In this study, an easily controlled transformation similar to the β + α → β + α + γ and the analysis of metastable phases in a β solidifying Ti-44.5Al-8Nb-2.5V alloy were investigated. Therefore, a liquid alloy copper-quenching followed by annealing at an application temperature (850 °C) has been carried out. Following quenching, a microstructure composed of several supersaturated phases—the basket-weave β₀ (β_bv) phase, the plate-like α₂ (α_p) phase and the stripe-like γ (γ_s) phase—was obtained. In the annealing processes, phase transformations in the prior β_bv and α_p phases domain corresponded nicely to the β + α → β + α + γ transformation during solidification. Also, in the annealed γ_s phase, the kinetics of the phase transformations involving the metastable L1₂ phase was firstly detected by transmission electron microscopy (TEM). The L1₂ phase had a lattice structure similar to the γ phase, whereas the composition of the phase was similar to the α₂ phase. The formation of the γ pre-twin phase with an anti-phase boundary (APB) was detected in the γ_s phase of the matrix. The orientation relationships between the γ_s and precipitated: γ (γ_p) phase are <101]γ_s//<114]γ_p, (10 $\overline{1}$ )γ_s//( $\overline{1}$ 10)γ_p and (0 $\overline{1}$ 0)γ_s//(22 $\overline{1}$ )γ_p.

TiAl alloys are high-temperature structural materials with excellent comprehensive properties, and their ideal service temperature range is about 700–950 °C. High-Nb containing the Ti-46Al-8Nb-2.5V alloy was subjected to hot compression and subsequent annealing at 900 °C. During hot compression, work-hardening and strain-softening occurred. The peak stresses during compression are positively correlated with the compressive strain rates and negatively correlated with the compression temperatures. The α₂ phase exhibited a typical (0001)α₂ basal plane texture after hot compression, while the β₀ and γ phases did not show a typical strong texture. Subsequent annealing at 900 °C of the hot-compressed samples resulted in significant phase transformations, specifically the α₂ → γ and β₀ → γ phase transformations. After 30 min of annealing, the volume fraction of the α₂ phase decreased from 39.0% to 4.6%. The microstructure characteristics and phase fraction after 60 min of annealing were similar to those after 30 min. According to the calculation of Miller indexes and texture evolution during annealing, the α₂ → γ phase transformation did not follow the Blackburn orientation relationship. Multiple crystal-oriented α₂ phases with nanoscale widths (20~100 nm) precipitate within the γ phase during the annealing process, which means the occurrence of γ → α₂ phase transformation. Still, the γ → α₂ phase transformation follows the Blackburn orientation relationship.