Investigation on the two-way shape memory effect and alternating current electrothermal driving characteristics of TiNiCu shape memory alloy

Two-way shape memory effect (TWSME) was introduced in a narrow hysteresis TiNiCu shape memory alloy spring by thermomechnical training after heat treatment. The TWSME spring can contract upon heating and extend upon cooling. The effect of heat treatment on the TWSME of the shape memory alloy springs has been investigated. The results showed that the TWSME recovery rate of the spring could be high up to 58% after being thermomechnical trained 75 cycles for the specimen heat treated at 500°C for 1 h. The transformation temperatures were also investigated by Differential Scanning Calorimeter (DSC) during thermomechanical training. The electrothermal driving characteristics of the TWSME springs were also investigated with alternating current density of 2.55–17.8 A/mm2. It is found that the time response (the time interval between the start and the end of the spring's shape change) and the maximum contraction rate were greatly depended on the magnitude of the electrical current density.