Room temperature and high temperature tensile behavior of a novel P/M nickel-based superalloy treated by solid solution and aging heat treatment

The as-forged microstructure of the novel P/M nickel-based superalloy contains coarse primary γ′ and irregular secondary γ′, leading to poor mechanical performance. Here, post-solution cooling routes (oil, air, and furnace cooling) were varied followed by an identical aging treatment to tailor the size, morphology, and distribution of γ′. Tensile tests were conducted at room temperature and 550−850 °C to evaluate the temperature dependence of strength and ductility. Pronounced serrated yielding occurred at 550 and 650 °C, with dense stress oscillations immediately after yielding, consistent with type-A dynamic strain aging. The alloy maintained high strength at 750 °C (YS = 1114 MPa; UTS = 1271 MPa) and exhibited smooth flow without serrations. At 850 °C, The fracture mechanism is intergranular brittle fracture. Microstructural showed that decreasing the post-solution cooling rate coarsened γ′ and reduced γ/γ′ interfacial density, lowering room-temperature strength but improving ductility. The serrated flow at 550−650 °C is ascribed to solute-related dynamic aging together with dislocation pinning by γ′ and carbides. At 750 °C, the alloy exhibits smooth flow without serrations because the testing condition lies outside the Portevin−Le Chatelier (PLC)/DSA instability window. And the γ′ shearing and SF formation still operate, but the solute dislocation interaction no longer produces intermittent pinning-unpinning events required for PLC. The 850 °C embrittlement with intergranular brittle fracture is primarily caused by oxidation-assisted grain-boundary degradation, with reduced slip compatibility as a secondary accelerating factor. These results inform microstructure optimization and reliability assessment of P/M nickel-based turbine-disk alloys across the relevant service temperature.