Plastic anisotropy and associated deformation mechanisms in nanotwinned metals

You, Zhifeng; Li, Xiaoyan; Liu, Gui; Lu, Qian; Zhu, Ting; Gao, Huajian; Lü, Lei

doi:10.1016/j.actamat.2012.09.052

Cited by 293 publications

(173 citation statements)

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“…It has been the subject of intensive research due to its unusual combination of ultrahigh yield strength and high ductility [19][20][21]. The high ductility of nanotwinned Cu has been attributed to the gradual loss of coherency of the Twinning Boundaries (TB) during plastic deformation [22][23][24]. A brittle-to-ductile transition was experimentally observed in nanotwinned Cu despite Cu being an intrinsically ductile metal.…”

mentioning

confidence: 99%

Brittle versus ductile behaviour of nanotwinned copper: A molecular dynamics study

et al. 2015

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Nanotwinned copper (Cu) exhibits an unusual combination of ultra-high yield strength and high ductility. A brittle-to-ductile transition was previously experimentally observed in nanotwinned Cu despite Cu being an intrinsically ductile metal. However, the atomic mechanisms responsible for brittle fracture and ductile fracture in nanotwinned Cu are still not clear. In this study, molecular dynamics (MD) simulations at different temperatures have been performed to investigate the fracture behaviour of a nanotwinned Cu specimen with a single-edge-notched crack whose surface coincides with a twin boundary. Three temperature ranges are identified, indicative of distinct fracture regimes, under tensile straining perpendicular to the twin boundary. Below 1.1 K, the crack propagates in a brittle fashion. Between 2 K and 30 K a dynamic brittle-to-ductile transition is observed. Above 40 K the crack propagates in a ductile mode. A detailed analysis has been carried out to understand the atomic fracture mechanism in each fracture regime. Between 2 K and 30 K a dynamic brittle-to-ductile transition is observed. Above 40 K the crack propagates in a ductile mode. A detailed analysis has been carried out to understand the atomic fracture mechanism in each fracture regime.

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confidence: 99%

Brittle versus ductile behaviour of nanotwinned copper: A molecular dynamics study

et al. 2015

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“…First, GB-mediated dislocation emission is an important mechanism in the dependence of hardness and tensile strength on grain size in nanocrystalline metals, as well as in twindislocation interaction mechanisms controlling the plasticity and fracture of nanotwinned metals [12,45,46]. The present simulations have shown that voids could constitute the preferential sites for dislocation emission.…”

Section: Influence Of Nanovoids On Deformation Mechanismsmentioning

confidence: 86%

“…GB networks govern the plastic deformation of nanocrystalline and nanotwinned metals due to several GB-induced mechanisms [45]. In this study, particular focus is paid to the processes of GB-mediated dislocation emission in HABs and LABs, GB sliding in Σ9(221) GBs, and GB migration in Σ5(210) and Σ27(115) GBs.…”

Section: Deformation Mechanismsmentioning

confidence: 99%

“…However, recent experimental observations using a new nanodiffraction technique [18,19] have revealed that GBs in columnar-grained Cu obtained by DC magnetron sputtering have defective structures not yet accounted for in theoretical models. It is therefore imperative to understand the role of GB defects, such as nanovoids, on plastic deformation processes since the deformation of the GB network governs the overall plasticity of nanocrystalline and nanotwinned metals [45].…”

Section: Influence Of Nanovoids On Deformation Mechanismsmentioning

confidence: 99%

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Quasicontinuum study of the shear behavior of defective tilt grain boundaries in Cu

2014

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Atomistic simulations using the quasicontinuum method are used to study the role of vacancy defects and angström-scale voids on the mechanical behavior of five tilt bicrystals containing grain boundaries (GBs) that have been predicted to exhibit characteristic deformation processes of nanocrystalline and nanotwinned metals : GB-mediated dislocation emission, interface sliding, and shear-coupled GB migration. We demonstrate that such nanoscale defects have a profound impact on interfacial shear strength and underlying deformation mechanisms in copper GBs due to void-induced local stresses. In asymmetric high and low angle GBs, we find that voids become preferential sites for dislocation nucleation when the void size exceeds 4 Å. In symmetric Σ9(221) GBs prone to sliding, voids are shown to shield the local shear stress, which considerably reduces the extent of atom shuffling at the interface. In symmetric Σ5(210) and Σ27(115) GBs, we find that the effect of voids on shear-coupled GB migration depends on the GB tilt direction considered, as well as on the size and number of voids. Remarkably, large voids can completely abate the GB migration process in Σ27(115) GBs. For all GB types, the interfacial shear strength is shown to decrease linearly as the volume fraction of voids at the interface increases ; however, this study also suggests that this decrease is much more pronounced in GBs deforming by sliding than by dislocation nucleation or migration, owing to larger void-induced stresses.

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“…19 , 34 Meanwhile, TBs are sinks for dislocations, as revealed by accumulation of high-density dislocations in NT metals ( Figure 2 a ). 35 N. Li et al reported the pinning of mobile ITBs due to residual dislocations that were produced by transmission of glide dislocations across an ITB in Cu, 36 and the formation of steps at CTBs due to dislocation-CTB interactions ( Figure 2b ). 37 Bufford et al explored work hardening due to ITBs in NT Al ( Figure 2c ).…”

Section: Deformation In Nanotwinned Materialsmentioning

confidence: 99%