Grain boundary structure and grain boundary segregation in stoichiometric and Ni-rich compositions of NiAl were studied by molecular statics and grand-canonical Monte-Carlo simulations in conjunction with an embedded-atom potential. Significant Ni segregation was found at the Σ = 3 (111) and Σ = 3 (211) grain boundaries, with segregation isotherms showing a saturation effect. The amount of Ni segregation increased and the excess free energy of the grain boundaries decreased with increased Ni bulk concentration. In strongly Ni-rich bulk compositions, both boundaries undergo transformations to new structures capable of accommodating more excess Ni atoms than the initial structures. The structural transformation was clearly manifested by a non-monotonic behavior of the segregation isotherm. In the Σ = 3 (211) grain boundary, the transformation was accompanied by a relative tangential translation of the grains.

Segregation and Structural Transformations at Σ = 3 Grain Boundaries in NiAl - a Monte-Carlo Study. J.A.Brown, Y.Mishin: Acta Materialia, 2005, 53[7], 2149-56