Hot deformation behavior and new grain size model of hot extruded FGH4096 superalloy during hot compression

The deformation behavior and grain size models of hot extruded (HEXed) FGH4096 superalloy at the temperature of 1040–1130 ℃ and the strain rate of 0.001–1 s−1 were investigated by hot compression. On the basis of the corrected flow stress curves, the constitutive equation considering the strain variable and hot working maps were established. The dynamic recrystallization (DRX) behaviors and microstructure evolution in different regions in hot working map superimposing the hot working instability maps were also analyzed. Discontinuous dynamic recrystallization (DDRX) occurs simultaneously with continuous dynamic recrystallization (CDRX) in the HEXed FGH4096 superalloy at low temperature, while only DDRX is activated at high deformation temperature. The wedge cracks, voids, and intergranular cracks are the main causes of flow instability. An optimal hot working window of deformation temperature = 1102–1130 ℃ and strain rate = 10−1.26–10−0 s−1 was obtained by combining the hot working maps and microstructure evolution. An established new grain size model by extending the Z parameter can predict the average grain size more accurately.