Aluminum matrix composite solidification in microgravity: Effect of the reinforcing phase on nucleation

Abstract Among all the solidification processings available for metal matrix composite (MMC) fabrication, the gas pressure liquid infiltration method, recently developed, is very simple and fast. The molten aluminum can be infiltrated either in a preform made up of a three-dimensional array of fibers (SiC whiskers), or in a porous ceramic network. The resulting microstructures present rather low dislocation densities and, short solidification times can avoid interface phase formation. A series of samples with different orientations and volume fractions of the reinforcement, i.e. with different porosity, were examined in order to investigate the reinforcing phase and convection effects on the nucleation and growth of the solid nuclei in the constrained environment existing between the preform fibers.