Microstructure and Solidification Behavior of Permanent-Mould-Cast Mg-9Li-3Al-XSr Magnesium Alloy

Mg-9Li-3Al-xSr (x=0wt%, 1.0wt%, 2.0wt%, 2.5wt%) magnesium alloys with different ingot sizees were prepared in furnace under the protection of argon atmosphere. The as-cast microstructure and solidification characteristics of Mg-9Li-3Al-xSr alloys were experimentally examined using optical microscopy, scanning electron microscopy and X-ray diffraction. The results indicate that Mg-9Li-3Al-xSr alloys are composed of α-Mg, β-Li, Mg17Al12, AlLi and Al4Sr phase. The grains of Φ10mm ingots are much smaller and the compound phase distributes much more uniformly than Φ90mm ingots. Solidification process of Mg-9Li-3Al-xSr alloys follows the principle of eutectic solidification. The microstructure of the series as-cast alloys is typical rodlike eutectic microstructure.