The nature of dissociated superlattice dislocations in Mn-modified Al3Ti which had been deformed at 673K was studied by means of transmission electron microscopy weak-beam imaging, assisted by computer simulation. The observed images of dissociated a<110> super-dislocations under various diffraction conditions were matched successfully with simulated images which were based upon the assumption of dissociation into two a/2<110> partials, separated by antiphase boundary. The simulations showed that fringe contrast from stacking faults and single dislocation images should be observed under certain diffraction conditions for a superlattice intrinsic stacking fault-dissociated super-dislocation. These differences made it possible to pre-select a series of imaging conditions, so as to identify the dislocation mechanism; even if the partials were very closely spaced. It was shown that the g•b criterion had to be used with caution when attempting to identify partial dislocations; especially when the spacing of the partials was small.

S.Zhang, W.W.Milligan, D.E.Mikkola: Philosophical Magazine A, 1995, 71[3], 523-36