Hydrogen solubility and diffusion in the shape-memory alloy NiTi

Schmidt, R.; Schlereth, Michael; Wipf, H.; Aßmus, W.; Müllner, M.

doi:10.1088/0953-8984/1/14/003

Cited by 90 publications

(47 citation statements)

References 16 publications

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“…For ideal B2, the XRD pattern actually differs from those measured. 2,10,11 In addition, from previous and present DFT results, the B2 energy relative to BCO is 48 meV/atom (557 K), much too high compared to the observed T c ≈ 313 K.…”

Section: Introductioncontrasting

confidence: 80%

“…1), which agrees with known data from neutron scattering and calorimetry, 9,11 as well as XRD. 2,5,10,11 Intriguingly, this structure has large atomic displacements from the ideal B2 sites, up to 22% of the B2 lattice constant at 0 K -above that suggested by the Lindemann criterion 12 for melting! This predicted austenitic structure cannot be describe by B2 symmetry, although in diffraction it appears B2 on average (Fig.…”

Section: Introductionmentioning

confidence: 86%

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Stable atomic structure of NiTi austenite

Zarkevich

Johnson

2014

Phys. Rev. B

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Nitinol (NiTi), the most widely used shape-memory alloy, exhibits an austenite phase that has yet to be identified. The usually assumed austenitic structure is cubic B2, which has imaginary phonon modes, hence it is unstable. We suggest a stable austenitic structure that "on average" has B2 symmetry (observed by X-ray and neutron diffraction), but exhibits finite atomic displacements from the ideal B2 sites. The proposed structure has a phonon spectrum that agrees with that from neutron scattering, has diffraction spectra in agreement with XRD, and has an energy relative to the ground state that agrees with calorimetry data.

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Section: Introductioncontrasting

confidence: 80%

Section: Introductionmentioning

confidence: 86%

Stable atomic structure of NiTi austenite

Zarkevich

Johnson

2014

Phys. Rev. B

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“…1 The 1173 K isothermal section of the Nb-Ti-Ni ternary system. 13) From these experimental results, it is interesting to investigate hydrogen permeability È of the Nb-(TiNi) duplex phase alloys. This paper describes a study on the relation between microstructures and È in the as-cast NbTi-Ni alloys.…”

Section: Introductionmentioning

confidence: 99%

Microstructures and Hydrogen Permeability of Nb-Ti-Ni Alloys with High Resistance to Hydrogen Embrittlement

et al. 2005

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Microstructures and hydrogen permeability (È) of as-cast Nb-Ti-Ni alloys have been investigated by scanning electron microscopy (SEM) and by the gas permeation technique, respectively. The È value increases with increasing temperature and the amount of the Nb content for every alloy. In these alloys, the Nb 39 Ti 31 Ni 30 alloy, consisting of the primary bcc-(Nb, Ti) solid solution and the eutectic {(Nb, Ti)+TiNi} phase, shows the highest È, which is equivalent to that of Pd. On the other hand, the Nb 10 Ti 50 Ni 40 alloy, consisting of the primary B2-TiNi compound and the eutectic {(Nb, Ti)+TiNi} phase, shows the lowest È value among the alloys for which È is measurable. Eutectic microstructures suppress the hydrogen embrittlement, while the primary (Nb, Ti) phase contributes to the hydrogen permeation in these alloys. The present work demonstrates that duplex alloys containing eutectic microstructures are promising for hydrogen permeation membranes with high resistance to the hydrogen embrittlement.

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“…40), dislocations interacting with vacancies (Ref. 45) and to twin boundaries. Recently, it has been discovered (Ref.…”

Section: Alloys Contaminated With Hydrogenmentioning

confidence: 99%

“…7,9,14,15,17,19,23,30,[45][46][47][48][49][50][51][52][53]. Remaining questions to be answered are: a) the origin of the non-thermally activated peaks P 150K and P 200K and b) the role of H in the local strain glass transition.…”

Section: H-contaminated Materialsmentioning

confidence: 99%

Recent progresses in the understanding of the elastic and anelastic properties of H-free, H-doped and H-contaminated NiTi based alloys

Mazzolai¹

2011

AIP Advances

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This review is focused on the influence of interstitial hydrogen and alloy compositional changes on the internal friction (IF) spectrum and elastic Young's modulus (E) of NiTi based shape memory alloys. In the martensitically transforming binary alloys Ni50+xTi50-x (x≤1.3) vacuum annealed and furnace cooled (H-free), besides the well known IF peak associated with the martensitic transition two additional non-thermally activated peaks (P150K and P200K′) are present due to some sort of second-order phase transitions. In martensitically transforming Ni50+xTi50-x and Ti50Ni50-yCuy alloys doped with hydrogen two thermally activated peaks, PTWH and PH, appear which originate from stress-assisted motions of H-twin boundary complexes and isolated H-elastic dipoles (Snoek effect), respectively. In a H-free martensitically non-trasforming alloy (x=2), besides the non-thermally activated peak P150K, a frequency dependent dip is observed in the E(T) curves at a temperature Tg. This dip is similar to that reported in the literature for two other non-transforming alloys (x=1.5 and x=2.5), which, however, were also found to exhibit a thermally activated IF peak just below Tg. Most likely, these two alloys were contaminated with hydrogen during the preliminary solubilization in argon atmosphere and subsequent water quenching treatments given to them. The Young's modulus dip and the lower temperature IF peak have been both attributed to a novel type of phase transition reported in the literature as “strain glass transition”. The introduction of hydrogen into the non-transforming alloy with x=2 enhances the Young's modulus dip and gives rise to the H-Snoek peak PH just below Tg, which clearly appears to be the counterpart of the peak observed in the alloys (x=1.5 and x=2.5) solubilized in argon atmosphere and water quenched. The conclusion was reached in the present work that this last peak is not related to the strain glass transition but is rather an H-Snoek relaxation

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Hydrogen solubility and diffusion in the shape-memory alloy NiTi

Cited by 90 publications

References 16 publications

Stable atomic structure of NiTi austenite

Stable atomic structure of NiTi austenite

Microstructures and Hydrogen Permeability of Nb-Ti-Ni Alloys with High Resistance to Hydrogen Embrittlement

Recent progresses in the understanding of the elastic and anelastic properties of H-free, H-doped and H-contaminated NiTi based alloys

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