Trapping of impurity in a dilute solution: phase-field simulation of solidification

The process of impurity redistribution in the vicinity of diffuse interface between the liquid and solid phases has been investigated by numerical simulation of nonstationary process of directional solidification of a dilute solution with a flat front using a locally nonequilibrium model of the phase field. As a result of calculations, the average impurity concentration profiles near the interface have been received. From these profiles, the concentration distributions in solid and liquid phases for different front velocities are determined using the phase field. The plotted dependences of distribution coefficient on the velocity are compared with data obtained using the hyperbolic model of continuous growth and with results of earlier calculations in the quasi-stationary approximation. We have analyzed the effect of model parameters on the form of the dependence of distribution coefficients on the front velocity and on the concentration distribution profile in the diffuse interface.