Modeling the overall solidification kinetics for undercooled single-phase solid-solution alloys. II. Model application

An overall solidification kinetic model was applied to undercooled Ni-15 at.% Cu alloy. A good agreement between the model predictions and the measured cooling curves was obtained by adopting a "phenomenological" heat boundary condition. Applying numerical calculations, it was demonstrated that solute is uniformly distributed at the purely thermal-controlled growth stage; a transition from non-equilibrium to near-equilibrium solidification occurs at the mainly thermal-controlled growth stage only if sufficiently high initial undercooling is available; and a transition from recalescence to post-recalescence occurs at the solutal-controlled growth stage wherein the current model reduces to Scheil's equation. The volume fraction solidified during recalescence is the same as the ratio of the initial undercooling to the hypercooling limit, and solidification should end generally at a temperature between the prediction of Scheil's equation and that of the Lever rule if back diffusion is considered.