Variation of activation energy determined by a modified Arrhenius approach: Roles of dynamic recrystallization on the hot deformation of Ni-based superalloy

Abstract

The hot deformation behaviors of Ni18Cr9Co9Fe5Nb3Mo superalloy were explored in the formation temperature range free of γ’ phase with various strain rates applied. The hot deformation behaviors are initially modeled with Arrhenius equation which gives an average activation energy of 581.1 kJ mol−1. A modified Arrhenius approach, including the updated Zener-Hollomon parameter is proposed to consider the change of activation energy under different deformation conditions which turns out a relatively accurate computation for activation energy of hot deformation, i.e., the standard variance for modified model calculated in the covered deformation condition is just 35.4 % of that for Arrhenius equation. The modified model also proposes a map for activation energy which ranges from 571.5-589.0 kJ mol−1 for various deformation conditions. Microstructural features of the representative superalloy specimens were characterized by electron backscattered diffraction (EBSD) techniques in order to clarify the influence of activation energy on the microstructural formation. It is found that the Ni-based superalloy samples with higher activation energy are promoted by the degree of dynamic recrystallization which suggests that the rise in activation energy gives either a better recrystallization rate or finer grains.