Light Alloys Light Alloys Metallurgy of the Light Metals Fifth Edition Ian Polmear David StJohn Jian-Feng Nie Ma Qian Butterworth-Heinemann is an imprint of Elsevier The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States Copyright © 2017 Ian Polmear, David StJohn, Jian-Feng Nie, Ma Qian. Published by Elsevier Ltd. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. 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British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-08-099431-4 For Information on all Butterworth-Heinemann publications visit our website at https://www.elsevier.com/books-and-journals Publisher: Matthew Deans Acquisition Editor: Christina Gifford Editorial Project Manager: Ana C Glaudia Garcia Production Project Manager: Susan Li Designer: Mark Rogers Typeset by MPS Limited, Chennai, India PREFACE TO THE FIRST EDITION The fact that the light metals aluminium, magnesium and titanium have tradi- tionally been associated with the aerospace industries has tended to obscure their growing importance as general engineering materials. For example, alu- minium is now the second most widely used metal and production during the next two decades is predicted to expand at a rate greater than that for all other structural metals. Titanium, which has a unique combination of properties that have made its alloys vital for gas turbine engines, is now finding many applica- tions in aircraft structures and in the chemical industry. Light alloys have never been the subject of a single book. Moreover, although the general metallurgy of each class of light alloys has been covered in individual texts, the most recent published in English appeared some time ago—aluminium alloys in 1970, magnesium alloys in 1966 and titanium alloys in 1956. Many new developments have occurred in the intervening periods and important new applications are planned, particularly in transportation. Thus it is hoped that the appearance of this first text is timely. In preparing the book I have sought to cover the essential features of the metallurgy of the light alloys. Extraction of each metal is considered briefly in Chapter one, after which the casting characteristics, alloying behaviour, heat treatment, properties, fabrication and major applications are discussed in more detail. I have briefly reviewed the physical metallurgy of aluminium alloys in Chapter two although the general principles also apply to the other metals. Particular attention has been devoted to microstructure/property relationships and the role of individual alloying elements, which provides the central theme. Special features of light alloys and their place in general engineering are high- lighted although it will be appreciated that it has not been possible to pursue more than a few topics in depth. The book has been written primarily for students of metallurgy and engi- neering although I believe it will also serve as a useful guide to both producers and users of light alloys. For this reason, books and articles for further read- ing are listed at the end of each chapter and are augmented by the references included with many of the figures and tables. ix x PREFACE TO THE FIRST EDITION The book was commenced when I was on sabbatical leave at the Joint Department of Metallurgy at the University of Manchester Institute of Science and Technology and University of Manchester, so that thanks are due to Professor K. M. Entwistle and Professor E. Smith for the generous facili- ties placed at my disposal. I am also indebted for assistance given by the Aluminium Development Council of Australia and to many associates who have provided me with advice and information. In this regard, I wish partic- ularly to mention the late Dr E. Emley, formerly of The British Aluminium Company Ltd; Dr C. Hammond, The University of Leeds; Dr M. Jacobs; TI Research Laboratories; Dr D. Driver, Rolls-Royce Ltd; Dr J. King and Mr W. Unsworth, Magnesium Elektron Ltd; Mr R. Duncan, IMI Titanium; Dr D. Stratford, University of Birmingham; Dr C. Bennett, Comalco Australia Ltd; and my colleague Dr B. Parker, Monash University. Acknowledgement is also made to publishers, societies and individuals who have provided figures and diagrams which they have permitted to be reproduced in their original or modified form. Finally I must express my special gratitude to my secretary Miss P. O’Leary and to Mrs J. Colclough of the University of Manchester who typed the man- uscript and many drafts, as well as to Julie Fraser and Robert Alexander of Monash University who carefully produced most of the photographs and diagrams. IJP Melbourne 1980 PREFACE TO THE SECOND EDITION In this second edition, the overall format has been retained although some new sections have been included. For the most part, the revision takes the form of additional material that has arisen through the development of new compo- sitions, processing methods, and applications of light alloys during the last 8 years. Most changes have occurred with aluminium alloys which, because of their widespread use and ease of handling, are often used to model new pro- cesses. Faced with increasing competition from fiber-reinforced plastics, the aluminium industry has developed a new range of lightweight alloys contain- ing lithium. These alloys are discussed in detail because they are expected to be important materials of construction for the next generation of passenger aircraft. More attention is given to the powder metallurgy route for fabricat- ing components made from aluminium and titanium alloys. Treatment of this topic includes an account of techniques of rapid solidification processing which are enabling new ranges of alloys to be produced having properties that are not attainable by conventional ingot metallurgy. Metal–matrix composites based on aluminium are also finding commercial applications because of the unique properties they offer and similar magnesium alloys are being developed. New methods of processing range from methods such as squeeze casting through to advances in superplastic forming. In preparing this new edition, I have again paid particular attention to microstructure/property relationships and to the special features of light alloys that lead to their widespread industrial use. In addition to an expanded text, the number of figures has been increased by some 40% and the lists of books and articles for further reading have been extended. Once more, the book is directed primarily at undergraduate and postgraduate students although I believe it will serve as a useful guide to producers and users of light alloys. I am again indebted for assistance given by colleagues and associates who have provided me with information. Acknowledgment is also made to publish- ers, societies, and individuals who have provided photographs and diagrams which they have permitted to be produced in their original or modified form. xi xii Preface to the Second edition Finally I wish to express my gratitude to Mesdames J. Carrucan, C. Marich, and V. Palmer, who typed the manuscript, as well as to Julie Fraser, Alan Colenso, and Robert Alexander of Monash University who carefully produced most of the photographs and diagrams. Melbourne, 1988 PREFACE TO THE THIRD EDITION The central theme of the first two editions was microstructure/property relation- ships in which special attention was given to the roles of the various alloying elements present in light alloys. This general theme has been maintained in the third edition although some significant changes have been made to the format and content. As before, much of this revision involves the inclusion of new material which, in this case, has arisen from developments during the seven years since the second edition was published. The most notable change in format has been to group together, into a new chapter, information on what have been called new materials and processing methods. Examples are metal matrix and other com- posites, structural intermetallic compounds, nanophase and amorphous alloys. Interest in these and other novel light alloys has increased considerably during the last decade because of the unceasing demands for improvements in the prop- erties of engineering materials. Since light alloys have been at the forefront of many of these developments, the opportunity has been taken to review this area which has been the focus of so much recent research in materials science. Another feature of the third edition is the greater attention given to applica- tions of light alloys and their place in engineering. More case studies have been included, such as the use of light alloys in aircraft and motor cars. Economic factors associated with materials selection are also discussed in more detail. Moreover, since the light metals are often placed at a competitive disadvan- tage because of the high costs associated with their extraction from minerals, more attention has been given to these processes. This has led to a considerable increase in the size of the first chapter. Joining processes are described in more detail and, once again, service performance of light alloys is discussed with particular regard to mechanical behaviour and corrosion resistance. As a result of these various changes, the text has been expanded and the number of figures has been increased by a further 20%. Lists of books and articles for further reading have been updated. While the book continues to be directed primarily at senior undergraduate and postgraduate students, I believe it will again serve as a useful guide to the producers and users of light alloys. xiii xiv PREFACE TO THE THIRD EDITION I am again indebted for assistance given by colleagues and associates who have provided me with information and helpful discussions. General acknowl- edgement is made to publishers, societies and individuals who have responded to requests for photographs and diagrams that have been reproduced in their original or modified form. Finally I wish to express my gratitude to my wife Margaret for her constant encouragement, to Carol Marich and Pam Hermansen who typed the manuscript and to Julie Fraser and Robert Alexander who once again carefully produced so many of the photographs and diagrams. I. J. Polmear Melbourne 1995 PREFACE TO THE FOURTH EDITION Since the third edition of Light Alloys appeared in 1995, developments with new alloys and processes have continued at an escalating rate. Competition between different materials, metallic and nonmetallic, has increased as produc- ers seek both to defend their traditional markets and to penetrate the markets of others. New compositions of aluminium, magnesium, and titanium alloy have been formulated, and increasing attention has been given to the development of novel and more economical processing methods. Because of their ease of han- dling, aluminium alloys in particular have been used as experimental models for many of the changes. Recently, potential automotive applications have led to a resurgence of interest in cast and wrought magnesium alloys. The central theme of earlier editions was microstructure/property relation- ships, and particular attention was given to the roles of the various alloying ele- ments present in light alloys. This general theme has been maintained in the fourth edition although further significant changes have been made to format and content. Special consideration has again been given to the physical metallurgy of aluminium alloys and many of the general principles also apply to magnesium and titanium alloys. The description of changes occurring during the process- ing of the major class of nonheat-treatable aluminium alloys has been extended. Although a century has now elapsed since the discovery of age hardening by Alfred Wilm, new observations are still being made as the latest experimental techniques reveal more details of the actual atomic processes involved. As exam- ples, more information is now available about the role of solute and vacancy clusters during the early stages of aging, as well as other phenomena such as secondary hardening. Some success has been achieved with the modeling of pre- cipitation processes. Precipitation hardening was hailed as the first nanotechnol- ogy and now it is possible to develop fine-scale microstructures in a much wider range of alloys through the use of novel processing methods. Some new topics in this fourth edition are strip and slab casting, creep forming, joining technologies such as friction stir and laser welding, metallic foams, quasicrystals, and the production of nanophase materials. Economic factors associated with the production and selection of light metals and alloys xv