Microstructure and texture variation with Gd addition in extruded magnesium

The microstructure and mechanical properties of extruded Mg-xGd binary alloys (x = 1, 5, 10, and 15 wt%) were investigated, and it was found that the grain size, precipitate, texture, and tensile properties of the extruded alloys vary significantly with the Gd content. The size of the recrystallized grains gradually increases with the addition of up to 10 wt% Gd, but then rapidly decreases in the Mg-15Gd alloy due to the formation of numerous fine Mg₅Gd precipitates and their grain boundary pinning effect. With an increase in Gd content, the texture peak orientation is dramatically changed from the <2-1-11> to <0001> direction, resulting in an extraordinary rare-earth texture with basal poles parallel to the extrusion direction in the Mg-15Gd alloy. The tensile strength gradually increases with Gd addition up to 10 wt% through solid solution strengthening, and then significantly rises with 15 wt% addition due to the refined grains and abundant precipitates.