Study on the dynamic recrystallization mechanisms of Inconel 740 superalloy during hot deformation

The dynamic recrystallization (DRX) mechanisms of Inconel 740 superalloy were studied by electron backscatter diffraction (EBSD) analysis of the superalloy microstructures obtained under different deformation conditions. The results show that the discontinuous dynamic recrystallization (DDRX) occurs together with the continuous dynamic recrystallization (CDRX), while CDRX is not active during hot deformation. CDRX easily happens at the low deformation temperature, high strain rate and medium strain. Under the testing conditions, there are five mechanisms, i.e., the bulging of pre-existing grain boundaries, the nucleation assisted by Σ3 boundaries, the nucleation assisted by dynamic recovery at pre-existing grain boundaries, and the progressive subgrain rotation and the increase of the heterogeneous misorientation in the deformed grain interiors, to facilitate the occurrence of DRX. The first three are classified as DDRX mechanism and the latter two belong to CDRX mechanism. The illustration of different DRX mechanisms validated via observation of DRX process helps establish an in-depth understanding and insight into the microstructural evolution of this relatively new superalloy during hot forming.