Effects of Ni/Ti ratio and heat-treatment on transformation temperature, mechanical properties and shape recovery strain of Ni-Ti-Nb alloy

Ni-Ti-Nb wide hysteresis shape memory alloys of three Ni/Ti ratio components were manufactured by vacuum induction melting. The transformation temperature, mechanical properties and recovery strain were studied by using differential scanning calorimeter and material testing machine. It shows that with Ni/Ti ratio increase, the transformation temperature and mechanical properties decrease. Shape recovery strain is higher when Ni/Ti ratio is 1.068, with recovery strain range from 6.8 to 7.5. The faster the cooling rate after annealing, the higher is the transformation temperature, and the lower are the mechanical properties and recovery strain.