Atomistic aspects of the deformation of NiAl

Properties of dislocations in B2-NiAl have been studied atomistically using an embedded atom potential. The response of dislocation cores to applied homogeneous shear stresses is investigated and the Peierls stresses of straight dislocations are determined. The results are in many details in excellent agreement with experimental observations. Specifically, the behaviour of the [1 1 1] dislocations, their slip planes, cross-slip behaviour and the limiting role of the screw dislocation can be explained. Similarly, the appearance of the {2 1 0} plane as a secondary slip plane for the [1 0 0] dislocations can be rationalised. Furthermore, the interaction of the dislocations with structural point defects is studied. Comparison with the flow stress of off-stoichiometric NiAl from the literature shows that the individual point defects cannot be made responsible for the strong increase of the flow stress, suggesting that more complex defect structures may play an important role. (C) 1999 Elsevier Science Ltd. All rights reserved.