Computer simulation of the interaction between an edge dislocation and interstitial clusters in Fe and Ni

Abstract

Atomic structures of interstitial type dislocation loops and the interaction between these loops and an edge dislocation have been investigated for Fe and Ni by means of computer simulation in order to understand the basic feature of the damage structure evolution during irradiation which provides cascade formation of defects. Clusters of crowdions or dumbbells were placed in the model lattices and final structures were observed after full relaxation. It is found that in the case of clusters of crowdions, relaxation of the structure, namely, split of strain concentration for each crowdion in the cluster occurs with increasing the number of crowdions in one cluster, i.e., beyond about ten, and this split structure indicates the transition to dislocation loops, because a straight edge dislocation has the same split nature both in Fe and Ni. In the study of the interaction between an initial cluster and an edge dislocation it is found that a stacking fault of an extended edge dislocation is heavily deformed by the presence of an interstitial cluster just below the slip plane. Finally the critical stress for the motion of an interstitial loop, that is, Peierls stress, for the dislocation loop was investigated and it is found that as the loop size increases, Peierls stress decreases and approaches the level for a straight edge dislocation.