Effect of Li content on microstructure and mechanical property of Mg-xLi-3(Al-Si) alloys

Mg-4Li-3(Al-Si), Mg-8Li-3(Al-Si) and Mg-12Li-3(Al-Si) alloys based on the alpha-Mg, alpha-Mg+beta-Li, beta-Li phases, respectively, were produced to investigate the effect of alloying with Al-Si eutectic on the microstructure and mechanical properties of the three alloys. Alloying with the Al-Si eutectic of Mg-xLi (x=4, 8 and 12 wt.%) alloys caused the formation of different types of Al-Li precipitates: Al3Li, AlLi and Li3Al2, respectively. Also, considerable quantities of Mg2Si phase particles were found in the three alloys. The results of tensile tests showed that the Mg-4Li-3(Al-Si) alloy exhibited the highest ultimate tensile strength (UTS) of 249 MPa but the lowest elongation of 6.3%. The Mg-12Li-3(Al-Si) alloy had the highest elongation of 26% but the lowest UTS of 173 MPa. The different mechanical properties were attributed to the different crystal structures of the three alloys and the precipitate with different type, morphology and distribution.