Reinforcement coatings and interfaces in aluminium metal matrix composites

The interface between the matrix and reinforcement plays a crucial role in determining the properties of metal matrix composites (MMC). Surface treatm ents and coating of the reinforcement are some of the important techniques by which the interfacial properties can be improved. This review reports th e state of art knowledge available on the surface treatments and coating wo rk carried out on reinforcements such as carbon/graphite, silicon carbide ( SiC) and alumina (Al2O3) and their effects on the interface, structure and properties of aluminium alloy matrix composites. The metallic coatings improved the wettability of reinforcement but at the same time changed the matrix alloy composition by alloying with the matrix. Ceramic coatings reduce the interfacial reaction by acting as a diffusion barrier between the reinforcement and the matrix. Multilayer coatings have multifunctions, such as wetting agent, diffusion barrier and releaser of th ermal residual stress. The roles of reinforcement coating as a means of "in situ hybridising" and "in situ alloying" are described. (C) 1998 Kluwer Ac ademic Publishers.