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The quest for higher efficiency and performance of automotive vehicles requires application of materials with high strength, stiffness and lower weight in their construction. Particulate-reinforced aluminum-matrix composites are cost-competitive materials, which can meet these requirements. MMCC, Inc. has been optimizing particulate-reinforced alloy systems and developing the Advanced Pressure Infiltration Casting (APIC™) process for the manufacture of components from these materials. This paper discusses the results of a recent study in which composites reinforced with 55 vol.% alumina were cast using two sizes of alumina particulate and eight different matrix alloys based on Al-4.5 wt.% Cu with varying amounts of silicon and magnesium. Optimum heat treatments for each alloy were determined utilizing microhardness studies. The tensile strength and fracture toughness were evaluated as a function of alloy chemistry, particulate size, and heat treatment.

Net-shape aluminum matrix composite components and test specimens were produced through an advanced pressure infiltration process where molten alloys are infiltrated into ceramic preforms. Test specimens were cast with 4 aluminum alloys with alumina and SiC reinforcements. Specimens were heat treated to T6 and T7 conditions and to a special condition wherein intermetallic particles are precipitated at internal interfaces. Alumina reinforced materials were generally stronger and tougher than silicon carbide reinforced materials. Maximum flexure strengths of 653 and 683 MPa were achieved through alumina reinforced 520 and 295 alloys, respectively. Fracture toughness and Charpy impact values were also determined.