Irradiation dose-rate effect in Fe-C system: An Object Kinetic Monte Carlo simulation

Herein, the defect features under irradiation in the Fe-C system are studied by an Object Kinetic Monte Carlo (OKMC) model. The model was based on recent parameters and was validated by comparing the numerical estimates with the experimentally obtained defect features in neutron-irradiated iron. Systematic simulations of defects evolution at 70 °C in a wide range of dose rates from 10 ⁻⁸ to 10 ⁻⁴ dpa/s were carried out. The simulation results demonstrate that at the lower dose range (< 0.02 dpa), a higher dose rate irradiation leads to a higher interstitial-loop density and irradiation hardening. In contrast, the dose rate does not obviously influence the defect features at the high dose range. Defect features under two carbon concentrations 50 and 100 appm show a similar dose-rate effect, and a higher carbon concentration leads to a higher interstitial loop density and irradiation hardening. We attribute the dose rate effect change with dose to the competition between sinks absorption and SIAs-vacancies annihilation. Based on the interaction model of <100> production, the ratio of <100>-type interstitial loops is higher at the higher dose rate irradiation, consistent with the experimental results.