ENERGETICS OF PARTICLE TRANSFER FROM GAS TO LIQUID DURING SOLIDIFICATION PROCESSING OF COMPOSITES

The energetics for equilibrium transfer of solid particles in the shape of prolate spheroids across a stationary gas-liquid interface is computed as a function of the path of submersion. By considering the energy for submersion as comprising surface, buoyancy, and potential energies, equations have been derived for these energies in terms of particle size, degree of submersion, contact angles, surface tension, and densities of particle and liquid. The results for wetting particles show that certain intermediate configurations of partially submerged particles can be energetically stable even though this is not reflected in the calculations based only on initial and final configurations. The results of the analysis are discussed in the context of synthesis by stir casting of metal-matrix composites where the externally added particles or fibers must cross over in succession a gas-oxide interface, oxide-melt interface, and melt-solidification front interface.