Temperature memory effect of martensite and R-phase transformation in TiNi-based shape memory alloys

The temperature memory effect (TME) phenomenon in the martensite or R-phase to parent phase transformation in TiNi-based shape memory alloys was studied by differential scanning calorimetry (DSC). It was found that an incomplete thermal cycle upon heating of SMAs (arrested at a temperature between austenite transformation start and finish temperatures or the start and finish temperatures of R-phase to parent transformation) will induce a kinetic stop in the next complete thermal cycle. The kinetic stop temperature was closely related to the previous arrested temperature. Results showed that the TME is a common phenomenon in shape memory alloys, caused by a partial martensite or R-phase to parent phase transformation. The TME in the R-phase transformation is weaker than that in the martensitic transformation. The TME can be strengthened by performing many repetitions of partial transformation at the same arrested temperature.