Abstract
The interactions of ⅙〈112]{111} twinning dislocations with large-angle grain boundaries, in duplex Ti-Al alloys after room-temperature deformation in tension, have been investigated by transmission electron microscopy. The dislocation reactions that describe the slip transfer processes have been identified using image matching between experimental and computed images and are discussed and interpreted in terms of the direction of the applied tensile stress. The results demonstrate that, at a general large-angle γ-γ grain boundary, slip transfer of incoming ⅙〈112]{111} twinning dislocations can be accommodated by the generation of glide in both grains by the movement of ½〈110]-type dislocations on prismatic glide planes, defined by the operative ½〈110] Burgers vector of the outgoing glide dislocations and the line of intersection of the incoming deformation twin with the grain boundary. This mechanism therefore represents a generalization of the dislocation interaction observed for edge-type deformation twins intersecting coherent γ-γ twin boundaries. The results indicate that general grain boundaries in duplex Ti-Al alloys, although providing strong barriers to deformation twin propagation, do not necessarily lead to the build-up of stresses sufficiently large to initiate fracture since, even at room temperature, the pile-up stress can at least be partially relieved by a plastic response at the boundary involving the propagation of prismatic glide dislocations.