Simultaneous Enhancement of Thermal Conductivity and Mechanical Properties of EZ42 Magnesium Alloy by Ca Microalloying

This study investigated the influence of Ca microalloying on the microstructure, thermal conductivity, and mechanical properties of the EZ42 magnesium alloy. The results indicated that Ca, Mg, and Zn atoms could form stable submicron Ca2Mg6Zn3 precipitates during the thermal deformation process, effectively inhibiting the growth of dynamic recrystallization grains. The refinement of grain size and the strengthening effect of submicron Ca2Mg6Zn3 precipitates increased the yield strength of the as-extruded EZG420 alloy to 162 MPa. The addition of Ca weakened the basal textures and, coupled with the effect of grain refinement, led to improved plasticity. The precipitation of the Ca2Mg6Zn3 phases reduced the residual solid solution Zn atoms in the matrix, and the Ca2Mg6Zn3 precipitates were incoherent with the matrix. These factors combined gave the as-extruded EZG420 alloy excellent room temperature thermal conductivity, reaching 139.6 W/(m·k). By regulating the precipitation behavior of the microalloying elements, the thermal and mechanical properties of the magnesium alloy were simultaneously improved.