Molecular statics simulations were made of dislocations in L10 structures, using three different embedded-atom method potentials that were fitted to the bulk properties of γ-TiAl. The three potentials were fitted to produce complex stacking-fault energies of 120, 320 and 580mJ/m2 so that the effects of variations in fault energy could be investigated parametrically. Core structures were determined for each of the potentials for the orientations: screw, 30° mixed, 60° mixed and edge. These cores were all planar apart from the screw orientations calculated using the 320 and 580mJ/m2 values. These showed substantial amounts of non-planar spreading. The 60° orientations for these two potentials had a tendency for the screw component of the displacement to spread out-of-plane and for the edge component to spread in the glide plane. The screw orientation of the 320mJ/m2 potential was found to have two possible states: planar and non-planar. The friction stresses were determined for all orientations of the 320mJ/m2 potential, since this appeared to represent γ-TiAl most closely. The friction stresses for the other potentials were determined only for the orientations producing the highest friction stress for the 320mJ/m2 potential. It was also found that the close-packed directions, screw and 60°, had the highest friction stress, with the more sparsely-packed directions having a considerably lower value. The friction stress for the 320mJ/m2 potential was found to be 250MPa, in good agreement with published experimental values of the critical resolved shear stress for γ-TiAl. Comparing line orientations with the same atomic directions, the effects of ordering on the friction stress predicted by Greenberg et al. (1991) were observed. These variations had a considerably smaller effect than did the atomic density along the line orientation.

Atomistics Simulations of Structures and Properties of ½<110> Dislocations using Three Different Embedded-Atom Method Potentials Fit to γ-TiAl. J.P.Simmons, S.I.Rao, D.M.Dimiduk: Philosophical Magazine A, 1997, 75[5], 1299-328