The temperature memory effect and the influence of thermo-mechanical cycling in shape memory alloys

Apart from the well-known shape memory effect (SME), the temperature memory effect (TME), i.e., the ability of a material to remember the heating interrupted temperature in the previous thermal cycle, is another interesting phenomenon observed in many shape memory alloys (SMAs). In this paper, based on previous and current experimental observations, we propose a phenomenological model to reproduce the TME. Subsequently, we study the influence of thermo-mechanical cycling (uniaxial tension) on the TME in a polycrystalline NiTi SMA wire (0.51 mm diameter). The maximum tensile strain in each cycle is 10%, which is beyond its elastic limit. The evolution of the peak transition temperature in the forward and reverse transformations and the TME upon thermo-mechanical cycling is investigated by differential scanning calorimetry. It is proved that the TME is a stable intrinsic phenomenon and can be utilized even under severe thermo-mechanical conditions.