Enhancing the hot-working capability of TiAl intermetallics via innovative microstructural design

The poor hot workability of TiAl intermetallics, stemming from their high dynamic recrystallization (DRX) temperature and sluggish atomic diffusion, severely limits their application in aerospace structural components. Here, this work introduced a novel three-phase bimodal (T-B) structure achieved through triggering the cellular reaction of full lamellar microstructure, to overcome this challenge. The T-B structure lowers the DRX temperature by at least 250 °C compared to conventional microstructures in TiAl intermetallics, enabling crack-free compression at 800 °C with 60 % strain—a first for TiAl intermetallics. Notably, ultrafine grains (0.8 μm) are achieved through low-temperature thermal compression, offering unprecedented opportunities to tailor mechanical properties. It is revealed that the pearlitic-like microstructure within the T-B structure exhibits exceptional strain-hardening capacity, generating a much higher density of dislocations during hot deformation. The higher density of dislocations serves as a potent catalyst, supplying abundant driving force and ultra-fine nuclei to facilitate DRX while eliminating stress concentration at significantly reduced temperatures. Furthermore, twin-induced and grain boundary-induced DRX mechanisms are unraveled during deformation at lower temperature, highlighting the grain refinement mechanism induced by the two DRX process. Finally, a novel low-temperature thermoforming process (800–1000 °C) is proposed, circumventing the need for β -stabilizing elements and reducing oxidation risks. This work not only advances the fundamental understanding of DRX in ordered intermetallics but also provides a new pathway to improve the manufacturing process of TiAl components. • Novel three-phase bimodal microstructure enables record-low 800°C DRX in TiAl, cutting threshold by 250°C vs conventional. • Ultrafine grains (0.8 μm) were synthesized for the first time in TiAl alloys through low-temperature thermal compression. • Twin/GB-induced DRX mechanisms elucidated: Nanotwins partition grains; Dislocations triggered subgrains→equiaxed transformation. • A novel low-temperature thermoforming process (800–1000 °C) is proposed, avoiding the need for β-stabilizing elements.