Flow softening mechanismin isothermal compression of β-solidifying γ-TiAl alloy

Flow softening mechanism in the isothermal compression of Ti-42.9Al-4.6Nb-2Cr with duplex structure was investigated. True stress-strain curves of Ti-42.9Al-4.6Nb-2Cr exhibited evident flow softening behavior when isothermal compression was conducted at the strain rate of 0.001-1.0 s(-1), and the flow softening effect was assessed via flow softening index. Results show that kinking of alpha(2)/gamma lamellar colonies and periodic morphology variation of beta(0) phase mainly contributed to the initial flow softening, while DRX of gamma phase and periodic morphology variation of beta(0) phase contributed to the lateral flow softening of Ti-42.9Al-4.6Nb-2Cr with duplex structure. Kinking of lamellar colonies was caused by appearance of stacking faults pairs in gamma lamellae and fracture of alpha(2) lamellae. Lamellar colonies were decomposed by DRX of gamma phase and growth of adjacent lamellae in the kinked area. Additionally, periodic morphology variation of beta(0) phase was related to intensive deformation systems, which can be easily-activated, and fast DRX behavior via rotation of subgrains during isothermal compression. (c) 2019 The Authors. Published by Elsevier Ltd.