On the Coupling between Recrystallization and Precipitation Following Hot Deformation in a γ-γ′ Nickel-Based Superalloy

Abstract

Post-dynamic recrystallization and γ' precipitation during cooling from γ' supersolvus temperature after hot compression have been studied in the AD730 TM γ-γ' Nickel-based superalloy. Emphasis was given not only on both phenomena as distinct mechanisms but also on their mutual influence in terms of physical mechanisms. The growth of γ'precipitates is hastened in the unrecrystallized grains compared to the recrystallized ones.This could possibly be attributed to the higher dislocation content acting as highdiffusivity paths. Post-dynamic recrystallization is not prevented by Smith-Zener pinning of the recrystallization front by the γ' precipitates. Instead, the recrystallization front dissolves γ' precipitates which then reprecipitate discontinuously or continuously, and coherently with the surrounding γ matrix in the recrystallized grains.

Microstructural engineering of medium entropy NiCo(CrAl) alloy for enhanced room and high-temperature mechanical properties

“…Here the migrating GBs assist the solute redistribution since the GBs are shown as fast diffusing paths for solutes as compared to the bulk lattice. Dissolution of precipitates during the migration of GBs is also observed and reported in several works [61][62][63][64][65][66][67][68] . Hence, the prior presence of precipitates will have an essential role in the recrystallization behavior.…”

Hot Deformation Behavior of a Powder Metallurgy Superalloy with High γ′ Content

“…Several studies have assessed the hot deformation of γ 0 strengthened superalloys, including γ 0 evolution mechanisms, recrystallization mechanisms, and their interactions. [17][18][19][20] PPBs also deserve attention, as fine powders promote the formation of PPB networks, [16,21] resulting in particle debonding and void formation during high-temperature deformation. [22,23] Thermomechanical processing determines the microstructure of the deformed superalloy, as the hot deformation behavior of superalloys is the result of The hot deformation behavior of a powder metallurgy superalloy EP741NP is studied using isothermal compression testing on a Gleeble-3500 thermomechanical simulator.…”

On the Evolution of Primary Gamma Prime Precipitates During High Temperature and High Strain Rate Deformation and Subsequent Heat Treatment in the Ni-Based Superalloy, RR1000

“…The evolution of the microstructure, i.e., specifically the c¢ precipitate morphology during these thermomechanical processes controls the grain size. [1][2][3][4] The grain size has a significant effect on the evolution of the flow stresses during forging. [2,[5][6][7][8][9][10] The evolution of the c¢ precipitate morphology is influenced by the stress, plastic strain, and most importantly the strain rate.…”

“…[2,[5][6][7][8][9][10] The evolution of the c¢ precipitate morphology is influenced by the stress, plastic strain, and most importantly the strain rate. [4,11,12] The 1st population termed as primary c¢ has the principal role of inhibiting grain growth during billet manufacture and forging by pinning the grain boundaries and are typically, 1 to 5 lm in size. [13] Thermomechanical operations carried out at temperatures where only these pinning particles are present in the microstructure (absence of secondary/tertiary populations, as they have lower solvus temperature compared to forging temperature) can be therefore carried out at decreased flow stresses.…”

“…At these high strain rates if DRX does not completely relax all the stress owing to the negligible deformation time (Dt~5 seconds and depending on the final plastic strain), reduction in the remnant dislocation density leads to meta-dynamic (post-dynamic) re-crystallization during cooling. [4,15] Furthermore, under such extreme deformation conditions, both the morphology and spatial occurrence of c¢ precipitates, i.e., inter/intragranular is determined by the strain rate. [12] The significance of studying the precipitate evolution under conditions of billet manufacture is key, since anomalous grain growth and existence of un-re-crystallized powder particles existing within the billet will affect both the flow stress and two-phase microstructure that evolves during forging, which can adversely affect the mechanical properties of the component.…”