Abstract:The hot compression curves and deformed microstructures were investigated under various hot deformation conditions in three states: hot isostatic pressing (HIP, A1), HIP+hot extrusion at 1100 ℃ (A2), and HIP+hot extrusion at 1150 ℃ (A3). The results show that A2 sample, extruded at 1100 ℃ with uniform γ+γ′ duplex microstructures, demonstrates excellent hot deformation behavior at both 1050 and 1100 ℃. The true stress-true strain curves of A2 sample maintain a hardening-softening equilibrium over a larger strain range, with post-deformation average grain size of 5 μm. The as-HIPed A1 sample and 1150 ℃ extruded A3 sample exhibit a softening region in deformation curves at 1050 ℃, and the grain microstructures reflect an incomplete recrystallized state, i.e. combination of fine recrystallized grains and initial larger grains, characterized by a necklace-like microstructure. The predominant recrystallization mechanism for these samples is strain-induced boundary migration. At 1150 ℃ with a strain rate of 0.001 s-1, the influence of the initial microstructure on hot deformation behavior and resultant microstructure is relatively less pronounced, and post-deformation microstructures are fully recrystallized grains. Fine-grained microstructures are conducive to maximizing the hot deformation potential of alloy. By judiciously adjusting deformation regimes, a fine and uniform deformed microstructure can be obtained.