Effect of Zr, Mn and Sc additions on the grain size of Mg–Gd alloy

The effect of Zr, Mn and Mn + Sc additions on the grain size of Mg–10Gd alloy has been investigated and the grain refinement mechanisms are also suggested. The results reveal that the addition of Zr results in a significant grain refinement of as-cast Mg–10Gd alloy by generating nucleants. However, it cannot restrict grain growth during homogenization treatment at 520 °C, and completely loss the grain refining effect for extruded alloy sample. Mn has a negligible effect on grain size of as-cast Mg–10Gd alloy, but α-Mn particles precipitate during homogenization treatment, which helps to refine the grains of extruded alloy sample due to α-Mn particles restricting recrystallization grain growth during extrusion. Successful grain refinement can be obtained by the addition of Mn + Sc. It is effective to refine microstructure of as-cast Mg–10Gd alloy, inhibit grain growth during homogenization treatment and also have a significant grain refining effect on extruded Mg–10Gd alloy sample, which are ascribed to the precipitation of a large number of Mn2Sc particles.