PRESSURE INFILTRATION CASTING OF METAL MATRIX COMPOSITES

Pressure infiltration casting* is a unique form of liquid infiltration which utilizes pressurized inert gas to force liquid metal into a preform of reinforcement material. The methods and equipment used for pressure infiltration casting allow for inexpensive development of composite materials, prototypes, and net-shape component production. Pressure infiltration casting's use of an enclosed die chamber with controlled pressurization makes it possible to cast in low strength molds with high infiltration pressures. The development of a number of solidification systems has enabled parts to be infiltrated and directionally solidified, producing high quality composites. The basic principles behind pressure infiltration casting and its history will be discussed in this paper. Results of research in different methods for casting composites will also be presented. These methods include: (1) top fill casting-liquid metal is forced downward by a pressurized gas into a preform; (2) bottom fill casting-liquid metal is forced up a fill tube into a preform by pressurized gas acting on the surface of a melt; (3) top pour casting-a method developed for infiltration of high temperature alloys where the reinforcement and melt must be prevented from reacting. The methods and apparatus illustrated include sample components with aluminum and copper matrices, their microstructures, and tolerancing for net shape component production.