Atomistic-informed kinetic phase-field modeling of non-equilibrium crystal growth during rapid solidification

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A novel method based on molecular dynamics (MD) is developed to make the kinetic phase-field (PF) model quantitative in predicting non-equilibrium crystal growth during rapid solidification. MD-calculated variations of the diffuse solid-liquid (SL) interface width versus interface velocity are used to parameterize the kinetic PF model. Two approaches are adopted to study temperature independent and temperature dependent interfacial properties on the accuracy of predictions. MD simulations of slow and rapid solidification regimes for an fcc metal (Ni) show that the SL interface width decreases by increasing the solidification velocity. Fitting the dynamic response of the interface width to the traveling wave solution of hyperbolic PF equation determines the target SL interfacial properties, namely propagation velocity and diffusion coefficient. Independently, the MD calculations of nonlinearity in velocity versus undercooling is used to validate the atomistic-informed kinetic PF model. Both parabolic and kinetic PF models parameterized by temperature-independent material properties can accurately simulate the linear portion of near-equilibrium crystal growth during solidification. However, they both fail to predict the crystal growth kinetics during rapid solidification. The kinetic PF model parameterized with the temperature-dependent SL interfacial properties can accurately predict both the equilibrium and non-equilibrium crystal growth during slow and rapid solidification. MD simulation results on Ni along with some analytical analysis on the variation of interface width versus interface velocity show that for fcc metals, in general, {110} interface has a smaller propagation velocity in comparison to {100} interface, resulting in a larger non-linear behavior at smaller undercooling.