Diffusion — Induced creep of polycrystalline and nanostructured metals

Kolobov, Yu. R.; Grabovetskaya, G. P.; Ratochka, I. V.; Ivanov, K. V.

doi:10.1016/s0965-9773(99)00311-6

Cited by 35 publications

(24 citation statements)

References 5 publications

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“…It has been shown that the diffusion in these materials is enhanced owing to intensive emission of non-equilibrium vacancies, which accompanies the dislocation climb. It is in agreement with experimental data (Schaefer et al 1995, Kolobov et al 1999, 2000, indicating the diffusion enhancement in mechanically synthesized nanocrystalline materials.…”

supporting

confidence: 92%

“…With these experimental data, the anomalously fast diffusion is treated as one of the unique phenomena occurring in nanocrystalline materials owing to interface and nanoscale effects (Gleiter 1989). At the same time, however, there are experimental data indicating that the boundary diffusion coefficients in dense bulk nanocrystalline materials are lower than those measured by Horvath et al (1987) and Schaefer et al (1995), Kolobov et al (1999Kolobov et al ( , 2000 and similar to the boundary diffusion coefficients in conventional coarse-grained polycrystals or a little higher (Wu¨rschum et al 1996, Tanimoto et al 1999, 2000. These data form the basis of the viewpoint that the atomic diffusion in nanocrystalline materials is similar to that in conventional coarse-grained polycrystals.…”

mentioning

confidence: 78%

“…Of special interest, from both fundamental and applied viewpoints, are the specific peculiarities of diffusion in nanocrystalline materials which crucially affect their outstanding mechanical and sensing characteristics. Following Horvath et al (1987), Gleiter (1989Gleiter ( , 2000, Schaefer et al (1995) and Kolobov et al (1999Kolobov et al ( , 2000, nanocrystalline materials exhibit anomalously enhanced diffusion properties. For instance, the boundary diffusion coefficients in bulk nanocrystalline materials fabricated by high-pressure compaction and severe plastic deformation methods are several orders of magnitude larger than those in conventional polycrystalline materials with the same chemical composition (Horvath et al 1987, Gleiter 1989, 2000, Schaefer et al 1995, Kolobov et al 1999, 2000.…”

mentioning

confidence: 97%

“…Nevertheless, mechanically synthesized (by severe plastic deformation, etc.) nanocrystalline materials are definitely recognized to exhibit enhanced diffusion properties compared with those of nanocrystalline materials fabricated by non-mechanical (more equilibrium than mechanical) methods and those of coarse-grained polycrystals (Schaefer et al 1995, Kolobov et al 1999, 2000. This experimentally documented phenomenon can be naturally explained as occurring because of the deformationinduced, highly defected (non-equilibrium) state of grain boundaries, in which case the grain-boundary diffusivity significantly increases (Nazarov 2000, Ovid'ko and Reizis 2001).…”

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confidence: 99%

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Grain-boundary dislocations and enhanced diffusion in nanocrystalline bulk materials and films

Ovid’ko¹,

Sheĭnerman

2003

Philosophical Magazine

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A theoretical model is suggested which describes the transformations of grainboundary dislocation walls and their influence on diffusion processes in nanocrystalline materials fabricated under highly non-equilibrium conditions. It is shown that the decay of boundary dislocation walls of finite extent, occurring via the climb of boundary dislocations and the corresponding emission of vacancies, is capable of highly enhancing the grain-boundary diffusion in nanocrystalline materials. The enhanced diffusion, in turn, strongly affects the deformation behaviour of nanocrystalline materials. In the case of nanocrystalline films deposited on to substrates, the effects of misfit stresses on the transformations of boundary dislocation walls and the diffusion are analysed. It is demonstrated that the mean diffusion coefficient in a nanocrystalline film may increase by approximately several orders of magnitude owing to misfit stresses. } 1. Introduction In recent years, nanocrystalline materials have attracted tremendous attention motivated by their wide applications in advanced technologies (for example Chow et al. (2000), Gleiter (2000) and Roco et al. (2000)). Of special interest, from both fundamental and applied viewpoints, are the specific peculiarities of diffusion in nanocrystalline materials which crucially affect their outstanding mechanical and sensing characteristics. Following Horvath et al. (1987), Gleiter (1989, 2000, Schaefer et al. (1995) and Kolobov et al. (1999Kolobov et al. ( , 2000, nanocrystalline materials exhibit anomalously enhanced diffusion properties. For instance, the boundary diffusion coefficients in bulk nanocrystalline materials fabricated by high-pressure compaction and severe plastic deformation methods are several orders of magnitude larger than those in conventional polycrystalline materials with the same chemical composition (Horvath et al.

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supporting

confidence: 92%

mentioning

confidence: 78%

mentioning

confidence: 97%

mentioning

confidence: 99%

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Grain-boundary dislocations and enhanced diffusion in nanocrystalline bulk materials and films

Ovid’ko¹,

Sheĭnerman

2003

Philosophical Magazine

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“…It is supposed that some nanocrystalline metallic alloys and ceramic materials show superplasticity at lower temperatures and for higher strain rates [7,8] in comparison to its coarse-grained counterparts. Some experimental results also imply opportunity of nanostructured materials to achieve high diffusion rate [9][10][11].…”

Section: Introductionmentioning

confidence: 95%

New Approach In The Properties Evaluation Of Ultrafine-Grained OFHC Copper

Kvačkaj¹,

Kováčová²,

Bidulská³

et al. 2015

Archives of Metallurgy and Materials

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In this study, static, dynamic and tribological properties of ultrafine-grained (UFG) oxygen-free high thermal conductivity (OFHC) copper were investigated in detail. In order to evaluate the mechanical behaviour at different strain rates, OFHC copper was tested using two devices resulting in static and dynamic regimes. Moreover, the copper was subjected to two different processing methods, which made possible to study the influence of structure. The study of strain rate and microstructure was focused on progress in the mechanical properties after tensile tests. It was found that the strain rate is an important parameter affecting mechanical properties of copper. The ultimate tensile strength increased with the strain rate increasing and this effect was more visible at high strain rates (ε ∼10 2 s −1 ). However, the reduction of area had a different progress depending on microstructural features of materials (coarse-grained vs. ultrafine-grained structure) and introduced strain rate conditions during plastic deformation (static vs. dynamic regime). The wear behaviour of copper was investigated through pin-on-disk tests. The wear tracks examination showed that the delamination and the mild oxidational wears are the main wear mechanisms.Keywords: OFHC copper, UFG, ECAP, strain rate, fractography, wear resistance W pracy zbadano szczegółowo statyczne, dynamiczne i tribologiczne właściwości ultra drobnoziarnistej (UFG) beztlenowej miedzi o wysokiej przewodności cieplnej (OFHC). W celu oceny właściwości mechanicznych przy różnych szybkościach odkształcenia, miedź OFHC badano za pomocą dwóch urządzeń w warunkach statycznych i dynamicznych. Ponadto miedź poddano dwóm różnym sposobom przetwarzania, co umożliwiło badanie wpływu struktury. Badanie szybkości odkształcenia i mikrostruktury koncentrowało się na zmianie właściwości mechanicznych po próbie rozciągania. Stwierdzono, że szybkość odkształcania jest ważnym parametrem wpływającym na właściwości mechaniczne miedzi. Wytrzymałość na rozciąganie wzrosła ze wzrostem szybkości odkształcenia i ten efekt był bardziej widocznyprzy dużej szybkości odkształcania (ε ∼10 2 s −1 ). Jednak zmniejszenie obrazu przebiegało inaczej w zależności od cech mikrostruktury materiałów (struktura gruboziarnista a struktura ultra drobnoziarnista) i zadanych warunków szybkości odkształcenia podczas odkształcenia plastycznego (warunki statyczne a warunki dynamiczne). Zużycie miedzi badano za pomocą testów zarysowania. Badanie ścieżek zużycia wykazało, że delaminacja i umiarkowane utlenienie to główne mechanizmy zużycia.

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