Low-temperature superplasticity in nanostructured nickel and metal alloys

McFadden, S. X.; Mishra, Rajiv S.; Valiev, Ruslan Z.; Zhilyaev, Alexander P.; Mukherjee, Amiya K.

doi:10.1038/19486

Cited by 596 publications

(283 citation statements)

References 11 publications

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“…Such near-perfect elastoplasticity in tension is quite unusual and has only been observed in pure nanocrystalline copper (5) when deformed at the extremely slow strain rate of 5 ϫ 10 Ϫ6 s Ϫ1 . The physical mechanism of this behavior in the pure nanocrystalline copper was related to a grain boundary (GB) sliding mechanism (7), which often leads to a drop of the flow stress (7,26). The high flow stress (ϳ1.09 GPa) and the nearperfectly plastic flow behavior observed in our samples at room temperature and at a much higher strain rate of 10 Ϫ4 s Ϫ1 are inconsistent with the observations in pure nanocrystalline materials, indicating an alternative deformation mechanism.…”

contrasting

confidence: 55%

Ductile crystalline–amorphous nanolaminates

Wang

Hamza

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

437

222

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It is known that the room-temperature plastic deformation of bulk metallic glasses is compromised by strain softening and shear localization, resulting in near-zero tensile ductility. The incorporation of metallic glasses into engineering materials, therefore, is often accompanied by complete brittleness or an apparent loss of useful tensile ductility. Here we report the observation of an exceptional tensile ductility in crystalline copper/copper-zirconium glass nanolaminates. These nanocrystalline-amorphous nanolaminates exhibit a high flow stress of 1.09 ؎ 0.02 GPa, a nearly elastic-perfectly plastic behavior without necking, and a tensile elongation to failure of 13.8 ؎ 1.7%, which is six to eight times higher than that typically observed in conventional crystallinecrystalline nanolaminates (<2%) and most other nanocrystalline materials. Transmission electron microscopy and atomistic simulations demonstrate that shear banding instability no longer afflicts the 5-to 10-nm-thick nanolaminate glassy layers during tensile deformation, which also act as high-capacity sinks for dislocations, enabling absorption of free volume and free energy transported by the dislocations; the amorphous-crystal interfaces exhibit unique inelastic shear (slip) transfer characteristics, fundamentally different from those of grain boundaries. Nanoscale metallic glass layers therefore may offer great benefits in engineering the plasticity of crystalline materials and opening new avenues for improving their strength and ductility.metallic glass ͉ size-dependent plasticity ͉ nanocrystalline materials ͉ amorphous-crystalline interface ͉ tensile ductility A traditional strategy to develop ultrahigh-strength crystalline materials is to limit or inhibit the motion of dislocations required for plastic deformation (1-3) so that a higher applied stress is necessary. Examples of such advanced materials include thin films (4), nanocrystalline metals (5-7), and nanolaminates (8-10). As dislocation motion in high-strength crystalline materials becomes increasingly difficult (11), the ductility, i.e., the ability of a material to change shape without catastrophic failure, is often reduced dramatically (6, 7). In bulk metallic glasses, plastic deformation is not enabled by dislocations (12-21) but rather by clusters of atoms that undergo cooperative shear displacements [shear transformation zones (STZs)] (16); in the extreme limit of homogeneous-toinhomogeneous flow transition, shear bands of nanoscale width form (17,(19)(20)(21). The formation of such shear bands causes large strain softening and abrupt rupture of the metallic glasses. By way of contrast, large compressive plastic strains have been obtained in several bulk metallic glasses (12)(13)(14). Nonetheless, they show nearzero macroscopic ductility when subjected to tensile loading. To our knowledge, there is no experimental evidence currently suggesting that macroscopic metallic glass samples can sustain large tensile plasticity. An interesting question arises whether shear banding remains...

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contrasting

confidence: 55%

Ductile crystalline–amorphous nanolaminates

Wang

Hamza

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

437

222

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“…First, it is necessary to measure the mean grain size, the distribution of grain sizes, the distribution of the grain boundary misorientations and the texture of the asprocessed material. Second, it is important also to examine the thermostability of the UFG microstructure since, if the ultrafine grains are reasonably stable at elevated temperatures, there is a potential for achieving superplastic ductilities at both unusually low testing temperatures and exceptionally rapid strain rates [16]. Despite the fact that an increase in strength is generally associated with a loss in ductility in testing at ambient and low temperatures, recent experiments demonstrated that SPD processing, when taken to a sufficiently high strain, is capable of producing materials exhibiting extraordinary combinations of both high strength and high ductility [17].…”

Section: Introductionmentioning

confidence: 99%

The microstructural characteristics of ultrafine-grained nickel

Zhilyaev

Kim

Szpunar

et al. 2005

Materials Science and Engineering: A

198

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“…1 Similarly, metallic nanowires can have unusual physical properties, such as quantized electron, photon, and phonon transport. [2][3][4][5][6] Enhanced strength, plasticity, and hardness were also observed for nanocrystalline metals as a result of limited dislocation mobility 1,[7][8][9][10][11] . While other deformation mechanisms, such as desclination activity 12 may participate at high deformation rates, diffusion-controlled grain boundary sliding [13][14][15] is likely to be the dominant deformation mechanism for nanosized grain materials.…”

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confidence: 99%

Co-continuous Metal−Ceramic Nanocomposites

2005

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A room temperature technique was developed to produce continuous metal nanowires embedded in random nanoporous ceramic skeletons. The synthesis involves preparation of uniform, nanoporous ceramic preforms, and subsequent electrochemical metal infiltration at room temperature, so to avoid materials incompatibilities frequently encountered in traditional high temperature liquid metal infiltration. Structure and preliminary evaluations of mechanical and electronic properties of copper/alumina nanocomposites are reported.Keywords: Metal/ceramic nanocomposite, Cu, porous Al 2 O 3 , electrochemical infiltration. * Corresponding author. Email: xfzhang@lbl.gov 2 Nanograin ceramics have been reported to exhibit dramatically increased strength, hardness, and superplasticity. 1 Similarly, metallic nanowires can have unusual physical properties, such as quantized electron, photon, and phonon transport. [2][3][4][5][6] Enhanced strength, plasticity, and hardness were also observed for nanocrystalline metals as a result of limited dislocation mobility 1,[7][8][9][10][11] . While other deformation mechanisms, such as desclination activity 12 may participate at high deformation rates, diffusion-controlled grain boundary sliding 13-15 is likely to be the dominant deformation mechanism for nanosized grain materials. It was also reported that scale effects are significant factors in determining strength and plasticity of metals, alloys, and superalloys for sizes up to as much as several micrometers. 16 When co-continuous metal/ceramic composites are created in which both the metallic and the ceramic components are of nanoscale size, the nature of the high interface/volume ratio and synergy of the combined physical properties may lead to a novel class of structural or functional materials.To avoid materials incompatibilities associated with the elevated temperatures required for molten metal infiltration, room temperature electrochemical infiltration of porous ceramic preforms has been considered. [17][18] Most published results have been for metal electrochemical infiltration of either submicron porous matrices 18 or micrometer thin anodized Al 2 O 3 membranes with one-dimensional nanopore channels . 6,17,[19][20] The present paper describes a method in which a nanograin ceramic compact is first produced with homogeneous nanoporosity, and subsequently filled with a continuous metallic nanowire network by room temperature electrochemical infiltration.Nanoporous alumina matrices (10 mm diameter and 1 mm thick, 40% porosity) were made by compacting and free sintering 20 nm γ-Al 2 O 3 nanopowder. The samples were placed in a holder, and electrochemical infiltration of Cu into the interconnected nanopore channels was done in a 0.2M CuSO 4 + 2M H 2 SO 4 + deionized water electroplating bath, with a Cu anode and the sample/Cu cathode 1.5 cm apart. Optimization of combined d.c. and a.c. currents was essential for efficient infiltration. The infiltrated samples were dried, and post-annealed at 500 o C in a He/4% H 2 atmosphere. The...

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Low-temperature superplasticity in nanostructured nickel and metal alloys

Cited by 596 publications

References 11 publications

Ductile crystalline–amorphous nanolaminates

Ductile crystalline–amorphous nanolaminates

The microstructural characteristics of ultrafine-grained nickel

Co-continuous Metal−Ceramic Nanocomposites

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