Recrystallization of the hot isostatic pressed nickel-base superalloy FGH4096: I. Microstructure and mechanism

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 528; no. 28; pp. 8065 - 8070
• Main Authors: Ning, Yongquan, Yao, Zekun, Fu, M.W., Guo, Hongzhen
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25.10.2011; Elsevier
• Subjects: Activation energy; Applied sciences; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Cross-disciplinary physics: materials science; rheology; Dipping; Dislocations; DRX mechanism; Elasticity. Plasticity; Exact sciences and technology; Materials science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Microstructure; Nickel base alloys; Nickel-base superalloy; Nucleation; Physics; Recrystallization; Superalloys; Treatment of materials and its effects on microstructure and properties; Nickel-base superalloy; Microstructure; DRX mechanism; Recrystallization; Hot deformation; Nickel base alloys; Plastic flow; Compressive testing; Hot isostatic pressing; Dynamical recrystallization; Plastic deformation; Superalloys; Transmission electron microscopy; Activation energy; Transition element alloys
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2011.07.053

► Bulge corrugation (BC) and dislocation induce phase (DIP) nucleation are proposed. ► Recrystallization firstly occurs on previous particle boundary (PPB) by BC mechanism. ► DIP nucleation occurs during hot working below γ′ phase solution temperature. ► Activation energy of Q = 922 kJ/mol is determined. Hot isostatic pressed (HIPed) nickel-based superalloy FGH4096 behaves a unique flow behavior in hot compression process due to the formation of necklace microstructure and leads to its characteristic dynamic recrystallization (DRX). In this process, dislocations activate the occurrence of DRX at prior particle boundaries (PPB) and the PPB is entirely covered with DRX grains, which forms the first layer in necklace structure. In this paper, two nucleation mechanisms, viz., bulge corrugation (BC) nucleation and dislocation induce phase (DIP) nucleation, are proposed. Based on the proposed mechanisms, the recrystallization firstly occurs in PPB via BC mechanism. The DIP nucleation occurs when the hot plastic deformation is carried out at the temperature below the γ′ phase solution temperature. To verify the proposed mechanisms, hot compression experiments were conducted. The models are then verified based on the experiments. Furthermore, the recrystallization activation energy of 922 kJ/mol is determined, which includes the growth energy and the two nucleation energies, viz., BC and DIP nucleation energies.