Weak-beam image simulations were made of a ½<112] edge dislocation, in γ-phase Ti-50wt%Al, which dissociated into three 1/6<112] partial dislocations that bounded superlattice intrinsic stacking-fault and superlattice extrinsic stacking-fault ribbons of equal width. The simulations included one of the 2 core configurations of a composite Shockley partial dislocation which had been found to explain the observed image contrast; plus 2 others that involved dissociation into stair-rods. The simulated images could not be distinguished from the predictions of the model for the composite Shockley dislocation. They accounted equally well for the observed image contrast. A previous claim, that configurations which consisted of stair-rod dislocations could be ruled out, was not supported. Core structures, which involved sessile stair-rod dislocations, explained the locked nature of the edge dislocation. Values which had previously been found, for the true separation between pairs of partial dislocations, were used to calculate the superlattice intrinsic stacking-fault and superlattice extrinsic stacking-fault energies. These were equal to 123mJ/m2.

On the Core Structure of <112] Edge Dislocations in γ-TiAl. C.Lang, P.B.Hirsch, D.J.H.Cockayne: Philosophical Magazine Letters, 2004, 84[3], 139-48