Hot Deformation Behavior and Flow Stress Modeling of A Novel CoNi-based Wrought Superalloy

Abstract The thermal deformation behavior and flow stress modeling of a novel CoNi-based wrought superalloy after forging was investigated at γ' sub-solvus temperature (1050 ℃ and 1075 ℃) and γ' super-solvus temperature (1100 ℃ and 1125 ℃) with strain rate range from 0.001 s-1 to 0.1 s-1 under a 50% strain. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) techniques were used to characterize the microstructures and explain the flow behavior. The results show that the flow stress increases with decreasing temperature and increasing strain rate. Dynamic recrystallization (DRX) occurs under all deformation conditions. When the alloy was deformed sub-solvusly at 1075 ℃/0.01 s-1 and 0.001 s-1 conditions, the γ' phase dissolved resulting in substantial grain growth. The constitutive equations were established via the flow stress data with the respect to the γ' phase dissolution. The activation energies for the γ+γ' dual-phase region and the γ single-phase region of the studied alloy are about 650 and 390 kJ/mol, respectively, which is comparable with traditional Ni-based superalloys.