Electronic mechanism of impurity-dislocation interactions in intermetallics: NiAl

The nature of impurity-dislocation interactions is one of the key questions governing the strength and plasticity of solid-solution materials. To inve stigate the influence of impurities on the mechanical properties of interme tallic NiAl, the electronic structure and energy of NiAl with a < 100 > {01 0} edge dislocation and transition-metal impurities was calculated using th e real-space tight-binding Linear muffin-tin orbital method. The localized electronic states, appearing in the core of the dislocation, are found to l ead to strong impurity-dislocation interactions via two mechanisms: firstly : chemical locking, due to strong hybridization between impurity electronic states and dislocation Localized states; secondly, electrostatic locking, due to long-range charge oscillations caused by the electron localization i n the dislocation core. The results obtained explain qualitatively why the solid-solution hardening effect in NiAl correlates with the electronic stru cture of impurities rather than with size misfit, as expected according to traditional views.