The effects of deviations from stoichiometry upon the core structure and motion of dislocations in the B2 phase were studied. Vacancies and antisites were introduced into numerous positions in embedded atom simulation blocks which contained [100](001) as well as [100](011¯) pure edge dislocations. The interaction of these point defects with the dislocations was quantified by calculating the change in total energy which was experienced by the simulated lattice. An off-stoichiometric Ni-rich alloy was generated by randomly substituting Ni atoms for Al atoms, as well as by simply deleting Al atoms from the perfect lattice structure. It was found that a 2% deviation from stoichiometry affected the shapes of dislocation cores, in that they tended to lose their preference for the well-defined crystallographic planes that were seen in the case of the stoichiometric alloy. Deviations from stoichiometry also increased the non-planar spreading of the core, as visualized by using the strain-invariant method. It was found that Al vacancies were strongly attracted to the dislocation core, and produced much more significant changes in the core structure than did antisites or Ni vacancies. The Peierls stresses were found to increase significantly in off-stoichiometric alloys. The interaction of antisites with the dislocation core was not as strong, although the Peierls stress still increased. The simulations suggested that an entirely different core structure might be stable in off-stoichiometric alloys.

J.K.Ternes, D.Farkas, R.Kriz: Philosophical Magazine A, 1995, 72[6], 1671-96