Grain morphology and crystal structure of pre-transition oxides formed on Zircaloy-4

Gong, Weijia; Zhang, Hailong; Qiao, Yu; Tian, Hao; Ni, Xiaodong; Li, Zhongkui; Wang, Xitao

doi:10.1016/j.corsci.2013.05.007

Cited by 45 publications

(15 citation statements)

References 28 publications

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“…Such phenomena indicate an increase in the thickness of Figure 6 shows the GIXRD results of the corroded samples after 3-day and 42-day exposures. It can be seen that the oxide film mainly consists of monoclinic zirconia (m-ZrO 2 ), which is consistent with the results in [5,52,53]. Due to the contribution of the substrate, the diffraction peaks of α-Zr can still be observed on the GIXRD patterns for all samples corroded after a 3-day exposure (Figure 6a).…”

Section: Characterizations Of the Substratessupporting

confidence: 86%

“…Wang et al [13,67] reported that only nanosized zirconia grains form on the surface of Zircaloy-4 after a short-time corrosion. Gong et al [52] also observed this phenomenon and pointed out that the nanosized zirconia grains formed on the surface of Zircaloy-4 are almost defenseless against the ingression of oxygen in the corrosive environment. Therefore, the corrosion rates of the samples are still relatively fast at the early stage of corrosion.…”

Section: Diffusion Coefficient Of Oxygen In a Substratementioning

confidence: 86%

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Calculation of Oxygen Diffusion Coefficients in Oxide Films Formed on Low-Temperature Annealed Zr Alloys and Their Related Corrosion Behavior

Zhang

Chen

Zhao³

et al. 2019

Metals

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The growth of oxide film, which results from the inward oxygen diffusion from a corrosive environment, is a critical consideration for the corrosion resistance of zirconium alloys. This work calculates the oxygen diffusion coefficients in the oxide films formed on zirconium alloys annealed at 400~500 °C and investigates the related corrosion behavior. The annealed samples have a close size for the second-phase particles but a distinctive hardness, indicating the difference in substrate conditions. The weight gain of all samples highly follows parabolic laws. The weight gain of the sample annealed at 400 °C has the fastest increase rate at the very beginning of the corrosion test, but its oxide film has the slowest growth rate as the corrosion proceeds. By contrast, the sample annealed at 500 °C shows the lowest weight gain but the highest corrosion rate constant. Such a corrosion behavior is attributed to the amount of defects existing in the oxide film formed on the annealed samples; fewer defects would provide a lower fraction of short-circuit diffusion in total diffusion, resulting in a lower diffusion coefficient of oxygen in the oxide film, thereby producing better corrosion resistance. This is consistent with the calculated diffusion coefficients of oxygen in the oxide films: 3.252 × 10−11 cm2/s, 3.464 × 10−11 cm2/s and 3.740 × 10−11 cm2/s for the samples annealed at 400 °C, 450 °C, and 500 °C, respectively.

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Section: Characterizations Of the Substratessupporting

confidence: 86%

Section: Diffusion Coefficient Of Oxygen In a Substratementioning

confidence: 86%

Calculation of Oxygen Diffusion Coefficients in Oxide Films Formed on Low-Temperature Annealed Zr Alloys and Their Related Corrosion Behavior

Zhang

Chen

Zhao³

et al. 2019

Metals

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“…Other studies have shown that small amounts of tetragonal ZrO 2 will remain after preparation of a TEM foil [24,27], but it is difficult to determine the amount of stress required to stabilize this phase. The partial oxidation that occurred in the sample oxidized at 650ºC reveals a possible dependence of oxidation on crystallographic orientation, as expected based upon previous work done on bulk alloys and thin film zirconium samples [13,22,35,53], and future work will focus on better elucidating these effects. Ploc, using an agglomeration of data from various authors, showed that when oxide thickness is shown versus Zr orientation certain directions show a preference for thicker oxides, however this work was focused on the epitaxial relationship of the oxide to the base metal [13].…”

Section: Comparison Of In-situ and Autoclave Samplessupporting

confidence: 70%

“…These techniques have provided an extensive knowledge base for the morphology and structure of the oxides formed on these alloys, including cracking behavior [23,26], crystal structure [23,25,26,29], and the start of breakaway corrosion [9,31]. A variety of oxidation environments for zirconium-based alloys have been studied as well, including oxygen [32,33], steam [7,8,34,35], water [7,9,25], water vapor [32], air [36][37][38], with all studies showing similar oxide structures and appearance, with only changes in kinetics of oxidation being noted. The majority of these experiments, however, have been done using autoclave or reactor corroded samples over long periods of time, which has not allowed for the study of the initial steps of corrosion.…”

mentioning

confidence: 99%

Determination of the initial oxidation behavior of Zircaloy-4 by in-situ TEM

Harlow

Ghassemi

Taheri

2016

Journal of Nuclear Materials

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The corrosion behavior of Zircaloy-4 (Zry-4), specifically by oxidation, is a problem of great importance as this material is critical for current nuclear reactor cladding. The early formation behavior and structure of the oxide layer during oxidation was studied using in-situ TEM techniques that allowed for Zry-4 to be monitored during corrosion. These environmental exposure experiments were coupled with precession electron diffraction to identify and quantify the phases present in the samples before and after the oxidation. Following short-term, high temperature oxidation, the dominant phase was revealed to be monoclinic ZrO 2 in a columnar structure. These samples oxidized in-situ contained structures that correlated well with bulk Zry-4 subjected to autoclave treatment, which were used for comparison and validation of this technique. By using in-situ TEM the effect of microstructure features, such as grain boundaries, on oxidation behavior of an alloy can be studied. The technique presented herein holds the potential to be applied any alloy system to study these effects.

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“…For Zircaloy-2, the crystal structures appear as Zr > Zr 3 O > tetragonal ZrO 2 > monoclinic ZrO 2 from the matrix to the surface [7]. For a Zircaloy-4 alloy oxidized at 673 K in steam, the monoclinic columnar grains form inner oxide zone, and porous equiaxed grains are outer oxides [8]. At 923 K, the dominant phase is still monoclinic ZrO 2 in a columnar form [9,10].…”

Section: Introductionmentioning

confidence: 99%

X-Ray Computer Tomography Study of Degradation of the Zircaloy-2 Tubes Oxidized at High Temperatures

Trybuś

Olivé

Lenoir

et al. 2019

Advances in Materials Science

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The investigations of high-temperature oxidation of zirconium alloys, applied for fuel pellets in nuclear power plants, are usually limited to oxidation kinetics, phase transformations and microstructural characterization. The purpose of this research was to characterize the degradation phenomena occurring within oxide layer and at the interface oxide/metal, on internal and external Zircaloy-2 tube surfaces, below and over crystalline transformation temperature of zirconium oxides. The commercial tubes were oxidized at 1273 K and 1373 K in calm air for 30 min and then examined with a technique novel for such purpose, namely a high-resolution X-ray computer tomography. The light microscopy was used to examine the cross-surfaces. The obtained results show that the form and intensity of oxide damage is significant and it is in a complicated way related to oxidation temperature and on whether external or internal tube surface is studied. The found oxide layer damage forms include surface cracks, the detachment of oxide layers, the appearance of voids, and nodular corrosion. The oxidation effects and damage appearance are discussed taking into account the processes such as formation of oxides, their phase transformation, stress-enhanced formation and propagation of cracks, diffusion of vacancies, formation of nitrides, diffusion of hydrogen into interface oxide-metal, incubation of cracks on second phase precipitates are taken into account to explain the observed phenomena.

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Grain morphology and crystal structure of pre-transition oxides formed on Zircaloy-4

Cited by 45 publications

References 28 publications

Calculation of Oxygen Diffusion Coefficients in Oxide Films Formed on Low-Temperature Annealed Zr Alloys and Their Related Corrosion Behavior

Calculation of Oxygen Diffusion Coefficients in Oxide Films Formed on Low-Temperature Annealed Zr Alloys and Their Related Corrosion Behavior

Determination of the initial oxidation behavior of Zircaloy-4 by in-situ TEM

X-Ray Computer Tomography Study of Degradation of the Zircaloy-2 Tubes Oxidized at High Temperatures

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