Design of Heat-Dissipating Mg–La–Zn Alloys Based on Thermodynamic Calculations

Abstract

How to design alloys with good heat-dissipating capacity and predict the thermal conductivities of Mg–La–Zn alloys is an interesting and important topic. In this study, nine alloys were designed by thermodynamic phase diagram calculations in Mg–La–Zn system. Their compositions were determined by controlling phase components and the solid solubility of Zn in α-Mg. The temperature dependence of thermal conductivities of as-cast Mg–xLa–yZn (x = 0.18–0.37 at.%, y = 0–2.55 at.%) alloys were investigated using flash method. Phase compositions and microstructure of heat-dissipating Mg–La–Zn alloys were also analyzed using X-ray diffraction and scanning electron microscopy. Considering the thermal conductivity of single-phase LaMg12 alloy measured in the present work, the thermal conductivities of Mg–La–Zn alloys in the two-phase regions (α-Mg + LaMg12) were also evaluated using the CALPHAD method. Results indicated that the Mg–La–Zn alloys with secondary phase (LaMg12) exhibited higher thermal conductivity than those with τ1, and the high solid solubility of Zn in α-Mg was detrimental to the heat dissipation of Mg alloys. Meanwhile, the calculated thermal conductivities show good agreements with the corresponding experimental values.