Reaction process of {alpha} {yields} {gamma} massive transformation in Ti-rich TiAl alloy

Book · Tue Aug 01 04:00:00 EDT 1995

OSTI ID:78318

Kumagai, T; Abe, E; Nakamura, M ^[1]; Takeyama, M ^[2]

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1. National Research Inst. for Metals, Ibaraki (Japan)
2. Tokyo Inst. of Technology (Japan). Dept. of Metallurgical Engineering

Reaction sequence of the massive transformation from the high-temperature {alpha}-Ti phase to the {gamma}-TiAl phase ({gamma}{sub m}) 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 {alpha} 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 {gamma} 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 {gamma} and {alpha}{sub 2}-Ti{sub 3}Al phases, and the {gamma} plates were found to run through the TAPDs caused by {alpha} {yields} {alpha}{sub 2} ordering. Subsequent aging at 1,273 K causes the microstructure change in the untransformed region from {alpha}{sub 2}/{gamma} lamellae to {gamma}/{gamma} lamellae spontaneously and expands the {gamma}{sub m} region. These observations suggest that the {alpha} {yields} {gamma}{sub m} transformation proceeds through formation of fine {gamma} plates.

• OSTI ID: 78318
• Report Number(s): CONF-941144--; ISBN 1-55899-265-0
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CRYSTAL DEFECTS
CRYSTAL-PHASE TRANSFORMATIONS
EXPERIMENTAL DATA
GRAIN SIZE
INTERMETALLIC COMPOUNDS
TITANIUM BASE ALLOYS
TRANSMISSION ELECTRON MICROSCOPY