An internal state variables constitutive model for Ni-based superalloy considering the influence of second phase and its application in flexible skew rolling

Microstructure prediction and control of Ni-based alloy during plastic forming is crucial for obtaining high-performance products. Taking GH4169 alloy as an example for study, firstly, hot compression experiments were conducted using both solution treated (ST) and aging treated (AT) alloys at different true strains (0.223–0.916), temperatures (900℃-1100℃), and strain rates (0.1 s⁻¹-10 s⁻¹). Then, an internal state variable constitutive model was established based on experimental data. In the developed model, the evolution of dislocation density, dynamic recovery, and dynamic recrystallization (DRX) behavior are reasonably described. Specifically, by introducing the volume fraction and size of the initial δ-phase, the interaction between δ-phase and dislocations, the influence of δ-phase on DRX behavior and critical strain, and its pinning effect on grain boundaries are considered. The calculation results indicate that accurate predictions can be achieved within a large parameter range. Subsequently, the model was applied to flexible skew rolling (FSR) process, a novel plastic forming method for forming shaft parts and bars. The finite element (FE) simulations and rolling experiments were carried out. The results indicate that the FE model embedded with the constitutive model can effectively predict the forming dimensions and microstructure distribution of GH4169 alloy. The established constitutive model can provide reference for the high-temperature plastic forming process of alloys containing the second phase.