本团队博士生温红宁等在Materials Science and Engineering: A发表研究论文。

摘要：A novel P/M nickel-based superalloy is developed with an excellent combination of strength and ductility for use in turbine disks. This superalloy is prepared through hot isostatic pressing (HIP) and subsequent hot extrusion (HEX) with different extrusion ratios (λ). The effects of λ on the evolution and mechanism of γ′ precipitation behavior, grain refinement, microtexture, and mechanical properties are systematically studied. As λ increases, the primary γ′ phase fraction decreases from 17.22% to 8.47%, and the precipitation morphology changes from an irregular to a spherical shape. Increasing λ is beneficial to dynamic recrystallization. Fully recrystallized fine grains with a diameter of 4.47 μm are obtained at an optimal λ = 5.0, a decrease of 76% compared with the HIPed alloy. Abnormal grain coarsening was observed at a higher λ with 8.5 owing to the lack of γ′ pinning and a stronger driving force for grain boundary migration induced by deformation heat. The yield strength (YS) and ductility of the HEXed alloy are over 30% higher than those of the HIPed alloy, thanks to refined grains and the γ′ phase. The alloy extruded with λ of 5.0 exhibits a high YS of 1376 MPa with a ductility of 22.6% at room temperature and a YS of 1208 MPa with a ductility of 18.3% at 700 °C, which are better than those of other superalloys. A multi-mechanistic strengthening model is constructed by correlating the chemical composition, size and fraction of γ′, grain size, and YS. The calculations suggest that precipitation strengthening contributes more than 60% of the YS. Extrusion can dramatically enhance the YS of the superalloy owing to the increment of grain boundary strengthening and precipitation strengthening. This work provides a practical route and theoretical support for optimizing microstructure and enhancing the mechanical properties of a HIPed P/M nickel-based superalloy.