Processing Metal Matrix Composites

By the definition adopted here (Section 1.1), all metal matrix composites are produced by artificially combining reinforcements with a metallic phase, “artificially” meaning that the two phases preexist the material before being combined. “Making a composite” is therefore the act of combining these two preexisting phases, matrix and reinforcement, into a new material, the composite (as illustrated in Figure 1.1). This we call “primary processing” of the composite. It is distinct from “secondary processing” where the composite is deformed, shaped, hardened, machined, coated, or joined (with itself or with another material) after it is created. Preliminary processing steps may also exist upstream of primary processing; these we call “pre-processing”. This of course includes making the reinforcement and the matrix, but may also comprise steps such as arranging these in various configurations. Examples include packing short fibres held together with a silica binder into a preform for subsequent infiltration, or creating powdered matrix cloth using an organic binder before solid-state consolidation with monofilaments.