TEM observations of twin intersections in a Ti–47Al–2Cr–2Nb–0.1Y alloy compressed at room temperature

Twin intersections in TiAl alloy compressed at room temperature were investigated by high-resolution electron microscopy (HREM). One incident twin (TI) was observed to divide into three thin twin bands and leave several superlattice intrinsic stacking faults (SISFs) in the barrier twin (TB). It was a process related to the dislocation dissociation: (1/2)[1 1 2] → (1/6)[1 1 2] + SISF + (1/6)[1 1 2] + SESF + (1/6)[1 1 2]. The nucleation of type-I twin intersection was also observed. The incident twin was found to be a bundle of SISFs, instead of a perfect twin lath. In addition, a triangular striated structure around type-I twin intersection was examined by HREM. The formation mechanism of this triangular striated structure and the related dislocation reactions were discussed.