材料物理导论-Chapter-5.ppt

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1、(b)AbnormalGrainGrowthThemannerofgrowth：Afewgrainssuddenlyarecoarsened,whichresultsinthedifferenceofgrainsizeisincreased.Thedrivingforce：Thetotalboundaryenergyislowered.Growthcondition：Mostgrainboundaryissteadyorpinning,butafewgrainboundaryeasilymigrate.Theinfluencefactorare:（1）S

2、mallanddispersedsecond-phaseparticlecanbepinnedinrecrystallizationmicrostructure.（2）Recrystallizedtextureisformed,grainorientationdifferenceissmallandgrainboundarymigrationrateissmall.5.RecrystallizationTextureandAnnealingTwinsRecrystallizationtexture:Afterrecrystallizaiton,newgr

3、ainsofthedeformedmetalstillhaveapreferentialcrystallographicorientation.Therearethreecases:(1)Identicaltotheinitialclod-deformedtexture.(2)Theinitialtexturedisappearsandnewtextureformed.(3)Theinitialtexturedisappearsandnotextureformed.(b)Growththeories:Orientednucleationtheory:Fo

4、rlarge-deformedmetalstructure,theorientationofsubgrainsissimilarsothatrecrystallizationhasapreferentialcrystallographicorientation.Therefore,thenewtexturewillbeidenticaltotheexistedtextures.Orientedgrowththeory:Someparticularorientationnuleiwillrapidlygrowindeformedmatrix.(c)Anne

5、alingtwins:Twinsareformedduringannealingheattreatmentsfollowingdeformation.Typicalannealingtwinsconfigurations:(1).Annealingtwinsatgrainboundary(2).Acompleteannealingtwinsinthewholegrain.(3).Aincompleteannealingtwins,oneendofwhoseceasesingrains.Figure5.31Schematicdiagramshowingat

6、winplaneorboundaryandtheadjacentatompositions(coloredcircles).AnnealingtwinsaretypicallyfoundinmetalsthathavetheFCCcrystalstructure.1.Microstructureandpropertiesofcold-workedmetalduringheatingWithheattemperatureiselevated,cold-workedmetalwillexperience:recovery,recrystallization

7、andgraingrowthRecovery:formingsubstructureandpropertieschangesinthestagebeforeno-distortiongraingrowth.Recrystallization:inthisstage,thedeformedgraingraduallysubstitutedbynewno-distortionequiaxedgrains.Graingrowth:inthisstage,graincontinuestogrowafterrecrystallization.Newgrainsag

8、gregatedtoasteadysizeunderthiscondition.