Solidification of particle-reinforced metal-matrix composites

The solidification process largely determines the particle distribution and microstructure of metal-matrix composites (MMCs) which, in turn, influence many of the material properties. The solidification behavior of MMCs was investigated experimentally by unidirectionally solidifying in a pre-heated cylindrical steel mould 15 μm silicon carbide particle-reinforced aluminum A356 alloy, prepared by a melt stirring technique. Temperatures were measured at different depths, from which the cooling curves were constructed. Experiments were conducted over a range of particle volume fractions, 0 to 0.15. Comparison of the cooling curves for the MMCs with the unreinforced alloy reveals a slight depression of the liquids and solids temperatures, and a higher solidification rate in the presence of the particles. Preliminary results of a one-dimensional enthalpy model of MMC solidification are also presented and discussed in relationship to the experimental observations.