Microstructure evolution and its effect on flow stress of TC17 alloy during deformation in α+β two-phase region
(School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: The microstructure evolution and its effect on flow stress of TC17 alloy during deformation in the α+β two-phase region were investigated via microstructure characterization and isothermal compression tests. Results showed that the spheroidized rate of α phase at 820 and 850 °C slightly increased with increasing strain. With increasing deformation temperature, the spheroidized rate of α phase showed a slight increasing trend, but the volume fraction of α phase significantly decreased. The flow stress at 780 °C and 1 s-1 decreased continuously and steady state condition was not achieved up to strain of 1.2 due to dislocation annihilation and α lamellae rotation. Under this condition, the dynamic spheroidization was retarded. At the deformation temperatures of 820 and 850 °C, and a strain rate of 1 s-1, a steady state flow stress was observed at strains above 0.8 due to the balance between work hardening and dynamic softening. The dynamic softening was attributed to the α lamellae rotation, dynamic recovery and a little spheroidization.
Key words: TC17 alloy; spheroidized rate; microstructure evolution; flow stress; microstructure characterization