Improved dislocation density-based models for describing hot deformation behaviors of a Ni-based superalloy

Abstract

Generally, the obvious work hardening, dynamic recrystallization (DRX), and dynamic recovery behaviors can be found during hot deformation of Ni-based superalloys. In the present study, the classical dislocation density theory is improved by introducing a new dislocation annihilation item to represent the influences of DRX on dislocation density evolution for a Ni-based superalloy. Based on the improved dislocation density theory, the peak strain corresponding to peak stress and the critical strain for initiating DRX can be determined, and the improved DRX kinetics equations and grain size evolution models are developed. The physical framework and algorithmic idea of the improved dislocation density theory are clarified. Moreover, the deformed microstructures are characterized and quantitatively correlated to validate the improved dislocation density theory. It is found that the improved dislocation density-based models can precisely characterize hot deformation and DRX behaviors for the studied superalloy under the tested conditions.

Dislocation Based Flow Stress Model of 300M Steel in Isothermal Compression Process

“… where was the flow stress, a constant, the shear modulus, the Taylor factor, the Burgess vector, and the average dislocation density. In the recovery stage, the dislocation density increment ( ) could be described by the contradicting effects of the strain hardening ( ) which was caused by dislocation pile-ups and cross-slip, and the softening ( ) by creep and dynamic recovery dislocation annihilations by the Kocks-Mecking (KM) model [ 16 ]: where was dislocation increment by strain hardening, and was dislocation decrement by dynamic recovery, which followed [ 25 , 26 ]: where was the initial grain size, and coefficients, and the effective plastic strain increment. It was argued by researchers [ 27 , 28 ] that the dislocation-free recrystallized nuclei began to form and grow at grain boundaries under the driving force of grain boundary curvature and dislocations during dynamic recrystallization.…”

A new dynamic recrystallization kinetics model for a Nb containing Ni-Fe-Cr-base superalloy considering influences of initial δ phase

“…Lin et al [20,21,22] developed accurate phenomenological and physical-base constitutive models to predict high-temperature deformation behavior for GH4169 superalloy.…”

High Temperature Behaviors of a Casting Nickel-Based Superalloy Used for 815 °C

“…Zhang and Li [16] put an insight into the hot deformation behavior of In718 during isothermal compression deformation, it was concluded that the peak stress is decreased due to the absence of DRX. Lin et al [17] studied the effects of WH, DRV, and DRX work hardening (WH), dynamic recrystallization (DRX) and dynamic recovery (DRV) on high-temperature deformation behaviors of a typical Ni-based superalloy and proposed an improved dislocation densitybased model method to quantificationally describe the flow behaviors. Hence, giving a deeper insight into the hot deformation behavior is of great importance and in turn, guiding on the improved castability and moldability with optimized parameters.…”