Effect of Ca Addition on the Mechanical Properties and Thermal Conductivity of Mg-2Ga Alloy

The Ca concentration dependence of microstructure, mechanical properties and thermal conductivity of Mg-2Ga-xCa (x = 0, 0.2, 0.4 and 0.8, in wt.%) alloys has been investigated at room temperature. As the Ca content in-creases, both the average grain size and the volume fraction of dynamically recrystallised grains decrease in the as-extruded alloys, leading to an increase in yield strength. However, the increase in the number and the size of second phase particles associated with the higher Ca content brings about the reduced plasticity. In addition, a minor Ca addition (0.2% and 0.4%) to the Mg-2Ga alloy has no significant effect on the thermal conductivity, but the 0.8%Ca addition can improve the thermal conductivity of the as-cast and as-extruded Mg-2Ga alloys significantly, which is mainly related to the reduction of solute Ga atoms in alpha-Mg. Meanwhile, the as-extruded alloy exhibits the higher thermal conductivity than the corresponding as-cast alloy. The as-extruded Mg-2Ga-0.8Ca alloy exhibits the tensile yield strength of 244 MPa and the thermal conductivity of 135.5 W center dot m-1 center dot K-1. It is desirable to design Mg alloys with high strength and high thermal conductivity by selecting proper alloying elements for the formation of the precipitates other than dissolving in the Mg solution.