Constitutive Modelling and Processing Map of GH3128 Superalloy during Hot Deformation

The deformation characteristics of GH3128 were explored via tension experiments in the temperature region of 1023-1173 K and strain rate range of 0.001-1 s⁻¹. The stress decreased as the temperature increased and the strain rate decreased. The obtained strain–stress curves were classified into two types: hardening and hardening–softening curves. To realise the unified prediction of the two types of stress–strain curves, a modified Johnson-Cook (JC)-Zerilli-Armstrong (ZA) constitutive model was established based on the deformation characteristics, in which the modified JC and ZA models were used to express the work-hardening and softening sections, respectively. At the same time, the peak strain was described as a function of lnZ to separate the work-hardening and softening sections. The comparison results suggest that the JC-ZA constitutive model can precisely express flow behaviour. In addition, a hot processing map for the GH3128 alloy was developed. The results showed that the high-energy dissipation region was mainly concentrated in the domain with a lower strain rate and higher temperature, where the instability domains were not included. The optimised working region was determined to be 1098-1173 K and 0.001-0.3 s⁻¹. Microstructural observations showed that the main deformation mechanism of the stable regions was dynamic recovery (DRV), with a small amount of dynamic recrystallisation (DRX). These studies provided a theoretical basis for the processing design of GH3128 alloy components.