Effect of Severe Plastic Deformation on the Behavior of Ti–Ni Shape Memory Alloys

The nanostructured TiNi-based shape-memory alloys were synthesized by severe plastic deformation (SPD), including high pressure torsion, equal-channel angular pressing, and multi-step SPD deformations (SPD plus cold rolling or drawing). It is found that the SPD processing changed the morphology of the martensite and temperature of martensite transformation. Also, we found that the mechanical and shape memory properties can be enhanced by forming nanostructures in these alloys. SPD processing renders higher strength, higher yield dislocation strength and in results—higher recovery stress (up to 1.5 GPa) and maximum reverse strain (up to 10%) of shape memory, which are desirable in various practical application.