Dynamic recrystallization behavior of a γ′-hardened nickel-based superalloy during hot deformation

The hot deformation behavior of a gamma'-hardened nickel-based superalloy was investigated by means of isothermal compression tests in the temperature range of 1010-1210 degrees C with a strain rate of 0.1 s(-1). The electron backscatter diffraction (EBSD) technique and transmission electron microscope (TEM) were employed to investigate the effect of deformation temperature and strain on the microstructure evolution and nucleation mechanisms of dynamic recrystallization (DRX). Microstructure observations revealed that the size and volume fraction of DRX grains increased with the increasing temperature. A power exponent relationship was obtained between the stable DRX grain size and the peak stress. Additionally, it was found that the effect of CDRX characterized by progressive subgrain rotation became weaker with the increasing deformation temperature, and DDRX was the operating nucleation mechanism of DRX at higher deformation temperature. On the other hand, the effect of DDRX became stronger with the increasing strain, and CDRX can only be considered as an assistant nucleation mechanism of DRX at the later stage of deformation for the alloy deformed at 1160 degrees C. Nucleation of DRX can also be activated by the twinning formation. Hence, particular attention was also paid to the evolution of twin boundaries during hot deformation. (C) 2014 Elsevier B.V. All rights reserved.