Microstructure and Mechanical Properties of Mg-8Li-4Al-0.3Y Alloys

The microstructure and mechanical properties of as-cast, solution-treated and as-extruded Mg-8Li-4Al-0.3Y alloys were studied by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction analysis (XRD) and tensile test machines. The results show that as-cast Mg-8Li-4Al-0.3Y alloy is composed of alpha-Mg, beta-Li, Al2Y, AlLi and MgAlLi2 phases. MgAlLi2 compound at the grain boundaries disappears in the solution-treated alloy and most of AlLi phase decompose and dissolve into the matrix, while only part of larger AlLi particles are left during the solution treatment. The microstructure of the as-extruded alloy is refined obviously and more uniform due to the dynamic recrystallization during the extrusion process. The microhardness of the solution-treated alloy is much higher than that of as-cast one due to solution strengthening. The mechanical properties of Mg-8Li-4Al-0.3Y alloys are improved a lot by extrusion and the ultimate strength and elongation of the extrude alloy reach 208 MPa and 25.1%, respectively.