Molecular dynamics simulation studies on the size dependent tensile deformation and fracture behaviour of body centred cubic iron nanowires

Sainath, G.; Choudhary, B.K.; Jayakumar, T.

doi:10.1016/j.commatsci.2015.03.053

Cited by 78 publications

(57 citation statements)

References 55 publications

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“…The activation of multiple slip systems satisfying the von-Mises criterion even at 10 K in <110> BCC Fe nanowires lead to gross plastic deformation and high ductility 19 . In <100> BCC Fe nanowire, different deformation mechanisms of twinning and reorientation at 10 K results in high ductility 14 . Apart from orientation, the nanowire size and shape also play an important role on the deformation mechanisms.…”

Section: B Ductile-brittle Transitionmentioning

confidence: 99%

“…These mechanisms cannot be observed when the nanowires deform by the dislocation slip. The reorientation mechanism observed in BCC Fe nanowires exhibits a strong size and temperature dependence 14,16 . It has been shown that the deformation by twinning leads to reorientation in nanowires of cross section width less than 11.42 nm.…”

Section: Introductionmentioning

confidence: 99%

“…It has been shown that the deformation by twinning leads to reorientation in nanowires of cross section width less than 11.42 nm. Beyond this size even though nanowires still deform by the twinning mechanism, the reorientation mechanism ceases to operate due to twin-twin interactions 14 . In addition to twinning, BCC Fe nanowires also exhibit peculiar dislocation behavior with respect to nanowire size, temperature, and strain rate.…”

Section: Introductionmentioning

confidence: 99%

“…Most of these studies in BCC metallic nanowires have been focused mainly on deformation aspects such as twinning and dislocation behavior [8][9][10][11][12][13][14][15][16][17][18][19][20] . It is surprising that enough attention has not been paid towards the fracture behavior of BCC Fe nanowires.…”

Section: Introductionmentioning

confidence: 99%

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Atomistic simulations on ductile-brittle transition in ⟨111⟩ BCC Fe nanowires

Sainath

Choudhary

2017

Journal of Applied Physics

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Molecular dynamics simulations have been performed to understand the influence of temperature on the tensile deformation and fracture behavior of <111> BCC Fe nanowires. The simulations have been carried out at different temperatures in the range 10-1000 K employing a constant strain rate of 1× 10 8 s −1 . The results indicate that at low temperatures (10-375 K), the nanowires yield through the nucleation of a sharp crack and fails in brittle manner. On the other hand, nucleation of multiple 1/2<111> dislocations at yielding followed by significant plastic deformation leading to ductile failure has been observed at high temperatures in the range 450-1000 K. At the intermediate temperature of 400 K, the nanowire yields through nucleation of crack associated with many mobile 1/2<111> and immobile <100> dislocations at the crack tip and fails in ductile manner. The ductile-brittle transition observed in <111> BCC Fe nanowires is appropriately reflected in the stress-strain behavior and plastic strain at failure. The ductile-brittle transition increases with increasing nanowire size. The change in fracture behavior has been discussed in terms of the relative variations in yield and fracture stresses and change in slip behavior with respect to temperature. Further, the dislocation multiplication mechanism assisted by the kink nucleation from the nanowire surface observed at high temperatures has been presented.

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Section: B Ductile-brittle Transitionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Atomistic simulations on ductile-brittle transition in ⟨111⟩ BCC Fe nanowires

Sainath

Choudhary

2017

Journal of Applied Physics

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“…Owing to their unique physical, chemical, and mechanical properties, the chemically reactive iron element 1,2 and its oxide nanostructure compounds are widely used as most promising materials for diverse nanoscale technological applications, such as heterogeneous photo catalysts/catalysis, 3,4 magnetic recording media, [5][6][7] hydrogen storage, 4 field emission devices, 8 water splitting, 8,9 chemical, gas, and bio sensors, 6,10-12 permanent magnets, 6 biomedical applications, 5,13,14 and solar cells. 9,11 In ambient environment conditions, even at room temperature, spontaneous oxidations of metallic Fe nanowires (NWs) exhibit rather complex phenomena when in contact with oxidizing agents, such as oxygen and/or water.…”

Section: Introductionmentioning

confidence: 99%

Effects of oxidation on tensile deformation of iron nanowires: Insights from reactive molecular dynamics simulations

Aral

Wang

Ogata

et al. 2016

Journal of Applied Physics

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The influence of oxidation on the mechanical properties of nanostructured metals is rarely explored and remains poorly understood. To address this knowledge gap, in this work, we systematically investigate the mechanical properties and changes in the metallic iron (Fe) nanowires (NWs) under various atmospheric conditions of ambient dry O 2 and in a vacuum. More specifically, we focus on the effect of oxide shell layer thickness over Fe NW surfaces at room temperature. We use molecular dynamics (MD) simulations with the variable charge ReaxFF force field potential model that dynamically handles charge variation among atoms as well as breaking and forming of the chemical bonds associated with the oxidation reaction. The ReaxFF potential model allows us to study large length scale mechanical atomistic deformation processes under the tensile strain deformation process, coupled with quantum mechanically accurate descriptions of chemical reactions. To study the influence of an oxide layer, three oxide shell layer thicknesses of $4.81 Å , $5.33 Å , and $6.57 Å are formed on the pure Fe NW free surfaces. It is observed that the increase in the oxide layer thickness on the Fe NW surface reduces both the yield stress and the critical strain. We further note that the tensile mechanical deformation behaviors of Fe NWs are dependent on the presence of surface oxidation, which lowers the onset of plastic deformation. Our MD simulations show that twinning is of significant importance in the mechanical behavior of the pure and oxide-coated Fe NWs; however, twin nucleation occurs at a lower strain level when Fe NWs are coated with thicker oxide layers. The increase in the oxide shell layer thickness also reduces the external stress required to initiate plastic deformation. Published by AIP Publishing.

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Interface Driven Pseudo‐Elasticity in a‐Fe Nanowires

Yang

Ding

et al. 2015

Adv Funct Materials

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wileyonlinelibrary.comwill specify exactly the conditions under which the formation of nanostructures is reversible after bending the nanowire.Reversibility is typically related to the shape memory effect and pseudo-elasticity in shape memory alloys (SMAs). [5][6][7] The shape recovery is achieved by thermoelastic martensitic phase transformations and domain switching. The driving force for the shape recovery arises from the free energy difference between the martensite and parent phase. This effect is strongly size-dependent and it is not obvious how SMAs operate in thin wires. [ 8,9 ] The fundamental question is whether a different shape memory effect exists at the nanoscale and if so by which mechanism. This is important because many traditional SMAs fail under nanoscale bending and it becomes important to search for alternative functional materials to replace the traditional SMAs for such nanoscale applications. We show by molecular dynamics simulations that α-Fe, which is not a shape memory alloy, also shows shape recovery (or pseudo-elasticity) after bending. Large bending in α-Fe occurs via the formation of interfaces between domains of different orientation and twinning. The deformed nanowire completely recovers under unloading. The mechanism is shown to be very different from the classic pseudo-elasticity, and is related to high-energy interfaces in the nanowire and not the martensite-austenite phase transformation. This result has implications more widely for shape-dependent SMAs that are used in microelectromechanical systems (MEMS) technology. This is also an example of the emerging fi eld of domain boundary engineering where functionality (namely the shape recovery) is linked to domain boundaries and interfaces, but not to bulk properties (such as the martensite-austenite phase transformation). [10][11][12] Previous molecular dynamics (MD) simulations have identifi ed a class of metallic nanowires with both face-centered cubic (fcc) and body-centered cubic (bcc) structures that show pseudo-elasticity and shape memory effects. [13][14][15][16][17][18][19] This pseudoelastic behavior was achieved under uniaxial tension while little is known whether such unique behavior can still exist when a wire is bent. Under tension, the shape recovery relates to the reversibility of conventional twinning. The driving force for the recoverable deformation stems from the minimization of the surface energy. [ 14,15,17,18 ] The total recoverable strain is very large and can exceed 40%. A large inelastic deformation mediated by conventional twinning has been confi rmed experimentally in fcc palladium and bcc tungsten. [ 20,21 ] Here we also show that the shape recovery effect under bending in α -Fe relates to the formation of nonconventional interfaces between domains of different orientations. Unlike conventional <111>/{112}-type Interface Driven Pseudo-Elasticity in α-Fe Nanowires Yang Yang , Suzhi Li , * Xiangdong Ding , * Jun Sun , and Ekhard K. H. Salje * Molecular dynamics simulations of bent [100] α-Fe nanowires...

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Molecular dynamics simulation studies on the size dependent tensile deformation and fracture behaviour of body centred cubic iron nanowires

Cited by 78 publications

References 55 publications

Atomistic simulations on ductile-brittle transition in ⟨111⟩ BCC Fe nanowires

Atomistic simulations on ductile-brittle transition in ⟨111⟩ BCC Fe nanowires

Effects of oxidation on tensile deformation of iron nanowires: Insights from reactive molecular dynamics simulations

Interface Driven Pseudo‐Elasticity in a‐Fe Nanowires

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