Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites

Isotropic composites of aluminum alloy matrices reinforced with particulate alumina have been developed as lightweight, high-specific-strength, less expensive alternatives to nickel-base and ferrous superalloys. These composites feature a specific gravity of about 3.45 g/cm3 and specific strengths of about 200 MPa/(g/cm3). The room-temperature tensile strength is 100 ksi (689 MPa) and stiffness is 30 Msi (206 GPa). At 500 °F (260 °C), these composites have shown 80 percent retention in strength and 95 percent retention in stiffness. These materials also have excellent fatigue tolerance and tribological properties. They can be fabricated in net (or nearly net) sizes and shapes to make housings, pistons, valves, and ducts in turbo-machinery, and to make structural components of such diverse systems as diesel engines, automotive brake systems, and power-generation, mining, and oil-drilling equipment. Separately,incorporation of these metal matrix composites within aluminum gravity castings for localized reinforcement has been demonstrated.