Microstructure and corrosion behavior of as-extruded Mg-xLi-3Al-2Zn-0.2Zr alloys (x=5, 8, 11 wt.%)

The microstructure and corrosion behavior of as-extruded Mg-xLi-3Al-2Zn-0.2Zr alloys (x = 5, 8, 11 wt.%) were investigated. Intergranular corrosion is observed in alpha-Mg phase, while pitting corrosion takes place in beta-Li phase. In dual-phase LAZ832-0.2Zr alloy, micro-galvanic corrosion occurs at the alpha-Mg/beta-Li phase interface. As-extruded LAZ832-0.2Zr alloy exhibits the best corrosion resistance due to that a-Mg phase contains fewer twins, finer and sparser AlLi phase at grain boundaries, and narrower Al depleted zones compared with as-extruded LAZ532-0.2Zr alloy, and beta-Li phase exhibits smaller grain size, lower dislocation density, and fewer AlLi particles compared with as-extruded LAZ1132-0.2Zr alloy.