Influences of Sr on Microstructure and Mechanical Properties of Mg-Li-Zn Alloy

Mg-8Li-3Zn-xSr alloys with different Sr mass fractions were prepared by smelting. The effects of Sr on the microstructure and mechanical properties of the alloys in different states were investigated by optical microscopy and tensile testing. The results show that network structure compounds of Sr in the grain boundaries could be found in the cast alloy with addition of Sr, which led to brittle fracture. With the increase of Sr content, both the strength and the elongation of the cast alloys decreased. The network structure compounds of Sr were broken to tiny masses distributing dispersively in the microstructure after extrusion, which could improve the strength and ductility of the alloy. With the increase of Sr content, the strength of the extruded alloys firstly increased and then decreased, and the ductility showed a downward trend after extrusion. The tensile strength and yield strength of the extruded alloy after remelting enhanced by 15% and 30%, respectively, and the ductility decreased a little, compared with the extruded alloy.