Effects of Mg Addition on Microstructure, Mechanical Properties, and Thermal Conductivity of As-Extruded Al-RE Alloys

In this study, we investigated the effect of Mg addition (0, 0.5, and 1.0 wt%) on the microstructure, mechanical properties, and thermal conductivity of as-extruded Al-RE alloys. With an increase in the Mg content from 0 to 1.0 wt%, the average grain size of the alloys decreased remarkably from 740 to 130 μm and the high-angle grain boundary fraction increased from 35 to 54%. The addition of Mg resulted in the grain refinement of the Al-1.0RE alloy because of the dynamic recrystallization caused by the solute Mg atoms during the extrusion. With an increase in the Mg content from 0.5 to 1.0 wt%, thermal conductivity of the alloy decreased from 231 to 193 W/mK because of the electric scattering caused by the solute Mg atoms. With an increase in the Mg content from 0 to 1.0 wt%, the ultimate tensile strength of the alloy increased remarkably from 74 to 120 MPa, while the strain reduced from 44 to 34%. This improvement in the strength resulted from the grain refinement and solid solution strengthening due to the solute Mg atoms. The Mg addition amount affected the thermal conductivity and strength of the alloys significantly.