The functional fatigue behaviour of two near equi-atomic NiTi shape memory alloy wires obtained from different sources were evaluated. Results showed that though the wires had similar transformation temperatures and mechanical properties, their functional fatigue behaviour upon thermo-mechanical cycling was at variance. Under a variable stress in the range 150-450 MPa and 4% recovery strain, one of the wires showed better stability, and significantly higher fatigue life (~30,000 cycles) than the other (~3,500 cycles). The reasons for such wide variation in thermo-mechanical fatigue behaviour have been discussed in this paper
