The nanostructure evolution in Fe-C systems under irradiation at 560 K

TL;DR

This study extends a kinetic Monte Carlo model to simulate nanostructure evolution in Fe-C alloys at reactor-operational temperatures, capturing defect dynamics and the influence of carbon at higher irradiation temperatures.

Contribution

The paper introduces an adapted model that accounts for two types of SIA clusters and validates it against experimental data at 560 K, enhancing understanding of irradiation effects in Fe-C alloys.

Findings

Model reproduces experimental nanostructure trends

Carbon forms immobile vacancy complexes acting as SIA traps

Different SIA cluster types are observed and modeled

Abstract

This work extends our Object Kinetic Monte Carlo model for neutron irradiation-induced nanostructure evolution in Fe-C alloys to consider higher irradiation temperatures. The previous study concentrated on irradiation temperatures < 370 K. Here we study the evolution of vacancy and self-interstitial atom (SIA) cluster populations at the operational temperature of light water reactors, by simulating specific reference irradiation experiments. Following our previous study, the effect of carbon on radiation defect evolution can be described in terms of formation of immobile complexes with vacancies, that in turn act as traps for SIA clusters. This dynamics is simulated using generic traps for SIA and vacancy clusters. The traps have a binding energy that depends on the size and type of the clusters and is also chosen on the basis of previously performed atomistic studies. The model had to be adapted to account for the existence of two kinds of SIA clusters, <111> and <100>, as observed in electron microscopy examinations of Fe alloys neutron irradiated at the temperatures of technological interest. The model, which is fully based on physical considerations and only uses a few parameters for calibration, is found to be capable of reproducing the experimental trends, thereby providing insight into the physical mechanisms of importance to determine the type of nanostructural evolution undergone by the material during irradiation.