Modeling of microstructural evolution and flow behavior of superalloy IN718 using physically based internal state variables

Microstructural evolution and flow behavior greatly affect the hot forming process of IN718. In this research, hot deformation behaviors of IN718 were investigated by performing hot compression tests at temperature range of 1000–1100 °C with strain rates of 0.1–20.0 s⁻¹. By incorporating physically based internal state variables such as dislocation density, volume fraction of dynamic recrystallization, and grain size, a set of unified viscoplastic constitutive equations were developed to predict the microstructural evolution and flow behavior of IN718. The material constants were determined using a genetic algorithm (GA)-based optimization method. Comparisons of the computed and experimental results indicate that the constitutive equations established in this study can accurately describe the hot deformation behavior and microstructural evolution of IN718.