Cast-alumina metal matrix composites

This composite consists of an aluminum-alloy matrix containing by volume percent, 0.4 to 8.8 alumina, 1 to 4.4 carbon or graphite and 0.5 to 20 nickel-bearing aluminide. The alumina particles have an average size between 3 and 250 mum and the carbon and graphite particles have an average size between 10 and 250 mum. The composite is cast by stirring alumina and carbon or graphite contained in a molten aluminum or aluminum-base alloy to form a molten mixture. The molten mixture is cast directly from a temperature above the liquidus of the matrix alloy. While solidifying, carbon or graphite particles delay or hinder the settling of alumina to create a more uniform composite structure. The resulting composite structure contains an aluminum-base alloy, alumina, carbon or graphite and nickel-bearing aluminide dispersoids.