Dynamic softening behavior differences of high-temperature α and γ phases in β/γ-TiAl alloys at different strain rates

By precisely controlling the preheating duration, in this study, rational composition design and uniformization treatment processes of the as-cast state were employed to achieve nearly single-phase high-temperature α and γ phases in the β/γ-TiAl alloy during hot compression deformation. The dynamic softening behavior differences of the two typical phases were investigated at various strain rates. The results suggest that the degree of discontinuous dynamic recrystallization (DDRX) in the γ phase initially increases and then decreases with increasing strain rate during the hot compression process, gradually exhibiting characteristics of continuous dynamic recrystallization (CDRX). Simultaneously, the degree of dynamic recrystallization (DRX) in the high-temperature α phase initially decreases and subsequently significantly increases following a CDRX mechanism. In the high-strain rate (2.5 s⁻¹) hot compression process, the high-temperature α phase achieves significant CDRX through progressive lattice rotation, with a primary deformation mechanism transition from pyramidal and basal slip to prismatic and pyramidal slip. Compared with the γ phase, the high-temperature α phase, which has a lower deformation resistance and an enhanced degree of DRX and grain refinement, is more favorable during high-strain-rate hot compression deformation processes. This study establishes a theoretical foundation and application support for β/γ-TiAl alloys in high-strain rate thermoplastic deformation.