Plastic deformation behavior and dynamic recrystallization of Inconel 625 superalloy fabricated by directed energy deposition

In this study, the hot plastic deformation behavior and dynamic recrystallization (DRX) phenomenon of Inconel 625 superalloy prepared by directed energy deposition (DED) are investigated by carrying out hot compression tests. The true stress–strain curves indicate that with the increment in deformation temperature and decrease in strain rate, the peak stress and flow stress reduce. Compared with wrought Inconel 625 superalloy, Inconel 625 superalloy fabricated by DED shows a higher flow stress, lower peak stress, and lower deformation activation energy under the same hot compression conditions. The fraction of recrystallized grain and recrystallized grain size increases with increasing temperature and decreasing strain rate. At lower deformation temperatures, continuous dynamic recrystallization is the main mechanism of DRX. However, discontinuous dynamic recrystallization becomes the predominant operating mechanism of DRX at high deformation temperature. In addition, the kinetics of DRX in DED Inconel 625 superalloy is much slower than that in forged Inconel 625. The results also show that DED Inconel 625 superalloy has higher thermal stability than that of forged Inconel 625 superalloy, which makes it possible for DED Inconel 625 superalloy to be employed at high temperatures.