Effect of thermodynamic interactions on the rapid solidification kinetics of Ni-Cu-Co alloys

Most theoretical work on solidification focuses on dilute binary alloys, while those commonly used in industry are multi-component with high solute concentrations. In concentrated alloys, the diffusion of one component will be inevitably influenced by the others, which will further affect the rapid solidification kinetics. Assuming local non-equilibrium at the solid/liquid (S/L) interface and in the bulk liquid, the kinetics of planar interface migration and dendrite growth in strongly non-equilibrium solidification of Ni-Cu-Co alloys is comparatively studied. It is found that, for planar interface kinetics, the thermodynamic interactions lead to a non-monotonic tendency of the partition coefficient of Co with a slightly lowered interface temperature. Meanwhile, for dendrite growth (i.e. curved interface), the curvature effect and the thermodynamic interactions together result in the non-monotonic variation of partition coefficients. Due to the lowered dendrite tip temperature as a result of the thermodynamic interactions, larger undercooling is needed for interface migration and the dendrite growth is slowed down.