Microstructure optimization and mechanical properties of lightweight Al-Mg2Si in-situ composite

This research investigated the effects of Er addition (01 wt.%), cooling rate and hot extrusion on the microstructure, hardness and tensile properties of Al-15 wt.% Mg2Si in-situ composite. The results show that addition of Er with high concentrations changes primary Mg2Si particles from irregularly shaped to polygonal shaped and also transforms needle-shaped Al5FeSi compounds into a short rod morphology. Microstructural studies revealed that water-cooling is more beneficial to acquire polygon shaped primary Mg2Si and fish-bone Al3Er. Through hot extrusion, the networks of eutectic Mg2Si phase and fish-bone Al3Er compound are broken. In addition, the results of tensile testing show that both Er addition and water-cooling improve the ultimate tensile strength and elongation. The optimum tensile behavior was achieved by adding 0.6 wt.% Er to the water-cooled Al-Mg2Si composite after hot extrusion.