| Abstract: |
Metal matrix composites (MMCs) are engineered combinations of two or morematerials (one of which is a metal) in which tailored properties are achieved by systematic combinations of different constituents. Conventional monolithic materials have limitations in terms of achievable combinations of strength, stiffness, coefficient of expansion, and density. Engineering MMCs consisting of continuous, discontinuous particles in a metal result in combinations of very high specific strength and specificmodulus [1] .Furthermore, systematic design and synthesis procedures can be developed toachieve unique combinations of engineering properties, such as high elevatedtemperature strengths, fatigue strength, wear resistance, damping properties, electricalconductivity, thermal conductivity, and coefficient of thermal expansion. In broadersense,several cast materials with two- phase microstructure in which the volume and shape ofthe phases are governed by phase diagrams have long been produced in foundries.Modem cast MMCs differ from these older materials in that any selected volume, shape, and size ofreinforcement can be introduced into the matrix Table (1.1). These tailored cast metal matrix materials represent a new product opportunity for foundrymen.A variety of methods for producing MMCs, including casting techniques, haverecently become available. The potential advantage of preparing composite materials by casting techniques is the achievement of near-net shape fabrication in a simple andcost- effective manner. In addition, casting processes are suitable for the manufacturing of large numbers of components with complex shape at high production rates. This isrequired by automotive and other consumer- oriented industries.Structurally, cast metal matrix composites (CMMC) consist of dispersions of continuous or discontinuous fibers, whiskers or particles in an alloy matrix which solidifies in restricted spaces between the reinforcing phase to form the bulk of the matrix [2].
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