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

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2017-06, Vol.697, p.132-140
• Main Authors: Sun, J.Z., Li, M.Q., Li, H.
• Format: Article
• Language: English
• Subjects: Beta phase; Continuous dynamic recrystallization; Deformation; Deformation mechanisms; Dynamic recovery; Dynamic recrystallization; Flow softening; Globularization; Grains; Hot working; Microstructure; Platelets; Recrystallization; Restoration; Restoration mechanisms; Softening; Strain rate; Stress-strain curves; Stress-strain relationships
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2017.04.107

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 0.0002s−1 to 0.1s−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.