Effect of Heat Treatment Temperature on Thermomechanical Properties of Ti-Ni Shape Memory Alloy

抄録

  This study discusses the suitable heat treatment condition for Ti-50.3at%Ni shape memory alloy. Tensile and tensile loading-unloading tests carried out using the heat-treated Ti-50.3at%Ni wire at the temperatures of A_f+30K, A_f+40K and A_f+50K which are 30K, 40K and 50K higher than austenite finish temperature A_f, respectively, and the effects of heat treatment temperature (HTT) and environmental temperature on thermomechanical properties has been investigated. The breaking strains of HTT=673K, 723K and 773K are almost the same value and do not vary in the temperature range from A_f +30K to A_f + 40K. However, the breaking strain of HTT=773K rapidly increases at A_f + 50K. There is hardly difference of the plastic strain between HTT=673K and 773K under the applied strain of 5%. However, the plastic strain of HTT=773K is lager than that of HTT=673K under the applied strain of 10%. The recoverable strain energy of HTT=673K is twice as large as that of HTT=773K both under the applied strain of 5% and 10%. This means that the Ti-50.3at%Ni wire heat-treated at 673K can store almost twice as much energy as the wire heat-treated at 773K.