Atomistic segregation analysis in an asymmetrical grain boundary for Ni(Ag)

Abstract

Intergranular segregation is studied for the first time in an asymmetrical grain boundary at the atomistic level. The grain boundary (GB) is the asymmetrical tilt (331)//(11-1) <110> experimentally observed by high resolution transmission electron microscopy (HRTEM) in nickel bicrystal. The metallic alloy chosen for the study is nickel(silver) in the limit of infinity diluted solution. The interactions are modelled with n-body, Finnis-Sinclair like, potentials. The atomic sites are characterized by their exact Voronoï volumes and by the stress density tensors locally exerted. In these respects, the asymmetrical near Σ=11 (331)//(11-1) GB presents a larger diversity of sites than the symmetrical GBs previously studied. The segregation energies are computed and analyzed versus the two ‘driving forces’, the elastic size effect and the excess cohesion energy effect, which play a role in metallic intergranular segregation in the one atom segregation limit. The elastic size effect calculated by the method of virtual impurity represents the main segregation driving force in most cases of the considered bimetallic alloy. This generalizes to an asymmetrical GB results previously obtained on symmetrical GBs.