Modeling of non-equilibrium solute diffusion upon rapid solidification: Effective mobility versus kinetic energy

The effective mobility approach is compared with the kinetic energy approach in terms of sharp interface modeling and phase-field modelling of non-equilibrium solute diffusion upon rapid solidification ofbinary alloys. The two approaches are equivalent formodelling of long range solutediffusion in bulk phases, but only the effectivemobility approach can introduce the non-equilibrium solute diffusion effect to short range solute diffusion at a sharp interface or within a diffuse interface. Addition of the kinetic energy terms results in an unreasonable non-bilinear expression of the flux and thermodynamic driving force in the free energy production of interface migration or phase field propagation, whereas the effective mobility approach allows the thermodynamic extremal principle workable.