Thermal storage properties of NiTiCu shape memory alloys with different phase transition behaviors

The development of thermal energy storage and thermal management technologies based on phase change materials (PCM) represents a significant opportunity for regulating energy supply and demand, and realizing sustainable development. Recent studies have demonstrated the efficacy of shape memory alloys as a solid-solid phase change material. In order to investigate the effect of phase change behavior on thermal storage performance, Ni 50-x Ti 50 Cu x (x = 20, 22.5, 25, 27.5, 30 at%) alloys with one-step phase change and Ni 40+x Ti 50-x Cu 10 (x = -1, 0, 1 at%) alloys with two-step phase change are comparatively analyzed. The focus was on the thermophysical properties of the two series of alloys, such as density, specific heat capacity and thermal conductivity, as well as the phase transition behavior, microstructure and thermal cycle stability studies. The findings demonstrate that, in comparison to conventional organic and inorganic phase change materials, the two alloys display superior thermal storage characteristics, including higher density and enhanced thermal conductivity, as well as superior figure of merit (FOM) that are significantly superior to those of conventional phase change materials. In comparison, considering the phase transition temperature, FOM and thermal cycling stability, one-step phase transition alloys have better overall thermal performance than two-step phase transition alloys, which demonstrates great promise for applications in areas such as efficient thermal energy storage, rapid thermal cycling thermal management.