The deformation structure of B2 parent phase in Ti–Ni shape memory alloy around 573K was investigated by transmission electron microscopy. Serrations were seen in stress–strain curve, which corresponds to the formation of various planar defects of twin relation with respect to {112} {113}, {115}, {447} planes and so on. These defects could be expressed by particular Σ values on the basis of the coincidence site lattice model, since they were <110> symmetric tilt boundaries in a wide sense. It was also demonstrated that the sigma combination rule of the coincidence site lattice model could be applied to the triple junction of such defects.

Crystallography of Deformation Twin Boundaries in a B2 Type Ti–Ni Alloy. M.Nishida, M.Matsuda, T.Fujimoto, K.Tanka, A.Kakisaka, H.Nakashima: Materials Science and Engineering A, 2006, 438-440, 495-9