Functional Shape Recovery Response of Heat-Treated NiTiCu SHAPE Memory Alloy Wire

NiTiCu shape memory alloy wires are promising functional materials for applications requiring controlled deformation and shape recovery. In this study, the functional shape recovery response of a commercial 0.5 mm diameter NiTiCu wire was investigated after heat treatment at 450 °C for different durations. The untreated wire and the wires heat-treated for 30 and 60 min in sealed quartz tubes were comparatively evaluated. Differential scanning calorimetry was used as an auxiliary characterization method to determine the appropriate temperature for the recovery test rather than as the main basis of discussion. The DSC results showed that heat treatment shifted the transformation temperatures to higher values and narrowed the transformation intervals. Based on the Af temperatures, bend and free recovery tests were carried out at 55 ± 2 °C. The recovery behavior was evaluated after five repeated bending and free recovery measurements for each condition. The untreated sample showed a high recovery ratio of 98.7 ± 0.1%, while the values increased to 99.5 ± 0.3% and 99.75 ± 0.1% after 30 and 60 min of heat treatment, respectively. These results indicate that heat treatment at 450 °C preserved the functional recovery capability of the NiTiCu wire and slightly improved its bending-related shape recovery response, with the best performance obtained after 60 min of heat treatment.