The dislocation core structures in stoichiometric and non-stoichiometric material were studied by using atomistic computer simulations and embedded-atom potentials to model the configurations in the vicinity of dislocation cores. The results were analyzed in terms of the stress tensor, as a function of position, and gave the detailed shape of the dislocation core. A non-stoichiometric Ni-rich alloy was generated by means of the random replacement of Al atoms by Ni atoms in a perfect lattice. The results showed that a 2% deviation from stoichiometry affected the shapes of the dislocation cores; in that they tended to lose their preference for the well-defined crystallographic planes that were seen in the stoichiometric alloy. Deviations from stoichiometry also increased non-planar spreading of the core. This increased non-planar spreading in Ni-rich material was in agreement with high-resolution electron microscopic results. It was also found that Al vacancies were strongly attracted to the core and produced even more marked changes in the core structure. The Peierls stress was found to increase significantly in non-stoichiometric alloys. The interaction of antisites with the dislocation core was not so strong, but the Peierls stress still increased.

K.Ternes, Z.Y.Xie, D.Farkas: Materials Science and Engineering A, 1995, 192-193, 125-33