Microstructure and mechanical properties of as-cast and solid solution treated Mg−8Li−xAl−yZn alloys

Abstract

The effects of Al/Zn ratio (mass ratio) on microstructure and mechanical properties of the Mg−8Li alloy were investigated. The results indicate that in the as-cast Mg−8Li−xAl−yZn (x+y=5) alloys (LAZ alloys), when the Al/Zn ratio is 1:4 and 2:3, the secondary phases are mainly AlLi and MgLiZn phases; when the Al/Zn ratio is 3:2 and 4:1, the secondary phases are mainly AlLi and MgLi2Al phases. The decomposition temperature of MgLiZn phase is about 300 °C and the decomposition temperatures of AlLi phase and MgLi2Al phase are higher (∼350 °C). Solid solution strengthening is the main factor for the improvement of strength of Mg−8Li−xAl−yZn alloys. The Mg−8Li−3Al−2Zn alloy after solution treatment at 350 °C for 4 h has the best comprehensive mechanical properties (yield strength of 272.5 MPa, ultimate tensile strength of 315.0 MPa and elongation of 3.4%) among the studied as-cast and solid solution treated Mg−8Li−xAl−yZn alloys.