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

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 degrees C and the decomposition temperatures of AlLi phase and MgLi2Al phase are higher (similar to 350 degrees 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 degrees 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.

Automated summary

The Al/Zn ratio significantly affects the microstructure and mechanical properties of Mg-8Li alloy, with solid solution strengthening being the main factor for strength improvement. Among the studied alloys, Mg-8Li-3Al-2Zn alloy after solution treatment at 350°C for 4 hours exhibits the best comprehensive mechanical properties.