Synergistic effects of cryogenic rolling and aging treatments on microstructure and mechanical properties of GH4169 superalloy

Abstract

This study investigates the interplay between cryogenic rolling (at liquid nitrogen temperature) and aging treatments on the microstructure and mechanical properties of GH4169 superalloy. Cryogenic rolling with 20% deformation was conducted at -50°C, followed by solid solution treatment and multi-step aging at 980°C, 720°C, and 620°C. Subsequent aging at 720°C produced a homogeneous distribution of nanoscale γ′ (5–10 nm) and γ′′ (10–20 nm) precipitates, which synergized with residual dislocations and twins to optimize strength and ductility balance. The cryogenically rolled and 720°C aged sample achieved the highest yield strength (953 MPa) and ultimate tensile strength (1136 MPa) while retaining 13.4% elongation, outperforming non-rolled counterparts. In contrast, high-temperature aging (980°C) promoted coarse η precipitates, reducing ductility, while low-temperature aging (620°C) led to insufficient precipitation. Microstructural analysis demonstrated that cryogenic deformation lowered the activation energy for precipitate nucleation, enabling Orowan and Hall-Petch strengthening mechanisms. Annealing twins further subdivided grains and amplified work hardening via twin-precipitate interactions. This work establishes a processing framework for GH4169 superalloy, emphasizing the critical role of cryogenic rolling in tailoring precipitation kinetics and deformation substructures for superior cryogenic performance.