Improved unified dislocation density-based constitutive model for high-temperature deformation and dynamic recrystallization behaviors of GH4698 superalloy

The high-temperature deformation and dynamic recrystallization (DRX) behaviors of GH4698 superalloy were investigated via hot compression tests, and an improved unified dislocation density-based constitutive model was established. The results indicate that with the temperature decreasing or the strain rate increasing, the flow stress increases and the DRX fraction decreases. However, as the strain rate increases from 1 to 10 s -1 , rapid dislocation multiplication and deformation heat accelerate the DRX nucleation, which further increases the DRX fraction. Discontinuous DRX nucleation is the dominant DRX nucleation mechanism, and continuous DRX nucleation mainly occurs under low strain rates. For the developed improved unified dislocation density-based constitutive model, the correlation coefficient, average absolute relative error, and root mean square error between the measured and predicted stresses are 0.994, 7.32% and 10.8 MPa, respectively. Meanwhile, the correlation coefficient between the measured and predicted DRX fractions is 0.976. These indicate that the developed model exhibits high accuracy in predicting the high-temperature deformation and DRX behaviors of GH4698 superalloy.