Casting Routes for Production of Metallic Based Composite Parts

Casting is a preferred route to produce metal matrix composites (MMCs) because of its perceived simplicity, low cost and applicability for mass production. The process typically involves melting of the metallic matrix by utilizing a furnace, incorporating the reinforcements and allowing the composite melt to solidify. The physical and chemical properties of the reinforcement particles may have a significant influence on the process and the nature and extent of its dispersion in the metallic matrix. A high wettability between the reinforcement particle and the molten metal is preferred for successful incorporation. The current chapter presents an overview of various casting routes used to produce MMCs. These include stir casting, slurry casting, centrifugal casting, and squeeze casting. Stir casting typically involves molten metal being stirred by a mechanical stirrer to produce a mixing vortex that then introduces particles into the matrix. During slurry casting the metallic matrix is heated to a semi solid state in the freezing range thereby improving the wettability of the reinforcement particles. Centrifugal casting utilizes a centrifugal force to disperse the composite melt into a tubular form to produce functionally graded composite tubes. Squeeze casting involves an application of a significant force to infiltrate the molten metal into preforms thereby reducing wettability issues and volume fraction limitations that may be inherent in other casting methods. The resultant microstructure and mechanical properties of each of these methods are presented and discussed. The associated advantages and disadvantages of each process are also discussed.