Optimization of heat treatment condition of nonflammable Mg-Al-Ca alloys with high thermal conductivity

Our previous study found that the thermal conductivity of nonflammable Mg-Al-Ca alloys is improved by heat treatment. Heat-treated Mg-Al-Ca alloys exhibited a high thermal conductivity of 100–130 W m−1 K−1 because of C15 (Al2Ca) compound precipitation in the α-Mg phase. In this study, the optimal heat treatment condition and the effect of C15 precipitation behavior on thermal conductivity were investigated using Mg91.98Al5Ca3Mn0.02 alloys. The thermal conductivity saturated at approximately 120 W m−1 K−1 in the shortest time at a heat treatment temperature of 673 K. This suggests that the nucleation rate of the C15 compounds could reach the highest at 673 K. Through the formation of dense, long, and thick C15 compounds, thermal conductivity increased with decreasing Al concentration in the α-Mg matrix.