Thermo-mechanical cyclic transformation behavior of Ti-Ni shape memory alloy wire

The present paper deals with recovery strain and fatigue life of Ti49.8Ni50.2 shape memory alloy (SMA) wire on thermo-mechanical cycling (TMC). Recovery strain of SMA wire with several heat treatments shows different changes when being subjected to TMC at a series of constant loads. These changes are significant in the initial 200 cycles and recovery strain tends to reach a steady state in the further cycling. The effect of heat treatment on the fatigue life is analyzed, the SMA wire with shorter heat treatment exhibits lower fatigue life while higher recovery strain. Transformation temperatures of SMA wire on TMC is investigated by electrical resistance measurements. It was found that both annealing time and TMC has obvious influence on transformation behavior.