Computer simulation of grain boundaries in Ni 3Al: The effect of grain boundary composition

Abstract

The authors have performed atomistic simulations on three (001) symmetric tilt grain boundaries: 5(210), (310), and 13(320). Depending on which sub-lattice in each of the two grains is occupied by Al, the grain boundary may have different stoichiometries. All of the simulations show that the Al-rich grain boundaries have the highest grain boundary energies. Thus Al-rich grain boundaries are more likely to fail than those which have the bulk stoichiometry or are Ni-rich. This conclusion is consistent with the observed stoichiometry dependence of the beneficial boron effect. The similarity between the grain boundary energies (cohesive energies) of Ni/sub 3/Al and Ni and the much higher yield stress of Ni/sub 3/Al provides a justification for the ''inherent'' brittleness of Ni/sub 3/Al grain boundaries.