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Microstructure and Property Change of Ti-49Al Induced by Hydrogen Charging

Published online by Cambridge University Press:  21 March 2011

E. Abe ,
K.W. Gao  and
M. Nakamura
E. Abe
Affiliation:
National Research Institute for Metals, 1–2–1 Sengen, Tsukuba 305–0047, JAPAN
K.W. Gao
Affiliation:
University of Science & Technology Beijing, Beijing, 100083, P.R. China.
M. Nakamura
Affiliation:
National Research Institute for Metals, 1–2–1 Sengen, Tsukuba 305–0047, JAPAN
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Abstract

We have investigated an effect of hydrogen gas-charging on the microstructure and the mechanical property of a Ti-49at.%Al alloy. After hydrogen-charging performed under an atmospheric pressure of hydrogen gas at 1023K for 3 hours, the alloy with γ-single phase has become completely brittle, while this hydrogen-induced embrittlement is suppressed for that with (γ+α2) two-phase microstructure composed of lath-precipitates in the γ matrix. A significant microstructural change was found to occur for the two-phase alloy (approximately 340ppm hydrogen in the alloy); a thin amorphous layers with a few nm thickness appear at the preexisting γ/α2 interfaces in the lath-precipitates after hydrogen-charging. In-situ TEM observation confirmed that the amorphous region transforms to a nano-crystalline state after heating to 1000K at which the hydrogen could be removed (degassed), indicating that the amorphous phase is not a binary Ti-Al phase but a ternary Ti-Al-H one. This, in turn, suggests that the γ/α2 interface in the lath packets act as the most preferential sites for hydrogen storage. Therefore, the scavenging is expected to occur effectively for the microstructure composed of γ-α2 fine lamellae in which a large number of γ/α2 interfaces exist. It is worthwhile mentioning that the fine-scale of the lamellae makes it possible to have a large number of interfaces for a given volume of the α2 phase.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 646 , 2000 , N7.3.1
Copyright
Copyright © Materials Research Society 2001

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References

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