Flow behavior and dynamic recrystallization of a power metallurgy nickel-based superalloy during hot compression in (γ + γ′)-phase region

Abstract

Flow behavior and dynamic recrystallization of a powder metallurgy EP962NP nickel-based superalloy in the (γ + γ′)-phase region have been investigated under the isothermal compression at 1075–1150 °C with strain rate of 0.0005–0.1 s−1. The results show that predicated solvus temperature of γ’ precipitates is as high as ~1196 °C. Flow stress behavior of experimental alloy exhibits typical characteristics of dynamic recrystallization (DRX) and can be well described by hyperbolic-sine Arrhenius-type model with a higher thermal deformation activation energy of 1181.7 kJ/mol. Discontinuous dynamic recrystallization can be identified as a dominant nucleation mechanism for DRX of the alloy, as evidenced by the prevalent observation of necklace structures. In addition, the refined recrystallized γ grains can be obtained with a higher strain rate due to the increasing deformation stored energy. During hot compression, the morphology of primary γ′ transforms from micron-scale irregular blocks to nano-scale spherical precipitates via the dissolution and re-precipitation process.