Ductility and strength of extruded SiCp/aluminium-alloy composites

The effect of hot extrusion on the strength and ductility of particulate silicon-carbide-reinforced aluminium alloy (Al-5% Si-0.2% Mg) composites has been studied. Cast ingots of the matrix alloy and the composites were extruded at 500 deg C at an extrusion ratio of 10:1. The microstructures and mechanical properties of the composite samples and the matrix alloy have been investigated in the as-cast state and after extrusion, and are compared with the mechanical properties of hot-forged composites of the same composition. The extruded microstructures have a more uniform distribution of the SiC particles and the eutectic silicon by comparison with as-cast microstructures. Evaluation of the mechanical properties show that the extruded samples have strength and ductility values superior to those of the as-cast counterparts. In the extruded samples the addition of increasing amounts of particulate SiC increases the yield and tensile strength and decreases the ductility. The ductility level of the extruded samples is found to be higher than those of the forged and as cast samples. (Materials noted: AlSi5, Silicon carbide.)