Tensile behavior of columnar grained Cu with preferentially oriented nanoscale twins

Pan, Qingsong; Lu, Qian; Lü, Lei

doi:10.1016/j.actamat.2011.07.044

Cited by 193 publications

(130 citation statements)

References 58 publications

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“…Most TBs appear rather straight without obvious evidence of defective structures. Similar materials have been synthesized in parallel by other groups albeit with clear variations in twin density and columnar grain size 14,20 . To obtain statistical misorientations of TBs and GBs, we carried out detailed IPFOM studies in TEM using the NanoMegas Astar system 21 (the pixellation effect of this technique can be seen in Supplementary Figs S1 and S2).…”

mentioning

confidence: 74%

“…GBs not only scatter electrons, but can migrate and slide under shear stresses 11 , leading to a maximum in strength in nanocrystalline materials 12,13 . In contrast, such migration/sliding mechanisms may not be operative in CTBs despite some reports of detwinning evidence 7,14,15 and the observation of a similar maximum strength in a nanotwinned copper 3 (nt-Cu). Existing models widely assume perfect CTBs and rationalize flow softening due to CTB migrations and detwinning as caused by nucleation and motion of partial dislocations parallel to CTBs (ref.…”

mentioning

confidence: 91%

“…This scenario is different from the detwinning process through partial dislocation glide proposed by modelling or from the detwinning caused by ITB motions observed in some experiments 17,31 . Nevertheless, the kink-motion proposition has strong implications to the detwinning phenomena observed so far experimentally (for example, detwinning remains active even at low temperatures and often occurs in certain regions) 7,14,15 , as well as a maximum strength seen in nt-Cu (ref.…”

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confidence: 99%

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Defective twin boundaries in nanotwinned metals

et al. 2013

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Coherent twin boundaries (CTBs) are widely described, both theoretically and experimentally, as perfect interfaces that play a significant role in a variety of materials. Although the ability of CTBs in strengthening, maintaining the ductility and minimizing the electron scattering is well documented [1][2][3] , most of our understanding of the origin of these properties relies on perfect-interface assumptions. Here we report experiments and simulations demonstrating that as-grown CTBs in nanotwinned copper are inherently defective with kink-like steps and curvature, and that these imperfections consist of incoherent segments and partial dislocations. We further show that these defects play a crucial role in the deformation mechanisms and mechanical behaviour of nanotwinned copper. Our findings offer a view of the structure of CTBs that is largely different from that in the literature 2,4,5 , and underscore the significance of imperfections in nanotwinstrengthened materials.CTBs formed during growth, deformation or annealing exist broadly in many crystalline solids with low or medium stackingfault energies 1,5,6 . The strengthening behaviour and other attractive properties of CTBs have been studied in nanotwinned metals (with an average twin spacing <100 nm; refs 7-9). One prevalent view is that CTB-strengthened materials have certain advantages over nanocrystalline or ultrafine-grained materials; that is, materials strengthened through traditional grain boundaries (GBs) that are considered incoherent and defective 10 . GBs not only scatter electrons, but can migrate and slide under shear stresses 11 , leading to a maximum in strength in nanocrystalline materials 12,13 . In contrast, such migration/sliding mechanisms may not be operative in CTBs despite some reports of detwinning evidence 7,14,15 and the observation of a similar maximum strength in a nanotwinned copper 3 (nt-Cu). Existing models widely assume perfect CTBs and rationalize flow softening due to CTB migrations and detwinning as caused by nucleation and motion of partial dislocations parallel to CTBs (ref. 4). These mechanisms are informative as long as CTB lengths are limited to the tens of nanometres typically used in molecular dynamics simulations 4,[16][17][18] . It still remains difficult through molecular dynamics simulations to validate the migrations/detwinning of the much longer CTBs seen in experiments (500 nm; ref. 3). There could be alternative mechanisms that are intricately related to the potential structures of CTBs and the characteristics of GBs, both of which are not accounted for in the literature.Recent studies of nanotwinned copper pillars without GBs revealed strong deformation anisotropy and a brittle-to-ductile transition behaviour (where CTBs are considered intrinsically brittle) 2 , suggesting that CTBs alone are not sufficient for increased plasticity despite their strong strengthening effect, and that a reasonable mix of GBs is helpful to mediate the plasticity and achieve high ductility. Experiments and simulations have f...

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Defective twin boundaries in nanotwinned metals

et al. 2013

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“…2b). 155 The plastic anisotropy of NT materials is not negligible at nanoscale due to the effect of spatial orientations of the nanotwins and the applied forces. Using magnetron sputtering deposition technique, Cu foils with preferred orientation of growth twins are successfully synthesized, 48 providing an alternative for the synthesis of ultrahigh-strength, ductile pure metals via the control of twin spacing and twin orientation (Fig.…”

Section: -151mentioning

confidence: 99%

Nanotwinned and hierarchical nanotwinned metals: a review of experimental, computational and theoretical efforts

Sun

2018

npj Comput Mater

134

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The recent studies on nanotwinned (NT) and hierarchical nanotwinned (HNT) face-centered cubic (FCC) metals are presented in this review. The HNT structures have been supposed as a kind of novel structure to bring about higher strength/ductility than NT counterparts in crystalline materials. We primarily focus on the recent developments of the experimental, atomistic and theoretical studies on the NT and HNT structures in the metallic materials. Some advanced bottom-up and top-down techniques for the fabrication of NT and HNT structures are introduced. The deformation induced HNT structures are available by virtue of severe plastic deformation (SPD) based techniques while the synthesis of growth HNT structures is so far almost unavailable. In addition, some representative molecular dynamics (MD) studies on the NT and HNT FCC metals unveil that the nanoscale effects such as twin spacing, grain size and plastic anisotropy greatly alter the performance of NT and HNT metals. The HNT structures may initiate unique phenomena in comparison with the NT ones. Furthermore, based on the phenomena and mechanisms revealed by experimental and MD simulation observations, a series of theoretical models have been proposed. They are effective to describe the mechanical behaviors of NT and HNT metals within the applicable scope. So far the development of manufacturing technologies of HNT structures, as well as the studies on the effects of HNT structures on the properties of metals are still in its infancy. Further exploration is required to promote the design of advanced materials.

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“…including bimodal grain size distributions [1,2], nanoscale twins [3,4], and grain size gradients [5]. Specifically, gradient microstructures generated through surface mechanical attrition treatments or SMAT have additional benefits over other hierarchical microstructures from a surface science/tribological standpoint by concentrating the nanocrystalline properties in the surface region.…”

Section: Open Accessmentioning

confidence: 99%

Mechanical Behavior of Ultrafine Gradient Grain Structures Produced via Ambient and Cryogenic Surface Mechanical Attrition Treatment in Iron

Murdoch

Darling

Roberts

et al. 2015

Metals

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Ambient and cryogenic surface mechanical attrition treatments (SMAT) are applied to bcc iron plate. Both processes result in significant surface grain refinement down to the ultrafine-grained regime; the cryogenic treatment results in a 45% greater grain size reduction. However, the refined region is shallower in the cryogenic SMAT process. The tensile ductility of the grain size gradient remains low (<10%), in line with the expected behavior of the refined surface grains. Good tensile ductility in a grain size gradient requires the continuation of the gradient into an undeformed region.

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Tensile behavior of columnar grained Cu with preferentially oriented nanoscale twins

Cited by 193 publications

References 58 publications

Defective twin boundaries in nanotwinned metals

Defective twin boundaries in nanotwinned metals

Nanotwinned and hierarchical nanotwinned metals: a review of experimental, computational and theoretical efforts

Mechanical Behavior of Ultrafine Gradient Grain Structures Produced via Ambient and Cryogenic Surface Mechanical Attrition Treatment in Iron

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