Effects of Sb Content on Microstructure and Mechanical Properties of As-cast Mg-4Al-1Zn-1Si Alloy

The effects of Sb modification on the microstructure and properties of Mg-4Al-1Zn-1Si alloy were investigated.The result show that the Mg3Sb2 phase generates in the alloy by the addition of 0.25wt% Sb.Large numbers of coarse Chinese script shaped Mg2Si phases which accumulated originally in the grain boundary are refined,which dispersed in the grain boundary and inside.Meanwhile,a few of polygonal block Mg2Si particles appear,and the mechanical properties are improved.When the content of Sb is 0.5wt%,the Mg2Si particle size decreases rapidly and changes into block and rod shapes.At the same time,the room temperature and elevated temperature mechanical properties of the alloy can reach the maximum.When the content of Sb is 0.75wt%,the Mg2Si particle size does not change obviously,but they start to aggregate.When the content of Sb is 1.0wt%,the Mg2Si phases change into large Chinese script shaped again,and the mechanical properties of the alloy reduce.