Atomistic Simulations of the Effect of Helium on the Dissociation of Screw Dislocations in Nickel**Supported by the Program of International S&T Cooperation under Grant No 2014DFG60230, the Strategically Leading Program of the Chinese Academy of Sciences under Grant No XDA02040100, the Shanghai Municipal Science and Technology Commission under Grant No 13ZR1448000, and the National Natural Science Foundation of China under

Abstract

The interactions of He with dissociated screw dislocations in face-centered-cubic (fcc) Ni are investigated by using molecular dynamics simulations based on an embedded-atom method model. The binding and formation energies of interstitial He in and near Shockley partial cores are calculated. The results show that interstitial He atoms at tetrahedral sites in the perfect fcc lattice and atoms occupying sites one plane above or below one of the two Shockley partial cores exhibit the strongest binding energy. The attractive or repulsive nature of the interaction between interstitial He and the screw dislocation depends on the relative position of He to these strong binding sites. In addition, the effect of He on the dissociation of screw dislocations are investigated. It is found that He atoms homogeneously distributed in the glide plane can reduce the stacking fault width.