The  = 3 {112} interface was examined by using diffraction contrast and high-resolution transmission electron microscopic imaging techniques. It was noted that this boundary could have various structures which corresponded to different translation states. A study was made of whether the differences were due to intrinsic or extrinsic factors, and of their possible effect upon migration and interaction with extrinsic dislocations. Particular attention was paid to the relationship between the rigid-body translation, and the 9R stacking sequence which could form when the boundary dissociated. It was found that the dislocation model of this boundary gave a useful description of the structure and the observed orientation change. The dislocations were not really Shockley partial dislocations, but were a representation of the core structure of the grain boundary. Rotation of the interface plane could be easily incorporated. The main advantage of the complete dislocation model was that it could be related to the mode of migration and the behavior of the interface under stress. The dislocations which were used in the model had the same Burgers vectors as the dislocations of the DSC lattice. It was noted that, if the boundary were to form by packets of 3 partial dislocations climbing vertically downwards into perfect crystal, no misorientation would arise. However, the introduction of such an array by glide on parallel (111) planes did produce the required twin relationship. It was concluded that the degree to which  = 3 {112} boundaries dissociated depended not only upon the stacking-fault energy, but also upon the local stress state within the specimen. This could differ at various parts of the interface.

C.B.Carter, D.L.Medlin, J.E.Angelo, M.J.Mills: Materials Science Forum, 1996, 207-209, 209-12