Abstract:This study investigates the powder metallurgy superalloy FGH4113A, focusing on the design and implementation of precisely controlled cooling during the solid solution state. It examines the influence of different cooling paths on microstructural evolution and tensile properties at 800℃. The results demonstrate that the cooling path significantly affects the strength-ductility synergy. Employing a conventional continuous cooling rate of 150℃/min resulted in yield strength of 920 ± 7 MPa, an ultimate tensile strength of 1079 ± 9 MPa, and an elongation of 13 ± 3%. In contrast, a two-stage cooling process (CP2), combining an initial slow cooling (44~75℃/min) with a subsequent fast cooling (459~594℃/min), enhanced the yield and ultimate tensile strengths to 978 ± 7 MPa and 1112 ± 5 MPa, respectively, while also improving the elongation to 15 ± 1%. Further optimization of the process parameters to an initial cooling rate of 48~65℃/min followed by a second-stage rate of 275~326℃/min (CP3) achieved an elongation of 18.5 ± 1% while maintaining high strength levels (yield strength:975 ± 10 MPa, ultimate tensile strength: 1108 ± 6 MPa). Microstructural characterization reveled that the staged cooling strategy, which promotes dislocation recovery through high-temperature slow cooling and subsequently freezes the low-defect structure through medium-temperature fast cooling, effectively produces grain structures with low orientation spread and low dislocation density. Furthermore, analysis of γ" precipitation behavior indicated that the primary cooling rate governs the size of secondary γ" precipitates, while the cooling transition temperature regulates the volume fraction of tertiary γ" precipitates. The secondary cooling rate influences the size of the tertiary γ" precipitates. Through this multiscale cooperative distribution of γ" precipitates, moderately sized secondary γ" precipitates enhance strain hardening capacity by promoting the Orowan bypass mechanism, while the finely dispersed tertiary γ" precipitates compensate for the strength loss associated with coarsened secondary γ" precipitates through shearing mechanism. This work demonstrates that precisely controlled staged cooling is an effective pathway for synergistically optimizing the 800℃ strength and ductility of FGH4113A superalloy without altering its chemical composition, providing both a theoretical basis and practical guidance for the heat treatment design of this alloy.