Abstract:FGH4097 and GH4079 alloys were prepared by powder metallurgy and wrought processes, respectively. The experimental results show that the grain size of FGH4097 superalloy is smaller and has more uniform distribution compared with that of GH4079 superalloy, with the former having a grain size of approximately ASTM grade 6.0 to 6.5 and the latter having a grain size of approximately ASTM grade 4.5 to 5.0. The size of the γ′ strengthening phase in FGH4097 superalloy is larger than that in GH4079 superalloy, with secondary γ′ phase being mostly cubic and having an average size of about 0.48 μm in FGH4097 superalloy, whereas in GH4079 superalloy, the secondary γ′ phase is mainly near-spherical with an average size of about 0.14 μm. Comparing the tensile properties of the two superalloys, the results indicate that under the tensile conditions from room temperature to 750 ℃, the tensile strength of the FGH4097 superalloy is higher than that of the GH4079 superalloy, and its plasticity is also significantly superior to that of the GH4079 superalloy. As the temperature increases, the difference in tensile strength and plasticity between the two superalloys becomes more pronounced. To further explore the high strength and high plastic deformation mechanisms of FGH4097 superalloy during tensile processes at different temperatures, the microstructure of the tensile fractures was characterized by TEM. For the FGH4097 alloy under tensile deformation conditions from room temperature to 650 °C, the dislocation configurations are predominantly characterized by high-density dislocation pile-ups in the γ channels, as well as dislocations cutting the γ′ phase in the form of superlattice stacking faults and antiphase domain boundaries, supplemented by a small number of continuous stacking faults cutting the γ′ and γ phases. This phenomenon indicates that the deformation of the alloy at low to medium temperatures is primarily controlled by dislocations cutting the γ′ phase. As the tensile temperature increases to 750–850 °C, the dislocation configuration in the FGH4097 alloy undergoes a significant transformation. A large number of microtwins form in the γ′ phase and γ matrix, becoming the dominant phase, while continuous stacking faults and superlattice stacking faults play only secondary roles. Under high-temperature conditions, the dominant deformation mechanism of the alloy shifts from dislocation cutting to a synergistic plastic deformation mechanism involving microtwins. For the GH4079 alloy under tensile conditions at 25, 650, and 750 °C, the phenomena of a large number of continuous stacking faults cutting the γ′ and γ phases, a small number of superlattice stacking faults cutting the γ′ phase, and a limited number of microtwins cutting the γ′ and γ phases are observed in GH4079 alloy, which are its primary deformation mechanisms.