Hot deformation behavior and flow stress modeling of a novel CoNi-based wrought superalloy

The thermal deformation behavior and flow stress modeling of a novel CoNi-based wrought superalloy after forging was investigated at gamma' sub-solvus temperature (1050 degrees C and 1075 degrees C) and gamma' super-solvus temperature (1100 degrees C and 1125 degrees C) 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 degrees C/0.01 s-1 and 0.001 s-1 conditions, the gamma' phase dissolved resulting in substantial grain growth. The constitutive equations were established via the flow stress data with the respect to the gamma' phase dissolution. The activation energies for the gamma + gamma' dual-phase region and the gamma single-phase region of the studied alloy are about 650 and 390 kJ/mol, respectively, which is comparable with traditional Ni-based superalloys. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The thermal deformation behavior and flow stress modeling of a novel CoNi-based wrought superalloy were investigated at different temperatures and strain rates, showing dynamic recrystallization occurring under all deformation conditions. Additionally, when the alloy was deformed sub-solvusly at higher temperatures and lower strain rates, the gamma' phase dissolved resulting in substantial grain growth.