Me 3101 text

An Introduction

MATERIALS SCIENCE and ENGINEERING

William D. Callister, Jr.David G. Rethwisch

9E

Characteristics of Selected Elements

Atomic Density of Crystal Atomic Ionic Most MeltingAtomic Weight Solid, 20!C Structure, Radius Radius Common Point

Element Symbol Number (amu) (g/cm3) 20!C (nm) (nm) Valence (!C)

Aluminum Al 13 26.98 2.71 FCC 0.143 0.053 3! 660.4Argon Ar 18 39.95 Inert "189.2Barium Ba 56 137.33 3.5 BCC 0.217 0.136 2! 725Beryllium Be 4 9.012 1.85 HCP 0.114 0.035 2! 1278Boron B 5 10.81 2.34 Rhomb. 0.023 3! 2300Bromine Br 35 79.90 0.196 1" "7.2Cadmium Cd 48 112.41 8.65 HCP 0.149 0.095 2! 321Calcium Ca 20 40.08 1.55 FCC 0.197 0.100 2! 839Carbon C 6 12.011 2.25 Hex. 0.071 !0.016 4! (sublimes at 3367)Cesium Cs 55 132.91 1.87 BCC 0.265 0.170 1! 28.4Chlorine Cl 17 35.45 0.181 1" "101Chromium Cr 24 52.00 7.19 BCC 0.125 0.063 3! 1875Cobalt Co 27 58.93 8.9 HCP 0.125 0.072 2! 1495Copper Cu 29 63.55 8.94 FCC 0.128 0.096 1! 1085Fluorine F 9 19.00 0.133 1" "220Gallium Ga 31 69.72 5.90 Ortho. 0.122 0.062 3! 29.8Germanium Ge 32 72.64 5.32 Dia. cubic 0.122 0.053 4! 937Gold Au 79 196.97 19.32 FCC 0.144 0.137 1! 1064Helium He 2 4.003 Inert "272 (at 26 atm)Hydrogen H 1 1.008 0.154 1! "259Iodine I 53 126.91 4.93 Ortho. 0.136 0.220 1" 114Iron Fe 26 55.85 7.87 BCC 0.124 0.077 2! 1538Lead Pb 82 207.2 11.35 FCC 0.175 0.120 2! 327Lithium Li 3 6.94 0.534 BCC 0.152 0.068 1! 181Magnesium Mg 12 24.31 1.74 HCP 0.160 0.072 2! 649Manganese Mn 25 54.94 7.44 Cubic 0.112 0.067 2! 1244Mercury Hg 80 200.59 0.110 2! "38.8Molybdenum Mo 42 95.94 10.22 BCC 0.136 0.070 4! 2617Neon Ne 10 20.18 Inert "248.7Nickel Ni 28 58.69 8.90 FCC 0.125 0.069 2! 1455Niobium Nb 41 92.91 8.57 BCC 0.143 0.069 5! 2468Nitrogen N 7 14.007 0.010.02 5! "209.9Oxygen O 8 16.00 0.140 2" "218.4Phosphorus P 15 30.97 1.82 Ortho. 0.109 0.035 5! 44.1Platinum Pt 78 195.08 21.45 FCC 0.139 0.080 2! 1772Potassium K 19 39.10 0.862 BCC 0.231 0.138 1! 63Silicon Si 14 28.09 2.33 Dia. cubic 0.118 0.040 4! 1410Silver Ag 47 107.87 10.49 FCC 0.144 0.126 1! 962Sodium Na 11 22.99 0.971 BCC 0.186 0.102 1! 98Sulfur S 16 32.06 2.07 Ortho. 0.106 0.184 2" 113Tin Sn 50 118.71 7.27 Tetra. 0.151 0.071 4! 232Titanium Ti 22 47.87 4.51 HCP 0.145 0.068 4! 1668Tungsten W 74 183.84 19.3 BCC 0.137 0.070 4! 3410Vanadium V 23 50.94 6.1 BCC 0.132 0.059 5! 1890Zinc Zn 30 65.41 7.13 HCP 0.133 0.074 2! 420Zirconium Zr 40 91.22 6.51 HCP 0.159 0.079 4! 1852

Values of Selected Physical Constants

Quantity Symbol SI Units cgs Units

Avogadros number NA 6.022 # 1023 6.022 # 1023

molecules/mol molecules/molBoltzmanns constant k 1.38 # 10"23 J/atom K 1.38 # 10"16 erg/atom K

8.62 # 10"5 eV/atom KBohr magneton mB 9.27 # 10"24 A m2 9.27 # 10"21 erg/gaussa

Electron charge e 1.602 # 10"19 C 4.8 # 10"10 statcoulb

Electron mass 9.11 # 10"31 kg 9.11 # 10"28 gGas constant R 8.31 J/mol K 1.987 cal/mol KPermeability of a vacuum m0 1.257 # 10"6 henry/m unitya

Permittivity of a vacuum $0 8.85 # 10"12 farad/m unityb

Plancks constant h 6.63 # 10"34 J s 6.63 # 10"27 erg s4.13 # 10"15 eV s

Velocity of light in a vacuum c 3 # 108 m/s 3 # 1010 cm/sa In cgs-emu units.b In cgs-esu units.

###

##

####

Unit AbbreviationsA % ampere in. % inch N % newton

% angstrom J % joule nm % nanometerBtu % British thermal unit K % degrees Kelvin P % poise

C % Coulomb kg % kilogram Pa % Pascal&C % degrees Celsius lbf % pound force s % secondcal % calorie (gram) lbm % pound mass T % temperaturecm % centimeter m % meter 'm % micrometereV % electron volt Mg % megagram (micron)&F % degrees Fahrenheit mm % millimeter W % wattft % foot mol % mole psi % pounds per squareg % gram MPa % megapascal inch

SI Multiple and Submultiple Prefixes

Factor by WhichMultiplied Prefix Symbol

109 giga G106 mega M103 kilo k10"2 centia c10"3 milli m10"6 micro '10"9 nano n10"12 pico p

a Avoided when possible.

WileyPLUS builds students confidence because it takes the guesswork out of studying by providing students with a clear roadmap:

what to do how to do it if they did it right

It offers interactive resources along with a complete digital textbook that help students learn more. With WileyPLUS, students take more initiative so youll have

greater impact on their achievement in the classroom and beyond.

For more information, visit www.wileyplus.com

Now available for

WileyPLUS is a research-based online environment for effective teaching and learning.

ALL THE HELP, RESOURCES, AND PERSONAL SUPPORT YOU AND YOUR STUDENTS NEED!

www.wileyplus.com/resources

Technical Support 24/7FAQs, online chat,and phone support

www.wileyplus.com/support

Student support from an experienced student user

Collaborate with your colleagues,find a mentor, attend virtual and live

events, and view resources

2-Minute Tutorials and allof the resources you and yourstudents need to get started

Your WileyPLUS Account Manager, providing personal training

and support

www.WhereFacultyConnect.com

Pre-loaded, ready-to-use assignments and presentations

created by subject matter experts

StudentPartnerProgram

QuickStart

Courtney Keating/iStockphoto

9th Edition

Materials Scienceand Engineering

AN INTRODUCTION

WILLIAM D. CALLISTER, JR.Department of Metallurgical Engineering

The University of Utah

DAVID G. RETHWISCHDepartment of Chemical and Biochemical Engineering

The University of Iowa

Front Cover: Depiction of a unit cell for iron carbide (Fe3C) from three different perspectives. Brown and blue spheres represent iron and carbon atoms, respectively.Back Cover: Three representations of the unit cell for body-centered cubic iron (a-ferrite); each unit cell contains an interstitial carbon atom.

VICE PRESIDENT AND EXECUTIVE PUBLISHER Donald FowleyEXECUTIVE EDITOR Daniel SayreEDITORIAL PROGRAM ASSISTANT Jessica KnechtSENIOR CONTENT MANAGER Kevin HolmPRODUCTION EDITOR James MetzgerEXECUTIVE MARKETING MANAGER Christopher RuelDESIGN DIRECTOR Harry NolanSENIOR DESIGNER Madelyn LesureSENIOR PHOTO EDITOR MaryAnn PriceCOVER ART Roy Wiemann and William D. Callister, Jr.

This book was set in 9.5/11.5 Times Ten LT Std by Aptara, Inc., and printed and bound by Quad Graphics/Versailles. The cover was printed by Quad Graphics/Versailles.

This book is printed on acid-free paper. q

Copyright 2014, 2010, 2007, 2003, 2000 John Wiley & Sons, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, website www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030-5774, (201) 748-6011, fax (201) 748-6008, website www.wiley.com/go/permissions.

Evaluation copies are provided to qualified academics and professionals for review purposes only, for use in their courses during the next academic year. These copies are licensed and may not be sold or transferred to a third party. Upon completion of the review period, please return the evaluation copy to Wiley. Return instructions and a free of charge return shipping label are available at www.wiley.com/go/returnlabel. Outside of the United States, please contact your local representative.

ISBN: 978-1-118-32457-8Wiley Binder Version ISBN: 978-1-118-47770-0

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

Dedicated to Bill Stenquist, editor and friend

In this ninth edition we have retained the objectives and approaches for teaching materials science and engineering that were presented in previous editions. The first, and primary, objective is to present the basic fundamentals on a level appropriate for university/college students who have completed their freshmen calculus, chemistry, and physics courses.

The second objective is to present the subject matter in a logical order, from the simple to the more complex. Each chapter builds on the content of previous ones.

The third objective, or philosophy, that we strive to maintain throughout the text is that if a topic or concept is worth treating, then it is worth treating in sufficient detail and to the extent that students have the opportunity to fully understand it without having to consult other sources; in addition, in most cases, some practical relevance is provided.

The fourth objective is to include features in the book that will expedite the learning process. These learning aids include the following:

Numerous illustrations, now presented in full color, and photographs to help visualize what is being presented

Learning objectives, to focus student attention on what they should be getting from each chapter

Why Study . . . and Materials of Importance items as well as case studies that provide relevance to topic discussions

Concept Check questions that test whether a student understands the subject matter on a conceptual level

Key terms, and descriptions of key equations, highlighted in the margins for quick reference

End-of-chapter questions and problems designed to progressively develop students understanding of concepts and facility with skills

Answers to selected problems, so students can check their work A glossary, a global list of symbols, and references to facilitate understanding of the

subject matter End-of-chapter summary tables of important equations and symbols used in these

equations Processing/Structure/Properties/Performance correlations and summary concept

maps for four materials (steels, glass-ceramics, polymer fibers, and silicon semiconductors), which integrate important concepts from chapter to chapter

Materials of Importance sections that lend relevance to topical coverage by discussing familiar and interesting materials and their applications

The fifth objective is to enhance the teaching and learning process by using the newer tech-nologies that are available to most instructors and todays engineering students.

Preface

vii

viii Preface

New/Revised ContentSeveral important changes have been made with this Ninth Edition. One of the most signifi-cant is the incorporation of several new sections, as well as revisions/amplifications of other sections. These include the following:

Numerous new and revised example problems. In addition, all homework problems requiring computations have been refreshed.

Revised, expanded, and updated tables Two new case studies: Liberty Ship Failures (Chapter 1) and Use of Composites

in the Boeing 787 Dreamliner (Chapter 16) Bond hybridization in carbon (Chapter 2) Revision of discussions on crystallographic planes and directions to include the use

of equations for the determination of planar and directional indices (Chapter 3) Revised discussion on determination of grain size (Chapter 4) New section on the structure of carbon fibers (Chapter 13) Revised/expanded discussions on structures, properties, and applications of the

nanocarbons: fullerenes, carbon nanotubes, and graphene (Chapter 13) Revised/expanded discussion on structural composites: laminar composites and

sandwich panels (Chapter 16) New section on structure, properties, and applications of nanocomposite materials

(Chapter 16) Tutorial videos. In WileyPLUS, Tutorial Videos help students with their muddiest

points in conceptual understanding and problem-solving. Exponents and logarithms. In WileyPLUS, the exponential functions and natural

logarithms have been added to the Exponents and Logarithms section of the Math Skills Review.

Fundamentals of Engineering homework problems and questions for most chapters. These appear at the end of Questions and Problems sections and provide students the opportunity to practice answering and solving questions and problems similar to those found on Fundamentals of Engineering examinations.

Online Learning ResourcesStudent Companion Site at www.wiley.com/college/callister.Also found on the books website is a Students Companion page on which is posted several important instructional elements for the student that complement the text; these include the following:

Answers to Concept Check questions, questions which are found in the print book. Library of Case Studies. One way to demonstrate principles of design in an engineering

curriculum is via case studies: analyses of problem-solving strategies applied to real-world examples of applications/devices/failures encountered by engineers. Five case studies are provided as follows: (1) Materials Selection for a Torsionally Stressed Cylindrical Shaft; (2) Automobile Valve Spring; (3) Failure of an Automobile Rear Axle; (4) Artificial Total Hip Replacement; and (5) Chemical Protective Clothing.

Mechanical Engineering (ME) Module. This module treats materials science/engineering topics not covered in the printed text that are relevant to mechanical engineering.

Extended Learning Objectives. This is a more extensive list of learning objectives than is provided at the beginning of each chapter. These direct the student to study the subject material to a greater depth.

Preface ix

Student Lecture PowerPoint Slides. These slides (in both Adobe Acrobat PDF and PowerPoint formats) are virtually identical to the lecture slides provided to an instructor for use in the classroom. The student set has been designed to allow for note taking on printouts.

Index of Learning Styles. Upon answering a 44-item questionnaire, a users learning-style preference (i.e., the manner in which information is assimilated and processed) is assessed.

Online Resources for InstructorsInstructors Companion Site at www.wiley.com/college/callister.The Instructor Companion Site is available for instructors who have adopted this text. Please visit the website to register for access. Resources that are available include the following:

All resources found on the Student Companion Site. (Except for the Student Lecture PowerPoint Slides.)

Instructor Solutions Manual. Detailed solutions for all end-of-chapter questions and problems (in both Word and Adobe Acrobat PDF formats).

Homework Problem Correlation Guide8th edition to 9th edition. This guide notes, for each homework problem or question (by number), whether it appeared in the eighth edition and, if so, its number in this previous edition.

Virtual Materials Science and Engineering (VMSE). This web-based software package consists of interactive simulations and animations that enhance the learning of key concepts in materials science and engineering. Included in VMSE are eight modules and a materials properties/cost database. Titles of these modules are as follows: (1) Metallic Crystal Structures and Crystallography; (2) Ceramic Crystal Structures; (3) Repeat Unit and Polymer Structures; (4) Dislocations; (5) Phase Diagrams; (6) Diffusion; (7) Tensile Tests; and (8) Solid-Solution Strengthening.

Image Gallery. Illustrations from the book. Instructors can use them in assignments, tests, or other exercises they create for students.

Art PowerPoint Slides. Book art loaded into PowerPoints, so instructors can more easily use them to create their own PowerPoint Slides.

Lecture Note PowerPoints. These slides, developed by the authors and Peter M. Anderson (The Ohio State University), follow the flow of topics in the text, and include materials taken from the text as well as other sources. Slides are available in both Adobe Acrobat PDF and PowerPoint formats. [Note: If an instructor doesnt have available all fonts used by the developer, special characters may not be displayed correctly in the PowerPoint version (i.e., it is not possible to embed fonts in PowerPoints); however, in the PDF version, these characters will appear correctly.]

Solutions to Case Study Problems. Solutions to Problems in the Mechanical Engineering Web Module. Suggested Course Syllabi for the Various Engineering Disciplines. Instructors

may consult these syllabi for guidance in course/lecture organization and planning.

Experiments and Classroom Demonstrations. Instructions and outlines for experiments and classroom demonstrations that portray phenomena and/or illustrate principles that are discussed in the book; references are also provided that give more detailed accounts of these demonstrations.

x Preface

WileyPLUS is a research-based online environment for effective teaching and learning.WileyPLUS builds students confidence by taking the guesswork out of studying by

providing them with a clear roadmap: what is assigned, what is required for each assign-ment, and whether assignments are done correctly. Independent research has shown that students using WileyPLUS will take more initiative so the instructor has a greater impact on their achievement in the classroom and beyond. WileyPLUS also helps students study and progress at a pace thats right for them. Our integrated resourcesavailable 24/7function like a personal tutor, directly addressing each students demonstrated needs by providing specific problem-solving techniques.

What do students receive with WileyPLUS? The complete digital textbook that saves students up to 60% of the cost of the

in-print text. Navigation assistance, including links to relevant sections in the online textbook. Immediate feedback on performance and progress, 24/7. Integrated, multi-media resourcesto include VMSE (Virtual Materials Science &

Engineering), tutorial videos, a Math Skills Review, flashcards, and much more; these resources provide multiple study paths and encourage more active learning.

What do instructors receive with WileyPLUS? The ability to effectively and efficiently personalize and manage their course. The ability to track student performance and progress, and easily identify those

who are falling behind. Media-rich course materials and assessment resources includinga complete

Solutions Manual, PowerPoint Lecture Slides, Extended Learning Objectives, and much more. www.WileyPLUS.com

WileyPLUS

We have a sincere interest in meeting the needs of educators and students in the materi-als science and engineering community, and therefore we solicit feedback on this edition. Comments, suggestions, and criticisms may be submitted to the authors via email at the following address: [email protected].

Feedback

Since we undertook the task of writing this and previous editions, instructors and stu-dents, too numerous to mention, have shared their input and contributions on how to make this work more effective as a teaching and learning tool. To all those who have helped, we express our sincere thanks.

We express our appreciation to those who have made contributions to this edition. We are especially indebted to the following:

Audrey Butler of The University of Iowa, and Bethany Smith and Stephen Krause of Arizona State University, for helping to develop material in the WileyPLUS course.

Grant Head for his expert programming skills, which he used in developing the Vir-tual Materials Science and Engineering software.

Eric Hellstrom and Theo Siegrist of Florida State University for their feedback and suggestions for this edition.

Acknowledgments

Preface xi

In addition, we thank the many instructors who participated in the fall 2011 market-ing survey; their valuable contributions were driving forces for many of the changes and additions to this ninth edition.

We are also indebted to Dan Sayre, Executive Editor, Jennifer Welter, Senior Prod-uct Designer, and Jessica Knecht, Editorial Program Assistant, for their guidance and assistance on this revision.

Last, but certainly not least, we deeply and sinc erely appreciate the continual en-couragement and support of our families and friends.

William D. Callister, Jr. David G. Rethwisch

October 2013

Contents

LIST OF SYMBOLS xxi

1. Introduction 1

Learning Objectives 21.1 Historical Perspective 21.2 Materials Science and Engineering 21.3 Why Study Materials Science and

Engineering? 4 Case StudyLiberty Ship Failures 51.4 Classification of Materials 6 Case StudyCarbonated Beverage

Containers 111.5 Advanced Materials 121.6 Modern Materials Needs 141.7 Processing/Structure/Properties/

Performance Correlations 15Summary 17References 17Questions 18

2. Atomic Structure and Interatomic Bonding 19

Learning Objectives 202.1 Introduction 20

ATOMIC STRUCTURE 20

2.2 Fundamental Concepts 202.3 Electrons in Atoms 222.4 The Periodic Table 28

ATOMIC BONDING IN SOLIDS 30

2.5 Bonding Forces and Energies 302.6 Primary Interatomic Bonds 322.7 Secondary Bonding or van der Waals

Bonding 39 Materials of ImportanceWater (Its

Volume Expansion Upon Freezing) 422.8 Mixed Bonding 432.9 Molecules 442.10 Bonding Type-Materials Classification

Correlations 44Summary 45

Equation Summary 46List of Symbols 46Processing/Structure/Properties/Performance Summary 47Important Terms and Concepts 47References 47Questions and Problems 48Fundamentals of Engineering Questions and Problems 50

3. The Structure of Crystalline Solids 51


CRYSTAL STRUCTURES 52

3.2 Fundamental Concepts 523.3 Unit Cells 533.4 Metallic Crystal Structures 543.5 Density Computations 603.6 Polymorphism and Allotropy 60 Materials of ImportanceTin (Its

Allotropic Transformation) 613.7 Crystal Systems 62

CRYSTALLOGRAPHIC POINTS, DIRECTIONS, AND PLANES 64

3.8 Point Coordinates 643.9 Crystallographic Directions 673.10 Crystallographic Planes 753.11 Linear and Planar Densities 813.12 Close-Packed Crystal Structures 82

CRYSTALLINE AND NONCRYSTALLINE MATERIALS 84

3.13 Single Crystals 843.14 Polycrystalline Materials 843.15 Anisotropy 863.16 X-Ray Diffraction: Determination of

Crystal Structures 873.17 Noncrystalline Solids 92

Summary 93Equation Summary 95List of Symbols 96

xiii

xiv Contents

Processing/Structure/Properties/Performance Summary 96Important Terms and Concepts 97References 97Questions and Problems 97Fundamentals of Engineering Questions and Problems 104

4. Imperfections in Solids 105


POINT DEFECTS 106

4.2 Vacancies and Self-Interstitials 1064.3 Impurities in Solids 1084.4 Specification of Composition 111

MISCELLANEOUS IMPERFECTIONS 115

4.5 DislocationsLinear Defects 1154.6 Interfacial Defects 118 Materials of ImportanceCatalysts (and

Surface Defects) 1214.7 Bulk or Volume Defects 1224.8 Atomic Vibrations 122

MICROSCOPIC EXAMINATION 123

4.9 Basic Concepts of Microscopy 1234.10 Microscopic Techniques 1244.11 Grain-Size Determination 128

Summary 131Equation Summary 132List of Symbols 133Processing/Structure/Properties/Performance Summary 134Important Terms and Concepts 135References 135Questions and Problems 135Design Problems 138Fundamentals of Engineering Questions and Problems 139

5. Diffusion 140

Learning Objectives 1415.1 Introduction 1415.2 Diffusion Mechanisms 1425.3 Ficks First Law 1435.4 Ficks Second LawNonsteady-State

Diffusion 1455.5 Factors That Influence Diffusion 1495.6 Diffusion in Semiconducting

Materials 154 Material of ImportanceAluminum for

Integrated Circuit Interconnects 157

5.7 Other Diffusion Paths 158Summary 158Equation Summary 159List of Symbols 160Processing/Structure/Properties/Performance Summary 160Important Terms and Concepts 162References 162Questions and Problems 162Design Problems 166Fundamentals of Engineering Questions and Problems 167

6. Mechanical Properties of Metals 168

Learning Objectives 1696.1 Introduction 1696.2 Concepts of Stress and Strain 170

ELASTIC DEFORMATION 174

6.3 StressStrain Behavior 1746.4 Anelasticity 1776.5 Elastic Properties of Materials 177

PLASTIC DEFORMATION 180

6.6 Tensile Properties 1806.7 True Stress and Strain 1876.8 Elastic Recovery After Plastic

Deformation 1906.9 Compressive, Shear, and Torsional

Deformation 1916.10 Hardness 191

PROPERTY VARIABILITY AND DESIGN/SAFETY FACTORS 197

6.11 Variability of Material Properties 1976.12 Design/Safety Factors 199


7. Dislocations and Strengthening Mechanisms 216


DISLOCATIONS AND PLASTIC DEFORMATION 217

Contents xv

7.2 Basic Concepts 2187.3 Characteristics of Dislocations 2207.4 Slip Systems 2217.5 Slip in Single Crystals 2237.6 Plastic Deformation of Polycrystalline

Materials 2267.7 Deformation by Twinning 228

MECHANISMS OF STRENGTHENING IN METALS 229

7.8 Strengthening by Grain Size Reduction 2297.9 Solid-Solution Strengthening 2317.10 Strain Hardening 232

RECOVERY, RECRYSTALLIZATION, AND GRAIN GROWTH 235

7.11 Recovery 2357.12 Recrystallization 2367.13 Grain Growth 240


8. Failure 251


FRACTURE 253

8.2 Fundamentals of Fracture 2538.3 Ductile Fracture 2538.4 Brittle Fracture 2558.5 Principles of Fracture Mechanics 2578.6 Fracture Toughness Testing 265

FATIGUE 270

8.7 Cyclic Stresses 2708.8 The SN Curve 2728.9 Crack Initiation and Propagation 2768.10 Factors That Affect Fatigue Life 2788.11 Environmental Effects 280

CREEP 281

8.12 Generalized Creep Behavior 2818.13 Stress and Temperature Effects 2828.14 Data Extrapolation Methods 2858.15 Alloys for High-Temperature Use 286

Summary 287

Equation Summary 290List of Symbols 290Important Terms and Concepts 291References 291Questions and Problems 291Design Problems 295Fundamentals of Engineering Questions and Problems 296

9. Phase Diagrams 297


DEFINITIONS AND BASIC CONCEPTS 298

9.2 Solubility Limit 2999.3 Phases 3009.4 Microstructure 3009.5 Phase Equilibria 3009.6 One-Component (or Unary) Phase

Diagrams 301

BINARY PHASE DIAGRAMS 302

9.7 Binary Isomorphous Systems 3039.8 Interpretation of Phase Diagrams 3059.9 Development of Microstructure in

Isomorphous Alloys 3099.10 Mechanical Properties of Isomorphous

Alloys 3129.11 Binary Eutectic Systems 3129.12 Development of Microstructure in

Eutectic Alloys 318 Materials of ImportanceLead-Free

Solders 3199.13 Equilibrium Diagrams Having Intermediate

Phases or Compounds 3259.14 Eutectoid and Peritectic Reactions 3289.15 Congruent Phase Transformations 3299.16 Ceramic and Ternary Phase

Diagrams 3309.17 The Gibbs Phase Rule 330

THE IRONCARBON SYSTEM 333

9.18 The IronIron Carbide (FeFe3C) Phase Diagram 333

9.19 Development of Microstructure in IronCarbon Alloys 336

9.20 The Influence of Other Alloying Elements 344Summary 344Equation Summary 346List of Symbols 347Processing/Structure/Properties/Performance Summary 347Important Terms and Concepts 349

References 349Questions and Problems 349Fundamentals of Engineering Questions and Problems 355

10. Phase Transformations: Development of Microstructure and Alteration of Mechanical Properties 356


PHASE TRANSFORMATIONS 357

10.2 Basic Concepts 35710.3 The Kinetics of Phase Transformations 35810.4 Metastable Versus Equilibrium States 369

MICROSTRUCTURAL AND PROPERTY CHANGES IN IRONCARBON ALLOYS 370

10.5 Isothermal Transformation Diagrams 37010.6 Continuous-Cooling Transformation

Diagrams 38110.7 Mechanical Behavior of IronCarbon

Alloys 38410.8 Tempered Martensite 38810.9 Review of Phase Transformations and

Mechanical Properties for IronCarbon Alloys 391

Materials of ImportanceShape-Memory Alloys 394Summary 397Equation Summary 398List of Symbols 399Processing/Structure/Properties/Performance Summary 399Important Terms and Concepts 401References 402Questions and Problems 402Design Problems 406Fundamentals of Engineering Questions and Problems 406

11. Applications and Processing of Metal Alloys 408


TYPES OF METAL ALLOYS 410

11.2 Ferrous Alloys 41011.3 Nonferrous Alloys 422 Materials of ImportanceMetal Alloys

Used for Euro Coins 433

FABRICATION OF METALS 434

11.4 Forming Operations 434

11.5 Casting 43611.6 Miscellaneous Techniques 437

THERMAL PROCESSING OF METALS 439

11.7 Annealing Processes 43911.8 Heat Treatment of Steels 44111.9 Precipitation Hardening 451

Summary 458Processing/Structure/Properties/Performance Summary 460Important Terms and Concepts 460References 463Questions and Problems 463Design Problems 464Fundamentals of Engineering Questions and Problems 466

12. Structures and Properties of Ceramics 467


CERAMIC STRUCTURES 468

12.2 Crystal Structures 46912.3 Silicate Ceramics 47712.4 Carbon 48112.5 Imperfections in Ceramics 48212.6 Diffusion in Ionic Materials 48612.7 Ceramic Phase Diagrams 487

MECHANICAL PROPERTIES 490

12.8 Brittle Fracture of Ceramics 49112.9 StressStrain Behavior 49512.10 Mechanisms of Plastic Deformation 49712.11 Miscellaneous Mechanical

Considerations 499Summary 501Equation Summary 503List of Symbols 503Processing/Structure/Properties/Performance Summary 503Important Terms and Concepts 504References 505Questions and Problems 505Design Problems 509Fundamentals of Engineering Questions and Problems 509

13. Applications and Processing of Ceramics 510


TYPES AND APPLICATIONS OF CERAMICS 512

xvi Contents

13.2 Glasses 51213.3 GlassCeramics 51213.4 Clay Products 51413.5 Refractories 51413.6 Abrasives 51613.7 Cements 51713.8 Carbons 51813.9 Advanced Ceramics 521

FABRICATION AND PROCESSING OF CERAMICS 525

13.10 Fabrication and Processing of Glasses and GlassCeramics 526

13.11 Fabrication and Processing of Clay Products 531

13.12 Powder Pressing 53513.13 Tape Casting 537

Summary 538Processing/Structure/Properties/Performance Summary 540Important Terms and Concepts 542References 543Questions and Problems 543Design Problem 544Fundamentals of Engineering Questions and Problems 544

14. Polymer Structures 545

Learning Objectives 54614.1 Introduction 54614.2 Hydrocarbon Molecules 54614.3 Polymer Molecules 54914.4 The Chemistry of Polymer Molecules 54914.5 Molecular Weight 55314.6 Molecular Shape 55614.7 Molecular Structure 55814.8 Molecular Configurations 55914.9 Thermoplastic and Thermosetting

Polymers 56214.10 Copolymers 56314.11 Polymer Crystallinity 56414.12 Polymer Crystals 56814.13 Defects in Polymers 57014.14 Diffusion in Polymeric Materials 571

Summary 573Equation Summary 575List of Symbols 575Processing/Structure/Properties/Performance Summary 575Important Terms and Concepts 576References 576Questions and Problems 577Fundamentals of Engineering Questions and Problems 579

15. Characteristics, Applications, and Processing of Polymers 580


MECHANICAL BEHAVIOR OF POLYMERS 581

15.2 StressStrain Behavior 58115.3 Macroscopic Deformation 58415.4 Viscoelastic Deformation 58415.5 Fracture of Polymers 58815.6 Miscellaneous Mechanical

Characteristics 590

MECHANISMS OF DEFORMATION AND FOR STRENGTHENING OF POLYMERS 591

15.7 Deformation of Semicrystalline Polymers 591

15.8 Factors That Influence the Mechanical Properties of Semicrystalline Polymers 593

Materials of ImportanceShrink-Wrap Polymer Films 597

15.9 Deformation of Elastomers 597

CRYSTALLIZATION, MELTING, AND GLASS- TRANSITION PHENOMENA IN POLYMERS 599

15.10 Crystallization 60015.11 Melting 60115.12 The Glass Transition 60115.13 Melting and Glass Transition

Temperatures 60115.14 Factors That Influence Melting and Glass

Transition Temperatures 603

POLYMER TYPES 605

15.15 Plastics 605 Materials of ImportancePhenolic

Billiard Balls 60715.16 Elastomers 60815.17 Fibers 61015.18 Miscellaneous Applications 61015.19 Advanced Polymeric Materials 612

POLYMER SYNTHESIS AND PROCESSING 616

15.20 Polymerization 61615.21 Polymer Additives 61815.22 Forming Techniques for Plastics 62015.23 Fabrication of Elastomers 62215.24 Fabrication of Fibers and Films 622

Summary 624Equation Summary 626List of Symbols 626Processing/Structure/Properties/Performance Summary 626

Contents xvii

Important Terms and Concepts 629References 629Questions and Problems 629Design Questions 633Fundamentals of Engineering Question 633

16. Composites 634


PARTICLE-REINFORCED COMPOSITES 637

16.2 Large-Particle Composites 63716.3 Dispersion-Strengthened Composites 641

FIBER-REINFORCED COMPOSITES 642

16.4 Influence of Fiber Length 64216.5 Influence of Fiber Orientation and

Concentration 64316.6 The Fiber Phase 65116.7 The Matrix Phase 65316.8 Polymer-Matrix Composites 65316.9 Metal-Matrix Composites 65916.10 Ceramic-Matrix Composites 66016.11 CarbonCarbon Composites 66216.12 Hybrid Composites 66216.13 Processing of Fiber-Reinforced

Composites 663

STRUCTURAL COMPOSITES 665

16.14 Laminar Composites 66516.15 Sandwich Panels 667 Case StudyUse of Composites in the

Boeing 787 Dreamliner 66916.16 Nanocomposites 670

Summary 673Equation Summary 675List of Symbols 676Important Terms and Concepts 676References 676Questions and Problems 676Design Problems 679Fundamentals of Engineering Questions and Problems 680

17. Corrosion and Degradation of Materials 681


CORROSION OF METALS 683

17.2 Electrochemical Considerations 68317.3 Corrosion Rates 68917.4 Prediction of Corrosion Rates 691

17.5 Passivity 69817.6 Environmental Effects 69917.7 Forms of Corrosion 69917.8 Corrosion Environments 70717.9 Corrosion Prevention 70717.10 Oxidation 709

CORROSION OF CERAMIC MATERIALS 712

DEGRADATION OF POLYMERS 713

17.11 Swelling and Dissolution 71317.12 Bond Rupture 71517.13 Weathering 716


18. Electrical Properties 725


ELECTRICAL CONDUCTION 726

18.2 Ohms Law 72618.3 Electrical Conductivity 72718.4 Electronic and Ionic Conduction 72818.5 Energy Band Structures in

Solids 72818.6 Conduction in Terms of Band and

Atomic Bonding Models 73018.7 Electron Mobility 73218.8 Electrical Resistivity of Metals 73318.9 Electrical Characteristics of Commercial

Alloys 736 Materials of ImportanceAluminum

Electrical Wires 736

SEMICONDUCTIVITY 738

18.10 Intrinsic Semiconduction 73818.11 Extrinsic Semiconduction 74118.12 The Temperature Dependence of Carrier

Concentration 74418.13 Factors That Affect Carrier

Mobility 74518.14 The Hall Effect 74918.15 Semiconductor Devices 751

ELECTRICAL CONDUCTION IN IONIC CERAMICS AND IN POLYMERS 757

18.16 Conduction in Ionic Materials 758

xviii Contents

18.17 Electrical Properties of Polymers 758

DIELECTRIC BEHAVIOR 759

18.18 Capacitance 75918.19 Field Vectors and Polarization 76118.20 Types of Polarization 76418.21 Frequency Dependence of the Dielectric

Constant 76618.22 Dielectric Strength 76718.23 Dielectric Materials 767

OTHER ELECTRICAL CHARACTERISTICS OF MATERIALS 767

18.24 Ferroelectricity 76718.25 Piezoelectricity 768

Materials of ImportancePiezoelectric Ceramic Ink-Jet Printer Heads 769Summary 770Equation Summary 773List of Symbols 774Processing/Structure/Properties/Performance Summary 774Important Terms and Concepts 778References 778Questions and Problems 778Design Problems 782Fundamentals of Engineering Questions and Problems 783

19. Thermal Properties 785

Learning Objectives 78619.1 Introduction 78619.2 Heat Capacity 78619.3 Thermal Expansion 790 Materials of ImportanceInvar

and Other Low-Expansion Alloys 792

19.4 Thermal Conductivity 79319.5 Thermal Stresses 796


20. Magnetic Properties 803

Learning Objectives 80420.1 Introduction 80420.2 Basic Concepts 804

20.3 Diamagnetism and Paramagnetism 80820.4 Ferromagnetism 81020.5 Antiferromagnetism

and Ferrimagnetism 81120.6 The Influence of Temperature on Magnetic

Behavior 81520.7 Domains and Hysteresis 81620.8 Magnetic Anisotropy 81920.9 Soft Magnetic Materials 820 Materials of ImportanceAn

IronSilicon Alloy Used in Transformer Cores 821

20.10 Hard Magnetic Materials 82220.11 Magnetic Storage 82520.12 Superconductivity 828


21. Optical Properties 838


BASIC CONCEPTS 839

21.2 Electromagnetic Radiation 83921.3 Light Interactions with Solids 84121.4 Atomic and Electronic

Interactions 842

OPTICAL PROPERTIES OF METALS 843

OPTICAL PROPERTIES OF NONMETALS 844

21.5 Refraction 84421.6 Reflection 84621.7 Absorption 84621.8 Transmission 85021.9 Color 85021.10 Opacity and Translucency in

Insulators 852

APPLICATIONS OF OPTICAL PHENOMENA 853

21.11 Luminescence 85321.12 Photoconductivity 853 Materials of ImportanceLight-Emitting

Diodes 85421.13 Lasers 85621.14 Optical Fibers in Communications 860

Contents xix

Summary 862Equation Summary 864List of Symbols 865Important Terms and Concepts 865References 865Questions and Problems 866Design Problem 867Fundamentals of Engineering Questions and Problems 867

22. Economic, Environmental, and Societal Issues in Materials Science and Engineering 868


ECONOMIC CONSIDERATIONS 869

22.2 Component Design 87022.3 Materials 87022.4 Manufacturing Techniques 870

ENVIRONMENTAL AND SOCIETAL CONSIDERATIONS 871

22.5 Recycling Issues in Materials Science and Engineering 873

Materials of ImportanceBiodegradable and Biorenewable Polymers/ Plastics 876Summary 878References 879Design Questions 879

Appendix A The International System of Units (SI) 880

Appendix B Properties of Selected Engineering Materials 882

B.1 Density 882B.2 Modulus of Elasticity 885B.3 Poissons Ratio 889B.4 Strength and Ductility 890B.5 Plane Strain Fracture Toughness 895B.6 Linear Coefficient of Thermal

Expansion 897B.7 Thermal Conductivity 900B.8 Specific Heat 903B.9 Electrical Resistivity 906B.10 Metal Alloy Compositions 909

Appendix C Costs and Relative Costs for Selected Engineering Materials 911Appendix D Repeat Unit Structures for Common Polymers 916Appendix E Glass Transition and Melting Temperatures for Common Polymeric Materials 920Glossary 921Answers to Selected Problems 934Index 939

xx Contents

List of Symbols

The number of the section in which a symbol is introduced or explained is given in parentheses.

A = area = angstrom unit Ai = atomic weight of

element i (2.2) APF = atomic packing factor (3.4) a = lattice parameter: unit cell

x-axial length (3.4) a = crack length of a surface crack

(8.5) at% = atom percent (4.4) B = magnetic flux density

(induction) (20.2) Br = magnetic remanence (20.7) BCC = body-centered cubic crystal

structure (3.4) b = lattice parameter: unit cell

y-axial length (3.7) b = Burgers vector (4.5) C = capacitance (18.18) Ci = concentration (composition) of

component i in wt% (4.4) Ci = concentration (composition) of

component i in at% (4.4) Cy, Cp = heat capacity at constant

volume, pressure (19.2) CPR = corrosion penetration rate

(17.3) CVN = Charpy V-notch (8.6) %CW = percent cold work (7.10) c = lattice parameter: unit cell

z-axial length (3.7) c = velocity of electromagnetic

radiation in a vacuum (21.2) D = diffusion coefficient (5.3) D = dielectric displacement (18.19) DP = degree of polymerization (14.5) d = diameter d = average grain diameter (7.8)

dhkl = interplanar spacing for planes of Miller indices h, k, and l (3.16)

E = energy (2.5) E = modulus of elasticity or

Youngs modulus (6.3) e = electric field intensity (18.3) Ef = Fermi energy (18.5) Eg = band gap energy (18.6) Er(t) = relaxation modulus (15.4) %EL = ductility, in percent elongation

(6.6) e = electric charge per electron

(18.7) e- = electron (17.2) erf = Gaussian error function (5.4) exp = e, the base for natural

logarithms F = force, interatomic or

mechanical (2.5, 6.2) f = Faraday constant (17.2) FCC = face-centered cubic crystal

structure (3.4) G = shear modulus (6.3) H = magnetic field strength (20.2) Hc = magnetic coercivity (20.7) HB = Brinell hardness (6.10) HCP = hexagonal close-packed crystal

structure (3.4) HK = Knoop hardness (6.10) HRB, HRF = Rockwell hardness: B and F

scales (6.10) HR15N, HR45W = superficial Rockwell hardness:

15N and 45W scales (6.10) HV = Vickers hardness (6.10) h = Plancks constant (21.2) (hkl) = Miller indices for a crystallo-

graphic plane (3.10)

xxi

xxii List of Symbols

(hkil) = Miller indices for a crystal-lographic plane, hexagonal crystals (3.10)

I = electric current (18.2) I = intensity of electromagnetic

radiation (21.3) i = current density (17.3) iC = corrosion current density (17.4) J = diffusion flux (5.3) J = electric current density (18.3) Kc = fracture toughness (8.5) KIc = plane strain fracture tough-

ness for mode I crack surface displacement (8.5)

k = Boltzmanns constant (4.2) k = thermal conductivity (19.4) l = length lc = critical fiber length (16.4) ln = natural logarithm log = logarithm taken to base 10 M = magnetization (20.2) Mn = polymer number-average

molecular weight (14.5) Mw = polymer weight-average

molecular weight (14.5) mol% = mole percent N = number of fatigue cycles (8.8) NA = Avogadros number (3.5) Nf = fatigue life (8.8) n = principal quantum number (2.3) n = number of atoms per unit cell

(3.5) n = strain-hardening exponent (6.7) n = number of electrons in an

electrochemical reaction (17.2) n = number of conducting elec-

trons per cubic meter (18.7) n = index of refraction (21.5) n = for ceramics, the number of

formula units per unit cell (12.2)

ni = intrinsic carrier (electron and hole) concentration (18.10)

P = dielectric polarization (18.19) PB ratio = PillingBedworth ratio (17.10) p = number of holes per cubic

meter (18.10) Q = activation energy Q = magnitude of charge stored

(18.18) R = atomic radius (3.4) R = gas constant %RA = ductility, in percent reduction

in area (6.6) r = interatomic distance (2.5)

r = reaction rate (17.3) rA, rC = anion and cation ionic radii

(12.2) S = fatigue stress amplitude (8.8) SEM = scanning electron microscopy

or microscope T = temperature Tc = Curie temperature (20.6) TC = superconducting critical

temperature (20.12) Tg = glass transition temperature

(13.10, 15.12) Tm = melting temperature TEM = transmission electron

microscopy or microscope TS = tensile strength (6.6) t = time tr = rupture lifetime (8.12) Ur = modulus of resilience (6.6) [uyw] = indices for a crystallographic

direction (3.9) [uvtw], [UVW] = indices for a crystallographic

direction, hexagonal crystals (3.9)

V = electrical potential difference (voltage) (17.2, 18.2) VC = unit cell volume (3.4) VC = corrosion potential (17.4) VH = Hall voltage (18.14) Vi = volume fraction of phase i (9.8) y = velocity vol% = volume percent Wi = mass fraction of phase i (9.8) wt% = weight percent (4.4) x = length x = space coordinate Y = dimensionless parameter or

function in fracture toughness expression (8.5)

y = space coordinate z = space coordinate a = lattice parameter: unit cell yz

interaxial angle (3.7) a, b, g = phase designations al = linear coefficient of thermal

expansion (19.3) b = lattice parameter: unit cell xz

interaxial angle (3.7) g = lattice parameter: unit cell xy

interaxial angle (3.7) g = shear strain (6.2) = precedes the symbol of a pa-

rameter to denote finite change P = engineering strain (6.2) P = dielectric permittivity (18.18)

List of Symbols xxiii

Pr = dielectric constant or relative permittivity (18.18)

P. s = steady-state creep rate (8.12) PT = true strain (6.7) h = viscosity (12.10) h = overvoltage (17.4) 2u = Bragg diffraction angle (3.16) uD = Debye temperature (19.2) l = wavelength of electromagnetic

radiation (3.16) m = magnetic permeability (20.2) mB = Bohr magneton (20.2) mr = relative magnetic permeability

(20.2) me = electron mobility (18.7) mh = hole mobility (18.10) n = Poissons ratio (6.5) n = frequency of electromagnetic

radiation (21.2) r = density (3.5) r = electrical resistivity (18.2) rt = radius of curvature at the tip of

a crack (8.5) s = engineering stress, tensile or

compressive (6.2) s = electrical conductivity (18.3) s* = longitudinal strength (compos-

ite) (16.5) sc = critical stress for crack propa-

gation (8.5) sfs = flexural strength (12.9) sm = maximum stress (8.5) sm = mean stress (8.7)

sm = stress in matrix at composite failure (16.5)

sT = true stress (6.7) sw = safe or working stress (6.12) sy = yield strength (6.6) t = shear stress (6.2) tc = fibermatrix bond strength/

matrix shear yield strength (16.4)

tcrss = critical resolved shear stress (7.5)

xm = magnetic susceptibility (20.2)

Subscripts c = composite cd = discontinuous fibrous

composite cl = longitudinal direction (aligned

fibrous composite) ct = transverse direction (aligned

fibrous composite) f = final f = at fracture f = fiber i = instantaneous m = matrix m, max = maximum min = minimum 0 = original 0 = at equilibrium 0 = in a vacuum

1

C h a p t e r 1 Introduction

A familiar item fabricated from three different material types is the beverage container. Beverages are marketed in aluminum (metal) cans (top), glass (ceramic) bottles (center), and plastic (polymer) bottles (bottom).

b

lickw

inke

l/Ala

my

iS

tock

phot

o/M

ark

Ole

ksiy

iS

tock

phot

o/Ji

ll C

hen

iS

tock

phot

o/M

ark

Ole

ksiy

b

lickw

inke

l/Ala

my

Learning ObjectivesAfter studying this chapter, you should be able to do the following:1. List six different property classifications of mate-

rials that determine their applicability.2. Cite the four components that are involved in

the design, production, and utilization of materi-als, and briefly describe the interrelationships between these components.

3. Cite three criteria that are important in the ma-terials selection process.

4. (a) List the three primary classifications of solid materials, and then cite the distinctive chemical feature of each.

(b) Note the four types of advanced materials and, for each, its distinctive feature(s).

5. (a) Briefly define smart material/system.(b) Briefly explain the concept of nanotechnol-

ogy as it applies to materials.

Materials are probably more deep seated in our culture than most of us realize. Transportation, housing, clothing, communication, recreation, and food productionvirtually every segment of our everyday lives is influenced to one degree or another by materials. Historically, the development and advancement of societies have been intimately tied to the members ability to produce and manipulate materials to fill their needs. In fact, early civilizations have been designated by the level of their materials development (Stone Age, Bronze Age, Iron Age).1

The earliest humans had access to only a very limited number of materials, those that occur naturally: stone, wood, clay, skins, and so on. With time, they discovered techniques for producing materials that had properties superior to those of the natural ones; these new materials included pottery and various metals. Furthermore, it was discovered that the properties of a material could be altered by heat treatments and by the addition of other substances. At this point, materials utilization was totally a selection process that involved deciding from a given, rather limited set of materials, the one best suited for an application by virtue of its characteristics. It was not until relatively recent times that scientists came to understand the relationships between the structural elements of materials and their proper-ties. This knowledge, acquired over approximately the past 100 years, has empowered them to fashion, to a large degree, the characteristics of materials. Thus, tens of thousands of dif-ferent materials have evolved with rather specialized characteristics that meet the needs of our modern and complex society, including metals, plastics, glasses, and fibers.

The development of many technologies that make our existence so comfortable has been intimately associated with the accessibility of suitable materials. An advance-ment in the understanding of a material type is often the forerunner to the stepwise progression of a technology. For example, automobiles would not have been possible without the availability of inexpensive steel or some other comparable substitute. In the contemporary era, sophisticated electronic devices rely on components that are made from what are called semiconducting materials.

1.1 HISTORICAL PERSPECTIVE

1The approximate dates for the beginnings of the Stone, Bronze, and Iron ages are 2.5 million bc, 3500 bc, and 1000 bc, respectively.

Sometimes it is useful to subdivide the discipline of materials science and engineering into materials science and materials engineering subdisciplines. Strictly speaking, materi-als science involves investigating the relationships that exist between the structures and

1.2 MATERIALS SCIENCE AND ENGINEERING

2

1.2 Materials Science and Engineering 3

properties of materials. In contrast, materials engineering involves, on the basis of these structureproperty correlations, designing or engineering the structure of a material to produce a predetermined set of properties.2 From a functional perspective, the role of a materials scientist is to develop or synthesize new materials, whereas a materials engi-neer is called upon to create new products or systems using existing materials and/or to develop techniques for processing materials. Most graduates in materials programs are trained to be both materials scientists and materials engineers.

Structure is, at this point, a nebulous term that deserves some explanation. In brief, the structure of a material usually relates to the arrangement of its internal components. Subatomic structure involves electrons within the individual atoms and interactions with their nuclei. On an atomic level, structure encompasses the organization of atoms or molecules relative to one another. The next larger structural realm, which contains large groups of atoms that are normally agglomerated together, is termed microscopic, mean-ing that which is subject to direct observation using some type of microscope. Finally, structural elements that can be viewed with the naked eye are termed macroscopic.

The notion of property deserves elaboration. While in service use, all materials are exposed to external stimuli that evoke some type of response. For example, a specimen subjected to forces experiences deformation, or a polished metal surface reflects light. A property is a material trait in terms of the kind and magnitude of response to a specific imposed stimulus. Generally, definitions of properties are made independent of mate-rial shape and size.

Virtually all important properties of solid materials may be grouped into six differ-ent categories: mechanical, electrical, thermal, magnetic, optical, and deteriorative. For each, there is a characteristic type of stimulus capable of provoking different responses. Mechanical properties relate deformation to an applied load or force; examples include elastic modulus (stiffness), strength, and toughness. For electrical properties, such as electrical conductivity and dielectric constant, the stimulus is an electric field. The thermal behavior of solids can be represented in terms of heat capacity and thermal conductivity. Magnetic properties demonstrate the response of a material to the ap-plication of a magnetic field. For optical properties, the stimulus is electromagnetic or light radiation; index of refraction and reflectivity are representative optical properties. Finally, deteriorative characteristics relate to the chemical reactivity of materials. The chapters that follow discuss properties that fall within each of these six classifications.

In addition to structure and properties, two other important components are in-volved in the science and engineering of materialsnamely, processing and perform-ance. With regard to the relationships of these four components, the structure of a material depends on how it is processed. Furthermore, a materials performance is a function of its properties. Thus, the interrelationship among processing, structure, prop-erties, and performance is as depicted in the schematic illustration shown in Figure 1.1. Throughout this text, we draw attention to the relationships among these four compo-nents in terms of the design, production, and utilization of materials.

We present an example of these processing-structure-properties-performance prin-ciples in Figure 1.2, a photograph showing three thin disk specimens placed over some printed matter. It is obvious that the optical properties (i.e., the light transmittance) of each of the three materials are different; the one on the left is transparent (i.e., virtually all of the

2Throughout this text, we draw attention to the relationships between material properties and structural elements.

Figure 1.1 The four components of the discipline of materials science and engineering and their interrelationship.

Processing Structure Properties Performance

4 Chapter 1 / Introduction

reflected light passes through it), whereas the disks in the center and on the right are, respec-tively, translucent and opaque. All of these specimens are of the same material, aluminum oxide, but the leftmost one is what we call a single crystalthat is, has a high degree of perfectionwhich gives rise to its transparency. The center one is composed of numerous and very small single crystals that are all connected; the boundaries between these small crystals scatter a portion of the light reflected from the printed page, which makes this ma-terial optically translucent. Finally, the specimen on the right is composed not only of many small, interconnected crystals, but also of a large number of very small pores or void spaces. These pores also effectively scatter the reflected light and render this material opaque.

Thus, the structures of these three specimens are different in terms of crystal boundaries and pores, which affect the optical transmittance properties. Furthermore, each material was produced using a different processing technique. If optical transmit-tance is an important parameter relative to the ultimate in-service application, the per-formance of each material will be different.

Why do we study materials? Many an applied scientist or engineer, whether mechani-cal, civil, chemical, or electrical, is at one time or another exposed to a design problem involving materials, such as a transmission gear, the superstructure for a building, an oil refinery component, or an integrated circuit chip. Of course, materials scientists and engineers are specialists who are totally involved in the investigation and design of materials.

Many times, a materials problem is one of selecting the right material from the thousands available. The final decision is normally based on several criteria. First, the in-service conditions must be characterized, for these dictate the properties required of the material. On only rare occasions does a material possess the maximum or ideal com-bination of properties. Thus, it may be necessary to trade one characteristic for another. The classic example involves strength and ductility; normally, a material having a high strength has only a limited ductility. In such cases, a reasonable compromise between two or more properties may be necessary.

A second selection consideration is any deterioration of material properties that may occur during service operation. For example, significant reductions in mechanical strength may result from exposure to elevated temperatures or corrosive environments.

1.3 WHY STUDY MATERIALS SCIENCE AND ENGINEERING?

Figure 1.2 Three thin disk specimens of aluminum oxide that have been placed over a printed page in order to demonstrate their differences in light-transmittance characteristics. The disk on the left is transparent (i.e., virtually all light that is reflected from the page passes through it), whereas the one in the center is translucent (meaning that some of this reflected light is transmitted through the disk). The disk on the right is opaquethat is, none of the light passes through it. These differences in optical properties are a consequence of differences in structure of these materials, which have resulted from the way the materials were processed.

Spec

imen

pre

para

tion,

P. A

. Les

sing

1.3 Why Study Materials Science and Engineering? 5

Finally, probably the overriding consideration is that of economics: What will the finished product cost? A material may be found that has the ideal set of properties but is prohibitively expensive. Here again, some compromise is inevitable. The cost of a finished piece also includes any expense incurred during fabrication to produce the desired shape.

The more familiar an engineer or scientist is with the various characteristics and structureproperty relationships, as well as the processing techniques of materials, the more proficient and confident he or she will be in making judicious materials choices based on these criteria.

Liberty Ship Failures

C A S E S T U D Y

The following case study illustrates one role that materials scientists and engineers are called upon to assume in the area of materials performance: analyze mechanical failures, determine their causes, and then propose appropriate measures to guard against future incidents.

The failure of many of the World War II Liberty ships3 is a well-known and dramatic example of the brittle fracture of steel that was thought to be duc-tile.4 Some of the early ships experienced structural damage when cracks developed in their decks and hulls. Three of them catastrophically split in half when cracks formed, grew to critical lengths, and then rap-idly propagated completely around the ships girths. Figure 1.3 shows one of the ships that fractured the day after it was launched.

Subsequent investigations concluded one or more of the following factors contributed to each failure5:

When some normally ductile metal alloys are cooled to relatively low temperatures, they be-come susceptible to brittle fracturethat is, they experience a ductile-to-brittle transition upon cooling through a critical range of temperatures. These Liberty ships were constructed of steel that

experienced a ductile-to-brittle transition. Some of them were deployed to the frigid North Atlan-tic, where the once ductile metal experienced brit-tle fracture when temperatures dropped to below the transition temperature.6

The corner of each hatch (i.e., door) was square; these corners acted as points of stress concentra-tion where cracks can form.

German U-boats were sinking cargo ships faster than they could be replaced using existing con-struction techniques. Consequently, it became necessary to revolutionize construction methods to build cargo ships faster and in greater numbers. This was accomplished using prefabricated steel sheets that were assembled by welding rather than by the traditional time-consuming riveting. Unfortunately, cracks in welded structures may propagate unimpeded for large distances, which can lead to catastrophic failure. However, when structures are riveted, a crack ceases to propagate once it reaches the edge of a steel sheet.

Weld defects and discontinuities (i.e., sites where cracks can form) were introduced by inexperi-enced operators.

3During World War II, 2,710 Liberty cargo ships were mass-produced by the United States to supply food and materials to the combatants in Europe.4Ductile metals fail after relatively large degrees of permanent deformation; however, very little if any permanent deformation accompanies the fracture of brittle materials. Brittle fractures can occur very suddenly as cracks spread rapidly; crack propagation is normally much slower in ductile materials, and the eventual fracture takes longer. For these reasons, the ductile mode of fracture is usually preferred. Ductile and brittle fractures are discussed in Sections 8.3 and 8.4.5Sections 8.2 through 8.6 discuss various aspects of failure.6This ductile-to-brittle transition phenomenon, as well as techniques that are used to measure and raise the critical temperature range, are discussed in Section 8.6.

(continued)


Remedial measures taken to correct these prob-lems included the following:

Lowering the ductile-to-brittle temperature of the steel to an acceptable level by improving steel quality (e.g., reducing sulfur and phosphorus im-purity contents).

Rounding off hatch corners by welding a curved reinforcement strip on each corner.7

Installing crack-arresting devices such as riveted straps and strong weld seams to stop propagating cracks.

Improving welding practices and establishing weld-ing codes.

In spite of these failures, the Liberty ship program was considered a success for several reasons, the pri-mary reason being that ships that survived failure were able to supply Allied Forces in the theater of operations and in all likelihood shortened the war. In addition, structural steels were developed with vastly improved resistances to catastrophic brittle fractures. Detailed analyses of these failures advanced the understand-ing of crack formation and growth, which ultimately evolved into the discipline of fracture mechanics.

Figure 1.3 The Liberty ship S.S. Schenectady, which, in 1943, failed before leaving the shipyard.(Reprinted with permission of Earl R. Parker, Brittle Behavior of Engineering Structures, National Academy of Sciences, National Research Council, John Wiley & Sons, New York, 1957.)

7The reader may note that corners of windows and doors for all of todays marine and aircraft structures are rounded.

Solid materials have been conveniently grouped into three basic categories: metals, ce-ramics, and polymers, a scheme based primarily on chemical makeup and atomic struc-ture. Most materials fall into one distinct grouping or another. In addition, there are the composites that are engineered combinations of two or more different materials. A brief explanation of these material classifications and representative characteristics is offered next. Another category is advanced materialsthose used in high-technology applica-tions, such as semiconductors, biomaterials, smart materials, and nanoengineered mate-rials; these are discussed in Section 1.5.

1.4 CLASSIFICATION OF MATERIALS

Tutorial Video:What are the

Different Classes of Materials?

1.4 Classification of Materials 7

MetalsMetals are composed of one or more metallic elements (e.g., iron, aluminum, copper, titanium, gold, nickel), and often also nonmetallic elements (e.g., carbon, nitrogen, oxygen) in relatively small amounts.8 Atoms in metals and their alloys are arranged in a very orderly manner (as discussed in Chapter 3) and are relatively dense in comparison to the ceramics and polymers (Figure 1.4). With regard to mechanical characteristics, these materials are relatively stiff (Figure 1.5) and strong (Figure 1.6), yet are ductile (i.e., capable of large amounts of deformation without fracture), and are resistant to fracture (Figure 1.7), which accounts for their widespread use in structural applications. Metallic materials have large numbers of nonlocalized electronsthat is, these electrons are not bound to particular atoms. Many properties of metals are directly attributable to these electrons. For example, metals are extremely good conductors of electricity

8The term metal alloy refers to a metallic substance that is composed of two or more elements.

Den

sity

(g/

cm3 )

(lo

garit

hmic

sca

le)

40

20

1086

4

2

1.00.80.6

0.2

0.4

0.1

Metals

Platinum

Silver

CopperIron/Steel

Titanium

Aluminum

Magnesium

Composites

GFRC

CFRC

Woods

Polymers

PTFE

PVCPSPERubber

ZrO2Al2O3

SiC,Si3N4GlassConcrete

Ceramics

Figure 1.4Bar chart of room-

temperature density values for various metals, ceramics,

polymers, and composite materials.


temperature stiffness (i.e., elastic modulus)

values for various metals, ceramics,

polymers, and composite materials. 10

1.0

0.1

100

1000

0.01

0.001

Stiff

ness

[el

astic

(or

You

ngs

) m

odul

us (

in u

nits

of

giga

pasc

als)

] (lo

garit

hmic

sca

le)

Composites

GFRC

CFRC

WoodsPolymers

PVC

PTFE PE

Rubbers

PS, Nylon

Metals

TungstenIron/Steel

AluminumMagnesium

Titanium

Ceramics

SiCAI2O3

Si3N4ZrO2

GlassConcrete

Tutorial Video:Metals


Str

engt

h (t

ensi

le s

tren

gth,

in u

nits

of

meg

apas

cals

) (lo

garit

hmic

sca

le) 1000

100

10

Nylon

PS

PE

PVC

PTFE

Polymers

Steelalloys

Gold

Aluminumalloys

Cu,Tialloys

Metals

CFRCGFRC

Composites

WoodsGlass

Si3N4

SiC

Ceramics

Al2O3


temperature strength (i.e., tensile strength)

values for various metals, ceramics,


Res

ista

nce

to F

ract

ure

(fra

ctur

e to

ughn

ess,

in u

nits

of

MPa

m)

(loga

rithm

ic s

cale

)

100

10

1.0

0.1

Composites

GFRCCFRC

Wood

Nylon

Polymers

PolystyrenePolyethylene

Polyester

Al2O3SiC

Si3N4

Glass

Concrete

Ceramics

Metals

SteelalloysTitanium

alloys

Aluminumalloys

Figure 1.7Bar chart of

room-temperature resistance to fracture (i.e., fracture tough-

ness) for various metals, ceramics,


(Reprinted from Engineering Materials 1: An Introduction to

Properties, Applications and Design, third

edition, M. F. Ashby and D. R. H. Jones, pages

177 and 178, Copyright 2005, with permission

from Elsevier.)

(Figure 1.8) and heat, and are not transparent to visible light; a polished metal surface has a lustrous appearance. In addition, some of the metals (i.e., Fe, Co, and Ni) have desirable magnetic properties.

Figure 1.9 shows several common and familiar objects that are made of metallic materials. Furthermore, the types and applications of metals and their alloys are discussed in Chapter 11.

CeramicsCeramics are compounds between metallic and nonmetallic elements; they are most fre-quently oxides, nitrides, and carbides. For example, common ceramic materials include aluminum oxide (or alumina, Al2O3), silicon dioxide (or silica, SiO2), silicon carbide (SiC), silicon nitride (Si3N4), and, in addition, what some refer to as the traditional ceramicsthose composed of clay minerals (e.g., porcelain), as well as cement and glass. With regard to me-chanical behavior, ceramic materials are relatively stiff and strongstiffnesses and strengths are comparable to those of the metals (Figures 1.5 and 1.6). In addition, they are typically very hard. Historically, ceramics have exhibited extreme brittleness (lack of ductility) and are highly susceptible to fracture (Figure 1.7). However, newer ceramics are being engineered to have improved resistance to fracture; these materials are used for cookware, cutlery, and

Tutorial Video:Ceramics


Elec

tric

al C

ondu

ctiv

ity (

in u

nits

of

reci

proc

al

ohm

-met

ers)

(lo

garit

hmic

sca

le)

108

104

1

1012

108

104

1016

1020

Ceramics Polymers

Semiconductors

MetalsFigure 1.8Bar chart of room-

temperature electrical

conductivity ranges for metals, ceramics,

polymers, and semiconducting

materials.

Figure 1.9 Familiar objects made of metals and metal alloys (from left to right): silverware (fork and knife), scissors, coins, a gear, a wedding ring, and a nut and bolt.

even automobile engine parts. Furthermore, ceramic materials are typically insulative to the passage of heat and electricity (i.e., have low electrical conductivities, Figure 1.8) and are more resistant to high temperatures and harsh environments than are metals and polymers. With regard to optical characteristics, ceramics may be transparent, translucent, or opaque (Figure 1.2), and some of the oxide ceramics (e.g., Fe3O4) exhibit magnetic behavior.

Several common ceramic objects are shown in Figure 1.10. The characteristics, types, and applications of this class of materials are also discussed in Chapters 12 and 13.

PolymersPolymers include the familiar plastic and rubber materials. Many of them are organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic ele-ments (i.e., O, N, and Si). Furthermore, they have very large molecular structures, often chainlike in nature, that often have a backbone of carbon atoms. Some common and familiar polymers are polyethylene (PE), nylon, poly(vinyl chloride) (PVC), polycar-bonate (PC), polystyrene (PS), and silicone rubber. These materials typically have low densities (Figure 1.4), whereas their mechanical characteristics are generally dissimilar to those of the metallic and ceramic materialsthey are not as stiff or strong as these

W

illia

m D

. Cal

liste

r, J

r.


other material types (Figures 1.5 and 1.6). However, on the basis of their low densities, many times their stiffnesses and strengths on a per-mass basis are comparable to those of the metals and ceramics. In addition, many of the polymers are extremely ductile and pliable (i.e., plastic), which means they are easily formed into complex shapes. In general, they are relatively inert chemically and unreactive in a large number of environ-ments. One major drawback to the polymers is their tendency to soften and/or decom-pose at modest temperatures, which, in some instances, limits their use. Furthermore, they have low electrical conductivities (Figure 1.8) and are nonmagnetic.

Figure 1.11 shows several articles made of polymers that are familiar to the reader. Chapters 14 and 15 are devoted to discussions of the structures, properties, applications, and processing of polymeric materials.

Figure 1.10 Common objects made of ceramic materials: scissors, a china teacup, a building brick, a floor tile, and a glass vase.

Figure 1.11 Several common objects made of polymeric materials: plastic tableware (spoon, fork, and knife), billiard balls, a bicycle helmet, two dice, a lawn mower wheel (plastic hub and rubber tire), and a plastic milk carton.

W

illia

m D

. Cal

liste

r, J

r.

Will

iam

D. C

allis

ter,

Jr.

Tutorial Video:Polymers


CompositesA composite is composed of two (or more) individual materials that come from the categories previously discussedmetals, ceramics, and polymers. The design goal of a composite is to achieve a combination of properties that is not displayed by any single material and also to incorporate the best characteristics of each of the component ma-terials. A large number of composite types are represented by different combinations of metals, ceramics, and polymers. Furthermore, some naturally occurring materials are compositesfor example, wood and bone. However, most of those we consider in our discussions are synthetic (or human-made) composites.

One of the most common and familiar composites is fiberglass, in which small glass fibers are embedded within a polymeric material (normally an epoxy or polyester).9 The glass fibers are relatively strong and stiff (but also brittle), whereas the polymer is more flexible. Thus, fiberglass is relatively stiff, strong (Figures 1.5 and 1.6), and flexible. In addition, it has a low density (Figure 1.4).

Another technologically important material is the carbon fiberreinforced polymer (CFRP) compositecarbon fibers that are embedded within a polymer. These materials are stiffer and stronger than glass fiberreinforced materials (Figures 1.5 and 1.6) but more expensive. CFRP composites are used in some aircraft and aerospace applications, as well as in high-tech sporting equipment (e.g., bicycles, golf clubs, tennis rackets, skis/snowboards) and recently in automobile bumpers. The new Boeing 787 fuselage is pri-marily made from such CFRP composites.

Chapter 16 is devoted to a discussion of these interesting composite materials.

Carbonated Beverage Containers

C A S E S T U D Y

One common item that presents some interesting material property requirements is the container for carbonated beverages. The material used for this application must satisfy the following constraints: (1) provide a barrier to the passage of carbon dioxide, which is under pressure in the container; (2) be non-toxic, unreactive with the beverage, and, preferably, recyclable; (3) be relatively strong and capable of surviving a drop from a height of several feet when containing the beverage; (4) be inexpensive, includ-ing the cost to fabricate the final shape; (5) if opti-cally transparent, retain its optical clarity; and (6) be capable of being produced in different colors and/or adorned with decorative labels.

All three of the basic material typesmetal (aluminum), ceramic (glass), and polymer (polyes-ter plastic)are used for carbonated beverage con-tainers (per the chapter-opening photographs). All of these materials are nontoxic and unreactive with

beverages. In addition, each material has its pros and cons. For example, the aluminum alloy is relatively strong (but easily dented), is a very good barrier to the diffusion of carbon dioxide, is easily recycled, cools beverages rapidly, and allows labels to be painted onto its surface. However, the cans are op-tically opaque and relatively expensive to produce. Glass is impervious to the passage of carbon dioxide, is a relatively inexpensive material, and may be recy-cled, but it cracks and fractures easily, and glass bot-tles are relatively heavy. Whereas plastic is relatively strong, may be made optically transparent, is inex-pensive and lightweight, and is recyclable, it is not as impervious to the passage of carbon dioxide as aluminum and glass. For example, you may have no-ticed that beverages in aluminum and glass contain-ers retain their carbonization (i.e., fizz) for several years, whereas those in two-liter plastic bottles go flat within a few months.

9Fiberglass is sometimes also termed a glass fiberreinforced polymer composite (GFRP).

Tutorial Video:Composites


Materials utilized in high-technology (or high-tech) applications are sometimes termed advanced materials. By high technology, we mean a device or product that operates or functions using relatively intricate and sophisticated principles, including electronic equipment (camcorders, CD/DVD players), computers, fiber-optic systems, spacecraft, aircraft, and military rocketry. These advanced materials are typically traditional mate-rials whose properties have been enhanced and also newly developed, high-performance materials. Furthermore, they may be of all material types (e.g., metals, ceramics, polymers) and are normally expensive. Advanced materials include semiconductors, biomaterials, and what we may term materials of the future (i.e., smart materials and nanoengineered materials), which we discuss next. The properties and applications of a number of these advanced materialsfor example, materials that are used for lasers, integrated circuits, magnetic information storage, liquid crystal displays (LCDs), and fiber opticsare also discussed in subsequent chapters.

SemiconductorsSemiconductors have electrical properties that are intermediate between those of electrical conductors (i.e., metals and metal alloys) and insulators (i.e., ceramics and polymers)see Figure 1.8. Furthermore, the electrical characteristics of these ma-terials are extremely sensitive to the presence of minute concentrations of impurity atoms, for which the concentrations may be controlled over very small spatial regions. Semiconductors have made possible the advent of integrated circuitry that has totally revolutionized the electronics and computer industries (not to mention our lives) over the past three decades.

BiomaterialsBiomaterials are employed in components implanted into the human body to replace dis-eased or damaged body parts. These materials must not produce toxic substances and must be compatible with body tissues (i.e., must not cause adverse biological reactions). All of the preceding materialsmetals, ceramics, polymers, composites, and semiconductorsmay be used as biomaterials.

Smart MaterialsSmart (or intelligent) materials are a group of new and state-of-the-art materials now being developed that will have a significant influence on many of our technologies. The adjective smart implies that these materials are able to sense changes in their environ-ment and then respond to these changes in predetermined mannerstraits that are also found in living organisms. In addition, this smart concept is being extended to rather sophisticated systems that consist of both smart and traditional materials.

Components of a smart material (or system) include some type of sensor (which detects an input signal) and an actuator (which performs a responsive and adaptive function). Actuators may be called upon to change shape, position, natural frequency, or mechanical characteristics in response to changes in temperature, electric fields, and/or magnetic fields.

Four types of materials are commonly used for actuators: shape-memory alloys, pi-ezoelectric ceramics, magnetostrictive materials, and electrorheological/magnetorheo-logical fluids. Shape-memory alloys are metals that, after having been deformed, revert to their original shape when temperature is changed (see the Materials of Importance box following Section 10.9). Piezoelectric ceramics expand and contract in response to an applied electric field (or voltage); conversely, they also generate an electric field when their dimensions are altered (see Section 18.25). The behavior of magnetostrictive materials is analogous to that of the piezoelectrics, except that they are responsive to

1.5 ADVANCED MATERIALS

1.5 Advanced Materials 13

magnetic fields. Also, electrorheological and magnetorheological fluids are liquids that experience dramatic changes in viscosity upon the application of electric and magnetic fields, respectively.

Materials/devices employed as sensors include optical fibers (Section 21.14), piezoelec-tric materials (including some polymers), and microelectromechanical systems (MEMS; Section 13.9).

For example, one type of smart system is used in helicopters to reduce aerodynamic cockpit noise created by the rotating rotor blades. Piezoelectric sensors inserted into the blades monitor blade stresses and deformations; feedback signals from these sensors are fed into a computer-controlled adaptive device that generates noise-canceling antinoise.

NanomaterialsOne new material class that has fascinating properties and tremendous technological promise is the nanomaterials, which may be any one of the four basic typesmetals, ceramics, polymers, or composites. However, unlike these other materials, they are not distinguished on the basis of their chemistry but rather their size; the nano prefix denotes that the dimensions of these structural entities are on the order of a nanometer (10-9 m)as a rule, less than 100 nanometers (nm; equivalent to the diameter of ap-proximately 500 atoms).

Prior to the advent of nanomaterials, the general procedure scientists used to understand the chemistry and physics of materials was to begin by studying large and complex structures and then investigate the fundamental building blocks of these struc-tures that are smaller and simpler. This approach is sometimes termed top-down science. However, with the development of scanning probe microscopes (Section 4.10), which permit observation of individual atoms and molecules, it has become possible to design and build new structures from their atomic-level constituents, one atom or molecule at a time (i.e., materials by design). This ability to arrange atoms carefully provides op-portunities to develop mechanical, electrical, magnetic, and other properties that are not otherwise possible. We call this the bottom-up approach, and the study of the properties of these materials is termed nanotechnology.10

Some of the physical and chemical characteristics exhibited by matter may experi-ence dramatic changes as particle size approaches atomic dimensions. For example, materials that are opaque in the macroscopic domain may become transparent on the nanoscale; some solids become liquids, chemically stable materials become combustible, and electrical insulators become conductors. Furthermore, properties may depend on size in this nanoscale domain. Some of these effects are quantum mechanical in origin, whereas others are related to surface phenomenathe proportion of atoms located on surface sites of a particle increases dramatically as its size decreases.

Because of these unique and unusual properties, nanomaterials are finding niches in electronic, biomedical, sporting, energy production, and other industrial applications. Some are discussed in this text, including the following:

Catalytic converters for automobiles (Materials of Importance box, Chapter 4) NanocarbonsFullerenes, carbon nanotubes, and graphene (Section 13.9) Particles of carbon black as reinforcement for automobile tires (Section 16.2) Nanocomposites (Section 16.16) Magnetic nanosize grains that are used for hard disk drives (Section 20.11) Magnetic particles that store data on magnetic tapes (Section 20.11)

10One legendary and prophetic suggestion as to the possibility of nanoengineered materials was offered by Richard Feynman in his 1959 American Physical Society lecture titled Theres Plenty of Room at the Bottom.


Whenever a new material is developed, its potential for harmful and toxicological interactions with humans and animals must be considered. Small nanoparticles have ex-ceedingly large surface areatovolume ratios, which can lead to high chemical reactivi-ties. Although the safety of nanomaterials is relatively unexplored, there are concerns that they may be absorbed into the body through the skin, lungs, and digestive tract at relatively high rates, and that some, if present in sufficient concentrations, will pose health riskssuch as damage to DNA or promotion of lung cancer.

In spite of the tremendous progress that has been made in the discipline of materials science and engineering within the past few years, technological challenges remain, in-cluding the development of even more sophisticated and specialized materials, as well as consideration of the environmental impact of materials production. Some comment is appropriate relative to these issues so as to round out this perspective.

Nuclear energy holds some promise, but the solutions to the many problems that remain necessarily involve materials, such as fuels, containment structures, and facilities for the disposal of radioactive waste.

Significant quantities of energy are involved in transportation. Reducing the weight of transportation vehicles (automobiles, aircraft, trains, etc.), as well as increasing engine op-erating temperatures, will enhance fuel efficiency. New high-strength, low-density struc-tural materials remain to be developed, as well as mat