It was found that, in Ti-rich compositions, plate-like precipitates of the tetragonal Al2Ti phase - with (001)P habit planes - formed on the {100}M planes of the L12 matrix. In Cr-stabilized alloys, the Al2Ti/L12 interfaces were coherent. In Ni- or Cu-stabilized alloys, networks of interfacial dislocations were present. It was shown that these networks accommodated a difference in lattice parameter between the L12 matrix and the a-parameter of the tetragonal Al2Ti phase. This in turn resulted from a slight decrease in the L12 lattice parameter upon replacing Cr by Ni or Cu. Analysis of these dislocations by using g.b rules, and the image-matching of transmission electron microscopic images, showed that the networks were based upon intersecting arrays of orthogonal edge dislocations with ½<110>M Burgers vectors. Irregularities in the networks often led to segments of these dislocations occurring in a screw orientation; thus permitting them to act as possible sources of ½<110>{111}M slip dislocations in the L12 matrix.

C.T.Forwood, M.A.Gibson: Materials Science Forum, 1995, 189-190, 353-60