Reconciliation between simulated and measured microstructures of metastable FeCr alloys: A phase field approach

Abstract

This work presents a novel phase field method for modeling the microstructure induced by the thermal decomposition of immiscible metastable binary alloys. This approach bypasses the problem associated with the modeling of the nucleation process introducing a random distribution of critical precipitates as an initial condition for the Cahn–Hilliard equation, extensively used to model the microstructure in the spinodal regime. The comparison between simulated and measured microstructures obtained from atom probe tomography measurements performed on ultra pure Fe0.81Cr0.19 samples justifies the validity of our method. In particular, we succeeded modeling the evolution of the chemical composition of α′ clusters produced during annealing. Such an evolution has been many times reported from atom probe tomography measurements but never explained. Moreover, these simulations allowed proposing a physical mechanism to explain the increase of the yield strength, observed in many annealed FeCr samples.