The crystallography of the martensitic transformation in equiatomic nickel-titanium

The microstructure and linear superelasticity of cold-drawn TiNi alloy

“…The spots derived from the M and the T1 are in mirror symmetry of each other with respect to the (111( ) plane, whereas the spots derived from the M and T2 are consistent with Fig. 2(c) in the work of Knowles and Smith [3], in which the 011 Type II twinning was first reported in the martensite in TiNi alloy. It could be conjectured that no considerable macroscopic strain could be available through variant coalescence, the further deformation procedure would take place mainly inside the martensite variants and the further rearrangement of substructural bands would occur, especially between the 011 Type II and the (111( ) Type I twinning plates.…”

“…Yet, with the increase of the area reduction, the amount of the 011 Type II twinning gradually reduces. As is well known, the 011 Type II twinning is the most frequently observed twinning mode in the thermal martensite [5], which has also been pointed out theoretically to be a lattice invariant shear [3,4]. Since the microstructure is wholly martensitic at the room temperature for the present alloy before cold-drawing, the appearance of the 011 Type II twinning bands is clearly to provide the necessary lattice invariant shear during the martensitic transformation which had finished before cold-drawing.…”

“…The substructure of each single martensite variant had been confirmed to be dominantly 011 Type II twin [3][4][5], with a few (111( ) Type I twin observed [5]. The present TEM observations indicate that the coalescence of martensite variants happens after the specimen is subjected to 5% area reduction, as shown in Fig.…”

“…As is well known for the as-annealed and undeformed TiNi alloy, the martensite variants exhibit selfaccommodation morphology, with the various twinning boundaries being straight and well defined [1][2][3][4][5]12]. The substructure of each single martensite variant had been confirmed to be dominantly 011 Type II twin [3][4][5], with a few (111( ) Type I twin observed [5].…”

Infinitesimal approach to the crystallography of martensitic transformation: application to Ni-Ti

“…Here, the paper by Knowles and Smith [11] and that by Matsumoto, Miyazaki, Otsuka and Tamura [12], the calculations based on the phenomenological theory, are referred to. The rational interface plane, (1, 1, 0) for ƒ ϭ 0.2710 and (1, 1, Ϫ1) for ƒ ϭ 0.3102, were also reported by both groups.…”