On the Stress-Induced Formation of R-Phase in Ultra-Fine-Grained Ni-Rich NiTi Shape Memory Alloys

Olbricht, Jürgen; Yawny, A.; Pelegrina, J.L.; Dlouhý, A.; Eggeler, Gunther

doi:10.1007/s11661-011-0679-y

Cited by 52 publications

(61 citation statements)

References 41 publications

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“…Recently, it was shown that the width of the mechanical hysteresis in PE SMAs is governed by the crystallographic compatibility between martensite and austenite [21]. It is important to highlight that the mechanical properties of PE NiTi show a very strong Clausius-Clapeyron type of temperature dependence [22]. An increase in temperature by 10 K, for example, is associated with an increase in both plateau stresses by about 65 MPa.…”

Section: Introductionmentioning

confidence: 99%

“…1a. Olbricht et al [22] showed that higher plateau stresses (caused by higher temperatures) can promote irreversible deformation based on dislocation plasticity. Therefore, PE can only be applied within a certain temperature window.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, PE can only be applied within a certain temperature window. Olbricht et al [22] studied the mechanical behavior of commercial PE NiTi wires. It was observed that a good shape recovery was only obtained between 20 and 70°C.…”

Section: Introductionmentioning

confidence: 99%

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Twinning-Induced Elasticity in NiTi Shape Memory Alloys

Birk

Biswas

Frenzel

et al. 2016

Shap. Mem. Superelasticity

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Pseudoelasticity (PE) in shape memory alloys relies on the formation of stress-induced martensite during loading and on the reverse transformation during unloading. PE yields reversible strains of up to 8 % and is applied in applications such as medical implants, flexible eye glass frames, damping elements, and others. Unfortunately, PE shows a strong temperature dependence and thus can only be exploited within a relatively narrow temperature window. The present work focuses on a related process, which we refer to as twinning-induced elasticity (TIE). It involves the growth and shrinkage of martensite variants which are stabilized by dislocations, which are introduced by appropriate cold work. TIE yields reversible strains of the order of 3 %. The TIE effect does not suffer from the strong temperature dependence of PE. The weak temperature dependence of mechanical TIE properties makes TIE attractive for applications where temperature fluctuations are large. In the present work, we study the TIE effect focusing on Ni 50 Ti 50 shape memory alloy wires. The degree of plastic pre-deformation of the initial material represents a key parameter of the ingot metallurgy processing route. It governs the exploitable recoverable strain, the apparent Young's modulus, and the widths of the mechanical hysteresis. Dynamic mechanical analysis is used to study the effects of pre-deformation on elementary microstructural processes which govern TIE.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Twinning-Induced Elasticity in NiTi Shape Memory Alloys

Birk

Biswas

Frenzel

et al. 2016

Shap. Mem. Superelasticity

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“…Nitinol can exhibit secondary deformation during mechanical testing, such as stress-induced martensite, and this has contributed to problems in being able to measure its mechanical properties [22]. Therefore, using conventional mechanical testing methods to measure the material properties of Nitinol, such as elastic modulus, have often not been successful [24].…”

Section: B Nitinol For Tuneable Resonance Devicesmentioning

confidence: 99%

A Comparison of Two Configurations for a Dual-Resonance Cymbal Transducer

Feeney

Lucas

2018

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Abstract-The ability to design tuned ultrasonic devices that can be operated in the same mode at two different frequencies has the potential to benefit a range of applications, such as surgical cutting procedures where the penetration through soft then hard tissues could be enhanced by switching the operating frequency. The cymbal transducer has recently been adapted to form a prototype ultrasonic surgical cutting device that operates at a single frequency. In this paper, two different methods of configuring a dual-resonance cymbal transducer are detailed. The first approach relies on transducer fabrication using different metals for the two end-caps, thereby forming a dual-resonance transducer. The second employs transducer end-caps composed from a shape memory alloy, superelastic Nitinol. The resonance frequency of the Nitinol transducer depends on the phase microstructure of the material, switchable through the temperature and/or stress dependency of the Nitinol end-caps. The vibration response of each transducer is measured through electrical impedance measurements and laser Doppler vibrometry, and finite element analysis is used to show the sensitivity of transducer modal response to the fabrication processes. Through this research, two viable dual-resonance cymbal transducers are designed and characterised, and compared to illustrate the advantages and disadvantages of the two different approaches.

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“…Like the A $ M transformation, the A $ R transformation also shows shape memory effect and pseudoelasticity [8,9]. Moreover, the A $ R transformation shows attractive properties, such as narrow thermal or stress hysteresis [10,11], fast response to temperature change [1,12,13], as well as high functional stability during thermomechanical cycling [13][14][15][16]. Based on these unique properties, although the transformation strain is small (*1 %) [9,17], various devices have been developed applying the A $ R transformation after proper structural design [18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Fundamental Development on Utilizing the R-phase Transformation in NiTi Shape Memory Alloys

Wang

Kustov

Verlinden

et al. 2015

Shap. Mem. Superelasticity

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In near equiatomic NiTi alloys, the reversible thermoelastic transformation between B2-structured austenite phase and the R-phase is attracting increasing interest for practical applications. However, the following two issues limit the widespread utilization of the R-phase transformation: (1) there is no effective approach to control the R-phase transformation temperatures; (2) it is not easy to largely separate the temperature domain of the R-phase and the B19 0 martensite phase transformation, especially in the presence of an external force. This article reviews concisely the work of the present authors on solving the above two problems. The effect of grain size on the aging microstructure and related transformation behavior is first discussed. Inspired by these findings, an approach to solve the above two problems has been developed by introducing nanoscaled Ni 4 Ti 3 precipitates in the samples with micronsized grains. The performance of alloys associated with the R-phase transformation, which shows controllable transformation temperatures, is summarized.

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On the Stress-Induced Formation of R-Phase in Ultra-Fine-Grained Ni-Rich NiTi Shape Memory Alloys

Cited by 52 publications

References 41 publications

Twinning-Induced Elasticity in NiTi Shape Memory Alloys

Twinning-Induced Elasticity in NiTi Shape Memory Alloys

A Comparison of Two Configurations for a Dual-Resonance Cymbal Transducer

Fundamental Development on Utilizing the R-phase Transformation in NiTi Shape Memory Alloys

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