Influence of aging modes on microstructure and mechanical properties of AZ80 magnesium alloy

The microstructure and mechanical properties of AZ80 magnesium alloy after solid solution and aging treatments were studied by using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) as well as tensile testing. The results indicated that beta-Mg17Al12 phase was getting to distribute discontinuously along the grain boundary after treated at 395 degrees C ageing for 12 h followed by water-cooling, but it did not dissolve into alpha-Mg completely. The residual 18-Mg17Al12 phase distributed along the grain boundary and had block-like or island shapes. The size of a-Mg was getting to be coarsening but not significantly. The beta-Mg17Al12 precipitates appeared in discontinuous and continuous patterns from supersaturated a-Mg solid solution after aged at 200 degrees C. The precipitation patterns were associated with the aging time essentially. The tensile strength and elongation of the alloy increased significantly but the hardness and yield strength decreased after solid solution treatment. However, with the prolonging of aging time, the hardness and strength of alloy increased while the ductility decreased.