Interactions of 1/6<112]{111} twinning dislocations with large-angle grain boundaries, in duplex alloys following room-temperature tensile deformation, were investigated by means of transmission electron microscopy. The dislocation reactions which described slip transfer processes were identified by using image-matching of experimental and calculated images, and were interpreted in terms of the direction of the applied stress. The results demonstrated that, at a general large-angle γ/γ grain boundary, slip transfer of incoming 1/6<112]{111} twinning dislocations could be accommodated by the generation of glide in both grains via the movement of ½<110]-type dislocations on prismatic glide planes. This was defined by the 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 was therefore a generalization of the dislocation interactions observed for edge-type deformation twins which intersected coherent γ/γ twin boundaries. The results indicated that general grain boundaries in duplex Ti-Al alloys provided strong barriers to deformation-twin propagation, but did not necessarily lead to the build-up of stresses that were sufficient to initiate fracture. Even at room temperature, the pile-up stress could be at least partially relieved by a plastic response at the boundary; involving the propagation of prismatic glide dislocations.

Slip Transfer of Deformation Twins in Duplex γ-Based Ti-Al Alloys - III. Transfer across General Large-Angle γγ Grain Boundaries. M.A.Gibson, C.T.Forwood: Philosophical Magazine A, 2002, 82[7], 1381-404