Study of Temperature Memory Effect in TiNi-Based Shape Memory Alloys Thin Films

If a reverse transformation of a shape memory alloy (SMA) is arrested at a temperature Ts between As and Af (As Ts Af) and cooled below Mf, a kinetic stop will appear in the next complete transformation cycle. The kinetic stop temperature is closely related to the previous arrested temperature. This phenomenon is named temperature memory effect (TME). In this work, the temperature memory effect in TiNi and TiNiCu thin films is systematically investigated by performing either a single incomplete cycle, or a sequence of incomplete cycles with different arrested temperatures. Results show that the TME is a common phenomenon in shape memory alloy, and is related to both the strain energy between martensites and coherent strain between parent phase and martensite.