The martensitic transformation behavior and shape memory effect (SME) have been
investigated in a Ni-rich Ti29.6Ni50.4Hf20 high temperature shape memory alloy (SMA) in the present
study. After aging, the transformation temperatures of Ti29.6Ni50.4Hf20 alloy increase obviously due to
the precipitation of (Ti,Hf)3Ni4 particles. And the transformation sequence changes from one-step to
two-step. When the experimental alloy is aged at different temperatures for 2h, the transformation
temperatures increase rapidly with increasing the aging temperature and then change slightly with
further increasing the aging temperature. Most of the martensite variants preferentially oriented in the
aged Ti29.6Ni50.4Hf20 alloy. The aged Ti29.6Ni50.4Hf20 alloy shows the better thermal stability of
transformation temperatures than the solution-treated one because the precipitates depress the
introduction of defects during thermal cycling. In addition, the proper aged Ti29.6Ni50.4Hf20 alloy also
shows the larger SME than the solution-treated one since the precipitates strengthen the matrix
strongly.