Engineering Materials 2 An Introduction to Microstructures, Processing and Design Engineering Materials 2 An Introduction to Microstructures, Processing and Design Second Edition by Michael F. Ashby and David R. H. Jones Department of Engineering, Cambridge University, England OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801-2041 A division of Reed Educational and Professional Publishing Ltd A member of the Reed Elsevier plc group First edition 1986 Reprinted with corrections 1988 Reprinted 1989, 1992 Second edition 1998 Reprinted 1999 © Michael F. Ashby and David R. H. Jones 1998 All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 9HE. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of Congress ISBN 0 7506 4019 7 Printed and bound in Great Britain by Biddles Ltd, Guildford and Kingd’s Lynn Contents General introduction ix A. Metals 1. Metals 3 the generic metals and alloys; iron-based, copper-based, nickel-based, aluminium-based and titanium-based alloys; design data 2. Metal structures 14 the range of metal structures that can be altered to get different properties: crystal and glass structure, structures of solutions and compounds, grain and phase boundaries, equilibrium shapes of grains and phases 3. Equilibrium constitution and phase diagrams 25 how mixing elements to make an alloy can change their structure; examples: the lead–tin, copper–nickel and copper–zinc alloy systems 4. Case studies in phase diagrams 34 choosing soft solders; pure silicon for microchips; making bubble-free ice 5. The driving force for structural change 46 the work done during a structural change gives the driving force for the change; examples: solidification, solid-state phase changes, precipitate coarsening, grain growth, recrystallisation; sizes of driving forces 6. Kinetics of structural change: I – diffusive transformations 57 why transformation rates peak – the opposing claims of driving force and thermal activation; why latent heat and diffusion slow transformations down 7. Kinetics of structural change: II – nucleation 68 how new phases nucleate in liquids and solids; why nucleation is helped by solid catalysts; examples: nucleation in plants, vapour trails, bubble chambers and caramel 8. Kinetics of structural change: III – displacive transformations 76 how we can avoid diffusive transformations by rapid cooling; the alternative – displacive (shear) transformations at the speed of sound 9. Case studies in phase transformations 89 artificial rain-making; fine-grained castings; single crystals for semiconductors; amorphous metals 10. The light alloys 100 where they score over steels; how they can be made stronger: solution, age and work hardening; thermal stability 11. Steels: I – carbon steels 113 structures produced by diffusive changes; structures produced by displacive changes (martensite); why quenching and tempering can transform the strength of steels; the TTT diagram 12. Steels: II – alloy steels 125 adding other elements gives hardenability (ease of martensite formation), solution strengthening, precipitation strengthening, corrosion resistance, and austenitic (f.c.c.) steels 13. Case studies in steels 133 metallurgical detective work after a boiler explosion; welding steels together safely; the case of the broken hammer 14. Production, forming and joining of metals 143 processing routes for metals; casting; plastic working; control of grain size; machining; joining; surface engineering B. Ceramics and glasses 15. Ceramics and glasses 161 the generic ceramics and glasses: glasses, vitreous ceramics, high- technology ceramics, cements and concretes, natural ceramics (rocks and ice), ceramic composites; design data 16. Structure of ceramics 167 crystalline ceramics; glassy ceramics; ceramic alloys; ceramic micro- structures: pure, vitreous and composite 17. The mechanical properties of ceramics 177 high stiffness and hardness; poor toughness and thermal shock resistance; the excellent creep resistance of refractory ceramics vi Contents 18. The statistics of brittle fracture and case study 185 how the distribution of flaw sizes gives a dispersion of strength: the Weibull distribution; why the strength falls with time (static fatigue); case study: the design of pressure windows 19. Production, forming and joining of ceramics 194 processing routes for ceramics; making and pressing powders to shape; working glasses; making high-technology ceramics; joining ceramics; applications of high-performance ceramics 20. Special topic: cements and concretes 207 historical background; cement chemistry; setting and hardening of cement; strength of cement and concrete; high-strength cements C. Polymers and composites 21. Polymers 219 the generic polymers: thermoplastics, thermosets, elastomers, natural polymers; design data 22. The structure of polymers 228 giant molecules and their architecture; molecular packing: amorphous or crystalline? 23. Mechanical behaviour of polymers 238 how the modulus and strength depend on temperature and time 24. Production, forming and joining of polymers 254 making giant molecules by polymerisation; polymer “alloys”; forming and joining polymers 25. Composites: fibrous, particulate and foamed 263 how adding fibres or particles to polymers can improve their stiffness, strength and toughness; why foams are good for absorbing energy 26. Special topic: wood 277 one of nature’s most successful composite materials D. Designing with metals, ceramics, polymers and composites 27. Design with materials 289 the design-limiting properties of metals, ceramics, polymers and composites; design methodology Contents vii 28. Case studies in design 296 1. Designing with metals: conveyor drums for an iron ore terminal 296 2. Designing with ceramics: ice forces on offshore structures 303 3. Designing with polymers: a plastic wheel 308 4. Designing with composites: materials for violin bodies 312 Appendix 1 Teaching yourself phase diagrams 320 Appendix 2 Symbols and formulae 370 Index 377 viii Contents understand the basic material. And finally we look at the role of materials in the design of engineering devices, mechanisms or structures, and develop a methodology for materials selection. One subject – Phase Diagrams – can be heavy going. We have tried to overcome this by giving a short programmed-learning course on phase dia- grams. If you work through this when you come to the chapter on phase diagrams you will know all you need to about the subject. It will take you about 4 hours. At the end of each chapter you will find a set of problems: try to do them while the topic is still fresh in your mind – in this way you will be able to consolidate, and develop, your ideas as you go along. To the lecturer This book has been written as a second-level course for engineering students. It pro- vides a concise introduction to the microstructures and processing of materials (metals, ceramics, polymers and composites) and shows how these are related to the properties required in engineering design. It is designed to follow on from our first-level text on the properties and applications of engineering materials,* but it is completely self- contained and can be used by itself. Each chapter is designed to provide the content of a 50-minute lecture. Each block of four or so chapters is backed up by a set of Case Studies, which illustrate and con- solidate the material they contain. There are special sections on design, and on such materials as wood, cement and concrete. And there are problems for the student at the end of each chapter for which worked solutions can be obtained separately, from the publisher. In order to ease the teaching of phase diagrams (often a difficult topic for engineering students) we have included a programmed-learning text which has proved helpful for our own students. We have tried to present the material in an uncomplicated way, and to make the examples entertaining, while establishing basic physical concepts and their application to materials processing. We found that the best way to do this was to identify a small set of “generic” materials of each class (of metals, of ceramics, etc.) which broadly typified the class, and to base the development on these; they provide the pegs on which the discussion and examples are hung. But the lecturer who wishes to draw other materials into the discussion should not find this difficult. Acknowledgements We wish to thank Prof. G. A. Chadwick for permission to reprint Fig. A1.34 (p. 340) and K. J. Pascoe and Van Nostrand Reinhold Co. for permission to reprint Fig. A1.41 (p. 344). x General introduction * M. F. Ashby and D. R. H. Jones, Engineering Materials 1: An Introduction to their Properties and Applications, 2nd edition, Butterworth-Heinemann, 1996. 2 Engineering Materials 2 [...]... m1 /2) 13 Melting temperature (K) Specific heat (J kg 1 K 1) Thermal conductivity (W m 1 K 1) Thermal expansion coefficient (MK 1) 0.3 0 . 21 0 .1 0 .2 0 .1 0 .2 0 .1 0.5 0–0 .18 80 14 0 20 –50 50 17 0 50 17 0 6 20 18 09 17 65 15 70 17 50 16 80 14 03 456 4 82 460 460 500 78 60 40 40 12 30 12 12 12 12 10 18 0.5–0.9 0.5 0.5 >10 0 30 10 0 30 10 0 13 56 11 90 1 12 0 385 397 12 1 85 17 20 19 >10 0 >10 0 >10 0 1 728 16 00 15 50 450 420 ... 21 4 60 340 800 300 680 13 00 Aluminium 10 00 Series 20 00 Series 5000 Series 7000 Series Casting alloys 910 910 11 00 10 00 11 00 11 00 (11 80) (11 80) (14 30) (13 00) (14 30) (14 30) 2. 7 2. 7 2. 8 2. 7 2. 8 2. 7 71 71 71 71 71 71 25 – 12 5 28 16 5 20 0–500 40–300 350–600 65–350 70 13 5 70 18 0 300–600 12 0 –430 500–670 13 0–400 Titanium Ti–6 A14 V 4630 (6 020 ) 5780 (7 510 ) 4.5 4.4 12 0 11 5 17 0 800–900 24 0 900 10 00 Zinc Lead–tin solder... 385 397 12 1 85 17 20 19 >10 0 >10 0 >10 0 1 728 16 00 15 50 450 420 450 89 22 11 13 14 12 0 .1 0.5 0 .1 0.45 0 .1 0 .25 0 .1 0.35 0 .1 0 .17 0. 01 0 .15 45 45 10 –50 30–40 20 –70 5–30 933 915 860 890 890 860 917 24 0 18 0 13 0 15 0 14 0 24 24 24 22 24 20 0 .25 0 .1 0 .2 50–80 19 40 1 920 530 610 22 6 9 8 693 456 650 390 12 0 31 420 11 0 27 0.4 0.5 0 .2 0.4 0.07–0 .15 wear resistance, thermal conductivity, electrical conductivity Structure-insensitive...  12 Engineering Materials 2 Table 1. 6 Properties of the generic metals Metal Density (Mg m −3) Young’s modulus (GPa) Yield strength (MPa) 7.9 7.9 7.8 7.8 7.8 7.4 21 1 21 0 21 0 20 3 21 5 1 52 50 22 0 350 16 00 29 0 16 00 17 0 16 00 50–400 1 020 (13 30) 750 10 60 (980 13 80) 15 00 (20 00) 8.9 8.4 8.4 13 0 10 5 12 0 75 20 0 20 0 22 0 350 350 Nickel Monels Superalloys 320 0 ( 420 0) 3000 (3900) 5000 (6500) 8.9 8.9 7.9 21 4 18 5 21 4... solder Diecasting alloy 330 (430) 20 00 (26 00) 800 (10 40) 7 .1 9.4 6.7 10 5 40 10 5 Iron Mild steel High-carbon steel Low-alloy steels High-alloy steels Cast irons Cost (UK£ (US$) tonne 1) 10 0 20 0 23 0 15 0 18 0 25 0 11 00 14 00 12 0 Copper Brasses Bronzes (14 0) (26 0–300) (20 0) (23 0–330) (14 00 18 00) (16 0) Tensile strength (MPa) 20 0 430 650 20 00 420 20 00 460 17 00 10 –800 12 0 28 0–330 Further reading Smithells’... c.p.h c.p.h 0.405 0 .22 9 0 .29 8 0 .28 9 0 .25 1 0.3 62 0.408 0. 320 0.384 0 .28 7 0.376 0.495 0. 3 21 0.8 91 0. 315 0.3 52 0.330 0.389 0.3 92 0.380 0.409 0.3 31 0.346 0 .29 5 0. 317 0.303 0.365 0 .26 7 0. 323 c 0.358 0.5 62 0.409 0.506 0.606 0. 5 21 0.553 0.468 0.573 0.495 0. 515 Fig 2. 1 Some metals have more than one crystal structure The most important examples of this polymorphism are in iron and titanium 15 ... alloys Their compositions and uses are summarised in Table 1. 1, and you will learn more about them in Chapters 11 and 12 , but let us now look at the other generic alloy groups An important group of alloys are those based on copper (Table 1 .2) The most notable part of the traction engine made from copper is the boiler and its firetubes (see Fig 1. 1) In full size this would have been made from mild steel,... Medium-stress uses: machinery parts – nuts and (+ ≈ 0.8 Mn) Fe + 0.7 to 1. 7 C (+ ≈ 0.8 Mn) Fe + 0 .2 C 0.8 Mn 1 Cr 2 Ni Fe + 0 .1 C 0.5 Mn 18 Cr 8 Ni Fe + 1. 8 to 4 C (+ ≈ 0.8 Mn 2 Si) shafts, gears High-stress uses: springs, cutting tools, dies Medium-carbon steel bolts, High-carbon steel Low-alloy steel High-alloy (“stainless”) steel Cast iron High-stress uses: pressure vessels, aircraft parts High-temperature... 8 Engineering Materials 2 Fig 1. 4 Miniature boiler fittings made from brass: a water-level gauge, a steam valve, a pressure gauge, and a feed-water injector Brass is so easy to machine that it is good for intricate parts like these Table 1. 3 Generic nickel-based metals Metals Monels Superalloys Typical composition (w t%) Typical uses Ni + 30 Cu 1 Fe 1 Mn Ni + 30 Cr 30 Fe 0.5 Ti 0.5 Al Ni + 10 Co 10 ...4 Engineering Materials 2 Fig 1. 1 A fully working model, one-sixth full size, of a steam traction engine of the type used on many farms a hundred years ago The model can pull an automobile on a few litres of water and a handful of coal But it is also a nice example of materials selection and design Table 1. 1 Generic iron-based metals Metal Typical composition . 78 12 0 . 21 14 0 17 65 4 82 60 12 0 .1 0 .2 20–50 15 70 460 40 12 0 .1 0 .2 50 17 0 17 50 460 40 12 0 .1 0.5 50 17 0 16 80 500 12 30 10 18 0–0 .18 6 20 14 03 0.5–0.9 > ;10 0 13 56 385 397 17 0.5 30 10 0 11 90 12 1 . 11 90 12 1 20 0.5 30 10 0 1 120 85 19 0.4 > ;10 0 1 728 450 89 13 0.5 > ;10 0 16 00 420 22 14 0 .2 > ;10 0 15 50 450 11 12 0 .1 0.5 45 933 917 24 0 24 0 .1 0.45 45 915 24 0 .1 0 .25 10 –50 860 18 0 24 0 .1 0.35. 24 0 .1 0.35 30–40 890 13 0 22 0 .1 0 .17 20 –70 890 15 0 24 0. 01 0 .15 5–30 860 14 0 20 0 .25 19 40 530 22 9 0 .1 0 .2 50–80 1 920 610 6 8 0.4 693 390 12 0 31 456 0.07–0 .15 650 420 11 0 27 wear resistance, thermal