2D cellular automaton simulation of hot deformation behavior in a Ni-based superalloy under varying thermal-mechanical conditions

A 2D cellular automaton model (CA) is developed to predict the hot deformation behavior of a Ni-based superalloy over a wide range of thermal-mechanical conditions. Relationships between the model parameters (work hardening parameter, dynamic recovery parameter, nucleation rate, and grain boundary mobility) and the thermal-mechanical conditions are established. The developed CA model is further employed to study the hot deformation behavior of the studied superalloy under varying thermal-mechanical conditions. These varying conditions include the sudden change of strain rate and gradual change of deformation temperature. The evolutions of flow stress, average grain size and fraction of dynamic recrystallization (DRX) under the varying thermal-mechanical conditions are predicted. The reliability of the simulated results is verified by experimental results. It is found that the predicted results under varying thermal-mechanical conditions gradually approach those under constant hot deformed conditions. i.e., constant deformation temperature and strain rate. The varying thermal-mechanical condition makes the complex evolution of dislocation density, fraction of DRX, and average grain size. Additionally, a pseudo-metadynamic recrystallization is found. The pseudo-metadynamic recrystallization is a temporary suspension of dynamic recrystallization during a large and rapid increase of strain rate as a consequence of nucleation inhibition. It resembles metadynamic recrystallization, except that the pseudo-metadynamic recrystallization occurs when the hot deformation is still underway.