The low-stress creep of fine-grain uranium dioxide

Chung, T. E.; Davies, Thomas

doi:10.1016/0001-6160(79)90014-2

Cited by 50 publications

(8 citation statements)

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“…This result is quite original, since it is generally assumed that creep deformation of UO 2 in conditions close to those chosen in this study does not lead to a change in form of the grains [6] [19]. It is consistent with creep processes considered in different ceramics [23] and indicates that plastic deformation and sliding processes, within the grains, are also involved in the creep process.…”

Section: Discussionsupporting

confidence: 86%

“…It is generally assumed in the literature that creep deformation of UO 2 pellets during compression tests does not induce a significant change in the grain shape, which remains equiax (at least in testing conditions and deformation levels close to those considered in this work) [19,6]. This characteristic is generally interpreted as a consequence of a grain boundary sliding (GBS) mechanism without grain deformation.…”

Section: Grain Shape and Orientation Changesmentioning

confidence: 68%

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Microstructural evolution of uranium dioxide following compression creep tests: An EBSD and image analysis study

Iltis

Gey²,

Cagna³

et al. 2015

Journal of Nuclear Materials

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International audienceSintered UO2 pellets with relatively large grains (similar to 25 pm) are tested at 1500 degrees C under a compressive stress of 50 MPa, at different deformation levels up to 12%. Electron Back Scattered Diffraction (EBSD) is used to follow the evolution, with deformation, of grains (size, shape, orientation) and sub-grains. Image analyses of SEM images are performed to characterize emergence of a population of micron size voids. For the considered microstructure and test conditions, the results show that the deformation process of UO2 globally corresponds to grain boundary sliding, partly accommodated by a dislocational creep within the grains, leading to a highly sub-structured state

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Section: Discussionsupporting

confidence: 86%

Section: Grain Shape and Orientation Changesmentioning

confidence: 68%

Microstructural evolution of uranium dioxide following compression creep tests: An EBSD and image analysis study

Iltis

Gey²,

Cagna³

et al. 2015

Journal of Nuclear Materials

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show abstract

“…22 These observations indicate that grain-boundary sliding is the primary deformation mechanism, the strain rate being controlled by the diffusion necessary to accommodate the motion of the grains. Such a mechanism, described by the Ashby-Verrall model, 33 makes it possible to explain successfully the microstructural and mechanical behavior observed in other ceramic materials with similar grain sizes, where a stress exponent close to unity was systematically reported: UO 2 , n ϭ 1.5, d ϭ 2-10 m; 34 NiO, n ϭ 1.4, d ϭ 9 m; 35 Y 2 O 3 -stabilized cubic ZrO 2 , n ϭ 1.3, d ϭ 2-6 m; 36 and YBa 2 Cu 3 O x , n ϭ 1.0, d ϭ 10 m. 37 The Ashby-Verrall model for grain-boundary sliding accommodated by diffusion leads to 33…”

Section: (2) Deformation Mechanismsmentioning

confidence: 64%

Ytterbium Cation Diffusion in Yttrium Aluminum Garnet (YAG)—Implications for Creep Mechanisms

Jiménez–Melendo

Haneda

Nozawa

2001

Journal of the American Ceramic Society

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The lattice and grain-boundary diffusion coefficients of ytterbium, which substitutes for yttrium, have been determined in high-purity, stoichiometric yttrium aluminum garnet (YAG) polycrystals in the temperature range 1400°-1550°C, in air. Ytterbium oxide thin films were produced on the YAG surfaces by a dipping method. After diffusion treatments, the penetration profiles were established by secondary ion mass spectroscopy, and the diffusion coefficients were calculated from the thin-film solution of Fick's equation. The difference between the volume and grain-boundary diffusion coefficients is ϳ5 orders of magnitude in the temperature range studied. The cation activation energies (ϳ550 kJ/mol) are much larger than those for oxygen (ϳ300 -350 kJ/mol). The effective diffusion coefficient deduced from high-temperature deformation data reported in the literature for YAG polycrystals, assuming grain-boundary sliding accommodated by volume diffusion, is in excellent agreement, both in magnitude and activation energy, with the cation diffusion data.

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“…The ability of ceramics to undergo superplastic deformation was, initially, recognized in 1979 and 1980 for uranium oxide and magnesium oxide, respectively 1, 2. In 1986, Wakai et al 3 reported experiments showing an elongation of 120% for a fine‐grained (<300 nm) 3 mol%‐Y 2 O 3 stabilized tetragonal zirconia (3Y‐TZP) at 1723 K. Afterward, a large number of investigations 4–12 have been carried out to identify the underlying mechanism for such a deformation in a wide range of temperatures and applied stresses.…”

Section: Introductionmentioning

confidence: 99%

High temperature mechanical spectroscopy of yttria stabilized zirconia reinforced with carbon nanotubes

Mazaheri

Mari

Schaller

2010

Physica Status Solidi (a)

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High temperature mechanical properties of zirconia reinforced with carbon-nanotubes (CNTs) are studied by mechanical spectroscopy. CNTs limit zirconia grainboundary sliding (GBS) and consequently deformation. Concurrent grain-growth and plastic deformation lead to a substantial error in the evaluation of deformation activation-enthalpy. Hence, a new calculation was developed in order to account for the effect of grain growth. The corrected enthalpy is comparable with the lattice diffusion energy of cations (Zr 4þ , Y 3þ ), which evidences that at low-stress regime, GBS is accommodated by diffusional creep.

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The low-stress creep of fine-grain uranium dioxide

Cited by 50 publications

References 10 publications

Microstructural evolution of uranium dioxide following compression creep tests: An EBSD and image analysis study

Microstructural evolution of uranium dioxide following compression creep tests: An EBSD and image analysis study

Ytterbium Cation Diffusion in Yttrium Aluminum Garnet (YAG)—Implications for Creep Mechanisms

High temperature mechanical spectroscopy of yttria stabilized zirconia reinforced with carbon nanotubes

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