Numerical Simulation of Microstructure of Al-Si/SiCp Composites during Stir Casting Process with Particle Pushing Model

Abstract

Particle distribution has vital influence on the microstructure and the final performance of particle reinforced metal matrix composite. The formation of microstructure of SiC particle reinforced Al–7.0mass%Si composite made by stir casting was simulated in this paper. Two-dimensional models under normal solidification condition including macro heat transfer, micro nucleation, equiaxed dendrite growth and particle pushing were presented. Two sets of meshes were used to carry out macro and micro calculation, respectively. A modified cellular automaton method coupled with finite difference method was used to simulate the evolution of the composite microstructure. In addition, the effects of SiC particle volume fraction, different casting processes, pouring temperature and cooling rate on the composite microstructure and the particles distribution were analyzed. The simulated results can clearly show the particle clustering/accumulation phenomenon caused by particle pushing. The calculated cooling curve and final predicted microstructure are in good agreement with the experimental results. Grain size is smaller for metal mould casting than sand mould casting. With the increase of SiC particle volume fraction or cooling rate, the grains of the matrix alloy are refined and particles are distributed more uniformly. As the pouring temperature increases, particles are distributed more uniformly.