冷却速度对Ti-50.9%Ni形状记忆合金相变行为和组织的影响.pdf

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1、Availableonlineat、^，vIn^，．SciencedireCt．com一一．Transaetionsof奄·二ScienceDirectNonferrousMetalsSocietyofChinaPressTrans．NonferrousMet．Soc．China22(2012)2685～2690www．tnmsc．cnInfluenceofcoolingrateonphasetransformationandmicrostructureofTi一50．9％NishapememoryalloyZHANGYan—qiu，JIANGShu-yong，ZHAOYa-nan，TA

2、NGMingIndustrialTrainingCentre，HarbinEngineeringUniversity，Harbin150001，ChinaReceived23September2011；accepted5January2011Abstract：HeattreatmentofTi-50．9％Nifmolefraction)alloywasstudiedbydifierentialscanningcalorimetry,X．raydifraction．scanningelectronmicroscopeyandenergydispersiveXrayanalysistoinv

3、estigatetheinfluenceofcoolingrateontransformationbehaviorandmicrostructuresofNiTishapememoryalloy．Theexperimentalresultsshowthatthree—stagephasetransformationcanbeinducedataverylowcoolingratesuchascoolinginfurnace．Thecoolingratealsohasagreatinfluenceonthephasetransformationtemperatures．Bothmarten

4、siticstarttransformationtemperature(mJandmartensiticfinishtransformationtemperature(_f1decreasewiththedecreaseofthecoolingrate，anddecreasingthecoolingratecontributestoenhancingthe-÷austenitetransformationtemperature．Thephasetransformationhysteresisf-Mf)increaseswiththedecreaseofthecoolingrate．Hea

5、ttreatmentisunabletoeliminatethetexturesformedinhotworkingofNiTisample．butcanweakentheintensityofthem．Thecoolingratehaslittleinfluenceonthegrainsize．Kevwords：NiTialloy；shapememoryalloy；phasetransformation；coolingrate：martensitictransformationtemperature：austenitetransformationtemperatureprocessin

6、gtechniquesandsoonn～41．1IntrOductiOnOverthelastdecades，manyscholarshavestudiedthephase仃ansformationbehaviorofNiTiSMA『5—131．Near．．equiatomicnicke1．．titaniumshapememoryHowever．manystudiesignoredtheinfluenceofcoolingalloy(NiTiSMA1isthemostwidelyusedshapememoryrateonthephasetransformationbehaviorofNi

7、TiSMA．materialduetoitsgoodmechanicalproperties．excellentInfact．coolingrateisreallyanotherconcernintestingshapememoryeffectandsuperelasticityaswellasaSMAs．whichisparticularlyimportantinbulkSMAsdueperfectbiologicalcompat