A new dynamic recrystallization kinetics model for a Nb containing Ni-Fe-Cr-base superalloy considering influences of initial δ phase

The isothermal compressive experiments of a Nb containing Ni-Fe-Cr-base superalloy are carried out. The influences of initial δ phase (Ni3Nb) upon dynamic recrystallization (DRX) behavior are discussed. By analyzing the experimental data, the DRX kinetics models are constructed by considering the synthetical influences of initial δ phase, strain rate and deformation temperature. The proposed DRX kinetics model quantitatively reveals the influences of δ phase on the DRX behavior, which is further verified by transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) observations. δ phase impedes the dislocation movement and supports preferential nucleation sites for DRX during hot deformation. Moreover, due to the pinning effect of δ phase, the DRX grain boundary migration can hardly proceed and the growth of DRX grain is restricted. However, with deformation temperature increasing, δ phase gradually dissolves and the influences upon DRX behavior become weaken.