Abstract:The fracture behavior at high temperatures of the Ti-22Al-26Nb alloy, which features duplex lamellar, bimodal, and Widmanst？tten structures, was studied. Samples of the alloy were prepared through compression deformation in the trans-phase region followed by subsequent heat treatment. The results indicate that at 650 °C, the fracture toughness of the Ti-22Al-26Nb alloy is increased by 41.7% compared to that with original microstructures. The content of the B2 phase significantly influences the inherent fracture toughness of the material, while the morphology and distribution of the precipitated phases primarily affect the tortuosity of the crack propagation path. Among the microstructural features, the morphology and geometric orientation of the lamellae most significantly impact the crack path; consequently, the Widmanst？tten structure exhibits the most tortuous fracture path. Additionally, a predictive model for fracture toughness is developed, which effectively predicts the fracture toughness of Ti-22Al-26Nb alloys with various microstructures at 650 °C.

Key words: Ti₂AlNb-based alloy; featured microstructures; fracture toughness prediction model; fracture mechanics