Effect of extrusion ratio on microstructure and mechanical properties of Mg-8Li-3Al-2Zn-0.5Y alloy with duplex structure

This study was undertaken to evaluate the effect of extrusion ratio on the microstructure and mechanical properties of Mg-8Li-3Al-2Zn-0.5Y (wt%) alloy, which was prepared by casting and then deformed by hot extrusion at 200 ℃ with four different ratios of 4:1, 9:1, 16:1 and 25:1, respectively. It was identified that the as-cast Mg-8Li-3Al-2Zn-0.5Y alloy is composed of α-Mg, β-Li, AlLi, MgLi2Al and Al2Y phases. After hot extrusion with all four ratios, the microstructure was significantly refined. The mechanical properties of Mg-8Li-3Al-2Zn-0.5Y alloy at room temperature were improved, mainly caused by grain refinement and precipitation strengthening. As the extrusion ratio increases from 4 to 25, the grains of the alloy become elongated and refined, and the tensile properties first increase and then decline. Among all the tested alloys, the alloy with the extrusion ratio of 16 exhibits the highest yield strength, ultimate tensile strength and elongation of 214 MPa, 243 MPa and 41%. In addition, the fracture behavior and strengthening mechanism of the studied alloys were also investigated systematically.