Models for the determination of kinetic phase diagrams and kinetic phase separation domains

Abstract

Several theoretical models for the determination of kinetic phase diagrams for solid solution growth from the liquid phase are presented and compared to each other. These models include a Monte Carlo simulation model, used as a reference model, a previously defined analytical model, based on linear non-equilibrium thermodynamics, and a new model, rooted in the kinetics at kink sites. All models have in common that the composition of the growing solid phase tends to the liquid phase composition for increasing undercooling, enhancing mixing even for systems with a strong tendency to phase separation. However, depending on the system parameters considerable quantitative differences can occur between the results from the model based on non-equilibrium thermodynamics and the MC model. Instead, the new model follows very well the trends of the MC simulations, both for well-mixing systems and for phase separating systems. For phase separating systems the analytical models predict kinetic phase separation domains, zones in the kinetic phase diagram yielding steady state growth of more than one solid phase with different compositions. According to MC simulations such domains in phase space correspond to domain formation in real space. Also in this case the new model is consistent with the MC results.