimum. Generally, hand drilling yields only 20 to 30% of the tool life that machine drilling yields. When drilling holes over one diameter deep, the drill should be retracted frequently to clear the drill flutes and holes of chips. The deeper the hole is drilled, the shorter the

employment of guide bushings to maintain proper location of a hole. When spiral-point drilling sheet, 180° point angles are recommended; the standard 118° angle is used for round or bar stock. Drills should be either chrome plated or oxide coated to resist galling and smearing on the drill margin. Setup. As in all machining operations, rigid machines and holding fixtures are a necessity when drilling titanium. In production operations, the use of drill jigs is recommended to prolong drill life and to prevent out-of-tolerance holes.

Table G.7

drill life will be. For deep, small-diameter holes, sulfochlorinated oils are the best coolant, and they should be supplied freely at the point of contact between work and tool. Oil-feeding drills may be used for larger diameter holes. Some shops report that no lubricant is required for drilling sheet when the hole depth is no greater than twice the drill diameter. At a depth-to-diameter ratio of 5:1 or greater, drill life may be reduced to 30% of that obtained at depth-to-diameter ratios of 3:1 or less. For this reason, designing of holes as shallow as possible is recommended.

Drilling data(a) Feed, in./revolution at nominal hole diam, in.:

Brinell

1

1 12

2

3

Tool material

Grade 1

Annealed

110–170

100

0.0005

0.002

0.006

0.007

0.008

0.010

0.013

0.015

M-1, M-10, M-2

Grade 2, grade 3, Ti-Pd

Annealed

140–200

80

0.0008

0.003

0.006

0.007

0.008

0.010

0.013

0.015

M-1, M-10, M-2

Grade 4

Annealed

200–275

50

0.002

0.005

0.006

0.007

0.008

0.010

0.013

0.015

M-1, M-10, M-2

3Al-2.5V

Annealed

200–260

50

0.002

0.005

0.006

0.008

0.009

0.010

0.012

0.013

M-1, M-10, M-2

5Al-2.5Sn, 5Al-2.5Sn-ELI, 6Al-2Nb-1Ta-1Mo, 4Al-3Mo-1V 6Al-4V, 8Mn

Annealed

300–340

40

0.002

0.005

0.006

0.007

0.008

0.010

0.011

0.012

M-1, M-10, M-2

Annealed

310–350

30

0.002

0.005

0.006

0.007

0.008

0.009

0.010

0.011

M-1, M-10, M-2

7Al-4Mo, 8Al-1Mo-1V, 6Al-6V-2Sn

Annealed

320–370

20

0.002

0.005

0.006

0.007

0.008

0.009

0.010

0.011

M-1, M-10, M-2

1Al-8V-5Fe

Annealed

320–380

15

0.002

0.004

0.005

0.006

0.007

0.008

0.009

0.010

T-15, M-33

6Al-4V

Solution treated and aged

350–400

25

0.001

0.002

0.004

0.005

0.006

0.007

0.008

0.008

T-15, M-33

6Al-6V-2Sn, 7Al-4Mo, 4Al-3Mo-1V

Solution treated and aged

375–420

20

0.001

0.002

0.003

0.004

0.004

0.005

0.005

0.005

T-15, M-33

1Al-8V-5Fe

Solution treated and aged

375–440

15

0.0005

0.001

0.0015

0.0015

0.002

0.002

0.003

0.004

T-15, M-33

13V-11Cr-3Al

Solution annealed

310–350

20

0.001

0.003

0.004

0.005

0.006

0.007

0.008

0.009

M-1, M-10, M-2

13V-11Cr-3Al

Solution treated and aged

375–440

15

0.0005

0.001

0.0015

0.0015

0002

0.002

0.003

0.004

T-15, M-33

Material

Condition

hardness No.

Speed, fpm

1

8

1

4

1

2

3

4

Tool geometry

Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7 °, PG: crankshaft Stub length drill, PA: 118 °, lip Cl: 7° PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: Crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft Stub length drill, PA: 118°, lip Cl: 7°, PG: crankshaft

fpm, feet per min; PA, point angle; Cl, clearance. (a) Nominal tool life to be expected for the recommended drilling conditions using high-speed steel drills, 75 holes, for 2 to 1 depth-to-diameter ratio. Courtesy of RMI Company

318 / Titanium: A Technical Guide Reaming Holes drilled or bored for the reaming of titanium and titanium alloys should be 0.254 to 0.058 mm (0.010 to 0.020 in.) undersize. Standard high-speed steel and carbide reamers perform satisfactorily, except that clearance on the chamfer should be 10°. To provide maximum tooth space for chip clearance, reamers with the minimum number of flutes for a given size should be selected. Remaining data presented in Table G.9 are based on average conditions and are intended only as typical starting points.

Tapping It is essential that straight, clean holes be drilled to assure good tapping results, since variations in diameter and tapered holes are detrimental to this work. Sound threads can be assured by reducing the tendency of the titanium to smear on the lands of the tap and by providing for a free flow of chips in the flutes. Failure to do this will result in poor threads, undersize holes, seizures, and, consequently, broken taps. Best results in tapping titanium have been with a 65% thread. One common problem is the smear of titanium on the land of the tap, which can result in the tap freezing or binding in the hole. An activated cutting oil such as a sulfurized and chlorinated oil is helpful in avoiding this problem. The use of nitrided taps also helps to reduce adherence of titanium to the lands of the tap. Relieving the land or the use of an interrupted tap also helps minimize the smearing tendency. Chip removal is a problem that makes tapping one of the more difficult machining operations. Chip clogging is reduced by the use of spiral pointed taps, which push the chips ahead of the tool. More chip clearance can be provided by sharply grinding away the trailing edges of the flutes. To give proper clearance, two-fluted, spiral point taps are recommended for diameters up to 5 16 in.; use three-fluted taps for larger sizes. Tapping data presented in Table G.10 are based on average conditions and are intended only as typical starting points.

There is a tendency for titanium chips to weld to the tool during an interrupted cut such as broaching. This tendency increases as the wearland develops. Both the broach and broach slots should be examined regularly for signs of smearing in order to avoid poor finish, more rapid tool wear, and loss of tolerances.

Milling Face Milling. Data are presented in Table G.12, based on average conditions. The life of face milling cutters can be lengthened through the use of a “climb milling” setup, with an antibacklash device on the table feed screw. Titanium chips tend to weld to the edge of the milling cutter and, when knocked

Table G.8

off on re-entering the metal, carry a portion of the cutting edge with them. This is especially true of carbide cutters. Climb milling produces a thin chip as the cutter teeth leave the work, thus reducing the tendency of the chip to weld to the cutting edge. As in all titanium machining work, sharp tools must be used to reduce galling and welding tendencies. Relief or clearance angles for face milling cutters should be greater than those used for steel. The use of a water base coolant is recommended. In milling titanium, when the cutting edge fails, it is usually because of chipping. Thus, the results with carbide tools are often less satisfactory than with cast-alloy tools. The increase of 20 to 30% in cutting speeds (which is possible with carbide tools as contrasted with cast-alloy tools) does not always compensate

Recommended tool materials, angles, and machine settings for drilling

Type of operation

Tool material

General drilling Deep holes, low production Deep holes, high production Sheet, power drilling Sheet, hand drilling

T-4 or T-5 high-speed steel (HSS) T-5 HSS C-1 or C-2 carbide T-4, T-5, or M-10, HSS M-10, T-4 or T-5 HSS Tool geometry

Operation

Tool angle

General and deep hole drilling

Point angle, ° Less than 1 4 diam 1 to 1 diam 4 2 Helix angle, ° Relief angle, ° Cutting angle, ° Body clearance Point angle, ° Less than 1 4 diam 1 to 1 diam 4 2 Helix angle, ° Relief angle, ° Cutting angle, ° Body clearance Point angle, ° Less than1 4 diam 1 to 1 diam(a) 4 2 Helix angle, ° Relief angle , ° Cutting angle, ° Body clearance

Sheet, power drilling

Sheet, hand drilling

Broaching data are presented in Table G.11 based on average conditions. To assure a quality broaching job, it is essential that the entire machine tool setup and the titanium component be rigid. It is also recommended that broaches be wet ground to improve the finish of the tool, thereby giving better tool performance. During the broaching operation, vapor blasting with the coolant helps to length broach life and to reduce smearing.

Carbide

140 90 or double angle 28–35 9–10 0 Yes

Single lip Gun drill … 6–8 … …

135 118 15 12–15 0 Yes

Not recommended Not recommended

150 135 15 12–15 0 No

Not recommended Not recommended

Operational information Titanium, all alloy grades Commercially pure titanium

Broaching

High-speed steel

General and deep hole drilling with HSS Speed, sfpm Feed, ipr Less than 1 8 diam 1 – 1 diam 8 4 1 –1 diam 4 2 Drilling deep holes with carbide drills Speed, sfpm Feed, ipr Sheet drilling with HSS Speed, sfpm Feed, ipr

Annealed

Heat treated

40–60

20–50

5–40

0.0015 0.002–0.005 0.005–0.009

0.0015 0.002–0.005 0.005–0.009

0.0015 0.002–0.005 0.005–0.009

200 0.0005

100–170 0.0005

75–145 0.0005

15–40 0.002–0.005(b)

20–30 0.002–0.005(b)

10.25 0.002–0.005(b)

sfpm, surface feet per minute; ipr, inches per revolution. (a) Freehand drilling not recommended over 5 16 diam. (b) Hand drilling titanium requires approximately twice the axial force for drilling aluminum. Courtesy of Industrial Titanium Corp.

Machining Data / 319 Table G.9

Reaming data(a) High-speed steel tool

Carbide tool

Feed, ipr

Material

Brinell Speed, hardness No. fpm

Feed, ipr

Nominal hole diam, in. 1

8

1

4

1

2

1

11 2

2

Tool material

Tool geometry

Speed, fpm

Nominal hole diam, in. 1

8

1

4

1

2

1

11 2

2

Tool material

Tool geometry

RR: 6°, Helix: 7°, Per. relief: 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix: 7°, Per. relief: 10 °, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix 7°, Per relief: 10°, CA: 45° Lead angle: 2° × 3 16 in. RR: 6° Helix: 7°, Per. relief: 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix: 7°, Per. relief, 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix: 7°, Per. relief: 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix: 7°, Per. relief: 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix 7°, Per. relief: 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix: 7°, Per. relief: 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6 °, Helix: 7°, Per. relief: 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix: 7° Per. relief: 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix: 7°, Per. relief: 10°, CA: 45°, Lead angle: 2° × 3 16 in. RR: 6°, Helix: 7°, Per. relief: 10°, CA: 45°, Lead angle 2° × 3 16 in.

Grade 1, annealed

110–170

100 0.003 0.006 0.009 0.012 0.015 0.020 M-1 or M-2 Right hand, Helix: 10°, CA: 45 °, Per. relief: 10°

375 0.003 0.006 0.009 0.012

0.015 0.020

C-2

Grade 2, grade 3, Ti-Pd, annealed

140–200

80

0.003 0.006 0.009 0.012 0.015 0.020 M-1 or M-2 Right hand, Helix: 10°, CA: 45°, Per. relief: 10°

300 0.003 0.006 0.009 0.012

0.015 0.020

C-2

Grade 4, annealed

200–275

70

0.003 0.005 0.008 0.011 0.014 0.016

Right hand, Helix: 10°, CA: 45°, Per. relief: 10°

250 0.003 0.005 0.008 0.011

0.014 0.016

C-2

3Al-2.5V, annealed

200–260

60

0.003 0.005 0.007 0.009 0.012 0.015 M-1 or M-2 Right hand, Helix: 10°, CA: 45°, Per. relief: 10°

250 0.003 0.005 0.007 0.009

0.012 0.015

C-2

5Al-2.5Sn, 5Al-2.5Sn-ELI, 6Al-2Nb-1Ta-1Mo, 4Al-3Mo-1V, annealed

300–340

45

0.002 0.005 0.007 0.009 0.012 0.015

M-2

Right hand, Helix:10 °, CA: 45°, Per. relief: 10°

175 0.002 0.005 0.007 0.009

0.012 0.015

C-2

6Al-4V, 6Al-4V-ELI, 8Mn, annealed

310–350

35

0.002 0.005 0.007 0.009 0.012 0.015

M-2

Right hand, Helix: 10°, CA: 45°, Per. relief: 10°

150 0.002 0.005 0.007 0.009

0.012 0.015

C-2

7Al-4Mo, 8Al-1Mo-1V, 6Al-6V-2Sn, annealed

320–370

30

0.002 0.005 0.007 0.009 0.012 0.015

M-2

Right hand, Helix: 10°, CA: 45°, Per. relief: 10°

120 0.002 0.005 0.007 0.009

0.012 0.015

C-2

1Al-8V-5Fe, annealed

320–380

30

0.002 0.005 0.007 0.009 0.012 0.015

M-2

Right hand, Helix: 10°, CA: 45°, Per.relief:10°

120 0.002 0.005 0.007 0.009

0.012 0.015

C-2

6Al-4V, solution treated and aged

350–400

30

0.002 0.005 0.007 0.009 0.012 0.015

M-2

Right hand, Helix: 10°, CA: 45°, Per.relief:10°

120 0.002 0.005 0.007 0.009

0.012 0.015

C-2

6Al-6V-2Sn, 7Al-4Mo, 4Al-3Mo-1V, solution treated and aged

375–420

25

0.002 0.005 0.007 0.009 0.012 0.015

M-2

Right hand, Helix: 10°, CA: 45°, Per. relief: 10°

100 0.002 0.005 0.007 0.009

0.012 0.015

C-2

1Al-8V-5Fe, solution treated and aged

375–440

25

0.002 0.004 0.006 0.008 0.010 0.012

M-2

Right hand, Helix: 10°, CA: 45°, Per. relief: 10°

100 0.002 0.004 0.006 0.008

0.010 0.012

C-2

13V-11Cr-3Al, solution annealed

310–350

30

0.002 0.005 0.007 0.009 0.012 0.015

M-2

Right hand, Helix: 10°, CA: 45°, Per.relief:10°

150 0.002 0.005 0.007 0.009

0.012 0.015

C-2

13V-11Cr-3Al, solution treated and aged

375–440

25

0.002 0.004 0.006 0.008 0.010 0.012

M-2

Right hand, Helix: 10°, CA: 45°, Per. relief: 10°

100 0.002 0.004 0.006 0.008

0.010 0.012

C-2

M-2

fpm, feet per min; CA, cutting angle, Per. relief, peripheral relief; RR, radial rake. (a) Nominal tool life to be expected for the recommended reaming conditions, high-speed steel and carbide reamers, 75 holes, for 2 to 1 depth-to-diameter ratio. Courtesy of RMI Company

320 / Titanium: A Technical Guide for the additional tool grinding costs. Consequently, it is advisable to try both cast-alloy and carbide tools to determine the better of the two for each milling job. For slab milling, the work should move in the same direction as the cutting teeth. For face milling, the teeth should emerge from the cut in the same direction as the work is fed. End Milling: Slotting. Data are presented in Table G.13, based on average conditions. Titanium end milling is, for the most part throughout industry, done with high-speed steel cutters. Cutters as short as possible are used. In this machining method, the tooth length-to-diameter ratio is high; thus, considerable tool deflection takes place. This condition is extremely critical with carbide cutters. Cutters should have sufficient flute space to prevent chip clogging and subsequent tool failure. Cutters up to 25.4 mm (1 in.) diameter should have three to four flutes. End Milling: Peripheral. Data are presented in Table G.14, based on average condiTable G.10

tions. High-speed steel cutters are preferred throughout industry for peripheral work, since the lack of rigidity inherent in this method is critical for carbide cutters. Here, too, cutters should be as short as possible to reduce tool deflection. Cutters should have sufficient flute space to prevent chip clogging and early cutter failure. Cutters up to 25.4 mm (1 in.) diameter should have three to four flutes. Climb milling also should be employed on peripheral milling. This produces thinner chips as the cutter teeth leave the work, thereby reducing the tendency of chips to weld to the cutter and then to break off portions of the cutting edge as they re-enter the work. Climb milling thus lengthens cutter life.

Surface Grinding The proper combination of grinding fluid, abrasive wheel, and wheel speeds can expedite

the shaping of titanium by means of surface grinding. The procedure recommended is to use considerably lower wheel speeds than in conventional grinding of steels. Abrasives recommended by a leading manufacturer of grinding wheels are silicon carbide wheels for cut-off and portable grinding, and aluminum oxide wheels for cylindrical and surface grinding. The following guidelines generally and typically apply to grinding operations:

• A sharply dressed wheel should be used. • The largest wheel diameter and thickness that are feasible should be used.

• Harder wheels should be used. • Ample power should be available at the spindle for grinding.

Reduced wheel speeds, as contrasted with those employed with steel, aid in grinding performance. In surface grinding, for example, 279 sm2/min (3000 sft2/min) has been

Tapping data(a)

Material

Condition

Brinell hardness No.

Speed, fpm

Grade 1

Annealed

110–170

50

Nitrided, M-1, M-10

HSS tool material

Grade 2, grade 3, Ti-Pd

Annealed

140–200

40

Nitrided, M-1, M-10

Grade 4

Annealed

200–275

30

Nitrided, M-1, M-10

5Al-2.5Sn, 5Al-2.5Sn-ELI, 6Al-2Nb-1Ta-1Mo, 4Al-3Mo-1V, 6Al-4V, 6Al-4V-ELI

Annealed

300–340

25

Nitrided, M-1, M-10

Annealed

310–350

20

Nitrided, M-1, M-10

7 Al-4Mo, 8 Al-1Mo-1V, 6Al-6V-2Sn

Annealed

320–370

15

Nitrided, M-1, M-10

1Al-8V-5Fe

Annealed

320–380

10

Nitrided, M-1, M-10

6Al-4V

Solution treated and aged

350–400

10

Nitrided, M-1, M-10 M-1, M-10

6Al-6V-2Sn, 7Al-4Mo, 4Al-3Mo-1V

Solution treated and aged

375–420

10

Nitrided, M-1, M-10

1Al-8V-5Fe

Solution treated and aged

375–440

7

Nitrided, M-1, M-10

13V-11Cr-3Al

Solution annealed

310–350

15

Nitrided, M-1, M-10

13V-11Cr-3Al

Solution treated and aged

375–440

7

Nitrided, M-1, M-10

Tool geometry

2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point — Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 in. tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap 2 flute spiral point— 5 tap and smaller. 16 3 flute spiral point— Larger than 5 16 in. tap

HSS, high-speed steel; fpm, feet per min. (a) Nominal tool life to be expected for the recommended tapping conditions, high-speed steel taps, 75 holes, for 2 to 1 depth-to-diameter ratio. Courtesy of RMI Company

Machining Data / 321 found to cause minimum surface stresses and distortion. The basic reasons for using slower wheel speeds when grinding titanium are:

• Minimize high temperatures that would develop at the chip-grit interface

• Minimize temperature-sensitive reactions in material being ground

• Mitigate problems associated with the abra• • •

sive character of titanium Minimize wheel loading Minimize or prevent smearing Lower the potential bazard for a titanium fire

To minimize residual stresses in the ground surfaces of titanium parts, the following down feeds should be employed: 0.025 mm/pass to last 0.051 mm; then 0.0127 mm, 0.0102 mm, 0.0076 mm, 0.0051 mm, 0.0025 mm/pass (0.001 in./pass to last 0.002 in., then 0.0005 in., 0.0004 Table G.11

in., 0.0003 in., 0.0002 in., 0.0001 in./pass), no sparkout. Nitride amine base fluids have been successfully used in a majority of operations. A watersodium nitrite mixture gives excellent results as a coolant. For form grinding, straight grinding oil is recommended. Because of the potential fire hazard when grinding titanium in the presence of a grinding oil, especially at increased speeds, the following precautions should be taken:

• Extra cutting fluid lines should be installed to quench the sparking as much as possible.

• Filters should be installed, whenever possi• •

ble, to remove the fine titanium particles from the cutting fluid. External surfaces of the machines should be cleaned of titanium dust frequently. Oil is to be changed more often than is customary with steels.

• Material such as soapstone should be available in the vicinity of the machine to quench any fires.

Thermal Cutting Oxygen cutting is a very suitable and economical process for fabrication operations. Oxyacetylene cutting of titanium can be performed using the same procedures as for steel and at speeds several times as fast. Line cutting, shape cutting, and severing of heavy sections is relatively easy. Preheating of the edge is necessary for starting the cut as with steel. If the metal is heavily scaled, scale removal by grinding may be ncessary at the starting edge. Metal reaction with the cutting gases is limited to a few thousandths of an inch. The original chemical quality of the cut surface can be restored by

Broaching data(a) High speed steel tool

Material

Condition

Brinell hardness No.

Type of cut

Speed, fpm

Chip load, in./tooth

Tool material

Tool geometry

Grade 1

Annealed

110–170

Roughing

35

0.005–0.008

T-5

Finishing

55

0.002–0.005

T-5

Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8° 10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°– 3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3° Hook angle: 8°–10° Cl: 3°–4° Hook angle: 8°–10° Cl: 2°–3°

Grade 2, grade 3, Ti-Pd

Annealed

140–200

Roughing Finishing

30 45

0.005– 0.008 0.002–0.005

T-5 T-5

Grade 4

Annealed

200–275

Roughing Finishing

20 30

0.004 –0.007 0.002 –0.004

T-5 T-5

5Al-2.5Sn, 5Al-2.5Sn-ELI, 6Al-2Nb-1Ta-1Mo, 4Al-3Mo-1V 6Al-4V, 6Al-4V-ELI, 8Mn

Annealed

300–340

Roughing Finishing

15 22

0.003–0.006 0.0015 –0.003

T-5 T-5

Annealed

310–350

Roughing Finishing

12 18

0.003–0.006 0.0015–0.003

T-5 T-5

7Al-4Mo, 8Al-1Mo-1V, 6Al-6V-2Sn

Annealed

320–370

Roughing Finishing

10 16

0.003 –0.006 0.0015 –0.003

T-5 T-5

1Al-8V-5Fe

Annealed

320–380

Roughing Finishing

8 14

0.002–0.005 0.0015–0.0025

T-5 T-5

6Al-4V

Solution treated and aged

350–400

Roughing Finishing

8 12

0.002–0.005 0.001–0.002

T-15 T-15

6Al-6V-2Sn, 7Al-4Mo, 4Al-3Mo-1V

Solution treated and aged

375–420

Roughing Finishing

7 10

0.002–0.004 0.001–0.002

T-15 T-15

1Al-8V-5Fe

Solution treated and aged

375–440

Roughing Finishing

6 9

0.002–0.004 0.001–0.002

T-15 T-15

13V-11Cr-3Al

Solution annealed

310–350

Roughing Finishing

11 17

0.003–0.006 0.0015 –0.003

T-5 T-5

13V-11Cr-3Al

Solution treated and aged

375–440

Roughing Finishing

6 9

0.002– 0.004 0.001– 0.002

T-15 T-15

Cl, clearance; fpm, feet per min. (a) Due to the complexity of most broaching tools and the configurations machined, general predictions of broach life are not practical. Courtesy of RMI Company

322 / Titanium: A Technical Guide light grinding to obtain a clean metal surface. The heat-affected zone, in which microstructure transformations occur, is generally not more than 0.254 mm (0.10 in.) deep and is only slighty harder than the unaffected metal. Gas tungsten-arc cutting is also suitable for cutting titanium, but the quality of the cut edge is generally inferior to that obtained with oxyacetylene cutting. Table G.12

• Machining Data Handbook, 3rd ed., Metcut

SELECTED REFERENCES The following listing provides references that contain tool life charts. These items may prove very helpful when making selections for milling titanium.

•

• “Machining,” Metals Handbook Desk Edi-

•

tion, 2nd ed., ASM International, 1998, p 933–935 , 945–950

Research Associates, Inc., Machinability Data Center, Cincinnati, OH, 1980 N. Zlatin, “Establishment of Production Machinability Data,” USAF Technical Report AFML-TR-75-120, Metcut Research Associates, Inc., Cincinnati, OH, 1975 N. Zlatin, J.D. Christopher, and J.T. Cammett, “Machining of New Materials,” USAF Technical Report AFML-TR-73-165,

Face milling data(a)

Material

Condition

Brinell hardness No.

High-speed steel tool

Carbide tool

Depth of cut, in.

Speed, fpm

Feed, in./tooth

Tool material

Tool geometry

AR: 0°, RR: 0°, ECEA: 6°, Cl: 12°, CA: 30° AR: 0°, RR: 0°, ECEA: 6°, Cl: 12°, CA: 30° AR: 0°, RR: 0°, ECEA: 6°, Cl: 12°, CA: 30° AR: 0°, RR: 0°, ECEA: 6°, Cl: 12°, CA: 30° AR: 0°, RR: 0°, ECEA: 6°, Cl: 12°, CA: 30° AR: 0°, RR: 0°, ECEA: 6°, Cl: 12°, CA: 30° AR: 10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45° AR: 10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45° AR: 10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45° AR:10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45° AR: 10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45° AR: 10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45°

Grade 1

Annealed

110–170

0.250 0.050

125 175

0.008 0.004

M-2

Grade 2, grade 3, Ti-Pd

Annealed

140–200

0.250 0.050

100 140

0.006 0.004

M-2

Grade 4

Annealed

200–275

0.250 0.050

75 110

0.006 0.004

M-2

5Al-2.5Sn, 5Al-2.5Sn-ELI, 6Al-2Nb-1Ta-1Mo, 4Al-3Mo-1V

Annealed

300–340

0.250 0.050

50 60

0.006 0.004

M-3 or T-15

6Al-4V, 6Al-4V-ELI, 8Mn

Annealed

310–350

0.250 0.050

40 50

0.006 0.004

M-3 or T-15

7Al-4Mo, 8Al-1Mo-1V, 6Al-6V-2Sn

Annealed

320–370

0.250 0.050

30 40

0.006 0.004

T-15 or M-3

1Al-8V-5Fe

Annealed

320–380

0.250 0.050

20 30

0.006 0.004

T-15

6Al-4V

Solution treated and aged

350–400

0.250 0.050

35 45

0.007 0.004

T-15

6Al-6V-2Sn, 7Al-4Mo, 4Al-3Mo-1V

Solution treated and aged

375–420

0.250 0.050

25 35

0.007 0.004

T-15

1Al-8V-5Fe

Solution treated and aged

375–440

0.250 0.050

20 25

0.007 0.004

T-15

13V-11Cr-3Al

Solution annealed

310–350

0.250 0.050

25 35

0.006 0.004

T-15

13V-11Cr-3Al

Solution treated and aged

375 –440

0.250 0.050

20 25

0.007 0.004

T-15

Speed, fpm Feed, ln./tooth Tool material Tool geometry

400 500

0.008 0.004

C-2 C-2

300 400

0.006 0.004

C-2 C-2

200 300

0.006 0.004

C-2 C-2

170 210

0.006 0.004

C-2 C-2

130 170

0.006 0.004

C-2 C-2

110 150

0.006 0.004

C-2 C-2

90 120

0.006 0.004

C-2 C-2

110 130

0.006 0.004

C-2 C-2

80 100

0.006 0.004

C-2 C-2

60 70

0.006 0.004

C-2 C-2

100 130

0.006 0.004

C-2 C-2

60 70

0.006 0.004

C-2 C-2

AR: 0°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45° AR: 0°, RR 0°, ECEA: 10°, Cl: 10°, CA: 45° AR: 0°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45° AR: 0°, RR: 10°, ECEA: 12°, Cl: 12°, CA: 30° AR: 0°, RR: 10°, ECEA: 12°, Cl: 12°, CA: 30° AR: 0° RR: –10°, ECEA: 12°, Cl: 12°, CA: 30°, AR: 0°, RR: –10°, ECEA: 12°, Cl: 12°, CA: 30° AR: 10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45°, AR: 10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45° AR: 10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45° AR: 0°, RR: –10°, ECEA: 12°, Cl: 12°, CA: 30° AR: 10°, RR: 0°, ECEA: 10°, Cl: 10°, CA: 45°

fpm, feet per min; AR, axial rake; RR, radial rake: ECEA, end cutting edge angle; cl, clearance; CA, cutting angle. (a) Nominal tool life to be expected for the recommended face milling conditions, high-speed steel and carbide cutters, 50 in./tooth. Courtesy of RMI Company

Machining Data / 323

Table G.13

End milling: slotting data(a) High-speed steel tool

Material

Brinell Depth of hardness No. cut, in.

Speed, fpm

Feed, in./tooth; Cutter diam, in. 1

8

3

8

3

4

1–2

Tool material

Grade 1, annealed

110–170

0.250 0.125 0.050 0.015

80 100 125 150

… … 0.0005 0.0005

0.0015 0.002 0.003 0.003

0.004 0.005 0.006 0.006

0.006 0.006 0.007 0.007

M-2 M-2 M-2 M-2

Grade 2, grade 3, Ti-Pd, annealed

140–200

0.250 0.025 0.050 0.015

70 90 120 150

… … 0.0005 0.0005

0.0015 0.002 0.003 0.003

0.004 0.005 0.006 0.006

0.006 0.006 0.007 0.007

M-2 M-2 M-2 M-2

Grade 4, annealed

200–275

0.250 0.125 0.050 0.015

40 50 60 75

… … 0.0005 0.0007

0.0007 0.001 0.002 0.003

0.003 0.003 0.004 0.005

0.004 0.004 0.005 0.006

M-2 M-2 M-2 M-2

5Al-2.5Sn, 300–340 5Al-2.5Sn-ELI, 6Al-2CNb-1Ta-1Mo, 4Al-3Mo-1V, annealed

0.250 0.125 0.050 0.015

35 45 55 70

… … 0.0005 0.0007

0.0007 0.001 0.002 0.003

0.003 0.003 0.004 0.005

0.004 0.004 0.005 0.006

M-2 M-2 M-2 M-2

6Al-4V, 6Al-4V-ELI, 8Mn, annealed

310–350

0.250 0.125 0.050 0.015

30 40 50 65

… … 0.0005 0.0007

0.0007 0.001 0.002 0.003

0.003 0.003 0.004 0.005

0.004 0.004 0.005 0.006

M-2 M-2 M-2 M-2

7Al-4Mo, 8Al-1Mo-1V, 6Al-6V-2Sn, annealed

320–370

0.250 0.125 0.050 0.015

30 35 45 55

… … 0.0005 0.0007

0.0007 0.001 0.002 0.003

0.003 0.003 0.004 0.005

0.004 0.004 0.005 0.006

M-2 M-2 M-2 M-2

1Al-8V-5Fe, annealed

320–380

0.250 0.125 0.050 0.015

25 30 35 45

… … 0.0005 0.0007

0.0007 0.001 0.002 0.003

0.003 0.003 0.004 0.005

0.004 0.004 0.005 0.006

M-2 M-2 M-2 M-2

6Al-4V, Solution treated and aged

350–400

0.250 0.125 0.050 0.015

25 30 35 45

… … 0.0006 0.001

0.0006 0.001 0.002 0.003

0.002 0.003 0.003 0.004

0.003 0.004 0.004 0.006

M-2 M-2 M-2 M-2

6Al-6V-2Sn, 7Al-4Mo, 4Al-3Mo-1V, Solution treated and aged

375–420

0.250 0.125 0.050 0.015

25 30 35 45

… … 0.0006 0.0008

0.0005 0.001 0.0015 0.003

0.001 0.002 0.003 0.004

0.002 0.003 0.004 0.006

M-2 M-2 M-2 M-2

1Al-8V-5Fe, Solution treated and aged

375–440

0.250 0.125 0.050 0.015

20 25 35 45

… … 0.0003 0.0005

0.0004 0.0007 0.0015 0.002

0.001 0.002 0.002 0.003

0.002 0.003 0.004 0.005

M-2 M-2 M-2 M-2

13V-11Cr-3Al, Solution annealed

310–350

0.250 0.125 0.050 0.015

30 35 45 55

… … 0.0005 0.0007

0.0007 0.001 0.002 0.003

0.003 0.003 0.004 0.005

0.004 0.004 0.005 0.006

M-2 M-2 M-2 M-2

13V-11Cr-3Al, Solution treated and aged

375–440

0.250 0.125 0.050 0.015

20 25 35 45

… … 0.0003 0.0005

0.0004 0.0007 0.0015 0.002

0.001 0.002 0.002 0.003

0.002 0.003 0.004 0.005

M-2 M-2 M-2 M-2

Carbide tool Tool geometry

Feed, in./tooth; Cutter diam, in. Speed,fpm

Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in.(b) Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in.(b) Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in.(b) Helix: 30°, RR: 10°, End Cl: 3°, Per. C: 7°, ECEA 3°, CA: 45° × 0.60 in.(b) Helix: 30°, RR: 10°, End Cl: 3°, Per. C: 7°, ECEA: 3°, CA: 45° × 0.60 in.(b) Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in.(b) Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in.(b) Helix 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in.(b) Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in.(b) Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7° ECEA: 3°, CA: 45° × 0.060 in.(b) Helix:, 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in.(b) Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in.(b)

1

8

3

8

3

4

1–2

Tool material

200 … 250 … 325 0.001 375 0.001

0.0015 0.0015 0.002 0.002

0.003 0.003 0.004 0.004

0.005 0.005 0.006 0.006

C-2 C-2 C-2 C-2

175 … 225 … 300 0.001 375 0.001

0.0015 0.0015 0.002 0.002

0.003 0.003 0.004 0.004

0.005 0.005 0.006 0.006

C-2 C-2 C-2 C-2

100 … 0.0007 125 … 0.0015 160 0.0005 0.002 190 0.0005 0.003

0.003 0.003 0.005 0.006

0.005 0.005 0.007 0.008

C-2 C-2 C-2 C-2

90 … 0.0007 110 … 0.0015 140 0.0005 0.002 175 0.0005 0.003

0.003 0.003 0.005 0.006

0.005 0.005 0.007 0.008

C-2 C-2 C-2 C-2

75 … 0.0007 100 … 0.0015 125 0.0005 0.002 165 0.0005 0.003

0.003 0.003 0.005 0.006

0.005 0.005 0.007 0.008

C-2 C-2 C-2 C-2

75 … 0.0007 90 … 0.015 115 0.0005 0.002 140 0.0005 0.003

0.003 0.003 0.005 0.006

0.005 0.005 0.007 0.008

C-2 C-2 C-2 C-2

60 … 0.0007 75 … 0.0015 90 0.0005 0.002 115 0.001 0.003

0.003 0.003 0.005 0.006

0.005 0.005 0.007 0.008

C-2 C-2 C-2 C-2

60 … 0.0006 75 … 0.001 90 0.0006 0.002 115 0.001 0.003

0.003 0.003 0.004 0.005

0.004 0.005 0.006 0.007

C-2 C-2 C-2 C-2

60 … 0.0006 75 … 0.001 90 0.0005 0.0015 115 0.001 0.003

0.003 0.003 0.004 0.005

0.004 0.004 0.006 0.007

C-2 C-2 C-2 C-2

50 … 0.0004 60 … 0.0007 90 0.0005 0.002 115 0.0007 0.002

0.001 0.002 0.003 0.004

0.002 0.004 0.005 0.006

C-2 C-2 C-2 C-2

75 … 0.0007 90 … 0.0015 115 0.0005 0.002 140 0.001 0.003

0.003 0.003 0.005 0.006

0.005 0.005 0.007 0.008

C-2 C-2 C-2 C-2

50 … 0.0004 60 … 0.0007 90 0.0005 0.002 115 0.0007 0.002

0.001 0.002 0.003 0.004

0.002 0.004 0.005 0.006

C-2 C-2 C-2 C-2

Tool geometry

Helix: 15°, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA:45° × 0.40in. Helix: 15°, RR: 0°, End: Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA:45°×0.040in. Helix: 15°, RR: 0°, End Cl: 12° Per. Cl: 12°, ECEA: 3°, CA:45°×0.040in. Helix: 15°, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA 45°× 0.40 in. Helix: 15°, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA:45° × 0.40in. Helix: 15°, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA:45°×0.040in. Helix: 15°, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA:45°×0.040in. Helix: 15°, RR: 0° End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA:45° × 0.040in. Helix: 15°, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.40 in. Helix: 15°, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA:45° × 0.040in. Helix: 15°, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA:45° × 0.040in. Helix: 15 °, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA:45° × 0.040in.

fpm, feet per min; RR, radial rake; Per. Cl, peripheral clearance; ECEA, end cutting edge angle; CA, cutting angle. (a) Nominal tool life to be expected for the recommended end milling under slotting conditions with highspeed steel and carbide cutters is 40 in./tooth. (b) Or radius as required. Courtesy of RMI Company (b) or radius as required

324 / Titanium: A Technical Guide

Table G.14

End milling: peripheral data(a)

Material

Brinell hardness No.

Depth of Speed, cut, in. fpm

High-speed steel tool Feed, in./tooth, Cutter diam, in. Tool 1 3 3 1–2 material 8 8 4

Grade 1, annealed

110–170 0.250 0.125 0.050 0.015

100 135 175 200

… … 0.0015 0.002

0.002 0.0035 0.005 0.006

0.005 0.006 0.007 0.008

0.007 0.008 0.009 0.010

M-2 M-2 M-2 M-2

Grade 2, grade 3, Ti-Pd, annealed

140–200 0.250 0.125 0.050 0.015

90 115 150 180

… … 0.0015 0.002

0.002 0.0035 0.005 0.006

0.005 0.006 0.007 0.008

0.007 0.008 0.009 0.010

M-2 M-2 M-2 M-2

Grade 4, annealed

200–275 0.250 0.125 0.050 0.015

60 70 85 100

… … 0.0008 0.001

0.001 0.0015 0.003 0.004

0.004 0.004 0.005 0.006

0.005 0.005 0.006 0.007

M-2 M-2 M-2 M-2

0.250 0.125 0.050 0.015

55 65 80 95

… … 0.0008 0.001

0.001 0.0015 0.003 0.004

0.004 0.004 0.005 0.006

0.005 0.005 0.006 0.007

M-2 M-2 M-2 M-2

6Al-4V, 6Al-4V-ELI, 8Mn, annealed

310–350 0.250 0.125 0.050 0.015

50 60 75 90

… … 0.0008 0.001

0.001 0.0015 0.003 0.004

0.004 0.004 0.005 0.006

0.005 0.005 0.006 0.007

M-2 M-2 M-2 M-2

7Al-4Mo, 8Al-1Mo-1V, 6Al-6V-2Sn, annealed

320–370 0.250 0.125 0.050 0.015

50 55 70 85

… … 0.0008 0.001

0.001 0.0015 0.003 0.004

0.004 0.004 0.005 0.006

0.005 0.005 0.006 0.007

M-2 M-2 M-2 M-2

1Al-8V-5Fe, annealed

320–380 0.250 0.125 0.050 0.015

40 50 65 80

… … 0.0008 0.001

0.001 0.0015 0.003 0.004

0.004 0.004 0.005 0.006

0.005 0.005 0.006 0.007

M-2 M-2 M-2 M-2

6Al-4V, Solution treated and aged

350–400 0.250 0.125 0.050 0.015

40 50 65 80

… … 0.001 0.0015

0.0008 0.0015 0.003 0.004

0.003 0.004 0.004 0.005

0.004 0.005 0.005 0.007

M-2 M-2 M-2 M-2

6Al-6V-2Sn, 7Al-4Mo, 4Al-3Mo-1V, Solution treated and aged

375–420 0.250 0.125 0.050 0.015

40 50 65 80

… … 0.0008 0.001

0.0008 0.0015 0.002 0.004

0.0015 0.003 0.004 0.005

0.003 0.004 0.005 0.007

M-2 M-2 M-2 M-2

1Al-8V-5Fe, Solution treated and aged

375–440 0.250 0.125 0.050 0.015

30 40 55 75

… … 0.0005 0.0007

0.0006 0.001 0.002 0.003

0.0015 0.003 0.003 0.004

0.003 0.004 0.005 0.006

M-2 M-2 M-2 M-2

5Al-2.5Sn, 300–340 5Al-2.5Sn-ELI, 6Al-2CNb-1Ta-1Mo, 4Al-3Mo-1V, annealed

Tool geometry

Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required Helix: 30°, RR: 10°, End Cl: 3°, Per. C: 7°, ECEA: 3°, CA: 45° × 0.60 in., or radius as required Helix: 30°, RR: 10°, End Cl: 3°, Per. C: 7°, ECEA: 3°, CA: 45° × 0.60 in., or radius as required Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required Helix 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required

Speed, fpm

Carbide tool Feed, in./tooth; Cutter diam, in. 1

8

3

8

3

4

1–2

Tool material

Tool geometry

250 335 375 400

… … 0.001 0.001

0.002 0.002 0.002 0.002

0.005 0.005 0.006 0.006

0.007 0.008 0.010 0.010

C-2 Helix: 15°, C-2 RR: 0°, C-2 End Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.40 in.

225 285 375 400

… … 0.001 0.001

0.002 0.002 0.002 0.002

0.005 0.005 0.006 0.006

0.007 0.008 0.010 0.010

C-2 Helix: 15°, C-2 RR: 0°, C-2 End: Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.040 in.

150 175 215 250

… … 0.0008 0.001

0.001 0.002 0.003 0.004

0.004 0.004 0.006 0.007

0.006 0.006 0.007 0.008

C-2 Helix: 15°, C-2 RR: 0°, C-2 End Cl: 12° C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.040 in.

135 160 200 240

… … 0.0008 0.001

0.001 0.002 0.003 0.004

0.004 0.004 0.006 0.007

0.006 0.006 0.007 0.008

C-2 Helix: 15°, C-2 RR: 0°, C-2 End Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA 45°× 0.40 in.

125 150 190 225

… … 0.0008 0.001

0.001 0.002 0.003 0.004

0.004 0.004 0.006 0.007

0.006 0.006 0.007 0.008

C-2 Helix: 15°, C-2 RR: 0°, C-2 End Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.40 in.

125 135 175 215

… … 0.0008 0.001

0.001 0.02 0.003 0.004

0.004 0.004 0.006 0.007

0.006 0.006 0.007 0.008

C-2 Helix: 15°, C-2 RR: 0°, C-2 End Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.040 in.

100 125 165 200

… … 0.0008 0.001

0.001 0.002 0.003 0.004

0.004 0.004 0.006 0.007

0.006 0.006 0.007 0.008

C-2 Helix: 15°, C-2 RR: 0°, C-2 End Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.040 in.

100 125 165 200

… … 0.001 0.0015

0.0008 0.0015 0.003 0.004

0.003 0.004 0.005 0.006

0.005 0.006 0.006 0.008

C-2 Helix: 15°, C-2 RR: 0°, C-2 End Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.040 in.

100 125 165 200

… … 0.0008 0.001

0.0008 0.0015 0.002 0.004

0.003 0.004 0.005 0.006

0.005 0.005 0.006 0.008

C-2 Helix: 15°, C-2 RR: 0°, C-2 End Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.40 in.

75 100 140 190

… … 0.0005 0.0007

0.0006 0.001 0.002 0.003

0.0015 0.003 0.004 0.005

0.003 0.005 0.006 0.007

C-2 C-2 C-2 C-2

Helix: 15°, RR: 0°, End Cl: 12°, Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.040 in.

(continued) fpm, feet per min; RR, radial rake; Per. Cl, peripheral clearance; ECEA, end cutting edge angle; CA, cutting angle. (a) Nominal tool life to be expected for the recommended end milling under peripheral conditions with high-speed steel and carbide cutters is 40 in./tooth. Courtesy of RMI Company

Machining Data / 325 Table G.14

(continued)

Material

Brinell hardness No.

Depth of Speed, cut, in. fpm

High-speed steel tool Feed, in./tooth, Cutter diam, in. Tool 1 3 3 1–2 material 8 8 4

13V-11Cr-3Al, Solution annealed

310–350 0.250 0.125 0.050 0.015

50 55 70 85

… … 0.0007 0.001

0.001 0.0015 0.003 0.004

0.004 0.004 0.005 0.006

0.005 0.005 0.006 0.007

M-2 M-2 M-2 M-2

13V-11Cr-3Al, Solution treated and aged

375–440 0.250 0.125 0.050 0.015

30 40 55 75

… … 0.0005 0.0007

0.0006 0.001 0.002 0.003

0.0015 0.003 0.003 0.004

0.003 0.004 0.005 0.006

M-2 M-2 M-2 M-2

Tool geometry

Helix, 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required Helix: 30°, RR: 10°, End Cl: 3°, Per. Cl: 7°, ECEA: 3°, CA: 45° × 0.060 in., or radius as required

Speed, fpm

Carbide tool Feed, in./tooth; Cutter diam, in. 1

8

3

8

3

4

1–2

Tool material

Tool geometry

125 140 175 215

… 0.001 … 0.0015 0.0007 0.003 0.001 0.004

0.004 0.005 0.006 0.007

0.006 0.006 0.007 0.008

C-2 Helix: 15°, C-2 RR: 0°, C-2 End Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.040 in.

75 100 140 190

… 0.0006 0.0015 … 0.001 0.003 0.0005 0.002 0.004 0.0007 0.003 0.005

0.003 0.005 0.005 0.007

C-2 Helix: 15 °, C-2 RR: 0°, C-2 End Cl: 12°, C-2 Per. Cl: 12°, ECEA: 3°, CA: 45° × 0.040 in.

fpm, feet per min; RR, radial rake; Per. Cl, peripheral clearance; ECEA, end cutting edge angle; CA, cutting angle. (a) Nominal tool life to be expected for the recommended end milling under peripheral conditions with high-speed steel and carbide cutters is 40 in./tooth. Courtesy of RMI Company

•

Metcut Research Associates, Inc., Cincinnati, OH, July 1973 N. Zlatin and M. Field, “Machinability Parameters on New Selective Aerospace Materials,” USAF Technical Report AFML-TR69-144, Metcut Research Associates, Inc., Cincinnati, OH, 1969

• N. Zlatin and M. Field, “Machinability Pa-

•

rameters on New and Selective Aerospace Matreials,” USAF Technical Report AFML-TR -71-95, Metcut Research Associates, Inc., Cincinnati, OH, 1971 N. Zlatin, M. Field, and W.P. Koster, “Final Report on Machinability of Materials,”

•

USAF Technical Report AFML-TR-65-444, Metcut Research Associates, Inc., Cincinnati, OH, 1966 N. Zlatin, M. Field, and W.P. Koster, “Machining of New Materials,” USAF Technical Report AFML-TR-67-339, Metcut Research Associates, Inc., Cincinnati, OH, 1967

Titanium: A Technical Guide Matthew J. Donachie, Jr., p327-330 DOI:10.1361/tatg2000p327

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Appendix H

Weights and Conversions THE INFORMATION contained in this Appendix assists the user on the most practical level—that of determining the overall weights of the various titanium grades in a variety of product forms. Additionally, various types of more general conversion tables are also provided. For ease of reference, the following list indicates the contents of each table:

• H.1: Commercially pure and alloyed tita• • • • • • •

nium weights H.2: Flat titanium bar weights H.3: Rounds, squares, bar, billet, wire weights H.4: Rectangular bar weights H.5: Sheet weights H.6: Plate weights H.7: Wire weights H.8: Ti-6Al-4V bar, coil, wire weights

Table H.1

• • • •

(See Table H.8 for Ti-6Al-4V.)

H.9: Pipe data, weights H.10: Tube and pipe weights H.11: Mils/in./mm conversions H.12: Mesh-sieve relations

• To determine the weight/inch of a flat bar,

A quick summary of conversion facts and formulas follows:

• The density of elemental titanium is nominally computed on the basis of 0.163 lb/in.3

• Apply the following factors to determine the

density of commercially pure Ti and various Ti alloys:

• • •

multiply width (in.) by thickness (in.) by 0.163. To determine the weight/foot of a round bar, multiply diameter (in.) squared by 1.536. Always consider the results of these formulas as approximations. Consult individual suppliers for more precise data. All of these computations and factors are based on English units.

Note that the data contained in the following tables must be considered close approximations, not precise constants. Consult your supplier in instances when precision is required, since manufacturing processes affect weights directly.

a. CP × 1.019 b. Ti-6Al-6V-2Sn × 1.025 c. Ti-6Mo-8V-2Fe-3Al × 1.094 d. Ti-13V-11Cr-3Al × 1.094

Commercially pure and titanium alloy weights

Gage

Weight, lb/ft2

0.008 0.010 0.012 0.016 0.020 0.025 0.030 0.032 0.035 0.040

0.188 0.235 0.282 0.376 0.469 0.587 0.704 0.751 0.822 0.939

Material

s s s s s s s s s

Gage

Weight, lb/ft2

0.045 0.050 0.056 0.060 0.063 0.071 0.075 0.080 0.085 0.090

1.056 1.174 1.314 1.408 1.479 1.667 1.760 1.878 1.995 2.112

Material

Note: Computations based on density of 0.163 lb/in.3. s, sheet; p, plate. Courtesy of Supra Alloys, Inc.

s s s s

s

Gage

Weight, lb/ft2

0.095 0.100 0.106 0.112 0.118 0.125 0.130 0.140 0.150 0.160

2.230 2.347 2.488 2.629 2.770 2.934 30.51 3.286 3.521 3.756

Material

s

Gage

Weight, lb/ft2

0.170 0.180 0.187 0.1875 0.250 0.375 0.500 0.625 0.750 1.000

3.990 4.225 4.389 4.401 5.868 8.802 11.736 14.670 17.604 23.472

Material

p

p p p

328 / Titanium: A Technical Guide Table H.2

Weight, lb/ft, at width (in.):

Thickness, in. 1 5 3 7 1 9

4 16 8 16 2 16

5

8 11 16 3 4 13 16 7 8 15 16

1 11 8 11 4 13 8 11 2 15 8 13 4 17 8 2

Titanium flat bar weights 1

5

2

0.244 0.305 0.366 0.427 0.488 0.549 0.611 0.672 0.733 0.794 0.855 0.916 0.978 1.100 1.222 1.345 1.467 1.589 1.712 1.834 1.956

8

0.305 0.382 0.458 0.534 0.611 0.687 0.763 0.839 0.916 0.993 1.070 1.146 1.222 1.375 1.528 1.681 1.834 1.986 2.139 2.292 2.445

3

4

0.366 0.458 0.549 0.641 0.733 0.824 0.916 1.008 1.100 1.192 1.284 1.375 1.467 1.650 1.834 2.017 2.200 2.385 2.567 2.751 2.934

7

8

0.427 0.534 0.641 0.748 0.855 0.962 1.070 1.177 1.284 1.391 1.497 1.604 1.712 1.925 2.139 2.353 2.567 2.780 2.994 3.209 3.423

1

11 4

11 2

13 4

2

21 4

21 2

23 4

3

31 4

31 2

33 4

4

0.488 0.611 0.733 0.855 0.978 1.100 1.222 1.344 1.467 1.589 1.712 1.834 1.956 2.200 2.445 2.690 2.934 3.178 3.423 3.668 3.912

0.611 0.763 0.916 1.070 1.222 1.375 1.528 1.681 1.834 1.986 2.139 2.293 2.445 2.750 3.056 3.361 3.668 3.973 4.278 4.586 4.890

0.733 0.916 1.100 1.284 1.467 1.650 1.834 2.017 2.200 2.385 2.567 2.751 2.934 3.301 3.668 4.035 4.401 4.768 5.135 5.502 5.868

0.855 1.070 1.284 1.497 1.712 1.925 2.139 2.353 2.567 2.780 2.994 3.209 3.423 3.852 4.278 4.707 5.135 5.562 5.990 6.419 6.846

0.978 1.222 1.467 1.712 1.956 2.200 2.445 2.690 2.934 3.178 3.423 3.668 3.912 4.401 4.890 5.380 5.868 6.356 6.846 7.336 7.824

1.100 1.375 1.650 1.925 2.200 2.476 2.751 3.026 3.301 3.576 3.852 4.126 4.401 4.957 5.501 6.051 6.602 7.151 7.701 8.252 8.802

1.222 1.528 1.834 2.139 2.445 2.751 3.056 3.361 3.668 3.973 4.278 4.585 4.890 5.501 6.112 6.725 7.335 7.948 8.558 9.170 9.780

1.344 1.681 2.017 2.353 2.690 3.027 3.361 3.699 4.035 4.370 4.707 5.043 5.380 6.051 6.725 7.397 8.069 8.741 9.413 10.086 10.758

1.467 1.834 2.200 2.567 2.934 3.301 3.668 4.035 4.401 4.768 5.135 5.502 5.868 6.602 7.335 8.069 8.802 9.536 10.270 11.004 11.730

1.589 1.986 2.385 2.780 3.178 3.576 3.973 4.370 4.768 5.165 5.562 5.959 6.356 7.151 7.946 8.740 9.536 10.330 11.124 11.920 12.712

1.712 2.139 2.567 2.994 3.423 3.852 4.278 4.707 5.135 5.562 5.990 6.419 6.846 7.701 8.558 9.413 10.270 11.124 11.981 12.838 13.692

1.833 2.292 2.751 3.209 3.668 4.125 4.584 5.043 5.501 5.958 6.417 6.877 7.335 8.253 9.168 10.087 11.003 11.918 12.836 13.755 14.670

1.956 2.444 2.934 3.424 3.912 4.400 4.890 5.380 5.868 6.356 6.846 7.336 7.824 8.802 9.780 10.760 11.736 12.712 13.692 14.672 15.648

Courtesy of Supra Alloys, Inc.

Table H.3 Size, in. 1 1 3 1 5 3 7 1 9

16 8 16 4 16 8 16 2 16

5

8 11 16 3 4 13 16 7 8 15 16

1 11 16 11 8 13 16 11 4 115 16 13 8 17 16 11 2 19 16 15 8 111 16

Titanium rounds, squares, bar, billet, and wire weights

Rounds, lb/ft

0.006 0.024 0.054 0.096 0.150 0.216 0.294 0.384 0.487 0.600 0.726 0.864 1.015 1.177 1.351 1.536 1.734 1.944 2.166 2.400 2.645 2.904 3.175 3.456 3.750 4.056 4.374

Table H.5

Squares, lb/ft

Size, in.

Rounds, lb/ft

Squares, lb/ft

Size, in.

Rounds, lb/ft

Squares, lb/ft

Size, in.

Rounds, lb/ft

Squares, lb/ft

0.008 0.031 0.069 0.123 0.192 0.276 0.375 0.489 0.619 0.764 0.924 1.100 1.291 1.497 1.719 1.956 2.207 2.476 2.759 3.056 3.369 3.699 4.042 4.401 4.775 5.165 5.570

13 4 113 16 17 8 115 16 2 21 16 21 8 23 16 21 4 25 16 23 8 27 16 21 2 29 16 25 8 211 16 23 4 213 16 27 8 215 16 3 31 8 31 4 33 8 31 2 35 8 33 4

4.705 5.047 5.400 5.766 6.144 6.534 6.937 7.350 7.777 8.215 8.665 9.128 9.601 10.087 10.585 11.096 11.618 12.152 12.698 13.255 13.826 15.00 16.226 17.50 18.82 20.19 21.60

5.990 6.425 6.876 7.342 7.824 8.320 8.832 9.359 9.902 10.460 11.034 11.621 12.225 12.844 13.478 14.127 14.792 15.47 16.17 16.88 17.60 19.10 20.66 22.28 23.96 25.70 27.51

37 8 4 41 8 41 4 43 8 41 2 45 8 43 4 47 8 5 51 8 51 4 53 8 51 2 55 8 53 4 57 8 6 61 8 61 4 63 8 61 2 65 8 63 4 67 8 7 71 4

23.07 24.58 26.14 27.75 29.40 31.11 32.86 34.66 36.51 38.41 40.35 42.34 44.38 46.47 48.61 50.79 53.03 55.30 57.63 60.01 62.43 64.91 67.43 70.00 72.61 75.28 80.75

29.37 31.30 33.28 35.33 37.44 39.61 41.84 44.13 46.49 48.90 51.38 53.91 56.51 59.17 61.89 64.67 67.51 70.42 73.38 76.41 79.49 82.64 85.85 89.12 92.45 95.84 102.81

71 2 73 4 8 81 2 9 91 2 10 101 2 11 111 2 12 121 2 13 14 15 16 17 18 19 20 21 22 23 24

86.41 92.27 98.32 111.0 124.4 138.6 153.6 169.4 186.0 203.0 221.0 240.0 260.0 301.0 347.0 393.0 444.0 498.0 555.0 614.0 677.0 744.0 813.0 885.0

110.03 117.48 125.18 141.3 158.4 176.5 195.6 215.6 237.0 259.0 282.0 306.0 331.0 383.0 440.0 500.0 565.0 634.0 … … … … … …

Table H.4 weights

Titanium rectangular bar

Width, in.

3

Weight, lb/linear ft, at gage (in.)

1 11 4 11 2 13 4 2

16

0.367 0.458 0.550 0.640 0.732

1

4

0.489 0.611 0.733 0.856 0.978

3

1

8

0.733 0.917 1.10 1.28 1.47

Courtesy of Industrial Titanium Corp.

Table H.7

Titanium sheet weights

Titanium wire weights Weight

Thickness (gage), in.

0.012 0.016 0.020 0.025 0.032 0.040 0.050 0.063

Approx. weight, lb/ft2

0.282 0.376 0.469 0.587 0.751 0.939 1.174 1.477

Weight, lb/36 × 96 in. sheet

6.760 9.013 11.267 14.083 18.026 22.533 28.166 35.490

Thickness (gage), in.

0.070 0.075 0.080 0.090 0.093 0.110 0.125

Weight, Approx. lb/36 × weight, 96 in. lb/ft2 sheet

1.643 1.760 1.878 2.112 2.143 2.582 2.934

39.432 42.250 45.066 50.700 52.390 61.967 70.416

Size, in.

Table H.6 Thickness, 3 1

16 (0.187)

(0.250) 3 (0.375) 8 1 (0.500) 2 4

1

Titanium plate weights Approximate weight,

4.401 5.868 8.802 11.736

Courtesy of Industrial Titanium Corp.

Thickness, 5 3

8 (0.625)

(0.750) 1 (1.000) 4

Approximate weight,

14.674 17.582 23.443

32 (0.032) 0.050 1 (0.063) 16 3 (0.093) 32 1 (0.125) 8 5 (0.156) 32 3 (0.187) 16 1 (0.250) 4 5 (0.312) 16

ft/lb

lb/100 ft

635 260 169 75 42 27 19 10.5 6.7

0.15748 0.38462 0.60976 1.31579 2.40053 3.73860 5.26316 9.60150 15.00234

Courtesy of Industrial Titanium Corp.

2

0.978 1.22 1.47 1.71 1.96

Weights and Conversions / 329 Table

H.8 Ti-6Al-4V bar, coil, and wire weights

Diam, in.

lb/100 ft

ft/lb

Diam, in.

0.010 0.012 0.014 0.016 0.018 0.020 0.022 0.024 0.026 0.028 0.030 0.032 0.034 0.036 0.038 0.040 0.042 0.044 0.046 0.048 0.050 0.052

0.015 0.022 0.030 0.039 0.049 0.060 0.073 0.087 0.102 0.118 0.136 0.154 0.174 0.195 0.218 0.241 0.266 0.292 0.319 0.347 0.377 0.408

6630 4605 3380 2590 2045 1655 1370 1150 980 845 735 645 570 510 455 414 375 342 313 287 265 245

0.054 0.056 0.058 0.060 0.062 0.064 0.068 0.070 0.072 0.074 0.076 0.078 0.080 0.082 0.084 0.086 0.088 0.090 0.092 0.094 0.096 0.098

Size, in.

Rounds, lb/ft

Square, lb/ft

Size, in.

0.3125 0.375 0.4375 0.50 0.5625 0.625 0.6875 0.750 0.8125 0.875 0.9375 1.0 1.0625

0.147 0.212 0.289 0.377 0.477 0.589 0.713 0.848 0.995 1.15 1.33 1.51 1.70

0.188 0.270 0.368 0.480 0.608 0.750 0.908 1.08 1.27 1.47 1.69 1.92 2.17

lb/100 ft

0.440 0.473 0.507 0.543 0.580 0.618 0.697 0.739 0.782 0.826 0.871 0.917 0.965 1.014 1.064 1.115 1.168 1.221 1.276 1.332 1.390 1.448 Rounds, lb/ft

1.125 1.1875 1.25 1.3125 1.375 1.4375 1.50 1.5675 1.625 1.6875 1.75 1.8125 1.875

1.91 2.13 2.36 2.60 2.85 3.12 3.39 3.68 3.98 4.29 4.62 4.95 5.30

ft/lb

Diam, in.

0.100 0.105 0.110 0.115 0.120 0.125 0.130 0.135 0.140 0.145 0.150 0.155 0.160 0.165 0.170 0.175 0.180 0.185 0.190 0.195 0.200 0.205

227 211 197 184 172 161 143 135 127 121 114 108 103 98 93 89 85 81 78 75 71 69

lb/100 ft

1.508 1.663 1.825 1.994 2.172 2.356 2.549 2.748 2.956 3.170 3.393 3.623 3.860 4.105 4.358 4.618 4.886 5.161 5.444 5.734 6.032 6.337

Square, lb/ft

Size, in.

Rounds, lb/ft

2.43 2.71 3.00 3.31 3.63 3.97 4.32 4.69 5.07 5.47 5.88 6.31 6.75

1.9375 2.0 2.0625 2.125 2.1875 2.25 2.3125 2.375 2.4375 2.50 2.5625 2.625 2.6875

5.66 6.03 6.41 6.81 7.22 7.63 8.06 8.51 8.96 9.43 9.90 10.39 10.89

ft/lb

Diam, in.

lb/100 ft

66 60 54 50 46 42 39 36 33 31 29 27 25 24 22 21 20 19 18 17 16 15

0.210 0.215 0.220 0.225 0.230 0.235 0.240 0.245 0.250 0.255 0.260 0.265 0.270 0.275 0.280 0.285 0.290 0.295 0.300 0.305 0.310 0.315

6.650 6.971 7.299 7.634 7.977 8.328 8.686 9.052 9.423 9.806 10.194 10.590 10.993 11.404 11.822 12.248 12.682 13.123 13.572 14.028 14.492 14.963

Square, lb/ft

7.21 7.68 8.17 8.67 9.19 9.72 10.27 10.83 11.41 12.00 12.61 13.23 13.87

Size, in.

2.75 2.8125 2.875 2.9375 3.0 3.0625 3.125 3.1875 3.25 3.3125 3.375 3.4375 3.50

Rounds, lb/ft

11.40 11.93 12.46 13.01 13.57 14.14 14.73 15.32 15.93 16.55 17.18 17.82 18.47

ft/lb

15 14 13 13 12 12 11 11 10 10 9 9 9 8 8 8 7 7 7 7 7 6 Square, lb/ft

14.52 15.19 15.87 16.57 17.28 18.01 18.75 19.51 20.28 21.07 21.87 22.69 23.52

Weights are based on a density of 0.160 lb/in.3. Apply the following factors for other grades: Ti-6Al-6V-2Sn × 1.025; commercially pure × 1.019; Ti-13V-11Cr-3Al × 1.094; Ti-8Mo-8V-2Fe-3Al 1.094. Courtesy of Dynamet, Inc.

Table H.9

Titanium pipe weights Schedule 10, light weight

Pipe size, in. 1 1 3 1 3

8 4 8 2 4

1 1 14 1 12 2 2 12 3 3 12 4

Schedule 40, standard weight

Schedule 80, extra heavy weight

Outside diam, in.

Wall, in.

wt/ft (lb)

Wall, in.

wt/ft (lb)

Wall, in.

wt/ft (lb)

0.405 0.540 0.675 0.840 1.050 1.315 1.660 1.900 2.375 2.875 3.500 4.000 4.500

0.049 0.065 0.065 0.083 0.083 0.109 0.109 0.109 0.109 0.120 0.120 0.120 0.120

0.107 0.182 0.244 0.386 0.493 0.807 1.038 1.199 1.517 2.030 2.491 2.849 3.227

0.068 0.088 0.091 0.109 0.113 0.133 0.140 0.145 0.154 0.203 0.216 0.226 0.237

1.141 0.244 0.326 0.489 0.650 0.965 1.307 1.563 2.100 3.331 4.356 5.238 6.204

0.095 0.119 0.126 0.147 0.154 0.179 0.191 0.200 0.218 0.276 0.300 0.318 0.337

0.181 0.308 0.425 0.626 0.848 1.249 1.723 2.088 2.888 4.405 5.894 7.188 8.614

Courtesy of Industrial Titanium Corp.

330 / Titanium: A Technical Guide Table H.10

Titanium tube and pipe weights

Wall, in.

0.020 0.025 0.028 0.032 0.035 0.042 0.049 0.058 0.065 0.072 0.083 0.095 0.109 0.120

Weight, lb/linear ft, at outside diameter, in. 1

8

0.013 0.015 0.016 0.018 0.019 0.021

3

16

0.020 0.025 0.027 0.030 0.032 0.037 0.041

1

5

4

0.028 0.034 0.038 0.042 0.046 0.053 0.060 0.068 0.073

16

0.035 0.044 0.048 0.055 0.060 0.069 0.079 0.090 0.098 0.106

3

8

0.043 0.053 0.059 0.067 0.073 0.086 0.098 0.113 0.123 0.134 0.148 0.163

7

1

16

0.051 0.063 0.069 0.079 0.086 0.101 0.116 0.134 0.147 0.160 0.179 0.198 0.220

2

0.058 0.072 0.080 0.091 0.100 0.118 0.135 0.157 0.173 0.189 0.212 0.236 0.261 0.280

9

16

0.066 0.081 0.091 0.103 0.113 0.133 0.153 0.178 0.196 0.215 0.242 0.270 0.301 0.327

5

8

0.073 0.091 0.101 0.115 0.126 0.151 0.173 0.202 0.223 0.244 0.276 0.309 0.345 0.372

3

4

0.089 0.110 0.123 0.140 0.154 0.182 0.211 0.246 0.273 0.300 0.340 0.382 0.429 0.464

7

8

0.104 0.129 0.144 0.164 0.180 0.215 0.248 0.291 0.323 0.355 0.404 0.455 0.513 0.556

1

11 4

13 8

11 2

158

13 4

17 8

2

21 4

23 8

21 2

23 4

3

0.119 0.148 0.165 0.188 0.205 0.244 0.286 0.336 0.373 0.411 0.468 0.528 0.586 0.649

0.151 0.186 0.208 0.237 0.259 0.309 0.361 0.424 0.473 0.521 0.595 0.674 0.764 0.833

0.207 0.229 0.261 0.287 0.340 0.395 0.465 0.520 0.571 0.651 0.741 0.836 0.916

0.226 0.253 0.285 0.312 0.373 0.436 0.513 0.573 0.631 0.722 0.820 0.932 1.01

0.274 0.313 0.341 0.405 0.469 0.558 0.622 0.686 0.786 0.892 1.01 1.10

0.337 0.368 0.437 0.512 0.603 0.673 0.742 0.850 0.966 1.09 1.20

0.395 0.472 0.549 0.647 0.722 0.797 0.913 1.03 1.18 1.29

0.505 0.587 0.686 0.773 0.853 0.977 1.11 1.26 1.38

0.662 0.780 0.872 0.963 1.10 1.25 1.43 1.57

0.825 0.922 1.01 1.16 1.33 1.51 1.66

0.870 0.972 1.07 1.23 1.40 1.60 1.75

0.959 1.07 1.18 1.35 1.54 1.76 1.93

1.04 1.17 1.29 1.48 1.69 1.93 2.12

Courtesy of Industrial Titanium Corp.

Table H.11

mils/in./mm conversions

mils

in.

mm

0.01 0.05 0.1 0.5 1 2 3 4 5 6 7 8 9 10 15 20 25 30 35 40 45 50 60 70 80 90 100 125 150 200 250 300 400 500 750 1000

0.00001 0.00005 0.0001 0.0005 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050 0.060 0.070 0.080 0.090 0.100 0.125 0.150 0.20 0.25 0.30 0.40 0.50 0.75 1.0 2 3 4 5 6 7 8 9 10 11 12

0.000254 0.00127 0.00254 0.0127 0.0254 0.0508 0.0762 0.1016 0.1270 0.1524 0.1778 0.2032 0.2286 0.2540 0.3810 0.5080 0.6350 0.7620 0.8890 1.016 1.143 1.270 1.524 1.778 2.032 2.286 2.540 3.175 3.810 5.080 6.350 7.620 10.160 12.700 19.050 25.40 50.80 76.20 101.60 127.00 152.40 177.80 203.20 228.60 254.00 279.40 304.80

Table H.12 Mesh-sieve designation

1 3 5 1 3 5 1

4 8 2 8 16 4

31 2 4 5 6 7 8 10 12 14 16 18 Mesh-sieve designation

20 25 30 35 40 45 50 60 70 80 100 120 140 170 200 230 270 325 400

Mesh-sieve relations Sieve opening in.

mm

1.00 0.750 0.625 0.500 0.375 0.312 0.250 0.223 0.187 0.157 0.132 0.111 0.0937 0.0787 0.0661 0.0555 0.0469 0.0394

25.4 19.0 16.0 12.7 9.51 8.00 6.35 5.66 4.76 4.00 3.36 2.83 2.38 2.00 1.68 1.41 1.19 1.00 Sieve opening

in.

microns

0.0331 0.0278 0.0234 0.0197 0.0165 0.0139 0.0117 0.0098 0.0083 0.0070 0.0059 0.0049 0.0041 0.0035 0.0029 0.0025 0.0021 0.0017 0.0015

841 707 595 500 420 354 297 250 210 177 149 125 105 88 74 63 53 44 37

A– mesh designation denotes all particles are smaller than the indicated opening. A+ mesh designation denotes all particles are larger than the indicated opening. Example: –3 8 + 10 mesh, particle sizes range from 2.00–9.51 mm.

Titanium: A Technical Guide Matthew J. Donachie, Jr., p333-343 DOI:10.1361/tatg2000p333

Copyright © 2000 ASM International® All rights reserved. www.asminternational.org

Appendix J

Glossary THIS GLOSSARY is composed of a selection of technical words relevant to a discussion of titanium and titanium alloys. It is included to aid the reader who may not be familiar with all aspects of titanium, its production, or its uses. This glossary is not all inclusive. Refer also to the various volumes of the ASM Handbook, which frequently contain extensive glossaries covering the entire field of metal production and use, or to the ASM Materials Engineering Dictionary. Note: Italicized words within a definition can be found under separate listings in the Glossary.

A AC. Air cooled. acicular alpha. A product of nucleation and growth from beta to the lower-temperature allotrope, alpha phase. It may have a needlelike appearance in a photomicrograph and may have needle, lenticular, or flattened bar morphology in three dimensions. Its typical aspect ratio is about 10:1. activation. The changing of a passive surface of a metal to a chemically active state. Contrast with passivation. age hardening. Hardening by aging, usually after rapid cooling or cold working. See also aging. aging. A change in the properties of certain metals and alloys that occurs with time at ambient or moderately elevated temperatures after working or a heat treatment (natural or artificial aging) or after a cold-working operation (strain aging). The change in properties is often, but not always, due to a phase change (precipitation), but it never involves a change in chemical composition of the metal or alloy. See also overaging. allotropy. The property by which certain elements may exist in more than one crystal structure. An allotrope is a specific crystal structure of the metal. alloy. A substance having metallic properties and being composed of two or more chemical elements of which at least one is a metal.

alloying element. An element, added to and remaining in a metal, that changes structure and properties. alloy powder, alloyed powder. A metal powder consisting of at least two constituents that are partially or completely alloyed with each other. alloy system. A complete series of compositions produced by mixing in all proportions any group of two or more components, at least one of which is a metal. alpha. The low-temperature allotrope of titanium with a hexagonal, close-packed crystal structure. (It occurs below the beta transus.) alpha-beta structure. A microstructure containing α and β as the principal phases at a specific temperature. See also beta. alpha case. The oxygen-, nitrogen-, or carbonenriched, α-stabilized surface resulting from elevated temperature exposure. See also a1pha stabilizer. alpha double prime (orthorhombic martensite). A supersaturated, nonequilibrium orthorhombic phase formed by a diffusionless transformation of the β phase in certain alloys. alpha prime (hexagonal martensite). A supersaturated, nonequilibrium hexagonal α phase formed by a diffusionless transformation of the β phase. It is often difficult to distinguish from acicular α, although the latter is usually less well defined and frequently has curved, instead of straight, sides. alpha stabilizer. An alloying element that dissolves preferentially in the alpha phase and raises the alpha-beta transformation temperature. alpha transus. The temperature that designates the phase boundary between the α and α + β fields. alpha 2 structure. An ordered structure of titanium-aluminum compound with a stoichiometry of Ti3Al. annealed powder. A powder that is heat treated to render it soft and compactible. annealing. A generic term denoting a treatment, consisting of heating to, and holding at, a suitable temperature followed by cool-

ing at a suitable rate. It is used primarily to soften metallic materials but also to simultaneously produce desired changes in other properties or in microstructure. The purpose of such changes may be, but is not confined to: improvement of machinability, facilitation of cold work, improvement of mechanical or electrical properties, and/or increase in stability of dimensions. When the term is used without qualification, full annealing is implied. When applied only for the relief of stress, the process is properly called stress relieving or stress-relief annealing. In nonferrous alloys, annealing cycles are designed to: (1) remove part or all of the effects of cold working (recrystallization may or may not be involved); (2) cause substantially complete coalescence of precipitates from solid solution in relatively coarse form; or (3) both, depending on composition and material condition. Specific process names in commercial use are final annealing, full annealing, intermediate annealing, partial annealing, recrystallization annealing, stressrelief annealing, and anneal to temper. See also multiple annealing. atm. Atmosphere (pressure). atomic number. The number of protons in an atomic nucleus; determines the individuality of the atom as a chemical element. atomic percent. The number of atoms of an element in a total of 100 representative atoms of a substance. atomization. The disintegration of a molten metal into particles by a rapidly moving gas or liquid stream or by other means. AWG. American wire gage. AWS. American Welding Society.

B B. Bar. bake. (verb). To remove gases from a powder at low temperatures. banded structure. A segregated structure consisting of alternating, nearly parallel bands of

334 / Titanium: A Technical Guide different composition, typically aligned in the direction of primary hot working. B&S. Brown and Sharpe (gage). bar. A metal product of uniform section produced in short to moderate lengths by rolling, extrusion, or other processes such as swaging or powder metallurgy. Section shapes generally are symmetrical and circular, rectangular, or hexagonal in form, but other shapes are produced. Bars are relatively smaller in cross-sectional dimensions than billets but are substantially larger than wire. Bar may be used for forging stock, wire drawing stock, or for the production of items by machining. barstock. Same as bar. basal plane. A plane perpendicular to the principal axis (c axis) in a tetragonal or hexagonal structure. basketweave. Alpha platelets with or without interleaved β platelets that occur in colonies in a Widmanstätten structure. batch. The total output of one mixing of powder metal; sometimes called a lot. batch sintering. Presintering or sintering in such a manner that compacts are sintered and removed from the furnace before additional unsintered compacts are placed in the furnace. Bauschinger effect. For both single-crystal and polycrystalline metals, any change in stress-strain characteristics that can be ascribed to changes in the microscopic stress distribution within the metal, as distinguished from changes caused by strain hardening. In the narrow sense, the process whereby plastic deformation in one direction causes a reduction in yield strength when stress is applied in the opposite direction. beta (β). The high-temperature allotrope of titanium with a body-centered cubic crystal structure that occurs above the β transus. beta eutectoid stabilizer. An alloying element that dissolves preferentially in the β phase, lowers the α-β to β transformation temperature, and results in β decomposition to α plus a compound. beta fleck. Alpha-lean region in the α-β microstructure significantly larger than the primary α width. This β-rich area has a β transus measurably below that of the matrix. Beta flecks have reduced amounts of primary α, which may exhibit a morphology different from the primary α in the surrounding α-β matrix. beta isomorphous stabilizer. An alloying element that dissolves preferentially in the β phase, lowers the α-β to β transformation temperature without a eutectoid reaction, and forms a continuous series of solid solutions with, β-titanium. beta-STOA. Beta solution overaging. See also solution heat treatment and overaging. beta transus. The minimum temperature above which equilibrium α does not exist. For β eutectoid additions, the β transus ordinarily is applied to hypoeutectoid compositions or

those that lie to the left of the eutectoid composition. billet. (1) A solid, semifinished round or square product that has been hot worked by forging, rolling, or extrusion; usually smaller than a bloom. (2) A general term for wrought starting stock used in making forgings or extrusions. binder. A substance added to the powder to: (a) increase the strength of the compact; and (b) cement together powder particles that alone would not sinter into a strong object. blank. A pressed, presintered, or fully sintered compact, usually in the unfinished condition, to be machined or otherwise processed to final shape or condition. body-centered cubic lattice structure. A unit cell that consists of atoms arranged at cube corners with one atom at the center of the cube. braze. A joint produced by heating an assembly to suitable temperatures and by using a filler metal having a liquidus above 450 °C (840 °F) and below the solidus of the base metal. The filler metal is distributed between the closely fitted faying surfaces of the joint by capillary action. brazeability. The capacity of a metal to be brazed, under the fabrication conditions imposed, into a specific suitably designed structure and to perform satisfactorily in the intended service. braze welding. A method of welding by using a filler metal having a liquidus above 450 °C (840 °F) and below the solidus of the base metals. Unlike brazing, in braze welding the filler metal is not distributed in the joint by capillary attraction. brazing. A group of processes that join solid materials together by heating them to a suitable temperature and by using a filler metal having a liquidus above approximately 450 °C (840 °F) and below the solidus of the base materials. The filler metal is distributed between the closely fitted surfaces of the joint by capillary attraction. brazing filler metal. A nonferrous filler metal used in brazing and braze welding. Brinell hardness number (HB). A number related to the applied load and to the surface area of the permanent impression made by a ball indenter. Brinell hardness test. A test for determining the hardness of a material by forcing a hard steel or carbide ball of specified diameter into it under a specific load. The result is expressed as the Brinell hardness number, which is the value obtained by dividing the applied load in kilograms by the surface area of the resulting impression in square millimeters. brittle. Permitting little or no plastic (permanent) deformation prior to fracture. brittle fracture. Separation of a solid accompanied by little or no macroscopic plastic deformation. Typically, brittle fracture occurs by rapid crack propagation with less expenditure of energy than for ductile fracture.

brittleness. The tendency of a material to fracture without first undergoing significant plastic deformation. Contrast with ductility.

C cake. A coalesced mass of unpressed metal powder. CAP. See consolidation by atmospheric pressure. carbonitriding. A case hardening process in which a suitable ferrous material is heated above the lower transformation temperature in a gaseous atmosphere of such composition as to cause simultaneous absorption of carbon and nitrogen by the surface and, by diffusion, create a concentration gradient. The heat-treating process is completed by cooling at a rate that produces the desired properties in the workpiece. carburizing. Absorption and diffusion of carbon into solid ferrous alloys by heating, to a temperature usually above Ac3, in contact with a suitable carbonaceous material. A form of case hardening that produces a carbon gradient extending inward from the surface, enabling the surface layer to be hardened either by quenching directly from the carburizing temperature or by cooling to room temperature, then reaustenitizing and quenching. case hardening. A generic term covering several processes applicable to steel that change the chemical composition of the surface layer by absorption of carbon, nitrogen, or a mixture of the two, and by diffusion, create a concentration gradient. The processes commonly used are carburizing and quench hardening, cyaniding, nitriding, and carbonitriding. The use of the applicable specific process name is preferred. cast or casting. To fabricate an item by pouring molten metal into a shaped cavity and permitting the metal to solidify. A cast can relate to the item or may be a synonym for heat, that is an identifiable chemistry lot. CAW-G. See gas carbon arc welding. Charpy test. An impact test in which a V-notched, keyhole-notched, or U-notched specimen, supported at both ends, is struck behind the notch by a striker mounted at the lower end of a bar that can swing as a pendulum. The energy that is absorbed in fracture is calculated at the height to which the striker would have risen had there been no specimen and the height to which it actually rises after fracture of the specimen. chemical vapor deposition (CVD). The precipitation of a metal from a gaseous compound onto a solid or particulate substrate. CHIP. CIP plus sinter plus HIP. A 3-stage P/M process. See also CIP. CHM. Chemical milling, a machining technique. CIP. See cold isostatic pressing.

Glossary / 335 close-packed. A geometric arrangement in which a collection of equally sized spheres (atoms) may be packed together in a minimum total volume. coarse grains. Grains larger than normal for the particular wrought metal or alloy or of a size that produces a surface roughening known as orange peel or alligator skin in wrought alloys. cold isostatic pressing. Forming technique in which high fluid pressure is applied to a powder (metal or ceramic) part at ambient temperature. Water or oil is used as the pressure medium. cold pressing. The forming of a compact from powder at, or below, room temperature. cold-worked structure. A microstructure resulting from plastic deformation of a metal or alloy below its recrystallization temperature. cold working. Deforming metal plastically under conditions of temperature and strain rate that induce strain hardening. Usually, but not necessarily, conducted at room temperature. Contrast with hot working. colonies. Regions within prior beta grains with alpha platelets having nearly identical orientations. In commercially pure titanium, colonies often have serrated boundaries. Colonies arise as transformation products during cooling from the beta fields at cooling rates that induce platelet nucleation and growth. compact. An object produced by the compression of metal powder, generally while confined in a die, with or without the inclusion of nonmetallic constituents. compact, compacting, compaction. The operation or process of producing a compact; sometimes called pressing. consolidation by atmospheric pressure (CAP). A P/M consolidation process wherin the applied pressure comes from the atmosphere. consumable electrode. A general term for any arc welding electrode made chiefly of filler metal. consumable electrode remelting. A process for refining metals in which an electric current passes between an electrode made of the metal to be refined. corrosion. The deterioration of a metal by a chemical or electrochemical reaction with its environment. corrosion embrittlement. The severe loss of ductility of a metal resulting from corrosive attack, usually intergranular and often not visually apparent. corrosion fatigue. Cracking produced by the combined action of repeated or fluctuating stress and a corrosive environment at lower stress levels or fewer cycles than would be required in the absence of a corrosive environment. corrosive wear. Wear in which chemical or electrochemical reaction with the environment is significant. cph. Close-packed hexagonal. See hexagonal close-packed lattice structure.

creep. Time-dependent strain occurring under stress usually at elevated temperatures. The creep strain occurring at a diminishing rate is called primary, or transient, creep; that occurring at a minimum and almost constant rate, secondary, or steady-rate creep; that occurring at an accelerating rate, tertiary creep. These rates are frequently represented graphically as 1, 2, and 3, or as I, II, and III. creep limit. (1) The maximum stress that will cause less than a specified quantity of creep in a given time. (2) The maximum nominal stress under which the creep strain rate decreases continuously with time under constant load and at constant temperature. Sometimes used synonymously with creep strength. creep rate. The slope of the creep-time curve at a given time determined from a Cartesian plot. creep recovery. Time-dependent strain after release of load in a creep test. creep rupture strength. The stress that will cause fracture in a creep test at a given time in a specified constant environment. Also known as stress-rupture strength. creep rupture test. Same as stress-rupture test. creep strain. The time-dependent total strain (extension plus initial gage length) produced by applied stress during a creep test. creep strength. The stress that will cause a given creep strain in a creep test at a given time in a specified constant environment. creep stress. The constant load divided by the original cross-sectional area of the specimen. crevice corrosion. A type of concentration cell corrosion; corrosion caused by the concentration or depletion of dissolved salts, metal ions, oxygen, or other gases, and such, in crevices or pockets remote from the principal fluid stream, with a resultant building up of differential cells that ultimately cause deep pitting. Localized corrosion of a metal surface at, or immediately adjacent to, an area that is shielded from full exposure to the environment because of close proximity between the metal and the surface of another material. critical stress intensity factor (KIc). A measure of fracture toughness. Increased KIc indicates greater resistance to fracture. KIc is a common means, but not the only one, of describing quantitatively the fracture resistance of an alloy. Stress intensity factors vary with loading conditions. The I refers to the loading condition (i.e. plane strain). The c refers to critical condition, above which the stress (load) need no longer be increased to cause fracture. KIc varies with material chemistry and processing history. It is a function of temperature and generally decreases as temperature decreases. crystal. A solid composed of atoms, ions, or molecules arranged in a pattern that is periodic in three dimensions. crystallization. (1) The separation, usually from a liquid phase on cooling, of a solid crystalline phase.(2) Sometimes erroneously

used to explain fracturing that actually has occurred by fatigue. curing. The processing of a mold to obtain desired characteristics. CVD. See chemical vapor deposition. cyaniding. A case hardening process in which a ferrous material is heated above the lower transformation temperature range in a molten salt containing cyanide to cause simultaneous absorption of carbon and nitrogen at the surface and, by diffusion, create a concentration gradient. Quench hardening completes the process.

D DA. See duplex annealing. da/dN. See fatigue crack growth rate. DBTT. Ductile-to-brittle transition temperature. deformation. A change in the form of a body due to stress, thermal change, change in moisture, or other causes. Measured in units of length. descaling. Removing the thick layer of oxides formed on some metals at elevated temperatures. DFB. See diffusion brazing. DFW. See diffusion welding. diam. Diameter. diffusion brazing (DFB). A brazing process that joins two or more components by heating them to suitable temperatures and by using a filler metal or an in situ liquid phase. The filler metal may be distributed by capillary attraction or may be placed or formed at the faying surfaces. The filler metal is diffused with the base metal to the extent that the joint properties have been changed to approach those of the base metal. Pressure may or may not be applied. diffusion welding (DFW). A high-temperature, solid-state welding process that permanently joins faying surfaces by the simultaneous application of pressure and heat. The process does not involve macroscopic deformation, melting, nor relative motion of parts. A solid filler metal (diffusion aid) may or may not be inserted between the faying surfaces. double aging. Employment of two different aging treatments to control the type of precipitate formed from a supersaturated matrix in order to obtain the desired properties. The first aging treatment, sometimes referred to as intermediate or stabilizing, is usually carried out at higher temperature than the second. ductile fracture. Fracture characterized by tearing of metal accompanied by appreciable gross plastic deformation and expenditure of considerable energy. ductility. The ability of a material to deform plastically before fracturing. Measured by elongation or reduction of area in a tension test, by height of cupping in a cupping test, or by the radius or angle of bend in a bend

336 / Titanium: A Technical Guide test. Contrast with brittleness; see also plastic deformation. duplex annealing (DA). See multiple annealing. duplexing. Any two-furnace melting or refining process. Also called duplex melting or duplex processing.

E EBC. See electron beam cutting. EBW. See electron beam welding. ECM. Electrochemical machining. electrode. (1) The isolated sponge, master alloy, and/or revert used in consumable vacuum arc melting. (2) The solidified ingot in cases when it is to be remelted again in double and triple melting operations. electron beam cutting (EBC). A cutting process that uses the heat obtained from a concentrated beam composed primarily of high-velocity electrons that impinge upon the workpieces to be cut; it may or may not use an externally supplied gas. electron beam welding (EBW). A welding process that produces coalescence of metals with the heat obtained from a concentrated beam composed primarily of high-velocity electrons impinging upon the surfaces to be joined. ELI. Extra-low interstitial. elongated alpha. A fibrous type of structure brought about by unidirectional metalworking. It may be enhanced by the prior presence of blocky and/or grain boundary alpha. elongated grain. A grain with one principal axis significantly longer than either of the other two. elongation. A term used in mechanical testing to describe the amount of extension of a test piece when stressed. In tensile testing, the increase in the gage length, measured after fracture of the specimen within the gage length, usually expressed as a percentage of the original gage length. embrittlement. The severe loss of ductility and/or toughness of a material, usually a metal or alloy. endurance limit. The maximum stress below which a material can presumably endure an infinite number of stress cycles. If the stress is not completely reversed, the value of the mean stress, the minimum stress, or the stress ratio also should be stated. Compare with fatigue limit. epitaxial. Having orientation controlled by the crystal substrate; use of crystals and of the relation between them and their substrate. epitaxy. Growth of an electrodeposit or vapor deposit in which the orientation of the crystals in the deposit are directly related to crystal orientations in the underlying crystalline substrate. equiaxed structure. A polygonal or spheroid microstructural feature having approximately equal dimensions in all directions. In alpha-beta titanium alloys, such a term com-

monly refers to a microstructure in which most of the minority phase appears spheroidal. equilibrium. A dynamic condition of physical, chemical, mechanical, or atomic balance, where the condition appears to be one of rest rather than change. erosion. Destruction of metals or other materials by the abrasive action of moving fluids, usually accelerated by the presence of solid particles or matter in suspension. When corrosion occurs simultaneously, the term erosion-corrosion is often used. erosion-corrosion. A conjoint action involving corrosion and erosion in the presence of a moving corrosive fluid, leading to the accelerated loss of material. eutectic. (1) An isothermal reversible reaction in which a liquid solution is converted into two or more intimately mixed solids upon cooling; the number of solids formed equals the number of components in the system. (2) An alloy having the composition indicated by the eutectic point on an equilibrium diagram. (3) An alloy structure of intermixed solid constituents formed by a eutectic reaction. eutectic melting. Melting of localized microscopic areas whose composition corresponds to that of the eutectic in the system. eutectoid. (1) An isothermal, reversible transformation in which a solid solution is converted into two or more intimately mixed solids. The number of solids formed equals the number of components in the system. (2) An alloy having the composition indicated by the eutectoid point on an equilibrium diagram. (3) An alloy structure of intermixed solid constituents formed by a eutectoid transformation. eutectoid point. The composition and temperature of a solid phase that undergoes univariant transformation into two or more other solid phases upon cooling.

F face-centered cubic lattice structure. A unit cell that consists of atoms arranged at cube corners with one atom at the center of each cube face. fatigue. The phenomenon leading to fracture under repeated or fluctuating stresses having a maximum value less than the tensile strength of the material. Fatigue fractures are progressive, beginning as minute cracks that grow under the action of the fluctuating stress. fatigue crack growth rate (da/dN). The rate of crack extension caused by constant-amplitude fatigue loading. fatigue failure. Failure that occurs when a specimen undergoing fatigue completely fractures into two parts, or has softened, or been otherwise significantly reduced in stiffness by thermal heating or cracking. Fatigue

failure generally occurs at loads which, if applied statically, would produce little perceptible effect. Fatigue failures are progressive, beginning as minute cracks that grow under the action of the fluctuating stress. fatigue life. The number of cycles of stress that can be sustained prior to failure for a stated test condition. fatigue limit. The maximum stress that presumably leads to fatigue fracture in a specified number of stress cycles. If the stress is not completely reversed, the value of the mean stress, the minimum stress, or the stress ratio also should be stated. Compare with endurance limit. fatigue ratio. The fatigue limit under completely reversed flexural stress divided by the tensile strength for the same alloy and condition. fatigue strength. The maximum stress that can be sustained for a specified number of cycles without failure, the stress being completely reversed within each cycle unless otherwise stated. FC. Furnace cooled. fcc. Face-centered cubic. FCP. Fatigue crack propagation. filler metal. The metal to be added in making a welded, brazed, or soldered joint. fissure. A small cracklike discontinuity with only slight separation (opening displacement) of the fracture surfaces. The prefixes macro or micro indicate relative size. flake. Powder of an essentially two-dimensional nature. Also, to eject or break off a small two-dimensional particle. flash welding (FW). A resistance welding process that produces coalescence simultaneously over the entire area of abutting surfaces, by the heat obtained from resistance to electric current between the two surfaces, and by the application of pressure after heating is substantially completed. Flashing and upsetting are accompanied by expulsion of molten metal from the joint. fluid die process. A P/M consolidation process. Also known as rapid omnidirectional compaction (ROC) process. flux cored arc welding (FCAW). An arc welding process that joins metals by heating them with an arc between a continuous tubular filler-metal electrode and the work. Shielding is provided by a flux contained within the consumable tubular electrode. Additional shielding may or may not be obtained from an externally supplied gas or gas mixture. foil. Among many definitions is: a flat-rolled product 0.127 mm (0.005 in.), or less, in thickness, regardless of width. (Any flat-rolled product thicker than this dimension is not considered foil.) Only thickness, not width, is a factor in determining foil. forgeability. Term used to describe the relative ability of material to flow under a compressive load without rupture.

Glossary / 337 forged structure. The macrostructure through a suitable section of a forging that reveals direction of working. forging. (1) Plastically deforming metal, usually hot, into desired shapes with compressive force, with or without dies. (2) Reshaping a billet or ingot by hammering. (3) The process of placing a powder in a container, removing the air from the container, and sealing it. This is followed by conventional forging of the powder and container to the desired shape. forging stock. A rod, bar, billet, or other section used to make forgings. formability. The relative ease with which a metal can be shaped through plastic deformation. forming. The shaping of a component or part by bending, stretching, etc. fracture. (1) The irregular surface produced when a piece of metal is broken. (2) To separate a metal or alloy into two or more pieces by an applied load. fracture stress. (1) The maximum principal true stress at fracture. Usually refers to unnotched tensile specimens. (2) The (hypothetical) true stress that will cause fracture without further deformation at any given strain. fracture toughness. See stress-intensity factor. friction welding (FRW). A solid-state process in which materials are welded by the heat obtained from rubbing together surfaces that are held against each other under pressure. FRW. See friction welding. FW. See flash welding.

G gall. (1) To damage the surface of a component by momentary adhesion between facing surfaces. (2) Damage to a compact or die part, caused by adhesion of powder to the die cavity wall or a punch surface. galling. A condition whereby excessive friction between high spots results in localized welding with subsequent spalling and a further roughening of the rubbing surfaces of one or both of two mating parts. gamma structure. An ordered structure of titanium-aluminum compound with a stoichiometry of Ti-Al. gas-carbon arc welding (CAW-G). A carbon arc welding process variation that produces coalescence of metals by heating them with an electric arc between a single carbon electrode and the work. Shielding is obtained from a gas or gas mixture. gas-metal arc welding (GMAW). An arc welding process that produces joining of metals by heating them with an arc between a continuous filler metal (consumable) electrode and the work. Shielding is obtained entirely from an externally supplied gas or gas mixture. Some variations of this process are

called MIG or CO2 welding (nonpreferred terms). gas-shielded arc welding. A general term used to describe gas metal arc welding, gas tungsten arc welding, and flux cored arc welding when gas shielding is employed. gas-tungsten arc welding (GTAW). An arc welding process that produces coalescence of metals by heating them with an arc between a tungsten (nonconsumable) electrode and the work. Shielding is obtained from a gas or gas mixture. At times called tungsten inert gas (TIG) welding. general corrosion. A form of deterioration that is distributed more or less uniformly over a surface. See also corrosion. GMAW. See gas-metal arc welding. grain-boundary alpha. Primary alpha outlining prior beta grain boundaries. It may be continuous unless broken up by subsequent work. Also may accompany blocky alpha. Occurs by slow cooling from the beta field into the alpha-beta field and is associated with insufficient deformation in working. grindability. Relative ease of grinding (analogous to machinability). grinding. Removing material from a workpiece with a grinding wheel or abrasive belt. grinding cracks. Shallow cracks formed in the surface of relatively hard materials because of excessive grinding heat or the high sensitivity of the material. See also grinding sensitivity. grinding sensitivity. Susceptibility of a material to surface damage such as grinding cracks; it can be affected by such factors as hardness, microstructure, hydrogen content, and residual stress. grinding stress. Residual stress, generated by grinding, in the surface layer of work. It may be tensile, compressive, or both. GTAW. See gas-tungsten arc welding. Often called TIG (tungsten inert gas).

H HAD. See high-aluminum defect. hardener. (1) An alloy element introduced to produce strength. (2) An alloy, rich in one or more alloying elements, added to a melt to permit closer composition control than possible by addition of pure metals or to introduce refractory elements not readily alloyed with the base metal. Sometimes called master alloy or rich alloy. hardening. Increasing hardness by suitable chemical, thermal, or mechanical treatment, usually involving heating and cooling. See also age hardening, case hardening, induction hardening, precipitation hardening, and quench hardening. hardness. A measure of the resistance of a material to surface indentation or abrasion; may be thought of as a function of the stress required to produce some specified type of surface deformation. There is no absolute scale

for hardness; therefore, to express hardness quantitatively, each type of test has its own scale of arbitrarily defined hardness. Indentation hardness may be measured by Brinell, Knoop, Rockwell, Scleroscope, and Vickers hardness tests. HAZ. See heat-affected zone. HB. See Brinell hardness number. heat-affected zone (HAZ). That portion of the base metal that has not been melted, but whose mechanical properties or microstructure have been altered by the heat of welding, brazing, soldering, or cutting. heat treatment. Heating and cooling a solid metal or alloy in such a way as to obtain desired conditions or properties. Heating for the sole purpose of hot working is excluded from the meaning of this definition. hexagonal close-packed lattice structure. A unit cell that consists of a hexagonal arrangement of atoms in a plane and surrounding an atom followed by three atoms in the next horizontal plane. This last plane is offset from the initial plane atoms, followed by an identical planar location of atoms above this. If the first plane is A and the second B, then the repetitive arrangement of atom planes is A-B-A-B-A-B and so on. HID. See high-interstitial defect. high-aluminum defect (HAD). An alpha-stabilized region containing an abnormally large amount of aluminum that may extend across a large number of beta grains. It contains an inordinate fraction of primary alpha but has a microhardness only slightly higher than the adjacent matrix. These are also known as type II defects. higher modulus alloys. Alloys in which the modulus values exceed the customary average. These are achieved by texture control and, possibly, by chemistry adjustments. high-interstitial defect (HID). Interstitially stabilized α-phase region in titanium of substantially higher hardness than surrounding material. It arises from very high local nitrogen or oxygen concentrations that increase the β transus and produce the high-hardness, often brittle α phase. Such a defect is often accompanied by a void resulting from thermomechanical working. Also termed type I or low-density interstitial defects, although they are not necessarily low density. HIP. See hot isostatic pressing. hogging. Machining a part from barstock, plate, or a simple forging in which much of the original stock is removed. hot isostatic pressing. (1) A process for simultaneously heating and forming a powder metallurgy compact in which metal powder, contained in a sealed flexible mold, is subjected to equal pressure from all directions at a temperature high enough for sintering to take place. (2) A process similar to the one explained in (1), but applied to castings in order to close internal porosity. hot pressing. Forming a powder metallurgy compact at a temperature high enough to have concurrent sintering.

338 / Titanium: A Technical Guide hot quenching. An imprecise term used to cover a variety of quenching procedures in which a quenching medium is maintained at a prescribed temperature above 70 °C (160 °F). hot-worked structure. The structure of a material worked at a temperature higher than the recrystallization temperature. hot working. Deforming metal plastically at such a temperature and strain rate that recrystallization takes place simultaneously with the deformation, thus avoiding any strain hardening. HR. See Rockwell hardness number. HRA. Rockwell A hardness. HRB. Rockwell B hardness. HRC. Rockwell C hardness. HV. See Vickers hardness number. hydride descaling. Descaling by action of a hydride in a fused alkali. hydride phase. The phase TiHx formed in titanium when the hydrogen content exceeds the solubility limit, generally locally due to some special circumstance. hydrogen embrittlement. A condition of low ductility in metals resulting from the absorption of hydrogen.

I immersion cleaning. Cleaning where the work is immersed in a liquid solution. impingement attack. Corrosion associated with turbulent flow of liquid. May be accelerated by entrained gas bubbles. See also erosion-corrosion. impurities. Undesirable elements or compounds in a material. inclusion. A particle of foreign material in a metallic matrix. The particle is usually a compound (such as an oxide, sulfide, or silicate), but may be of any substance that is foreign to (and essentially insoluble in) the matrix. Inclusions are usually considered undesirable, although in some cases—such as in free-machining metals—manganese sulfides, phosphorus, selenium, or tellurium may be deliberately introduced to improve machinability. induction hardening. A surface-hardening process in which only the surface layer of a suitable ferrous workpiece is heated by electromagnetic induction to above the upper critical temperature and immediately quenched. ingot. A casting of simple shape, suitable for hot working or remelting. intergranular beta. Beta phase situated between alpha grains. It may be at grain corners as in the case of equiaxed alpha-type microstructures in alloys having low beta stabilizer contents. intermetallic compound. A phase in an alloy system having a restricted solid solubility range. Nearly all are brittle and of stoichiometric composition.

interstitial element. An element with a relatively small atom that can assume a position in the interstices of the titanium lattice. Common examples are oxygen, nitrogen, hydrogen, and carbon. interstitial solid solution. A type of solid solution that sometimes forms in alloy systems having two elements of widely different atomic sizes. Elements of small atomic size, such as carbon, hydrogen, oxygen, and nitrogen, often dissolve in solid metals to form this solid solution. The space lattice is similar to that of the pure metal, and the atoms of carbon, hydrogen, oxygen, and nitrogen occupy the spaces or interstices between the metal atoms. investment casting. (1) Casting metal into a mold produced by surrounding (investing) an expendable pattern with a refractory slurry that sets at room temperature after which the wax, plastic, or frozen mercury pattern is removed through the use of heat. The pattern is then fixed at high temperature. Also called precision casting or lost-wax process. (2) A part made by the investment casting process. investment compound. A mixture of a graded refractory filler, a binder, and a liquid vehicle, used to make molds for investment casting. isothermal forging. Forging of a material while maintaining it at an essentially constant forging temperature. isostatic pressing. A process for forming a powder metallurgy compact by applying pressure equally from all directions to metal powder contained in a sealed flexible mold. See also hot isostatic pressing and cold isostatic pressing.

J J. Joules.

K KIc. See critical stress intensity factor. Kroll process. A process for the production of metallic titanium sponge by the reduction of titanium tetrachloride with a more active metal, such as magnesium. The sponge is further processed to granules or powder. Kt. Stress concentration factor.

L laser beam cutting (LBC). A cutting process that severs materials with the heat obtained from the application of a concentrated coherent light beam impinging upon the workpiece to be cut. The process can be used with or without an externally supplied gas.

laser beam welding (LBW). A welding process that produces joining of materials with the heat obtained from the application of a concentrated coherent light beam impinging upon the members to be joined. LBC. See laser beam cutting. LBW. See laser beam welding. liquidus. In a constitution or equilibrium diagram, the locus of points representing the temperatures at which the various compositions in the system begin to freeze on cooling or finish melting on heating. (See also solidus.) longitudinal direction. Usually, the direction parallel to the direction of working in wrought alloys or the direction of crystal growth in directionally solidified or single-crystal cast alloys. Commonly, it corresponds to the direction parallel to the direction of maximum elongation in a worked material. See also normal direction and transverse direction.

M machinability. The relative ease of machining a metal. machining. Removing material from a metal part, usually using a cutting tool, and usually using a power-driven machine. macrostructure. The structure of metals as revealed by macroscopic examination of a specimen. The examination may be carried out using an as-polished or a polished and etched specimen. martensite. (1) The alpha product resulting from cooling from the beta phase region at rates too high to permit transformation by nucleation and growth. Martensite is supersaturated with beta stabilizer. Also called martensitic alpha. (2) A generic term for microstructures formed by diffusionless phase transformation in which the parent and product phases have a specific crystallographic relationship. Martensite is characterized by an acicular pattern in the microstructure in ferrous and nonferrous alloys. The amount of high-temperature phase that transforms to martensite upon cooling depends to a large extent on the lowest temperature attained, there being a distinct starting temperature (Ms) and a temperature at which the transformation is essentially complete (Mf), which is the martensite finish temperature. See also transformation temperature. martensitic. A constituent having a platelike appearance and a mechanism of formation similar to that of martensite. martensitic transformation. A reaction that takes place in some metals on cooling, with the formation of an acicular structure called martensite. master alloy. An alloy, rich in one or more desired addition elements, that is added to a

Glossary / 339 melt to raise the percentage of a desired constituent. matrix. The constituent that forms the continuous or dominant phase of a two-phase microstructure. mechanical properties. The properties of a material that reveal its elastic and inelastic (plastic) behavior when force is applied, thereby indicating its suitability for mechanical (load-bearing) applications. Examples are elongation, fatigue limit, hardness, modulus of elasticity, tensile strength, and yield strength. Compare with physical properties. melting point. The temperature at which a pure metal, compound, or eutectic changes from solid to liquid; the temperature at which the liquid and the solid are in equilibrium. metastable. Refers to a state of pseudoequilibrium that has a higher free energy than the true equilibrium state. metastable beta. A β phase composition that can be partially or completely transformed to martensite, α, or eutectoid decomposition products with thermal or strain-energy during subsequent processing or service exposure. Mf. The temperature at which the martensite reaction is complete. MIG welding. See preferred terms gas-metal arc welding and flux cored arc welding. mill forms, products. Shaped metal not produced in the design of a part or component, (e.g., strip, sheet, plate, tubing, etc.). (A forged disk, however, is not considered a mill product.) mixture. A combination of two or more undissolved materials intimately in contact with one another. Mo. The maximum temperature at which alpha double prime (orthorhombic martensite) begins to form from the beta on cooling. modulus. See modulus of elasticity. modulus of elasticity. A measure of rigidity or stiffness of a metal; the ratio of stress, below the proportional limit, to the corresponding strain. Specifically, the modulus obtained in tension or compression is Young’s modulus (E), stretch modulus, or modulus of extensibility; the modulus obtained in torsion or shear is modulus of rigidity, shear modulus (G), or modulus of torsion; the modulus covering the ratio of the mean normal stress to the change in volume per unit volume is the bulk modulus. modulus of rigidity. See modulus of elasticity. modulus of rupture. Nominal stress at fracture in a bend test or torsion test. In bending, modulus of rupture is the bending moment at fracture divided by the section modulus. In torsion, modulus of rupture is the torque at fracture divided by the polar section modulus. Ms. The maximum temperature at which the alpha prime martensite reaction begins upon cooling from the beta phase. multiple annealing (TA). The process of giving two or more heat treatments to a titanium

alloy to enhance ductility and toughness at the expense of modest decreases in strength. Solution heat treatment and overaging results from multiple annealing of an alloy. Historically, multiple annealing has been called duplex or triplex annealing. It occurs whenever a high-temperature solution heat treatment is followed by a second or third thermal treatment. An example might be a heat treatment of Ti-6Al-4V alloy: at 954 °C (1750 °F) for 2 h and water quenched; plus 593 °C (1100 °F) for 2 h and air cooled; plus 704 °C (1300 °F) for 2 hours and air cooled.

N near-net shape (NNS). A quality of P/M and investment casting techniques. nitriding. Introducing nitrogen into the surface layer of a solid ferrous alloy by holding at a suitable temperature (below Ac1 for ferritic steels) in contact with a nitrogenous material, usually ammonia or molten cyanide of appropriate composition. Quenching is not required to produce a hard case. NNS. See near-net shape. normal direction. That direction perpendicular to the plane of working in a worked material. See also longitudinal direction and transverse direction.

O OD. Outside diameter. ODS. See oxide dispersion strengthening. omega phase. A nonequilibrium, submicroscopic phase that forms as a nucleation and growth product; often thought to be a transition phase during the formation of α from β. It occurs in metastable β alloys and can lead to severe embrittlement. It typically occurs during aging at low temperature but can also be induced by high hydrostatic pressures. OQ. Oil quenched. ordered structures. That crystal structure of a solid solution in which the atoms of different elements seek preferred lattice positions. overaging. Aging under conditions of time and temperature greater than those required to obtain maximum change in a certain property. See also aging. overheating. Heating a metal or alloy to such a high temperature that its properties are impaired. When the original properties cannot be restored by further heat treating, by mechanical working, or by a combination of working and heat treating, the overheating is known as burning. oxidation. (1) A reaction in which there is an increase in valence resulting from a loss of electrons. Contrast with reduction. (2) A corrosion reaction in which the corroded metal forms an oxide; usually applied to reaction

with a gas containing elemental oxygen, such as air. oxide dispersion strengthening (ODS). (1) Said of P/M alloys. (2) Alloys strengthened by the uniform dispersion of refractory oxide particles throughout the matrix.

P P. Plate. PA. See prealloyed powder. passivation. The changing of a chemically active surface of a metal to a much less reactive state. (Contrast with activation.) passivity. A condition in which a piece of metal, because of an impervious covering of oxide or other compound, has a potential much more positive than when the metal is in the active state. PAW. See plasma-arc welding. physical properties. Properties of a metal or alloy that are relatively insensitive to structure and can be measured without the application of force; for example, density, electrical conductivity, coefficient of thermal expansion, magnetic permeability, heat capacity, and lattice parameter. Does not include chemical reactivity. Compare with mechanical properties. pickling. Removal of the oxide film on a casting by a chemical process; pickling is sometimes used solely to show up defects. plasma-arc welding (PAW). An arc-welding process that produces coalescence of metals by heating them with a constricted arc between an electrode and the workpiece (transferred arc) or the electrode and the constricting nozzle (nontransferred arc). Shielding is obtained from hot, ionized gas issuing from an orifice surrounding the electrode and may be supplemented by an auxiliary source of shielding gas, which may be an inert gas or a mixture of gases. Pressure may or may not be used, and filler metal may or may not be supplied. plastic deformation. The permanent (inelastic) distortion of metals under applied stresses. plate. A flat-rolled metal product of some minimum thickness and width—at times less than 610 mm (24 in.). (It is relatively thick when compared with sheet.) platelet alpha. Alpha phase arranged in plates, often in colonies or domains in Widmanstätten structures. Beta may or may not be present. platelet alpha structure. Acicular alpha of a coarser variety, usually with low aspect ratios. This microstructure arises from cooling alpha or alpha-beta alloys from temperatures at which a significant fraction of beta phase exists. platelets. Grains of a phase existing with essentially a two-phase shape; similar to plate. P/M. See powder metallurgy. Poisson’s ratio. The absolute value of the ratio of the transverse strain to the corresponding

340 / Titanium: A Technical Guide axial strain in a body subjected to uniaxial stress; usually applied to elastic conditions. powder. Particles of a solid characterized by small size, nominally within the range of 1 to 1000 μm. powder lubricant. An agent mixed with or incorporated in a powder to facilitate the pressing and ejecting of a powder metallurgy compact. powder metallurgy (P/M). The technology and art of producing metal powders and of the use of metal powders for the production of massive materials and shaped objects. powder metallurgy forging. Plastically deforming a powder metallurgy compact or preform into a fully dense finished shape using compressive force; usually done hot, and usually within closed dies. powder metallurgy part. A shaped object that has been formed from metal powders and sintered by heating below the melting point of the major constituent. A structural or mechanical component made by the powder metallurgy process. powder production. The process by which a powder is produced, such as machining, milling, atomization, condensation, reduction, oxide decomposition, carbonyl decomposition, electrolytic deposition, or precipitation from a solution. powder technology. A broad term encompassing the production and utilization of both metal and nonmetal powders. ppm. Parts per million. prealloyed powder (PA). A metallic powder composed of two or more elements and in which the particles are of the same nominal composition throughout. precipitation. (1) Separation of a new phase from solid or liquid solution, usually with changing conditions of time, temperature, and stress. (2) The removing of a metal from a solution caused by the addition of a reagent by displacement. (3) The removal of a metal from a gas by displacement. precipitation hardening. Hardening caused by the precipitation of a constituent from a supersaturated solid solution. See also age hardening and aging. precipitation heat treatment. Artificial aging in which a constituent precipitates from a supersaturated solid solution at temperatures above room temperature. precision casting. A metal casting of reproducible accurate dimensions regardless of how it is made. precision part, precision sintered part. A powder metallurgy part that is compacted and sintered, closely conforming to specified dimensions without a need for substantial finishing. precision sheet. A section of flat-rolled metal in a short length. The width is considered to be 610 mm (24 in.) or greater. The thickness is less than 0.381 mm (0.015 in.), but greater than 0.127 mm (0.005 in.). precision strip. A section of flat-rolled metal in a short length. The width is considered to

be 610 mm (24 in.), or greater. The thickness is less than 0.381 mm (0.015 in.), but greater than 0.127 mm (0.005 in.). preform. An initially pressed compact to be subjected to repressing or forging. preforming. (1) The initial pressing of a metal powder to form a compact that is to be subjected to a subsequent pressing operation other than coining or sizing. Also, the preliminary shaping of a refractory metal compact after presintering and before the final sintering. (2) Preliminary forming operations, especially for impression die forging. preheat. (1) An early stage in the sintering procedure when, in a continuous furnace, lubricant or binder burnoff occurs without atmosphere protection prior to actual sintering in the protective atmosphere of the high heat chamber. (2) Process of heating a part before welding or brazing. premium grade. A term used to describe titanium alloys used for jet engines. Equivalent of aircraft quality, flight quality. premium quality. See premium grade. premix (noun). A uniform mixture of components prepared by a powder producer for direct use in compacting. See preferred term, mixture. premix (verb). A term sometimes applied to the preparation of a premix. presintered blank. A compact sintered at a low temperature but at a long enough time to make it sufficiently strong for metal working. See also presintering. presintering. Heating a compact to a temperature below the final sintering temperature, usually to increase the ease of handling or shaping of a compact or to remove a lubricant or binder (burnoff) prior to sintering. primary alpha. Alpha phase in a crystallographic structure that is retained from the last high-temperature α-β working or heat treatment. The morphology of α is influenced by the prior thermomechanical history. principal stress normal. The maximum or minimum value of the normal stress at a point in a plane considered with respect to all possible orientations of the considered plane. On such principal planes the shear stress is zero. There are three principal stresses on three mutually perpendicular planes. The state of stress at a point may be: (1) uniaxial, a state of stress in which two of the three principal stresses are zero; (2) biaxial, a state of stress in which only one of the three principal stresses is zero; or (3) triaxial, a state of stress in which none of the principal stresses is zero. Multiaxial stress refers to either biaxial or triaxial stress. prior-beta grain size. Size of β grains established during the most recent β field excursion. Grains may be distorted by subsequent subtransus deformation. Beta grain boundaries may be obscured by a superimposed α-β microstructure and detectable only by special techniques. process annealing. (1) An imprecise term denoting various treatments used to improve

workability. For the term to be meaningful, the condition of the material and the time-temperature cycle used must be stated. (2) A heat treatment used to soften metal for further cold working. In ferrous sheet and wire industries, heating to a temperature close to but below the lower limit of the transformation range and subsequently cooling for working. In the nonferrous industries, heating above the recrystallization temperatures at a time and temperature sufficient to permit the desired subsequent cold working. progressive aging. Aging by increasing the temperature in steps or continuously during the aging cycle.

Q quench aging. Aging induced from rapid cooling after solution heat treatment. quench hardening. Hardening suitable alpha-beta alloys by solution treating and quenching to develop a martensite-like structure. quenching. Rapid cooling. When applicable, the following more specific terms should be used: direct quenching, fog quenching, hot quenching, interrupted quenching, selective quenching, spray quenching, and time quenching. quench time. (1) In resistance welding, the time from the end of weld time to the beginning of temper time. (2) In heat treatment, the time from the removal of an object from a heat source until the object reaches the desired temperature.

R RD. Rolling direction. reactive. Capable of interacting with other elements, most usually with gases such as oxygen or liquids. recrystallization. (1) Formation of new, strain-free grain structure from the structure existing in cold-worked metal. (2) A change from one crystal structure to another, such as that occurring upon heating or cooling through critical temperature. reducing atmosphere. A chemically active protective atmosphere, which at elevated temperature will reduce metal oxides to their metallic state. (Reducing atmosphere is a relative term and such an atmosphere may be reducing to one oxide but not to another oxide.) reduction. (1) In cupping and deep drawing, a measure of the percentage decrease from blank diameter to cup diameter, or of diameter reduction in redraws. (2) In forging, rolling, and drawing, either the ratio of the original to final cross-sectional area or the percentage decrease in cross-sectional area. (3) A reaction in which there is a decrease in

Glossary / 341 valence resulting from a gain in electrons. Contrast with oxidation. reduction in area. (1) Commonly, the difference, expressed as a percentage of original area, between the original cross-sectional area of a tensile test specimen and the minimum cross-sectional area measured after complete separation. (2) The difference, expressed as a percentage of original area, between original cross-sectional area and that after straining the specimen. regrowth alpha. Alpha that grows on pre-existing alpha during cooling. rem. Remainder. REP atomization. Formation of powder, usually of a reactive metal, by an arc struck between a rotating consumable ingot source and a tungsten electrode in a vacuum or a low-reactivity atmosphere. residual stress. Stress remaining in a structure or member as a result of thermal or mechanical treatment or both. Stress arises in fusion welding primarily because the weld metal contracts on cooling from the solidus to room temperature. resistance brazing. Brazing by resistance heating, the joint being part of the electrical circuit. resistance seam welding (RSEW). A resistance welding process that produces coalescence at the faying surfaces by the heat obtained from resistance to electric current through the work parts held together under pressure by electrodes. The resulting weld is a series of overlapping resistance spot welds made progressively along a joint by rotating the electrodes. resistance welding. Welding with resistance heating and pressure, the working being part of the electrical circuit. Examples: resistance spot welding, resistance seam welding, projection welding, and flash butt welding. revert. Reclaimed titanium and/or titanium alloy scrap. ROC. Rapid omnidirectional compaction process. See also fluid die process. Rockwell hardness number. (HR) A number derived from the net increase in the depth of impression as the load on an indenter is increased from a fixed minor load to a major load and then returned to the minor load. Rockwell hardness numbers are always quoted with a scale symbol representing the penetrator, load, and dial used. rotor grade. Titanium alloy material approved for the most stringent rotating-part applications in gas turbine engines. rotor quality turnings. Titanium alloy machining scraps that are carefully segregated and controlled to prevent contamination or, subsequently, inclusions. RSEW. See resistance seam welding. RSR. Rapid solidification rate. RT. Room temperature. rupture stress. The stress at failure. Also known as breaking stress or fracture stress.

S SAW. Submerged arc welding. scaling. (1) Forming a thick layer of oxidation products on metals at high temperature. (2) Depositing water-insoluble constituents on a metal surface, as in cooling tubes and water boilers. SCC. See stress-corrosion cracking. Often associated with hot-salt-induced cracking (HSSCC). seam. On the surface of metal, an unwelded fold or lap that appears as a crack, usually resulting from a discontinuity obtained in casting or in a wrought workpiece. sheet. A flat-rolled metal product of some maximum thickness and minimum width arbitrarily dependent on the type of metal. It is thinner than plate and has a width-to-thickness ratio greater than approximately 50. shot-blasting. A stream of iron shot or grit being directed onto the surface of a casting for the purpose of dislodging foreign materials not removed during removal of a mold. shrinkage. As molten metal solidifies during cooling it contracts, which in turn makes the finished part a little smaller than the mold. shrink cavity. A defect caused by the solidification of metal. In titanium and zirconium, this cavity is caused by the outside surface solidifying before the inside; as the inside hardens and shrinks, it causes a void in the metal. slab. A piece of metal, intermediate between ingot and plate, with the width at least twice the thickness. SMAW. Shielded metal arc welding. solidification. The change in state from liquid to solid on cooling through the melting temperature or melting range. solidification range. The temperature range between the liquidus and the solidus. solidification shrinkage. The reduction in volume of metal from beginning to end of solidification. solidification shrinkage crack. A crack that forms, usually at elevated temperature, because of the internal (shrinkage) stresses that develop during solidification of a metal casting. Also termed hot crack. solid shrinkage. The reduction in volume of metal from the solidus to room temperature. solid solution. A solid crystalline phase containing two or more chemical species in concentrations that may vary between limits imposed by phase equilibrium. solid solution strengthening. A mechanism for strengthening the alloy by dissolved elements in solid solution. solidus. In a constitution or equilibrium diagram, the locus of points representing the temperatures at which various compositions finish freezing on cooling or begin to melt on heating. See also liquidus. solute. The component of a liquid or solid solution that is present to the lesser or minor ex-

tent; the component that is dissolved in the solvent. solution. A phase existing over a range of composition. solution heat treatment (ST). A heat treatment in which an alloy is heated to a suitable temperature, held at that temperature long enough to cause one or more constituents to enter into solid solution, then cooled rapidly enough to hold these constituents in solution. solution heat treatment and overaging (STOA). A process whereby an alloy is “solutioned” high in the alpha-beta range and, after quenching from the temperature, is aged above the standard aging temperature. Used to produce incremented ductility and toughness, but little change in strength. See multiple annealing. spatter. The metal particles expelled during arc or gas welding. They do not form part of the weld. SPF/DB. Superplastic forming/diffusion bonding. splat. Used in powder metallurgy to describe a particle coating occurring during the manufacturing process when a solid particle collides with a liquid particle. Associated with RSR in some instances. sponge. (1) Also called “virgin sponge,” so designated because of its porous, spongelike texture. (2) A form of metal characterized by a porous condition that is the result of the decomposition or reduction of a compound without fusion. The term is applied to one particular form of titanium. sponge titanium powder. Ground and sized titanium sponge. See also Kroll process. spot welding. Welding of lapped parts in which fusion is confined to a relatively small circular area. It is generally resistance welding but may also be gas-tungsten arc, gas-metal arc, or submerged-arc welding. springback. (1) The elastic recovery of metal after cold forming. (2) The degree to which metal tends to return to its original shape or contour after undergoing a forming operation. (3) In flash, upset, or pressure welding, the deflection in the welding machine caused by the upset pressure. ST. See solution heat treatment. STA. Solution heat treated and aged. std. Standard. STDA. Solution treated and double aged. STOA. See solution heat treatment and overaging. stopoff. A material used on the surfaces adjacent to the joint to limit the spread of soldering or brazing filler metal. STQ. Solution treated and quenched. strain. A measure of the relative change in the size or shape of a body. Linear strain is the change per unit length of a linear dimension. True strain (or natural strain) is the natural logarithm of the ratio of the length at the moment of observation to the original gage length. Conventional strain is the linear strain over the original gage length. Shearing strain (or shear strain) is the change in angle

342 / Titanium: A Technical Guide (expressed in radians) between two lines originally at right angles. When the term strain is used alone, it usually refers to the linear strain in the direction of applied stress. strain-age embrittlement. A loss in ductility accompanied by an increase in hardness and strength that occurs with some alloys aged, following plastic deformation. The degree of embrittlement is a function of aging time and temperature, occurring in a matter of minutes at higher temperatures but requiring a few hours to years at room temperature. (Not normally a great concern in nonferrous alloys.) strain hardening. An increase in hardness and strength caused by plastic deformation at temperatures below the recrystallization range. strain rate. The time rate of straining for the usual tensile test. Strain as measured directly on the specimen gage length is used for determining strain rate. Because strain is dimensionless, the units of strain rate are reciprocal time. stress. The intensity of the internally distributed forces or components of forces that resist a change in the volume or shape of a material that is or has been subjected to external forces. Stress is expressed in force per unit area and is calculated on the basis of the original dimensions of the cross section of the specimen. Stress can be either direct (tension or compression) or shear. Usually expressed in pounds per square inch (psi) or megapascals (MPa). stress-corrosion cracking (SCC). Failure of metals by cracking under combined action of corrosion and stress, residual or applied. In brazing, the term applies to the cracking of stressed base metal due to the presence of a liquid filler metal. stress-intensity factor. A scaling factor, usually denoted by the symbol K used in linear-elastic fracture mechanics to describe the intensification of applied stress at the tip of a crack of known size and shape. At the onset of rapid crack propagation in any structure containing a crack, the factor is called the critical stress-intensity factor, or the fracture toughness. Various subscripts are used to denote different loading conditions or fracture toughnesses: Kc. Plane-stress fracture toughness. The value of stress intensity at which crack propagation becomes rapid in sections thinner than those in which plane-strain conditions prevail. KI. Stress-intensity factor for a loading condition that displaces the crack faces in a direction normal to the crack plane (also known as the opening mode of deformation). KIc. Plane-strain fracture toughness. The minimum value of Kc for any given material and condition, which is attained when rapid crack propagation in the opening mode is governed by plane-strain conditions. See critical stress intensity factor. KId. Dynamic fracture toughness. The fracture toughness determined under dynamic load-

ing conditions; it is used as an approximation of KIc for very tough materials. KISCC. Threshold stress intensity factor for stress-corrosion cracking. The critical plane-stain stress intensity at the onset of stress-corrosion cracking under specified conditions. KQ. Provisional value for plane-strain fracture toughness. Kth. Threshold stress intensity for stress-corrosion cracking. The critical stress intensity at the onset of stress-corrosion cracking under specified conditions. ΔK. The range of the stress-intensity factor during a fatigue cycle. stress-relief cracking. Intergranular cracking in the heat-affected zone or weld metal that occurs during the exposure of weldments to elevated temperatures during postweld heat treatment or high-temperature service. stress-relief heat treatment. Uniform heating of a structure or a portion thereof to a sufficient temperature to relieve the major portion of the residual stresses, followed by uniform cooling. stress relieving. Heating to a suitable temperature, holding long enough to reduce residual stresses, and then cooling slowly enough to minimize the development of new residual stresses. stress-rupture test. A method of evaluating elevated-temperature durability in which a tension-test specimen is stressed under constant load until it breaks. Data recorded commonly include: initial stress, time to rupture, initial extension, creep extension, plus reduction of area at fracture. Also known as creep-rupture test. striation. A fatigue fracture feature often observed in electron micrographs that indicates the position of the crack front after each succeeding cycle of stress. The distance between striations indicates the advance of the crack front across that crystal during one stress cycle, and a line normal to the striation indicates the direction of local crack propagation. substrate. The layer of metal underlying a coating, regardless of whether the layer is base metal. subsurface corrosion. Formation of isolated particles of corrosion products beneath a metal surface. This results from the preferential reaction of certain alloy constituents by inward diffusion of oxygen, nitrogen, or sulfur. superalpha. Refers to titanium alloys in the α-β region, but which have chemistries very close to the α region and contain a very large amount of α. surface hardening. A generic term covering several processes applicable to a suitable ferrous alloy that produces, by quench hardening only, a surface layer that is harder or more wear resistant than the core. There is no significant alteration of the chemical composition of the surface layer. The processes commonly used are induction hardening,

flame hardening, and shell hardening. Use of the applicable specific process name is preferred. surface stability. Ability of a surface to resist interaction with an atmosphere either at low or high temperatures.

T TA. See multiple annealing. TCP. Topologically close-packed. TCR. Temperature coefficient of resistance. TD. See transverse direction. temper. In nonferrous alloys, the hardness and strength produced by mechanical or thermal treatment, or both, characterized by a certain structure, mechanical properties, or reduction in area during cold working. tensile strength (TS). In tensile testing, the ratio of maximum load to original cross-sectional area. Also called ultimate strength. Compare with yield strength. tension. The force or load that produces elongation. tension testing. A method for determining the behavior of materials subjected to uniaxial loading, which tends to stretch the metal. A longitudinal specimen of known length and diameter is gripped at both ends and stretched at a slow, controlled rate until rupture occurs. Also known as tensile testing. tickle. Slang for Ti-Cl4. toll melting. Contracting with a company to melt a metal. transformation temperature. The temperature at which a change in phase occurs. This term is sometimes used to denote the limiting temperature of a transformation range. transformed beta. A local or continuous structure comprising decomposition products arising by nucleation and growth from beta; typically consists of alpha platelets that may or may not be separated by beta phase. transverse direction (TD). Literally “across.” Usually signifying a direction or plane perpendicular to the direction of working. In rolled plate or sheet, the direction across the width is often called long transverse, and the direction through the thickness, short transverse. See also longitudinal direction and normal direction. triplex annealing. See multiple annealing. TS. See tensile strength.

U ultimate strength. The maximum stress (tensile, compressive, or shear) a material can sustain without fracture, determined by dividing maximum load by the original cross-sectional area of the specimen. Also known as nominal strength or maximum strength.

Glossary / 343 ultrasonic welding (USW). A solid state process in which materials are welded by locally applied high-frequency vibratory energy to a joint held together under pressure. unit cell. A unit of atoms arranged such that its repetitive occurrence constitutes a grain of metal. UNS. Unified Numbering System. upset. (1) The localized increase in cross-sectional area of a workpiece or weldment resulting from the application of pressure during mechanical fabrication or welding. (2) Bulk deformation resulting from the application of pressure in welding. The upset may be measured as a percent increase in interfacial area, a reduction in length, or a percent reduction in thickness (for lap joints). upset forging. A forging obtained by upset of a suitable length of bar, billet, or bloom. upsetting. Working metal so that the cross-sectional area of a portion or all of the stock is increased. upset weld. A weld made by upset welding. upset welding (UW). A resistance welding process that produces coalescence simultaneously over the entire area of abutting surfaces or progressively along a joint by the heat obtained from resistance to electric current through the area where those surfaces are in contact. Pressure is applied before heating is started and is maintained throughout the heating period. USW. See ultrasonic welding. UW. See upset welding.

sure reduces the amount of dissolved gas in the metal. vacuum induction melting (VIM). A process for remelting and refining metals in which the metal is melted inside a vacuum chamber by induction heating. The metal may be melted in a crucible, then poured into a mold. The process may also be operated in a configuration similar to that used in consumable electrode remelting except that the heat is supplied by an induction heating coil rather than from the passage of electric current through the electrode. vacuum melting. Melting in a vacuum to prevent contamination from air, as well as to remove gases already dissolved in the metal; the solidification may also be carried out in a vacuum or at low pressure. VAR. See vacuum arc remelting. VHP. Vacuum hot processing. Vickers hardness number (HV). A number related to the applied load and the surface area of the permanent impression made by a square-based pyramidal diamond indenter having included face angles of 136°. Vickers hardness test. An indentation hardness test employing a 136° diamond pyramid indenter (Vickers) and variable loads, enabling the use of one hardness scale for all ranges of hardness—from very soft lead to tungsten carbide. Also known as diamond pyramid hardness test. VIM. See vacuum induction melting.

W V vacuum arc remelting (VAR). A consumable electrode remelting process in which heat is generated by an electric arc between the electrode and the ingot. The process is performed inside a vacuum chamber. Exposure of the droplets of molten metal to the reduced pres-

weldability. A specific or relative measure of the ability of a material to be welded under a given set of conditions. Implicit in this definition is the ability of the completed weldment to fulfill all service designed into the part. Widmanstätten structure. A structure characterized by a geometrical pattern resulting

from the formation of a new phase along certain crystallographic planes of the parent solid solution. The orientation of the lattice in the new phase is related crystallographically to the orientation of the lattice in the parent phase. The structure was originally observed in meteorites, but is readily produced in many alloys, such as titanium, by appropriate heat treatment. wire. A thin, flexible, continuous length of metal, usually of circular cross section, and usually produced by drawing through a die. work hardening. Same as strain hardening. WQ. Water quenched. wrought. A metal or alloy that has been deformed plastically one or more times and exhibits little or no evidence of cast structure. See also cast. wt. Weight.

Y yield. (1) As a noun: the weight of a finished casting divided by the total weight of metal needed to produce it, including running systems, etc. (2) As a verb: to deform plastically on the first instance in a tensile or compressive test. See also yield point. yield point. The first stress in a material, usually less than the maximum attainable stress, at which an increase in strain occurs without an increase in stress. Only certain metals exhibit a yield point. If there is a decrease in stress after yielding, a distinction may be made between upper and lower yield points. yield strength (YS). The stress at which a material exhibits a specified deviation from proportionality of stress and strain. An offset of 0.2% is used for many metals. Compare with tensile strength. YS. See yield strength.

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Subject Index A Abrasive-blast cleaning, for scale removal . . 87 Abrasive cutting . . . . . . . . . . . . . . . . 313–315(T) wheel material characteristics . . . . . . . . . 313(T) AC, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Acetaldehyde, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Acetate, n-propyl, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Acetic acid corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 307(T) titanium alloy corrosion rate . . . . . . . . . . 311(T) Acetic acid + acetic anhydride, corrosion rate of commercially pure titanium . . 307(T) Acetic acid + chlorine, corrosion rate of commercially pure titanium . . . . . . 307(T) Acetic acid + formic acid corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 307(T) titanium alloy corrosion rate . . . . . . . . . . 311(T) Acetic anhydride, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Acetone, for cleaning . . . . . . . . . . . . . . . . . . . . . 70 Acicular alpha . . . . . . . . . . . . . . . . . 14(F), 15(F), 16–17(F), 19, 36(F), 37(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Acicular alpha plus beta. . . . . . . . . . . . . . . 14(F) Acicular martensite . . . . . . . . . . . . . . . . . . . 16(F) Acicular structure . . . . . . . . . . . . . . 100–101(T) Acid leaching . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Acid pickling . . . . . . . . . . . . . . . . . . . . . . . . . 89(T) after vapor degreasing . . . . . . . . . . . . . . . . . . . 91 Activation, definition. . . . . . . . . . . . . . . . . . . . 333 Adhesive bonding . . . . . . . . . . . . . . . . . . . . . . . . 1 Adipic acid, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Adipic acid + glutaric + acetic acid, corrosion rate of commercially pure titanium . . 307(T) Adiponitrile, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Adipylchloride and chlorobenzene solution, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Advanced P/M composites . . . . . . . . . . . . . . . . 3 AECMA equivalent designations . . . . . 283(T) Aerospace applications. See also individual alloys in Alloy Index. . . 3, 7(F), 8 Aged, abbreviation . . . . . . . . . . . . . . . . . . . 143(T) Age hardened, abbreviation . . . . . . . . . . . 143(T) Age hardening. See also Aging. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Aging. See also Overaging. . . . . . . . . . 55, 56, 57, 58, 59(T), 60–61 alpha-beta alloys . . . . . . . . . . . . . . . . . . . . . . . . 20 before and after welding. . . . . . . . . . . . . . . . . . 65 beta alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . 24(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 final . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

of forgings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 in forming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 partial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 postweld heat treatment . . . . . . . . . . . . . . . . . . 68 of weldments . . . . . . . . . . . . . . . . . . . . . 66, 68(F) Aircraft Boeing 757 . . . . . . . . . . . . . . . . . . . . . . . . . . . 6(F) Boeing, titanium usage from 707 to 757 . . . 10(F) content (%) of some recent military airframes . . . . . . . . . . . . . . . . . . . . . . . . . 47(T) F-14, P/M parts . . . . . . . . . . . . . . . . 50(F), 52(T) F-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39(F) P/M parts . . . . . . . . . . . . 49(F), 50(F), 52(T) F-22 Raptor . . . . . . . . . . . . . . . . . . . . . . . 9, 10(F) F119 engine . . . . . . . . . . . . . . . . . . . . . . . 1(F) F-100, P/M parts . . . . . . . . . . . . . . . . . . . . . 51(F) F-107, P/M parts . . . . . . . . . . . . . . . . . . . . . 52(T) military titanium requirements (including engines). . . . . . . . . . . . . . . . . 10(T) SP71. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1(F) titanium buy weights for commercial and military aircraft . . . . . . . . . . . . . . . . 10(T) Aircraft applications. See also individual alloys in Alloy Index.. . 1(F), 7(F) landing gear beam for Boeing 757 aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . 5, 6(F) transmission case for Osprey vertical take-off and landing aircraft . . . . . . . . 5, 6(F) Allotropy, definition . . . . . . . . . . . . . . . . . . . . 333 Alloy, definition . . . . . . . . . . . . . . . . . . . . . . . . 333 Alloying element definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 effect on atom size . . . . . . . . . . . . . . . . . . . . . . 96 Alloying powder, definition . . . . . . . . . . . . . . 333 Alloy powder, definition . . . . . . . . . . . . . . . . . 333 Alloy steels, machinability rating . . . . . . . . 79(T) Alloy system, definition. . . . . . . . . . . . . . . . . . 333 Alpha alloys . . . . . . . . . . . . . . . . . . . . . . . . . 13, 16 age hardening not recommended . . . . . . . . . . 99 alloying element effects on structure . . . . . 2(F) applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 beta phase content . . . . . . . . . . . . . . . . . . . . . . . 99 brazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 characteristics and data for individual alloys . . . . . . . . . . . . . . . . . . . . . 159–194(F,T) composition . . . . . . . . . . . . . . . . . . . . . . . . . 19(T) cryogenic applications . . . . . . . . . . . . . . . . . . . 18 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 elevated temperature applications . . . . . . . . . 18 forgeability . . . . . . . . . . . . . . . . . . . . . . . . . 18–19 heat treatment. . . . . . . . . . . . . . . . . . . . . . . 55, 56, 57(T), 58(T) heat treatment having minimal effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 hot forming temperature. . . . . . . . . . . . . . . 38(T) mechanical properties . . . . . . . . . . . . . . 102–103 microstructural changes . . . . . . . . . . . . . . 21–22 properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 22(F) scale removal by belt grinding . . . . . . . . . 86–87 solution annealing . . . . . . . . . . . . . . . . . . . . . . . 99 stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

strengthening mechanisms . . . . . . . . . . . . . . . 99 welding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65, 73 Alpha-beta alloys . . . . . . . . . . . 2, 13, 16, 19–20, 99–101(F, T) aging . . . . . . . . . . . . . . . . . . . . . . . . . . . 20, 101(T) alloying element effects on structure . . . . . 2(F) aluminum content effect. . . . . . . . . . . . . . . . . . . 2 brazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 casting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 characteristics and data for individual alloys. . . . . . . . . . . . 195–239(F,T) composition . . . . . . . . . . . . . . . . . . . . . . . . . 20(T) cooling rate effects . . . . . . . . . . . . . . . . . . 101(T) direction of testing, longitudinal vs. transverse. . . . . . . . . . . . . . . . . . . . . . . . 101(T) elevated-temperature properties . . . . . . . . . . . 99 equiaxed structures . . . . . . . . . . . . . . . . . . . . . 100 hardenability . . . . . . . . . . . . . . . . . 20–21, 101(T) heat treatment . . . . . . . . . . . . 2–3, 20–21, 42(T), 55(T), 56, 57(F,T), 58(T), 59–61(F,T), 66, 101 hot forming temperature. . . . . . . . . . . . . . . 38(T) martensitic transformations. . . . . . . . . 16–17(F) mechanical properties . . . . . . . . . . 3, 30–31, 100 microstructure . . . . . . . . . . 14(F), 15(F), 100(F) precipitation hardening . . . . . . . . . . . . . . . . . . 21 properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 22(F) scale removal by belt grinding . . . . . . 86–87(F) solution treatment . . . . . . . . . . . . . . . . . . . . . . . 20 transformation undertaken. . . . . . . . . . . . . . . . 19 welding . . . . . . . . . . . . . . . . . . . . 65–67(F), 69(F) Alpha-beta solution treatment (ABST) . . . . . . . . . . . . . . . . . . . . . . . 30, 42(T) heat treatment method for modifying microstructure and properties of net shape products . . . . . . . . . . . . . . . . . 42(T) Alpha-beta structure, definition. . . . . . . . . . 333 Alpha case. See also Alpha stabilizer. . . . . . . . . . . . . . . . 18, 31, 56, 61–62 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 descaling baths used to remove. . . . . . . . . . . . 87 and hydrogen pickup . . . . . . . . . . . . . . . . . . . . 63 and nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 removal by chemical milling on castings . . . 40 Alpha crystal structure . . . . . . . . . . . . . . . . . . . 2 Alpha double prime (orthorhombic martensite) . . . . . . . . . . . . . . . . . . . 16, 22, 23 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Alpha formers . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Alpha phase . . . . . . . . . . . . . . . . 13(F), 16, 61, 68 and beta annealing. . . . . . . . . . . . . . . . . . . . . . . 58 Alpha-phase stabilization . . . . . . . . . . . . . . . . 96 Alpha plates . . . . . . . . . . . . . . . . . . . . . . . . . 22, 42 Alpha prime (hexagonal martensite) . . . . . . . . . . 15(F), 16, 22, 23, 68 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Alpha prime matrix. . . . . . . . . . . . . . . . . . . 15(F) Alpha segregation . . . . . . . . . . . . . . . . . 29–30(F) Alpha stabilizer . . . . . . . . . . . . . . . 14–15(T), 18, 19, 61, 95 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

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352 / Subject Index Alpha stabilizer (continued) in alpha-beta alloys. . . . . . . . . . . . . . . . . . . . . 100 in beta alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 and stress-corrosion cracking . . . . . . . . . . . . 129 Alpha transus, definition . . . . . . . . . . . . . . . . 333 Alpha (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Alpha-2 aluminide alloys (Ti3Al) . . . . 131–132 applications . . . . . . . . . . . . . . . . . . . . . . . . 141(T) compositions . . . . . . . . . . . . . . . . . . . . . . . . . . 132 description . . . . . . . . . . . . . . . . . . . . . . . . . 141(T) mechanical properties. . . . . . . . . . . . . . . . 132(F) oxidation resistance . . . . . . . . . . . . . . . . . . . . 132 precision investment casting . . . . . . . . . . . . . 132 strength-to-weight ratio . . . . . . . . . . . . . . 132(F) Alpha-2 structure . . . . . . . . . . . . . . . . . . . . . . . 18 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Aluminum alloying additions and corrosion. . . . . . . . . . 129 alloying element effect on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15(T) as alpha-stabilizing element . . . . . . 2(F), 14–15 content limit in alpha-beta alloys . . . . . . . . . 100 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 307(T) raising beta transus temperature in titanium alloys . . . . . . . . . . . . . . . . . . . . . . . 15 range as alloying element for titanium . . . 15(T) soluble in both alpha and beta phases. . . . . . . 16 as substitutional solid-solution strengthener . . . . . . . . . . . . . . . . . . . . . . . . 102 Aluminum alloys drilling, unit power requirements . . . . . . . 80(T) machinability rating . . . . . . . . . . . . . . . . . . 79(T) milling, unit power requirements . . . . . . . 80(T) turning, unit power requirements . . . . . . . 80(T) Aluminum chloride aerated, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 307(T) corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 307(T) Aluminum fluoride, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Aluminum nitrate, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Aluminum sulfate, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Aluminum sulfate + H2SO4 (sulfuric acid), corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 307(T) Ammonia, anhydrous, corrosion rate of commercially pure titanium . . . . . . 307(T) Ammonia, steam, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Ammonia, water, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Ammonium acetate, corrosion rate of commercially pure titanium . . . . . . 307(T) Ammonium acid phosphate, corrosion rate of commercially pure titanium . . 307(T) Ammonium aluminum chloride, corrosion rate of commercially pure titanium. . . . . . . . . . . . . . 307(T), 308(T) Ammonium bicarbonate, corrosion rate of commercially pure titanium . . 307(T) Ammonium bifluoride, as etchant to check for alpha case removal . . . . . . . . . . . 62 Ammonium bisulfite, corrosion rate of commercially pure titanium . . . . . . . . 307(T) Ammonium carbamate, corrosion rate of commercially pure titanium . . . . . . 308(T) Ammonium chlorate, corrosion rate of commercially pure titanium . . . . . . 308(T) Ammonium chloride, titanium alloy corrosion rate . . . . . . . . . . . . . . . . . . . . 311(T)

Ammonium fluoride, corrosion rate of commercially pure titanium . . . . . . 308(T) Ammonium hydroxide corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 311(T) Ammonium nitrate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Ammonium nitrate + nitric acid, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Ammonium oxalate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Ammonium perchlorate, corrosion rate of commercially pure titanium . . . 308(T) Ammonium sulfate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Ammonium sulfate + sulfuric acid (H2SO4), corrosion rate of commercially pure titanium . . . . . . . . 308(T) Anatase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Angle of rotation, symbols . . . . . . . . . . . . 331(T) Anhydrous methanol/halide solutions . . . . 129 Aniline, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Aniline + aluminum chloride, corrosion rate of commercially pure titanium . . . 308(T) Aniline hydrochloride, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Annealed, abbreviation . . . . . . . . . . . . . . . 143(T) Annealed powder, definition . . . . . . . . . . . . . 333 Annealing. See also Multiple annealing.. . . . . . . . . . . . . . . . . . . . . . . . 55, 56, 57–58(T) before welding . . . . . . . . . . . . . . . . . . . . . . 65, 66 beta annealing . . . . . . . . . . . . . . . . . . . . . . . 57–58 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 duplex annealing. . . . . . . . . . . . . . . . . . . . . 57–58 for weld-repaired castings . . . . . . . . . . . . . . . . 41 mill annealing . . . . . . . . . . . . . . . . . . . . . . . 57–58 recrystallization annealing . . . . . . . . . . . . 57–58 Anodizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Antimony trichloride, corrosion rate of commercially pure titanium . . . . . . 308(T) Applications abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) nonaerospace . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Aqua regia corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 311(T) Aqueous chloride solutions . . . . . . . . . . . . . . 129 Aqueous solutions, environment and temperature conducive to SCC of Ti alloys . . . . . . . . . . . . . . . . . . . . . . . . . 129(T) Arc burns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 Argon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 for shielding. . . . . . . . . . . . . . . . . . . . . . . . . 72, 74 Argon-helium gas, for shielding . . . . . . . . . . . 72 Arsenous oxide, corrosion rate of commercially pure titanium . . . . . . . . 308(T) ASME equivalent designations . . . . . . . 286(T) Associates of the Titanium Information Group . . . . . . . . . . 296–298(T) ASTM equivalent designations . . . . 286–287(T) Astro equivalent designations . . . . . . . . 287(T) As welded, abbreviation. . . . . . . . . . . . . . . 143(T) atm, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Atmosphere for brazing . . . . . . . . . . . . . . . . . . . . . . . . . . 65, 78 for heat treatment . . . . . . . . . . . . . . . 61–63(F,T) for welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 oxidizing . . . . . . . . . . . . . . . . . . . . . . . 62(F,T), 63 Atomic number definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5(T)

Atomic percent, definition . . . . . . . . . . . . . . . 333 Atomic volume, of titanium. . . . . . . . . . . . . . 5(T) Atomic weight, of titanium . . . . . . . . . . . . . . 5(T) Atomization, definition . . . . . . . . . . . . . . . . . . 333 Automotive, abbreviation . . . . . . . . . . . . . 143(T) Average, abbreviation . . . . . . . . . . . . . . . . 143(T) AWG, definition . . . . . . . . . . . . . . . . . . . . . . . . 333 AWS, definition . . . . . . . . . . . . . . . . . . . . . . . . 333 AWS equivalent designations. . . . . . . . . 287(T)

B B, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Bake, definition. . . . . . . . . . . . . . . . . . . . . . . . . 333 Banded structure, definition. . . . . . . . . 333–334 Band sawing . . . . . . . . . . . . . . . 313, 314–315(T) blade characteristics . . . . . . . . . . . . . . . . . 314(T) horizontal machines (cut-off sawing) . . . . . 314 speeds and feeds . . . . . . . . . . . . . . . . . . . . 314(T) vertical machines . . . . . . . . . . . . . . . . . . . . . . 314 B & S, definition . . . . . . . . . . . . . . . . . . . . . . . . 334 Bar abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) manufacturers and suppliers . . . . . . . . . . 304(T) weights per various sizes . . . . . . . . . . . . . 328(T) Bar-flat, weight at width per various thicknesses . . . . . . . . . . . . . . . . . . . . . . 327(T) Barium carbonate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Barium chloride, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Barium fluoride, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Barium hydroxide, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Barium nitrate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Bar-rectangular, weight at width per various thicknesses . . . . . . . . . . . . . . . 328(T) Barstock definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 fatigue properties tested . . . . . . . . . . . . . . . . . 107 Basal plane, definition. . . . . . . . . . . . . . . . . . . 334 Basketweave, definition . . . . . . . . . . . . . . . . . 334 Batch, definition . . . . . . . . . . . . . . . . . . . . . . . . 334 Batch sintering, definition . . . . . . . . . . . . . . . 334 Bauschinger effect . . . . . . . . . . . . . . . . . . . . . . . 37 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 and stress relief . . . . . . . . . . . . . . . . . . . . . . . . . 56 Belt grinding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Benzaldehyde, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Benzene, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Benzene (traces of HCl), corrosion rate of commercially pure titanium . . . . . . 308(T) Benzoric acid, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Beta (β), definition . . . . . . . . . . . . . . . . . . . . . . 334 Beta alloys . . . . . . . . . . . . . . . . . . 13, 16, 101–102 advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 aerospace applications . . . . . . . . . . . . . . . . . . 131 aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24(F) aircraft applications . . . . . . . . . . . . . . . 1(F), 131 alloying element effects on structure . . . . . . . . . . . . . . . . . . . . . 2(F), 24(T) brazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 casting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 characteristics and data for individual alloys. . . . . . . . . . . . 240–282(F,T) composition . . . . . . . . . . . . . . . . . . . . . . . . . 21(T) descaling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 elevated-temperature applications . . . . . . . . . 21

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Subject Index / 353 fatigue influenced by microstructure . . . . . . 107 forgeability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 formability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 heat treatment . . . . . . . . . . . . . . . . 21, 24, 55, 56, 57(T), 58(T), 59, 60–61, 66 hot forming temperature. . . . . . . . . . . . . . . 38(T) machinability . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 mechanical properties . . . . . . . . . . . . . . . 21, 103 metastable alloys . . . . . . . . . . . . . . . . . . . . . . . 2, 3 microstructure . . . . . . . . . . . . . . . . . . . . . . . 14(F) physical properties . . . . . . . . . . . . . . . . . . . . . . 21 postweld aging heat treatment effects. . . . 68(F) properties . . . . . . . . . . . . . . . . . . . . . . . . 21, 22(F) temperature limitations . . . . . . . . . . . . . . . . . . 61 welding . . . . . . . . . . . . . . . . . . . . . . . . . . 66, 69(F) Beta annealing . . . . . . . . . . . . . . . . 57–58, 59–60 heat treating cycle and resulting microstructure. . . . . . . . . . . . . . . . . . . . . 55(T) Beta crystal structure . . . . . . . . . . . . . . . . . . . . . 2 Beta eutectoid stabilizer, definition . . . . . . . 334 Beta fleck . . . . . . . . . . . . . . . . . . . . . . . . 29–30(F), 34, 199, 217 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 Beta grain refinement methods . . . . . . . . . . . 67 Beta grains, and welding . . . . . . . . . . . . . . . 67(F) Beta isomorphous group . . . . . . . . . . . . . . . . . 15 Beta isomorphous stabilizer, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 Beta phase. . . . . . . . . . . . . . . . . . 13(F), 16, 17, 61 and beta annealing. . . . . . . . . . . . . . . . . . . . . . . 58 Beta-phase stabilization. . . . . . . . . . . . . . . . . . 96 Beta processing . . . . . . . . . . . . . . . . . . . . . 30, 135 and stress-corrosion cracking . . . . . . . . . . . . 129 Beta quench, heat treating cycle and resulting microstructure . . . . . . . . . 55(T) Beta segregation. . . . . . . . . . . . . . . . . . . 29–30(F) Beta solution treatment (BST). . . 42(T), 59–60 of castings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 heat treatment method for modifying microstructure and properties of net shape products . . . . . . . . . . . . . . . . . 42(T) Beta solution treatment/overaging (beta-STOA) . . . . . . . . . . . . . . . . . . . . . . . . 42 Beta stabilizers . . . . . . . . . . . . . . . . . . . 14–15(T), 16,18, 19, 66, 69, 95, 100 and hardenability. . . . . . . . . . . . . . . . . . . . . . . . 20 in beta alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 in metastable beta alloys . . . . . . . . . . . . . . . . . 68 reducing susceptibility in seawater of stress-corrosion cracking . . . . . . . . . . . . . 130 and solution heat treating . . . . . . . . . . . . . . . . . 60 and stress-corrosion cracking . . . . . . . . . . . . 129 with beta flecks . . . . . . . . . . . . . . . . . . . . . . 29, 30 Beta-STOA. See also overaging; solution heat treatment. . . . . . . . . . . . . . . . . 43 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 Beta stringers . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Beta-to-martensite transition . . . . . . . . . . 16(F) Beta transus. . . . . . . . . . . . . . . . . . . 15(F), 19, 22, 30, 34, 56 and beta annealing temperature . . . . . . . . . . . 58 definition . . . . . . . . . . . . . . . . . . . . . . . . . . 15, 334 and forming . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 and heat treatment of castings . . . . . . . . . . . . . 42 and solution heat treating . . . . . . . . . . . . . . . . . 59 Beta transus temperature . . . . . . . . . . . . 15, 29, 30–31, 38, 56(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 role in die forging . . . . . . . . . . . . . . . . . . . . . . . 33 and welding process . . . . . . . . . . . . . . . . . . . . . 68 Bicycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 7, 9 Billet abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 manufacturers and suppliers . . . . . . 304–305(T)

weights per various sizes . . . . . . . . . . . . . 328(T) Binder, definition . . . . . . . . . . . . . . . . . . . . . . . 334 Biocompatibility . . . . . . . . . . . . . . . . . . . . . . . 5, 8 Biomedical applications. See also individual alloys in Alloy Index. . . . . . . . 1, 7 buffing of parts . . . . . . . . . . . . . . . . . . . . . . . . . 90 castings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 properties desirable. . . . . . . . . . . . . . . . . . . . . 7–8 Bismuth, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Bismuth/lead, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Blank, definition . . . . . . . . . . . . . . . . . . . . . . . . 334 Blended elemental (BE) method . . . . . . . . . . 48 Blended elemental (BE) powder. . . . . 114(F,T) Blended elemental powders, consolidation and shapemaking . . . 51(F), 53 Blue-etch anodizing . . . . . . . . . . . . . . . . . . 29, 62 Body-centered cubic (bcc) crystal structure in Ti-base alloys, symbols. . . . . . . . . . . . . . . . . . . . . . . . . 331(T) Body-centered cubic lattice structure, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 Boiling point, of titanium. . . . . . . . . . . . . . . . 5(T) Boric acid, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Brake bending . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Braze, definition . . . . . . . . . . . . . . . . . . . . . . . . 334 Brazeability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 Braze welding, definition . . . . . . . . . . . . . . . . 334 Brazing . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 65, 66, 77–78(F,T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 filler metal selection . . . . . . . . . . . . . . . 66, 78(T) specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 temperature range . . . . . . . . . . . . . . . . . . . . . . . 66 Brazing filler metal, definition . . . . . . . . . . . 334 Brinell hardness, abbreviation. . . . . . . . . 143(T) Brinell hardness number (HB), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 Brinell hardness test, definition . . . . . . . . . . 334 Brines, industrial, equipment and containers for . . . . . . . . . . . . . . . . . . . . . . . 124 British equivalent designations . . . 285–286(T) Brittle, definition . . . . . . . . . . . . . . . . . . . . . . . 334 Brittle fracture, definition . . . . . . . . . . . . . . . 334 Brittleness, definition . . . . . . . . . . . . . . . . . . . 334 Broaching . . . . . . . . . . . . . . . . . . . 81, 318, 321(T) speeds and feeds . . . . . . . . . . . . . . . . . . . . 321(T) Broken-up structure (BUS) method . . . . . . . . . . . . . . . . . . . 42(T), 51–52, 112, 113(F), 116(F) heat treatment method for modifying microstructure and properties of net shape products . . . . . . . . . . . . . . . . . 42(T) Bromine corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) gas, dry, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) in methyl alcohol, corrosion rate of commercially pure titanium . . 308(T) moist, corrosion rate of commercially pure titanium . . . . . . . . 308(T) water solution, corrosion rate of commercially pure titanium . . 308(T) BS equivalent designations . . . . . . . . . . . 285(T) Buffing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90, 91 limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Built-up edge, lack of . . . . . . . . . . . . . . . . . . . . 80 N-butyric acid, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Buy-to-fly ratio. . . . . . . . . . . . . . . . . . . . . . . . . . 52 Buy weights, for titanium, commercial and military applications . . . . . . . . . . . . 10(T)

C Cabot equivalent, designations . . . . . . . . 287(T) Cadmium, and liquid metal embrittlement of titanium alloys . . . . . . . . . . . . . . . . . . . . 130 Cadmium-liquid or solid, and stress-corrosion cracking . . . . . . . . . . . . . 129 Cake, definition. . . . . . . . . . . . . . . . . . . . . . . . . 334 Calcium bisulfite, corrosion rate . . . . . . . 308(T) Calcium carbonate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Calcium chloride corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 311(T) Calcium hydroxide, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Calcium hypochlorite, corrosion rate of commercially pure titanium . . . . . . 308(T) CAP. See Consolidation by atmospheric pressure. Carbon as alloying addition and corrosion . . . . . . . . 126 content effect on commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . 97(F,T) content effect on titanium embrittlement. . . . . . . . . . . . . . . . . . . . . 25–27 implanted on titanium . . . . . . . . . . . . . . . . 92, 93 raises beta transus temperature in titanium alloys . . . . . . . . . . . . . . . . . . . . . . . 15 Carbon dioxide corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) effect from atmosphere on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61, 63 Carbonitriding, definition . . . . . . . . . . . . . . . 334 Carbon monoxide, effect from atmosphere on titanium alloys . . . . . . . . . . 63 Carbon steel as container material for titanium powder. . . . . . . . . . . . . . . . . . . . . . . . . . . 50–51 machinability rating . . . . . . . . . . . . . . . . . . 79(T) Carbon tetrachloride, corrosion rate of commercially pure titanium . . . . . . 308(T) Carbon tetrachloride + 50% H2O, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Carburizing, definition . . . . . . . . . . . . . . . . . . 334 Case hardening, definition. . . . . . . . . . . . . . . 334 Cast abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 Cast alloys, microstructural adjustments . . . 132 Casting abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) alloys used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 investment casting. . . . . . . . . . . . . . . . . 39, 40(F) oxygen-level control. . . . . . . . . . . . . . . . . . . . . 41 precision investment casting . . . . . . . . . . . . . . 43 processes . . . . . . . . . . . . . . . . . . . . . . . . 40–41(F) rammed-graphite method. . . . . . . . . . . 40, 41(F) technology . . . . . . . . . . . . . . . . . . . . . . . 40–41(F) Castings . . . . . . . . . . . . . . . . . . . . . . 3, 39–45(F,T) advantages for titanium and titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39–40 aircraft applications. . . . . . . . . . . . . . . . . . . 10(F) applications . . . . . . . . . . . . . . . . . . . . . . 42–43(F) biomedical applications . . . . . . . . . . . . . . . 41(F) cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3, 43 design considerations . . . . . . . . . . . . . . . . . . . . 41 design properties. . . . . . . . . . . . . . . . . . 43–45(T) development of technology . . . . . . . . 9–11(F,T) fatigue-limited . . . . . . . . . . . . . . . . . . . . . . . . . . 42 heat treatment. . . . . . . . . . . . . . . . . . . . . . . . 42(T)

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354 / Subject Index Castings (continued) manufacturers and suppliers . . . . . . 304–305(T) mechanical properties . . . . . . . . 40, 43–45(F,T), 110(F,T) physical properties . . . . . . . . . . . . . . . . . . . . . . . 3 weld repair effect. . . . . . . . . . . . . . . . . . . . . . . . 41 Cast-plus-hot isostatically pressed alloys . . . . . . . . . . . . . . . 113–114(F) Cathodic alloying . . . . . . . . . . . . . . . . . . . . . . 126 Cavitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Center bursts . . . . . . . . . . . . . . . . . . . . . . . . 18–19 Centerless grinding, to remove scale . . . . . . . 86 Centrifugal, abbreviation . . . . . . . . . . . . . 143(T) CERMETi. See the Alloy Index. Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65, 71 clamp-on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 flow-purged . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 for welding . . . . . . . . . . . . . . . . . . . . . . . . . 72–73 Charpy impact strength, of unalloyed titanium . . . . . . . . . . . . . . . . . . . . . . . . . . 99(F) Charpy test, definition . . . . . . . . . . . . . . . . . . 334 Chase Ext. CDX equivalent designations . . . . . . . . . . . . . . . . . . . . . 287(T) Chemical conversion coatings . . . . . . . . . 91(T) Chemical milling (CHM). . . . . . . . . . . 83–84(F) for scale removal . . . . . . . . . . . . . . . . . . . . . . . . 87 Chemical vapor deposition (CVD), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 Chinese equivalent designations . . . . . . 283(T) CHIP, definition . . . . . . . . . . . . . . . . . . . . . . . . 334 Chloracetic acid, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Chlorides, and stress-corrosion cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Chloride salts, corroding titanium. . . . . . . . . 123 Chloride salts, hot dry, environment and temperature conducive to stress-corrosion cracking of titanium alloys . . . . . . . . . . . . . . . . . . . 129(T) Chlorinated diphenyl, environment and temperature conducive to SCC of Ti alloys . . . . . . . . . . . . . . . . . . . . . . 129(T) Chlorine avoided in composition of cutting fluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 environment and temperature conducive to SCC of Ti alloys . . . . . . 129(T) Chlorine-wet, titanium alloy corrosion rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311(T) Chlorine dioxide, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Chlorine dioxide + HOCl, H2O + Cl2, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Chlorine dioxide in steam, corrosion rate of commercially pure titanium . . 308(T) Chlorine gas, dry corroding titanium . . . . . . . . . . . . . . . . . . . . . 123 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) Chlorine gas, wet corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) corrosion resistance of titanium . . . . . . . . . . 123 Chlorine monoxide (moist), corrosion rate of commercially pure titanium . . 308(T) Chlorine saturated water, corrosion rate of commercially pure titanium . . 308(T) Chlorine trifluoride, corrosion rate of commercially pure titanium . . . . . . 308(T) Chloroform, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Chloroform + water, corrosion rate of commercially pure titanium . . . . . . 308(T) Chloropicrin, corrosion rate of commercially pure titanium . . . . . . . . 308(T)

Chlorosulfonic acid, corrosion rate of commercially pure titanium . . . . . . 308(T) CHM, definition . . . . . . . . . . . . . . . . . . . . . . . . 334 Chromic acid corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) as inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 titanium alloy corrosion rate . . . . . . . . . . 311(T) Chromic acid + nitric acid, corrosion rate of commercially pure titanium . . . 308(T) Chromic ions (r6+), inhibiting titanium corrosion in boiling reducing acids . . . 124(T) Chromium as alloying addition and corrosion . . . . . . . . 126 alloying element effect on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15(T) as beta-stabilizing element . . . . . . . . . . . . . . 2(F) effect in binary alloys on eutectoiod temperature, composition, and content to retain beta . . . . . . . . . . . . . . . 24(T) effective in retaining beta. . . . . . . . . . . . . . 24(T) in eutectoid group . . . . . . . . . . . . . . . . . . . . 15, 16 range as alloying element for titanium . . . 15(T) CIP, definition. . . . . . . . . . . . . . . . . . . . . . . . . . 334 Citric acid aerated, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 311(T) Cleaning. . . . . . . . . . . . . . . . . . . . . 71, 85–89(F,T) before diffusion bonding . . . . . . . . . . . . . . . . . 76 before welding . . . . . . . . . . . . . . . . . . . . 70(F), 73 buffing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90, 91 chemicals producing harmful effects . . . . . . . 91 galvanic effects caused by discontinuities in scaled surfaces . . . . . . . . . . . . . . . . . . . . . 85 gas absorption as problem . . . . . . . . . . 85, 86(F) grease and other soils, removal of. . . . . . . . . . 91 of joint and workpiece surfaces. . . . . . . . . . . . 72 methods. . . . . . . . . . . . . . . . . . . . . . . . . . 61, 70(F) polishing . . . . . . . . . . . . . . . . . . . . . . . . . . 90(F,T) wire brushing . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Climb milling . . . . . . . . . . . . . . . . . . . . . . 320, 321 Close-packed, definition . . . . . . . . . . . . . . . . . 334 Coalescence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Coarse grains, definition . . . . . . . . . . . . . . . . 334 Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 antioxidant spray . . . . . . . . . . . . . . . . . . . . . . . . 62 chemical conversion . . . . . . . . . . . . . . . . . . 91(T) effect on cleanliness . . . . . . . . . . . . . . . . . . . . . 86 gold sprayed on titanium . . . . . . . . . . . . . . . . . 92 to improve higher temperature capability . . . . . . . . . . . . . . . . . . . . . . 135–136 to prevent crevice corrosion . . . . . . . . . . . . . 128 Cobalt alloying additions and corrosion. . . . . . . . . . 129 effect in binary alloys on eutectoid temperature, composition, and content to retain beta . . . . . . . . . . . . . . . 24(T) in eutectoid group . . . . . . . . . . . . . . . . . . . . 15, 16 Coil, manufacturers and suppliers . . . . . . 305(T) Cold drawn, abbreviation . . . . . . . . . . . . . 143(T) Cold finished/formed, abbreviation . . . . 143(T) Cold-gas spray method (CGSM) . . . . . . . . . 134 Cold-hearth melting . . . . . . . . . . . . . . . . . . . . . 29 Cold isostatic pressing (CIP) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 of particulate-reinforced titanium matrix composites . . . . . . . . . . . . . . . . . . . 134 plus vacuum sintering . . . . . . . . . . . . . . . . 49, 51 plus vacuum sintering plus HIP (CHIP) . . . . . . . . . . . . . . . . . . . . . 49, 51(F), 53 Cold pressing, definition. . . . . . . . . . . . . . . . . 335 Cold rolled, abbreviation. . . . . . . . . . . . . . 143(T) Cold worked, abbreviation . . . . . . . . . . . . 143(T)

Cold-worked structure, definition . . . . . . . . 335 Cold working . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 to modify microstructure . . . . . . . . . . . . . . . . 108 Colonies, definition . . . . . . . . . . . . . . . . . . . . . 335 Color, of titanium . . . . . . . . . . . . . . . . . . . . . . 5(T) Columbium, in beta isomorphous group . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15, 16 Commercially pure titanium. See the Alloy Index. Commercial titanium alloys, temperature range, of useful strengths . . . . 1 Compact. . . . . . . . . . . . . . . . . . . . . . . . . . 27, 28(F) blended elemental powder . . . . . . . . . . . . . . . . 48 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 prealloyed powder . . . . . . . . . . . . . . . . . . . . . . 48 Compacting, definition . . . . . . . . . . . . . . . . . . 335 Compaction, definition . . . . . . . . . . . . . . . . . . 335 Computer-aided modeling, for rapid prototyping . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Condenser, abbreviation . . . . . . . . . . . . . . 143(T) Consolidation by atmospheric pressure (AP), definition . . . . . . . . . . . . . 335 Constitutional solution treatment (CST), heat treatment method for modifying microstructure and properties of net shape products . . . . . . 42(T) Consumable electrode, definition. . . . . . . . . 335 Consumable electrode remelting, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 Contaminants, exclusion from joint region . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . 74 during brazing . . . . . . . . . . . . . . . . . . . . . . . . . . 78 evidence (colors). . . . . . . . . . . . . . . . . . . . . 70, 73 of surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 with heat treating. . . . . . . . . . . . . . . . 61–63(F,T) Contamination cracking . . . . . . . . . . . . . . 68, 69 Continuous cooling transformation diagram for Ti-17 . . . . . . . . . . . . . . . . . . . . . . . . . . . 198(F) for Ti-6246 . . . . . . . . . . . . . . . . . . . . . . . . . 201(F) Continuous-drive and inertia friction welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Continuous shot casting (CSC) . . . . . . . . . . . 48 Contour sawing . . . . . . . . . . . . . . . . . . . . . . . . 315 Contractile strain ratio (CSR) . . . . . . . . 163(F) Controlled alpha-beta forging . . . . . . . . . . . 103 Controlled beta forging . . . . . . . . . . . . . . . . . 103 Controlled-hearth melting . . . . . . . . . . . . . . . 28 Conversion factors (mils/in./mm) . . . . . 330(T) Cooling rate after solution treating. . . . . . . . . . 60(F,T), 61(F) and hardenability of alpha-beta alloys. . . 20–21 Copper alloying element effect on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15(T) effect in binary alloys on eutectoid temperature, composition, and content to retain beta . . . . . . . . . . . . . . . 24(T) in eutectoid group . . . . . . . . . . . . . . . . . . . . 15, 16 range as alloying element for titanium . . . 15(T) Copper nitrate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Copper sulfate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Copper sulfate + sulfuric acid, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Corrosion abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . 123, 335 Corrosion embrittlement, definition . . . . . . 335 Corrosion fatigue, definition . . . . . . . . . . . . . 335 Corrosion rates

© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

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Subject Index / 355 for commercially pure titanium, in various media. . . . . . . . . . . . . . . . 307–311(T) for titanium alloys, in various media. . . . . . . . . . . . . . . . . . . . . . . 311–312(T) Corrosion resistance . . . . . . . . . 1, 2, 5, 7, 9, 16, 123–130(F,T) alloying additions and their benefits . . . . . . . . . . . . . . . . . . . . . . . . 126–127 alloying for thermodynamic stability. . . . . . 126 and brazing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 cathodic alloying. . . . . . . . . . . . . . . . . . . . . . . 126 gases, corrosive behavior. . . . . . . . . . . . . . . . 123 heat-affected zones . . . . . . . . . . . . . . . . . . . . . 124 liquids, corrosive behavior . . . . . . . . . . 123–124 minor alloying elements . . . . . . . . . . . . . . . . 124 oxidizers corroding titanium . . . . . . . . . . . . . 124 passivation alloying . . . . . . . . . . . . . . . . . . . . 126 range of metal systems . . . . . . . . . . . . . . . . . . 123 surface treatment . . . . . . . . . . . . . . . . . . 126–127 of weldments . . . . . . . . . . . . . . . . . . . . . . . . . . 124 Corrosive wear, definition . . . . . . . . . . . . . . . 335 Cost of castings . . . . . . . . . . . . . . . . . . . . . . . . . . . 43(F) of titanium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Covalent radius, of titanium . . . . . . . . . . . . . 5(T) Cph, definition . . . . . . . . . . . . . . . . . . . . . . . . . 335 Cracking, time to first . . . . . . . . . . . 106, 107(F) Crack nucleation . . . . . . . . . . . . . . . . . . . . . . . 108 Crack propagation . . . . . . . . . . . . . . . . . . . . . 108 Creep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 Creep limit, definition . . . . . . . . . . . . . . . . . . . 335 Creep rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 Creep recovery, definition . . . . . . . . . . . . . . . 335 Creep resistance, and annealing . . . . . . . . . . . 58 Creep rupture strength, definition . . . . . . . 335 Creep rupture test, definition . . . . . . . . . . . . 335 Creep strain, definition. . . . . . . . . . . . . . . . . . 335 Creep strength . . . . . . . . . . . . . . . . . . . . . . . 16, 18 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 Creep strengthening . . . . . . . . . . . . . . . . . . . . . 58 Creep stress, definition . . . . . . . . . . . . . . . . . . 335 Crevice corrosion . . . . . . . . 123(F), 127–128(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 enhancing resistance. . . . . . . . . . . . . . . . . . . . 128 iron-induced . . . . . . . . . . . . . . . . . . . . . . 127–128 minor alloy element changes for titanium alloy resistance . . . . . . . . . . . . . . 124 and palladium alloying effects . . . . . . . . . . . 126 Critical stress intensity factor (KIc), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 Crucible ceramic mold process (CCMP). . . 51 Crucible equivalent designations . . . . . 287(T) Cryogenic temperatures aerospace applications . . . . . . . . . . . . . . . . . . 117 mechanical properties affected by . . . . . . . . . . . . . . . . . . . . . . . . 117–121(F,T) microstructure affected by. . . . . . 117–121(F,T) Crystal, definition . . . . . . . . . . . . . . . . . . . . . . 335 Crystallization, definition . . . . . . . . . . . . . . . 335 Crystal structure of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5(T) vs. grain structure . . . . . . . . . . . . . . . . . . . . . . . 13 Cupric carbonate + cupric hydroxide, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Cupric chloride, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Cupric cyanide, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Cupric ion (Cu2+), inhibiting titanium corrosion in boiling reducing acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124(T) Cuprous chloride, corrosion rate of commercially pure titanium . . . . . . . . 308(T)

Curing, definition. . . . . . . . . . . . . . . . . . . . . . . 335 Cutting fluids . . . . . . . . . . . . . . . . . . . . . 80, 81(F) CVD. See Chemical vapor deposition. Cyaniding, definition. . . . . . . . . . . . . . . . . . . . 335 Cyclohexane (plus traces of formic acid), corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Cyclohexylamine, corrosion rate of commercially pure titanium . . . . . . . . 308(T)

D DA. See Duplex annealing. da/dN. See Fatigue crack growth rate. Daido equivalent designations . . . . . . . . 284(T) DBTT, definition . . . . . . . . . . . . . . . . . . . . . . . 335 Deep drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Deformation, definition . . . . . . . . . . . . . . . . . 335 Density of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5(T) of titanium, vs. steel or nickel-base superalloys. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Descaling . . . . . . . . . . . . . . . . . . . . . . . . . 85–87(F) aqueous caustic . . . . . . . . . . . . . . . . . . . . . . . . . 88 by molten salt baths. . . . . . . . . . . . . . 87–88(F,T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 metallurgical restrictions. . . . . . . . . . . . . . 85–86 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Designations, equivalent . . . . . . . . . 283–288(T) Dew point, for brazing titanium . . . . . . . . . . . . 78 DFB. See Diffusion brazing. DFW. See Diffusion welding. diam, definition. . . . . . . . . . . . . . . . . . . . . . . . . 335 Diameter, abbreviation . . . . . . . . . . . . . . . 143(T) Dichloroacetic acid, corrosion rate of commercially pure titanium . . . . . . 308(T) Dichlorobenzene + hydrochloric acid, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Diethylene triamine, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Diffusion bonding (DB) . . . . . . . . . . 1, 76–77(F) Diffusion brazing (DFB), definition. . . . . . . 335 Diffusionless transformations . . . . . . . . . . . . 16 Diffusion welding (DFW). See also Diffusion bonding. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 DIN equivalent designations . . . . . 283–284(T) Dispersion-strengthened alloys . . . . . . . . . . 135 Dispersion strengthening . . . . . . . . . . . . . . . 135 Dispersoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Distilled water, environment and temperature conducive to SCC of Ti alloys . . . . . . . . . . . . . . . . . . . . . . . . . 129(T) Double aging, definition . . . . . . . . . . . . . . . . . 335 Double consumable-electrode vacuum-arc remelting process . . . . . . . . 28 Drilling . . . . . . . . . . . . . . . . . . . . . . . . 315–318(T) angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318(T) chip flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 cutting fluid effects . . . . . . . . . . . . . . . . . . . 81(F) machine settings . . . . . . . . . . . . . . . . . . . . 318(T) power requirements. . . . . . . . . . . . . . . . . . . 80(T) speeds and feeds . . . . . . . . . . . . . . . . . . . . 317(T) spiral-point drills . . . . . . . . . . . . . . . . . . 316–317 tool materials . . . . . . . . . . . . . . . 81, 316, 318(T) DTD equivalent designations . . . . . . . . . 285(T) Ductile fracture, definition . . . . . . . . . . . . . . 335 Ductility. See also Plastic deformation. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 Duplex anneal. . . . . . . . . . . . . . . . . . . . . . . . . . . 32

heat treatment cycle and resulting microstructure. . . . . . . . . . . . . . . . . . . . . 55(T) Duplex annealed, abbreviation . . . . . . . . 143(T) Duplex annealing (DA). See also Multiple annealing.. . . . . . . . . 57–58, 112(T) Duplexing, definition. . . . . . . . . . . . . . . . . . . . 335 Dynamic fracture toughness (KId), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

E EBW. See Electron beam welding. EBC. See Electron beam cutting. ECM, definition . . . . . . . . . . . . . . . . . . . . . . . . 335 Elastic modulus . . . . . . . . . . . . . . . . . . . . . . . . . 80 Electrical conductivity, of titanium . . . . . . 5(T) Electrical discharge machining . . . . . 83–84(F) Electrical resistance welded, abbreviation . . . . . . . . . . . . . . . . . . . . . 143(T) Electrical resistivity symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . 331(T) at 20 °C, of titanium . . . . . . . . . . . . . . . . . . . 5(T) Electrochemical machining (ECM). . . . . 83(F) Electrode abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 for gas-tungsten arc welding . . . . . . . . 73–74(T) for making titanium ingots. . . . . . . . . . . . . . . . 27 Electrodeposits. . . . . . . . . . . . . . . . . . . . . . . . . . 92 Electrodynamic degassing. . . . . . . . . . . . . . . . 49 Electrolytic chemical pickling . . . . . . . . . . . . 85 Electron-beam cold-hearth melting (EBCHM) . . . . . . . . . . . . . . . . . . . . . . . 28–29 Electron beam cutting (EBC), definition . . . 336 Electron-beam melting. . . . . . . . . . . . . . . . . . . 28 Electron beam physical vapor deposition, to deposit titanium matrix onto fibers . . . 134 Electron beam welding (EBW) . . . . . 67(F), 68, 70, 71, 75–76 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 modes employed . . . . . . . . . . . . . . . . . . . . . . . . 71 Electronegativity, of titanium . . . . . . . . . . . 5(T) Electroplating copper on titanium alloys . . . . . . . . . . . . . . 92(F) platinum on titanium alloys . . . . . . . . . . . . . . . 92 Electropolishing . . . . . . . . . . . . . . . . . . . . 90(F,T) Electroslag melting . . . . . . . . . . . . . . . . . . . . . . 29 Electrostatic separation . . . . . . . . . . . . . . . . . . 49 ELI. See Extra low interstitial alloys. Elongated alpha . . . . . . . . . . . . . . . . . . . . . . . . . 34 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Elongated grain, definition . . . . . . . . . . . . . . 336 Elongation abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 P/M compacts. . . . . . . . . . . . . . . . . . . . . . . . 52(F) of tensile-test specimen just prior to fracture, symbols . . . . . . . . . . . . . . . . . 331(T) unalloyed titanium. . . . . . . . . . . . . . . . . . . . 18(T) Embrittlement, definition . . . . . . . . . . . . . . . 336 End milling . . . . . . . . . . . . . . . . . . . . . . . 83–84(F) peripheral . . . . . . . . . . . . . . . . . 320–321, 324(T) pocketing technique . . . . . . . . . . . . . . . . . . . . . 81 slotting . . . . . . . . . . . . . . . . . . . . . . . . 320, 323(T) tool materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Endurance limit. . . . . . . . . . . . . . . . . . . . . . . . 108 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 and machining effects . . . . . . . . . . . . . . . . . 83(F) Epitaxial, definition . . . . . . . . . . . . . . . . . . . . . 336 Epitaxy, definition . . . . . . . . . . . . . . . . . . . . . . 336 Equiaxed alpha . . . . . . . . . . . . . . . . 14(F), 17(F), 36(F), 37(T) Equiaxed alpha plus beta . . . . . . . . . . . . . . 14(F)

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356 / Subject Index Equiaxed primary alpha . . . . . . . . . . . . . . 15(F) Equiaxed structure. . . . . . . . . . . . . . 100–101(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Equilibrium, definition . . . . . . . . . . . . . . . . . . 336 Erosion, definition . . . . . . . . . . . . . . . . . . . . . . 336 Erosion-corrosion . . . . . . . . . . . . . . . . . . . . . . 128 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Etch-anodized technique . . . . . . . . . . . 30(F), 62 Ethanol, environment and temperature conducive to SCC of Ti alloys . . . . . . 129(T) Ethyl alcohol. . . . . . . . . . . . . . . . . . . . . . . . . . . 130 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) Ethylene diamine, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Ethylene dichloride, corrosion rate of commercially pure titanium . . . . . . 308(T) Ethylene dichloride + water, corrosion rate of commercially pure titanium . . 308(T) European alloys, casting. . . . . . . . . . . . . . . . . . 39 European equivalent designations. . . 283–284(T) Eutectic, definition. . . . . . . . . . . . . . . . . . . . . . 336 Eutectic melting, definition . . . . . . . . . . . . . . 336 Eutectoid, definition . . . . . . . . . . . . . . . . . . . . 336 Eutectoid point, definition . . . . . . . . . . . . . . . 336 Eutectoid systems . . . . . . . . . . . . . . . . . . . . . . . 15 Eutectoid temperatures . . . . . . . . . . . . . . . . . . 15 Exchanger, abbreviation . . . . . . . . . . . . . . 143(T) Exothermic reactions . . . . . . . . . . . . . . . . . . . 124 Explosive welding . . . . . . . . . . . . . . . . . . . . . . . 76 Extra low interstitial (ELI) alloys . . . . 9, 18, 97 abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 as filler rods for welding castings . . . . . . . . . . 41 for critical applications, cryogenic temperatures . . . . . . . . . . . . . . . . . . . . . . . . 118 hydrogen content limits . . . . . . . . . . . . . . . . . . 97 Extrusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) manufacturers and suppliers . . . . . . . . . . 305(T)

F Fabrication primary . . . . . . . . . . . . . . . . . . . . . . . . . . 30–32(T) secondary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Face-centered cubic lattice structure, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Face milling . . . . . . . . . . . . . . . . . 81, 320, 322(T) Fasteners interference-fit, cadmium-plated . . . . . . . . . 130 manufacturers and suppliers . . . . . . . . . . 305(T) to join titanium products. . . . . . . . . . . . . . . . . . . 1 Fatigue of castings. . . . . . . . . . . . . . . . . . . . . . . . 43, 44(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . 105, 336 in P/M parts . . . . . . . . . . . . . . . . . . . . . . 49, 53(F) and surface treatments . . . . . . . . . . . 107–108(F) Fatigue crack growth rate of castings . . . . . . . . . . . . . . . . . . . . . . . . . . . 44(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Fatigue crack propagation . . . . . . . 108–110(F) Fatigue crack propagation rate, at cryogenic temperatures . . . . . . . . . . . . 121(F) Fatigue endurance limit . . . . . . . . 105, 107, 114 Fatigue failure, definition. . . . . . . . . . . . . . . . 336 Fatigue life . . . . . . . . . . . . . . . . . . . . . . . . 105, 106 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 hot isostatic pressing effect . . . . . . . . . . . . . . . 63 and machining tool sharpness . . . . . . . . . . . . . 80 microstructural parameters of beta alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Fatigue limit, definition . . . . . . . . . . . . . . . . . 336

Fatigue ratio, definition . . . . . . . . . . . . . . . . . 336 Fatigue resistance, effect of unidirectional rolling . . . . . . . . . . . . . . . . . . 32 Fatigue strength at cryogenic temperatures . . . . . . . . 120–121(T) of castings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 FC, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 336 FCAW. See Flux cored arc welding. fcc, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 FCP, definition . . . . . . . . . . . . . . . . . . . . . . . . . 336 Ferric chloride corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 311(T) Ferric ion (Fe3+), inhibiting titanium corrosion in boiling reducing acids . . 124(T) Ferric sulfate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Ferrous chloride + hydrochloric acid, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) Ferrous sulfate, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Filler, abbreviation . . . . . . . . . . . . . . . . . . . 143(T) Filler metal definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 for brazing . . . . . . . . . . . . . . . . . . . . . . . . . . 78(T) for fusion welding. . . . . . . . . . . . . . . . . 71–72(T) Final annealing. . . . . . . . . . . . . . . . . . . . . . . . . . 58 Fire hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 dry mass finishing of titanium parts . . . . . . . . 89 and dry powders for extinguishing fires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81–82 during abrasive blasting . . . . . . . . . . . . . . . . . . 87 during belt grinding . . . . . . . . . . . . . . . . . . . . . 86 Fissure, definition. . . . . . . . . . . . . . . . . . . . . . . 336 Flake, definition . . . . . . . . . . . . . . . . . . . . . . . . 336 Flash reduction of titanium (alloy) vapors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Flash welding (FW). . . . . . . . . . . . . . . . . . . . . . 76 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Flexon. See the Alloy Index. Flow stress, symbols . . . . . . . . . . . . . . . . . 331(T) Fluid die process, definition. . . . . . . . . . . . . . 336 Fluoboric acid, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Fluorine, commercial, corrosion rate of commercially pure titanium . . . . . . 308(T) Fluorine, HF free, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Fluorosilicic acid, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Flux cord arc welding (FCAW), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Fluxes, for brazing . . . . . . . . . . . . . . . . . . . . 65, 78 Foil definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 manufacturers and suppliers . . . . . . . . . . 305(T) Forgeability alpha alloys . . . . . . . . . . . . . . . . . . . . . . . . . 18–19 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Forged structure, definition . . . . . . . . . . . . . 336 Forging . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 5, 6(F), 30, 33–36(F,T) abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) alpha-beta vs. beta forging . . . . . . 35–36, 37(F) applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 beta forging . . . . . . . . . . . . . 34–35, 36(F), 37(F) conventional alpha-beta . . . . . . . . . . . . . . 33–34 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 die forging . . . . . . . . . . . . . . . . . . . . . 33–36(F,T) flow stress of titanium alloys. . . . . . . . 33, 34(F) isothermal beta forging . . . . . . . . . . . . . . . . . . 35 isothermal forging . . . . . . . . . . . . . . . . 34–35, 36 methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

precision die forging. . . . . . . . . . . . . . . . . . . . . 36 stages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 superplastic isothermal die forging . . . . . . . . 34 surface preparation . . . . . . . . . . . . . . . . . . . . . . 33 temperature effect on forging pressure . . . . . . . . . . . . . . . . . . . . . . . 33, 34(F) temperature ranges recommended for titanium alloys . . . . . . . . . . . . . . . . . 34, 35(T) thermomechanical processing schedules . . . . . . . . . . . . . . . . . . . . . . . . . 35(T) Forgings fatigue properties tested . . . . . . . . . . . . . . . . . 107 manufacturers and suppliers . . . . . . . . . . 305(T) Forging skin, hacksawing. . . . . . . . . . . . . . . . 314 Forging stock, definition. . . . . . . . . . . . . . . . . 336 Formability . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3, 9 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Formaldehyde, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Formamide vapor, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Form grinding . . . . . . . . . . . . . . . . . . . . . . . . . 322 Formic acid aerated, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) nitrogen-sparged, titanium alloy corrosion rate . . . . . . . . . . . . . . . . . . . . 311(T) nonaerated, corrosion rate of commercially pure titanium . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 311(T) Forming . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2, 33, 36–38(F,T) aging in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 beta vs. alpha and alpha-beta alloys . . . . . . . . 36 cold forming for strain hardening . . . . . . . . . . 37 creep forming . . . . . . . . . . . . . . . . . . . . . . . 37, 38 deep drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 elevated-temperature . . . . . . . . . . . . . . . . . . . . 58 hot forming . . . . . . . . . . . . . . . . . . . . . . 37, 38(T) limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 overforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 power spinning . . . . . . . . . . . . . . . . . . . . . . . . . 38 press-brake forming . . . . . . . . . . . . . . . . . . . . . 38 rubber-pad forming. . . . . . . . . . . . . . . . . . . . . . 38 stretch forming . . . . . . . . . . . . . . . . . . . . . . . . . 38 superplastic forming . . . . . . . . . . . . . . . . . . . . . 38 temperature range . . . . . . . . . . . . . . . . . . . . . . . 37 Forming limit diagram, for Ti-15-3 . . . . 262(F) Fracture, definition . . . . . . . . . . . . . . . . . . . . . 337 Fracture strength, symbols . . . . . . . . . . . 331(T) Fracture stress, definition . . . . . . . . . . . . . . . 337 Fracture toughness. See also Stressintensity factor. . . . . . . . . . . . . . . . . . . . . . . . . 9 at cryogenic temperatures . . . . . . . . . . . . 120(T) of castings. . . . . . . . . . . . . . . . . . . . . . . . 43, 44(F) P/M compacts . . . . . . . . . . . . . . . . . . . . . . . 53(T) versus density of P/M compacts . . . . . . . 114(F) Friction, coefficient of. . . . . . . . . . . . . . . . . . . . 85 of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5(T) Friction welding (FW) . . . . . . . . . . . . . . . . . . . 76 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 FRW. See Flash welding. Furfural, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 308(T) Furnace brazing. . . . . . . . . . . . . . . . . . . . . . . . . 78 Furnaces for heat treating . . . . . . . . . . . . . . . . . . . . . . . . . 63 for solution heat treating and aging . . . . . . . . 59 vacuum arc remelting . . . . . . . . . . . . . . 27(F), 29 Fusion welding . . . . . . . . . . . . . . . . . 1, 65, 66, 67 filler metals . . . . . . . . . . . . . . . . . . . . . . 71–72(T) practice . . . . . . . . . . . . . . . . . . . . . . . . 70–76(F,T) shielding gases. . . . . . . . . . . . . . . . . . . . . . . . . . 72

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Subject Index / 357 Fusion-zone beta grain size . . . . . . . . . . . . . . . 67 FW. See Flash welding.

G Gall, definition . . . . . . . . . . . . . . . . . . . . . . . . . 337 Galling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Gallium, raises beta transus temperature in titanium alloys . . . . . . . . . . . . . . . . . . . . . 15 Galvanic corrosion . . . . . . . . . . . . . . . . . . 72, 85, 125–126(T) and brazing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Galvanic series in seawater. . . . . . . 125, 126(T) Gamma alloys (TiAl) . . . . . . . . . . . . . . . 131–132 applications . . . . . . . . . . . . . . . . . . . . 132–133(F) automotive applications. . . . . . . . . . . . . . . . . 133 compositions . . . . . . . . . . . . . . . . . . . . . . . . . . 132 cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 mechanical properties . . . . . . . . . . . 132(F), 133 oxidation resistance . . . . . . . . . . . . . . . . . . . . 132 reinforced by titanium boride particles. . . . . . . . . . . . . . . . . . . . . 133–134(F) Gamma aluminide alloys, single-phase applications . . . . . . . . . . . . . . . . . . . . . . . . 141(T) description . . . . . . . . . . . . . . . . . . . . . . . . . 141(T) Gamma aluminide alloys, two-phase applications . . . . . . . . . . . . . . . . . . . . . . . . 141(T) description . . . . . . . . . . . . . . . . . . . . . . . . . 141(T) Gamma prime . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Gamma structure, definition. . . . . . . . . . . . . 337 Garrett treatment (GTEC), heat treatment method for modifying microstructure and properties of net shape products . . . . . . . . . . . . . . . . . 42(T) Gas atomization (GA) process . . . . . . . . . 48, 49 Gas-carbon arc welding (GAW-G), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Gas-metal arc welding (GMAW). . . . . . . . . . . . . . . . . . 67(F), 68, 70, 71, 74(T), 75 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Gas-shielding arc welding, definition . . . . . 337 Gas-tungsten arc cutting . . . . . . . . . . . . . . . . 325 Gas-tungsten arc welding (GTAW) . . . . . . . . . . . . . . . . . . . . . 67–68(F), 69(F), 70, 71, 72, 73–74(F,T), 75 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 for castings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 for welding revert to form an electrode. . . 27–28 Gas turbine engines . . . . . . . . . . . . . . . . . . . . 1(F) GAW-G. See Gas carbon arc welding. General corrosion . . . . . . . . . . . . . . . . . . . . . . 125 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 improvement efforts . . . . . . . . . . . . . . . . . . . . 127 German equivalent designations . . . 283–284(T) Germanium, raises beta transus temperature in titanium alloys . . . . . . . . . . 15 Glass-bead blasting. . . . . . . . . . . . . . 106, 107(F) Glove box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Gloves, use of . . . . . . . . . . . . . . . . . . . . . . . . 70, 85 Gluconic acid, corrosion rate of commercially pure titanium . . . . . . . . 308(T) Glycerin, corrosion rate of commercially pure titanium . . . . . . . . 308(T) GMAW. See Gas-metal arc welding. Golf clubs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 9 GOST equivalent designations. . . . . . . . 285(T) Grain-boundary alpha. . . . . . . . . . . . . 34, 35(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Grain structure, vs. crystal structure . . . . . . . 13 Granules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28(F)

Green density . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Green shapes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Grindability, definition. . . . . . . . . . . . . . . . . . 337 Grinding . . . . . . . . . . . . . . . . . . . . 83(F), 321–322 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 fire hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 surface damage susceptibility . . . . . . . . . . . . . 80 to remove scale . . . . . . . . . . . . . . . . . . . . . . . . . 86 Grinding cracks. See also Grinding sensitivity. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Grinding sensitivity, definition . . . . . . . . . . . 337 Grinding stress, definition . . . . . . . . . . . . . . . 337 Grit blasting, to remove scale . . . . . . . . . . . . . 86 GTAW. See Gas-tungsten arc welding.

H Hacksawing . . . . . . . . . . . . . . . . . . . . 313–314(T) blade characteristics . . . . . . . . . . . . . . . . . 314(T) operational information . . . . . . . . . . . . . . 314(T) speeds and feeds . . . . . . . . . . . . . . . . . . . . 314(T) HAD. See High-aluminum defect. Hafnium, as alpha and beta strengthener . . . . 16 Hall-Petch relation . . . . . . . . . . . . . . . . . . . . . 144 Halogen, avoided in composition of cutting fluids . . . . . . . . . . . . . . . . . . . . . . . . . 81 Hardenability . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 alpha-beta alloys . . . . . . . . . . . . . 20–21, 101(T) Hardener, definition . . . . . . . . . . . . . . . . . . . . 337 Hardening. See also Age hardening; Case hardening; Induction hardening; Precipitation hardening; Quench hardening. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Hardness abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5(T) Hardness testing, not recommended for checking effectiveness of titanium alloy heat treatment . . . . . . . . . . . . . . . . . . . 55 HAZ. See Heat-affected zone. HB. See Brinell hardness number. Heat, abbreviation. . . . . . . . . . . . . . . . . . . . 143(T) Heat-affected zone liquation cracking . . . . . 69 Heat-affected zones (HAZ) . . . . . . . . . . . . 65, 66 corrosion resistance . . . . . . . . . . . . . . . . . . . . 124 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 fracture toughness after heat treatment. . . . . . . . . . . . . . . . . . . . . . . . . 105(T) Heat conductivity . . . . . . . . . . . . . . . . . . . . . . . 80 Heat of fusion, of titanium. . . . . . . . . . . . . . . 5(T) Heat of vaporization, of titanium. . . . . . . . . 5(T) Heat treated, abbreviation . . . . . . . . . . . . 143(T) Heat treating (heat treatment). See also Aging; Annealing; Hot isostatic pressing; Solution heat treatment; Stabilizing; Stress relief heat treatment.. . . . . . . . . . . . . . . . . . . . 55–84(F,T) alpha alloys. . . . . . . . . . . . . . . . . . . . . . . . . 55, 56, 57(T), 58(T) alpha-beta alloys . . . . . . . . . . . . . . . . . 55(T), 56, 57(F,T), 58(T), 59–61(F,T) atmospheres . . . . . . . . . . . . . . . . . . . . 61–63(F,T) atmospheric protection provided . . . . . . . . . . 56 beta alloys . . . . . . . . . . . . . . . . . . . . 24(F), 55, 56, 57(T), 58(T), 59, 60–61 of castings. . . . . . . . . . . . . . . . . . . . . . . . . . . 42(T) cleaning methods . . . . . . . . . . . . . . . . . . . . . . . 56 contamination . . . . . . . . . . . . . . . . . . 61–63(F,T) cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 heating rate and time effect on growth . . . 63(T) near-alpha alloys . . . . . . . . . . . . . . . . . 55, 57(T), 58(T), 59, 60 near-beta alloys . . . . . . . . . . . . . 57(T), 58(T), 59 post-heat treatment processing . . . . 61–63(F,T) pre-heat treatment precautions . . . . . . . . . . . . 61 sufficient stock for metal removal requirements . . . . . . . . . . . . . . . . . . . . . . . . . 56 temperature limitations . . . . . . . . . . . . . . . . . . 56 Helium, for shielding . . . . . . . . . . . . . . . . . . 72, 74 Hexagonal close-packed (hcp) lattice structure definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . 331(T) HID. See High-interstitial defect. High-aluminum defects . . . . . . . . . . . . 29, 30(F) High-cycle fatigue (HCF) . . . . . . . . . . . 106–107 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 machining effects on . . . . . . . . . . . . . . . . . . 83(F) High-density inclusions (HDI) . . . . . . . . . . . . 29 Higher-interstitial defect, definition . . . . . . 337 Higher modulus alloys, definition . . . . . . . . 337 High-purity titanium. See the Alloy Index High-temperature cobalt-base alloys drilling, unit power requirements . . . . . . . 80(T) milling, unit power requirements . . . . . . . 80(T) turning, unit power requirements . . . . . . . 80(T) High-temperature hydrogenation (HTH), heat treatment method for modifying microstructure and properties of net shape products. . . . . . . . . . . . . . . . . . . . . 42(T) High-temperature nickel alloys drilling, unit power requirements . . . . . . . 80(T) milling, unit power requirements . . . . . . . 80(T) turning, unit power requirements . . . . . . . 80(T) High-temperature/short-time roll bonding, of titanium matrix composites . . . . . . . . . . . . . . . . . . . . . . . . . 134 HIP. See Hot isostatic pressing. Hogging, definition . . . . . . . . . . . . . . . . . . . . . 337 Hot-dip coatings, before brazing . . . . . . . . . . . 78 Hot dry chloride salts, and hot salt stress-corrosion cracking . . . . . . . . . . . . . 129 Hot extruded, abbreviation. . . . . . . . . . . . 143(T) Hot finished, abbreviation. . . . . . . . . . . . . 143(T) Hot isostatic pressing (HIP). . . . . . . . . . . 11, 49, 50, 51, 52, 112, 113(F), 114 abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) of castings. . . . . . . . . . . . . . . . . . . . 39(F), 40–41, 41–42, 43, 44(F) crucible ceramic mold process (HIP-CCMP) . . . . . . . . . . . . . . . . . . 51, 52(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 as heat treatment . . . . . . . . . . . . . . . . . . . . . . . . 63 of titanium matrix composites . . . . . . . . . . . 134 Hot pressing, definition. . . . . . . . . . . . . . . . . . 337 Hot quenching, definition. . . . . . . . . . . . . . . . 337 Hot rolled, abbreviation. . . . . . . . . . . . . . . 143(T) Hot roll finishing . . . . . . . . . . . . . . . . . . 31, 32(T) Hot rolling . . . . . . . . . . . . . . . . . . . . . . . . 31, 32(T) Hot salts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 Hot salt stress-corrosion cracking (HSSCC) . . . . . . . . . . . . . . . . . . . . . . . . 18, 63, 129, 130(F,T) relative susceptibility of titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . 130(T) of superalpha alloys . . . . . . . . . . . . . . . . . . . . 135 Hot sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Hot-worked structure, definition . . . . . . . . . 337 Hot worked/wrought, abbreviation . . . . 143(T) Hot working . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Howmet equivalent designations . . . . . . 287(T) c. See Rockwell hardness number.

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358 / Subject Index HRA, definition. . . . . . . . . . . . . . . . . . . . . . . . . 338 HRB, definition. . . . . . . . . . . . . . . . . . . . . . . . . 338 HRC, definition. . . . . . . . . . . . . . . . . . . . . . . . . 338 Hunter process . . . . . . . . . . . . . . . . . . . . . . . . . . 25 HV. See Vickers hardness number. Hydride/dehydride (HDH) process . . . . . . . . . . . . . . . . . . . . . . 48, 49, 134 Hydride descaling, definition . . . . . . . . . . . . 338 Hydride phase . . . . . . . . . . . . . . . . . . . . . . . . . 128 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Hydride precipitation. . . . . . . . . . . . . . . . . . . . 66 Hydrides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96(F) precipitation in commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Hydriding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Hydrochloric acid corroding titanium . . . . . . . . . . . . . . . . . . . . . 123 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 311(T) and titanium corrosion resistance. . . . . . 125, 126 Hydrochloric acid-aerated corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Hydrochloric acid-chlorine saturated corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Hydrochloric acid-deaerated, titanium alloy corrosion rate. . . . . . . . . . . . . . . . 311(T) Hydrochloric acid-hydrogen saturated, titanium alloy corrosion rate. . . . . . . . 312(T) Hydrochloric acid-nitrogen saturated, titanium alloy corrosion rate. . . . . . . . 311(T) Hydrochloric acid-oxygen saturated, titanium alloy corrosion rate. . . . . . . . 312(T) Hydrochloric acid-10%, environment and temperature conducive to SCC of Ti alloys . . . . . . . . . . . . . . . . . . . . . . . . . 129(T) Hydrochloric acid + chlorine, corrosion rate of commercially pure titanium . . 309(T) Hydrochloric acid + CrO3, corrosion rate of commercially pure titanium . . 309(T) Hydrochloric acid + copper chloride, titanium alloy corrosion rate. . . . . . . . 312(T) Hydrochloric acid + copper sulfate, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 309(T) Hydrochloric acid + ferric chloride corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 309(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Hydrochloric acid + ferric chloride + magnesium chloride corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Hydrochloric acid + ferric chloride + magnesium chloride + chlorine, saturated corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 308(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Hydrochloric acid + nitric acid, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 309(T) Hydrochloric acid + phosphoric acid + nitric acid corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 309(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Hydrochloric acid + sodium chlorate, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 309(T)

Hydrochloric acid + titanium ions, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 309(T) Hydrofluoric acid . . . . . . . . . . . . . . . . . . . . . . 125 anhydrous, corrosion rate of commercially pure titanium . . . . . . . . 309(T) corroding titanium . . . . . . . . . . . . . . . . . . . . . 125 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 309(T) Hydrofluoric-nitric acid 5 vol% HF-35 vol% HNO3, corrosion rate of commercially pure titanium . . . . . . 309(T) Hydrogen as beta stabilizer . . . . . . . . . . . . . . . . . . . . . . . . 15 contamination . . . . . . . . . . . . . . . . . . . . . . . . . . 89 damage in titanium . . . . . . . . . . . . . . . . . . . . . 128 effect from atmosphere on titanium alloys. . . . . . . . . . . . . . . . . . . . . . . . . 61, 62–63 effect on commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 96–97(F,T) embrittlement of titanium . . . . . . . . . . . . . . . 124 Hydrogen chloride, environment and temperature conducive to SCC of Ti alloys . . . . . . . . . . . . . . . . . . . . . . . . . 129(T) Hydrogen chloride, gas, corrosion rate of commercially pure titanium . . . . . . 308(T) Hydrogen diffusion coefficient. . . . . . . . . . . 128 Hydrogen embrittlement . . . . . . . . . 68, 69, 128 of commercially pure titanium. . . . . . . . . . 96(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 of weldments . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Hydrogen peroxide corroding titanium . . . . . . . . . . . . . . . . . . . . . 124 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 309(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Hydrogen peroxide + calcium ions, titanium alloy corrosion rate. . . . . . . . 312(T) Hydrogen peroxide + sodium chloride, titanium alloy corrosion rate. . . . . . . . 312(T) Hydrogen peroxide + sodium hydroxide, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 309(T) Hydrogen sulfide, steam and 0.077% mercaptans, corrosion rate of commerciallyl pure titanium . . . . . . . 309(T) Hydrogen sulfide (water saturated), corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 309(T) Hydrovac process (HVC), heat treatment method for modifying microstructure and properties of net shape products . . 42(T) Hydroxy-acetic acid, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Hypochlorous acid + ClO and Cl2 gases, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 309(T)

I Ilmenite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 IMI equivalent designations . . . . . 285–286(T) Immersion cleaning, definition . . . . . . . . . . . 338 Impingement attack. See also Erosion-corrosion. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Implant, abbreviation. . . . . . . . . . . . . . . . . 143(T) Impurities, definition . . . . . . . . . . . . . . . . . . . 338 Inclusion, definition. . . . . . . . . . . . . . . . . . . . . 338 Inconel, corrosion resistance . . . . . . . . . . . 123(F) Induction brazing . . . . . . . . . . . . . . . . . . . . . . . 78 Induction hardening, definition . . . . . . . . . . 338 Induction skull melting . . . . . . . . . . . . . . . . . . 29

Induction slag melting . . . . . . . . . . . . . . . . . . . 29 Industrial applications . . . . . . . . . . . . . . . . . . . . 7 Ingot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 defects. . . . . . . . . . . . . . . . . . . . . . . . . . . 29–30(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 producers of . . . . . . . . . . . . . . . . . . . . 3, 27–30(F) size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Inhibitors, and oxide breakdown. . . . . . . . . . 124 Intergranular beta . . . . . . . . . . . . . . . . . . . . 14(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Intermetallic compound, definition. . . . . . . 338 Intermetallic compound (generic) in Ti-alloy binary phase diagrams, symbols. . . 331(T) International Titanium Association (ITA) Web site . . . . . . . . . . . . . . . . . . . . . 295 Interstitial elements . . . . . . . . . . . . . . . . . . . . . 16 content effect in titanium alloys . . . . . . . . . . . . 2 content effect on mechanical properties . . . . . 9 and corrosion resistance. . . . . . . . . . . . . . . . . 126 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 exclusion from joint region . . . . . . . . . . . . . . . 65 Interstitially stabilized alpha phase . . . . . . . 29 Interstitial solid solution, definition . . . . . . 338 Investment, abbreviation. . . . . . . . . . . . . . 143(T) Investment casting. . . . . . . . . . . . . . . . . 1, 5, 6(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Investment compound, definition . . . . . . . . 338 Iodide titanium, grain size vs. annealing and deformation . . . . . . . . . . . . . . . . . . 146(F) Iodine dry gases, corrosion rate of commercially pure titanium . . . . . . . . 309(T) moist gases, corrosion rate of commerciallyl pure titanium . . . . . . . 309(T) Iodine, in alcohol, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Iodine, in water, + potassium iodide, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 309(T) Ion implantation . . . . . . . . . . . . . . . . . . . 126, 127 aircraft applications . . . . . . . . . . . . . . . . . . . . . 93 biomedical applications . . . . . . . . . . . . . . . . . . 93 processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Ionizable fluoride compounds . . . . . . . . . . . 124 Ionization potential, of titanium . . . . . . . . . 5(T) Ion plating . . . . . . . . . . . . . . . . . . . . . . . . 126, 127 Iron as alloying addition and corrosion . . . . . . . . 126 as beta-stabilizing element . . . . . . . . . . . . . . 2(F) content effect in ELI grades . . . . . . . . . . . . . . . . . . . . . . . 118 on properties of annealed sheet . . . . . . 27(T) on strength of unalloyed Ti . . . . . . . . . . . . 25 effect in binary alloys on eutectoid temperature, composition, and content to retain beta . . . . . . . . . . . . . . . 24(T) in eutectoid group . . . . . . . . . . . . . . . . . . . . 15, 16 surface contamination and hydride formation. . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Isostatic pressing. See also Cold isostatic pressing; Hot isostatic pressing. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Isothermal forging definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Isothermal transformation diagram for Ti-17 . . . . . . . . . . . . . . . . . . . . . . . . . . . 198(F) for Ti-662 . . . . . . . . . . . . . . . . . . . . . . . . . . 219(F)

J Japanese equivalent designations . . . . . 284(T) Jet classification. . . . . . . . . . . . . . . . . . . . . . . . . 49

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Subject Index / 359 JIS equivalent designations . . . . . . 284–285(T) Joining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 conditions necessary. . . . . . . . . . . . . . . . . . . . . 65 design criteria . . . . . . . . . . . . . . . . . . . . . . . . . . 70 limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 technology and practice . . . . . . . . . . 65–84(F,T) Joints design and preparation . . . . . . . . . . . . . . . . . . . 72 dimensions, typical . . . . . . . . . . . . . . . . . . . 72(T) Joules, definition. . . . . . . . . . . . . . . . . . . . . . . . 338

K KIc. See Critical stress intensity factor. Kobe equivalent designations. . . . . . . . . 285(T) Kroll process. . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 as magnesium reduction process . . . . . . . . . . 48 Kt, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

L Laboratory prepared titanium, scaling rates in air. . . . . . . . . . . . . . . . . . . . . . . . . 62(F) Lactic acid, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Larson-Miller parametric relationships, hot salt stress-corrosion cracking of titanium alloys. . . . . . . . . . . . . . . . . . . . 130(F) Laser-assisted gas nitriding process . . . . . . . 93 Laser beam cutting (LBC), definition . . . . . 338 Laser beam machining (LBM) . . . . . . . . . 83(F) Laser beam welding (LBW). . . . . . . . 67(F), 68, 70, 71, 75–76 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Laser forming . . . . . . . . . . . . . . . . . . 134–135(T) Lasform process . . . . . . . . . . . . . . . . 134–135(T) LBC. See Laser beam cutting. LBM. See Laser beam machining. LBW. See Laser beam welding. Lead, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 309(T) Lead acetate, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Leucoxene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Linear thermal expansion, coefficient of, of titanium . . . . . . . . . . . . . . . . . . . . . . 5(T) Linseed oil, boiled, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Liquid, abbreviation . . . . . . . . . . . . . . . . . . 143(T) Liquid metal embrittlement. . . . . . . . . 129, 130 Liquid oxygen corroding titanium . . . . . . . . . . . . . . . . . . . . . 123 storage or transfer not in containers of titanium or its alloys . . . . . . . . . . . . . . . . . 118 Liquid-state alloying. . . . . . . . . . . . . . . . . . . . . 93 Liquidus. See also Solidus. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5(T) Lithium, molten, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Lithium chloride, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Localized corrosion processes . . . . 127–128(F) Longitudinal direction. See also Normal direction; Transverse direction. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Low-cycle fatigue (LCF) . . . . . . . 9, 106–107(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Low-density inclusions (LDI) . . . . . . . . . . . . . 29 Low-pressure plasma spray . . . . . . . . . . . . . 134 Lubricants, for belt grinding . . . . . . . . . . . . . . 86

M Machinability. . . . . . . . . . . . . . . . . . . . 1–2, 79(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Machined, abbreviation. . . . . . . . . . . . . . . 143(T) Machining . . . . . . . . . . . . . . . . . . . . . 79–84(F,T), 313–325(T) cost factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 cutting fluids . . . . . . . . . . . . . . . . . . . . . 80, 81(F) cutting forces . . . . . . . . . . . . . . . . . . 79(F), 80(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 dry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 machinability comparisons . . . . . . . . . . . . 79(T) methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 nontraditional methods . . . . . . . . . . . . . . . . 83(F) power requirements. . . . . . . . . . . . . . . . . . . 80(T) rigidity of setups . . . . . . . . . . . . . . . . . . . . . . . . 80 speeds and feeds . . . . . . . . . . . . . . . . . . 81, 82(T) surface integrity. . . . . . . . . . . . . . . . . . . 83–84(F) tool life . . . . . . . . . . . . . . . . . . . . . . . 80(F), 81(F) tool materials. . . . . . . . . . . . . . . . . . . . . . . . 80–81 tool wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Macroetching . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Macrosegregation . . . . . . . . . . . . . . . . . . . 68–69 Macrostructure definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 and hardening . . . . . . . . . . . . . . . . . . . . . . . . . . 96 modifications done by VAR process . . . . . . . 28 Magnesium, corrosion rate of commerically pure titanium . . . . . . . . 309(T) Magnesium chloride corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 309(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Magnesium hydroxide, corrosion rate of commerically pure titanium . . . . . . 309(T) Magnesium sulfate, corrosion rate of commerically pure titanium . . . . . . . . 309(T) Magnetic susceptibility, symbols . . . . . . 331(T) Magnetic susceptibility (volume, at room tempertature), of titanium . . . . . 5(T) Maleic acid, corrosion rate of commerically pure titanium . . . . . . . . 309(T) Manganese alloying additions and corrosion. . . . . . . . . . 129 as beta-stabilizing element . . . . . . . . . . . . . . 2(F) effect in binary alloys on eutectoid temperature, composition, and content to retain beta . . . . . . . . . . . . . . . 24(T) in eutectoid group . . . . . . . . . . . . . . . . . . . . 15, 16 Manganous chloride, corrosion rate of commercially pure titanium . . . . . . 309(T) Manufacturers addresses, contact information, and products or services described . . . 298–304(T) by primary titanium product or service line . . . . . . . . . . . . . . . . . . . . . . . . . 304–306(T) Martin Mar equivalent designations . . . 287(T) Martinsite. See also Transformation temperature. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Martensite finish (Mf), temperature . . . . . . . . 22 Martensitic abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Martensitic transformation, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Martensitic transformations,. . . . 16–17(F), 19 Mass (barrel) finishing, 89(T)

Master alloy, definition. . . . . . . . . . . . . . . . . . 338 Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Mechanical alloying . . . . . . . . . . . . . . . . . . . . 131 Mechanical die pressing, plus vaccuum sintering . . . . . . . . . . . . . . . . . . . 49 Mechanical properties, definition . . . . . . . . 338 Melting point, of titanium . . . . . . . . . . . . . . . 5(T) Melting point, 2, definition. . . . . . . . . . . . . . . 339 Memorite. See the Alloy Index for this entry. Mercuric chloride, corrosion rate of commerically pure titanium . . . . . . . . 309(T) Mercuric cyanide, corrosion rate of commerically pure titanium . . . . . . . . 309(T) Mercury corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 309(T) and liquid metal embrittlement of titanium alloys . . . . . . . . . . . . . . . . . . . . 130 Mercury + copper, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Mercury + iron, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Mercury + magnesium, corrosion rate of commercially pure titanium . . . . . . 309(T) Mercury + zirconium, corrosion rate of commercially pure titanium . . . . . . 309(T) Mesh-sieve relations, . . . . . . . . . . . . . . . . 330(T) Metal, abbreviation. . . . . . . . . . . . . . . . . . . 143(T) Metal-inert gas welding, to form electrodes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Metastable, definition . . . . . . . . . . . . . . . . . . . 339 Metastable beta, definition . . . . . . . . . . . . . . 339 Metastable beta alloys descaling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 microsegregation. . . . . . . . . . . . . . . . . . . . . . . . 69 properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 scale removal . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 welding . . . . . . . . . . . . . . . . . . . . . . . . . . 68, 69(F) Methanol, environment and temperature conducive to SCC of Ti alloys . . . . . . 129(T) Methyl alcohol . . . . . . . . . . . . . . . . . . . . . . . . . 130 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 309(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Methyl-ethyl-ketone (MEK), for cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Mf, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 “Microcooler” titanium particles . . . . . . 67–68 Micrometer, symbols. . . . . . . . . . . . . . . . . 331(T) Micron, symbols . . . . . . . . . . . . . . . . . . . . . 331(T) Microsegregation . . . . . . . . . . . . . . . . . . . . 68, 69 Microstructure. . . . . . . . . . . . . . 13–14(F), 15(F) beta-annealed . . . . . . . . . . . . . . . . . . . . . . . 109(F) factors affecting mechanical properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 and fatigue . . . . . . . . . . . . . . . . . . . . . 105–107(F) and hardening . . . . . . . . . . . . . . . . . . . . . . . . . . 96 interstitial elements role . . . . . . . . . . . . . . . . . . 96 lamellar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 low-temperature service effects on mechanical properties . . . . . . . 117–121(F,T) and mechanical properties. . . . . . 103–105(F,T) mill-annealed. . . . . . . . . . . . . . . . . . . . . . . . . . 109 modifications done by VAR process . . . . . . . 28 purity specified in user requirements . . . . . . . . 9 recrystalllization-annealed . . . . . . . . . . . . . . 105 of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2(F) of weldments . . . . . . . . . . . . . . . . . . . . . 66–68(F) MIG welding. See Flux cored arc welding; Gas-metal arc welding. MIL equivalent designations . . . . . . . . . 287 (T) Military applications . . . . . . . . . . . . . . . . . . . 1(F) Mill annealing . . . . . . . . . . . . . . . . . . . . 23, 57–58 heat treating cycle and resulting microstructure. . . . . . . . . . . . . . . . . . . . . 55(T)

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360 / Subject Index Mill forms, products, definition . . . . . . . . . . 339 Milling . . . . . . . . . . . . . . . . . . . . 320–321, 322(T), 323(T), 324–325(T) cutters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 power requirements. . . . . . . . . . . . . . . . . . . 80(T) properties . . . . . . . . . . . . . . . . . . . . . . . . 31–32(T) Mixture, definition. . . . . . . . . . . . . . . . . . . . . . 339 MMA equivalent designations . . . . . . . . 285(T) Mo, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Modulus. See Modulus of elasticity. Modulus of elasticity, definition . . . . . . . . . . 339 Modulus of rigidity. See Modulus of elasticity. Modulus of rupture, definition . . . . . . . . . . . 339 Molten salt descaling baths . . . . . . . 87–88(F,T) Molybdenide ion (Mo6+), inhibiting titanium corrosion in boiling reducing acids . . . . . . . . . . . . . . . . . . . . 124(T) Molybdenum alloying additions and corrosion . . . . . 126, 129 alloying element effect on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15(T) as beta-stabilizing element . . . . . . . . . . . . . . 2(F) in beta isomorphous group. . . . . . . . . . . . . . . . 15 range as alloying element for titanium . . . 15(T) with nickel, as alloying elements for corrosion resistance . . . . . . . . . . . . . . . 124 Monel, corrosion resistance . . . . . . . . . . . . 123(F) Monochloracetic acid, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Ms, definition. . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Multiple, abbreviation . . . . . . . . . . . . . . . . 143(T) Multiple annealing, definition. . . . . . . . . . . . 339 Multivalent transition-metal ions, effect on corrosion rate in reducing acids . . . . . . . . . . . . . . . . . . . . 124(T)

N Nanostructured materials. . . . . . . . . . . . . . . 135 Nanostructure processing . . . . . . . . . . . . . . . 135 Near-alpha alloys . . . . . . . . . . . . . . . 2, 13, 14, 16 alloying element effects on structure . . . . . 2(F) brazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 characteristics and data for individual alloys . . . . . . . . . . . . . . . . . . . . . 159–194(F,T) composition . . . . . . . . . . . . . . . . . . . . . . . . . 19(T) description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 elevated-temperature properties . . . . . . . . . . . 99 heat treatment . . . . . . . . . . . . . . . . . . . . 55, 57(T), 58(T), 59, 60 hot-forming temperature . . . . . . . . . . . . . . 38(T) mechanical properties. . . . . . . . . . 102–103, 135 microstructure . . . . . . . . . . . . . . . . . . . . . . . 14(F) properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 22(F) welding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65, 69 Near-beta alloys . . . . . . . . . . . . . . . . . . . . . . . . . . 2 alloying element effects on structure . . . . . 2(F) characteristics and data for individual alloys. . . . . . . . . . . . . . . . . . . . . 240–282(F, T) heat treatment . . . . . . . . . . . . . . 57(T), 58(T), 59 properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 22(F) Near-net shape (NNS) by spray forming . . . . . . . . . . . . . . . . . . . . . . . 134 casting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 for castings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 forgings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 particulate-reinforced titanium matrix composites . . . . . . . . . . . . . . . . . . . . . . . . . 134 P/M alloys . . . . . . . . . . . . . . . . . . . . . . . . . 3, 47, 50 precision die forging. . . . . . . . . . . . . . . . . . . . . 36

Net shape technology, for powder metallurgy . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Nickel as alloying addition and corrosion . . . . . . . . 126 effect in binary alloys on eutectoid temperature, composition, and content to retain beta . . . . . . . . . . . . . . . 24(T) in eutectoid group . . . . . . . . . . . . . . . . . . . . 15, 16 Nickel-base superalloys–René 41, machinability rating . . . . . . . . . . . . . . . . 79(T) Nickel chloride, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Nickel nitrate, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Niobium, alloying additions and corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 Nippon equivalent designations . . . . . . . 285(T) Nitinol. See the Alloy Index. Nitric acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 aerated, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 309(T) anhydrous red fuming, corroding titanium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 corroding titanium . . . . . . . . . . . . . . . . . . . . . 126 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 309(T) as inhibitors . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 not refreshed, corrosion rate of commercially pure titanium . . . . . . . . 309(T) red fuming corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . 309(T) environment and temperature conducive to SCC of Ti alloys . . . 129(T) saturated with zirconyl nitrate, corrosion rate of commercially pure titanium . . 309(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) white fuming, corrosion rate of commerically pure titanium . . . . . . . . 309(T) Nitric acid + 1% Ce(SO4)2, corrosion rate of commercially pure titanium . . 309(T) Nitric acid + 0.01% CrO3, corrosion rate of commercially pure titanium . . 309(T) Nitric acid + FeCl3, corrosion rate of commercially pure titanium . . . . . . . . 309(T) Nitric acid + K2Cr2O7, corrosion rate of commercially pure titanium . . . . . . 309(T) Nitric aid + 1% NaClO3, corrosion rate of commercially pure titanium . . . . . . 309(T) Nitric acid + NaNO3 and NaCl, corrosion rate of commercially pure titanium . . . . . . 309(T) Nitric acid + zirconyl nitrate, corrosion rate of commercially pure titanium . . 309(T) Nitric-hydrofluoric acid. . . . . . . . . . . . . . . . . . 72 for pickle bath . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Nitriding, definition. . . . . . . . . . . . . . . . . . . . . 339 Nitrogen as alloying addition and corrosion . . . . . . . . 126 and alpha case . . . . . . . . . . . . . . . . . . . 61–62, 63 as alpha stabilizer . . . . . . . . . . . . . . . 2(F), 14–15 content effect on commerically pure titanium . . . . . . . . . . . . . . . . . . . . . . . . 97(F,T) content effect on titanium embrittlement. . . . . . . . . . . . . . . . . . . . . 25–27 effect from atmosphere on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 implanted on titanium . . . . . . . . . . . . . . . . 93, 93 raises beta transus temperature in titanium alloys . . . . . . . . . . . . . . . . . . . . . . . 15 Nitrogen tetroxide . . . . . . . . . . . . . . . . . . . . . . 129 corroding titanium . . . . . . . . . . . . . . . . . . . . . 123 environment and temperature conducive to SCC of Ti alloys . . . . . . 129(T) NNS. See Near net shape. Nominal, abbreviation . . . . . . . . . . . . . . . . 143(T)

Nondestructive inspection standards (NDT), for castings . . . . . . . . . . . . . . . . . . . 42 Nonequilibrium phases . . . . . . . . . . . . . . . . . . 16 Normal direction. See also Longitudinal direction; Transverse direction. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Normalized, abbreviation . . . . . . . . . . . . . 143(T) Notch acuity . . . . . . . . . . . . . . . . . . . . 106, 107(F) Not heat treated, abbreviation . . . . . . . . . 143(T) Nozzles of torches, material for . . . . . . . . . . . . 74

O OD, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 339 ODS. See Oxide dispersion strengthening. Omega phase (W). . . . . . . . . . . 16, 17, 58, 61, 68 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 in beta alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . 331(T) Optic-system support structures . . . . . . . . . . . 8 OQ, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Ordered face-centered tetraonal compound of composition near TiAl in Ti-Al alloys, symbols . . . . . . 331(T) Ordered structures, definition . . . . . . . . . . . 339 Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Ordering in the alpha phase . . . . . . . . . . . . . 102 OREMET equivalent designations . . . . . . . . . . . . . . . . 287–288(T) Ores, manufacturers and suppliers . . . . . . 305(T) Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Orthorhombic titanium intermetallics composition . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 strength-to-weight ratio . . . . . . . . . . . . . . 132(F) Osprey process. . . . . . . . . . . . . . . . . . . . . . . . . 134 Others each, abbreviation . . . . . . . . . . . . . 143(T) Others total, abbreviation . . . . . . . . . . . . . 143(T) Otto Fuchs equivalent designations . . . 284(T) Overaging. See also Aging. . . . . . . . . . 37, 56, 61 castings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Overheating, definition. . . . . . . . . . . . . . . . . . 339 Oxalic acid corroding titanium . . . . . . . . . . . . . . . . . . . . . 123 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . 309(T), 310(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Oxidation definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 metal removal required to return to unaffected base metal. . . . . . . . . . . . . . . 62(T) of unalloyed titanium . . . . . . . . . . . . . . . . . . . . 18 Oxidation rates . . . . . . . . . . . . . . . . . . . . . 62(F,T) Oxidation resistance. . . . . . . . . . . . . . . . . . 2, 123 Oxide dispersion strengthening (ODS) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Oxide film layer . . . . . . . . . . . . . . . . . . . . . . . . 126 for corrosion resistance . . . . . . . . . . . . . . . . . 125 as protective layer for corrosion resistance. . . . . . . . . . . . . . . . . . . . . . . . . . . 124 Oxidizing anions, inhibiting corrosion of titanium alloys in reducing acids. . 124(T) Oxidizing metal cations, inhibiting corrosion of titanium alloys in reducing acids . . . . . . . . . . . . . . . . . . . . 124(T) Oxidizing organic compounds, inhibiting corrosion of titanium alloys in reducing acids . . . . . . . . . . . . 124(T) Oxyacetylene cutting . . . . . . . . . . . . . . . . . . . 325 Oxygen as alloying addition and corrosion . . . . . . . . 126 and alpha case . . . . . . . . . . . . . . . . . . . . . . . 61–62

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Subject Index / 361 as alpha stabilizer . . . . . . . . . . . . . . . 2(F), 14–15 content or atmospheric effect in ELI grades. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 content effect on commerically pure titanium . . . . . . . . . . . . . . . . . . . . . . . . 97(F,T) content effect on properties of annealed sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27(T) content effect on strength of unalloyed Ti . . . 25 corroding titanium . . . . . . . . . . . . . . . . . . . . . 123 dissolved, as corrsoion inhibitor. . . . . . . . . . 124 effect from atmosphere on titanium alloys . . . 61 raises beta transus temperature in titanium alloys . . . . . . . . . . . . . . . . . . . . . . . 15 Oxygen cutting. . . . . . . . . . . . . . . . . . . . . . . . . 325

P P, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 PA. See Prealloyed powder. Palladium as alloying element, and corrosion resistance . . . . . . . . . . . . . . . . . . . . . . 124, 126 in eutectoid group . . . . . . . . . . . . . . . . . . . . . . . 16 Palladium-containing pure grades, chemical processing operations . . . . . . . . . . 9 Particulate-reinforced titanium matrix composites mechanical properties . . . . . . . . . . . . . . . . . . 134 as titanium matrix strengthening material . . . . . . . . . . . . . . . . . . . . . 133–134(F) Passivation . . . . . . . . . . . . . . . . . . . . . . . . 125,126 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Passivation alloying . . . . . . . . . . . . . . . . . . . . 126 Passivation potential . . . . . . . . . . . . . . . . . . . . . . 5 Passivity, definition . . . . . . . . . . . . . . . . . . . . . 339 PAW. See Plasma-arc welding. Pearlitic, abbreviation . . . . . . . . . . . . . . . . 143(T) Peening . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66, 106, 107(F), 108 Pendant drop (P-D). . . . . . . . . . . . . . . . . . . . . . 48 Perchloroethylene + water, corrosion rate of commerically pure titanium. . . 310(T) Perchloryl fluoride + liquid ClO3 , corrosion rate of commercially pure titanium . . . . 310(T) Perchloryl fluoride + water, corrosion rate of commercially pure titanium . . 310(T) Phase changes, avoided in joint region . . . . . . 65 Phase diagrams . . . . . . . . . . . . . . . . . . . 13–14(F), 15(F), 23, 24(F) for Ti-662 . . . . . . . . . . . . . . . . . . . . . . . . . . 219(F) titanium-silicon . . . . . . . . . . . . . . . . . . . . . 187(F) Ti-13V-11Cr-3Al . . . . . . . . . . . . . . . . . . . 256(F) to predict forging or heat treat practice . . . . . . . . . . . . . . . . . . . . . . . . . . . 34(F) Phase transformations . . . . . . . . . . . . . 16–17(F) Phase type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 Pheonol, corrosion rate of commerically pure titanium . . . . . . . . . . . . . . . . . . . . . 310(T) Phi (Φ), symbols . . . . . . . . . . . . . . . . . . . . . 331(T) Phosphoric acid . . . . . . . . . . . . . . . . . . . . . . . . 125 corroding titanium . . . . . . . . . . . . . . . . . . . . . 123 corrosion rate of commerically pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) Phosphoric acid, naturally aerated, titanium alloy corrosion rate. . . . . . . . 312(T) Phosphoric acid + nitric acid, corrosion rate of commerically pure titanium . . 310(T) Phosphoric oxychloride, corrosion rate of commerically pure titanium . . . . . . 310(T) Phosphorus trichloride, corrosion rate of commerically pure titanium . . . . . . 310(T) Photographic emulsions, corrosion rate of commerically pure titanium . . . . . . 310(T)

Phthalic acid, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Physical properties, definition . . . . . . . . . . . 339 Physical vapor deposition (PVD). . . . . . . . . 131 Pickling . . . . . . . . . . . . . . . . . . . . . . . . . . 70(F), 72, 88, 128 before belt griding. . . . . . . . . . . . . . . . . . . . . . . 86 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 following descaling . . . . . . . . . . . . . . . 88, 89(T) to remove oxide formations. . . . . . . . . . . . . . . 85 Pipe abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) manufacturers and suppliers . . . . . . . . . . 305(T) weight by outside diameter and wall thickness . . . . . . . . . . . . . . . . . . . . . . . . 330(T) weight per size (in.) by schedule size . . . 329(T) Pitting corrosion . . . . . . . . . . . . . . . . . . . . . . . 128 Plane-strain fracture toughness (KIc) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 and microstructure . . . . . . . . . . . . . . . . . . . . . 104 provisional value (KQ), definition . . . . . . . . 342 Plane-stress fracture toughness (Kc), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Planishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Plasma-arc melting (PAM). . . . . . . . . . . . 28–29 Plasma-arc welding (PAW). . . . . . . . 67, 68, 71, 74–76(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Plasma rotating-electrode process (PREP) . . . . . . . . . . . . . . . . . . . . . . . . . . 48, 49 Plasma spraying, to deposit titanium matrix onto fibers. . . . . . . . . . . . . . . . . . . . 134 Plastic deformation, definition . . . . . . . . . . . 339 Plate abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 manufactuers and suppliers . . . . . . . . . . . 305(T) weight per thickness (gage) . . . . . . . . . . . 328(T) Platelet alpha, definition. . . . . . . . . . . . . . . . . 339 Platelet alpha structure, definition . . . . . . . 339 Platelets, definition . . . . . . . . . . . . . . . . . . . . . 339 Plating, cadmium on parts, and use with titanium discouraged . . . . . . . . . . . . . . . . . 130 Platinum, as alloying addition and corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 P/M. See Powder metallurgy. Poisson’s ratio definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . 331(T) of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5(T) Polishing . . . . . . . . . . . . . . . . . . . . . . . . . . . 90, 108 Porosity. . . . . . . . . . . . . . . . . . . . . . . 40–41, 68, 74 during welding. . . . . . . . . . . . . . . . . . . . . . . . . . 66 in welds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Potassium bromide, corrosion rate of commercially pure titanium . . . . . . 310(T) Potassium chloride, corrosion rate of commercially pure titanium . . . . . . 310(T) Potassium dichromate, corrosion rate of commercially pure titanium . . . . . . 310(T) Potassium ethyl xanthate, corrosion rate of commercially pure titanium . . 310(T) Potassium ferricyanide, corrosion rate of commercially pure titanium . . . . . . 310(T) Potassium hydroxide, corrosion rate of commercially pure titanium. . . . . . . . 310(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Potassium hydroxide + potassium chloride, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Potassium iodide, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Potassium orthophosphate, as grining lubricant. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Potassium perchlorate, corrosion rate of commercially pure titanium . . . . . . 310(T)

Potassium permanganate, corrosion rate of commercially pure titanium . . 310(T) Potassium sulfate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Potassium thiosulfate, corrosion rate of commercially pure titanium . . . . . . 310(T) Pourbaix diagram, for titanium-water system. . . . . . . . . . . . . . . . . . . . . . . . . . . 125(F) Powder abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 manufactuers and suppliers . . . . . . . . . . . 305(T) Powder lubricant, definition . . . . . . . . . . . . . 339 Powder metallurgy (P/M) . . . . . . . . 47–53(F,T) alloys used in applications . . . . . . . . . . . . . . . . 48 applications . . . . . . . . . . . . . . . . . . . . . . . . . 47, 52 benefits of powder metal processing . . . . 47–48 consolidation and shapemaking . . . 49–51(F,T) cost factors. . . . . . . . . . . . . . . . . . . . 47–48, 52(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 mechanical properties. . . . . . . . . . . . 52–53(F,T) oxygen content effects on products . . . . . . . . 47 postcompaction treatments . . . . . . . . . . . . 51–52 powder-making process elemental powder . . . . . . . . . . . . . . 48, 49(F) prealloyed powder . . . . . . . . 48–49, 50(F,T) production processes . . 48–49(F), 50(F), 51(F) pyrophoric characteristic . . . . . . . . . . . . . . . . . 47 Powder metallurgy technology, processing of titanium . . . . . . . . . . . . . . . . . . 1 Powder metallurgy (P/M) titanium alloys complex production techniques . . . . . . . . . . . . 3 costs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 low-chloride content for good fracture toughness. . . . . . . . . . . . . . . . . . . . . . . . . . . 116 mechanical properties . . . . . . . . . 114–117(F,T) near-net shape (NNS) capability . . . . . . . . . . . . 3 physical properties. . . . . . . . . . 114, 115–116(F) versus cast vs. wrought alloys. . . 116–117(F,T) Powder metallurgy forging, definition . . . . 340 Powder metallurgy ingot, isothermal forging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Powder metallurgy part, definition . . . . . . . 340 Powder production, definition . . . . . . . . . . . 340 Powder technology, definition . . . . . . . . . . . 340 Powder under vacuum (PSV for pulverization sous vide) method. . . . . . . 48 ppm, definition . . . . . . . . . . . . . . . . . . . . . . . . . 340 Prealloyed (PA) method. . . . . . . . . . . . . . . . . . 48 Prealloyed (PA) powders. . . . . . . . . . . . . . . . 114 consolidation and shapemaking . . . . . 51, 52(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Precious metal ions, inhibiting corrosion of titanium alloys in reducing acids. . 124(T) Precipitation, definition . . . . . . . . . . . . . . . . . 340 Precipitation hardened,abbreviation . . . 143(T) Precipitation hardening See also Age hardening; Aging. . . . . . . . . . . . . . . . . . . . . 21 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) Precipitation heat treatment, definition . . . 340 Precision casting alpha-2 alloys . . . . . . . . . . . . . . . . . . . . . . . . . 132 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Precision forging, development of technology . . . . . . . . . . . . . . . . . . . . 9–11(F,T) Precision part, definition . . . . . . . . . . . . . . . . 340 Precision sintered part, definition . . . . . . . . 340 Precision sheet, definition . . . . . . . . . . . . . . . 340 Precision strip, definition . . . . . . . . . . . . . . . . 340 Preform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 in powder metallurgy . . . . . . . . . . . . . . . . . 51–52 isothermal forging. . . . . . . . . . . . . . . . . . . . . . . 36 of particulate-reinforced titanium matrix composites . . . . . . . . . . . . . . . . . . . 134

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362 / Subject Index Preforming, definition . . . . . . . . . . . . . . . . . . 340 Preheat, definition . . . . . . . . . . . . . . . . . . . . . . 340 Premium grade, definition. . . . . . . . . . . . . . . 340 Premium quality. See Premium grade. Premix (noun), definition . . . . . . . . . . . . . . . . 340 Premix (verb), definition . . . . . . . . . . . . . . . . 340 Presintered blank. See also Presintering. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Presintering, definition . . . . . . . . . . . . . . . . . . 340 Press cogging . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Press consolidation . . . . . . . . . . . . . . . . . . . 49–50 Press-fit bushings, cadmium plated . . . . . . . 130 Press forming . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Pressure, abbreviation . . . . . . . . . . . . . . . . 143(T) Primary alpha. . . . . . . . . . . . . . . . . . . . . . . . 15(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Principal stress normal, definition. . . . . . . . 340 Prior beta grain boundaries . . . . . . . . . . . 15(F) Prior beta grains . . . . . . . . . . . . . . . . . . . . . . . . 29 Prior beta grain size . . . . . . . . . . . . . . . 67–68(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 and fatigue . . . . . . . . . . . . . . . . . . . . . . . . . 106(F) Process annealing. See also annealing. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Product forms . . . . . . . . . . . . . . . . . . . . . 2, 5, 6(F) primary fabrication . . . . . . . . . . . . . . . . . . . . . . 31 Production cycle for ingot and mill products. . . . . . . . . . 25, 26(F) Progressive aging definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Propionic acid, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Pseudobinary phase daigrams . . . . . 13–14(F), 15(F) Pure titanium. See the Alloy Index for this entry. Pyrogallic acid corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T)

Q Quench aging, definition . . . . . . . . . . . . . . . . 340 Quenched and aged, abbreviation. . . . . . 143(T) Quenched/tempered, abbreviation . . . . . 143(T) Quench hardening, definition . . . . . . . . . . . . 340 Quenching after solution heat treating and aging. . . 60–61(F) of brazed assemblies. . . . . . . . . . . . . . . . . . . . . 66 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 with stress relief. . . . . . . . . . . . . . . . . . . . . . . . . 56 Quench time, definition . . . . . . . . . . . . . . . . . 340

R Radiographic inspection, to check castings . . 42 Rapid prototyping, of castings . . . . . . . . . . . . 40 Rapid solidification rate (RSR) processing . . . . . . . . . . . . . . . . . . . . 3, 48, 135 Powder metallurgy processing . . . . . . . . . . . 131 Rare earth (RE) elements, for inoculation to promote nucleation of beta grains . . . . . 67 RD, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Reactive, definition . . . . . . . . . . . . . . . . . . . . . 340 Reactive plasma ion plating . . . . . . . . . . . . . 127 Reaming . . . . . . . . . . . . . . . . . . . . . . . 318, 319(T) speeds and feeds . . . . . . . . . . . . . . . . . . . . 319(T) Reannealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Reclaimed scrap (revert). . . . . . . . . . . . . . 25, 27 Recrystallization . . . . . . . . . . . . . . 18, 30–31, 76

and beta forging. . . . . . . . . . . . . . . . . . . . . . . . . 34 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 effect on microstructure of alpha alloys . . . 108 Recrystallization-annealed strctures . . . . . 105 Recrystallization annealing . . . . . . . . 18, 57–58 heat treating cycle and resulting microstructure. . . . . . . . . . . . . . . . . . . . . 55(T) Red fuming nitric acid . . . . . . . . . . . . . . . . . . 129 corroding titanium . . . . . . . . . . . . . . . . . . . . . 123 Reducing atmospheres, definition . . . . . . . . 340 Reduction, definition. . . . . . . . . . . . . . . . . . . . 340 Reduction in area definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 P/M compacts. . . . . . . . . . . . . . . . . . . . . . . . 52(F) References, for additional reading . . . . 345–349 Regrowth alpha, definition . . . . . . . . . . . . . . 340 Relief angles . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 Rem, definition . . . . . . . . . . . . . . . . . . . . . . . . . 340 Remelting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Reoxidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 REP atomization, definition . . . . . . . . . 340–341 Residual stress . . . . . . . . . . . . . . . . . . . . . . . . . . 57 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 in alpha and superalpha alloys. . . . . . . . . . . . . 18 in ground titanium surfaces . . . . . . . . . . . . . . 322 in welding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Resistance brazing, definition . . . . . . . . . . . . 341 Resistance seam welding (RSEW) . . . . . 71, 75 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Resistance spot welding . . . . . . . . . . . . . . . . . . 75 Resistance welding . . . . . . . . . . . . . . . . 68, 71, 75 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Resistant, abbreviation . . . . . . . . . . . . . . . 143(T) Resolution heat treatment . . . . . . . . . . . . . . . . 73 Resulfurized steel, machinability rating . . 79(T) Retained beta . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Retained beta fusion zone . . . . . . . . . . . . . . . . 69 Revert. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25, 27 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 melted to form an ingot with titanium sponge and alloy additions . . . . . . . . . . 28(F) to control oxygen content in castings . . . . . . . 41 welded to form the electrode for making titanium ingots . . . . . . . . . . . . . . . . . . . . . . . 27 Rhodium, as alloying addition and corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Ring abbreviations . . . . . . . . . . . . . . . . . . . . . . . 143(T) manufacturers and suppliers . . . . . . . . . . 305(T) Ring rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 RMI equivalent designations . . . . . . . . . 288(T) ROC. See also Fluid die process. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Rockwell hardness number (HR), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Rod abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) manufacturers and suppliers . . . . . . 305–306(T) Roll cogging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Rolling, hot . . . . . . . . . . . . . . . . . . . . . . . 31, 32(T) Room temperature, abbreviation . . . . . . 143(T) Rotating-electrode process (REP) . . 48, 49, 135 Rotor grade, definition . . . . . . . . . . . . . . . . . . 341 Rotor quality turnings, definition . . . . . . . . 341 Rounds, weights per various sizes . . . . . . 328(T) RSEW. See Resistance seam welding. RSR, definition . . . . . . . . . . . . . . . . . . . . . . . . . 341 RT, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Rupture stress, definition. . . . . . . . . . . . . . . . 341 Russian equivalent designations . . . . . . 285(T) Rutile . . . . . . . . . . . . . . . . . . . 3, 25, 125, 126–127 R-value. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

S SAE equivalent designations . . . . . . . . . 288(T) Salicylic acid, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Salt descaling baths . . . . . . . . . . 87–88(F,T), 93 Sand cast, abbreviation . . . . . . . . . . . . . . . 143(T) SAW, definition . . . . . . . . . . . . . . . . . . . . . . . . 341 Sawing . . . . . . . . . . . . . . . . . . . . . . . . . 313–315(T) Scale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62(F) porosity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 removal . . . . . . . . . . . . . . . . . . . . . . 31, 85–87(F) removal, before welding . . . . . . . . . . . . . . . . . 70 variety of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Scaling, definition. . . . . . . . . . . . . . . . . . . . . . . 341 SCC. See Stress-corrosion cracking. Scrap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Seam, definition . . . . . . . . . . . . . . . . . . . . . . . . 341 Seamless, abbreviation. . . . . . . . . . . . . . . . 143(T) Seawater accelerated crack propagation. . . . . . . . . . . . 130 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 310(T) environment and temperature conducive to SCC of Ti alloys . . . . . . 129(T) erosion-corrosion presence . . . . . . . . . . . . . . 128 stress-corrosion cracking and accelerated crack propagation . . . . . . . . . 130 titanium alloy corrosion rate . . . . . . . . . . 312(T) Sebacic acid, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Secondary phase formation . . . . . . . . 16–17(F) Section, abbreviation . . . . . . . . . . . . . . . . . 143(T) Section size and die forging. . . . . . . . . . . . . . . . . . . . 34, 35(F) effect on mechanical properties. . . . . . . . . 31(T) after solution heat treating and aging . . . . . . . . . . . . . . . . . . 60(F,T), 61(F) Segregation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 as defect source in titanium alloy ingots . . . . 29 Shape, abbreviation . . . . . . . . . . . . . . . . . . 143(T) Shape memory alloys . . . . . . . . . . 11(T), 141(T) Sheet abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 manufacturers and suppliers . . . . . . . . . . 306(T) weight per thickness (gage) . . . . . . . . . . . 328(T) Shielded metal arc welding, abbreviation . . . . . . . . . . . . . . . . . . . . . 143(T) Shielding hose material . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 inert gas . . . . . . . . . . . . . . . . . . . 71, 72, 73(F), 74 pressure (psi) gages. . . . . . . . . . . . . . . . . . . . . . 72 torch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 trailing shield. . . . . . . . . . . . . . . . . . 73(F), 74, 75 of weld zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Shot-blasting, definition . . . . . . . . . . . . . . . . . 341 Shot peening. . . . . . . . . . . . . . . . 106, 107(F), 108 Shrinkage . . . . . . . . . . . . . . . . . . . . . . . . . . . 42, 74 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Shrink cavity, definition . . . . . . . . . . . . . . . . . 341 Silicon alloying effect on high-temperature strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 alloying element effect on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15(T) effect in binary alloys on euctectoid temperature, composition, and content to retain beta . . . . . . . . . . . . . . . . . . . . . . 24(T) in eutectoid group . . . . . . . . . . . . . . . . . . . . . . . 15 range as alloying element for titanium . . . 15(T) Silicon carbide as fibers for reinforcing titanium matrix composites. . . . . . . . . . . . . . . 133–134

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Subject Index / 363 Sintered, abbreviation . . . . . . . . . . . . . . . . 143(T) Sintering, temperature . . . . . . . . . . . . . . . . . . . . 51 Silver as antigallant for titanium and hot slat stress-corrosion cracking. . . . . . . . . . 129 and liquid metal embrittlement of titanium alloys . . . . . . . . . . . . . . . . . . . . . . 130 Silver nitrate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Slab, definition . . . . . . . . . . . . . . . . . . . . . . . . . 341 Slab milling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 Slab shapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 SMAW, definition . . . . . . . . . . . . . . . . . . . . . . 341 Sodium, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 310(T) Sodium acetate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium aluminate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium bifluoride, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium bisulfate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Soldium bisulfite, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium carbonate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium chlorate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium chlorate + NaCl 8-250 g/L, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) Sodium chloride corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Sodium citrate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium cyanide, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium dichromate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium fluoride corroding titanium . . . . . . . . . . . . . . . . . . . . . 124 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Sodium hydrosulfide + sodium sulfide and polysulfides corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) Sodium hydroxide . . . . . . . . . . . . . . . . . . . . . . 125 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) Sodium hyperoxide, titanium alloy corrosion rate . . . . . . . . . . . . . . . . . . . . 312(T) Sodium hypochlorite corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) Sodium hypochlorite + sodium chloride +sodium hydroxide, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium nitrate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium perchlorate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium phosphate, corrosion rate of commercially puretitanium. . . . . . . . . 310(T) Sodium silicate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium sulfate corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Sodium sulfide, corrosion rate of commercially pure titanium . . . . . . . . 310(T)

Sodium sulfite, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium thiosulfate, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sodium thiosulfate + acetic acid, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 310(T) Soils, corrosive corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) Solidification, definition . . . . . . . . . . . . . . . . . 341 Solidification cracking. . . . . . . . . . . . . . . . 68, 69 Solidification range, definition . . . . . . . . . . . 341 Solidification segregation . . . . . . . . . . . . . 68–69 Solidification shrinkage, definition . . . . . . . 341 Solidification shrinkage crack, definition . 341 Solid solution, definition. . . . . . . . . . . . . . . . . 341 Solid shrinkage, definition . . . . . . . . . . . . . . . 341 Solid-solution strengthening (SSS). . . . 96, 100 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Solid-state spray forming (SSF) . . . . . . . . . 134 Solid-state welding . . . . . . . . . . . . . 65, 76–77(F) Solidus. See also Liquidus. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Solidus/liquidus, of titanium. . . . . . . . . . . . . 5(T) Solute, definition. . . . . . . . . . . . . . . . . . . . . . . . 341 Solute-lean, hcp, martensite, symbols . . 331(T) Solute-lean β-phase, symbols . . . . . . . . . 331(T) Solute-rich, orthorhombic, martensite, symbols . . . . . . . . . . . . . . . . . . . . . . . . . 331(T) Solute-rich β-phase, symbols. . . . . . . . . . 331(T) Solution abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Solution annealed, abbreviation . . . . . . . 143(T) Solution annealing (treatment) . . . 58–60(F,T) Solution heat treated, abbreviation. . . . . 143(T) Solution heat treatment (ST). . . . . . . . . . 18, 57, 58–60(F, T) before welding. . . . . . . . . . . . . . . . . . . . . . . . . . 65 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 of forgings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Solution heat treatment and overaging. See also Multiple aging. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Solution treat and age, heat treating cycle and resulting microstructure. . . . 55(T) Solution treated, abbreviation . . . . . . . . . 143(T) Solution treated and aged (stabiliziation) . . . . . . . . . . . 55, 58–61(F, T) abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) Solution treated and overaged (STOA) . . . . 61 abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) Solution treating . . . . . . . . . . . . . . . . . . . . . . . . 56 alpha-beta alloys . . . . . . . . . . . . . . . . . . . . . . . . 20 Spaghetti alpha . . . . . . . . . . . . . 34, 35(T), 36(F) Spalling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Spanish equivalent designations . . . . . . 285(T) Spatter, definition . . . . . . . . . . . . . . . . . . . . . . 341 Specials total, abbreviation . . . . . . . . . . . . 143(T) Specification and standardization organizations in the United States addressses, contact information, and descriptions . . . . . . . . . . . . . . 289–290(T) Specification and standardization organizations outside the United States addresses, contact information, and descriptions . . . . . . . . . . . . . . . . . 291–294(T) Specifications, consolidation trend . . . . . . . . 136 Specific gravity, of titanium . . . . . . . . . . . . . 5(T) Specific heat (at 25 °C), of titanium . . . . . . 5(T) SPF/DB, definition . . . . . . . . . . . . . . . . . . . . . . 341 Spinning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Splat, definition. . . . . . . . . . . . . . . . . . . . . . . . . 341 Sponge definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

manufacturers and suppliers . . . . . . . . . . 306(T) Sponge fines . . . . . . . . . . . . . . . . . . . . . . . . . 48, 49 Sponge titanium powder. See also Kroll process. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Sporting goods applications . . . . . . . . . . . 7, 10, 11(T), 39, 42, 43 Spot welding . . . . . . . . . . . . . . . . . . . . . . 67(F), 71 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Spray forming . . . . . . . . . . . . . . . . . . . . . 134–135 cast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 near-net shape processing . . . . . . . . . . . . . . . 134 oxygen effect . . . . . . . . . . . . . . . . . . . . . . . . . . 134 Springback. . . . . . . . . . . . . . . . . . . . . 36, 152, 153 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 and machining . . . . . . . . . . . . . . . . . . . . . . . . . . 80 minimized by hot forming . . . . . . . . . . . . . . . . 37 prevention during annealing processes . . . . . 58 weights per various sizes . . . . . . . . . . . . . 328(T) ST. See Solution heat treatment. STA, definition . . . . . . . . . . . . . . . . . . . . . . . . . 341 Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 alpha-beta alloys . . . . . . . . . . . . . . . . . . . . . . . 101 Stabilized, abbreviation . . . . . . . . . . . . . . . 143(T) Stabilizing . . . . . . . . . . . . . . . . . . . . . . 58–61(F,T) Stainless steels corrosion resistance. . . . . . . . . . . . . . . . . . 123(F) machinability rating . . . . . . . . . . . . . . . . . . 79(T) Stannic chloride, corrosion rate of commercially pure titanium . . . . . . . . 310(T) molten, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 310(T) Std, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 341 STDA, definition. . . . . . . . . . . . . . . . . . . . . . . . 342 Steady-state solidification, not possible in vacuum arc remelting . . . . . . . . . . . . . . . 27 Steam + air, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Steam + hydrogen sulfide, corrosion rate of commercially pure titanium . . . . . . 310(T) Stearic acid, molten, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Steels drilling, unit power requirments . . . . . . . . 80(T) flow stress . . . . . . . . . . . . . . . . . . . . . . . . . . . 34(F) forging temperature effect on forging pressure . . . . . . . . . . . . . . . . . . . . . . . . . . 34(F) mechanical properties. . . . . . . . . . . . . . . . . 95(T) milling unit power requirements . . . . . . . . 80(T) physical properties . . . . . . . . . . . . . . . . . . . 95(T) strength-to-density value . . . . . . . . . . . . . . 95(T) stress-strain curve . . . . . . . . . . . . . . . . . . . . 99(F) turning, unit power requirements . . . . . . . 80(T) STOA. See Solution heat treatment and overaging. Stopoff, definition. . . . . . . . . . . . . . . . . . . . . . . 341 STQ, definition . . . . . . . . . . . . . . . . . . . . . . . . . 341 Strain, definition. . . . . . . . . . . . . . . . . . . . . . . . 341 Strain, % deformation, symbols. . . . . . . 331(T) Strain-age embrittlement, definition. . . . . . 341 Strain hardening, definition . . . . . . . . . . . . . 341 Strain rate, definition . . . . . . . . . . . . . . . . . . . 342 Stress definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . 331(T) Stress at 0.01% strain; the proportional limit, σ0.2 symbols . . . . . . . . . . . . . . . . 331(T) Stress at 0.2% strain; the “0.2%-offset” yield stress, symbols . . . . . . . . . . . . . . 331(T) Stress-corrosion cracking (SCC) . . . . . . . . . 18, 128–130(F,T) by chlorides . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 chemistry and processing. . . . . . . . . . . . . . . . 129 definition . . . . . . . . . . . . . . . . . . . . . . . . . 128, 342 environments and temperature conducive to . . . . . . . . . . . . . . . . . . . . . 129(T)

© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

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364 / Subject Index Stress-corrosion cracking (SCC) (continued) from vapor degreasing solvents . . . . . . . . . . . 91 hot-salt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 mechanism of . . . . . . . . . . . . . . . . . . . . . . . . . 129 Stress-intensity factor (KI), definition. . . . . 342 Stress-intensity factor range during a fatigue cycle (∆K), definition . . . . . . . . 342 Stress raiser . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Stress-relief annealing. See Stress relief heat treatment. Stress relief cracking, definition. . . . . . . . . . 342 Stress relief heat treatment. . . . . . . . . . . 18, 55, 56–57(F, T) after welding . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 of castings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 for weld repaired castings . . . . . . . . . . . . . . . . 41 of diffusion welds . . . . . . . . . . . . . . . . . . . . . . . 73 temperature and time duration. . . . . . . . . . 37(T) of weldments . . . . . . . . . . . . . . . . . . . . . . . . 57, 65 Stress relieved, abbreviation. . . . . . . . . . . 143(T) Stress relieving, definition . . . . . . . . . . . . . . . 342 Stress rupture . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Stress-rupture test, definition . . . . . . . . . . . . 342 Striation, definition . . . . . . . . . . . . . . . . . . . . . 342 Stringers. . . . . . . . . . . . . . . . . . . . . . . . . . 39, 30(F) Strip abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) manufacturers and suppliers . . . . . . . . . . 306(T) Subsolidus (ductility dip) cracking . . . . . . . . 68 Substitutional alloying elements . . . . . . . . . . 16 Substitutional solid-solution strengthening . . . . . . . . . . . . . . . . . . . . . . . 96 Substrate, definition . . . . . . . . . . . . . . . . . . . . 342 Subsurface corrosion, definition . . . . . . . . . 342 Subzero temperature, effect on mechanical properties and microstructure . . . . . . . . . . . . . 117–121(F,T) Succinic acid, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sulfamic acid corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 310(T) titanium alloy corrosion rate . . . . . . . . . . 312(T) Sulfamic acid + ferric chloride, corrosion rate of commercially pure titanium . . . 310(T) Sulfanilic acid, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sulfur, alloying addition and corrosion. . . . . 126 Sulfur-molten, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sulfur dioxide, dry, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sulfur dioxide, water saturated, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 310(T) Sulfur dioxide gas + SO3 and 3% O2, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 310(T) Sulfur monochloride, corrosion rate of commercially pure titanium . . . . . . 310(T) Sulfuric acid, aerated, corrosion rate of commercially pure titanium . . . . . . . . 310(T) aerated, titanium alloy corrosion rate . . 312(T) and titanium corrosion resistance . . . . 125, 126 chlorine saturated, titanium alloy corrosion rate . . . . . . . . . . . . . . . . . . . . 312(T) corroding titanium . . . . . . . . . . . . . . . . . . . . . 123 naturally aerated, titanium alloy corrosion rate . . . . . . . . . . . . . . . . . . . . 312(T) nitrogen saturated, titanium alloy corrosion rate . . . . . . . . . . . . . . . . . . . . 312(T) oxygen saturated, titanium ally corrosion rate . . . . . . . . . . . . . . . . . . . . 312(T) saturated with chlorine, corrosion rate of commercially pure titanium . . . . . . . . 311(T)

Sulfuric acid + chlorine ions, titanium alloy corrosion rate. . . . . . . . . . . . . . . . 312(T) Sulfuric acid + chromium oxide, corrosion rate of commercially pure titanium . . . . . . 310(T) Sulfuric acid + copper ions + 1% thiourea (deaerated), titanium alloy corrosion rate . . . . . . . . . . . . . . . . . . . . 312(T) Sulfuric acid + CuSO4, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Sulfuric acid + 15% CuSO4, titanium alloy corrosion rate. . . . . . . . . . . . . . . . 312(T) Sulfuric acid + ferric chloride, titanium alloy corrosion rate. . . . . . . . . . . . . . . . 312(T) Sulfuric acid + ferric sulfate, titanium alloy corrosion rate Sulfuric acid + ferric sulfate, and titanium corrosion resistance . . . . . . . . . . . . . 125, 126 titanium alloy corrosion rate . . . . . . . . . . 312(T) Sulfuric acid + nitric acid, corrosion rate of commercially pure titanium . . . 310–311(T) Sulfuric acid + 4 g/L Ti4+, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Sulfuric acid vapors, corrosion rate of commercially pure titanium . . . . . . . . 310(T) Sulfurous acid, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Sumitomo equivalent designations . . . . 285(T) Superalpha, definition . . . . . . . . . . . . . . . . . . 342 Superalpha alloys . . . . . . . . . . . . . . . . . . . . 14, 16 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 heat treating . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 mechanical properties . . . . . . . . . . . . . . . . . . 135 precipitation hardening . . . . . . . . . . . . . . . . . . 21 Superplastic forging . . . . . . . . . . . . . . . . . . . . . 30 Superplastic forming . . . . . . . . . . . . . . 3, 50, 76, 77(F), 131 with diffusion bonding . . . . . . . . . . . . . . . . . . . 76 Superplastic forming/diffusion bonding (SPFDB). . . . . . . . . . . . . 77(F), 134 aircraft applications . . . . . . . . . . . . . . . . . . . . 134 cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 Superplastic forming/forging . . . . . . . . . . . . . . 9 Superplasticity . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Suppliers addresses, contact information, and products or services described . . 298–304(T) by primary titanium product or service line . . . . . . . . . . . . . . . . . . . . . . . . . 304–306(T) Surface cracks . . . . . . . . . . . . . . . . . . . . . . . 18–19 Surface finishes . . . . . . . . . . . . . . . . . . . . . . . . . 85 Surface grinding . . . . . . . . . . . . . . . . . . . 321–322 fire hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 Surface hardening, definition . . . . . . . . . . . . 342 Surface rolling . . . . . . . . . . . . . . . . . . . . . . . . . 108 Surface scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Surface stability, definition . . . . . . . . . . . . . . 342 Surface treatments, of precious metals . . . . 128 Surgical, abbreviation . . . . . . . . . . . . . . . . 143(T) Surveillance and guidance systems . . . . . . . . . 8 Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331(T)

T TA. See Multiple annealing. Tack welding . . . . . . . . . . . . . . . . . . . . . . . . 74, 75 Tannic acid, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Tantalum as alloying addition and corrosion . . . . . . . . 126 corrosion resistance. . . . . . . . . . . . . . . . . . 123(F) in beta isomorphous group . . . . . . . . . . . . 15, 16 Tapping . . . . . . . . . . . . . . . . . . . . . . . . 318, 320(T)

speeds and feeds . . . . . . . . . . . . . . . . . . . . 320(T) tool materials . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Tarnish films, removal of . . . . . . . . . . . . . . . . . 89 Tartaric acid, corrosion rate of commercially pure titanium . . . . . . . . 311(T) TCP, definition . . . . . . . . . . . . . . . . . . . . . . . . . 342 TCR, definition . . . . . . . . . . . . . . . . . . . . . . . . . 342 TD. See Transverse direction. Tee-Nee. See the Alloy Index for this entry. Teledyne AllVac equivalent designations . . . . . . . . . . . . . . . . . . . . . 288(T) Teledyne equivalent designations . . . . . 288(T) Teledyne Rodney equivalent designations . . . . . . . . . . . . . . . . . . . . . 288(T) Temper, definition . . . . . . . . . . . . . . . . . . . . . . 342 Temperature coefficient of electrical resistance, of titanium. . . . . . . . . . . . . . . 5(T) Tempered, abbreviation . . . . . . . . . . . . . . 143(T) Temporary bag . . . . . . . . . . . . . . . . . . . . . . . . . 65 10–6 m, symbols. . . . . . . . . . . . . . . . . . . . . . 331(T) Tensile strength . . . . . . . . . . . . . . . . . . . . . . . . . . 1 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 P/M compacts. . . . . . . . . . . . . . . . . . 52(F), 53(T) of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5(T) Tensile yield strength (TYS), and fatigue . . 105 Tension, definition . . . . . . . . . . . . . . . . . . . . . . 342 Tension testing, definition . . . . . . . . . . . . . . . 342 Terephthalic acid, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Tetrachloroethane, liquid and vapor, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 311(T) Tetrachloroethylene corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 311(T) liquid and vapor, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Tetrachloroethylene + water, corrosion rate of commercially pure titanium . . . 311(T) Texture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 Texturization parameter in magnetic texture measurement, symbols . . . . 331(T) Theoretical density . . . . . . . . . . . . . . . . . . . . . 114 Thermal conductivity, of titanium . . . . . . . 5(T) Thermal cutting. . . . . . . . . . . . . . . . . . . . . . . . 325 Thermal diffusion . . . . . . . . . . . . . . . . . . . . . . 126 Thermal expansion coefficient, and optic-system support structures . . . . . . . . . . 8 Thermal fatigue . . . . . . . . . . . . . . . . . . . . . . . . 105 Thermal neutron absorption cross section, of titanium. . . . . . . . . . . . . . . . . . 5(T) Thermal oxidation . . . . . . . . . . . . . . . . . 127, 128 Thermal spray . . . . . . . . . . . . . . . . . . . . . . . . . 134 Thermomechanical treatment (TCT), heat treatment method for modifying microstructure and properties of net shape products . . . . . . . . . . . . . . . . . 42(T) Thermocouple, to monitor stress relief heat treatment . . . . . . . . . . . . . . . . . . . . . . . . 56 Thermomechanical processing (TMP) . . . . . . . . . . . . . . . . . 204, 205, 208(T), 209(T), 218, 223 effect on fatigue . . . . . . . . . . . . . . . . . . . . . 108(F) for Beta C . . . . . . . . . . . . . . . . . . . . . . . . . . 247(T) for Timetal 21S . . . . . . . . . . . . . . . . . . . . . . . . 264 for Ti-6-22-22S . . . . . . . . . . . . . . . . . . . . . 237(T) for titanium aluminides. . . . . . . . . . . . . . . 132(F) for Ti-10V-2Fe-3AL . . . . . . . . 102, 248, 251(T) to modify surface microstructure . . . . . . . . . 108 to provide desired fracture toughness . . . . . . . . . . . . . . . . . 103–105(F,T) Thickness, abbreviation. . . . . . . . . . . . . . . 143(T) Thomas Register (Products & Services volume, titanium entry) . . . . . . . . . . . . . 295

© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

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Subject Index / 365 Threshold stress-intensity factor for stress-corrosion cracking (KISCC), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 “Through the transus” processing, of Beta-CEZ . . . . . . . . . . . . . . . . . . . . . . . . 266 Thyssen Contimet equivalent designations . . . . . . . . . . . . . . . . . . . . . 284(T) Thyssen LT equivalent designations. . . 284(T) Titanium aluminides, applications. . . . . . . . 132 Tickle, definition. . . . . . . . . . . . . . . . . . . . . . . . 342 Tiduran process . . . . . . . . . . . . . . . . . . . . . . . . . 93 Time-temperature transformation (TTT) diagrams . . . . . . . . . . . . . . . 23, 24(F) for IMI 679 . . . . . . . . . . . . . . . . . . . . . . . . . 188(F) for Ti-5Al-2.5Fe (Tikrutan LT 35) . . . . . 237(F) for Ti-6Al-4V. . . . . . . . . . . . . . . . . . . . . . . 211(F) for Ti-10V-2Fe-3Al . . . . . . . . . . . . . . . . . 252(F) for Ti-13V-11Cr-3Al . . . . . . . . . . . . . . . . 256(F) TIMET equivalent designations . . . . . . 288(T) Tin alloying additions and corrosion. . . . . . . . . . 129 alloying element effect on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15(T) as alpha and beta strengthener . . . . . . . . . 15, 16 range as alloying element for titanium . . . 15(T) Tinel. See the Alloy Index for this entry. Titanium as allotropic element. . . . . . . . . . . . . . . . . . . . . 13 applications. . . . . . . . . . . . . . . . . . . . . . . . . . . 7(F) biocompatibility . . . . . . . . . . . . . . . . . . . . . . . . . 5 body-centered cubic . . . . . . . . . . . . . . . . . . . . . 16 content (%) of some recent military airframes . . . . . . . . . . . . . . . . . . . . . . . . . 47(T) corrosion resistance . . . . . . . . . . . . . . . . . . . . 5, 7 crystal structures . . . . . . . . . . . . . . . . . . . . . . 2(F) development. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 melting point . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 microstructures. . . . . . . . . . . . . . . . . 14(F), 15(F) mineral sources . . . . . . . . . . . . . . . . . . . . . . . . . . 3 passivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 physical properties . . . . . . . . . . . . . . . . . . . . . . . 1 position in galvanic series in seawater. . . 126(T) producers (countries) . . . . . . . . . . . . . . . . . . . . . 3 product forms . . . . . . . . . . . . . . . . . . . . . . . 5, 6(F) properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 selection for service . . . . . . . . . . . . . . . 5–8(F, T) Titanium alloys abbreviations used in Table F.2. . . . . . . . 312(T) advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 aerospace applications . . . . . . . . . 3, 8, 9, 11(T), 42, 43(F), 52, 72 aerospace applications blazed components . . . . . . . . . . . . . 76, 78(F) castings for. . . . . . . . . . . . . . . . . . . . 39, 41(F) machined parts . . . . . . . . . . . . . . . . . . . . . . 81 P/M parts. . . . . . . . . . . . . 49(F), 50(F), 51(F) aircraft applications. . . . . . . . . 1(F), 9–11(F, T), 31, 39(F), 42, 43(F), 51(F), 52(T), 76(F) bonded and brazed components . . 76–77(F), 78(F) gold-coated titanium . . . . . . . . . . . . . . . . . 92 machined parts . . . . . . . . . . . . . . . . 81, 82(T) alloying elements effect on sponge purity. . . . 25 alloying elements effects. . . . . . . . . 14–16(F, T) alloying tendency . . . . . . . . . . . . . . . . . . . . . . . 80 applications. . . . . . . . . . . . . . . . . . . . . . . . . . . 7(F) architectural applications . . . . . . . . . . . . . . 11(T) automotive applications . . . . . . . . . . . . 9, 11(T), 42–43, 52, 136 biomedical applications . . . . . 11(T), 42–43, 90 cast-plus-HIP materials, mechanical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 chemical-process applications . . . . . . . . . 42, 52 chemical processing industries applications. . . . . . . . . . . . . . . . . . . . 10, 11(T)

commercial availability . . . . . . . . . . . . . . . . . . . 7 composition. . . . . . . . . . . . . . . . . . . . . . . . . 19(T), 20(T), 21(T) corrosion rates by various media, concentrations, and temperatures. . . . . . . . . . . . . . . . . 311–312(T) corrosion resistance . . . . . . . . . . . . . . . . . . 5, 7, 9 cryogenic applications . . . . . . . . . . . . . . . . . . . . 9 cutting resistance . . . . . . . . . . . . . . . . . . . . . 79(F) design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 drilling, unit power requirements . . . . . . . 80(T) fashion and apparel industries applications . . . . . . . . . . . . . . . . . . . . . . . 11(T) fatigue. . . . . . . . . . . . . . . . . . . . . . . . . 105–107(F) formability . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3, 9 groups. . . . . . . . . . . . . . . . . . . . . . . . . 17–21(F, T) growth potential . . . . . . . . . . . . . . . . . . . . . . . 137 guidance systems and electronics applications . . . . . . . . . . . . . . . . . . . . . . . . . . 90 hardenability . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 heat treatment . . . . . . . . . . . . . . . . . . . . . 7, 10, 11 higher-temperature . . . . . . . . . . . . . . . . 135–136 hot salt cracking susceptibility . . . . . . . . . . . 129 hydrogen damage . . . . . . . . . . . . . . . . . . . . . . 128 industrial applications. . . . . . . . . . . . . . . . . . . . . 9 lower-cost. . . . . . . . . . . . . . . . . . . . . . . . . . 136(T) manufacture of. . . . . . . . . . . . . . . . . . . . . . . . . . 25 marine applications . . . . . . . . . . . . . . . . . . . 9, 10, 11(T), 42, 136 marine applications, castings for . . . . . . . . . . 39 mechanical properties . . . . . . . . . . . 1, 7, 8, 9, 80 mechanical properties, factors affecting. . . . . . . . . . . . . . . . . . . . . . . 95–96(F) microstructural development . . . . . 21–24(F, T) microstructural ranges . . . . . . . . . . . . . . . . 17(F) milling, unit power requirements . . . . . . . 80(T) miscellaneous applications . . . . . . . . . . . . 11(T) nonburning, development of . . . . . . . . . . 136(F) oil, gas, and petroleum processing applications . . . . . . . . . . . . . . . . . . . . . . . 11(T) oxidation resistance . . . . . . . . . . . . . . . . . . 2, 123 particulate-reinforced applications . . . . . . . . . . . . . . . . . . . . . 141(T) description . . . . . . . . . . . . . . . . . . . . . . 141(T) petroleum industry applications . . . . . . . . 42–43 phase diagrams . . . . . . . . . . . . . 13–14(F), 15(F) physical properties . . . . . . . . . . . . . . . . . . . . 2, 95 power generation applications. . . . . . . . . . 11(T) processing . . . . . . . . . . . . . . . . . . . . . . . . . . 10–11 processing requirements. . . . . . . . . . . . . . . . . . . 7 product forms . . . . . . . . . . . . . . . . . . . . . . . 5, 6(F) properties . . . . . . . . . . . . . . . . . . . . . . . . 18, 22(F) rotor-grade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 selection for service . . . . . . . . . . . . . . . 5–8(F, T) sporting goods applications . . . . . . . . . . . . 7, 10, 11(T), 39, 42, 43 strength-to-density valves . . . . . . . . . . . . . 95(T) surface damage susceptibility during machining . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 systems availability. . . . . . . . . . . . . . . . . . . . . . . 9 temperature limit. . . . . . . . . . . . . . . . . . . . . . . 131 turning, unit power requirements . . . . . . . 80(T) weight per gage . . . . . . . . . . . . . . . . . . . . . 327(T) workability. . . . . . . . . . . . . . . . . . . . . . . . . . . 8, 11 work hardening characteristics . . . . . . . . . . . . 80 Titanium alloys, specific type aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59(T) solution treating . . . . . . . . . . . . . . . . . . . . . . 59(T) Titanium aluminides . . . . . . . . . 16, 131–133(F) aluminizing . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 and annealing. . . . . . . . . . . . . . . . . . . . . . . . . . . 58 coatings for . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 compositions. . . . . . . . . . . . . . . . . . . . . . 131–132 cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

development spurred by military requirements . . . . . . . . . . . . . . . . . . . . . . . . 131 elastic modulus . . . . . . . . . . . . . . . . . . . . . . . . 132 formability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 forming TiO2 . . . . . . . . . . . . . . . . . . . . . . . . . 132 mechanical properties. . . . . . . . . . . . . . 3, 132(F) limitations . . . . . . . . . . . . . . . . . . . . . . . . . 133 Metal-chromium-aluminum-yttrium overlay coatings . . . . . . . . . . . . . . . . . . . . . 132 oxidation resistance . . . . . . . . . . . . . . . . . . . . 132 processing methods . . . . . . . . . . . . . . . . . . . . 132 properties. . . . . . . . . . . . . . . . . . . . . . . . . 131–132 service temperatures. . . . . . . . . . . . . . . . . . . . 132 silicides/ceramics . . . . . . . . . . . . . . . . . . . . . . 132 temperature range for applications . . . . . . . . . . 5 temperature range of useful strengths . . . . . . . 1 Titanium aluminide (Ti-Al) alloys single phase (γ) alloys applications . . . . . . . . . . . . . . . . . . . . . 141(T) description . . . . . . . . . . . . . . . . . . . . . . 141(T) two-phase (γ + α – 2) alloys applications . . . . . . . . . . . . . . . . . . . . . 141(T) description . . . . . . . . . . . . . . . . . . . . . . 141(T) Titanium aluminide (Ti3-Al) alloys applications . . . . . . . . . . . . . . . . . . . . . . . . 141(T) description . . . . . . . . . . . . . . . . . . . . . . . . . 141(T) Titanium fines . . . . . . . . . . . . . . . . . . . . . . . 81–82 as fire hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Titanium flat bar, weight at width per various thicknesses . . . . . . . . . . . . 327(T) Titanium hydride formation predicted under strongly reducing, or cathodic, reactions . . . 125, 126 surface films . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Titanium Information Group, Associates of . . . . . . . . . . . . . . . . 296–298(T) Titanium ion hydrolysis. . . . . . . . . . . . . . . . . 125 Titanium matrix composites (TMC). . . . . . . . . . . . . . . . . . . . . . 133–134(F) aircraft applications . . . . . . . . . . . . . . . . . . . . 133 cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 defects in microstructure . . . . . . . . . . . . . . . . 134 deposition methods for titanium matrix onto fibers . . . . . . . . . . . . . . . . . . . . . . . . . . 134 development spurred by military requirements . . . . . . . . . . . . . . . . . . . . . . . . 131 future of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 matrix materials . . . . . . . . . . . . . . . . . . . . . . . 133 mechanical properties . . . . . . . . . . . . . . 133, 134 particulate-reinforced, mechanical properties. . . . . . . . . . . . . . . . . . . . . . . . . . . 134 particulate-reinforced, produced by P/M processing . . . . . . . . . . . . . . . . . . . . . . . . . . 134 physical properties . . . . . . . . . . . . . . . . . . . . . 134 processing options . . . . . . . . . . . . . . . . . . . . . 134 reinforcement materials . . . . . . . . . . . . . . . . . 133 Titanium-nickel shape memory alloys . . 11(T) applications . . . . . . . . . . . . . . . . . . . . . . . . . 11(T) description . . . . . . . . . . . . . . . . . . . . . . . . . 141(T) Titanium nitride, as crack initiation site . . . . 25 Titanium oxide, as crack initiation site. . . . . . 25 Titanium oxynitride, as crack initiation site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Titanium production standards unalloyed titanium (ASTM B 265). . . . . . . . . . 7 unalloyed titanium (ASTM B 338). . . . . . . . . . 7 unalloyed titanium (ASTM B 367). . . . . . . . . . 7 Titanium-silicon phase diagram . . . . . . 187(F) Titanium sludge . . . . . . . . . . . . . . . . . . . . . . . . . 83 Titanium sponge . . . . . . . . . . . . . . . . . . 25, 27(F) impurities in . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 melting to form an ingot. . . . . . . . . . . . . . . . . . 25 melted to form an ingot with revert and alloy additions . . . . . . . . . . . . . . . . . . . . 28 production . . . . . . . . . . . . . . . . . . . . . . . . . . . 3, 25 purification of . . . . . . . . . . . . . . . . . . . . . . . . . . 25

© 2000 ASM International. All Rights Reserved. Titanium: A Technical Guide, 2nd Edition (#06112G)

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366 / Subject Index Titanium sponge (continued) purity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 specifications relative to chemistry and inclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Titanium tetrachloride. . . . . . . . . . . . . . . . . . . 25 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 311(T) Titanium trade (information) associations . . . . . . . . . . . . . . . . . . . . . 295(T) Titanium-water system, Pourbaix diagram for . . . . . . . . . . . . . . . . . . . . . . 125(F) Titan RT equivalent designations . . . . . 284(T) Titrametric analysis, to control pickling bath acidity . . . . . . . . . . . . . . . . . . . . . . . . . . 91 TMCA equivalent designations . . . . . . . 288(T) Toho equivalent designations . . . . . . . . . 285(T) Toll melting, definition . . . . . . . . . . . . . . . . . . 342 Torch brazing. . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Trade (information) associations. . . . . . 295(T) Transformation products, beta-phase. . . . . . 96 Transformations. . . . . . . . . . . . . . . . . . 16–17(F), 21–24(F) Transformation temperature, definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Transformed beta . . . . . . . . 15(F), 16–17(F), 68 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Transverse direction (TD), definition . . . . . 342 Transverse solute banding . . . . . . . . . 68, 69(F) Trichloroacetic acid, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Trichloroethylene . . . . . . . . . . . . . . . . . . . . . . . 70 corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 311(T) environment and temperature conducive to SCC of Ti alloys. . . . . . . . . . . . . . . . 129(T) Trichloroethylene water, corrosion rate of commercially pure titanium . . . . . . 311(T) Trichlorofluoroethane, environment and temperature conducive to SCC of Ti alloys. . . . . . . . . . . . . . . . . . . . . . . 129(T) Triplex annealed, abbreviation . . . . . . . . 143(T) Triplex annealing. See also Multiple annealing. . . . . . . . . . . . . . . . . . 57–58, 112(T) TS. See Tensile strength. Tube abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) weight by outside diameter and wall thickness . . . . . . . . . . . . . . . . . . . . . . . . 330(T) Tube, tubing, manufacturers and suppliers. . . . . . . . . . . . . . . . . . . . . . . . . 306(T) Tungsten, as alloying addition and corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Turning . . . . . . . . . . . . . . . . . . . . . . 83(F), 315(T) power requirements. . . . . . . . . . . . . . . . . . . 80(T) single-point and box tool speeds and feeds . . . . . . . . . . . . . . . . . . . . 315–316(T) speeds and feeds . . . . . . . . . . . . . . . . . . 81, 82(T) tool materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Type I imperfections. . . . . . . . . . . . . . . . . . . . . 29 Type II imperfections . . . . . . . . . . . . . . 29, 30(F)

U Ultimate strength definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 unalloyed titanium. . . . . . . . . . . . . . . . . . . . 18(T) Ultimate tensile strength (UTS) . . . . . . . . . . . . 1 abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) of commercially pure titanium. . . . . . . . . . 99(F) and fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 in weldments . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 P/M compacts. . . . . . . . . . . . . . . . . . . . . . . . 52(F) of unalloyed titanium . . . . . . . . . . . . . . . . . 99(F)

Ultrasonic welding (USW) . . . . . . . . . . . . . . . 76 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Unalloyed titanium. See the Alloy Index for this entry. UNE equivalent designations . . . . . . . . . 285(T) Unidirectional rolling . . . . . . . . . . . . . . . . . 32(T) Unit cell, definition. . . . . . . . . . . . . . . . . . . . . . 342 United States equivalent designations . . . 286(T) UNS, definition . . . . . . . . . . . . . . . . . . . . . . . . . 342 Upset, definition . . . . . . . . . . . . . . . . . . . . . . . . 342 Upset forging, definition. . . . . . . . . . . . . . . . . 342 Upsetting, definition . . . . . . . . . . . . . . . . . . . . 343 Upset weld, definition . . . . . . . . . . . . . . . . . . . 343 Upset welding (UW), definition . . . . . . . . . . 343 Uranium chloride, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Uranyl ammonium phosphate filtrate + chloride + fluoride + ammonia + uranium, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Uranyl nitrate containing chromium ions, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 311(T) Uranyl nitrate containing ferric ions, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 311(T) Uranyl nitrate containing nickel ions, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . . . . . 311(T) Uranyl nitrate containing nitric acid and chlorine, corrosion rate of commercially pure titanium . . . . . . . . 311(T) Uranyl sulfate + lithium sulfate, corrosion rate of commercially pure titanium . . 311(T) Uranyl sulfate + lithium sulfate + oxygen gas, corrosion rate of commercially pure titanium . . . . . . . . . . . . . . . . . . . . . 311(T) Uranyl sulfate + oxygen, corrosion rate of commercially pure titanium . . . . . . 311(T) USW. See Ultrasonic welding. UW. See Upset welding.

V Vacuum annealing to get rid of hydrogen pickup. . . . . . . . . . . . . . 63 to remove hydrogen from commercially pure titanium. . . . . . . . . . . . . . . . . . . . . . . . . 97 Vacuum arc remelted (VAR) sponge consolidation process . . . . . . . . . . . . . . . . 48 Vacuum arc remelting (VAR). . . . . . . . . . 27(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Vacuum degassing. . . . . . . . . . . . . . . . . . . . . . . 88 Vacuum distilling . . . . . . . . . . . . . . . . . . . . . . . 25 Vacuum hot pressing (VHP) . . . . 49, 50, 51, 52 of titanium matrix composites . . . . . . . . . . . 134 Vacuum induction melting (VIM), definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Vacuum melting, definition . . . . . . . . . . . . . . 343 Vanadium as alloying addition and corrosion . . . . 126, 129 alloying element effect on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15(T) as beta-stabilizing element . . . . . . . . . . . . . . 2(F) in beta isomorphous group . . . . . . . . . . . . 15, 16 range as alloying element for titanium . . . 15(T) Vanadium ion (V5+), inhibiting titanium corrosion in boiling reducing acids . . 124(T) Vapor degreasing . . . . . . . . . . . . . . . . . . . . . . . 91 VAR. See Vacuum arc remelting. Vessel, abbreviation . . . . . . . . . . . . . . . . . . 143(T) VHP, definition . . . . . . . . . . . . . . . . . . . . . . . . . 343

Vickers hardness number (HV), definition . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Vickers hardness test, definition . . . . . . . . . 343 VIM. See Vacuum induction melting.

W Water, effect from atmosphere on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . 61 Water elutriation . . . . . . . . . . . . . . . . . . . . . . . . 49 Weights . . . . . . . . . . . . . . . . . . . . . . . . 327–330(T) Weldability . . . . . . . . . . . . . . . . . . 2, 9, 18, 65–66 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Welded, abbreviation . . . . . . . . . . . . . . . . . 143(T) Weld fusion zone . . . . . . . . . . . . 66–67(F), 68(F) Welding. See also Electron beam welding; Fusion welding; Gas-metal arc welding; Gas-tungsten arc welding; Laser beam welding; Plasma arc welding; Resistance seam welding; Resistance spot welding: Resistance welding; Weld repair. . . . . . 1, 65 abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) aerospace applications . . . . . . . . . . . . . . . . . . . 71 alpha alloys . . . . . . . . . . . . . . . . . . . . . . . . . 65, 73 alpha-beta alloys . . . . . . . . . . . . 65–67(F), 69(F) beta alloys. . . . . . . . . . . . . . . . . . . . . . . . 66, 69(F) defects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 filler metals used . . . . . . . . . . . . . . . . . . . . . . . . 66 metastable beta alloys. . . . . . . . . . . . . . 68, 69(F) near-alpha alloys. . . . . . . . . . . . . . . . . . . . . 65, 69 out-of-chamber . . . . . . . . . . . . . . . . . . . . . . 73(F) precautions in practice . . . . . . . . . . . . . . . . . . . 70 residual stresses. . . . . . . . . . . . . . . . . . . . . . . . . 71 shielding of weld zone . . . . . . . . . . . . . . . . . . . 70 specifications . . . . . . . . . . . . . . . . . . . . . . . 69–70 temperature range . . . . . . . . . . . . . . . . . . . . . . . 65 Weldments aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66, 68(F) corrosion resistance . . . . . . . . . . . . . . . . . . . . 124 defects. . . . . . . . . . . . . . . . . . . . . . . . . . . 68–69(F) embrittlement. . . . . . . . . . . . . . . . . . . . . . . . . . . 66 fatigue crack propagation . . . . . . . . 109–110(F) fatigue strength at cryogenic temperatures. . . . . . . . . . . . . . . . . 120–121(T) fracture toughness after heat treatment . . . 105(T) fracture toughness at cryogenic temperatures . . . . . . . . . . . . . . . . . . . . . 120(T) mechanical properties . . . . . . . . . . . . . . . . . 68(F) microstructure . . . . . . . . . . . . . . . . . . . . 66–68(F) shielding to prevent hydrogen pickup . . . . . 128 stress relief heat treatments . . . . . . . . . . . . 57, 73 Weld-metal liquation cracking . . . . . . . . . . . 69 Weld repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 after hot isostatic pressing . . . . . . . . . . . . . . . . 41 Weld spatter . . . . . . . . . . . . . . . . . . . . . . . . . 74, 76 Werkstoff-Nr equivalent designations. . . 284(T) Wide belt grinding, to remove scale . . . . . . . . 86 Widmanstätten structure . . . . . . . . . . . . . 16(F), 22(F), 66, 68 commercially pure titanium with interstitial elements present . . . . . . 97, 98(F) definition . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 343 in alpha alloys . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Wire abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) copper-plated titanium . . . . . . . . . . . . . . . . . . . 92 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 manufacturers and suppliers . . . . . . . . . . 306(T) weight per size . . . . . . . . . . . . . . . . . . . . . . 328(T) weight per various sizes . . . . . . . . . . . . . . 328(T) Wire brushing . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Wire drawing . . . . . . . . . . . . . . . . . . . . . . . . 91(T) Work hardening . . . . . . . . . . . . . . . . . . . . . . . . 80

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Subject Index / 367 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 WQ, definition. . . . . . . . . . . . . . . . . . . . . . . . . . 343 Wrought. See also Cast. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Wrought alloys, greatest experience factor . . . 3 Wt, definition . . . . . . . . . . . . . . . . . . . . . . . . . . 343

X X-ray diffraction, to assess stress-relief efficiency by measurement of residual stresses . . . . . . . . . . . . . . . . . . . . . . 57

Y Yield. See also Yield point. definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Yield point, definition . . . . . . . . . . . . . . . . . . . 343 Yield strength . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 abbreviation . . . . . . . . . . . . . . . . . . . . . . . . 143(T) of beta alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 P/M compacts. . . . . . . . . . . . . . . . . . . . . . . . 52(F) unalloyed titanium. . . . . . . . . . . . . . . . . . . . 18(T) Young’s modulus cryogenic temperatures vs. room temperatures . . . . . . . . . . . . . . 118(F), 120(T) of titanium. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5(T)

YS. See Yield strength.

Z Zirconium alloying additions and corrosion . . . . . 126, 129 alloying element effect on titanium alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15(T) as alpha and beta strengthener . . . . . . . . . 15, 16 corrosion resistance. . . . . . . . . . . . . . . . . . 123(F) not strengthener for alpha alloys. . . . . . . . . . . 99 range as alloying element for titanium . . . 15(T)

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