Microstructural characterization of oxides formed on model Zr alloys using synchrotron radiation

Arthur Thompson Motta, M. J.G. Da Silva, A. Yilmazbayhan, R. J. Comstock, Z. Cai, B. Lai

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

To understand how alloy chemistry and microstructure impact corrosion performance, oxide layers formed at different stages of corrosion on various model zirconium alloys (Zr-xFe-yCr, Zr-xCu-yMo, for various x, y) and control materials (pure Zr, Zircaloy-4) were examined to determine their structure and the connection of such structure to corrosion kinetics and oxide stability. Microbeam synchrotron radiation diffraction and fluorescence of oxide cross sections were used to determine the oxide phases present, grain size, and orientation relationships as a function of distance from the oxide-metal interface. The results show a wide variation of corrosion behavior among the alloys, in terms of the pretransition corrosion kinetics and in terms of the oxide susceptibility to breakaway corrosion. The alloys that exhibited protective behavior at 500°C also were protective during 360°C corrosion testing. The Zr-0.4Fe-0.2Cr model ternary alloy showed protective behavior and stable oxide growth throughout the test. The results of the examination of the oxide layers with microbeam X-ray diffraction show clear differences in the structure of protective and nonprotective oxides both at the oxide-metal interface and in the bulk of the oxide layer. The nonprotective oxide interfaces show a smooth transition from metal to oxide with metal diffraction peaks disappearing as the monoclinic oxide peaks appear. In contrast, the protective oxides showed a complex structure near the oxide-metal interface, showing peaks from Zr3O suboxide and a highly oriented tetragonal oxide phase with specific orientation relationships with the monoclinic oxide and the base metal. The same interfacial structures are observed through their diffraction signals in protective oxide layers formed during both 360°C and 500°C corrosion testing. These diffraction peaks showed much higher intensities in the samples from 500°C testing. The results for the various model alloys are discussed to help elucidate the role of individual alloying elements in oxide formation and the influence of oxide microstructure on the corrosion mechanism.

Original languageEnglish (US)
JournalJournal of ASTM International
Volume5
Issue number3
DOIs
StatePublished - Mar 1 2008

Fingerprint

Synchrotrons
Synchrotron radiation
Oxides
Radiation
Corrosion
Metals
Diffraction
Testing
Zirconium alloys

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Materials Science(all)
  • Nuclear Energy and Engineering
  • Engineering(all)
  • Public Health, Environmental and Occupational Health

Cite this

Motta, Arthur Thompson ; Da Silva, M. J.G. ; Yilmazbayhan, A. ; Comstock, R. J. ; Cai, Z. ; Lai, B. / Microstructural characterization of oxides formed on model Zr alloys using synchrotron radiation. In: Journal of ASTM International. 2008 ; Vol. 5, No. 3.
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abstract = "To understand how alloy chemistry and microstructure impact corrosion performance, oxide layers formed at different stages of corrosion on various model zirconium alloys (Zr-xFe-yCr, Zr-xCu-yMo, for various x, y) and control materials (pure Zr, Zircaloy-4) were examined to determine their structure and the connection of such structure to corrosion kinetics and oxide stability. Microbeam synchrotron radiation diffraction and fluorescence of oxide cross sections were used to determine the oxide phases present, grain size, and orientation relationships as a function of distance from the oxide-metal interface. The results show a wide variation of corrosion behavior among the alloys, in terms of the pretransition corrosion kinetics and in terms of the oxide susceptibility to breakaway corrosion. The alloys that exhibited protective behavior at 500°C also were protective during 360°C corrosion testing. The Zr-0.4Fe-0.2Cr model ternary alloy showed protective behavior and stable oxide growth throughout the test. The results of the examination of the oxide layers with microbeam X-ray diffraction show clear differences in the structure of protective and nonprotective oxides both at the oxide-metal interface and in the bulk of the oxide layer. The nonprotective oxide interfaces show a smooth transition from metal to oxide with metal diffraction peaks disappearing as the monoclinic oxide peaks appear. In contrast, the protective oxides showed a complex structure near the oxide-metal interface, showing peaks from Zr3O suboxide and a highly oriented tetragonal oxide phase with specific orientation relationships with the monoclinic oxide and the base metal. The same interfacial structures are observed through their diffraction signals in protective oxide layers formed during both 360°C and 500°C corrosion testing. These diffraction peaks showed much higher intensities in the samples from 500°C testing. The results for the various model alloys are discussed to help elucidate the role of individual alloying elements in oxide formation and the influence of oxide microstructure on the corrosion mechanism.",
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Microstructural characterization of oxides formed on model Zr alloys using synchrotron radiation. / Motta, Arthur Thompson; Da Silva, M. J.G.; Yilmazbayhan, A.; Comstock, R. J.; Cai, Z.; Lai, B.

In: Journal of ASTM International, Vol. 5, No. 3, 01.03.2008.

Research output: Contribution to journalArticle

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