Microbeam synchrotron radiation diffraction and fluorescence of oxide layers formed on zirconium alloys at different corrosion temperatures
- The Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical and Nuclear Engineering; Naval Nuclear Lab., Schenectady, NY (United States)
- Naval Nuclear Lab., Schenectady, NY (United States)
- Naval Nuclear Lab., West Mifflin, PA (United States)
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source
- The Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical and Nuclear Engineering
Autoclave corrosion tests of Zircaloy-4 were performed at temperatures ranging from 274°C to 427 °C to determine how the characteristics of the oxide layer changed with corrosion temperature. Corroded samples were prepared in cross-section and examined at the Advanced Photon Source using x-ray diffraction and fluorescence with sub-micron spatial resolution. These measurements provide high fidelity data for characterization of the oxide layer grown on zirconium alloys over a range of temperatures to better understand the fundamental mechanisms of corrosion. It was found that the size of the monoclinic oxide grains increases with distance from the metal-oxide interface, while the average grain size of the tetragonal oxide phase decreases. This is consistent with the continuous nucleation of a mixture of equiaxed tetragonal and monoclinic grains at the metal-oxide interface, of which only the monoclinic oxide grains that are properly aligned to minimize stresses grow into long columnar oxide grains. The tetragonal phase oxide grains transform to monoclinic oxide once a critical size is reached. While the monoclinic oxide grain size increases with corrosion temperature, the tetragonal phase grain size remains below a maximum value. Evolution of the tetragonal fraction, calculated with the Garvie-Nicholson formula, was observed, with local maxima seen just before transition and local minima seen at oxide locations corresponding to the oxide kinetic transition. No difference was observed in the tetragonal phase fraction in the oxide layers formed at different corrosion temperatures. Detailed fluorescence and diffraction mapping of one sample showed the evolution of the diffraction intensity over a short range in the oxide. In conclusion, this work provides a systematic study revealing fundamental characteristics of the microstructure of Zircaloy-4 oxide layers to further understanding of corrosion resistance of these materials.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA), Office of Naval Reactors (NA-30)
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1573803
- Alternate ID(s):
- OSTI ID: 1560736
OSTI ID: 22886468
- Journal Information:
- Journal of Nuclear Materials, Journal Name: Journal of Nuclear Materials Journal Issue: C Vol. 526; ISSN 0022-3115
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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