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Microstructure of Massively Transformed γ-TiAl Phase Studied by High-Resolution Electron Microscopy

Published online by Cambridge University Press:  15 February 2011

E. Abe,
T. Kumagai,
S. Kajiwara and
M. Nakamura
E. Abe
Affiliation:
National Research Institute for Metals, Sengen, Tsukuba 305, Japan, abe@tamamori.nrim.go.jp
T. Kumagai
Affiliation:
National Research Institute for Metals, Sengen, Tsukuba 305, Japan, abe@tamamori.nrim.go.jp
S. Kajiwara
Affiliation:
National Research Institute for Metals, Sengen, Tsukuba 305, Japan, abe@tamamori.nrim.go.jp
M. Nakamura
Affiliation:
National Research Institute for Metals, Sengen, Tsukuba 305, Japan, abe@tamamori.nrim.go.jp
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Abstract

A microstructure of the massively transformed γ-TiAl (γm) phase in a Ti-48at.%Al alloy, which was heat treated in the high-temperature α-Ti (disordered hep) single phase field (1683K), followed by ice water quenching, has been examined using high-resolution electron microscopy. The characteristic features of the microstructure originated from the α→γ massive transformation have been clarified in detail, which are as follows. (1) Extremely thin hep plates (about 0.8–2nm in thickness), which are considered to be a retained α phase, are found to exist in the γ m phase. (2) Twin boundaries are found to be not flat interfaces, that is, twin interfaces are not on the exact (111) mirror plane. This situation is attributed to the existence of a number of partial dislocations at the twin boundaries. (3) Antiphase relationship between the regions either side of the thin rotated domain wall [1] is confirmed. The validity of this situation is explained by assuming that the thin rotated domain wall has been grown from a simple antiphase domain boundary. On the basis of these facts, mechanism of the α→γ massive transformation has been discussed.

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References

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