Prediction of temperature-dependent nucleation and growth in pure FeCr alloy via a self-consistent Phase Field approach
Résumé
In a nucleation and growth process, the nucleation rate dictating the decomposition kinetics is generally modeled using the classical nucleation theory approach, which is only valid near the solubility limit where experiments are very difficult to perform. An alternative to this difficulty is to describe the exact dynamics associated with the decomposition from the metastable state to the stable state. This dynamics depends on the system under consideration and is complex to calculate. The approach presented in this work circumvents these two difficulties. The nucleation rate is calculated using only the knowledge of an effective Hamiltonian within a phase field approach. It then does not require the exact knowledge of the dynamics. The key point of this generic work is to show that only two time scales are sufficient to describe the complex interactions between the nucleation, growth, and coarsening processes. Comparing these scales makes it then possible to simulate microstructures by considering the nucleation process either as an initial condition or as a source term in the phase field equations. This approach is validated by the very good agreement between the simulated and measured 3D microstructures at different times on ultra-pure samples of FeCr, a textbook case of a nucleation-growth process.