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High-temperature oxidation of a rapidly solidified amorphous Ta-Ir alloyThe oxidation products formed at 500 and 700 C on an amorphous Ta-44.5 at. pct Ir alloy in an Ar-0.1 percent O2 gas mixture were characterized using SEM, XRD, EPMA, TEM, STEM, AES, and XPS. Initially, a thin (3-4 nm) layer of Ta2O5 formed at the surface of the alloy. Continued growth of the Ta2O5, which occurred very rapidly, involved diffusion of oxygen anions from the Ta2O5/gas interface to the alloy/Ta2O5 interface, where tantalum was selectively oxidized. Because the oxide grew more quickly than iridium could diffuse back into the alloy, the iridium coalesced into platelets of crystalline iridium-rich alloy that were oriented approximately parallel to the oxide/alloy interface, and which became embedded in a matrix of Ta2O5. The unoxidized core remained in the glassy state. The oxidation process and/or the dissolution of oxygen into the unoxidized alloy caused the alloy to become embrittled.
Document ID
19870038074
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Cotell, Catherine M.
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Yurek, Gregory J.
(MIT Cambridge, MA, United States)
Date Acquired
August 13, 2013
Publication Date
December 1, 1986
Publication Information
Publication: Oxidation of Metals
Volume: 26
ISSN: 0030-770X
Subject Category
Metallic Materials
Accession Number
87A25348
Funding Number(s)
CONTRACT_GRANT: NSG-7648
Distribution Limits
Public
Copyright
Other

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