Comparison about effects of Sb, Sn and Sr on as-cast microstructure and mechanical properties of AZ61–0.7Si magnesium alloy

In the paper, the effects of Sb, Sn and Sr on the as-cast microstructure and mechanical properties of AZ61–0.7Si magnesium alloy, especially on the modification and/or refinement of Mg2Si phases in the alloy, are investigated. The results indicate that adding 0.4 wt.%Sb or 0.6 wt.%Sn to AZ61–0.7Si alloy can refine the Chinese script-shaped Mg2Si phases in the alloy, but the modification of Mg2Si phases is not obvious. Oppositely, adding small amounts of Sr can obviously modify and refine the Mg2Si phases in the alloy. After adding 0.09 wt.%Sr to AZ61–0.7Si alloy, the morphology of Mg2Si phases in the alloy changes from coarse Chinese script shape to fine granule and/or irregular polygonal shapes. Accordingly, the tensile and creep properties of the Sr-containing AZ61–0.7Si alloy are greatly improved. The difference of Sb, Sn and Sr in the modification and refinement of Mg2Si phases might be related to the effects of these elements on the undercooling degree.