Superelasticity of TiNi thin films induced by cyclic nanoindentation deformation at nanoscale

Cyclic deformation behavior of submicron-thick austenitic TiNi film at nanoscale was studied by nanoindentation. It was found that excellent superelasticity was achieved and stabilized after certain times of indentation deformation, and lower loading would require more deformation cycles to achieve superelasticity stabilization. Loss of superelasticity was attributed to the lower yield strength of austenite than the critical stress required for stress-induced martensitic transformation. Both introduced dislocations and grain growth during cyclic deformations contributed to the superelasticity and its steady-state achievement.