On the two-way shape memory behavior in NiTi alloy—An experimental analysis

Wada, Kiyohide; Liu, Yong

doi:10.1016/j.actamat.2008.03.005

Cited by 40 publications

(18 citation statements)

References 32 publications

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“…The same Cu-Al-Ni wire of 90 m diameter is then "trained" by a scheme similar to that used by Wada and Liu,20 i.e., by loading in the martensitic state and then heating to above the austenite finish temperature. While maintaining this constant load, the wire is then subjected to thermal cycling across the transformation temperature range, at 5°C/ min far from transformation temperatures and 1°C/ min close to and between them.…”

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confidence: 99%

Shape memory and superelasticity in polycrystalline Cu–Al–Ni microwires

Chen

Zhang

Dunand

et al. 2009

Applied Physics Letters

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We report a strategy to significantly improve the ductility and achieve large superelastic and shape memory strains in polycrystalline Cu–Al–Ni shape memory alloys that are normally brittle. We use a liquid-phase (Taylor) wire forming process to obtain microwires of 10–150 μm diameter with a bamboo grain structure. The reduction of grain boundary area, removal of triple junctions, and introduction of a high specific surface area in the wire decrease constraints on the martensitic transformation, and permit both superelasticity and stress-assisted two-way shape memory with recoverable strains as high as 6.8%.

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confidence: 99%

Shape memory and superelasticity in polycrystalline Cu–Al–Ni microwires

Chen

Zhang

Dunand

et al. 2009

Applied Physics Letters

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“…12,[22][23][24][25][26] Prior deformation slightly beyond the strain limit of the martensitic transformation as a means to develop two-way memory effect is to create such an anisotropic dislocation structure in NiTi SMAs. 14,[27][28]30 The two-way actuation of the Nb nanoribbon-nanocrystalline NiTi composite studied in this work is induced by a new mechanism, via a long range directional stress coupling between the Nb nanoribbons and the NiTi matrix, as opposed to the anisotropic short range stress fields associated with the deformation-induced dislocations. The presence of the long range coupling stresses (elastic lattice strains) between the Nb nanoribbons and the NiTi matrix is evident in Figures 5d and 5e.…”

Section: Resultsmentioning

confidence: 99%

Achieving Superior Two-Way Actuation by the Stress-Coupling of Nanoribbons and Nanocrystalline Shape Memory Alloy

Hao

Liu

Ren

et al. 2016

ACS Appl. Mater. Interfaces

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Inspired by the driving principle of traditional bias-type two-way actuators, we developed a novel two-way actuation nanocomposite wire in which a massive number of Nb nanoribbons with ultralarge elastic strains are loaded inside a shape memory alloy (SMA) matrix to form a continuous array of nanobias actuation pairs for two-way actuation. The composite exhibits a two-way actuation strain of 3.2% during a thermal cycle and an actuation stress of 934 MPa upon heating, which is about twice as high as that (∼500 MPa) found in reported two-way SMAs. Upon cooling, the composite shows an actuation stress of 134 MPa and a mechanical work output of 1.08 × 10(6) J/m(3), which are about three and five times higher than those of reported two-way SMAs, respectively. It was revealed that the massive number of Nb nanoribbons in the compressive state provides the high actuation stress and high work output upon cooling, and the SMA matrix with high yield strength offers the high actuation stress upon heating. Compared to traditional bias-type two-way actuators, the two-way actuation composite with a small volume and simple construct works well with the miniaturization and simplification of actuators.

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“…However, apart from this single qualitative observation we are not aware of a more explicit evaluation of sample size effects on G el . This open area is especially interesting and relevant for shape memory properties triggered by thermal excursions (as opposed to superelastic stress cycles), because thermally-and mechanically-induced martensite differ significantly in number of variants and transformation morphology [13,[15][16][17][18].It is the purpose of this study to explore sample size effects on thermally induced transformations, and in particular to shed more light on sample size effects upon the martensitic transformation ranges and ΔG el .…”

Section: Introductionmentioning

confidence: 99%