Microstructures and tensile properties of hot-extruded Al matrix composites containing different amounts of Mg2Si

The effect of hot extrusion process on the microstructure and tensile properties of aluminum matrix composite containing 15, 20, 25 and 30 wt% Mg2Si phase has been studied in this investigation. Microstructural examinations were assessed by the use of optical microscope and scanning electron microscopy. The results revealed that hot extrusion breaks primary Mg2Si phase and changes its morphology from dendritic to regular shape. It was also found that hot extrusion reduces the size of primary particles as well as casting defects such as porosity. Further examination showed that hot extrusion has strong effect on breaking eutectic Mg2Si network. Remarkable result of this study was concerned with significant improvement in ductility by hot extrusion. Fractographic examinations revealed that hot extrusion encourages ductile mode of fracture by introducing homogenous and fine dimples on the fracture surface of the aluminum matrix composites.