Flow characteristics and intrinsic workability of IN718 superalloy

Abstract

a b s t r a c tThis study focuses on deformation characteristics of superalloy IN718 by formulation of a new flow stress model and detailed evaluation of intrinsic workability through the generation of three-dimensional (3D) processing maps with the support of optical microstructural observations. Based on thermomechanical simulation tests using a Gleeble-1500 machine, the flow stress model for superalloy IN718 was built and the flow stress throughout the entire deformation process was described by a peak stress only depending on Zener-Hollomon parameter and strain. The developed model exhibited the strain softening due to dynamic recrystallisation (DRX). The intrinsic workability was further investigated by constructing 3D processing maps. The 3D processing maps described the variations of the efficiency of power dissipation and flow instability domains as a function of strain rate, temperature and strain, from which the favourite deformation conditions for thermomechanical processing of IN718 can be established.

Study of Flow Softening Mechanisms of a Nickel-Based Superalloy With Δ Phase

“…Because there is no enough time for deformation heating to dissipate at high strain rate, the local temperature of deformed block sharply increases. Thus, flow localization occurs [26]. Besides, it can be found that there are a large amount of δ phases in grain interior and boundaries at the strain rate of 1 s -1 , as shown in Fig.…”

“…Besides, it can be found that there are a large amount of δ phases in grain interior and boundaries at the strain rate of 1 s -1 , as shown in Fig. 10. δ phases, typical second-phase particles, can act as the geometric barrier to inhibit dislocations movement [26,52], which will result in the decreased flow softening degree. It is well known that the stresses for dislocations to overcome the further movement are mostly affected by the volume fraction and mean particle radius of second-phase particles.…”

“…In their proposed models, material constant are expressed as functions of the initial content of δ phase. On the other hand, Wen et al [25], Chen et al [26], Zhang et al [27], and Jiang et al [28] developed the processing maps of some nickel-based superalloys, and the optimized processing parameters were obtained. Besides, Lin et al [29] found that the discontinuous dynamic recrystallization plays a major role on the nucleation of dynamic recrystallization (DRX) during the hot deformation of GH4169 superalloy.…”

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

“…Chen et al [36] established three-dimensional processing maps to assess the hot workability of Inconel 718 superalloy. Liu et al [37] discussed the effects of strain rate and deformation temperature upon hot workability of FGH4096 superalloy.…”

Mesoscale modeling and simulation of microstructure evolution during dynamic recrystallization of a Ni-based superalloy

“…The mechanical properties of forgings are extremely sensitive to the dynamic and interconnected variables, such as strain, strain rate and temperature [20]. Therefore, in recent years, the flow behaviors and microstructural evolution of IN718 have been studied experimentally by many researchers [21][22][23][24][25][26]. However, there have been few investigations on modeling and simulation of microstructure evolution for IN718 superalloy during hot working.…”