Calculation of grain-boundary segregation in Ni-Cu alloys

The equilibrium segregation at symmetric twist grain boundaries in Ni-Cu alloys is computed with use of Monte Carlo simulations combined with the Daw-Baskes embedded-atom method. These simulations include both compositional rearrangements and atomic displacements. The boundaries studied are the {Σ}5, {Σ}13, and {Σ}61 [001] symmetric twist boundaries. It is found that Cu segregates to the boundary and that the change in composition is confined to a few atomic layers near the boundary. The degree of segregation was found to be greater for Ni-rich alloys and for large-angle boundaries. The variation of the concentration within the planes parallel to the boundary for a low-angle twist boundary is studied and the variations correlated with the positions of the boundary dislocations.