Simulation of Solidification Structures Using a Multiparticle Diffusion Model

Abstract

A multiparticle diffusion limited aggregation type model is used to simulate diffusion during solidification in a binary alloy melt. Solidification from the liquid phase is calculated as an aggregation of mobile particles on a solidification front, assuming an anisotropic surface energy calculated by a Lattice Gas Hamiltonian with different interaction energies between nearest neighbours and next nearest neighbours. The microstructural length scales are shown to depend on an imposed surface relaxation length, defined as the maximum distance an adsorbed particle can migrate along the surface, thereby minimizing the surface energy. Our model allows simulation of both dendritic and eutectic growth structures. By using the assumption that liquid in the iterdendritic region reaches an eutectic composition one can also obtain a realistic simulation of hypo-eutectic microstructures.