Latent heat storage proves to be one of the most efficient ways of storing thermal energy. The selection of phase change materials is the key factor in storing thermal energy. In this study, the microstructure and thermal characteristics of Mg–24% Sn, Mg–37% Sn and Mg–50% Sn (wt%) alloys as high temperature phase change materials for thermal energy storage were investigated. The microstructure of Mg–24% Sn alloy mainly consisted of α-Mg matrix and α-Mg + Mg₂Sn eutectic phases. The microstructure of Mg–37% Sn alloy mainly consisted of α-Mg + Mg₂Sn eutectic phases. The microstructure of Mg–37% Sn alloy mainly consisted of the primary Mg₂Sn phase and α-Mg + Mg₂Sn eutectic phases. The melting enthalpies of Mg–24% Sn, Mg–37% Sn and Mg–50% Sn alloys are 105.3, 217.8 and 118.8 J g⁻¹, with the phase change temperatures of 557.6, 554.4 and 557.1 °C, respectively. The melting enthalpy of Mg–37% Sn alloy is the highest among these three alloys due to its higher proportion of α-Mg + Mg₂Sn eutectic phases, comparing with that of Mg–24% Sn and Mg–50% Sn alloys. Besides, the thermal conductivity of alloys decreases with increasing Sn content.

This study focuses on the characterization of eutectic alloy, Mg–25%Cu–15%Zn with a phase change temperature of 452.6 °C, as a phase change material (PCM) for thermal energy storage (TES). The phase composition, microstructure, phase change temperature and enthalpy of the alloy were investigated after 100, 200, 400 and 500 thermal cycles. The results indicate that no considerable phase transformation and structural change occurred, and only a small decrease in phase transition temperature and enthalpy appeared in the alloy after 500 thermal cycles, which implied that the Mg–25%Cu–15%Zn eutectic alloy had thermal reliability with respect to repeated thermal cycling, which can provide a theoretical basis for industrial application. Thermal expansion and thermal conductivity of the alloy between room temperature and melting temperature were also determined. The thermophysical properties demonstrated that the Mg–25%Cu–15%Zn eutectic alloy can be considered a potential PCM for TES.

This work studied the thermophysical properties of Mg-24%Cu, Mg-31%Cu, and Mg-45%Cu (wt.%) alloys to comprehensively consider the possibility of using them as thermal energy storage (TES) phase change materials (PCMs) used at high temperatures. The microstructure, phase composition, phase change temperatures, and enthalpy of these alloys were investigated by an electron probe micro analyzer (EPMA), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The XRD and EPMA results indicated that the binary eutectic phase composed of α-Mg and Mg₂Cu exists in the microstructure of the prepared Mg–Cu series alloys. The microstructure of Mg-24%Cu and Mg-31%Cu is composed of α-Mg matrix and binary eutectic phases, and Mg-45%Cu is composed of primary Mg₂Cu and binary eutectic phases. The number of eutectic phases is largest in Mg-31%Cu alloy. The DSC curves indicated that the onset melting temperature of Mg-24%Cu, Mg-31%Cu, and Mg-45%Cu alloys were 485, 486, and 485 °C, and the melting enthalpies were 152, 215, and 91 J/g. Thermal expansion and thermal conductivity were also determined, revealing that the Mg–Cu alloys had a low linear thermal expansion coefficient and high thermal conductivity with respect to increasing temperatures. In conclusion, the thermal properties demonstrated that the Mg–Cu alloys can be considered as a potential PCM for TES.