Hot deformation behavior of β phase containing γ-TiAl alloy

The hot deformation behavior of β containing γ-TiAl alloy with chemical composition of Ti-43.9Al-4.3Nb-0.9Mo-0.1B-0.4Si (at%) was investigated by means of uniaxial compressive tests in this paper. The tests were performed with a Gleeble 3500 simulator within a temperature range of 1100-1250 °C and a strain rate regime of 0.01-1 s−1 up to a true deformation of 0.7. The true stress-strain curves exhibited typical features of work hardening and flow softening. The peak stress of current alloy decreased with temperature and increased with strain rate, which can be described by a hyperbolic sine function of the Zener-Hollomon parameter (Z). The activation energy (Q) and stress exponent (n) were measured to be 540.28 kJ/mol and 2.82, respectively. Due to the addition of element Nb and Mo, and the formation of resultant β phase, this alloy possesses a wide hot-working window of temperatures above 1150 °C and strain rate under 0.5 s−1. Under a high Z or intermediate Z condition, dislocation climbing and twinning accompanied with the dynamic recrystallization (DRX) acted as the main deformation mechanism. Under a low Z condition, DRX became the dominant softening mechanism. A crack-free current alloy sheet was prepared by hot rolling at these optimized parameters.