Atomistic simulation of the effect of carbon content and carbon-rich region on irradiation response of α-Fe on picosecond timescale

Abstract

α-Fe with low carbon content is a base material which is commonly used in manufacturing of Reactor Pressure Vessel (RPV) of commercial nuclear power plants. Carbon is generally diffused to α-Fe matrix to improve some of its mechanical properties. The presence of carbon may alter the irradiation response of the steel. In the current study, using molecular dynamics simulations, we have investigated the influence of carbon (∼in either dispersed form or carbon-rich region as chain) in the primary damage states of α-Fe low carbon steels. It is found that carbons in dispersed form have no significant effect on the self-interstitial atoms (SIAs) in α-Fe. While, carbon-rich (C-rich as pseudo-precipitation) region clearly increased the number of SIAs in bulk. A simple power formula was proposed to estimate the number of defects as a function of primary knock-on atom (PKA) energy and the number of atoms in the C-rich region.Cluster analyses of the defects formed in α-Fe containing 0–0.1 at.% dispersed carbon and with a C-rich region (with carbon chain of 0–100 atoms positioned in octahedral positions) showed that the presence of carbon in dispersed form had no effect on the average number of defect clusters (both the SIAs and the vacancies) in α-Fe containing 0–0.1 at.%. On the other hand, the average number of defect clusters for the α-Fe containing C-rich region apparently increases with increasing the number of carbon atoms in carbon chain. In addition, the average number of the interstitial clusters was significantly higher than that of the vacancy clusters.