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

A. T. Motta, M. J.Gomes Da Silva, A. Yilmazbayhan, R. J. Comstock, Z. Cai, B. Lai

Research output: Chapter in Book/Report/Conference proceedingConference contribution

20 Scopus citations

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 nonpro-tective 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)
Title of host publicationZirconium in the Nuclear Industry
Subtitle of host publication15th International Symposium
PublisherAmerican Society for Testing and Materials
Pages486-506
Number of pages21
ISBN (Print)9780803145146
DOIs
StatePublished - 2009
Event15th International Symposium on Zirconium in the Nuclear Industry - Sunriver, OR, United States
Duration: Jun 24 2007Jun 28 2007

Publication series

NameASTM Special Technical Publication
Volume1505 STP
ISSN (Print)0066-0558

Other

Other15th International Symposium on Zirconium in the Nuclear Industry
CountryUnited States
CitySunriver, OR
Period6/24/076/28/07

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

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