Formation of a triangular striated structure in the twin intersection area in γ-TiAl during room-temperature deformation

A triangular striated region, which is related to the type-I twin intersection in γ-TiAl during room-temperature deformation, has been investigated by high-resolution transmission electron microscopy (HREM). The triangular structure around the intersection area is supposed to be a result of the heavy lattice distortion in the case of the type-I twin intersection. Under a local stress concentration, some nanotwins were observed to nucleate at the ledges on the incoherent twin boundary of the incident twin tip. Some dislocation dissociations at the ledges may be responsible for nucleation of these nanotwins. These nanotwins within the triangular striated region propagate with a homogeneous 1/6 [112̄] twinning dislocation glide mechanism. The propagation of nanotwins can accommodate the lattice distortion of the triangular striated region without any crack at the nanotwin boundaries.