XPS study of the initial stages of oxidation of a sub(2)-Ti sub(3)Al and g-TiAl intermetallic alloys

The initial stages of oxidation of a sub(2)-Ti sub(3)Al and g-TiAl alloys at 650 super(o)C under low oxygen pressure are shown to be characterized by three stages using XPS. Stage I is a pre-oxidation stage characterized by the adsorption and absorption of oxygen species. When the subsurface is satu...

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Bibliographic Details
Published in:Acta materialia 2007-06, Vol.55 (10), p.3315-3325
Main Authors: Maurice, V, Despert, G, Zanna, S, Josso, P, Bacos, M P, Marcus, P
Format: Article
Language:English
Subjects:
Alloys
Aluminum base alloys
Aluminum oxide
Nucleation
Oxidation
Oxides
Surface chemistry
X-ray photoelectron spectroscopy
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Summary:The initial stages of oxidation of a sub(2)-Ti sub(3)Al and g-TiAl alloys at 650 super(o)C under low oxygen pressure are shown to be characterized by three stages using XPS. Stage I is a pre-oxidation stage characterized by the adsorption and absorption of oxygen species. When the subsurface is saturated with dissolved oxygen (16 and 2at.% on a sub(2)-Ti sub(3)Al and g-TiAl, respectively), the selective oxidation of the alloy leads to the nucleation and growth of ultrathin (0.5 and 1.2nm on a sub(2)-Ti sub(3)Al and g-TiAl, respectively) alumina layers (stage II). The growth kinetics of the alumina layers is limited by the transport of Al in the alloy, leading to Al-depletion in the metallic phase underneath the oxide. When a critical concentration is reached (Ti sub(8) sub(2)Al sub(1) sub(8) and Ti sub(7) sub(5)Al sub(2) sub(5) on a sub(2)-Ti sub(3)Al and g-TiAl, respectively), titanium oxidation occurs (stage III). Ti(III) and Ti(IV) oxide particles are formed at the surface of the still growing alumina layer.
ISSN:1359-6454
DOI:10.1016/j.actamat.2007.01.030