Abstract:The severe deterioration of thermal plasticity for nickel-base wrought superalloys with high Al and Ti contents during cogging has become the bottleneck for their wide application, and their thermal plasticity can be significantly affected by the γ′ precipitation. However, previous studies about the role of γ′ on hot deformation behaviors of such alloys did not consider the interference of grain boundary strengthening elements. In this paper, a high Al+Ti nickel-base superalloy ingot without adding grain boundary strengthening elements C, B and Zr was prepared and fully homogenized. Afterwards, the hot deformation behaviors of this as-homogenized ingot at 1060 ℃ (γ/γ′ dual-phase range) and 1170 ℃ (γ single-phase range) were investigated. The results show that, the deformation resistance in γ single-phase range is much lower than that in γ/γ′ dual-phase range, and the plasticity of γ single-phase range is much better. Interestingly, in γ single-phase range a typical yield drop phenomenon appeared, while no such phenomenon appeared in γ/γ′ dual-phase range. This may be because the release of more Al and Ti solutes in γ single-phase range hinders the movement of dynamic dislocations and finally locks them. Both the γ single-phase and γ/γ′ dual-phase ranges showed intergranular cracking, which indicates that initial grain boundaries are the weakest link in hot working process of such alloys. When the logarithmic strain reaches 0.36, discontinuous dynamic recrystallization (DDRX) has occurred in both the γ single-phase and γ/γ′ dual-phase ranges, and with the increase of strain the number of DRX grains increases significantly, but the DRX grain size has no obvious change. Owing to the pinning effect of γ′ to grain boundaries, the DRX grain size in γ single-phase range is much greater than that in the γ/γ′ dual phase range, but the number density of DRX grains in the γ single-phase range is much smaller. The main reason for the lower deformation resistance and better thermal plasticity in the γ single-phase range is that the rapid growth of DRX grains rapidly can reduce the dislocation density near the initial grain boundary.