Effect of heat aging on thermal and mechanical properties of Ti-Ni-Nb shape memory alloy

This paper describes the effect of heat aging on thermal and mechanical properties of shape memory alloy. The materials used in this Study are Ti-Ni-(6-12 at%)Nb shape memory alloy. The tensile tests at 173 K and the heating-cooling tests under constrained strain condition were carried out using the specimens aged at 561 K for between 20 h and 1000 It in normal water chemistry. The martensite start temperature rapidly decreases in the initial short aging time, but there is little further decrease of the martensite start temperature with aging time more than 100h. The recovery stress gradually increases with aging time, but on the contrary, the aging time of more than 500 h causes reduction of the recovery stress.