Metal Matrix Composites MMCs

A metal matrix composite (MMC) is composite material with at least two constituent parts one being a metal necessarily the other material may be a different metal or another material such as a ceramic or organic compound. When at least three materials are present it is called a hybrid composite. An MMC is complementary to a cermet. MMCs are made by dispersing a reinforcing material into a metal matrix. The reinforcement surface can be coated to prevent a chemical reaction with the matrix. For example carbon fibers are commonly used in aluminium matrix to synthesize composites showing low density and high strength. However carbon reacts with aluminium to generate a brittle and water-soluble compound Al4C3 on the surface of the fibre. To prevent this reaction the carbon fibres are coated with nickel or titanium boride. The matrix is the monolithic material into which the reinforcement is embedded and is completely continuous. This means that there is a path through the matrix to any point in the material unlike two materials sandwiched together. In structural applications the matrix is usually a lighter metal such as aluminum magnesium or titanium. RTV .