An analytical model for complete solute trapping during rapid solidification of binary alloys

An analytical model has been developed to describe solute partitioning during rapid solidification of binary alloys under local nonequilibrium conditions. The model takes into account the deviations from equilibrium both at the solid–liquid interface according to the kinetic approach of Jackson et al. based on Monte Carlo simulations and in the bulk liquid using local nonequilibrium diffusion model (LNDM). The dimensionless growth parameter β found in the Monte Carlo simulations as the important parameter for solute trapping has been modified for the local nonequilibrium diffusion case. An analytical expression has been developed for the velocity-dependent partition coefficient KLNDM(V) which predicts complete solute trapping and an abrupt transition from diffusion-controlled to diffusionless solidification when the interface velocity V passes through the critical point V=VD. The predictions are in good agreement with the experimental results, molecular dynamic studies, and Monte Carlo computer simulations.

► We model solute trapping in alloys under local nonequilibrium conditions.
► We introduce a new trapping probability parameter.
► Complete solute trapping occurs at a finite interface velocity.
► Critical parameter for solute trapping is the bulk liquid diffusion speed.