A temperature-dependent atomistic-informed phase-field model to study dendritic growth

Abstract

The effects of solid–liquid interface anisotropy and kinetics on crystallization of highly undercooled titanium melts are studied by coupling molecular dynamics and phase-field simulations. Unlike previous models and to consider the actual physics of crystal growth, the phase-field parameters, representing interface mobility, solid–liquid transformation barrier, and interfacial energy gradient, are temperature dependent. The parameters are determined by a combination of molecular dynamics simulations and classical thermodynamic calculations based on the temperature-dependent solid–liquid interface properties and kinetic coefficient. We investigated Ti dendritic growth as a benchmark example to demonstrate that the phase-field model presented in this work is more compatible with the experimental data and theoretical models in comparison to the earlier models with constant model parameters. The capillary fluctuation method is used to determine the solid–liquid interface energy and its anisotropy for undercoolings up to 400 K. Similar to theoretical models, the average solid–liquid interface energy decreases with temperature, and the preferred dendrite growth direction shifts from 〈100〉 to 〈110〉 direction as the undercooling increases. Phase-field simulations also show other favorite growth directions, implying that there is a competition between the interface anisotropy and kinetics of the solid–liquid interface.