Diffuse solid-liquid interfaces and solute trapping

A phenomenological model is presented for partitioning of solute atoms across solid-liquid interface during solidification. The model treats the interface as being "diffuse", for which the transition from one phase to another takes place gradually when time-averaged over the entire layer of atoms parallel to the interface. For such an interface, the chemical potential of species also changes continuously from those in the liquid side of the interface to those in the solid. Moreover, the solute redistribution coefficient during solidification will depend on the diffuseness of the interface, which in turn is related to the interfacial peclet number. The latter is related to the interface velocity, its thickness and the overall migration rate of species across the interface. The influence of solidification rate on the solute trapping will be discussed and compared to other solute trapping models.