On the orientation and temperature dependence of the superelasticity and elastocaloric effect of Cu-Al-Mn-(Ni, Mo, Cr) shape memory alloys

This study systematically reveals the influence of the crystal orientation and operating temperature on the superelasticity and elastocaloric effect of single-crystal Cu-Al-Mn-(Ni, Mo, Cr) shape memory alloys. These single crystals were prepared using the abnormal grain growth method to produce samples having orientations classified as approximately [0 0 1]β, [1 0 1]β, and [1 1 1]β. The experimental results indicated that significant differences in energy dissipation and elastocaloric cooling capacity among the three types of orientations, which were attributed to the different numbers of induced martensitic variants and the magnitude of transformation fraction. Compared with the approximately [0 0 1]β and [1 1 1]β orientations, the approximately [1 0 1]β orientation was considered the preferred choice for a solid-state refrigerant due to its smaller energy dissipation and the pronounced coefficient of performance of the material. On the other hand, the superelastic and elastocaloric properties of the three types of orientations changed as the testing temperature increased, which was attributed to atomic ordering (from 80 °C to 140 °C) and the formation of bainitic α (above 140 °C). This study identified the preferred orientation for solid-state refrigerant applications and comprehensively analyzed the influence of the operating environment on Cu-Al-Mn-(Ni, Mo, Cr) shape memory alloys for solid-state refrigeration.