Multi-scale modeling of the effects of temperature, radiation flux and sink strength on point-defect and solute redistribution in dilute Fe-based alloys

TL;DR

This paper develops an analytical model to understand how temperature, radiation flux, and sink strength influence point-defect and solute redistribution in dilute Fe-based alloys under radiation, revealing different kinetic regimes and the impact of forced atomic relocations.

Contribution

The work introduces a new analytical model that captures the coupled effects of defect migration, production, and sink interactions on radiation-induced segregation in Fe alloys.

Findings

Diffusion and RIS behaviors vary significantly across kinetic domains.

Forced atomic relocations can suppress RIS profiles at high flux and sink strength.

Quantitative criteria are provided to simulate reactor RIS effects via ion irradiation.

Abstract

In this work, we investigate the radiation-induced segregation (RIS) resulting from the coupling between the atomic and point defect (PD) fluxes towards the structural defects of the microstructure. This flux coupling depends on the migration mechanisms of PDs and atoms, including thermal diffusion mechanisms and forced atomic relocations (FAR) occurring in displacement cascades. We derive an analytic model of the PD and solute RIS profiles accounting for PD production and mutual recombination, the FAR mechanism, and the overall sink strength of the microstructure controlling the elimination of PDs at structural defects. From this model, we present a parametric investigation of diffusion and RIS properties in dilute Fe-$B$ ($B$ = P, Mn, Cr, Si, Ni, and Cu) binary alloys, in the form of quantitative temperature/radiation flux/sink strength maps. As in previous works, we distinguish three kinetic domains for the diffusion and RIS properties: the recombination domain, the sink domain, and the thermal domain. Both our analytical approach and numerical applications demonstrate that the diffusion and RIS behaviors of PDs and solute atoms largely differ from one kinetic domain to another. Moreover, at high radiation flux, low temperature, and large sink strength, FARs tend to destroy the solute RIS profiles and therefore reduce the overall amount of RIS by forcing the mixing of solute and host atoms, especially close to PD sinks. Finally, we provide quantitative criteria to emulate in-reactor RIS behaviors by ion irradiation.