Evolution characterization of α lamellae during isothermal compression of TC17 alloy with colony-α microstructure

The α lamellae evolution of TC17 alloy with colony-α microstructure during isothermal compression in α/β phase field was investigated via scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques. Special attention was paid to orientation evolution and α/α interfaces of the α lamellae. The results showed that the strain rate played a more significant role in the α lamellae evolution than the deformation temperature. The dynamic globularization via boundary grooving mainly characterized the α lamellae evolution at the strain rates of 0.01 s⁻¹ and 0.1 s⁻¹, and the high-angle boundaries (HABs) induced by the continuous dynamic recrystallization (CDRX) provided the main driving force for boundary grooving. The globularization fraction of α lamellae increased with the increasing of deformation temperature and decreasing of strain rate, in which the diffusion-controlled boundary grooving was enhanced. The α lamellae evolution at the strain rates of 1.0 s⁻¹ and 5.0 s⁻¹ was dominated by fragmentation, in which the localized shear flow driven by the synergistic effect of strain localization and inadequate dynamic recovery governed the fragmentation of α laths.