Breakdown of Shape Memory Effect in Bent Cu–Al–Ni Nanopillars: When Twin Boundaries Become Stacking Faults

Liu, Lifeng; Ding, Xiangdong; Sun, Jun; Li, Suzhi; Salje, Ekhard K. H.

doi:10.1021/acs.nanolett.5b03483

Cited by 11 publications

(3 citation statements)

References 51 publications

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“…Their domain switching and domain wall (or twin boundary) motion dominate these effects. For example, Cu-Al-Ni nanopillars show a strong shape memory recoverability through twinning and de-twinning mechanisms, while this effect is destroyed by high densities of stacking faults in small size nanopillars [1]. In Ti-Ni-based shape memory alloys, the motion of twin boundary could improve fatigue resistance when the temperature is below the martensitic transition temperature [2].…”

Section: Introductionmentioning

confidence: 99%

The interaction between vacancies and twin walls, junctions, and kinks, and their mechanical properties in ferroelastic materials

Ding

et al. 2019

Acta Materialia

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Vacancies strongly interact with twin boundaries and often change dramatically the properties of a ferroelastic material. However, the understanding of this behavior at an atomic-level is still deficient. Here we study vacancy diffusion processes across very large length-and time-scales using a combination of molecular dynamics and Monte Carlo simulations. We find that vacancies reduce their energy by residing at twin boundaries, kinks inside domain boundaries, and junctions between domain boundaries. Vacancies have the largest binding energy inside junctions and co-migrate with the motion of the junctions. For the weaker trapping inside twin boundaries, a "ghost line" may be generated because vacancies do not necessarily diffuse with moving boundaries and are left behind, leaving a trace of a previous position of the domain boundary. Needle twins act as channels for fast diffusion with almost one order of magnitude higher vacancy diffusivity than in bulk. The relative concentration of vacancies at twin boundaries (ρVa) is a function of the average vacancy concentration (CVa) with ρVa ~ CVa α and α = 0.61, in contrast to that of immobile vacancies case with α = 0.4. The concentration of vacancies at twin boundaries is enriched ca. 5 times at low temperatures. With increasing temperature, the enrichment drops as the trapping potential at the twin boundaries decreases (thermal release). The distribution of energydrop upon twin pattern evolution follows a power law. The exponent ε increases from ~1.44 to 2.0 when the vacancy concentration increases. The power law exponent is the same in the athermal region, while Vogel-Fulcher behavior is found at high temperatures.

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Section: Introductionmentioning

confidence: 99%

The interaction between vacancies and twin walls, junctions, and kinks, and their mechanical properties in ferroelastic materials

Ding

et al. 2019

Acta Materialia

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“…To enhance the damage tolerance of these nanocomponents, it is desirable to achieve fully reversible deformation exceeding the elastic strain limit, which is known as pseudoelasticity (see Supporting Information Figure S1). While shape memory effects originating from stress-induced martensitic phase transformation can exhibit a certain extent of pseudoelasticity, , this mechanism is no longer applicable to refined sample sizes of sub-100 nm. − Furthermore, the twinning/surface-mediated pseudoelastic behaviors of nanocrystals − ,,,− , are either limited to specific crystallographic orientations or lack controllability, making it challenging to control the pseudoelastic strain for various applications.…”

mentioning

confidence: 99%

Controllable Pseudoelasticity in Metallic Nanocrystals by Grain Boundary Engineering

Deng,

Chen,

Zhu

et al. 2024

Nano Lett.

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Materials with pseudoelasticity can recover from large strains exceeding their elastic limits during unloading, making them promising damage-tolerant building blocks for advanced nanodevices. Nevertheless, a practical approach to realize controllable pseudoelastic behavior at nanoscale remains challenging. Here, we proposed a grain boundary (GB) engineering approach to endow metallic nanocrystals with a controllable pseudoelasticity. Both in situ nanomechanical testing and atomistic simulations demonstrate that such controllable pseudoelasticity is governed by the extension and contraction of an inherent stacking fault array at the GB. By precisely tuning GB misorientation and inclination, our simulation results reveal that metallic nanocrystals can exhibit tailored pseudoelastic performance across a broad spectrum of GBs in different face-centered cubic metals. These findings enrich our understanding of the intrinsic pseudoelasticity of GBs and provide a GB engineering approach toward metallic materials with reversible deformability.

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“…Several studies have indicated that the superelastic response of SMA pillars has a strong size-dependence. − Ozdemir et al reported that the superelasticity of [110] Ni 54 Fe 19 Ga 27 shape memory alloy single crystal pillars start to diminish once the diameter of pillars D < ∼1 μm. It was suggested that the irreversible plastic deformation observed is due to the formation of stabilized martensites, even though there was no direct experimental evidence.…”

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confidence: 99%

Helium Nanobubbles Enhance Superelasticity and Retard Shear Localization in Small-Volume Shape Memory Alloy

et al. 2017

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The intriguing phenomenon of metal superelasticity relies on stress-induced martensitic transformation (SIMT), which is well-known to be governed by developing cooperative strain accommodation at multiple length scales. It is therefore scientifically interesting to see what happens when this natural length scale hierarchy is disrupted. One method is producing pillars that confine the sample volume to micrometer length scale. Here we apply yet another intervention, helium nanobubbles injection, which produces porosity on the order of several nanometers. While the pillar confinement suppresses superelasticity, we found the dispersion of 5-10 nm helium nanobubbles do the opposite of promoting superelasticity in a NiFeGa shape memory alloy. The role of helium nanobubbles in modulating the competition between ordinary dislocation slip plasticity and SIMT is discussed.

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Breakdown of Shape Memory Effect in Bent Cu–Al–Ni Nanopillars: When Twin Boundaries Become Stacking Faults

Cited by 11 publications

References 51 publications

The interaction between vacancies and twin walls, junctions, and kinks, and their mechanical properties in ferroelastic materials

The interaction between vacancies and twin walls, junctions, and kinks, and their mechanical properties in ferroelastic materials

Controllable Pseudoelasticity in Metallic Nanocrystals by Grain Boundary Engineering

Helium Nanobubbles Enhance Superelasticity and Retard Shear Localization in Small-Volume Shape Memory Alloy

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