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摘要: 对Ni52.2Mn23.8Ga24的单晶样品在马氏体相变过程中的相变潜热、磁性、电阻以及应变等物理序参量进行了测量.测量结果表明:不同的物理机制表征的相变温度有所不同.利用马氏体相变的GT关系予以分析,解释了不同测量方法获得的相变温度差别的原因.研究指出,Heusler合金Ni2MnGa的相变是分布晶格畸变类型,磁结构的变化发生在第二步晶格的非均匀切变,但相变应变与GT模型有区别.
Abstract: WehavemeasuredthetransformationtemperatureofNi52 . 2 Mn2 3 . 8Ga2 4singlecrystallinesamplebyvariousmethods,suchasDSC ,magnetization ,acmagneticsusceptibility,dcresistance,andtransformationstrain .Comparingtheexperimentalresultsbetweeneachother,wefoundthat,duetothedifferentphysicalmechanism ,variousmeasuringmethodswillgivedifferentmar tensitictransformationtemperatures.Basedontheseobservations,wesuggestamulti steplatticedeformationforthetransforma tionofNiMnGa,whichissimilartotheG Trelation .ThewholeprocessoftransformationcanbeobservedbyDSCandR Tmea surements ,whilethemagneticmeasurementsisonlysensitivetotheformationofmartensiticlattices.Themeasurementontrans formationstrainisnotsoreliableforthetransformationtemperatureastheothermeasurements,butitreallyreflectsthesituationofthesub structures,suchastwinboundaries,variantsanddefectsinthematerial.