A novel short-process manufacturing method of γ′-strengthened superalloy: Modulation of nano-scaled γ′ precipitates during hot deformation

Abstract

The tailoring of precipitates during hot deformation provides an opportunity to eliminate lengthy post-process heat treatment and removes the inherent disadvantages, such as abnormal grain growth. In this work, a novel short-process manufacturing method consisting of only pre-annealing and hot deformation steps was proposed for fabricating γ′-strengthened GH4720Li superalloy. Diverse nanoscale precipitation strengthening phases with bimodal distributions but similar matrix grain sizes were successfully modulated by this integrated two-step manufacturing method. The modulated superalloys fabricated under low deformation resistance and without typical long-time aging treatment exhibited high yield strength (∼1196 MPa) and ultimate tensile strength (∼1561 MPa) while maintaining a decent uniform elongation (∼19%) during tensile tests at room temperature. The dominant tertiary γ′ strengthening precipitates originate from the supersaturated matrix and dynamic evolution of secondary γ′ precipitates during hot deformation. In addition, the shearing of secondary γ′ through dislocation pairs promotes their dissolution during hot deformation. This study provides a novel pathway for the integrated short-process manufacturing of multimodal γ′ nickel-based superalloys and a new understanding for dynamically modifying the microstructure of precipitate-containing alloys during hot deformation.