Structural characterization and tensile properties of a high niobium containing gamma TiAl sheet obtained by powder metallurgical processing

Ti–46Al–9Nb (at.%) alloy powders were produced by Argon gas atomization. The powder fraction <180 μm was hot isostatically pressed at 1270 °C and 190 MPa and the compacts were rolled to sheets with dimensions of about 600×300×1 mm3. The low oxygen (450 μg/g), nitrogen (70 μg/g) and argon (0.5 μg/g) concentrations in the sheets indicate that no impurity pick up occurred during processing. After a post rolling thermal treatment, the microstructure becomes “near gamma” showing an average γ-TiAl grain size of around 5 μm. Samples for tensile tests were prepared parallel and transverse to the rolling direction. At room temperature, high strength levels of up to 750 MPa (yield strength) and 2% plastic elongation were obtained. At 1000 °C the ultimate tensile strength was around 85 MPa and elongations to failure of up to 93% were obtained. The texture of the sheet exhibits a weak cube component with an alignment of [001] in transverse direction. The resulting anisotropy of the yield stress at 700 °C is small, with 5% higher strength in transverse direction.