Hot deformation behavior and dynamic recrystallization mechanism of Ti-48Al-2Nb-2Cr with microstructure

Hot processing is extremely effective in optimizing the microstructure of gamma-TiAl alloy, and hot deformation mechanism is the decisive factor in the microstructure evolution. In this paper, hot compression tests under different conditions were carried out to investigate the characteristics of hot deformation behavior and deformation mechanism of Ti-48Al-2 Nb-2Cr alloy with near-gamma microstructure. The Arrhenius constitutive model was established, and the predicted flow stress agreed well with the experimental value. Hot pro-cessing maps at different strains were constructed. High power dissipation efficiency (n) region which was suitable for hot working appeared in the temperature range of 1180-1210 celcius and the strain rate range of 0.001-0.01 s-1. At the strain rates from 0.001 to 0.1 s-1, dynamic recrystallization (DRX) served as the primary softening mechanism of the alloy, which was closely related to the disordered transformation of u2 -> u. At the temperature above T 2 and the strain rate of 1 s-1, flow softening of the alloy was mainly controlled by dynamic recovery (DRV). The occurrence of DRX in the lamellar structure can be promoted by the elevated temperatures and reduced strain rates. Discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) appeared in the gamma and u/u2 phases of the alloy deformed at the conditions corresponding to high n region. With the decrease of n value, DRX nucleation of the alloy under the relevant conditions was chiefly dominated by DDRX.(c) 2023 Elsevier B.V. All rights reserved.