英文原版教材班“材料科學(xué)基礎(chǔ)”考試試題

英文原版教材班“材料科學(xué)根底〞考試試題試卷一Examinationproblemsofthecourseof“fundamentofmaterialsscience〞姓名：班級(jí)：記分：1.Glossary(2pointsforeach)1)crystalstructure:2)basis(ormotif):3)packingfractor:4)slipsystem:5)criticalsize:6)homogeneousnucleation:7)coherentprecipitate:8)precipitationhardening:9)diffusioncoefficient:10)uphilldiffusion:2.DeterminetheindicesfortheplanesinthecubicunitcellshowninFigure1.(5points)Fig.13.Determinethecrystalstructureforthefollowing:(a)ametalwitha0=4.9489?,r=1.75?andoneatomperlatticepoint;(b)ametalwitha0=0.42906nm,r=0.1858nmandoneatomperlatticepoint.(10points)4-1.Whatisthecharacteristicofbrinellhardnesstest,rockwellhardnesstestandVickershardnesstest?Whataretheeffectsofstrainrateandtemperatureonthemechanicalpropertiesofmetallicmaterials?(15points)4-2.Whataretheeffectsofcold-workonmetallicmaterials?Howtoeliminatethoseeffects?Andwhatismicro-mechanismfortheeliminatingcold-workeffects?(15points)5-1.BasedonthePb-Sn-BiternarydiagramasshowninFig.2,tryto(1)Showtheverticalsectionof40wt.%Sn;(4points)(2)Describethesolidificationprocessofthealloy2#withverylowcoolingspeed(includingphaseandmicrostructurechanges);(4points)(3)Plottheisothermalsectionat150oC.(7points)Fig.2Fig.25-2.A1mmsheetofFCCironisusedtocontainN2inaheatedexchangerat1200oC.TheconcentrationofNatonesurfaceis0.04atomicpercentandtheconcentrationatthesecondsurfaceis0.005atomicpercent.At1000oC,ifsameNconcentrationisdemandedatthesecondsurfaceandthefluxofNbecomestohalfofthatat1200o6-1.Supposedthatacertainliquidmetalisundercooleduntilhomogeneousnucleationoccurs.(15points)Howtocalculatethecriticalradiusofthenucleusrequired?Pleasegivethedeductionprocess.FortheMetalNi,theFreezingTemperatureis1453C,theLatentHeatofFusionis2756J/cm3,andtheSolid-liquidInterfacialEnergyis25510-7J/cm2.Pleasecalculatethecriticalradiusat13536-2.Fig.3isaportionoftheMg-Alphasediagram.(15points)Ifthesolidificationistoorapid,pleasedescribethesolidificationprocessofMg-10wt%Alalloy.PleasedescribetheequilibriumsolidificationprocessofMg-20wt%Alalloy,andcalculatetheamountofeachphaseat300Fig.37-1.Figure4showsustheAl-CubinarydiagramandsomemicrostructuresfoundinacoolingprocessforanAl-4%Cualloy.Pleaseanswerfollowingquestionsaccordingtothisfigure.(20points)Fig.4(1)Whatareprecipitate,matrixandmicroconstituent?Pleasepointthemoutintheinthefigureandexplain.(2)Whyisneed-likeprecipitatenotgoodfordispersionstrengthening?Thetypicalmicrostructureshowninthefigureisgoodornot?why?(3)Pleasetellushowtoobtaintheidealmicrostructureshowninthisfigure.(4)Candispersionstrengthenedmaterialsbeusedathightemperature?Pleasegivethereasons(comparingwithcoldworkingstrengthening)7-2.Pleaseanswerfollowingquestionsaccordingtothetime-temperature-transformation(TTT)diagramasshowninFig.5.(20points)(1)WhatsteelisthisTTTdiagramfor?AndwhatmeansP,B,andMinthefigure?(2)WhydosetheTTTdiagramexhibitsa‘C’shape?(3)PointoutwhatmicroconstituentwillbeobtainedafterausteniteiscooledaccordingtothecurvesI,II,IIIandIV.(4)WhatismicrostructuraldifferencebetweenthecurveIandthecurveII?(5)HowtoobtainthesteelwiththestructureofP+BP+M+A(residual)P+B+M+A(residual)FulltemperedmartensiteIfyoucan,pleasedrawtherelativecoolingcurveortheflowchartofheattreatment.IIIIIIIVFig.5IIIIIIIV英文原版教材班“材料科學(xué)根底〞考試試題答案Solutionsofthecourseof“fundamentofmaterialsscience〞1.Glossary(2pointsforeach)1)Thearrangementoftheatomsinamaterialintoarepeatablelattice.2)Agroupofatomsassociatedwithalattice.3)Thefractionofspaceinaunitcelloccupiedbyatoms.4)Thecombinationoftheslipplaneandtheslipdirection.5)Theminimumsizethatmustbeformedbyatomsclusteringtogetherintheliquidbeforethesolidparticleisstableandbeginstogrow.6)Formationofacriticallysizedsolidfromtheliquidbytheclusteringtogetherofalargenumberofatomsatahighundercooling(withoutanexternalinterface).7)Aprecipitatewhosecrystalstructureandatomicarrangementhaveacontinuousrelationshipwithmatrixfromwhichprecipitateisformed.8)Astrengtheningmechanismthatreliesonasequenceofsolidstatephasetransformationsinadispersionofultrafineprecipitatesofa2ndphase.Thisissameasagehardening.Itisaformofdispersionstrengthening.9)Atemperature-dependentcoefficientrelatedtotherateatwhichatom,ion,orotherspeciesdiffusion.TheDCdependsontemperature,thecompositionandmicrostructureofthehostmaterialandalsoconcentrationofthediffusionspecies.10)Adiffusionprocessinwhichspeciesmovefromregionsoflowerconcentrationtothatofhigherconcentration.2.Solution:A(-364),B(-340),C(346).3.Solution:(a)fcc;(b)bcc.4-1.Whatisthecharacteristicofbrinellhardnesstest,rockwellhardnesstestandVickershardnesstest?Whataretheeffectsofstrainrateandtemperatureonthemechanicalpropertiesofmetallicmaterials?(15points)4-2.Whataretheeffectsofcold-workonmetallicmaterials?Howtoeliminatethoseeffects?Andwhatismicro-mechanismfortheeliminatingcold-workeffects?(15points)5-1.BasedonthePb-Sn-BiternarydiagramasshowninFig.2,tryto(1)Showtheverticalsectionof40wt.%Sn;(5points)(2)Describethesolidificationprocessofthealloy2#withverylowcoolingspeed(includingphaseandmicrostructurechanges);(5points)(3)Plottheisothermalsectionat150oC.(5points)Fig.2Fig.25-2.A1mmsheetofFCCironisusedtocontainN2inaheatedexchangerat1200oC.TheconcentrationofNatonesurfaceis0.04atomicpercentandtheconcentrationatthesecondsurfaceis0.005atomicpercent.At1000oC,ifsameNconcentrationisdemandedatthesecondsurfaceandthefluxofNbecomestohalfofthatat1200o6-1.Supposedthatacertainliquidmetalisundercooleduntilhomogeneousnucleationoccurs.(15points)Howtocalculatethecriticalradiusofthenucleusrequired?Pleasegivethedeductionprocess.FortheMetalNi,theFreezingTemperatureis1453C,theLatentHeatofFusionis2756J/cm3,andtheSolid-liquidInterfacialEnergyis25510-7J/cm2.Pleasecalculatethecriticalradiusat13536-2.Fig.3isaportionoftheMg-Alphasediagram.(15points)Ifthesolidificationistoorapid,pleasedescribethesolidificationprocessofMg-10wt%Alalloy.PleasedescribetheequilibriumsolidificationprocessofMg-20wt%Alalloy,andcalculatetheamountofeachphaseat300Fig.37-1.Figure4showsustheAl-CubinarydiagramandsomemicrostructuresfoundinacoolingprocessforanAl-4%Cualloy.Pleaseanswerfollowingquestionsaccordingtothisfigure.(20points)Fig.4(1)Whatareprecipitate,matrixandmicroconstituent?Pleasepointthemoutintheinthefigureandexplain.(2)Whyisneed-likeprecipitatenotgoodfordispersionstrengthening?Thetypicalmicrostructureshowninthefigureisgoodornot?why?(3)Pleasetellushowtoobtaintheidealmicrostructureshowninthisfigure.(4)Candispersionstrengthenedmaterialsbeusedathightemperature?Pleasegivethereasons(comparingwithcoldworkingstrengthening)7-2.Pleaseanswerfollowingquestionsaccordingtothetime-temperature-transformation(TTT)diagramasshowninFig.5.(20points)(1)WhatsteelisthisTTTdiagramfor?AndwhatmeansP,B,andMinthefigure?(2)WhydosetheTTTdiagramexhibitsa‘C’shape?(3)PointoutwhatmicroconstituentwillbeobtainedafterausteniteiscooledaccordingtothecurvesI,II,IIIandIV.(4)WhatismicrostructuraldifferencebetweenthecurveIandthecurveII?(5)HowtoobtainthesteelwiththestructureofP+BP+M+A(residual)P+B+M+A(residual)FulltemperedmartensiteIfyoucan,pleasedrawtherelativecoolingcurveortheflowchartofheattreatment.IIIIIIIVFig.5IIIIIIIV英文原版教材班“材料科學(xué)根底〞考試試題試卷二Examinationproblemsofthecourseof“fundamentofmaterialsscience〞姓名：班級(jí)：記分：1.Youwouldliketobeabletophysicallyseparatedifferentmaterialsinascraprecyclingplant.Describesomepossiblemethodsthatmightbeusedtoseparatematerialssuchaspolymers,aluminumalloys,andsteelsfromoneanother.(5points)2.versusatomicnumber(i.e.,plotmeltingtemperaturesofLithroughCs).Discussthisrelationship,basedonatomicbondingandbindingenergy.(10points)3.Above882℃,titaniumhasaBCCcrystalstructure,witha=0.332nm.Belowthistemperature,titaniumhasaHCPstructure,witha=0.2978nmandc=0.4735nm.Isthisacontractionorexpansion?4.ThedensityofBCCironis7.882g/cm3andthelatticeparameteris0.2866nmwhenhydrogenatomsareintroducedatinterstitialpositions.Calculate(a)theatomicfractionofhydrogenatomsand(b)thenumberofunitcellsrequiredonaveragetocontainonehydrogenatom.(15points)5.Acarburizingprocessiscarriedoutona0.10%Csteelbyintroducing1.0%Catthesurfaceat980℃,wheretheironisFCC.Calculatethecarboncontentat0.01cm,0.05cm,and0.10cmbeneaththesurfaceafter1h.6.Thefollowingdatawerecollectedfromastandard0.505-in.-diametertestspecimenofacopperalloy(initiallength(to)=2.0in.):LoadGageLengthStressStrain(lb)(in.)(psi)(in/in.)02.0000000.02.0016715,0002.0033330,0002.0041737,5002.009045,0000.004510,5002.04052,5000.0212,0002.2660,0000.1312,40062,0000.2511,40057,0000.51atfracture,and(h)themodulusofresilience.(15points)7.A1.5-em-diametermetalbarwitha3-cmgagelengthissubjectedtoatensiletest.Thefollowingmeasurementsaremade.ChangeinForce(N)Gagelength(cm)Diameter(cm)16,2400.66421.202819,0661.47541.088419,2732.46630.9848Determinethestrainhardeningcoefficientforthemetal.IsthemetalmostlikelytobeFCC,BCC,orHCP?Explain.(15points)8.expectedtodisplayunlimitedsolidsolubility?Explain.(15points)(a)Au-Ag(b)Al-Cu(c)Al-Au(d)U-W(e)Mo-Ta(f)Nb-W(g)Mg-Zn(h)Mg-Cd英文原版教材班“材料科學(xué)根底〞考試試題答案Solutionsofthecourseof“fundamentofmaterialsscience〞1.Steelscanbemagneticallyseparatedfromtheothermaterials;steel(orcarbon-containingironalloys)areferromagneticandwillbeattractedbymagnets.Densitydifferencescouldbeused—polymershaveadensitynearthatofwater;thespecificgravityofaluminumalloysisaround2.7;thatofsteelsisbetween7.5and8.Electricalconductivitymeasurementscouldbeused—polymersareinsulators,aluminumhasaparticularlyhighelectricalconductivity.(5points)2.K–63.2Astheatomicnumberincreases,themeltingtemperaturedecreases,(10points)3.directlycompared.VVHCP△V=×=-0.6%(10points)4. Thetotalatomspercellinclude2Featomsand0.0081Hatoms.Thus:(10points) atomsis:(5points)5.Cx=0.87%CCx=0.43%CCx=0.18%C(15points)6.=FI(/4)(0.505)2=F/0.2=(l-2)/2E=(30,000-0)/(0.001665-0)=18x106psi(15points)7.Force(lb)Gagelength(in.)Diameter(in.)Truestress(psi)Truestrain(psi)16,2403.664212.0281430.20019,0664.475410.8842050.40019,2735.46639.8482490.600σt=Kεt2orln143=lnK+nln0.2ln249=lnK+nln0.6n=0.51Astrainhardeningcoefficientof0.51istypicalofFCCmetals.(15points)8.samecrystalstructures,andthesamevalences.Eachofthesemightbetionscomplicatethediagram.](15points)英文原版教材班“材料科學(xué)根底〞考試試題試卷三Examinationproblemsofthecourseof“fundamentofmaterialsscience〞姓名：班級(jí)：記分：1.Youwouldliketobeabletoidentifydifferentmaterialswithoutresortingtochemicalanalysisorlengthytestingprocedures.Describesomepossibletestingandsortingtechniquesyoumightbeabletousebasedonthephysicalpropertiesofmaterials.(5points)2.tableversusatomicnumber(i.e.,plotmeltingtemperaturesofTithroughNi,Zrandbindingenergy,(a)astheatomicnumberincreasesineachrowoftheperiodictableand(b)astheatomicnumberincreasesineachcolumnoftheperiodictable.(10points)3.andtheatomicweightis9.01g/mol.Determine(a)thenumberofatomsineachunitcelland(b)thepackingfactorintheunitcell.(10points)4.Supposeweintroduceonecarbonatomforevery100ironatomsinaninterstitialpositioninBCCiron,givingalatticeparameterof0.2867nm.FortheFe-Calloy,find(a)thedensityand(b)thepackingfactor.(15points)5.Ironcontaining0.05%Cisheatedto912oCinanatmospherethatproduces1.20%Catthesurfaceandisheldfor24h.Calculatethecarboncontentat0.05cmbeneaththesurfaceif(a)theironisBCCand(b)theironisFCC.Explainthedifference.(15points)6.Thefollowingdatawerecollectedfroma0.4-in.diametertestspecimenofpolyvinylchloride(l0=2.0in):Load(lb)GageLength(in.)Stress(psi)Strain(in/in.)02.0000000.03002.007462,3876002.014964,7730.007489002.023747,16012002.0329,5470.01615002.04611,9330.023166013,2060.03516002.09412,7290.04714202.12(fracture)11,2970.06atfracture,and(h)themodulusofresilience.(15points)7.AtitaniumalloycontainsaveryfinedispersionoftinyEr203particles.Whatwillbetheeffectoftheseparticlesonthegraingrowthtemperatureandthesizeofthegrainsatanyparticularannealingtemperature?Explain.(15points)8.Suppose1at%ofthefollowingelementsisaddedtocopper(formingaseparatealloywitheachelement)withoutexceedingthesolubilitylimit.Whichonewouldbeexpectedtogivethehigherstrengthalloy?Isanyofthealloyingelementsexpectedtohaveunlimitedsolidsolubilityincopper?(a)Au(b)Mn(c)Sr(d)Si(e)Co(15points)英文原版教材班“材料科學(xué)根底〞考試試題答案Solutionsofthecourseof“fundamentofmaterialsscience〞1.Steelscanbemagneticallyseparatedfromtheothermaterials;steel(orcarbon-containingironalloys)areferromagneticandwillbeattractedbymagnets.Densitydifferencescouldbeused—polymershaveadensitynearthatofwater;thespecificgravityofaluminumalloysisaround2.7;thatofsteelsisbetween7.5and8.Electricalconductivitymeasurementscouldbeused—polymersareinsulators,aluminumhasaparticularlyhighelectricalconductivity.(5points)2. partlyfull.InCr,thereare5electronsinthe3dshell;inMo,thereare5electronsinthe4dshell;inWthereare4electronsinthe5dshell.Ineachcolumn,themeltingtemperatureincreasesastheatomicnumberincreases—theatomcorescontainalargernumberoftightlyheldelectrons,makingthemetalsmorestable.(10points)3.(10points)4.1/50Cperunitcell:(15points)5.BCC9871Cx=1.11%CCx=0.95%Cboncontentatpoint“x〞.(15points)6.=F(l-2)/2 E=(7160-0)/(0.01187-0)=603,000psi(15points)7.Theseparticles,byhelpingpindiegrainboundaries,willincreasethegraingrowthtemperatureanddecreasethegrainsize.(15points)8.temperatures.(15points)英文原版教材班“材料科學(xué)根底〞考試試題試卷四Examinationproblemsofthecourseof“fundamentofmaterialsscience〞姓名：班級(jí)：記分：1.Aluminumhasadensityof2.7g/cm3.Supposeyouwouldliketoproduceacompositematerialbasedonaluminumhavingadensityof1.5g/cm3.Designamaterialthatwouldhavethisdensity.Wouldintroducingbeadsofpolyethylene,withadensityof0.95g/cm3,intothealuminumbealikelypossibility?Explain.(5points)2.(a)Aluminumfoilusedforstoringfoodweighsabout0.3gpersquareinch.Howmanyatomsofaluminumarecontainedinthissampleoffoil?(b)UsingthedensitiesandatomicweightsgiveninAppendixA,calculateandcomparethenumberofatomspercubiccentimeterin(i)leadand(ii)lithium.(10points)3.Thedensityofpotassium,whichhastheBCCstructureandoneatomperlattice(a)thelatticeparameter;and(b)theatomicradiusofpotassium.(10points)4.ThedensityofasampleofHCPberylliumis1.844g/cm3andthelatticeparametersarea0=0.22858nmandc0=0.35842nm.Calculate(a)thefractionofthelatticepointsthatcontainvacanciesand(b)thetotalnumberofvacanciesinacubiccentimeter.(15points)5.AceramicpartmadeofMgOissinteredsuccessfullyat1700℃in90minutes.Tominimizethermalstressesduringtheprocess,weplantoreducethetemperatureto1500℃.Whichwilllimittherateatwhichsinteringcanbedone:diffusionofmagnesiumionsordiffusionofoxygenions?Whattimewillberequiredatthelower6.plasticdeformationoccurs.(b)Theflexuralmodulusofaluminais45x106psianditsflexuralstrengthis46,000psi.Abarofalumina0.3in.thick,1.0in.wide,and10in.longisplacedonsupports7in.apart.Determinetheamountofdeflectionatthemomentthebarbreaks,assumingthatnoplasticdeformationoccurs.(15points)7.inelementA,andelementAhasamaximumsolubilityof15%inelementB.Thenumberofdegreesoffreedomfromthephaseruleiszerowhenthetemperatureis725°Candthereis35%Bpresent.Atroomtemperature1%BissolubleinAand7%AissolubleinB.(15points)8.SupposethatagehardeningispossibleintheAl-Mgsystem(seeFigure10-11).(a)Recommendanartificialage-hardeningheattreatmentforeachofthefollowingalloys,and(b)comparetheamountoftheprecipitatethatformsfromyourtreatmentofeachalloy.(i)Al-4%Mg(ii)Al-6%Mg(iii)Al-12%Mg(c)Testingofthealloysaftertheheattreatmentrevealsthatlittlestrengtheningoccursasaresultoftheheattreatment.Whichoftherequirementsforagehardeningislikelynotsatisfied?(15points)英文原版教材班“材料科學(xué)根底〞考試試題答案Solutionsofthecourseof“fundamentofmaterialsscience〞1.Inordertoproduceanaluminum-matrixcompositematerialwithadensityof1.5g/cm3,wewouldneedtoselectamaterialhavingadensityconsiderablylessthan1.5g/cm3.Whilepolyethylene’sdensitywouldmakeitapossibility,thepolyethylenehasaverylowmeltingpointcomparedtoaluminum;thiswouldmakeitverydifficulttointroducethepolyethyleneintoasolidaluminummatrix—processessuchascastingorpowdermetallurgywoulddestroythepolyethylene.ThereforepolyethylenewouldNOTbealikelypossibility.Oneapproach,however,mightbetointroducehollowglassbeads.Althoughceramicglasseshavedensitiescomparabletothatofaluminum,ahollowbeadwillhaveaverylowdensity.Theglassalsohasahighmeltingtemperatureandcouldbeintroducedintoliquidaluminumforprocessingasacasting.(5points)2.(a)(ii)Inlithium:(10points)3.r=(10points)4. (15points)5.radiusoftheoxygen.t1500=D1700t1700/D1500=(15points)6.theflexuralmodulus.merisnotexpectedtofracture.F=(2)(1in)(0.3in)2(46,000psi/(3)(7in.)=394lb8=(394lb)(7in)3/(4)(lin)(0.3in)3(45x106psi)=0.0278in.(15points)7.(15points)8.Al-4%MgAl-6%MgAl-12%MgTEutectic451451451TSolvs210280390210-451280-451390-451QuenchQuenchQuenchAgeat:<210<280<390areagedat200°C,asanexample,thetielinegoesfromabout3.8toA1-4%Mg:%=(4?3.82)/(35?3.82)X100=0.6%Al-6%Mg:%=(6?3.82)/(35?3.82)X100=7.1%Al-12%Mg:%=(12?3.82)/(35?3.82)X100=26.8%Mostlikely,acoherentprecipitateisnotformed;simpledispersion

strengthening,ratherthanagehardening,occurs.(15points)英文原版教材班“材料科學(xué)根底〞考試試題試卷五Examinationproblemsofthecourseof“fundamentofmaterialsscience〞姓名：班級(jí)：記分：1.Youwouldliketodesignanaircraftthatcanbeflownbyhumanpowernonstopforadistanceof30km.Whattypesofmaterialpropertieswouldyourecommend?Whatmaterialsmightbeappropriate?(5points)2.Boronhasamuchlowercoefficientofthermalexpansionthanaluminum,eventhoughbothareinthe3Bcolumnoftheperiodictable.Explain,basedonbindingenergy,atomicsize,andtheenergywell,whythisdifferenceisexpected.(10points)3.DeterminetheASTMgrainsizenumberif20grains/squareinchareobservedatamagnificationof400.(10points)4.Wecurrentlycansuccessfullyperformacarburizingheattreatmentat1200oCin1h.Inanefforttoreducethecostofthebricklininginourfurnace,weproposetoreducethecarburizingtemperatureto950℃.Whattimewillberequiredtogiveusasimilarcarburizingtreatment?5.ThedatabelowwereobtainedfromaseriesofCharpyimpacttestsperformedonfoursteels,eachhavingadifferentmanganesecontent.Plotthedataanddetermine(a)thetransitiontemperature(definedbythemeanoftheabsorbedenergiesintheductileandbrittleregions)and(b)thetransitiontemperature(definedasthetemperaturethatprovides50Jabsorbedenergy).Plotthetransitiontemperatureversusmanganesecontentanddiscusstheeffectofmanganeseonthetoughnessofsteel.Whatwouldbetheminimummanganeseallowedinthesteelifapartistobeusedat0°CTesttemperature°CImpactsnergy(J)-10025515-7525725-502122045-2510254070030557511025601001101355010512513014075130135135140100130135135140(15points)6.A3-in.-diametercastingwasproduced.Thetimesrequiredforthesolid-liquidinterfacetoreachdifferentdistancesbeneaththecastingsurfaceweremeasuredandareshowninthefollowingtable.(in.)Time(s)0.132.65.710.373.58.570.5130.611.430.75225.015.001.0334.918.22Determine(a)thetimeatwhichsolidificationbeginsatthesurfaceand(b)thetimeatwhichtheentirecastingisexpectedtobesolid,(c)Supposethecenterofthecastingactuallysolidifiedin720s.Explainwhythistimemightdifferfromthetimecalculatedinpart(b).(15points)7.ConsideraPb-15%Snalloy.Duringsolidification,determine(a)thecompositionofthefirstsolidtoform,(b)theliquidustemperature,solidustemperature,solvustemperature,andfreezingrangeofthealloy,(c)theamountsandcompositionsof(e)theamountsandcompositionsofeachphaseat25°C.(158.AnAl-2.5%Cualloyissolution-treated,quenched,andoveragedat230°Ctoproduceastablemicrostructure.Ifthespheroidalprecipitatessothatformhasaparticlespercm3.(1英文原版教材班“材料科學(xué)根底〞考試試題答案Solutionsofthecourseof“fundamentofmaterialsscience〞1.Bimetallicmaterialsareproducedbybondingtwomaterialshavingdifferentcoefficientsofthermalexpansiontooneanother,formingalaminarcomposite.Whenthetemperaturechanges,oneofthematerialswillexpandorcontractmorethantheothermaterial.Thisdifferenceinexpansionorcontractioncausesthebimetallicmaterialtochangeshape;iftheoriginalshapeisthatofacoil,thenthedevicewillcoiloruncoil,dependingonthedirectionofthetemperaturechange.Inorderforthematerialtoperformwell,thetwomaterialsmusthaveverydifferentcoefficientsofthermalexpansionandshouldhavehighenoughmodulusofelasticitysothatnopermanentdeformationofthematerialoccurs.(5points)2. 1 rB 1rsizeoftheboronatomandthelowerbindingenergyassociatedwithitssize.(10points)3.(10points)4.t1200=1ht950=D1200t1200/D950(15points)5.are:0.30%Mn:T=150.39%Mn:T=-5°C1.01%Mn:r=-15°forimprovingtheimpactpropertiesofthesteel.onthe50Jcriterion.6.d=k—c(b)1.5=0.070-0.3tcenter=(1.8/0.07)2=661S(15points)7.L:30%Sn:12%Sn;:15%Sn100%:2%Pba:100%Sn(15points)8.d=9000X10~10m=9X10?5cmre=4.5X10??(15points)英文原版教材班“材料科學(xué)根底〞考試試題試卷六Examinationproblemsofthecourseof“fundamentofmaterialsscience〞姓名：班級(jí)：記分：1.Wewouldliketoproduceatransparentcanopyforanaircraft.Ifweweretouseaceramic(thatis,traditionalwindowglass)canopy,rocksorbirdsmightcauseittoshatter.Designamaterialthatwouldminimizedamageoratleastkeepthecanopyfrombreakingintopieces.(5points)2.Methane(CH4)hasatetrahedralstructuresimilartothatofSiO2(Figure2-16),withacarbonatomofradius0.77×10-8cmatthecenterandhydrogenatomsofradius3.Adiffractedx-raybeamisobservedfromthe(311)planesofaluminumata2θparameterofthealuminum.(10points)4.DeterminetheASTMgrainsizenumberif25grains/squareinchareobservedatamagnificationof50.(15points)5.Determinethemaximumallowabletemperaturethatwillproduceafluxoflessthan2000Hatoms/cm2-sthroughaBCCironfoilwhentheconcentrationgradientis?5×1016atoms/cm3?cm.(Notethenegativesignfortheflux.)(15points)6.ThefollowingdatawereobtainedfromaseriesofCharpyimpacttestsperformedonfourductilecastirons,eachhavingadifferentsiliconcontent.Plotthedataanddetermine(a)thetransitiontemperature(definedbythemeanoftheabsorbedenergiesintheductileandbrittleregions)and(b)thetransitiontemperature(definedasthetemperaturethatprovides10Jabsorbedenergy).Plotthetransitiontemperatureversussiliconcontentanddiscusstheeffectofsilicononthetoughnessofthecastiron.Whatwouldbethemaximumsiliconallowedinthecastironifapartistobeusedat25°Ctemperature°C2.55%SiImpact2.85%Sienergy(J)3.25%Si3.63%Si-502.52.522-2532.52206532.52513107450171412875191616131001916161612519161616(15points)7.ConsideraPb-35%Snalloy.Determine(a)ifthealloyishypoeutecticorhypereu-tectic,(b)thecompositionofthefirstsolidtoformduringsolidification,(c)theamountsandcompositionsofeachphaseat184°C,(d)theamountsandcomposi(158.Ineutecticalloys,theeutecticmicroconstituentisgenerallythecontinuousone,butdescribingthechangesthatoccurwithdecreasingtemperatureineachreaction,explainwhythisdifferenceisexpected.(15points)英文原版教材班“材料科學(xué)根底〞考試試題答案Solutionsofthecourseof“fundamentofmaterialsscience〞1.Wemightsandwichathinsheetofatransparentpolymerbetweentwolayersoftheglass.Thisapproach,usedforwindshieldsofautomobiles,willpreventthe“safety〞glassfromco