Microstructure and Thermal Conductivity of As-Cast and As-Solutionized Mg-Rare Earth Binary Alloys

The microstructure and thermal conductivity of four groups of Mg-rare earth (RE) binary alloys (Mg-Ce, Mg-Nd, Mg-Y and Mg-Gd) in as-cast and as-solutionized states were systematically studied. Thermal conductivity was measured on a Netzsch LFA457 using laser flash method at room temperature. Results indicated that for as-cast alloys, the volume fraction of second phases increased with the increase of alloying elements. After solutionizing treatment, a part or most of second phases were dissolved in alpha-gmatrix, except for Mg-Ce alloys. The thermal conductivity of as-cast and as-solutionized Mg-RE alloys decreased with the increase of concentrations. The thermal conductivity of as-solutionized Mg-Nd, Mg-Y and Mg-Gd alloys was lower than that of as-cast alloys. Thermal conductivity of as-solutionized Mg-Ce alloys was higher than that of as-cast alloys, because of the elimination of lattice defects and fine dispersed particles during solutionizing treatment. Different RE elements have different influences on the thermal conductivity of Mg alloys in the following order: Ce < Nd< Y< Gd. Ce has the minimum effect on thermal conductivity of Mg alloys, because of the very low solubility of Ce in the alpha-Mgmatrix. The variations in the atomic radius of the solute elements with Mg atom (Delta r), valence, configuration of extranuclear electron of the solute atoms, and the maximum solid solubility of elements in the alpha-Mg matrix were suggested to be the main reasons for the differences in thermal conductivity of resulting Mg-RE alloys. (C) 2016 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.