Fabrication and properties of powder metallurgical and cast aluminium alloy matrix composite products

The addition of ceramic particulates to aluminium alloys is an efficient way to improve some of their properties. However, attention should be paid to the formability of composites as it is often complicated to machine them. In the present work, the manufacture of particulate-reinforced aluminium alloys has been studied with reference to both powder metallurgical (PM) hot extrusion and casting methods including squeeze, gravity die, sand and pressure die-casting. The formability of hot-extruded composites has been investigated by tensile and upsetting testing. The properties of heat-treated composites are presented by tensile, fracture toughness and tribological properties. The results show that good-quality composites can be produced by both PM and casting methods. The forming of wrought composites is more difficult than that of unreinforced alloys and the application of compressive forces is to be preferred (e.g. closed-die forging) in forming operations. The addition of SiC particulates increased the stiffness, strength and wear resistance of both PM and cast composites. However, the ductility and fracture toughness were reduced.