In Situ Study of γ-TiAl Lamellae Formation in Supersaturated α2-Ti3Al Grains

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//