In Situ Study of γ‐TiAl Lamellae Formation in Supersaturated α2‐Ti3Al Grains |
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Authors: | Limei Cha Thomas Schmoelzer Zaoli Zhang Svea Mayer Helmut Clemens Peter Staron Gerhard Dehm |
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Affiliation: | 1. Department of Physical Metallurgy and Materials Testing, Montanuniversit?t Leoben, 8700 Leoben, Austria;2. Materials Center Leoben Forschung GmbH, 8700 Leoben, Austria;3. Erich‐Schmid Institute of Materials Science, Austrian Academy of Sciences, 8700 Leoben, Austria;4. Institute of Materials Research, Helmholtz‐Zentrum Geesthacht, 21502 Geesthacht, Germany;5. Department of Materials Physics, Montanuniversit?t Leoben, 8700 Leoben, Austria |
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Abstract: | In situ heating transmission electron microscopy (TEM) was used to investigate the initial stage of γ‐TiAl lamellae formation in an intermetallic Ti–45Al–7.5Nb alloy (in at.%). The material was heat treated and quenched in a non‐equilibrium state to consist mainly of supersaturated, ordered α2‐Ti3Al grains. Subsequently, specimens were annealed inside a TEM up to 750 °C. The in situ TEM study revealed that ultra‐fine γ‐TiAl laths precipitate in the α2‐matrix at ≈730 °C which exhibit the classical Blackburn orientation relationship, i.e. (0001)α2//(111)γ and $11{\bar {2}}0$ ]α2//<110]γ. The microstructural development observed in the in situ TEM experiment is compared to results from conventional ex situ TEM studies. In order to investigate the precipitation behavior of the γ‐phase with a complementary method, in situ high energy X‐ray diffraction experiments were performed which confirmed the finding that γ‐laths start to precipitate at ≈730 °C from the supersaturated α2‐matrix. |
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