Hot deformation behavior and microstructure evolution of Inconel 625 superalloy sheet

The hot deformation behavior and microstructural evolution of Inconel 625 superalloy sheet under different conditions were investigated. The hot tensile tests under the temperature ranging from 800 ℃ to 950 ℃ with the increment of 50 ℃ and the strain rates between 0.001 and 0.1 s⁻¹ were performed on a Gleeble 3500 machine. The experimental results indicated that the plastic flow behavior of the Inconel 625 sheet changes from work hardening to hot softening with the rise of experimental temperature and the decline of strain rate. Furthermore, the elongation is decreased with the rise of deformation temperature and decline of strain rate. According to the principle of dynamic material model (DMM), the process maps at various strains were constructed, and the optimal domain with the highest power dissipation was determined. The optimal domain appears at the temperature range of 925 and 950 ℃ and the strain rate between 0.001 and 0.1 s⁻¹ with the power dissipation efficiency of about 46.5%. The grain size, grain boundary and texture of the deformed samples under typical conditions was analyzed by electron backscatter diffraction (EBSD) and transmission electron microscope (TEM), which reflected that the dynamic recrystallization (DRX) occurs in the optimal hot working window, and the preferred orientation for DRX nucleation of the Inconel 625 superalloy sheet is the<001>direction. The deformation behavior of Inconel 625 sheet under the long-term service temperature range is affected by the coupled effect of DDRX and CDRX.