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

The alpha lamellae evolution of TC17 alloy with colony-alpha microstructure during isothermal compression in alpha/beta 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 alpha/alpha interfaces of the alpha lamellae. The results showed that the strain rate played a more significant role in the alpha lamellae evolution than the deformation temperature. The dynamic globularization via boundary grooving mainly characterized the alpha 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 alpha lamellae increased with the increasing of deformation temperature and decreasing of strain rate, in which the diffusion-controlled boundary grooving was enhanced. The alpha 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 alpha laths.