On the Temperature‐Induced Equilibration of Phase Distribution and Microstructure in a Gas‐Atomized Titanium Aluminide Powder

• Published in: Advanced engineering materials Vol. 25; no. 6
• Main Authors: Musi, Michael, Clemens, Helmut, Stark, Andreas, Spoerk-Erdely, Petra
• Format: Journal Article
• Language: English
• Published: 01.03.2023
• Subjects: microstructure; phase transformations; powder processing; synchrotron radiation; titanium aluminides
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.202201242

Powder production by gas atomization of γ‐TiAl based alloys typically yields a highly nonequilibrium material regarding the occurring phases and their microstructural appearance. In particular, the equilibration of the powder and the associated phase transformations during heating are of great importance for the subsequently applied densification techniques. The present work employs in situ high‐energy X‐ray diffraction to investigate how this thermodynamic equilibration manifests itself in the resulting phase distribution, the ordering behavior of the disordered α and β phase, both evidenced in the powder, and the change of the γ lattice parameters during heating of a Ti–46.3Al–2.2W–0.2B (at%) powder up to 850 °C. Complementary microstructural characterization of the gas‐atomized powder and the heat‐treated material condition reveals that the temperature exposure predominately affects the dendritic parts of the microstructure, especially when the α phase is transformed into γ phase with small embedded grains of α2 and βo. In situ investigations reveal an equilibration of a gas‐atomized W‐containing γ‐TiAl based powder upon heating between 600 and 850 °C. This equilibration comprises the ordering of the disordered phases and the change of the predominant phase from α‐Ti(Al) to γ‐TiAl. The formation of γ phase only affects the microstructure of the Al‐lean regions of the powder particles.