Grain boundary segregation of cation dopants in {alpha}-Al{sub 2}O{sub 3} scales
Journal Article
·
· Journal of the Electrochemical Society
- Oak Ridge National Lab., TN (United States)
A fe-20 atom % Cr-10% Al matrix was dispersed with a wide range of oxide particulates in order to study the effect of oxygen-active dopants on high-temperature oxidation performance and alumina scale microstructure. The effects of these various cation dopants have been correlated with dopant ion segregation to the {alpha}-Al{sub 2}O{sub 3} grain boundaries using analytical electron microscopy. Elements such as Mn and V showed little effect on the oxide scale microstructure and were not observed to segregate. Elements such as Y, Nd, and Gd were found to have a positive effect on oxidation performance and segregated to scale grain boundaries, resulting in finer, more columnar {alpha}-Al{sub 2}O{sub 3} grains. However, Ti, Ta, Ca, and Nb also were found to segregate but had less of an effect on oxidation behavior. These results indicate that cation segregation to scale grain boundaries is not a sufficient condition for achieving beneficial oxidation performance. The driving force for diffusion and segregation in growing alumina scales is discussed. Based on comparisons with an alloy containing an Al{sub 2}O{sub 3} dispersion, the finer scale grain sizes observed with reactive element oxide dispersions are the result of grain growth inhibition and not a heterogeneous nucleation effect.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 653339
- Journal Information:
- Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 6 Vol. 145; ISSN JESOAN; ISSN 0013-4651
- Country of Publication:
- United States
- Language:
- English
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