Directional Atomic Rearrangements During Transformations Between the α- and γ-Phases in Titanium Aluminides

Making movies in-situ at glowing temperatures up to 1300°C through a microscope (false color image) and from two-dimensional X-ray diffraction (movie frames) reveal the lattice correlations, gradients and intermediate structures during phase transformations in titanium aluminide. A quenched, α 2 -rich γ-based TiAl first approaches its equilibrium by α 2 → y on a heating ramp, disorders α 2 → a and then evolves reversely y → a, which are morphologically different processes.