Modeling the PSN mechanism of recrystallization nuclei formation in Inconel 718

This study proposes and applies a mathematical model to describe the process of recrystallization nucleation on large d-phase particles in the Inconel 718 nickel alloy during annealing (the particle stimulated nucleation (PSN) mechanism). The investigation employs a multilevel approach based on an extended statistical model, in which the subgrain structure is explicitly described by an aggregate of Laguerre polyhedra. The model for the formation of new recrystallized grain nuclei is based on the physical mechanisms of recovery: subgrain coalescence and low-angle boundary migration. Additionally, the model accounts for lattice rotations of subgrains near the non-deformable particle resulting from the incompatibility of prior plastic deformation, as well as the retarding effect of dispersed γ′ and γ″ particles during subgrain boundary migration. Numerical experiments were conducted on a representative volume of subgrains at annealing temperatures range 450–950 °C. It is shown that at 450 - 850°C subgrain growth near the d-phase particle is retarded due to increased misorientation, which hinders coalescence. At temperatures above 950 °C, the dissolution of the strengthening phases γ′ and γ″ leads to a decrease in the Zener pinning force and intense boundary migration near the d-phase particle results in the active formation of recrystallization nuclei. It is established that a needle-shaped d-particle promotes more intense nucleation compared to a spherical one due to its larger interfacial area. The simulation results are in qualitative agreement with known experimental data.