Temperature memory effect induced by incomplete transformation in TiNi-based shape memory alloy

If the reverse transformation of a shape memory alloy is arrested at a temperature between As and Af, a kinetic stop will appear in the next complete transformation. The kinetic stop temperature has a close relation with the previous arrest temperature. This phenomenon is called temperature memory effect (TME). In this work, the TME induced by incomplete cycling in Ti–Ni and Ti–Ni–Cu plates, Ti–Ni–Nb bar was systematically investigated by performing either a single incomplete cycle, or a sequence of incomplete cycles with different arrested temperatures. Results showed that the TME is a common phenomenon in shape memory alloys, caused by a partial martensite to parent phase (M → P) transformation. On the contrary, if a partial parent phase to martensite (P → M) transformation was performed by an incomplete cycle on cooling, the next complete P → M transformation did not show any evidence of TME. Results showed that the capability to memorize the temperature is a specific characteristic of both in monoclinic martensite (B19′) and orthorhombic martensite (B19) phase.