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Effect of the theta-alpha-Al2O3 transformation on the oxidation behavior of beta-NiAl+ZrIsothermal oxidation of NiAl+Zr has been performed over the temperature range of 800-1200 C and studied by TGA, XRD, and SEM. A discontinuous decrease in growth rate of two orders of magnitude was observed at 1000 C due to the formation of alpha-Al2O3 from theta-Al2O3. This transformation also resulted in a dramatic change in the surface morphology of the scales, as a whisker topography was changed into a weblike network of oxide ridges and radial transformation cracks. It is believed that the ridges are evidence for a short-circuit outward aluminum diffusion growth mechanism that has been documented in a number of O-18 tracer studies.
Document ID
19890051229
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Rybicki, George C. (NASA Lewis Research Center Cleveland, OH, United States)
Smialek, James L. (NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 14, 2013
Publication Date
April 1, 1989
Publication Information
Publication: Oxidation of Metals
Volume: 31
ISSN: 0030-770X
Subject Category
METALLIC MATERIALS
Distribution Limits
Public
Copyright
Other