Effects of Sr on the microstructure,tensile and creep properties of AZ61-0.7Si magnesium alloy

The modification and refinement of Mg₂Si phase is thought to be one of the key aspects to improve the mechanical properties of Si-containing magnesium alloys. In this article, the effects of Sr on the microstructure, tensile and creep properties of AZ61-0.7Si magnesium alloy were investigated. The results indicate that adding small amounts of Sr to AZ61-0.7Si alloy can modify and refine Chinese script shaped Mg₂Si phases in the alloy. After adding 0.03wt%-0.09wt% Sr to AZ61-0.7Si alloy, the Mg₂Si phases in the alloy change from the coarse Chinese script shape to fine granule and/or irregular polygonal shapes. The modification and refinement mechanisms of Mg₂Si phases in Sr-containing AZ61-0.7Si alloys are possibly related to the reduction of growth rate and the enhancement of nucleation ratio for Mg₂Si particles during the solidification process. Owing to the modification and refinement of Mg₂Si phases, the tensile and creep properties of Sr-containing AZ61-0.7Si alloys are greatly improved.