THE MULTIPLICITY OF POSSIBLE GRAIN-BOUNDARY STRUCTURES IN NI3AL

The multiplicity of possible grain boundary structures was studied for the ordered compound Ni3Al. Two symmetrical tilt boundaries were chos en for the detailed study corresponding to Sigma=3[110]{112} and Sigma =9[110]{114}. These boundaries were investigated considering possible variations of the local chemical composition as well as the surroundin g matrix using atomistic computer simulations with EAM interatomic pot entials. Many different grain boundary structures were found to have v ery similar energies for the same orientation of the two crystals and the grain boundary plane. The possible transformations among these str uctures that may result from the interaction of the boundaries with di slocations or antiphase boundaries were studied, including the energet ics of the junctions between the different structures. The role of the multiplicity of structures and these transformations in the grain bou ndary mechanical properties is discussed and a model is proposed for t he tendency to grain boundary brittleness observed in Ni3Al. (C) 1998 Elsevier Science Limited. All rights reserved.