材料科學與工程基礎”考試試題-英文原版教材班(注：第1、2、3題為必做題；第4、5、6、7題為選擇題，必須二選一。共100分)Glossary(2pointsforeach)crystalstructure:Thearrangementoftheatomsinamaterialintoarepeatablelattice.basis(ormotif):Agroupofatomsassociatedwithalattice.packingfractor:Thefractionofspaceinaunitcelloccupiedbyatoms.slipsystem:Thecombinationoftheslipplaneandtheslipdirection.criticalsize:Theminimumsizethatmustbeformedbyatomsclusteringtogetherintheliquidbeforethesolidparticleisstableandbeginstogrow.homogeneousnucleation:Formationofacriticallysizedsolidfromtheliquidbytheclusteringtogetherofalargenumberofatomsatahighundercooling(withoutanexternalinterface).coherentprecipitate:Aprecipitatewhosecrystalstructureandatomicarrangementhaveacontinuousrelationshipwithmatrixfromwhichprecipitateisformed.precipitationhardening:Astrengtheningmechanismthatreliesonasequenceofsolidstatephasetransformationsinadispersionofultrafineprecipitatesofa2ndphase.Thisissameasagehardening.Itisaformofdispersionstrengthening.diffusioncoefficient:Atemperature-dependentcoefficientrelatedtotherateatwhichatom,ion,orotherspeciesdiffusion.TheDCdependsontemperature,thecompositionandmicrostructureofthehostmaterialandalsoconcentrationofthediffusionspecies.uphilldiffusion:Adiffusionprocessinwhichspeciesmovefromregionsoflowerconcentrationtothatofhigherconcentration.DeterminetheindicesfortheplanesinthecubicunitcellshowninFigure1.(5points)Fig.1A(-364),B(-340),C(346).Fig.1A(-364),B(-340),C(346).?DetermineLnecrystdistructureforLnefoiiowing?(d)ametdiwiLnZ7A0/1x0A—1 /AQTiricmaofcTnmarloftica iomatola—4.9489a,r—i./dadiidonedtomperidtticepoini；(b)dmetdiWitha=0.42906nm,r=0.1858nmandoneatomperlatticepoint.(10po0nts)Solution:(a)fcc;(b)bcc.1.Whatisthecharacteristicofbrinellhardnesstest,rockwelhardnesstestandVickershardnesstest?Whataretheeffectsostrainrateandtemperatureonthemechanicalpropertiesofmetallicmaterials?(15points)2.Whataretheeffectsofcold-workonmetallicmaterials?Howtoeliminatethoseeffects?Andwhatismicro-mechanismfortheeliminatingcold-workeffects?(15points)1.BasedonthePb-Sn-BiternarydiagramasshowninFig.2,trytoShowtheverticalsectionof40wt.%Sn;(5points)Describethesolidificationprocessofthealloy2#withverylowcoolingspeed(includingphaseandmicrostructurechanges);(5points)Plottheisothermalsectionat150oC.(5points)2.A1mmsheetofFCCironisusedtocontainNinaheatedexchangerat1200oC.TheconcentrationofNatonesUrfaceis0.04atomicpercentandtheconcentrationatthesecondsurfaceis0.005atomicpercent.At1000oC,ifsameNconcentrationisdemandedat

thesecondsurfaceandthefluxofNbecomestohalfofthatat1200oC,thenwhatisthethicknessofsheet?(15points)1.Supposedthatacertainliquidmetalisundercooleduntilhomogeneousnucleationoccurs.(15points)Temperatureis1453°C,theLatent3Temperatureis1453°C,theLatent3,and： ”一(15points)hesolidificForthe^MetalNi,theFreezingTemperatureis1453°C,theLatentHeatofFusionis2756J/cm3,andtheSolid-liquidInterfacialEnergyis255x10-7J/cm2.Pleasecalculatethecriticalradiusat1353°C.(AssumethattheliquidNiisnotsolidified.)(15points)hesolidific2.Fig.3isaportionoftheMg-Alphasediagram.(15points)rocessofMg-10wt%Alalloy.

leasedescribetheequilitIfthesolidificationistoorapid,pleasedescribethesolidificationprocessofMg-10wt%Alalloy.rocessofMg-10wt%Alalloy.

leasedescribetheequilitPleasedescribetheequilibriumsolidificationprocessofMg-20wt%Alalloy,andcalculatetheamountofeachphaseat300°C.70060050040030020010010203040(p)￡370060050040030020010010203040(p)￡3巴。dE￡0MgWeightpercentaluminumFig.31.Figure4showsustheAl-CubinarydiagramandsomemicrostructuresfoundinacoolingprocessforanAl-4%Cualloy.Pleaseanswerfollowingquestionsaccordingtothisfigure.(20points)

Fig.4precipitate,matrixandmicroconstituent?Pleasepoint efigureandexplain.isneed-likeprecipitatenotgoodfordispersion? " ;nowninthefigureisWhatareFig.4precipitate,matrixandmicroconstituent?Pleasepoint efigureandexplain.isneed-likeprecipitatenotgoodfordispersion? " ;nowninthefigureisthemoutintheinthefigureandexplain.Whyisneed-likeprecipitatenotstrengthening?Thetypicalmicrostructuresgoodornot?why?Pleasetellushowtoobtaintheidealmicrostructureshowninthisfigure.Candispersionstrengthenedmaterialsbeusedathightemperature?Pleasegivethereasons(comparingwithcoldworkingstrengthening)2.Pleaseanswerfollowingquestionsaccordingtothetime-temperature-transformation(TTT)diagramasshowninFig.5.(20points)WhatsteelisthisTTTdiagramfor?AndwhatmeansP,B,andMinthefigure?WhydosetheTTTdiagramexhibitsa‘C’shape?PointoutwhatmicroconstituentwillbeobtainedafterausteniteiscooledaccordingtothecurvesI,II,IIIandIVWhatismicrostructuraldifferencebetweenthecurveIandthecurveII?HowtoobtainthesteelwiththestructureofPointoutwhatmicroconstituentwillbeob