Effects of reinforcement oxidation on the mechanical properties of SiC particulate reinforced aluminum composites

The microstructures and mechanical properties of artificially oxidized and as-received silicon carbide particle (SiCp) reinforced pure aluminum and 2024Al composites were investigated. It was shown that surface oxidation of SiCp increased the tensile strength and fracture strain of the pure Al based composite. Diffusion of aluminum into SiO2 during fabrication of the composite, which increased the diffusion bonding between the SiC particle and the aluminum matrix, is thought to be responsible for the increases in strength and ductility. However, the strength and ductility of the oxidized SiCp reinforced 2024Al composite were much lower than those of the as-received SiCp reinforced 2024Al composite. Based on the experimental results from DSC, TEM, EDX and SEM fractography analyses, it is suggested that the interfacial reactions related to SiO2 depleted the magnesium in the matrix and subsequently decreased the amount of the age strengthening phase containing magnesium. The lower level of strengthening in the matrix and the formation of a thick interfacial reaction layer, which was continuous and brittle, finally led to the lower strength and ductility of the artificially oxidized SiCp reinforced composite.