Phase Transformations Metals Alloys相变金属合金.pdf

Published by Chapan L Hall,2-6 Bormdary Row,London SEl m,LX Chapman&Hall,2-6 Boundary Raw,London SEl 8HN,UK Chapman&Eldl GmbH,Pappclallee 3,69469 Wtinbeim,Germany Chapman&Hall USA,115 fifth P:*ermt,NEW YO&,NY 10003,USA Chaimao Bt HaU Japan,l7?-Japan,Kyowa Building,3F,2-2-1 Ruahwachu,Chiyoda-b,Tokyo 102,Japan Chapman&Hall Australia,1M Dodds Stnet,South Mtlboumc,Victoria 3205,Australia Chapman&Hall India,R.Seshadri,32 Stcond Main Road,CIT East,Madnrs 600 035,India First edition 1981 Reprinted 1982,1983,1984,1986,1987,1988,1989,1990,1992 Second edition 1992 Reprinted I993(twice),1995,1996 0 1981,I992 D.A.Porter and K.E.Easterling Typeset in 10112pt Times by Bed-set Typcseuw hd,Rong Kong,Printed in Gnat Brimin by T.J.Pms(jadstow)Ltd,Cornwall ISBN 0 412 45030 5 Apart f r o m any hir dealing for the purposes of research or private study,or criticism o r rcviw,as permitted under the UK CopyrigM Dcsigna a d Patents Act,1988,this publication may not be reprcduccd,.stoced.or transmitted,in any form or by any mans,without the prior permission in writing of rhe pubtishefa,or in thc cast of reprographic reproduction only in accordance with the tm of the licencts issued by the Copyright Lictasing Agmcy in the UK,or in accordance with the tams of li-issued by the appropriate Reproduction Rights Organization outside the UK Enquiries concerning rcproduftion outside the term slated hwe should be sglt to the publishers at the London add-printed on this page.The publisher makta no repmentation,expmss or implied,with regard t o thc accuracy of the information conktined in this book and cannot accept any legal rwponsibility or liability for any crmrs or omissions that may be made.A Cataiogut m r d for this book is available ftom the British Library Library of Congreu Cataloging-in-Publication Data available n BPrinted on permanent acid-fm text apsr manufatuA in accordance with ANSUNIS0 239.48-1992 and ANSUNLO 239.4%1984(Pcrmansncc of Paper).Contents Preface to the second edition Preface to rhe first edition I Thermodynamia and Phase Diagrams 1.1 Equilibrium 1.2 Single ornonenf Systems 1.3.1 Gibhs Free Energy as a Function of Temperature 1.1.1 Pressure Effects 1.2.3 The Driving Force for Soliditicatiun 1.3 Binary Solutions 1.3.1 The Gibbs Free Enerpy of Binary Solutions 1.3.2 Ideal Solutions 1.3.3 Chemical Potential 1.3.4 Regular Solutions 1.3.5 Activity 1.3.6 Real Solutions 1.3.7 Ordered Phases 1.3.8 Intermediate Phases 1.3 Equilibrium in Heterogeneous Systems 1.5 Binary Phase Diagrams I 3.1 A Simple Phase Diagram 1.5.2 Systems with a Miscibility Gap 1.5.3 Ordered Alloys 1.5.4 Simple Eutectic Systems 1.5.5 Phase Diagrams Containing Intermediate Phases 1.5.6 TheGibbsPhaseRule 1.5.7 The Effect of Temperature on Solid Solubility 1.5.1:Equilibrium Vacancy Concentration 1.6 The Influence of Interfaces on Equilibrium 1.7 Ternary Equilibrium 1.8 Additional Thermodynamic Relationships for Binary Solutions 1.9 The Kinetics of Phase Transformations References Further Reading Exercises xi xii vi Con(en IS 2 Diffusion 2.1 Atomic Mechanisms of Diffusion 2.2 Interstitial Diffusion 2.7.1 Interstitial Diffusion as a Random Jump Process 2.2.2 Effect of Temperature-Thermal Activation 2.2.3 Steady-State Diffusion 2.2.4 Nonsteady-State Diffusion 2.2.5 Solutions to the Diffusion Equation Homogenization The Carburization of Steel 2.3 Substitutional Diffusion 2.3.1 Self-Diffusion 2.3.2 Vacancy Diffusion 2.3.3 Diffusion in Substitutional Allnys 2.3.4 Diffusion in Dilute Substitutional Alloys 2.4 Atomic Mobility 2.5 Tracer Diffusion in Binary Alloys 2.6 Diffusion in Ternary Alloys 2.7 High-Diffusivity Paths 2.7.1 Diffusion along Grain Boundaries end Free Surfaces 2.7.2 Diffusion along Dislocations 2.8 Diffusion in Multiphase Binary Svstems References Further Reading Exercises 3 Crystal Interfaces and Microstructure 3.1 Interfacial Free Energy 3.2 SolidJVapour Interfaces 3.3 Boundaries in Single-Phase Solids 3.3.1 Low-Angle and High-Angle Boundaries 3.3.2 Special High-Angle Grain Boundaries 3.3.3 Equilibrium in Polycrystalline Materials 3.3.4 Thermally Activated Migration of Grain Boundaries 3.3.5 The Kinetics of Grain Growth 3.4 Interphase Interfaces in Solids 3.3.f Interface Coherence Fully Coherent Interfaces Semicoheren t interfaces Incoherent Interfaces Complex Semicoherent Interfaces 3.4.2 Second-Phase Shape:Interfacial Energy Effects Fully Coherent Precipitates Partially Coherent Precipitates Incoherent Precipitates Precipitates on Grain Boundaries Confens vii 3.3.3 Second-Phase Shape:Misfit Strain Effects Fully Coherent Precipitates Incoherent Inclusions Plate-Like Precipitates 3.4.3 Coherency Loss _ 3.4.5 Glissiie Interfaces 3.1.6 SolidlLiquid Interfaces 3.5 Interface Migration 3.5.1 Diffusion-Controlled and Interface-Controlled Growth References Further Reading Exercises 4 Solidification 185 4.I Nucleation in Pure Metals 135 4.1.1 Homoeneous Nuclealion 18b 4.1.2 The Homogeneous Nucleoton Rate 190 4.1.3 Heterogeneous Nucleation 192 4.1.4 Nucleation of Melting 197 4.2 Growth o f a Pure Solid 197 4.2.1 Continuous Growth 198 1.2.1 Lateral Growth 198 Surface Nucleation 1(M Spral Growth 20 1 Growth from Twin Intersections 202 4.2.3 Heat Flow and Interface Stability 203 4.3 Alloy Solidification 1117 4.1.1 Solidiiication of Single-Phase Alloys 208 Equliibrium Solidification 108 No Diffusion in Solid.Perfect Mixing in Liquid 208 No Diffusion in Solid,Diffusional Mixing In tiquld 212 Cellular and Dendritic Solidification 214-4.3.2 Eutectic Solidification 222 Growth of Lamellar Eutectics 223 4.3.3 Off-Eutectic Alloys 229 4.3.1 Perltectic Solidification 73 1 4.4 Solidification of Ingots and Castings 233 4.4.1 Ingot Structure 233 Chill Zone 234 Columnar Zone 735 Equiaxed Zone 236 Shrinkage Effects 236.4.4.2 Segegation in lngots and Castings 237 4.4.3 Continuous Casting 233 Heat Flow in Welding and Continuous Casting 239 4.5 Solidification of Fusion Welds Influence of Welding Speed Geometry of Crystal Growth 4.6 Solidification during Quenching from the Melt 4.7 Case Studies of some Practical Castings and Welds 4.7.1 Casting of Carbon and Low-Alloy Steels-1.7.2 Casting of High-Speed Steels,3.7.3 Stainless Steel Weld Metal References Further Reading Exercises 5 Diffusional Transformations in Solids 5.1 Homogeneous Nucleation in Solids 5.2 Heterogeneous Nucleation Nucleation on Grain Boundaries Dislocations Excess Vacancies 5.2.1 Rate of Heterogeneous Nudeation 5.3 Precipitate Growth 5.3.1 Gruwth behind Planar Incoherent Interfaces Sa3.2 Diffusion-Contmlled Lengthening of Plates or Needles 5.3.3 Thickening of Plate-like Precipitates 5.1 Overall Transformation Kinetics-TIT Diagrams-i.S Precipitation in Age-Hardening Alloys 5.5.1 Precipitation in Aluminium-Copper Alloys GP Zones Transition Phases 5.6.2 Precipitation in Aluminium-Silver Alloys 5.5.3 Quenched-in Vacancies 5.5.4 Age Hardening 5.5.5 Spinoda t Decompositicn 3.5.6 Particle Coarsening Low y Low x,Low D 5.6 The Precipitation of Ferrite from Austenite 5.7 Cellular Precipitation 5.8 Eutectoid Transformations 5.8.I The Pearlite Reaction in Fe-C Alloys Nucleation of Pearlite Pearlite Growth Pearlite in Off-Eutectoid Fe-C Alloys 5.8.2 The Bainite Transformation Upper Bainite Lower Bainite Transformation Shears 5.8.3 The Effect of Alloying Elements on Hardenability 5.8.1 Continuous Cooling Diagrams 5.8.5 Fibrous and Interphase Precipittion in Alloy Steels 5-9 Massive Transformat ions 5.10 Ordering Transformarions 5.1 1 Case Studies 5.11.1 Titanium Forging Allays 5.1 1.2 The Weldability of Low-Carhnn and Microalloyed Rolled Steels References Further Reading Exercises 6 Diffusionless Transformations h.1 Characteristics uf Diffusionless Transformilttons h.1.1 The Solid Solution of Carbon in Iron 2 Martensite Uryatalluraphy h.2.1 The Bain Model of the fcc+hct Transformation 6.2.2 Comparison of Crystallographic Thcory with Experimental Results h.3 Theories o f Martensite Nucleation h.3.1 F(rmation of Coherent Nuclei of Marttssite 6.3.1 Role of Dislocations in Martunhitc?iuclculion h.3.3 Dislocation Strain Energ!A+%ised Transformation h.4 Martensite Growth 15.4.I Growth of Larh Martensite-6.4.2 Plate Martensite 6.4.3 Stabilization 6.4.4.Effect of External Stresses 6.4.5 Role of Grain Size 6.5 Pre-martensite Phenomena 6.6 Tempering of Ferrous Martensites Carbon Segregation E-Carbide Cementite AHoy Carbides Effect of Retamed Austenite Recovery,Recrystallization and Grain Growth Temper Emhrittlement-3%397 398 10 1 10h 100 410 412 415 415 Jlh Jlh 417 420 421-,.-122 412 476-.42h 127.6.7 Case studies 428 6.7.1 Carbon and Low-Alloy Quenched and Tempered Steels 428 6.7.2 Controlled Transformation Steels 430 6.7.3 The Shape-Memory Metal:Nitinol References Further Reading Exercises Solutions to exercises Compiled by John C.Ion Indev 439 I Preface to the second edition 441*I 510:In the ten years since this book was tirst published there have been man):new developments in the rnetallureical field.Rapidly solidified metals and glasses have come of age;new AI-Li alloys are now used in modem aircraft;microalloyed(structural)and high purity(pipeline)steels have become more sophisticated:radically new oxide-dispersed steels have ap-peared;a number of new memory metals have been developed:the list could go on.In spite of this.the undertyins principles governing ail of these developments have obviously not changed over the years.This is really the strength of the present text book.From the beginning we aimed to spell out these principles in a nice.readable way,and one in which undergraduates could appreciate and he capahle of developing for themselves.The present text is thus deliberately little changed from the original.We have,however.hopefully.corrected any errors.expanded the lists of further reading,and perhaps.most importantly.included a complete set of solutions to exercises.We hope that the revised edition continues to be enjoyed and appreciated in the many Schools of Metallury,Materials Science and Engineering Materials we know to he using our text throughout the world.In completing this rcvlsed edition we are grateful to the many people.students and professors;dike,who have written to us over the last decade.Partcular thanks are due to Dr Wen-Bin Li(Unversity of Lulei)for using a fine tooth-comb in bringing out both obvious and less obvious errors in the original text.There remain,(inevitably).a few points of contention concerning ourdecrition of certain phenomena.as raised by some of our correspondents,but there is nothing unhealthy about that.We should finail!like to thank Dr John Ion(University of Lappeenranta,Finland)for his help in compiling the Solutions to Exercises chapter.David Porter and Kenneth Easterling September 1 Wl Preface to the first edition This book is written as an undergraduate course in phase transformations for final year students specializing in metallurgy,materials science or engineering materials.It should also be useful for research students in-terested in revising their knowledge of the subject.The book is based on lectures originally given by the authors at the University of Lulel for engineerins students specializing in engineering materials.Surprisingly we found no modern treatments of this important subject in a form suitable for a course book,the most recent probably being P.G.Shewmons Tram-formations in Metals(McGraw-Hilt,1969).There have,however,been some notable developments in the subject over the last decade,particularly in studies of interfaces between phases and interface migration,as well as the kinetics of precipitate growth and the stability of precipitates.There have also been a number of important new practical developments based on phase transformations,including the introduction of TRIP steels(trans-formation induced by plastic deformation).directionally aligned eutectic composites.and sophisticated new structural steeIs with superior weldability and forming properties.to mention just a few.In addition.continuous casting and high speed,high energy fusion welding have emerged strongly in recent years as irnportan t production applications of solidification.It was the objective of this course to present a treatment of phase transformations in which these and other new developments could be explained in terms of the basic principles of thermodynamics and atomic mechanisms.The book is effectively in two parts.Chapters 1-3 contain the background material necessary for understanding phase transformations:thermo-dynamics,kinetic-.,diffusion theory and the structure and properties of interfaces.Chapters 4-6 deal with specific transformations:solidification,diffusional transformations in solids and diffusionless transformations.At the end of the chapters on solidification,diffusion-controlled transforma-tions and martensite,we give a few selected case studies of engineering alloys to illustrate sorne.of the principles discussed earlier.In this way,we hope that the text wil1:provide 9 usefu Link between theory and the practical reality.It should be stated that we found it necessary to give this course in conjunction with a number of practical laboratory exercises and worked examples.Scts of problems are aIso included at the end of each chapter of the book.In developing this course and wriring the text we have had continuous rifuue ro rhe firsr edirion.Xlll 1 support and encouragement of our colleagues and students in the Depari-ment of Engineerins Materials.Particular thanks are due LO Agneta Engfors I for her patience and skill in typing the manuscript as well as assisring with I the editing David Porter and Kenneth Easterling*Frhruury 1980 Thermodynamics and Phase Diagrams-I This chapter deals with some of the basic thermodynamic concepts that are t required for a more fundamental appreciation of phase diagrams and phase transformations.It is assumed that the student is already acquainted with elementary thermodynamics and only a summary of the most important results as regards phase transformations will be given here.Fuller treatment can be found in the books listed in the bibliography at the end of this chapter.The main use of thermodynamics in physical metallurgy is to allow the prediction of whether an alloy is in equilibrium.In considering phase trans-formations we are always concerned with changes towards equiiibrium.and thermodynamics is therefore a very powerful tool.It should be noted.how-ever.that the rate at which equilibrium is reached cannot be determined by thermodynamics alone,as will become apparent in later chapters.1.1 Equilibrium It is useful to begin this chapter on thermodynamics by defining a few of the terms that will be frequently used.In the study of phase transformations we will be dealing with the changes that can occur within a given system,e.g.an alloy that can exlst as a mixture of one or more phases.A phase can be defined as a portion of the system whose properties and composition are.homogeneous and which is physically distinct from other parts of the system