Consideration of recrystallization modeling of γ/γ’-strengthened Ni-based superalloys at sub-solvus temperatures

Abstract

New Ni-based superalloys and methods for controlling their microstructures have recently received much investigation to further improve their high-temperature properties, sometimes via control of precipitates such as γ’ (Ni₃(Al,Ti,Nb,Ta)) and γ″ (Ni₃Nb). In Ni-based superalloys, fine grains favor deformability and mechanical properties; therefore, control of grain size, achieved by recrystallization, is also important. Some new studies have reported the pinning effects of coarse γ’. However, few studies have investigated modeling methods for recrystallization behaviors. Difficulties in grain size and phase distribution control have hindered fabrication by open-die forging utilizing the pinning effect of the γ#x2019; phase. Therefore, this study examines the recrystallization behaviors of Ni-based superalloys containing coarse primary γ’ precipitates and considers applicable modeling methods. The recrystallization behaviors at sub-solvus temperatures are investigated in a new Ni-based superalloy with abundant coarse γ’ precipitates. Grain growth is limited by the pinning effect of coarse γ’ and the recrystallized grain size corresponds to increasing applied strain. Dynamic and static recrystallization is promoted by high strains and high temperatures. The kinetics of the recrystallized area fraction and recrystallization grain growth influenced by the pinning effect of coarse γ’ is modeled by Zurob’s method.