The effect of Cr concentration on radiation damage in Fe-Cr alloys

Displacement cascades in Fe-Cr alloys were studied using molecular dynamics computer simulations. We considered random Fe-5Cr and Fe-15Cr alloys, as well as Fe-10Cr alloys with and without Cr-rich precipitates. In the simulations two versions of a two-band embedded atom method potential were used, and the cascades were induced by recoils with energies up to 20 keV. We found that the average number of surviving Frenkel pairs and the fraction of vacancies and self-interstitials in clusters was approximately the same in pure Fe and random Fe-Cr alloys (regardless of Cr concentration). A noticeable effect of the presence of Cr in the Fe matrix was only observed in the enrichment of self-interstitials by Cr in Fe-5Cr. The calculated change in the short range order parameter showed that Fe-5Cr tends towards ordering (negative short range order parameter) and Fe-15Cr towards segregation (positive short range order parameter) of Cr atoms. In simulations with the Cr-rich precipitate, enhanced cascade splitting and segregation of self-interstitial defects created inside the precipitates towards the precipitate-matrix interface region was observed. The number of Frenkel pairs and their clustered fraction was not affected by the presence of the precipitate.