Stress relaxation following heating of nanocrystalline nickel

Трусов, Л. И.; Khvostantseva, T.P.; Соловьев, В. А.; Mel'nikova, V. A.

doi:10.1016/0965-9773(94)90086-8

Cited by 11 publications

(5 citation statements)

References 14 publications

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“…Very recently, the present authors found that the strain-rate sensitivity exponent for n-Ni-Fe was n ‫ס‬ 0.01 at room temperature, 36 which excluded possibility of normal GB sliding mechanism, for n is usually near 0.5 as GB sliding prevails. Other investigations showed that GB sliding occurred as homologous temperature (T/T m ) > 0.36 on n-Ni 37 and n-Mg. 38 Hence, it seems unlikely that GB sliding would occur here at room temperature [approximately 0.18 T m ; here T m is melting point (approximately 1452 °C) of Ni-Fe]. Therefore, deformation mechanism in n-Ni-Fe at room temperature could still be some kind of dislocation mode.…”

Section: B Deformation Mechanismmentioning

confidence: 96%

Microstructures and Mechanical Behavior of Bulk Nanocrystalline γ–Ni–Fe Produced by a Mechanochemical Method

Qin

Lee

2002

J. Mater. Res.

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The microstructures and mechanical behavior of bulk nanocrystalline γ–Ni–xFe (n-Ni–Fe) with x = ∼19–21 wt%, synthesized by a mechanochemical method plus hot-isostatic pressing, were investigated using microstructural analysis [x-ray diffraction, energy-dispersive spectroscopy, light emission spectrum, atomic force microscopy (AFM), and optical microscopy (OM)], and mechanical (indentation and compression) tests, respectively. The results indicated that the yield strength (σ0.2) of n-Ni–Fe (d ∼ 33 nm) is about 13 times greater than that of conventional counterpart. The change of yield strength with grain size was basically in agreement with Hall–Petch relation in the size range (33–100 nm) investigated. OM observations demonstrated the existence of two sets of macroscopic bandlike deformation traces mostly orienting at 45–55° to the compression axis, while AFM observations revealed that these bandlike traces consist of ultrafine lines. The cause for high strength and the possible deformation mechanisms were discussed based on the characteristics of microstructures and deformation morphology of n-Ni–Fe.

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Section: B Deformation Mechanismmentioning

confidence: 96%

Microstructures and Mechanical Behavior of Bulk Nanocrystalline γ–Ni–Fe Produced by a Mechanochemical Method

Qin

Lee

2002

J. Mater. Res.

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“…Their faceting corresponded to the metal lattice type ( Figure 2) [13]. The effect of vacancy-cluster structures on the metals mechanical properties is considered in these studies [14][15][16] where studied the stress-strain (σ ~ ε) dependence in the uniaxial compression mode for the Ni nanocrystalline (70nm) samples with vacancy clusters formed in the process its nanopowders compaction [13]. The Figure 3 shows the Ni stress-strain curves with a grain size of 100 µm ( Figure 3a) and nanocrystalline Ni (70nm) with vacancy clusters ( Figure 3b).…”

Section: The Vacancy-clusters Formation In Nano-disperse Metal Media mentioning

confidence: 99%

“…The absence of the hardening effect under repeated loading of nanocrystalline Ni (70nm) samples indicated that innergrain plastic deformation occurs by a mechanism of diffusion-viscous flow without the formation of dislocation structure that changes the form and shape of the curve (σ ~ ε) at the initial stage of deformation [14][15][16]. As shown by special studies in stronglydeformed NMM the dislocation structure there is not exists [11,13] (Figure 2) and that is correlated with the theoretical estimates of the dislocation loop (0.5-1.5 µm) critical sizes [12].…”

Section: The Vacancy-clusters Formation In Nano-disperse Metal Media mentioning

confidence: 99%

Metals Property Changes Under Effect of Vacancy-Cluster Structures

Novikov¹

2019

IJMSA

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The experimental results analysis of a metals property changes under vacancy-cluster structure effects are shown.Two technological approaches of such structures obtaining are considered. The first is a nanopowders compaction under high (up to 5GPa) hydrostatic compression, on example of a Ni nanopowder (70nm). The second is the Al and Pb crystallization under the high-intensity plastic deformation [ε′ = (10 2 -10 4 ) sec -1 ] (НIPD) conditions on the "solid-liquid" boundary in the centrifugal casting machine with rotary speed up to 2000 rpm. Using the method of atomic force microscopy (AFM), vacancy cluster tubes (VCT) with average diameters of 39 nm for Al and 25 nm for Pb have been detected in the crystallized volume of Al and Pb metals. Discussed the physical model of a new substructure formation within the metals in the form of vacancy cluster tubes, obtained in the process of high-intensive plastic deformation (HIPD) during the process of mass crystallization of Al and Pb and the changes in the mechanical, magnetic and superconducting properties of the above metals, which followed this process. During Al and Pb crystallization under high-intensive plastic deformation (HIPD) range about [ε′ = (10 2 -10 4 ) sec -1 ] with specially selected modes of metals crystallization in high-speed centrifugal casting machine the special conditions are being created to achieve the dimensional effect of dynamic (shifting) re-crystallization. Shifting deformation during centrifugal crystallization caused primarily by a large incline of the temperature field from the periphery (relative to the cold wall of the rotor) to the molten central part of the rotor. The difference in the angular velocities of the already-frozen part of the metal (adjacent to the outer surface of the rotor wall) and the central part, where the metal still remains in the molten state, leads to a high-intensity deformation [ε′ = (10 2 -10 4 ) sec -1 ] of the crystallized metal melt solidified phase. Since the grain sizes at the crystallized phase initially comprise around tens of nano-meters (approximately crystal nucleation size), it becomes possible to achieve the dimensional effect of the dynamic re-crystallization of a «nanocrystalline» solidified metal at high shift of strain velocities. The ≪non-equilibrium vacancies≫ formed this way condense into vacancy clusters, which are formed in the centrifugal force field in the form of vacancy-shaped cluster tubes stretched out to the center of rotation of the rotor. The process proceeds under conditions far from the equilibrium in comparison with the usual crystallization of the metal from the melt. Such processes can lead to the formation of highly ordered non-equilibrium statescharacteristic of non-equilibrium open systems. Discussed the physical model of a metals vacancy-cluster structures formation at high hydrostatic nanopowders compression (up to 5 GPa) and high-intensity plastic deformation (HIPD) at the stage of Al and Pb alloys mass crystallization during centrifugation. Conclusion of the article i...

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“…Диссипация механической энергии при высокоинтенсивной сдвиговой деформации [7,8] в условиях сверхскоростного (2000 об/мин) центробежного литья на аппаратах нового типа способствует образованию высокой концентрации неравновесных вакансий (порядка ∼10 -2 ) в закристаллизованной части расплава, которые создают возможность для повторной перекристаллизации металла в твердой фазе (твердофазная перекристаллизация) в сильно неравновесных условиях с одновременной конденсацией неравновесных вакансий в поле центробежных сил в вакансионные кластеры в форме шестигранных трубок. Образование в металлах субструктуры в виде структурных элементов нового типавакансионных кластерных трубок, могут, прежде всего, существенно повлиять на механические свойства металла [19][20][21]. На (рис.…”

Section: обсуждение результатовunclassified

ОСОБЕННОСТИ СТРУКТУРИРОВАНИЯ ПРИ МАССОВОЙ КРИСТАЛЛИЗАЦИИ РАСПЛАВОВ Al И Pb В УСЛОВИЯХ ВЫСОКОИНТЕНСИВНОЙ ПЛАСТИЧЕСКОЙ ДЕФОРМАЦИИ ПРИ ЦЕНТРИФУГИРОВАНИИ

Tarasov¹,

Krjachko²,

Новиков³

2018

kcmf

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Представлены экспериментальные результаты по кристаллизации Al и Pb в условиях высокоинтенсивной пластической деформации [ε′ = (102–104) сек–1] на границе раздела «твердое-жидкое» в аппарате центробежного литья нового типа при скоростях вращения ротора до 2000 об/мин. В объёме закристаллизованных металлов Al и Pb методом атомной силовой микроскопии обнаружены вакансионные кластерные трубки со средними диаметрами Al – 39 нм, Pb – 25 нм. Обсуждается физическая модель образования в металлах новой субструктуры в виде вакансионных кластерных трубок, полученных при высокоинтенсивной пластической деформации.

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Stress relaxation following heating of nanocrystalline nickel

Cited by 11 publications

References 14 publications

Microstructures and Mechanical Behavior of Bulk Nanocrystalline γ–Ni–Fe Produced by a Mechanochemical Method

Microstructures and Mechanical Behavior of Bulk Nanocrystalline γ–Ni–Fe Produced by a Mechanochemical Method

Metals Property Changes Under Effect of Vacancy-Cluster Structures

ОСОБЕННОСТИ СТРУКТУРИРОВАНИЯ ПРИ МАССОВОЙ КРИСТАЛЛИЗАЦИИ РАСПЛАВОВ Al И Pb В УСЛОВИЯХ ВЫСОКОИНТЕНСИВНОЙ ПЛАСТИЧЕСКОЙ ДЕФОРМАЦИИ ПРИ ЦЕНТРИФУГИРОВАНИИ

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