Initial flow softening and restoration mechanisms of isothermally compressed Ti-5Al-2Sn-2Zr-4Mo-4Cr with basketweave microstructure

The initial flow softening behavior and restoration mechanisms of Ti-5Al-2Sn-2Zr-4Mo-4Cr with basketweave microstructure during hot working were investigated. The stress-strain curves presented an obvious flow softening behavior at the range of strain rates from 0.0002 s⁻¹ to 0.1 s⁻¹. The dynamic recovery (DRC) in α and β phases was responsible for the initial flow softening rather than the rotation of α platelets to a “soft” orientation. Following this continuous dynamic recrystallization (CDRX) of α and β phases based on the DRC is the main restoration mechanism related to the following flow softening. CDRX, as the first step of fragmentation of α phase, resulted in the globularization of α platelets. The globularization fraction of α platelets increased with decreasing strain rates and rising deformation temperatures since the CDRX of α phase and the penetration of β phase were the diffusion-controlled process accelerated by the higher deformation temperatures and longer diffusion time. Furthermore, the CDRX of β grains was always linked to the kinked sharp α grains in order to coordinate the deformation from α phase.