Effects of Carbon Impurity on Microstructural Evolution in Irradiated α-Iron

Abstract

It is known that the presence of even a small amount of impurity in interstitial positions can, depending on temperature, have a drastic influence on the one-dimensional (1-D) motion of self-interstitial atom (SIA) loops, and thus, on the accumulation of radiation damage in materials. In this study, atomic-scale computer simulations based on a recently developed optimization technique have been performed to evaluate the binding energies of SIA loops with interstitial carbon, a vacancy-carbon (V-C) complex, and a vacancy as a function of loop size in α-iron. While weak and strong attractive interactions are found when an interstitial carbon atom and a vacancy, respectively, are located on the perimeter of an SIA loop, the interactions for both quickly weaken approaching the loop center. In contrast, for a wide range of loop sizes, significantly higher binding energies are obtained between an SIA loop and a V-C complex located within the habit plane of the loop. A cluster dynamics model was developed by taking into account the trapping effects of V-C complexes on 1-D migrating SIA loops, and preliminary calculations were performed to demonstrate the validity of the assumed trapping mechanism through a comparison of the microstructural evolution with experimental data in neutron-irradiated α-iron.