Mechanical and elastic changes in cementite Fe3C subjected to cumulative 1 keV Fe recoils

Carbon-bearing steels have a complex microstructure which involves cementite Fe3C. When these steels are used as construction materials for nuclear reactors they are subjected to continuous defect production due to neutron irradiation. Its effects on iron containing interstitial carbon have been studied previously. However, the evolution of Fe3C when subjected to these conditions is unknown, at any temperature, dose and dose rate. In this work we present results from molecular dynamics simulations of cumulative defect production in a pure single-crystal Fe3C sample subjected to a high dose-rate of 1 keV Fe recoils. The results indicate that Fe3C after an initial softening grows slightly harder after a dose of 0.1 dpa, and remains at this level for doses up to 0.7 dpa. Analysis indicates this effect may be due to C atoms getting closer to each other as the damage production increases. Results for the Young's moduli and the defect production are also presented. Due to the high dose-rate the effects on actual nuclear steels is unclear, but some estimates are discussed. (C) 2014 Elsevier B.V. All rights reserved.