Microstructure and thermal characteristics of Mg–Sn alloys as phase change materials for thermal energy storage

Abstract

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.