Low temperature stress relaxation of nanocrystalline nickel

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

doi:10.1007/bf00349669

Cited by 12 publications

(6 citation statements)

References 12 publications

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“…Second, and the most important, as the grain size falls below around 50 nm, a variety of other deformation mechanisms can operate. Grain boundaries play a more dominant role in plastic deformation such as the source or sink of dislocations [33][34][35][36][37] or grain boundary siding by enhanced Coble diffusion [38][39][40][41]. Such a shift of deformation mode, in many cases, is reflected in the reduced slope of the Hall-Petch relationship, as is also shown in Fig.…”

Section: Effect Of Dispersions On Hardness Of Nanocrystalline Nimentioning

confidence: 81%

Nanocrystalline nickel dispersed with nano-size WO3 particles synthesized by electrodeposition

et al. 2012

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A new class of bulk nanocrystalline nickel dispersed with nano-scale WO 3 particles has been synthesized by conventional electrodeposition to clarify the effect of the presence of nano-size dispersions on the strength and thermal stability of nanocrystalline structures. It was found that WO 3 particles of an initial size of 0.1 lm, when suspended in an electrolyte, fragmented into smaller nano-size particles, and were embedded into nanocrystalline nickel matrix of an average grain size of 45 nm during deposition. X-ray diffraction and transmission electron microscopy analyses revealed that phase transition of WO 3 particles occurred from an initial monoclinic to a tetragonal structure. The cause-and-effect relation between the fragmentation and the phase transition of WO 3 particles was discussed. Further hardening was confirmed in comparison with nanocrystalline pure nickel, but its increment was less than that predicted by the classical Orowan-type hardening of the particle-dislocation interaction. The discrepancy may be associated with a different dominant deformation mode which operates in a nanocrystalline regime.

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Section: Effect Of Dispersions On Hardness Of Nanocrystalline Nimentioning

confidence: 81%

Nanocrystalline nickel dispersed with nano-size WO3 particles synthesized by electrodeposition

et al. 2012

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“…The most important one is that as the grain size falls below around 50 nm, a variety of other deformation mechanisms can operate. Grain boundaries play a more dominant role in plastic deformation, acting as the source or sink of dislocations [27][28][29][30][31], or grain boundary siding by enhanced Coble diffusion [32][33][34][35]. Such a shift of deformation mode is in many cases reflected in the reduced slope of the Hall-Petch relationship, as is also shown in Figure 6, for pure nanocrystalline nickel with a grain size ranging from 20 to 50 nm [25].…”

Section: Effect Of Dispersions On Hardness Of Nanocrystalline Nimentioning

confidence: 83%

Novel Synthesis of Nanocrystalline Nickel Dispersed with Nano-size WO3 Particles by Electrodeposition

Kato¹,

Fujiwara²,

Miyamoto³

et al. 2015

Int J Metall Mater Eng

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Bulk nanocrystalline nickel dispersed homogenously with nano-scale hard WO 3 particles has been successfully synthesized by a novel synthesis using electrodeposition. In this synthesis, ionized WO 4 2-molecules in an electrolyte were transformed into WO 3 particles and embedded into a nanocrystalline nickel matrix during electrodeposition by controlling the pH and potential of the electrode. The effect of the presence of nano-size oxide dispersions on the strength and thermal stability of nanocrystalline structures was demonstrated. This is indeed a new class of bulk nanocrystalline metals in that nano-scale second-phase particles are not reactive precipitate from the solute-supersaturated matrix, but are stable oxide particles resistant to the so-called Ostwald ripening. In this regard, future optimization of this synthesis have potential to realize nanocrystalline metals with record-high strength and thermal stability, superior to their precipitates-or solutes-stabilized counterparts.

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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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Low temperature stress relaxation of nanocrystalline nickel

Cited by 12 publications

References 12 publications

Nanocrystalline nickel dispersed with nano-size WO3 particles synthesized by electrodeposition

Nanocrystalline nickel dispersed with nano-size WO3 particles synthesized by electrodeposition

Novel Synthesis of Nanocrystalline Nickel Dispersed with Nano-size WO3 Particles by Electrodeposition

Metals Property Changes Under Effect of Vacancy-Cluster Structures

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