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Initial stages of oxidation of Ti45Al7Nb0.4Y alloy at 900 °C in air

Published online by Cambridge University Press:  31 January 2011

G.L. Chen
Affiliation:
State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
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Abstract

The initial stage of oxidation of Ti45Al7Nb0.4Y alloy (at.%) oxidized at 900 °C in air was investigated by using x-ray photoelectron spectroscopy and Auger electron spectroscopy. Experimental results revealed that YAl2 segregated along the grain boundaries preferentially oxidized to Y2O3 and Al2O3 due to strong affinity of Y to oxygen. Oxides grew faster at the grain boundaries than in lamellar colonies. As a result, Y and Al oxides pegs protruded into the substrate, which can increase the contact areas of oxide scale and substrate. Moreover, inward diffusion of oxygen more easily occurred along the grain boundaries. As a result, it promoted the external oxidation of Al within the grains due to lower inward diffusion flux of oxygen. And coarse-grained Y2O3 blocked the cationic intergranular diffusion. Therefore, Y addition can effectively enhance the Al2O3 layer and suppress the TiO2 outermost layer.

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Articles
Copyright
Copyright © Materials Research Society 2010

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