Grain boundary diffusion characteristics of nanostructured nickel

Kolobov, Yu. R.; Grabovetskaya, G. P.; Иванов, М. Б.; Zhilyaev, Alexander P.; Valiev, Ruslan Z.

doi:10.1016/s1359-6462(00)00699-0

Cited by 268 publications

(225 citation statements)

References 8 publications

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“…This disagreement may be associated with the nonequilibrium grain boundary structure; there are reports of "anomalous" diffusion in nanocrystalline materials due to presumed nonequilibrated grain boundaries exhibiting diffusion properties more like a free surface. [43][44][45] The activation energy for surface selfdiffusion on a (111) plane in Ni is 60 kJ/mol, 46 which is reasonably close to what we measure in Fig. 3.…”

Section: A Linear Hardening Regimesupporting

confidence: 85%

Grain boundary relaxation strengthening of nanocrystalline Ni–W alloys

2012

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The hardening effect caused by the relaxation of nonequilibrium grain boundary structure has been explored in nanocrystalline Ni-W alloys. First, the kinetics of relaxation hardening are studied, showing that higher annealing temperatures result in faster, more pronounced strengthening. Based on the temperature dependence of relaxation strengthening kinetics, triple junction diffusion is suggested as a plausible kinetic rate limiter for the removal of excess grain boundary defects in these materials. Second, the magnitude of relaxation strengthening is explored over a wide range of grain sizes spanning the Hall-Petch breakdown, with an apparent maximum hardening effect found at a grain size below 10 nm. The apparent activation volume for plastic deformation is unaffected by annealing for grain sizes down to ;10 nm, but increases with annealing for the finest grain sizes, suggesting a change in the dominant deformation mechanism for these structures.

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Section: A Linear Hardening Regimesupporting

confidence: 85%

Grain boundary relaxation strengthening of nanocrystalline Ni–W alloys

2012

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“…In addition, recent studies showed that diffusion or segregation processes in ufg materials are considerably influenced by the highly-distorted non-equilibrium grain boundaries [65][66][67][68]. The vacancy-type free volumes are supposed to be mainly located in the grain boundary regions, thus enhancing grain boundary diffusion.…”

Section: Discussionmentioning

confidence: 99%

Phase separation of a supersaturated nanocrystalline Cu–Co alloy and its influence on thermal stability

et al. 2015

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The thermal decomposition behavior, the microstructural evolution and its influence on the mechanical properties of a supersaturated Cu-Co solid solution with ~100 nm average grain size prepared by severe plastic deformation is investigated under non-isothermal and isothermal annealing conditions. Pure fine-grained Cu and Co exhibit substantial grain growth upon annealing, whereas the Cu-Co alloy is thermally stable at the same annealing temperatures. The annealed microstructures are studied by independent characterization methods, including scanning electron microscopy, electron energy loss spectroscopy and atom probe tomography. The phase separation process in the Cu-Co alloy proceeds by the same mechanism, but on different length scales: a fine scaled spinodal-type decomposition is observed in the grain interior, simultaneously Co and Cu regions with a larger scale are formed near the grain boundary regions. Subsequent grain growth at higher annealing temperatures results in a microstructure consisting of the pure equilibrium phases. Such mechanisms can be used to tailor nano structures to optimize certain properties. Published in

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“…For example, recent studies demonstrated that transport properties of UFG materials (diffusion, segregation, etc.) are markedly affected by a so-called "nonequilibrium" grain boundary state [8][9][10]. At this place it is important to highlight that a broad spectrum of diffusivities of short-circuit paths is observed in UFG materials -contributions of high-angle grain boundaries with both "normal" and significantly enhanced diffusion rates can be differentiated in SPD-processed materials [11,12].…”

Section: Introductionmentioning

confidence: 99%

Grain boundaries in ultrafine grained materials processed by severe plastic deformation and related phenomena

Sauvage

Wilde

Divinski

et al. 2012

Materials Science and Engineering: A

476

219

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Grain boundaries in ultrafine grained (UFG) materials processed by severe plastic deformation (SPD) are often called "non-equilibrium" grain boundaries. Such boundaries are characterized by excess grain boundary energy, presence of long range elastic stresses and enhanced free volumes. These features and related phenomena (diffusion, segregation, etc.) have been the object of intense studies and the obtained results provide convincing evidence of the importance of a non-equilibrium state of high angle grain boundaries for UFG materials with unusual properties. The aims of the present paper are first to give a short overview of this research field and then to consider tangled, yet unclear issues and outline the ways of oncoming studies. A special emphasis is given on the specific structure of grain boundaries in ultrafine grained materials processed by SPD, on grain boundary segregation, on interfacial mixing linked to heterophase boundaries and on grain boundary diffusion. The connection between these unique features and the mechanical properties or the thermal stability of the ultrafine grained alloys is also discussed.

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Grain boundary diffusion characteristics of nanostructured nickel

Cited by 268 publications

References 8 publications

Grain boundary relaxation strengthening of nanocrystalline Ni–W alloys

Grain boundary relaxation strengthening of nanocrystalline Ni–W alloys

Phase separation of a supersaturated nanocrystalline Cu–Co alloy and its influence on thermal stability

Grain boundaries in ultrafine grained materials processed by severe plastic deformation and related phenomena

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