Temperature dependence of tensile deformation behaviors in a novel powder metallurgy Ni-based superalloy with high density nanoscale γ′ phase

High-temperature tensile property is a key indicator for evaluating the mechanical properties of powder metallurgy (PM) Ni-based superalloys under long-term service and high-temperature conditions. This study investigates the relationship between the tensile properties, deformation mechanisms, and fracture modes of FGH4113A superalloy at room temperature (RT), 550 °C, 650 °C, 750 °C, and 850 °C. The results show that as the temperature increases to 850 °C, elevated-temperature grain boundary oxidation drives a transition in the fibrous zone fracture mode from transgranular ductile to intergranular fracture, thereby progressively reducing elongation. However, the plastic deformation mechanism changes from the high-density, strongly coupled dislocation array formed slip bands at RT to the stacking fault (SF) shear mechanism at 550–750 °C and the deformation twinning mechanism at 850 °C. Ultimate tensile strength (UTS) and yield strength (YS) exhibit a non-monotonic trend of initially decreasing (RT-650 °C), followed by anomalous strengthening (650–750 °C), and finally decreasing again (750–850 °C). The yield strength anomaly (YSA) at 750 °C is primarily due to the high temperature promoting the increased decomposition of dislocations, leading to the formation of a high-density SF network and Lomer-Cottrell (L-C) locks, significantly improving the alloy's strength.