The intermediate phase of the shape-memory alloy NiTi

Tietze, H.; Müllner, M.; Selgert, P.; Aßmus, W.

doi:10.1088/0305-4608/15/2/004

Cited by 26 publications

(14 citation statements)

References 9 publications

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“…The other domains, except for the translational ones, are obtained by the action on the first domain by the representative elements of the cosets in the decompo sition of the group O h with respect to the subgroup C 2h = 2/m: sponding to the arms k 9 , k 10 and k 11 , k 12 (plane (100)) are obtained by the action onto the domains shown in Fig. 3 Thus, we arrive at conclusions analogous to those made in [15,16], from which it follows that the domains produced by displacements of atoms with WVs of the 1/3〈110〉 type are not domains of the R phase with either hexagonal or rhombohedral lattices. The other structures of displacements with the SGs listed in Table 8 have a base centered lattice (11) belonging, after an appropriate deformation, to mon oclinic or orthorhombic system.…”

Section: Discussionsupporting

confidence: 66%

“…As concerns to the SPTs in TiNi based В2 com pounds, the only group (of all the subgroups listed in Table 8) that is encountered in the literature is the = P2/m group [15]. The authors of [15] investi gated diffraction effects in the premartensitic temper ature range (from 348 K to 248 K (which corresponds the onset of the formation of the martensitic phase)) in an almost equiatomic TiNi single crystal.…”

Section: Discussionmentioning

confidence: 99%

“…The authors of [15] investi gated diffraction effects in the premartensitic temper ature range (from 348 K to 248 K (which corresponds the onset of the formation of the martensitic phase)) in an almost equiatomic TiNi single crystal. At 348 K, extra reflections of the 1/3〈110〉 type appeared, whose intensity increased with approaching martensitic transformation According to [15], the intermediate structure has a symmetry of the P2/m type; the num ber of possible orientational domains of this phase is equal to 12. The structure of each domain is formed due to the development of a single wave of atomic dis placements of the 〈110〉k 〈1 0〉e type.…”

Section: Discussionmentioning

confidence: 99%

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Symmetry of pretransition structures in alloys with a B2-type superstructure

Zolotukin

Лотков

Klopotov

et al. 2012

Phys. Metals Metallogr.

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Transformation properties of the order parameters-atomic displacements in the B2 structure related to the wave vectors of the 1/3͗110͘ and 1/3͗111͘ type, which, in particular, are observed in B2 titanium nickelide based alloys, have been studied. Irreducible representations and their basis vectors related to these wave vectors have been determined. Subgroups of the symmetry group of the B2 structure relative to which the order parameters are invariant have been calculated. The feasibility of the realization of these subgroups as symmetry groups of the pretransition structures that arise prior to the B2 → R martensitic transformation in titanium nickelide based alloys has been analyzed.

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Section: Discussionsupporting

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Symmetry of pretransition structures in alloys with a B2-type superstructure

Zolotukin

Лотков

Klopotov

et al. 2012

Phys. Metals Metallogr.

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“…On the other hand the wave vector k 1/3 agrees with the R-phase, incommensurate premartensitic phenomena seen with the inelastic neutron-scattering experiment. 37 The calculations show that the minimum of the soft mode at k M is quite wide in the reciprocal space, and includes the wave vector k 1/3 . Since atomic distortions accompanying the phase transitions are rather large, one may expect that the anharmonic terms do not remain constant within the Brillouin zone, hence, they may influence the real phonon vibrations appreciably.…”

Section: Discussionmentioning

confidence: 90%

Lattice dynamics of NiTi austenite, martensite, andRphase

Parliński

Parlinska-Wojtan

2002

Phys. Rev. B

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Using the local-density approximation, calculating the Hellmann-Feynman forces, and applying the direct method, the phonon-dispersion relations of cubic austenite, trigonal R, orthorhombic and monoclinic martensitic phases of the NiTi intermetallic compound have been derived. In the austenite phase we have found a soft phonon branch with a minimum at the M reciprocal-lattice point. The orthorhombic structure, in turn, shows a shear low-frequency mode favoring a martensitic phase. The phonon-dispersion relations indicate that martensitic and R phases are dynamically stable. For the martensitic and R phases the phonon density of states, free energies, and heat capacities have been calculated. We find that the first-order R-phase-martensite phase transition temperature occurs at T c ϭ285 K.

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“…This has been, in part, a motivator for considerable theoretical [1][2][3][4][5] and experimental research [6][7][8][9][10][11][12][13] into the mechanisms behind its shape-memory effect. A complete assessment of compositional effects on the physics controlling the relevant phase transitions, however, has not been developed.…”

Section: Introductionmentioning

confidence: 99%

Soft-phonon feature, site defects, and a frustrated phase transition inNi50Ti47Fe3: Experiments and first-principles calculations

et al. 2008

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A soft-phonon feature associated with the shape-memory transition in NiTi is observed in the phonon density of states ͑DOS͒ of the B2 phase of both NiTi and Ni 50 Ti 47 Fe 3 ͑with Fe substituted for Ti͒ using inelastic neutron scattering. In both alloys, the feature softens with decreasing temperature, but the softening occurs about 100 K lower in the Fe-substituted alloy, indicating a decreased transition temperature. Electrical resistivity and magnetic susceptibility verify the decreased transition temperature but also show that the transition develops second-order-like behavior similar to that observed by others in Ni 44 Ti 50 Fe 6 ͑with Fe substituted for Ni͒. First-principles calculations supported by Mössbauer spectroscopy and neutron diffraction indicate a double-defect scenario, where Fe occupies Ni sites and the displaced Ni occupies the empty Ti sites in the Ti-substituted alloys. A comparison between the current results for Ti-substituted alloys, and related experimental data for alloys featuring Fe substitution for Ni, indicates that the instability temperature is controlled by the number of Fe atoms occupying the Ni sites, while the second-order-like behavior is caused by the addition of the Ni antisite defects. We argue that this latter behavior results from percolated networks of interacting defects acting to frustrate the symmetry-breaking strains.

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The intermediate phase of the shape-memory alloy NiTi

Cited by 26 publications

References 9 publications

Symmetry of pretransition structures in alloys with a B2-type superstructure

Symmetry of pretransition structures in alloys with a B2-type superstructure

Lattice dynamics of NiTi austenite, martensite, andRphase

Soft-phonon feature, site defects, and a frustrated phase transition inNi50Ti47Fe3: Experiments and first-principles calculations

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