High-temperature Deformation Behavior and Properties of High Nb Containing TiAl Alloy

The high-temperature deformation behavior of high Nb containing TiAl alloy during step-by-step hot compression process was studied. Results show that the workability of high Nb containing TiAl alloy was improved after one hot compression deformation due to the increased volume fraction of equiaxed γ grains and α grains, as well as the decreased volume fraction and size of lamellar colony. Accordingly, based on the processing map and microstructure optimization, the optimal rolling process can be acquired as: the rolling process with strain rate lower than 0.5 s-1, deformation strain less than 25% in the early deformation stage and deformation temperature higher than 1150℃ was determined. Correspondingly, a large size of 600 mm×85 mm×3 mm high Nb containing TiAl alloy sheet with good surface quality and defect-free was successfully fabricated by hot pack rolling with 5 passes of large deformation rolling. The microstructure of the as-rolled high Nb containing TiAl alloy presented fine duplex microstructure with mean grain sizes of less than 5 μm. At room temperature, the as-rolled alloy exhibited yield strength, ultimate tensile strength and ductility as 948 MPa, 1084 MPa and 0.94%, respectively. The tensile strength at 800℃ also remained as high as 758 MPa. © 2022, Editorial Office of Chinese Journal of Materials Research. All right reserved.