Driving force for binary alloy solidification under far from local equilibrium conditions

Abstract

In this study we have incorporated the local nonequilibrium term into the Gibbs equation to obtain the local nonequilibrium correction to the driving force for solidification of binary alloys. The local nonequilibrium correction has been used to calculate the effective liquidus slope and the interface temperature for the model with and without solute drag effects. It has been demonstrated that both the local nonequilibrium correction and the solute drag play the most important role in the intermediate rage of the interface velocity V. When V increases up to VD, where VD is the characteristic diffusive velocity, a sharp transition to completely diffusionless and partitionless solidification occurs, which implies that the local nonequilibrium correction and the solute drag effects can be ignored. The transition is accompanied by a sharp change in the effective liquidus slope and the interface temperature as functions of interface velocity. The model was applied to describe initial transient and steady-state solidification of Si–As alloy and a good agreement between the model predictions and the available experimental data was obtained.