Thermal cycling stability of ultrafine-grained TiNi shape memory alloys processed by equal channel angular pressing

The thermal cycling stability of martensitic transformation in two different TiNi alloys processed by equal channel angular pressing (ECAP) was investigated. The transformation behavior of the as-ECAP-processed Ti49.2Ni50.8 alloy was more stable than that of Ti50.2Ni49.8 alloy. Annealing at a temperature below 500 °C did not influence the thermal cycling stability of the Ti49.2Ni50.8 alloy. The relationship between thermal cycling stability and composition and annealing treatment was discussed based on the grain size evolution.