Phase-field model of equilibrium and radiation induced segregation at grain boundaries: Formalism and application to Fe Cr alloys

We propose a novel phase-field (PF) model to enhance the description of grain boundaries (GBs) and its effect on the solute segregation behaviour under irradiation. Conventional PF models typically treat GBs as perfect sinks for point defects (PDs) such as vacancies and interstitials, often assuming the system’s chemical potentials as homogeneous. Our approach employs a density function to represent the reduction in atomic density within GBs. Furthermore, we introduce a mixing term to account for ballistic damage, simulating the effects of PD generated by displacement cascades. This study demonstrates how our model featuring the density function correctly predicts equilibrium segregation and its impact on radiation-induced segregation (RIS) in alloys, a material widely used in the nuclear industry. Our methodology successfully reproduces the well-known “W-shape” segregation profiles, and provides insights into spinodal decomposition and ballistic mixing effects on GB segregation. This advanced PF model offers a better understanding of GBs behaviour under irradiation, potentially contributing to improved material design for nuclear applications.