Study on the microstructure evolution during hot deformation of GH5188 superalloy

In this paper, the transformation law of microstructure evolution during multi-pass deformation and heat preservation was investigated by a Gleeble-3800 thermal simulation testing machine. A hot working diagram was established at deformation rate 0.01−10 s⁻¹, deformation amount 50%, and deformation temperature 980−1230 ℃. The effects of holding time after single-pass deformation on the microstructure of double-pass deformation, holding time after double-pass deformation and holding temperature on the microstructure evolution, and deformation and holding time after double-pass cooling on the microstructure were discussed. The results show that the boundary conditions of the high power dissipation zone in the hot working diagram are 1050−1175 ℃, 0.01−0.1 s⁻¹, and 1200−1225 ℃, 0.01−1 s⁻¹, respectively. The boundary conditions of the low power dissipation zone are 975−1150 ℃, 0.01−10 s⁻¹, and 1150−1225 ℃, 0.1−10 s⁻¹, respectively. Too long holding time after the first deformation is not conducive to the second dynamic recrystallization. The recrystallization phenomenon occurred after the double-pass deformation, and the grain size did not grow obviously with the increasing holding time. In addition, with the second deformation temperature decrease, the proportion of recrystallization in the specimen decreases, and the lower the holding temperature, the less likely static recrystallization occurs.