Effect of Cr Concentration on ½ to Dislocation Loop Transformation in Fe-Cr alloys

Radiation can produce both and ½ type dislocation loops in Fe-Cr based ferritic/martensitic alloys. However, contradictory experimental results have been reported on how Cr concentration affects the ratio of to ½ loops. In this study, firstly molecular dynamics simulations are conducted to study how Cr concentration affects the formation probability of loops from overlapping cascades on a pre-existing ½ loop in a series of Fe-Cr alloys with 0 – 15%Cr at 300 K using a concentration-dependent interatomic potential. Our atomistic modeling directly demonstrates that the ratio of to ½ loops decreases with the increasing Cr concentration, which is consistent with many experimental observations. Next, independent molecular statics calculations show that the formation energy of a loop has a much faster increase rate than that of a ½ loop as Cr concentration increases, indicating that the formation of loops becomes energetically more and more unfavorable than ½ loops as the Cr content increases. Using a different interatomic potential, the Cr dependence on the loop formation probability is weak, because this potential predicts that Cr addition does not change the relative energy difference between and ½ loops. Our results provide an alternative explanation for why Cr can suppress the formation of loops in Fe-Cr alloys, which can be applied to all loop formation mechanisms. The possible effects of other alloying elements on the formation of loops in Fe-based alloys are also discussed. [Display omitted]