Reversible change of shape in mabtensitic transformations

Physical metallurgy of Ti–Ni-based shape memory alloys

“…The mechanical behavior associated with the R-phase was first observed by Khachin and co-workers [99,100] by tensile tests on binary Ti-Ni alloys. They observed two-stage yielding in the S-S curve, and ascribed the first stage due to the rearrangement of R-phase variants, and the second stage to the stress-induced martensitic transformation from the R-phase to B19 0 martensite.…”

“…Although the R-phase was reported to be tetragonal [103] at one time, people later recognized rhombohedral distortion upon the transformation from X-ray powder diffraction patterns, since {1 1 0} and {1 1 2} reflections split with decreasing temperature, although {2 0 0} reflections do not [100,101,104]. This means that the lattice can be described by stretching the cubic parent lattice along the h1 1 1i diagonal direction.…”

“…9. Thirdly the shape memory and superelasticity effects [67,[99][100][101][102], which are characteristic of thermoelastic martensitic transformation, are also observed associated with this phenomenon. This simply means that B2-R transformation is a martensitic transformation, which competes with B2-B19 0 transformation.…”

Transformation behavior and shape memory characteristics of thermo-mechanically treated Ti–(45−x)Ni–5Cu–xV (at%) alloys

“…Ternary Ti-Ni-X alloys made by substitution of Fe, Al, Co, Cr, Mo for Ti in near equiatomic Ti-Ni alloys induce the B2-R transformation, and thus transformation occurs in two-stage, B2-R-B19 0 [6][7][8][9][10]. Those elements are believed to induce the B2-R transformation by suppressing the B2-B19 0 transformation.…”

Transformation behavior of Ti–Ni–Cu–Mo alloys

“…Solution treated near equiatomic Ti-Ni alloys showed the B2 (cubic)-B19 (monoclinic) transformation [1]. Substitution of Fe, Al, Co, Cr, Mo for Ti in near equiatomic Ti-Ni alloys induced the B2-R (trigonal) transformation, and thus transformation occurred in two-stage, B2-R-B19 [2][3][4][5][6]. Substitution of Cu, Pd for Ni in near equiatomic Ti-Ni alloys induced the B2-B19 (orthorhombic) transformation, and thus transformation occurred in two-stage, B2-B19-B19 [7,8].…”