Synergistic Effect of Primary and Secondary γ′ Phases on the Deformation Behavior and Mechanism of Powder Metallurgy Nickel‐Based Superalloy

This study investigates the hot deformation behavior and microstructure evolution of a solution‐treated powder metallurgy nickel‐based superalloy using hot compression tests at 1000°C–1200°C and strain rates of 0.001–1 s −1 (50% deformation). The work aims to address the challenge of inhomogeneous deformation during the isothermal forging process of this alloy. The flow stress after peak stress exhibits three distinct types: fast dynamic softening (1000–1100°C/0.001–1 s −1 ), slow dynamic softening (1150°C/0.001–1 s −1 ), and balance of dynamic softening and work hardening type (1200°C/0.001–1 s −1 ). Microstructural analysis shows that the hot deformation behavior is therefore controlled by a synergistic effect between the primary γ′ and secondary γ′ phase, and the optimal hot deformation window for the alloy lies at 1150°C–1200°C and strain rates of 0.1–1 s −1 . With increasing temperature, the primary γ′ phase decreases in both area fraction and size. It enhances work hardening by hindering dislocation motion and promotes dynamic softening through particle‐stimulated nucleation. Meanwhile,the secondary γ′ phase, whose size decreases with the increase of temperature, larger secondary γ′ phase hinder dislocation motion to promote continuous dynamic recrystallization, whereas smaller ones facilitate dislocation slipping to promote discontinuous dynamic recrystallization.