Dynamic recrystallization mechanisms and twining evolution during hot deformation of Inconel 718

Abstract

The hot deformation behavior of an IN718 superalloy was studied by isothermal compression tests under the deformation temperature range of 950–1100 °C and strain rate range of 0.001–1 s-1 up to true strains of 0.05, 0.2, 0.4 and 0.7. Electron backscattered diffraction (EBSD) technique was employed to investigate systematically the effects of strain, strain rate and deformation temperature on the subgrain structures, local and cumulative misorientations and twinning phenomena. The results showed that the occurrence of dynamic recrystallization (DRX) is promoted by increasing strain and deformation temperature and decreasing strain rate. The microstructural changes showed that discontinuous dynamic recrystallization (DDRX), characterized by grain boundary bulging, is the dominant nucleation mechanism in the early stages of deformation in which DRX nucleation occurs by twining behind the bulged areas. Twin boundaries of nuclei lost their ¿3 character with further deformation. However, many simple and multiple twins can be also regenerated during the growth of grains. The results showed that continuous dynamic recrystallization (CDRX) is promoted at higher strains and large strain rates, and lower temperatures, indicating that under certain conditions both DDRX and CDRX can occur simultaneously during the hot deformation of IN718.Peer ReviewedPostprint (author's final draft

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

“…(17), (18) and (19), it can be found that the influences of initial δ phase on DRX are comprehensively considered in Eq. (17). Therefore, the new developed DRX kinetic model shows the distinct advantages for predicting the DRX behavior of the studied superalloy at complicated aging conditions.…”

“…In recent years, numerous researches have been executed to study the high-temperature deformation behaviors [11,12], hot tensile fracture characteristics [13,14], microstructural evolution [15,16,17], and hot workability [18,19] of some typical superalloys. Lin et al [20,21,22] developed accurate phenomenological and physical-base constitutive models to predict high-temperature deformation behavior for GH4169 superalloy.…”

“…Mei et al [34] discussed analyzed the effects of cold rolling on the precipitation and the morphology of δ-phase in Inconel 718 alloy. Azarbarmas et al [35] clarified that DRX behavior is the dominant dislocation restoration mechanism for Inconel 718 superalloy.…”

In Situ Characterization of Inconel 718 Post-Dynamic Recrystallization within a Scanning Electron Microscope

“…Dynamic and post-dynamic recrystallization is among the most important phenomena impacting the microstructure of hot-forged components. The influence of the thermomechanical forging conditions on dynamic recrystallization (DRX) kinetics and on the DRX grain size is relatively well established [1][2][3][4][5][6][7][8], and can even be predicted using either physical or empirical models [9][10][11][12][13][14][15]. However, previous studies have shown that post-dynamic evolutions may also considerably impact the final microstructure [12,[15][16][17][18].…”

Forging Optimization and Microstructural Simulation of an Inconel 718 Alloy Used in Turbine Discs

“…These severe working environments require a proper forging of the disc to be performed. Grain size control in the forging of the Inconel 718 superalloy is a very important issue because the grain size is closely related to the mechanical properties and the performance of the discs [1] [2]. Na et al [3] studied the evolution of the microstructure in the process of two-step blade forging of 718 alloy using a 3D FE simulator that contained a microstructure module.…”