On the processing of in-situ metal-matrix-composites

During in-situ processing of metal matrix composites a fine: dispersion of small crystals elf carbides, nitrides or borides are formed by an exothermic reaction in liquid metals. The reaction can be achieved by mixing a liquid metal containing carbide or boride stabilising elements with a liquid, a solid or a gas containing carbon nitrogen or boron. The reaction is controlled by nucleation and growth of a large number of crystals. The precipitation processes are related to the stability of the precipitated crystals. This is analysed using well-known thermodynamic models. Experimental results together with the theories of nucleation and growth are used to discuss and out line the most important parameters necessary to achieve a fine dispersion of small crystals.