Atomistic simulations of the bulk effects of Mg on the cohesion of the Ni3Al–x at.% Mg grain boundary

Monte Carlo simulation with the energetics described by the embedded atom method (EAM) has been employed to calculate not only grain boundary concentration profiles of Ni, Mg and Al, but also dependence of the grain boundary cohesion on the Mg bulk concentration, for the Ni3Al-x at.% Mg (100%Ni\100%Ni)[001]/Sigma5(210)/36.87degrees grain boundary, at equilibrium. We suggest that the bulk effects of Mg on the grain boundary include the primarily positive effect on the Ni enrichment at the grain boundary, i.e. the Mg atoms induce Ni atoms to substitute into Al sites, the secondarily positive effect on it, i.e. the Mg atoms substitute into Al sites, and the negative effect on it, i.e. the Mg atoms substitute into Ni sites. For the Ni3Al-x at.% Mg grain boundary, at the equilibrium, the calculations show that when x (the Mg bulk concentration) increases from 0.1 to 0.5, the Mg enrichment increases, both the Ni enrichment and the Al depletion maximizes at x = 0.2. The calculations also show the best cohesion of the grain boundary at x = 0.2. (C) 2003 Elsevier B.V. All rights reserved.