The cavitation of high Nb-containing TiAl alloys during tensile tests around BDTT

To understand the fracture behavior and cavity evolution of high Nb-containing TiAl alloys, tensile tests were conducted at low strain rates and various temperatures around brittle to ductile transition temperature (BDTT). Then, the fracture morphology and cavitation behavior were investigated. The results show that cavitation occurs above BDTT as the fracture mode changes from cleavage fracture to ductile fracture. And the cavitation of this alloy is dominated by diffusion-controlled cavity nucleation, which is promoted at higher temperature. The growth and coalescence of cavities are correlated with heterogeneous deformation and facilitated at higher strain rate. The cavity growth and coalescence are accelerated at boundaries between hard and soft orientated lamellar colonies due to the strain incompatibility. Additionally, β/B2 phase may facilitate the cavity nucleation due to its high diffusivity. These findings may provide important implications for optimizing the hot-working processing of high Nb-containing TiAl alloys.