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Reaction Process of αəγ Massive Transformation in Ti-Rich TiAl Alloy

Published online by Cambridge University Press:  22 February 2011

T. Kumagai ,
E. Abe ,
M. Takeyama  and
M. Nakamura
T. Kumagai
Affiliation:
National Research Institute for Metals, Tsukuba-shi, Ibaraki 305, Japan
E. Abe
Affiliation:
National Research Institute for Metals, Tsukuba-shi, Ibaraki 305, Japan
M. Takeyama
Affiliation:
Department of Metallurgical Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo 152, Japan
M. Nakamura
Affiliation:
National Research Institute for Metals, Tsukuba-shi, Ibaraki 305, Japan
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Abstract

Reaction sequence of the massive transformation from the high-temperature α-Ti phase to the γ-TiAl phase (αm) in a Ti-48at.% Al alloy has been examined in terms of optical and transmission electron microscopes. Both transformed and untransformed regions were macroscopically observed in the sample quenched from the high-temperature α phase field, when the sample was held there for a extended period of time prior to quenching. The transformed region consists of randomly oriented fine α single phase grains, in which many thermal anti-phase domains (TAPDs), together with a number of stacking faults were observed. In contrast, the untransformed region comprises extremely fine lamellae of the α and α2-Ti3Al phases, and the α plates were found to run through the TAPDs caused by α ə α2 ordering. Subsequent aging at 1273K causes the microstructure change in the untransformed region from α2/γ lamellae to γ/γ lamellae spontaneously and expands the γm region. These observations suggest that the α ə γm transformation proceeds through formation of fine γ plates.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 364: Symposium L – High-Temperature Ordered Intermetallic Alloys–VI , 1994 , 181
Copyright
Copyright © Materials Research Society 1995

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