Transmission electron microscopic observations of the dislocation substructure in Cu-8at%Al single crystals, deformed in tension, were carried out in order to clarify the cause of the twinning dislocation which produced conjugate twinning in this alloy. It was suggested that the correct Heidenreich-Shockley dislocation was obtained by reaction of the primary dislocation with the faulted (Frank) dipole. These interactions were expected to occur frequently during deformation. Various configurations of the twinning sources were analysed with respect to nucleation and growth of the twin. Geometrical features which were related to pinning of the component dislocations at the nodes formed, the motion of single twinning dislocations and the non-coherent twinning front, and the barriers encountered during twin growth were analysed. It was shown that there were no geometrical or energetic obstacles to the development of a macroscopic twin, via the pole mechanism, from the source proposed here.

Twinning Nucleation in Cu-8at% Al Single Crystals. M.Niewczas, G.Saada: Philosophical Magazine A, 2002, 82[1], 167-91