Indentation and two-way shape memory in a NiTi polycrystalline shape-memory alloy

This paper reports a systematic study on indentation by a Vickers indenter and two-way shape memory in subsequent thermal cycling of a NiTi polycrystalline shape-memory alloy. It was found that, at a lower temperature, the indent is sink-in, while at a higher temperature, it is pile-up. However, after heating all indents are pile-up. The two-way shape memory is almost linearly dependent on the maximum indentation load but independent of the indentation temperature. The mechanism behind these phenomena is explained. The stability of two-way shape memory was also investigated.