Crossover from grain boundary sliding to rotational deformation in nanocrystalline materials

Gutkin, M. Yu.; Ovid’ko, I. A.; Скиба, Н. В.

doi:10.1016/s1359-6454(03)00226-x

Cited by 141 publications

(54 citation statements)

References 23 publications

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“…Thus, no mismatch in the striped patterns at the grain boundary between grain-A and grain-B and between grain-A and grain-BЈ can be observed. These results support the proporsed theory 36 of rotation mechanism with respect to a dipole of wedge disclinations, which occur on the grain boundaries, as shown in Fig. 7͑b͒, and we can presume that dislocations can climb more easily in a disordered region than in a well-ordered region.…”

Section: Intergranular Deformation In Nanocrystalline Metalssupporting

confidence: 88%

“…Therefore, accommodation mechanisms for misfits are required to obtain large elongation. One such mechanism would be a grain boundary diffusion creep mechanism 24 and another possibility is a grain rotation mechanism proposed by theoretical analyses 36,37 and observed in this simulation as shown below. Theoretical analyses show that a gliding grain boundary dislocation causing grain boundary sliding splits into climbing grain boundary dislocations at the triple junction, and then the grain rotation occurs through the motion of climbing grain boundary dislocations which compose a grain boundary disclination from a large-scale viewpoint, and this process is an energetically practical deformation mechanism in nanocrystalline materials ͑refer to Fig.…”

Section: Intergranular Deformation In Nanocrystalline Metalsmentioning

confidence: 77%

“…7͒. 36 Further, disclination dipoles are experimentally observed in body-centered-cubic iron that had undergone severe plastic deformation. 38 On the other hand, in our simulation, Fig.…”

Section: Intergranular Deformation In Nanocrystalline Metalsmentioning

confidence: 99%

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Grain-size dependence of the relationship between intergranular and intragranular deformation of nanocrystalline Al by molecular dynamics simulations

2005

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The strength of nanocrystalline aluminum has been studied using molecular dynamics simulation. Nanocrystalline models consisting of hexagonal grains with grain size d between 5 nm and 80 nm are deformed by the application of tension. A transition from grain-size hardening to grain-size softening can be observed in the region where d Ϸ 30 nm, which is the optimum grain size for strength. In the grain-size hardening region, nanocrystalline models primarily deform by intragranular deformation. Consequently, a pile-up of dislocations can be observed. When the grain size becomes less than 30 nm, where the thickness of the grain boundaries cannot be neglected in comparison to the grain sizes, the dominant deformation mechanism of nanocrystalline metals is intergranular deformation by grain boundary sliding. Further, geometrical misfits by grain boundary sliding are accommodated by the grain rotation mechanism. Moreover, cooperative grain boundary sliding occurs in the 5 nm model. The optimum grain size is controlled by the relationship between resistance to intergranular deformation by grain boundary processes and intragranular deformation resisted by the grain boundary. Therefore, the primary role of the grain boundary changes in the region where the optimum grain size is observed.

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Section: Intergranular Deformation In Nanocrystalline Metalssupporting

confidence: 88%

Section: Intergranular Deformation In Nanocrystalline Metalsmentioning

confidence: 77%

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Grain-size dependence of the relationship between intergranular and intragranular deformation of nanocrystalline Al by molecular dynamics simulations

2005

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“…Recently, rotational deformation occurring through motion of grain boundary disclination dipoles has been suggested as a deformation mechanism contributing to plastic flow in nanocrystalline materials [313][314][315][316]. Subsequently, there exists a cooperative action of grain boundary sliding and grain rotation during deformation.…”

Section: Mechanical Behaviormentioning

confidence: 99%

Nanocrystalline materials and coatings

Tjong

Chen

2004

Materials Science and Engineering: R: Reports

806

345

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In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of $0.1 to 0.3 mm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value ($10-20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall-Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process. #

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“…This has generated interest in the identification of deformation mechanism(s) acting in shear bands in NCMs, which potentially will allow one to influence the processes of plastic flow localization. In general, plastic and superplastic deformation mechanisms in NCMs are supposed to be lattice dislocation slip [1,2], grain boundary (GB) sliding [10][11][12][13][14], GB diffusional creep [3][4][5], triple junction diffusional creep [6], twinning [15] and rotational deformation mode [7][8][9][10], which compete with each other. In this paper, we will focus our consideration on ductile NCMs with comparatively large grains with size d 30 nm, in which the lattice dislocation slip is dominant.…”

Section: Introductionmentioning

confidence: 99%

Decay of low-angle tilt boundaries in deformed nanocrystalline materials

Bobylev¹,

Gutkin²,

Ovid’ko³

2003

J. Phys. D: Appl. Phys.

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A theoretical model is suggested, which describes a decay of low-angle grain boundaries in deformed nanocrystalline materials (NCMs). In the framework of the model, lattice dislocations that form a low-angle boundary are under the action of the forces owing to external (applied) and internal stresses. The balance of the forces causes the critical shear stress at which a low-angle boundary decays. Such decay processes result in the formation of high-density ensembles of mobile lattice dislocations that are capable of inducing plastic flow localization (shear banding) in mechanically loaded NCMs.

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Crossover from grain boundary sliding to rotational deformation in nanocrystalline materials

Cited by 141 publications

References 23 publications

Grain-size dependence of the relationship between intergranular and intragranular deformation of nanocrystalline Al by molecular dynamics simulations

Grain-size dependence of the relationship between intergranular and intragranular deformation of nanocrystalline Al by molecular dynamics simulations

Nanocrystalline materials and coatings

Decay of low-angle tilt boundaries in deformed nanocrystalline materials

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