Free volume in nanostructured Ni

Petegem, S. Van; Torre, F. Dalla; Segers, D.; Swygenhoven, H. Van

doi:10.1016/s1359-6462(02)00322-6

Cited by 87 publications

(47 citation statements)

References 17 publications

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“…2, where 1 (150-200 ps), 2 (400-450 ps), and 3 (2000-2500 ps) are the peaks of positron lifetime. These positron lifetime peaks correspond to the occurrence of positron annihilation at one-atom-sized (or smaller) vacancies, at vacancy clusters, and at nanosized voids, 32,33) respectively. In the present paper, the intensities of 1 , 2 , and 3 are denoted I 1 , I 2 , and I 3 , respectively.…”

Section: Microstructuresmentioning

confidence: 99%

“…Note that the I 1 of specimen B was about twice as strong as that of specimen A, where I 1 is the intensity of one-atom or smallersized vacancies. It is known from an experiment 33) and a MD simulation 21) that vacancies exist in grain boundaries in nanocrystalline metals. The point defect formation energy in the grain boundary is lower than that in the lattice because vacancies are more stable in the grain boundary than in the lattice.…”

Section: Microstructuresmentioning

confidence: 99%

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Effects of Vacancies on Deformation Behavior in Nanocrystalline Nickel

et al. 2008

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The effects of vacancies on deformation of nanocrystalline Ni have been investigated by experiments and molecular dynamics (MD) simulations. In the experiments, nanocrystalline Ni specimens containing different numbers of vacancies were produced by electrodeposition and annealing, and their mechanical properties were investigated by tensile tests. As a result, the yield stress and fracture stress for the specimen containing more vacancies were lower than those for the one containing fewer vacancies. The MD simulations showed that the grain boundary energy is increased by the presence of vacancies in the grain boundary, however, that an increase in grain boundary energy with straining is reduced by the presence of vacancies in the grain boundary. The results of the experiments and simulations suggested that there is a correlation between the grain boundary energy characteristics and the mechanical properties of the nanocrystalline Ni.

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Section: Microstructuresmentioning

confidence: 99%

Section: Microstructuresmentioning

confidence: 99%

Effects of Vacancies on Deformation Behavior in Nanocrystalline Nickel

et al. 2008

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“…[10,11,[50][51][52][53] The typical grain structure of such materials may vary from columnar to equiaxed, but in none of the articles cited above is there a high density of growth twins in pure nanocrystalline Ni. The Ni-rich alloys plated in this work offer a striking contrast to this picture.…”

Section: A Ni-rich Depositsmentioning

confidence: 99%

Nanostructured Ni-Co alloys with tailorable grain size and twin density

Ferreira

Schuh

2005

Metall Mater Trans A

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We present an experimental approach to systematically produce nanostructures with various grain sizes and twin densities in the Ni-Co binary system. Using electrodeposition with various applied current densities and organic additive contents in the deposition bath, we synthesize nanostructured fcc and hcp solid solutions with a range of compositions. Due to the low stacking fault energy (SFE) of these alloys, growth twins are readily formed during deposition, and by adjusting the deposition conditions, a range of twin boundary densities is possible. The resulting nanostructured alloys cannot be described by a single characteristic length scale, but instead must be characterized in terms of (1) a true grain size pertaining to general high-angle grain boundaries and (2) an effective grain size that incorporates twin boundaries. Analysis of Hall-Petch strength scaling for these materials is complicated by their dual length scales, but the hardness trends found in Ni-80Co are found to be roughly in line with those seen in pure nanocrystalline nickel.

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“…According to the Taylor law, which links the dislocation density in a metal to its flow stress, therefore, diffusion kinetics can be accelerated by increased flow stresses. Meanwhile, plastic deformation may induce vacancies and increase the mobile vacancy concentration [23][24][25]. The increased vacancy concentrations by SPD may lead to pronounced enhancement of diffusion kinetics [24,25].…”

Section: Introductionmentioning

confidence: 99%

Microstructural evolution and formation of nanocrystalline intermetallic compound during surface mechanical attrition treatment of cobalt

Tao

Wei

et al. 2007

Acta Materialia

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Nanocrystalline intermetallic Co 3 Fe 7 was produced on the surface of cobalt via surface mechanical attrition (SMA). Deformationinduced diffusion entailed the formation of a series of solid solutions. Phase transitions occurred depending on the atomic fraction of Fe in the surface solid solutions: from hexagonal close-packed (<4% Fe) to face-centered cubic (fcc) (4-11% Fe), and from fcc to body-centered cubic (>11% Fe). Nanoscale compositional probing suggested significantly higher Fe contents at grain boundaries and triple junctions than grain interiors. Short-circuit diffusion along grain boundaries and triple junctions dominate in the nanocrystalline intermetallic compound. Stacking faults contribute significantly to diffusion. Diffusion enhancement due to high-rate deformation in SMA was analyzed by regarding dislocations as solute-pumping channels, and the creation of excess vacancies. Non-equilibrium, atomic level alloying can then be ascribed to deformation-induced intermixing of constituent species. The formation mechanism of nanocrystalline intermetallic grains on the SMA surface can be thought of as a consequence of numerous nucleation events and limited growth.

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Free volume in nanostructured Ni

Cited by 87 publications

References 17 publications

Effects of Vacancies on Deformation Behavior in Nanocrystalline Nickel

Effects of Vacancies on Deformation Behavior in Nanocrystalline Nickel

Nanostructured Ni-Co alloys with tailorable grain size and twin density

Microstructural evolution and formation of nanocrystalline intermetallic compound during surface mechanical attrition treatment of cobalt

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