Simulation of solidification structures of binary alloys: a multi-particle diffusion-limited aggregation model with surface rearrangement

The thermodynamics and kin-ties of isothermal solidification in binary-alloy melts were simulated in a two-dimensional model incorporating the effects of nearest and next-nearest neighbours at the solid-liquid interfaces, taking into account the simultaneous diffusion in the melt of all mobile particles (atoms) and allowing rearrangement at the solid-liquid interface on a local scale. The next-nearest-neighbour interaction and the surface rearrangement were shown to have large effects on the resulting solidification morphologies. Additionally, the influences of the operating diffusion coefficient and the sticking rule for the solidifying particle were analysed. A wide range of growth modes, dendritic, massive, equiaxed, eutectic, and transitions thereof during solidification, involving change of time dependence of the growth velocity, as observed in practice, could be placed on a rationalistic basis.