Molecular dynamics simulation of twin boundary effect on deformation of Cu nanopillars

Sainath, G.; Choudhary, B.K.

doi:10.1016/j.physleta.2015.05.027

Cited by 45 publications

(29 citation statements)

References 22 publications

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“…Most of these studies were focused on perfect nanowires, and it is not clear whether the deformation by twinning will continue to occur in the presence of defects such as dislocations and grain boundaries. Recently, it has been shown that the presence of twin boundary in <110> FCC Cu nanopillars changes the deformation mechanism from twinning to slip [19]. In the present study, an attempt has been made to understand the influence of twist boundary on deformation twinning in BCC Fe nanowires.…”

Section: Introductionmentioning

confidence: 92%

Influence of twist boundary on deformation behaviour of 〈1 0 0〉 BCC Fe nanowires

Sainath

Choudhary

2016

Philosophical Magazine Letters

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Molecular dynamics simulations revealed significant difference in deformation behaviour of <100>BCC Fe nanowires with and without twist boundary. The plastic deformation in perfect <100> BCC Fe nanowire was dominated by twinning and reorientation to <110> followed by further deformation by slip mode. On the contrary, <100> BCC Fe nanowire with a twist boundary deformed by slip at low plastic strains followed by twinning at high strains and absence of full reorientation. The results suggest that the deformation in <100> BCC Fe nanowire by dislocation slip is preferred over twinning in the presence of initial dislocations or dislocation networks. The results also explain the absence of extensive twinning in bulk materials, which inherently contains large number of dislocations.

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Section: Introductionmentioning

confidence: 92%

Influence of twist boundary on deformation behaviour of 〈1 0 0〉 BCC Fe nanowires

Sainath

Choudhary

2016

Philosophical Magazine Letters

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“…The superior mechanical properties of twinned nanopillars have been attributed to unique deformation mechanisms operating in the presence of twin boundaries [11]. In view of this, the materials containing high density of twin boundaries attract huge interest among materials scientists and engineers.Several experimental and molecular dynamics (MD) simulation studies have been performed to understand the influence of twin boundaries on the strength and deformation behaviour in FCC nanopillars/nanowires [12][13][14][15][16].Using MD simulations, Cao et al [12] have shown that in FCC nanopillars, the twin boundaries serve as the strong obstacles for dislocations motion. As a result, the decrease in twin boundary spacing increases the yield strength in orthogonally twinned Cu nanopillars.…”

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confidence: 99%

“…Further, the strengthening in twinned FCC nanopillars also depends on the size and aspect ratio [14]. In addition to orthogonally twinned FCC nanopillars, the increase in yield stress is also observed in slanted and vertically twinned FCC nanopillars [15,16].Using molecular dynamics simulations and in situ experiments, the deformation mechanisms responsible for superior properties and the associated dislocation-twin boundary interactions have been characterised in FCC nanopillars.Most of the studies reported in the literature have been performed on twinned FCC nanopillars and little attention has been paid to characterise the mechanical behaviour of twinned BCC nanowires/nanopillars. It is well known that the twin boundaries in FCC system coincide with {111} planes, while in BCC systems they coincide with {112} planes [17].…”

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confidence: 99%

Deformation behaviour of body centered cubic iron nanopillars containing coherent twin boundaries

Sainath¹,

Choudhary²

2016

Philosophical Magazine

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Molecular dynamics simulations were performed to understand the role of twin boundaries on deformation behaviour of body-centred cubic (BCC) iron (Fe) nanopillars. The twin boundaries varying from one to five providing twin boundary spacing in the range 8.5 -2.8 nm were introduced perpendicular to the loading direction. The simulation results indicated that the twin boundaries in BCC Fe play a contrasting role during deformation under tensile and compressive loadings. During tensile deformation, a large reduction in yield stress was observed in twinned nanopillars compared to perfect nanopillar. However, the yield stress exhibited only marginal variation with respect to twin boundary spacing. On the contrary, a decrease in yield stress with increase in twin boundary spacing was obtained during compressive deformation. This contrasting behaviour originates from difference in operating mechanisms during yielding and subsequent plastic deformation. It has been observed that the deformation under tensile loading was dominated mainly by twin growth mechanism, due to which the twin boundaries offers a negligible resistance to slip of twinning partials. This is reflected in the negligible variation of yield stress as a function of twin boundary spacing. On the other hand, the deformation was dominated by nucleation and slip of full dislocations under compressive loading. The twin boundaries offer a strong repulsive force on full dislocations resulting in the yield stress dependence on twin boundary spacing. Further, it has been observed that the curved twin boundary can acts as a source for full dislocation. The occurrence of twin-twin interaction during tensile deformation and dislocation-twin interaction during compressive deformation were presented and discussed.In recent years, the twinned nanopillars or nanowires have drawn growing attention in view of their superior physical properties and potential applications in modern small-scale electronic devices such as nano/micro electro mechanical systems. The twinned nanopillars contain a series of twin boundaries with specified spacing between the boundaries. Twin boundary possesses high symmetry and lowest interface energy along with well-defined boundary plane. The low energy of twin boundaries results in a number of superior properties over conventional grain boundaries. For example, it has been found that the twin boundaries enhance the strength without loss of ductility [1-3], improve fracture toughness and crack resistance [4][5][6], and increase corrosion resistance and strain rate sensitivity [7]. Moreover, the twin boundaries possess high thermal and mechanical stability [8,9] and high electrical conductivity [10]. The superior mechanical properties of twinned nanopillars have been attributed to unique deformation mechanisms operating in the presence of twin boundaries [11]. In view of this, the materials containing high density of twin boundaries attract huge interest among materials scientists and engineers.Several experimental and molecular dynamics (MD) sim...

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“…However, the influence of twin boundary spacing has not been investigated when the twin boundaries are parallel to the loading direction. Although, under tensile loading, it has been shown that the introduction of longitudinal twin boundary increases the strength of the nanowire compared to its perfect counterpart [13], but the influence of twin boundary spacing is still elusive. Further in twinned nanopillars, the dislocation interactions with twin boundaries needs to be investigated in greater detail.…”

Section: Introductionmentioning

confidence: 99%

Role of axial twin boundaries on deformation mechanisms in Cu nanopillars

Rohith

Sainath

Goyal

et al. 2019

Philosophical Magazine

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In recent years, twinned nanopillars have attracted tremendous attention for research due to their superior mechanical properties. However, most of the studies were focused on nanopillars with twin boundaries (TBs) perpendicular to loading direction. Nanopillars with TBs parallel to loading direction have received minimal interest. In this backdrop, the present study is aimed at understanding the role of axial TBs on strength and deformation behaviour of Cu nanopillars using atomistic simulations. Tensile and compression tests have been performed on <112> nanopillars with and without TBs. Twinned nanopillars with twin boundary spacing in the range 1.6-5 nm were considered. The results indicate that, under both tension and compression, yield strength increases with decreasing twin boundary spacing and is always higher than that of perfect nanopillars. Under compression, the deformation in <112> perfect as well as twinned nanopillars proceeds by the slip of extended dislocations. In twinned nanopillars, an extensive cross-slip by way of Friedel-Escaig and Fleischer mechanisms has been observed in compression. On the other hand, under tensile loading, the deformation in perfect nanopillars occurs by partial slip/twinning, while in twinned nanopillars, it proceeds by the slip of extended dislocations. This extended dislocation activity is facilitated by stair-rod formation and its dissociation on the twin boundary. Similar to compressive loading, the extended dislocations under tensile loading also exhibit cross-slip activity in twinned nanopillars. However, this cross-slip activity occurs only through Fleischer mechanism and no Friedel-Escaig mechanism of cross-slip has been observed under tensile loading.

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Molecular dynamics simulation of twin boundary effect on deformation of Cu nanopillars

Cited by 45 publications

References 22 publications

Influence of twist boundary on deformation behaviour of 〈1 0 0〉 BCC Fe nanowires

Influence of twist boundary on deformation behaviour of 〈1 0 0〉 BCC Fe nanowires

Deformation behaviour of body centered cubic iron nanopillars containing coherent twin boundaries

Role of axial twin boundaries on deformation mechanisms in Cu nanopillars

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