Hot deformation behavior of a heat-resistant alloy without γ′-phase

The hot compression behavior of the nickel-based heat-resistant alloy C-HRA-2(R) was investigated by a Gleeble-1500 thermo-mechanical simulator with the deformation temperature range of 950-1150 degrees C and the strain rate of 0.001-10 s(-1). The constitutive equation of the alloy was established by using a hyperbolic sine function, and the peak stress followed a power law relationship with the Zener-Hollomon parameter (Z). The activation energy was about 446 kJ mol(-1) for the whole hot deformation domain in this alloy. The optimum hot deformation condition was obtained in the temperature range of 1050-1150 degrees C and the strain rate range of 0.005-0.1 s(-1). Unsafe domains during the hot deformation would occur in the strain rate range of 0.1-10 s(-1) with inhomogeneous microstructure and high-density twins in the alloy. The dominant nucleation mechanism of dynamic recrystallization (DRX) was continuous dynamic recrystallization with sub-grain rotation at high strain rate, while DRX at low strain rate was discontinuous dynamic recrystallization with original grain boundaries bulging.