Structure, phase transformation and superelasticity of nanocrystalline Ti-50.9 at. % Ni alloy

We investigate the effect of heat treatments of nanocristalline Ni-rich NiTi alloy on the precipitation of Ti3Ni4 phase in the alloys grain/subgrain structure after annealing at 300°C and at 400°C, as well as on martensitic transformations and inelastic behavior. It is shown that the increase in Ti3Ni4 precipitate size and change in their distribution in the substrucrure is accompanied by a shift of martensitic transformation temperatures, leading to the occurrence of the R-phase, and ensuring change of mechanical responses from pseudoelastic to shape memory.