FUNDMNT MATERLS SCI
FUNDMNT MATERLS SCI MSE 170
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This 51 page Class Notes was uploaded by Foster Hahn IV on Wednesday September 9, 2015. The Class Notes belongs to MSE 170 at University of Washington taught by Miqin Zhang in Fall. Since its upload, it has received 34 views. For similar materials see /class/192201/mse-170-university-of-washington in Materials Science Engineering at University of Washington.
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Chapter 6 Mechanical properties of metals Outline D Elastic recovery during plastic deformation D Hardness El Variability of material properties III Designsafety factors Elastic recovery during plastic deformation III Schematic tensile stress strain diagram showing elastic strain recove Stress 7 l6 Elastic strain recovery Ductility EL Plastic tensile strain at failure EL LIL X 100 0 smaller EL Engineering tensile stress 6 lar er EL 9 Lo A L Adapted mm Fig 613 Callister7e Engineering tensile strain 9 A A Another ductility measure RA o f 100 0 True stress amp strain Note SA changes when sample stretched El True stress 67 FA 67 618 s lnE e 8 n18 El True Strain T O T True M 8 2 5 Engineering Strain 4 Hardening An increase in cydue to plastic deformation U large hardening 0y 1 0y0 small hardening S Curve fit to the stressstrain response hardening exponent n 015 UT K some steels to n 05 some coppers 5 true stress FA true strain nLLo Hardness El Hardnss a mmsure ofa material39s resistance to apply known forcel measure size localized plastic 1 to 10009 of indem ner deformation or 39 eg u 1 39quot39quot Sphere removm load El Simple and inexpensive cracking in comprssion Smaller indents d mean largermrdness El Non dstrucuve easily turd hrassesv machined lo cutlingl nitrided D Can obtain other P39ast39 Alalloys steels rile hools steels d39a39m39 mechanical proper s Increasing hardness Hardness tests El Mohs scale 1talclt2Gypsumlt3cacitelt4fuorlte lt10diamond III 1m llanlncss39 39 g39ruhniqm Shape nlndzulnliun Farm for m hmquot m up n W mm quotmm mm Brmell lllrnnl sphere l D a I39 HE emu or rel u llt mva 1 lungslen cmude d e Vlckers Dillmnnd ll 11 1quot HV LK MPLl mlcmhardness pymllid u Knnnp Diamond mrcmmmnell gymInd E quot I39 HK MW 5 Rockwell and 39 Dln nond 12D 6n kg Super cml cane mu kg we Rockwell ll Ml in lin kgl hamster a steel sphere li l in kg Super clal Rockwell as l Hardness tests continue D Rockwell and super cial rockwe Lllvlvvfm llmLmllllrIIm39ull No major sample dama e i Each scale runs to 130 but only useful in range 20100 Minor load 10 kg 0 Major load 60 A 100 B amp 150 C kg 0A diamond B 116 in ball iamond mu ml MlIurlu39ml Hm Innll mum y El Examples 2 37mm 7 Imzulvr IIuJurIuml A 80HRB60 HR30W El 20lthardnesslt100 Hardness tests continue nw El Brinell 10mm sphere of steel or mewWm tungsten carbide El Knoop and vickers mm microhardness mm m WW Lnnu III Hardness conversion 3933 r m 32m MD mm D In S k lullth mm 39 tall n 2 quot 573 3 394quot WW quotmlquot m quot mm W 0 5 ni39l39lil l r Correlation between hardness and tensile strength El Relations between hardness and tensile strength for steel brass and cast iron 60 70 80 90 100 HRB 20 so El For most steels TS MPa345xHB Ts psi500xHB Tenslle slmlglh MP3 Rockwell hardness 40 cm lmn nodulall l 400 Erlnell llal39drless number TellSlle strength 10 psl Example El Btimate the Bn39nell and Rockwell hardnesses for brass and carbon s ee llu mm mm mum lo m Mammy Example El Estimate the Brinell and Rockwell hardnesses for brass and carbon steel Tuuilz nmmninhammm whim an Variability of material properties El Factors that lead to scatter in measured material properties El The average III The standard deviation x r141 where n is the number of data points Example El Determine the average and standard deviation of tensile strength mum umm r w l 3 39 Vi 1 K X v A Ts V X W Sin 39 7 4 T3 51H 11 w quot w x I il kll u I I x TVS Elmx H 1 W l l 1 L 4 Am lT i 3391 ms lquotgt 45 iquot l 7 l H my 4 h tl u Designsafety factors Design uncertainties mean we do not push the limit Factor of safety N Often N is 6y between 6working W 12 and 4 0 Ex Calculate a diameter d to ensure that yield does not occur in the 1045 carbon steel rod below Use a factor of safety of 5 6 y 1045 plain 6Worklng N carbon steel lLo 220000N 39 11 d2 4 F 220000N Summary 0 Stress and strain These are sizeindependent measures of load and displacement respectively 0 Elastic behavior This reversible behavior often shows a linear relation between stress and strain To minimize deformation select a material with a large elastic modulus E or G 0 Plastic behavior This permanent deformation behavior occurs when the tensile or compressive uniaxial stress reaches 6y 0 Toughness The energy needed to break a unit volume of material 0 Ductility The plastic strain atfailure Mechanical prop FeC System 1 I Effect of wt C 397 5 Pearlite med ferrite softquotquotquotK 39 Colt 076 wt C CO gt 076 wt C Hypoeutectoid Hypereutectoid H H I L39 H TSWPEH 100 N n EL W 7 80 A VSMPa 100 g a 900 39 r dness 3 740g 7007 gt 50 g 5007 0 g 7 E 300 a mum Hir E 05 owim 0 05 CW More wt C TS and VS increase EL decreases o 0 Mechanical prop FeC system 2 Ei Fine vs coarse pearlite vs spheroidite u u u n4 y n4 y 320 39 fine g spheroidite m peariite lt 60 g 240 coarse g g peariite g E 5pneroidite g 39 i 160 2 30 coarse g D peariite ca 39 fine 8039IIIIIIIII lllllllllpearme 05 05 wtC wic Hardness ne gt coarse gt spheroidite RA ne lt coarse lt spheroidite Mechanical Prop Fe C system 3 El Fine Pearlite vs Martensite Hypo Hyper a 600 martensite g E g 400 5 13 200 fine pearlite n I I I I I I I 05 WtC1 Hardness fine pearlite ltlt martensite Tempering martensite III reduces brittleness of martensite El reduces internal stress caused by quenching TSMPa YSMPa 1800 1600 1400 1200 1000 800 30 400 600 Tempering T C III produces extremely small Fe3C particles surrounded y on El decreases TS Y8 but increases RA Summary Processing options Austenite y slow cool Bainite Martensite a FeSC platesneedles BOT phase diffusionless transformation Pearlite a FeSC layers a proeutectoid phase Martensite T Martensite n bainite E Tempered i E MartenSIte g fine pearlite g a very fine U coarse pearlite CI Feac particles l spheroidite 39 Chap11Applioations and processing of metal alloys Metal Alloys Feru s Nonferrou s Steels Castlrons on Al Mg Ti lt1 4wtC 345wtC microstructure T C 39 1600 ferrlte graphite cementite 1400 39 1200 y 43 C LFe30 auslenile Eutectic 1000 4 0 2 yFe30 I132 3 727 C Feac ferrite Eutectoid emanate 600 011 1Feac 400 l 39 39 39 o 1 2 a 4 5 s 67 W on WIDu c Steels Low Alloy High Alloy l I low carbon med carbon high carbon lt025wtC 025C 6wtC 0614wtC Name plain HSLA plain heat plain tool aus e mm H treatable n stalnlness ll I I Additions none cr v or N39 dr V NL Mo none MP none Mo w Cr ll Mo Example 1010 4310 1040 4340 1095 4199 394 Hardenability Q 1 1 4 4l 9 0 139 139 H 0 EL 0 4 I l I l E I ll Uses auto bridges crank pistons wear drills h9hT uc towers shafts gears applic saws appllc sheet press bolts dies lurblnes vessels hammers applic furnaces I I V corros increasing strength cost decreasing duc39tility res39s n Nonferrous alloys Cu Alloys AI Alloys Brass Zn is subst impurity lower p 27gl cm3 costume jewelry coins cuy Mgtsi Mn Zn additions corrosion resistant sglid so or precip Bronze Sn Al Si Ni ar subst impurity 39 bushings landing geao CuBe precip hardened for strength i Ti A loys Iowe lagM3 strengthened struct aircraft parts amp packaging NonFerrou Allo Refractory metals A high melting T V3719 Estes 39 Noblemetals39 Nb MOT w 39I a Treactiveltat high Tquot A9 AU Pt space applic ox id 39quotcorr resistant Chapter 12 Structures and properties of ceramics El Bonding in ceramics El Imperfection in ceramics El Electric properties of ceramics El Ceramic phase diagrams El Brittle fracture of ceramics El Stressstrain behavior El Mechanisms of plastic deformation Ceramic bonding El Bonding Mostly ionic some covalent u ionic character increases with difference in electronegativity Table of Electronegativities Imperfections in ceramics ElSchottky defects a paired set of cation and anion vacancies DFrenkel defects an atom from a lattice site to an interstitial position 590 Q39Q i i 900 2W U 9 a 0523 Q 090 Q U WFrenkel owe oooou Point defects in ionic crystals El Impurities must also satisfy charge balance Ex NaCl Na0 or o Substitutional cation impurity a2 odo Na o 0 initial geometry Ca2impurity resulting geometry 0 Substitutional anion impurity anio vacancy 03 0 I I initial geometry Oz39impurity resulting geometry Point defects in ionic crystals El Defect examples for other ionic crystal systems lZlIn simple ionic crystals both Schottky and Frenkel defects occur but the concentration of one type generally exceeds that of the other 0 Schottky defects dominate in alkali halides Cation Frenkel defects dominate in AgCl and AgBr Anion Frenkel defects dominate in Can and fluorites Electric properties El Electrical conductivity the mobility of charged point defects 0n e Ea tn emex p KT Since the cation vacancy is more mobile than anion vacancy n defect concentration e charge p mobility Electric properties continue El Electrical conductivity Ln 039 l 0 Region I Schottky defects E3 Em 12EE 0 Region II Cation vacancies E3 Em 0 Region III cation vacancies impurity ions clustering of defects i l l l l l 1T Effect of temperature on electrical conductivity of a NaCI crystal containing a small cone of a divalent cation Ceramic phase diagram D Ale339Cr203 20 80 1 o 22952 5393 o Isomorphous o In solid solution Al3 m substitute Cr3 Al and Cr should have have similar mo radius and same charge 20455395 7 Both N203 and CrZO3 20007 N203Clzoasulldsolwull have the same crystal structure 20 no 60 an 1 0 Al 0 i Cr 0 2 3 Composition 00 0203 2 3 Composition mm 0203 40 Liquid 4000 0 Temperature l C Teniperaturef r 7 3800 7 3500 Ceramic phase diagram Composition mowe Alzozi DThe MgZO39AIZOE 2 0 4 0 6 0 8 0 system El Intermediate M phase spinel compound lvlgll o 5 2400 i Mm 2000 w m o 0 Temperature r 0 Temperature l r w o o o ngO 5 NigAlZO lssi Mgmzf 55 E o o m 203 1200 o 50 ng07 Composition was Alzoi Aizoji Stressstrain behavior El Flectural testing replace tensile testing D Reasons for not a standard tension test 0 difficult to prepare and test specimens having a required geometry 0 difficult to grip brittle materials without fracturing them 0 ceramics fail after only about 01 strain and samples are difficult to align without experiencing bending stress Measuring elastic modulus El Room T behavior is usually elastic with brittle failure 3Point Bend Testing often used El Tensile tests are dif cult for brittle materials F cross section B midpoint de ect ion III Determine elastic modulus according to F L3 F L3 slope i 5 4in3 5 1271R4 5 rect circ 5 cross cross linearelastic behavior SBCtiOn section Measuring strength El 3point bend test to measure room T strength cross section F location ofmax tension El Flexural strength Typ values 6 7 fan 7 1 5FmaXL 7 FmaX L Material ofs MPa EGPa fs 5 i 2 i 3 SI nitride 7001000 300 git R Si carbide 550860 430 Fma F 39 Al oxide 275550 390 Dglaa gr Cali52l955 max 10 Elastic behavior El Typical stress 250 7 X strain behavior to fracture for 200 7 i 30 aluminum oxide Aluminum oxide and glass Stress MPa i m 0 Stress 103 psi Mechanisms of plastic deformation El Crystalline ceramics are brittle Covalent bonds are relatively strong There are limited numbers of slip systems Dislocation structures are complex El Noncrystalline ceramics Plastic deformation does not occur by dislocation motion for noncrystalline ceramics Viscosity is a measure of of noncrystalline material s resistance to deformation Influence of porosity on mechanical behavior El EE0119P09P2 El 05 60 exp nP n no a u n z u z o u a Valumz m N am a 4 a 5 mm mm miniilv Hardness 39I39nlulx lflJi Approximate Klmop lill39lllll h h Hill 5 luzul l or Sewn Ivrunliv l 39 s lpH39Iu39iulult39 llulrriul Kmmp Ilm39tlmws Diamond carbon Boron Carbide BAC 2800 Silicon carbide SiC 2500 Tungsten carbide WC 2100 Aluminum oxide A1309 lell Quunz SiOl mo G 55 Summary Ceramic materials have mostly ironic bondingamp some covalent bonding Defects must preserve charge neutrality have a concentration that varies exponentially wlT Room T mechanical response is elastic but fracture is brittle with negligible ductility Elevated T creep properties are generally superior to those of metals and polymers Chapter 6 Mechanical properties of metals Outline III Introduction III Concepts of stress and strain III Elastic deformation 0 Stressstrain behavior 0 Elastic properties of materials III Plastic deformation 0 Yield and yield strength 0 Ductility o Resilienoe o Toughness Concepts of stress and strain El Tension compression shear and torsion Stressstrain testing III Tension tests Load ce engineering stress 0 L A0 engineering strain Ho 8 IO IO Reduceq Iseckion k 21 7 I 339 l39 quot g 3 Diameter 7 3 7 lt gt a Radius Gauge length III Compression tests Shear stress El Shear and torsional tests Shear stress F r G A0 7 Shear strain y tane gt El Geometric considerations of the stress state 7 i 1 Elastic deformation 1 Initial 2 Small load 3 Unload bonds stretch return to i initial F F Linear elastic Elastic means reversible NonLinear elastic Linear elastic properties El Modulus of Elasticity E also known as Young39s modulus El Hooke39s Law GE8 Stressstrain behavior El Stressstrain for linear elastic deformation El Stressstrain for nonlinear elastic deformation Siress Siane modulus N mastitity Strain Stressstrain behaviorcontinue El Modulus of elasticity E is proportional to dFdrr El Slope of stress strain plot which is proportional to the elastic modulus depends on bond strength of met Stroneg bonded Separation r Weakly bonded Other elastic properties M El Elastic Shear modulus 6 Simple torsion quot 39 G 7 test M El Elastic Bulk P P modulus K P P A V A V K V V O 0 K 5 pressure quotquotquot quot test lnit El Special relations for isotropic materials VOI V E E Vol ohg G K AV 21 v 31 2v Comparison of Young s moduli Eceramics gt Emetals gtgt Epolymers Diamond Si carbide t mild Carbunlibersunlv W e EGPa g m tswgta FRElllribersi39 tE E a lws la mammmnl u vcgqy g d IGlassrsuda wagggmgm l ganeswmi nsFHEllirinersr oCuncrete iEFRE GEW i iimmr FRELLflelS ggasmr MFPEwinersi i FE Po 39Epuxvuan ERE WVEIEIdl Valli 39PTFE J39g Comparison of yield strength 0yceramics gtgt 0ymetals gtgt Oy polymers Graphite A gab Ceramics Polymers 0 ggrss39t65 ys Semi ond UUU 39Steelmmn l A1000 E m Wig35quot 9 wearng E V 400 39Steelmmna g steeimu2n0 8 39 gt 300 d gt0 b 39Al BEIle 5 g g 200 Steelmu nhr 3 g 5 grursgaw g E C Li 15D 0 e B 8 100 gg g E s as 2 I I 50 39Al6EIEl5 E 40 E 9 so i gt39 20 E 10 Elastic properties of materials El Poisson s ratio metals v 033 ceramics v 025 polymers v 040 Units E GPa or psi 2 v dimensionless v2 Plastic Deformation Metals l 5elastic plastic F linear linear Plastic means permanent elastic gt 5pastic Plastic deformation yield and yield strength El Yielding El Proportional limit El Yield strength Tensile strength El Tensile strength the stress at the Imum on the engineering Ts stressstrain curve El Metals occurs when noticeable necking starts El Ceramics occurs when crack propagation starts El Polymers occurs when polymer backbones are aligned and about engineering stress to break engineering strain Plastic permanent deformation At lower temperature Tlt Tmelt3 El Simple tension test ElasticPastic engineering stress 6 at larger stress permanent plastic after load is removed gt 8p engineering strains plastic strain Elastic and plastic deformations III Stressstrain relations under uniaxial loading Ceramics Polymeric material Fracture Elm u Sires Stress Eng 39rl Shun in Strain Ductility III Ductility a measure of the degree of plastic deformation that has been sustained at fracture in 3 x100 l EL athA x 100 39 Ll Mechanic properties of typical metals Tqu 02 39I ypicall Mechanical Properties of Stuml Metals and Iluys in In nnvnlod Slalle I39t lll Vlrl39nglll I39mus Nlrt39nglll Illl Iili39 39huIL39L Jh l l Illql39 JI II ksi ll 39 iii 5 mm 1 3911 Aluminum 35 5 90 13 4 0 CT 6 In 200 2 45 Brass 70 u 302n 75 ll Sill 44 68 Iron 130 l9 262 38 45 Nickel 138 20 480 70 40 Steel 1020 180 26 380 55 25 Titanium 450 65 52 75 25 Molybdenum 565 82 555 95 3S Reelllence El Resilience is the capacity of a material to absorb energy when it is deformed elastically and then upon unloading to have this energy recovered c7y Res wnce UJ ade 1 0 II I a I lt2 Uslayey 6 I I I I I I 391 I 1 g 395 quotl l 25 I gt 160002 8y Strain Toughness El Energy to break a unit volume of material El Approximate by the area under the stressstrain curve Engineering small toughness ceramics tenSile large toughness metals stress 0 A Adapted from Fig 613 Caisle 7e i Engineering tensile strain a Brittle fracture elastic energy Ductile fracture elastic plastic energy Summary Stress and strain These are sizeindependent measures of load and displacement respectively Elastic behavior This reversible behavior often shows a linear relation between stress and strain To minimize deformation select a material with a large elastic modulus E or G Plastic behavior This permanent deformation behavior occurs when the tensile or compressive uniaxial stress reaches 6 Toughness The energy needed to break a unit volume of material Ductility The plastic strain at failure MSE 170A Midterm review Exam date 10272008 Mon lecture time Place Here Close book notes and no collaborations A sheet of lettersized paper with doublesided notes is allowed Material on the exam will be taken from the text book reading lecture notes homework and lab Bring a calculator and straight edgetriangle The review materials are not comprehensive there may be questions on the exam on topics not listed here Chapter 2 Bonding and atomic forces The periodic table What types of bonding are there How does bonding affect materials properties Chapter 2 The Periodic Table Columns SimilarValence Structure a CD CD m a 0 lt1 5 3 l x C Q r 4 l DMetal V D C C D Q IA gt y 1 O 0 T Nonmetal 392 O CU H quotA NA NA VA VlA VllA He 3 7 Intermediate 5 6 7 8 1 Li Be I B C N 0 F Na 11 12 My 13 14 15 16 17 18 Na Mg ilig lVB VB VIB VIIB l IB quot8 Al 5i PH 87 Cl VAr idaggdfrom 19 20 21 22 23 24 25 25 27 28 29 30 31 32 33 34 35 V g39 39 K Ca 11 V Cr Mn Fe Co Ni Cu Zn Ga Ge As 53 Br Kr Camste e 37 3s 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 T Rb Sr 2139 Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Ta 1 55 56 Rare 72 73 74 7s 76 77 78 79 so 81 82 83 84 as 86 Cs Ba 312 Hf Ta w Re Os Ir Pt Au Hg Tl Pb Bi Po At R111 7 88 ma 104 105 106 107 103 109 110 Fr Ra 52 Rf Db Sg Bh Hs Mt Ds Electropositive elements Readily donate electrons to become ions gt Electronegative elements Readily acquire electrons to become ions Chapter 2 3 Bonding and atomic forces continued Atomic forces amp potential vs interatomic distance Chapter 2 Atomic bonding in solids Bonding forces and energies Force F Polanllal energy E mmmm Attractlan Repulsmn Repulslon E Attractive force FA 1 InIeranmlc separation r I Repulslwa for2 FR A U r 1 N et Iorce FN I I I I39aJ 39l I Repulswe en ergy E I I Interatomlc separation k Nat energy EN 4 Attractla39e energy EA I r61 Chapter 2 39J 39 Crystal structure Determine atomsunit cell CN APF and density Draw and index crystallographic direction and planes Closepacked plane and stacking sequence Crystal systems Chapter 2 Crystal Structures Chapter2 7 Crystal structures ceramics Know the types of ceramic structures and identify their unit cells Determine coordination number for ceramic structures based on ionic radii and charge cs 0 Chapter 2 Defects Distinguish point linear dislocation 1D interfacial2D volume3D defects Draw and describe edge and screw dislocations Burgers circuits and vectors Understand equilibrium of vacancies and effect of T Chapter 2 Point Defects Vacancies vacant atomic sites in a structure Self Interstitials quotextraquot atoms positioned between atomic sites self interstitial Chapter 2 1O Point Defects in Alloys Two outcomes if impurity B added to host A Solid solution of B in A ie random dist of point defects Substitutional solid soln eg Cu in Ni Interstitial solid soln eg C in Fe Chapter 2 11 Imperfections in Solids Edge Dislocation extra halfplane of atoms inserted in a crystal structure b J to dislocation line Burgers vector Edge dislocation line Fig 43 Calister 7e Chapter2 12 Diffusion Mechanisms concentration gradients diffusion coefficient Ficks laws Effects of T on diffusion coefficients Chapter 2 Diffusion Interdiffusion In an alloy atoms tend to migrate from regions of high cone to regions of low conc Adapted from Figs 51 and 52 Callister 7e 7 Concentration Pro les 7 Concentration Pro les 7 Chapter2 14 SteadyState Diffusion Rate of diffusion independent of time d Flux proportional to concentration gradient a Fick s first law of diffusion H dx D a diffusion coefficient dx Ax 3 Chapter 2 15 Nonsteady State Diffusion The concentration of diffusing species is a function of both time and position C CXt In this case Fick s Second Law is used 2 Fick s Second Law E D a C at 6X2 Chapter2 16 Mechanical properties Definition of stress strain elastic modulus Analysis of stressstrain curves Yield strength tensile strength Poisson39s ratio ductility resilience and toughness Hardness Chapter 2 Concepts of stress and strain Tension tests engineering stress engineering strain Reduced section H 77239 2 Gauge length Compression tests li10 A 0 lo Chapter 2 Plastic deformation Slip plane direction and system resolved shear stress Mechanism of plastic deformation Strengthening mechanisms Recovery recrystallization and grain growth Chapter 2