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In Situ Study of γ‐TiAl Lamellae Formation in Supersaturated α 2 ‐Ti 3 Al Grains
Author(s) -
Cha Limei,
Schmoelzer Thomas,
Zhang Zaoli,
Mayer Svea,
Clemens Helmut,
Staron Peter,
Dehm Gerhard
Publication year - 2012
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201100272
Subject(s) - materials science , intermetallic , transmission electron microscopy , in situ , precipitation , supersaturation , alloy , microstructure , crystallography , electron diffraction , diffraction , metallurgy , nanotechnology , thermodynamics , chemistry , physics , meteorology , optics
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 α 2 ‐Ti 3 Al 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 α 2 ‐matrix at ≈730 °C which exhibit the classical Blackburn orientation relationship, i.e. (0001)α 2 //(111)γ and [ $11{\bar {2}}0$ ]α 2 //<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 α 2 ‐matrix.