Microstructures and tensile properties of as-cast Mg-5Sn-1Si magnesium alloy modified with trace elements of Y, Bi, Sb and Sr
Heshuai Yu, Xuefeng Guo, Hongbao Cui
Abstract
The microstructures and mechanical properties of as-cast Mg-5Sn-1Si magnesium alloy modified with trace elements Y, Bi, Sb and Sr were investigated and compared. Results show that the microstructure of the as-cast Mg-5Sn-1Si alloy consists of α-Mg, Mg 2 Si, Mg 2 Sn and Mg 2 (Si x Sn 1− x ) phases. After adding 0.8wt.% Y, 0.3wt.% Bi, 0.9wt.% Sb and 0.9wt.% Sr, respectively into the Mg-5Sn-1Si magnesium alloy, Mg 24 Y 5 , Mg 3 Bi 2 , Mg 3 Sb 2 and Mg 2 Sr phases are precipitated accordingly. Trace elements can refine α-Mg grain and Chinese script-shaped Mg 2 Si phase. Refinement efficiency of different trace elements on α-Mg grain and Mg 2 Si phase is varied. Sr element has the best refinement effect, followed by Sb and Bi, while Y has the least refinement effect. Mg-5Sn-1Si-0.9Sr alloy has higher tensile properties than the other three modified alloys. The refinement mechanism of Y, Bi and Sr elements on Mg-5Sn-1Si magnesium alloy can be explained by the growth restriction factors and the solute undercooling. For Mg-5Sn-1Si-0.9Sb alloy, the heterogeneous nuclei of Mg 3 Sb 2 phase is the main reason for the refinement of grains and second phases.