Nitinol Fatigue: A Review of Microstructures and Mechanisms

Pelton, Alan R.

doi:10.1007/s11665-011-9864-9

Cited by 196 publications

(177 citation statements)

References 14 publications

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“…A similar phenomenon has been reported in shape memory alloys, where dislocations can form at the interface between the martensite and austenite domains, hindering the interface movement [29]. As a result, more energy and thus higher temperatures are needed to trigger the reverse transformation [30]. Another contributing factor might be the difference in terms of monoclinic variant preference during the two transformation processes; the uniaxial compression might not favor the same variant correspondence as the unidirectional temperature change, as we will discuss in more detail below.…”

Section: Mechanically Compressed Zirconia Pillarsupporting

confidence: 69%

In-situ studies on martensitic transformation and high-temperature shape memory in small volume zirconia

Zeng

Tamura

et al. 2017

Acta Materialia

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Shape memory effect (SME) High temperature deformation High temperature shape memory ceramics a b s t r a c t Recently, the shape memory effect with significant recoverable shape deformation has been discovered in small volume single-crystal zirconia. The application potential for such shape memory ceramics has spurred in-depth exploration of the martensitic transformation crystallography and high temperature shape memory effect. In this work, the martensitic transformation of micron-sized zirconia has been studied in both a pristine as-produced condition and after micromechanical compression, using synchrotron scanning micro X-ray diffraction (mXRD). The pristine zirconia was found to transform into the monoclinic phase via a different crystallographic path than the compressed zirconia, resulting in distinct monoclinic variant preferences. The characteristic martensitic transformation temperatures were also found to be higher after uniaxial compression than in the pristine condition. Such observations provide insight on the differences between stress-induced and thermally-induced martensitic transformation. Moreover, we have observed a full cycle of the shape memory effect with large recoverable strain (7%) in micron-sized zirconia at a temperature of 400 C. Our findings provide an important guideline to tailor the high-temperature shape memory properties of zirconia for further scientific research and engineering applications.

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Section: Mechanically Compressed Zirconia Pillarsupporting

confidence: 69%

In-situ studies on martensitic transformation and high-temperature shape memory in small volume zirconia

Zeng

Tamura

et al. 2017

Acta Materialia

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“…At strains of only about ~2%, cracking is observed after only a few transformation cycles (17). This is unlike shape memory metals such as Ni-Ti, which can access large strains up to ~8% and, at lower strain levels can be reversibly transformed up to millions of cycles (18).…”

mentioning

confidence: 98%

Shape Memory and Superelastic Ceramics at Small Scales

Lai

Gan

et al. 2013

Science

259

197

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Shape memory materials are a class of smart materials able to convert heat into mechanical strain (or strain into heat), by virtue of a martensitic phase transformation. Some brittle materials such as intermetallics and ceramics exhibit a martensitic transformation, but fail by cracking at low strains and after only several applied strain cycles. Here we show that such failure can be suppressed in normally brittle martensitic ceramics by providing a fine-scale structure with few crystal grains. Such oligocrystalline structures reduce internal mismatch stresses during the martensitic transformation, and lead to robust shape memory ceramics capable of many superelastic cycles to large strains; here we describe samples cycled up to 50 times, and samples which can show strains over 7%. Shape memory ceramics with these properties represent a new class of actuators or smart materials with a unique set of properties that include high energy output, high energy damping, and high temperature usage.One Sentence Summary: Fine-scale shape memory ceramics capable of many actuation cycles to strains up to 7%.Main Text: Shape memory materials are solid-state transducers, able to convert heat to strain and vice versa. They exhibit two unique properties: 1) the shape memory effect, which is the ability to transform to a "remembered" pre-defined shape upon the application of heat and 2) superelasticity, which is the ability to deform to large strains recoverably, while dissipating energy as heat. The underlying mechanism in crystalline shape memory materials is a thermoelastic martensitic transformation between two crystallographic phases that can be induced thermally (shape memory effect) or with the application of stress (superelasticity) (1, 2).The ability to transduce heat and strain renders shape memory materials useful in a wide variety of actuation, energy damping, and energy harvesting applications (3-7). To be of practical use, the material must be able to accommodate the extreme deviatoric strains associated with the

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“…In particular, the existing martensite in the as-welded material should have undergone detwinning during solicitation up to 10%, contributing to the irrecoverable strain of the welded joint. As for the austenite, it is expected that, aside from the introduction of dislocations which are known to occur during cyclic solicitation of NiTi [11,12], some retained martensite is found to occur due the blockage of the reverse martensitic transformation upon unloading [13,14]. In either case, the same phenomenon occurs: martensite stabilization.…”

Section: Introductionmentioning

confidence: 99%