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

摘要

If the reverse transformation of a shape memory alloy is arrested at a temperature between A_s and A_f, 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.