Spheroidization and dynamic recrystallization mechanisms of a novel HIPed P/M superalloy during hot deformation.

The spheroidization behavior of γ′ phase and dynamic recrystallization (DRX) mechanisms of a novel HIPed powder metallurgy (P/M) superalloy deformed at high temperatures (1080−1170 ℃) and different strain rates (1–0.001 s−1) are investigated. The results show that the spheroidization behavior of γ' phase and DRX mechanisms are greatly influenced by deformation condition. The coarse γ′ Ⅰ phase promotes the DRX process, while the fine spherical γ' Ⅲ phase results in the formation of sub-grain boundaries. Thus, the grains are refined. During hot deformation, some coarse γ′ Ⅰ and γ′ ⅠⅠ phases transform into the fine spherical γ' Ⅲ phases, while some initial γ' Ⅲ phases gradually diminish. Besides, the spheroidization rates of γ′ Ⅰ , γ′ Ⅱ and γ' Ⅲ phases increase with the increase of strain rate. The low DRX volume fraction and refined grains with the average size of 2.27 µm are obtained at 1110 ℃/1 s−1. It is attributed to the fact that the DRX nucleation is obviously enhanced and the pinning effects of spherical γ′ Ⅲ phases on dislocations accelerate the formation of sub-grains. In addition, the discontinuous DRX is the main DRX mechanism of this novel P/M superalloy. • Spheroidization and DRX mechanisms of a novel HIPed P/M superalloy during hot deformation is studied. • The coarse γ′ Ⅰ phase promotes the DRX by inducing the dislocation accumulation. • The fine spherical γ' Ⅲ phases result in the formation of sub-grain boundaries and the grains are refined. • Some coarse γ′ Ⅰ and γ′ ⅠⅠ phases transform into the fine spherical γ' Ⅲ phases during hot deformation. • The discontinuous DRX is the main DRX mechanism of this novel P/M superalloy. [ABSTRACT FROM AUTHOR]