Microstructure evolution and improvement of thermal conductivity in Mg–2Sn alloy induced by La addition

Rare earth elements are commonly used to improve the properties of magnesium alloys. In this paper, the effects of various La contents on the microstructure and thermal properties of Mg–2Sn alloys were investigated. Cooling curve thermal analysis technique was adopted to reveal the microstructure evolution of Mg-2Sn-xLa alloys. La addition contributed a new eutectic reaction to occur at 639 °C and the eutectic structure was determined to be LaMgSn phase. Mg12La, Mg2Sn and matrix precipitated phases may be generated in the microstructure with further increase of La content. The thermal conductivity of Mg–2Sn alloy can be effectively improved by La addition and the maximum value 149 W/(m·K) was achieved at the Sn/La atomic ratio of 1. The thermal conductivity of Mg-2Sn-2.3La alloy could further increase to 152 W/(m·K) after solution heat treatment. The addition of La reduced the amount of solute atoms and eliminated the Sn enriched region, resulted in a rapid increase in the thermal conductivity of the Mg–2Sn alloy. The spheroidization of Mg12La phase contributed to the further improvement of the thermal conductivity after solution treatment.