Modeling of solidification of metal-matrix particulate composites with convection

Abstract

A multiphase model for the alloy solidification of metal-matrix particulate composites with convection is developed. Macroscopic transport equations are written for each phase, with unknown parameters modeled through supplementary relations pertinent to the solidification of a binary alloy matrix containing a stationary solid phase and generally nonstationary spherical particles. The model is applied to various one- and two-dimensional systems containing an Al-7 wt pct Si/SiC composite. One-dimensional sedimentation results in nonclustering and clustering particle systems show good agreement with experiments. One-dimensional composite solidification results illustrate the effect of particle clustering and cooling direction on the final macroscopic particle distribution. Two-dimensional results in various unreinforced and reinforced systems illustrate macroscopic particle segregation and its effect on buoyancy-driven melt convection and species macrosegregation. Results indicate a nearly uniform particle distribution for relatively small particles due to negligible particle settling prior to entrapment. For relatively large particles, significant particle settling prior to entrapment results in large denuded and packed zones in the casting. Fluid flow and macrosegregation during solidification are substantially reduced in the presence of particles, due to the relatively large interfacial drag exerted on the liquid by the stationary mush and particle phases.