清华材料科学基础课件（英文）.ppt

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1、材料科学基础FundamentalofMaterialsLessoneight2021/7/28材料科学基础ChapterⅢTheStructuresofAlloys2021/7/28材料科学基础§3.1BasicconceptsofalloysⅠ.DefinitionAnalloyisthecombinationofmetal(s)withotherelementsthroughchemicalbonding.Ⅱ.Terminology2021/7/28材料科学基础2021/7/28材料科学基础1.C

2、omponent(orconstituent)onecomponentsystemtwocomponentsystembinarysystemthreecomponentsystemternarysystemfourcomponentsystemquarternarysystemfivecomponentsystemquinarysystemmulti-componentsystem2021/7/28材料科学基础2.CompositionItcanbeexpressedeitherbyatomicper

3、centage(molfraction)XaorbymasspercentageXm2021/7/28材料科学基础3.PhaseAphaseisahomogeneouspartofthematerialinwhichnoabruptchangeincomposition,structureandpropertiesoccurs.Analloymaybesinglephaseormulti-phasematerial.4.StructureStructureisageneraltermforthecomb

4、inationofatomarrangementincludingthetypesamountsanddistributionofalltypesofmaterialaswellasgrainsize,defectetc.2021/7/28材料科学基础Ⅲ.ClassificationofAlloyPhases1.AccordingtostructureSolidSolutionCompoundInSolidSolution,atomsofdifferentcomponentshareacommonlat

5、ticeinvariableproportion.2021/7/28材料科学基础2021/7/28材料科学基础2.AccordingtopositionofthealloyinphasediagramTerminalS.S.IntermediateS.S.orsecondaryS.S.αBAβα+β2021/7/28材料科学基础§3.2FactorsAffectingtheStructureofAlloyPhase1.WhatissizefactormetallicradiirA+rB=dionicra

6、diir++r-=dcovalentradiisinglebondradiusVanderWaalsradiiAtomicradii2021/7/28材料科学基础CNradiiBCCFCCCNofBCC:8()+6(a)CNofFCC:12()rα==rβ===0.12557nm=0.128674nm2021/7/28材料科学基础GoldschmidtatomicradiiistheradiiofatominstructureswithCN=12Sizefactorisdefinedas2021/7/2

7、8材料科学基础2.WhatisElectrochemicalfactor——ElectronegativityXXrepresentstheabilityofanatomofanelementinthecompondtoattractelectronstoitself.Pauli’sempiricalrule:n:valencer(1):simplebondradius2021/7/28材料科学基础EAA——bondingenergybetweenA-AatomsEBB——bondingenergybe

8、tweenB-BatomsEAB——bondingenergybetweenA-Batoms2021/7/28材料科学基础3.Electronconcentration(e/a)Electronconcentration(e/a)isthenumberofvalenceelectronsperatomontheaverage.i.g.forCuZn:e/a=3/2=1.52021/7/28材料科学基础§3.3SolidSolutionⅠ.C