Effects of aging on the shape memory behavior of Ni-rich Ni50.3Ti29.7Hf20 single crystals

Saghaian, Sayed M.; Karaca, H.E.; Tobe, Hirobumi; Souri, Maryam; Noebe, Ronald D.; Chumlyakov, Y.I.

doi:10.1016/j.actamat.2014.12.040

Cited by 79 publications

(36 citation statements)

References 36 publications

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“…These recent studies clearly show that instrumented indentation techniques can be used to characterize the mechanical response of bulk and thin film NiTi alloys. In this study, Ni 50.3 Ti 29.7 Hf 20 alloy was selected since it has higher strength than other NiTi-based alloys and shows superelasticity at high temperatures of about 200 °C 30–33 . The main aim of this study is to characterize the mechanical behavior of NiTiHf alloys as a function of temperature under a spherical indenter in micro-scale and compare that with compression experiments at macro-scale.…”

Section: Introductionmentioning

confidence: 99%

Rapid Characterization of Local Shape Memory Properties through Indentation

Karaca

Cheng

2017

Sci Rep

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AbstarctShape memory alloys (SMAs) have the ability to show large recoverable shape changes upon temperature, stress or magnetic field cycling. Their shape memory, material and magnetic properties (e.g. transformation temperatures, strain, saturation magnetization and strength) determine their prospects for applications from small-scale microelectromechanical systems to large scale aerospace and biomedical systems. It should be noted that properties of SMAs are highly temperature dependent. Generally, the conventional mechanical characterization methods (e.g, tension, compression, and torsion) are used on bulk samples of SMAs to determine those properties. In this article, it will be shown that indentation technique can be used as an alternative rapid method to determine some of the important shape memory properties of SMAs. Indentation response of a high-temperature NiTiHf alloy was determined as a function of temperature. A clear relationship between the work recoverable ratio and transformation temperatures, superelastic and plastic behavior was observed. This work shows that indentation response can be used to measure local superelasticity response, determine phase transformation temperatures and reveal the temperature intervals of the deformation mechanisms of shape memory alloys.

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Section: Introductionmentioning

confidence: 99%

Rapid Characterization of Local Shape Memory Properties through Indentation

Karaca

Cheng

2017

Sci Rep

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“…As previously discussed, the recent body of work on NiTiHf alloys [50,72,75,83] has considered both polycrystals and single crystals for Hf contents less than 20 at.%. These recent works on compression have shown that the transformation strains fall far below the theoretical values [75].…”

Section: Discussion Of Resultsmentioning

confidence: 95%

Shape memory strains and temperatures in the extreme

Şehitoğlu

Patriarca

2017

Current Opinion in Solid State and Materials Science

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It is well known that the achievement of high transformation strains in shape memory alloys (SMAs) has been curtailed by plastic deformation mediated via dislocation slip. In particular, the utilization of SMAs at high temperatures is also hindered by plastic slip. In this paper, an overview of the most important SMAs is provided by constructing transformation strain, transformation temperature, and slip resistance plots to put existing works in perspective. To this plots, we added results on NiTiHf alloys which impart both high temperature capability and high slip resistance at unprecedented levels. The remarkable finding is that NiTiHf alloys can undergo transformation strains near 20% and transformation temperatures exceeding 400 °C

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“…Presen SME and SE, thermoelastic B (f = 16-30%) o at high externa [2][3][4][5]. On the other hand, in TiNi poly-and single crystals containing less than 51.0 at.% of Ni in the quenched and aged states at the axial stresses between 500-700 MPa the martensite achieves its yield strength, and superelasticity is accompanied by irreversible strains [1, 3,14,15].…”

Section: Methodsmentioning

confidence: 99%

“…Among the most common functional alloys are those based on nickel titanium with B2-(R)-B19′-thermoelastic martensitic transformations (MTs), which are widely applied due to a combination of large reversible strains during manifestation of SME and SE, high ductility, corrosion resistance, and biological compatibility. It is well known [1][2][3][4][5] that by increasing the content of Ni (С Ni ≥ 50.5 at.%) both in binary alloys, such as TiNi, and in the NiTiHf alloys, it is possible to achieve a high-strength state of the В2-austenite (the stresses at the onset of plastic flow in the austenite turn out to be higher than G/100, G -shear modulus) due to the deviation of the alloy composition from stoichiometry and due to dispersion hardening in the case of precipitation of a large volume fraction (f > 7-8%) of coherent particles during aging.…”

Section: Introductionmentioning

confidence: 99%

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Orientation Dependence of Functional Properties in Heterophase Single Crystals of the Ti36.5Ni51.0Hf12.5 and Ti48.5Ni51.5 Alloys

et al. 2016

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The features of orientation dependence of stress-induced thermoelastic B2-(R)-B19′-martensitic transformations in single crystals of the Ti 48.5 Ni 51.5 and Ni 51.0 Ti 36.5 Hf 12.5 (at.%) alloys, which contain disperse particles of the Ti 3 Ni 4 and H-phase, respectively, are revealed along with those of their shape-memory effects (SME) and superelasticity (SE). It is experimentally demonstrated that irrespective of the crystal structure of disperse particles measuring more than 100 nm, for their volume fraction f > 16% there is a weaker orientation dependence of the reversible strain in the cases of manifestation of SME and SE. In the orientations of Class I, wherein martensitic detwinning introduces a considerable contribution into transformation strain, the values of SME | SME | and SE | SE | decrease by over a factor of two compared to the theoretical lattice strain value | tr0 | for a B2-B19′-transformation and the experimental values of reversible strain for quenched TiNi crystals. In the orientations of Class 2, wherein detwinning of the martensite is suppressed as is the case in quenched single-phase single crystals, the reversible strain is maintained close to its theoretical value |ε tr0 |. Micromechanical models of interaction between the martensite and the disperse particles are proposed, which account for the weaker orientation dependence of | SME | and | SE | due to suppression of detwinning of the B19′-martensite crystals by the particles and a transition from a single-variant evolution of the stress-induced martensitic transformations to a multiple-variant evolution of transformations in the cases of increased size of the particles and their larger volume fractions.

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Effects of aging on the shape memory behavior of Ni-rich Ni50.3Ti29.7Hf20 single crystals

Cited by 79 publications

References 36 publications

Rapid Characterization of Local Shape Memory Properties through Indentation

Rapid Characterization of Local Shape Memory Properties through Indentation

Shape memory strains and temperatures in the extreme

Orientation Dependence of Functional Properties in Heterophase Single Crystals of the Ti36.5Ni51.0Hf12.5 and Ti48.5Ni51.5 Alloys

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