az31镁合金静态再结晶过程及机理的研究论文

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1、重庆大学硕士学位论文英文摘要ABSTRACTDuetotheexcellentphysicalpropertiessuchaslowdensity,highspecificstrengthandstiffness,magnesium(Mg)alloysareveryattractiveinavarietyoftechnicalapplication,especiallyinautomotiveandaircraftindustries.Asahexagonalclose-packed(hcp)metal,Mgalloysexhibitp

2、oorductilityandcoldworkabilityowingtotheirinsufficientslipsystemsespeciallyatroomtemperature,whichrestrictsitswidespreadapplication.Wegetcomplexmagnesiumalloypartsbycastingmethodusually,butitcausedmuchproblemssuchasinclusionandcompositionsegregationect.Weldingprocessespl

3、ayacriticalroleintheboardapplicationofmagnesiumalloysbyjoiningeasily-castsegmentsintomorecomplexpartsifitisreliable.Recrystallizationisimportantformagnesiumalloyproductprocessingbecauseitcansoftenthemetal、improvemicrostructureuniformityandcontrolgrainsize.Researchsonrecr

4、ystallizationinthispaperisdividedintotwoparts.Firstofall,westudiedtheeffectoftwinboundariesonstaticrecrystallizationofcastmagnesiumalloy.As-castAZ31magnesiumalloywerecompressedorforgedby4%、8%and12%,andthenitannealedat200℃or300℃fordifferenttime.Wecomparedtheeffectofdeform

5、ationmodeandstrianontwinningprocessandthedifferenceofrecrystallizationphenomenonunderdifferentconditionsby,XRDandEBSDexperimentalmethod.Theinfluenceofdifferenttwinboundarisonmagnesiumalloystaticrecrystallizationandthegrainnucleationandgrowupmechanismwerediscussed.Theresu

6、ltsshowthattwinsareshortandtheirorientationsaredisorderedinforgingsamples,buttwinsincompressionsamplesarelongandnarrowwhichhavethesameorientationandexistwithgroups.Thesemorphologydifferencesarerelatedtothedistinctrateoftwodeformationmode.Wefound{10-11}compressiontwinboun

7、drywasmucheasytonucleatethan{10-12}tensiletwinboundry.Thenumberof{10-11-{10-12}doubletwinsarerelatedtodeformationstrainratherthandeformationrate,andwefoundthistwinvariantsisrelativestableduringannealingprocesswhichisdifferentfromTDRXtheory.Wealsoputforwardthe"twinboundar

8、ybulgenucleation"theorytoexplainssomespecialphenomenonofnucleationontwinboundary.Secondly,wediscussedth