Effect of Aging on Microstructure and Martensitic Transformation in Ti-Zr-Ni Shape Memory Alloys

Effect of isothermal aging on martensitic transformation temperatures, mechanical properties and microstructure was investigated for a Ni-rich Ti-Zr-Ni shape memory alloy at temperatures ranging from 673 K to 773 K. The aging behaviour was two stage process: the first stage associated with an increase in the Vickers hardness and a decrease in martensitic transformation temperatures and the second stage with a decrease in the hardness and increase in the transformation temperatures. Second stage was also characterized by the appearance of nano-scale precipitates, which has never been reported.