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 degrees 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 alpha-Mn particles precipitate during homogenization treatment, which helps to refine the grains of extruded alloy sample due to alpha-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. (C) 2008 Elsevier B.V. All rights reserved