Abstract A high-performance TiAl-Nb alloy was obtained by forging and heat treatment. The tensile properties of the alloy were tested, and the microstructure of the alloy was observed via transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). The results revealed that after the alloy undergoes tensile fracture at the temperature of 820 °C, the yield strength was 420 Mpa and the elongation rate is 3.6 %. After tensile fracture at 880 °C, the yield strength of the alloy was 340 Mpa and the elongation rate is 9.8 %.The brittle-ductile transition temperature (BDTT) of the alloy ranged from 820 °C to 880 °C. In the brittle fracture process, the alloy fractures by a mixed mode of lamellar fracture and lamellar colony boundary fracture. In lamellar colonies, cracks propagate mainly along the γ / γ interface. Among the lamellar colony boundaries, the passivated serrated lamellar colony boundary has better crack propagation resistance than the straight strip lamellar colony boundary. In the process of plastic fracture, lamellar colony boundary fracture is the main damage mechanism. The repeated recrystallization of γ grains and abundant B2 phase that precipitates within and between lamellar colonies are the main reasons for the formation and propagation of cracks.
Tian et al. (Thu,) studied this question.