ATOMISTIC MODELING OF STOICHIOMETRY EFFECTS ON DISLOCATION CORE STRUCTURE IN NIAL

Dislocation core structures in stoichiometric and non-stoichiometric N iAl have been analyzed. Atomistic computer simulation with embedded at om method potentials was used for the study of the configuration of th e material in the vicinity of dislocation cores. The results were anal yzed in terms of the stress tenser as a function of position, giving t he detailed shape of the dislocation core. A nonstoichiometric Ni-rich alloy was generated by random substitution of Al atoms by Ni atoms in the perfect lattice. structure. The results show that a 2% deviation from stoichiometry affects the shapes of the dislocation cores, in tha t they tend to lose their preference for the well-defined crystallogra phic planes seen in the stoichiometric alloy. Stoichiometry deviations also increase the non-planar spreading of the core. This increased no n-planar spreading of the core in Ni-rich NiAl is in agreement with th e experimental results of high resolution electron microscopy. In addi tion, it was found that Al vacancies are greatly attracted to the dist ribution core and produce more significant changes in the core structu re. The Peierls stresses were found to increase significantly for the non-stoichiometric alloys. The interaction of antisites with the dislo cation core is not as strong, although the Peierls stress is still fou nd to increase.