Etude micrographique du processus de desquamation (“break-away”) au cours de l'oxydation du zirconium

Keys, L.H.; Béranger, G.; Gelas, Bruno; Lacombe, P.

doi:10.1016/0022-5088(68)90114-8

Cited by 19 publications

(5 citation statements)

References 9 publications

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“…1-4), we conclude in partial consistence with Keys et al [14] that the breakaway oxidation phenomena is associated with the change of non-stoichiometric (anion-deficient) and protective black oxide into stoichiometric and non-protective white (or grey) oxide. This change accompanies a decrease in the plasticity of the oxide layer and leads to cracks in the outer stoichiometric region and a mechanical breakdown under the growth stress originating from a high value (1.56) for the Pilling-Bedworth ratio [4].…”

Section: Resultssupporting

confidence: 68%

Microstructural characterization of ZrO2 layers formed during the transition to breakaway oxidation

Park

Jeong

Lee

2010

Journal of Nuclear Materials

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Section: Resultssupporting

confidence: 68%

Microstructural characterization of ZrO2 layers formed during the transition to breakaway oxidation

Park

Jeong

Lee

2010

Journal of Nuclear Materials

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“…From the results mentioned above, we conclude in partial consistence with Keys et al [9] that the breakaway oxidation phenomena is associated with the change of non-stoichiometric (anion-deficient) and protective black oxide into stoichiometric and non-protective white(or grey) oxide. This change accompanies a decrease in the plasticity of the oxide layer and leads to cracks in the outer stoichiometric region and a mechanical breakdown under the growth stress originating from a high value (1.56) for the Pilling-Bedworth ratio [10].…”

Section: Methodssupporting

confidence: 70%

An electron microscopy study on the Zr oxides formed during the transition to breakaway oxidation

Choi

Park

2012

MRS Proc.

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In order to characterize the microstructure of oxide layers formed on Zircaloy-4 tubes during the breakaway transition, oxidation tests in a flowing steam environment were performed at 1000 with a different oxidation time. It was found that breakaway oxidation occurred after the oxidation time of 3000s, and zirconium dioxide layers existed in two mixed crystallographic forms of the tetragonal and monoclinic phase in all samples. The zirconium oxide layers showed enhanced crystallinity, increase in grain size, and fine pores at the grain boundary after breakaway oxidation. We found that the initiation of breakaway-oxidation instability originated from these microstructural changes.

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“…In the next stage of the oxidation, no relationship was found between the oxidation growth rate and the preferential orientation [94]. The oxide grows evenly, is adherent and black.…”

Section: Morphology and Porosity Of The Oxide Layersmentioning

confidence: 92%

Corrosion of Zr Alloys in Water and Steam

1994

Materials Science Monographs

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The oxide, Zr0 2 , is formed by the reaction of Zr with water. Water molecules dissociate on the oxide surface, the oxygen formed diffuses through anion vacancies in the oxide to the metal-oxide boundary, where part of the oxygen dissolves in the metal and part reacts to form new oxide. As the oxide has a greater volume than the metal from which it was formed, strain is produced at the boundary. Hydrogen formed in the reaction partly diffused through the oxide into the metal.The process of oxidation of Zr and its alloys in water and steam passes through several stages with correspondingly different laws for the rate of oxide growth as a function of temperature and the corrosion exposure time. In the initial stage, especially at low temperatures, the oxide growth has a complex character, controlled by either a logarithmic or parabolic rate law. This period is a result of localized oxidation of the grain boundaries and of intermetallic species, preferential oxidation of some grains, etc.At temperatures above 300 °C, the oxidation rate is controlled by a cubic or parabolic law. Black, adhering and non-stoichiometric Zr0 2 is also formed. After a certain period of time, given by the oxidation conditions, a change occurs in the oxidation kinetics, appearing as a break on the kinetic curves, after which the oxidation kinetics obey a linear law. This is mostly accompanied by the formation of white or light grey (light brown) oxide, that adheres poorly to the metal and peels off.The increase in the mass of the Zr alloys sample with time can be expressed by the relationship ΔΜ = kt n (9.1)where Am is the mass increase per unit surface area, t is the oxidation time, k is the oxidation rate constant, and n is a dimensionless coefficient. The corrosion process is affected by a great many factors, the most important of which are: the chemical composition of the Zr alloy, both alloying elements and impurities in the metal, the metal structure determined by the technology of alloy working, the quality of the alloy surface, determined by the technology, the composition of the corrosive medium, the influence of radiation, especially the flux and the fluence of fast neutrons. 9.

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Etude micrographique du processus de desquamation (“break-away”) au cours de l'oxydation du zirconium

Cited by 19 publications

References 9 publications

Microstructural characterization of ZrO2 layers formed during the transition to breakaway oxidation

Microstructural characterization of ZrO2 layers formed during the transition to breakaway oxidation

An electron microscopy study on the Zr oxides formed during the transition to breakaway oxidation

Corrosion of Zr Alloys in Water and Steam

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