清华大学lesson 8：复习资料

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1、材料科学基础材料科学基础FundamentalofMaterialsFundamentalofMaterialsFundamentalofMaterialsFundamentalofMaterialsProf:TianMinBoTel:62795426，62772851E-mail:tmb@mail.tsinghua.edu.cnDepartmentofMaterialScienceandEngineeringTsinghuaUniversity.Beijing100084LessoneightChapterChapterⅢⅢTheStructuresof

2、AlloysTheStructuresofAlloys§§3.1Basicconceptsofalloys3.1Basicconceptsofalloys�ⅠⅠ.Definition.DefinitionAnalloyisthecombinationofmetal(s)withotherelementsthroughchemicalbonding.�ⅡⅡ.Terminology.Terminology1.Component(orconstituent)�onecomponentsystem�twocomponentsystembinarysystem�th

3、reecomponentsystemternarysystem�fourcomponentsystemquarternarysystem�fivecomponentsystemquinarysystemmulti-componentsystem2.CompositionItcanbeexpressedeitherbyatomicpercentage(molfraction)XaorbymasspercentageXmWmiMiXaiMiXai=nXmi=n∑(XmMj)∑(XajMj)jj=1j=13.PhaseAphaseisahomogeneouspa

4、rtofthematerialinwhichnoabruptchangeincomposition,structureandpropertiesoccurs.Analloymaybesinglephaseormulti-phasematerial.4.StructureStructureisageneraltermforthecombinationofatomarrangementincludingthetypesamountsanddistributionofalltypesofmaterialaswellasgrainsize,defectetc.�Ⅲ

5、Ⅲ.ClassificationofAlloyPhases.ClassificationofAlloyPhases1.AccordingtostructureSolidSolutionCompoundInSolidSolution,atomsofdifferentcomponentshareacommonlatticeinvariableproportion.2.AccordingtopositionofthealloyinphasediagramTerminalS.S.αβIntermediateS.S.α+βorsecondaryS.S.AB§§3.2

6、FactorsAffectingthe3.2FactorsAffectingtheStructureofAlloyPhaseStructureofAlloyPhase1.WhatissizefactormetallicradiirA+rB=dionicradiiAtomicr++r-=dcovalentradiisinglebondradiusradiiVanderWaalsradiiCNradii∆r12→8=−3%r∆r12→6=−4%r∆r12→4=−12%rBCCFCC32CNofBCC:8()+6(a)CNofFCC:12()aa223322rα

7、==aα×0.290nmrβ==aβ×0.364nm4444=0.12557nm=0.128674nmGoldschmidtatomicradiiistheradiiofatominstructureswithCN=12d−dABSizefactorisdefinedasδδ=×100%dA2.WhatisElectrochemicalfactor——ElectronegativityXXrepresentstheabilityofanatomofanelementinthecompondtoattractelectronstoitself.n+1Paul

8、i’sempiricalrule:X=0.31+0.5r(1)n: