有应力作用时效下的ni4ti3相沉淀行为模拟

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1、TransactionsofNonferrousMetals受Av·ai：labl；eo，nSlinecaitewwnwc．secieDnceidrierect．ctornSocietyofChinaPressTrans．NonferrousMet．Soc．China22(2012)2578—2585www．tnmsc．cnModelingofNiaTi3precipitationduringstress-freeandstress--assistedagingofbi·-crystallineNiTishapememoryalloysKEChang．bo一，CAOShan．sha

2、n。MAXiao，ZHANGXin-ping，1．SchoolofMechanicalandAutomotiveEngineering，SouthChinaUniversityofTechnology,Guangzhou510640，China；2．SchoolofMaterialsScienceandEngineering，SouthChinaUniversityofTechnology,Guangzhou510640，ChinaReceived9July2012；accepted6August2012Abstract：Thephasefieldmethodwasappliedt

3、ostudythemicrostructureevolutionofNi4Ti3precipitatesduringstress-freeandstress．assistedagingofbi．crystallineNiTishapememoryalloys(SAMs)withtwodiferentinitialNi-contentsof51．5％and52．5％(molefraction)，respectively．Thesimulationresultsshowthat，duringstress—freeagingoftheNiTialloywithalowsupersatur

4、ationofNi(i．e．，Ti一51．5％Ni)，theNi4Ti3precipitatesexhibitaheterogeneousdistributionwithahighnumberdensityofparticlesatthegrainboundary,leavingmostofthegraininteriorsfreeofprecipitates；whilefortheNiTialloywithahighsupersaturationofNi(i．e．，Ti一52．5％Ni)，theNi4Ti3preci[)itatesshowahomogeneousdistribu

5、tionacrosstheentiresimulationsystem．Thestress-assistedagingcangiverisetohomogeneousdistributionoftheprecipitates，regardlessoftheinitialNi—content；however,thedistributionofvarianttypewithinthetwograinsisheterogeneous．Keywords：NiTishapememoryalloy；Ni4Ti3precipitate；low-anglegrainboundary；martens

6、itictransformation；phasefieldsimulationdeformation『41．ThestudyoftheinfluenceofNi4Ti3on1Introductionmartensitic仃ansformationwasmainlyperformedbyexperimenta1observationandcharacterizationsuchasNear．equiatomicNiTialloyshaveattractedagreatdiferentialscanningcalorimetry(DSC)andinsitudeaIofinterests

7、inthepastdecadesonaccountoftransmissionelectronmicroscopy(TEM)[5—7】．Thusfar,excellentshapememoryefectandsuperelasticproperty．ithasbeenwellrecognizedthatthemartensiticTheyhavebecomeoneofthemostimportantmetaltransformationbehaviorinNiTiSM