Hot deformation behavior and constitutive model of GH3230 alloy

The flow stress behaviors and the deformation microstructure of GH3230 alloy were investigated by high temperature tensile in the temperature range from 1144 to 1273 K and strain rate range from 1×10^-3 to 1×10^-1 s^-1. The deformation activation at elevated temperatures was calculated. The constitutive relationship of GH3230 alloy during high temperature deformation was obtained by introducing Zener-Hollomon parameter. The results showed that flow stress increased with strain rate increasing but decreased with temperature increasing. The flow stress could be represented by a Zener-Hollomon parameter in the hyperbolic sine type equation. The material constants of thermal deformation were as follows: A=5.179×10¹⁶ s^-1, a=0.0088, n=3.9893, and the thermal deformation activation energy of GH3230 alloy was calculated as 455.203 kJ·mol^-1. It was found that the deformation activation energy was more susceptible to the strain rate. Scanning electron microscopy (SEM) results showed that the fracture mode of all specimens was micro-porous aggregation ductile fracture caused by the damage at different temperatures (1144~1273 K) and strain rates (1×10^-3~1×10^-1 s^-1), and the variation of temperature did not bring about major changes in fracture morphology, but the fracture dimple became deeper and larger when the strain rate decreased.