Study on the dynamic recrystallization mechanisms tailored by dislocation substructures of a coarse grained Co-free nickel-based superalloy

During hot deformation of nickel-based superalloys, dislocations are produced, annihilated or rearranged into substructures with specific configurations, which are of significance to dynamic recrystallization process since the nucleation and growth of new recrystallized grains are accompanied by the formation and transition of dislocation substructures. Therefore, revealing the relationship between the dislocation substructure and recrystallization process is an important issue to understand the recrystallization mechanisms. Derived from this perspective, a coarse grained Co-free nickel-based superalloy was applied to explore the dislocation substructure evolution and associated recrystallization behaviors through isothermal compression experiments. The results indicated that the dynamic recrystallization mechanisms were tailored by dislocation substructures which served as the precursor for new grains, meanwhile the dynamic recovery played an important role that it promoted the dislocation substructure transitions. The independent substructures within the deformed grains contributed to the occurrence of continuous dynamic recrystallization (CDRX), while the substructures attached to the original grain boundaries contributed to the occurrence of discontinuous dynamic recrystallization (DDRX). The dislo-cation substructures were sacrificed as the driving force for recrystallization kinetic because the recrystallized volume fraction was inversely proportional to the content of sub-boundaries after deformation. The distance between adjacent sub-boundaries determined the new grain size during CDRX process, based on the processing of continuous rotation, a weight model was proposed to predict the grain size.

Automated summary

During hot deformation of nickel-based superalloys, dislocations undergo various processes such as production, annihilation, and rearrangement into substructures, which have a significant impact on the dynamic recrystallization process. Understanding the relationship between dislocation substructures and recrystallization mechanisms is crucial. Through isothermal compression experiments, the evolution of dislocation substructures and associated recrystallization behaviors were studied in a coarse-grained Co-free nickel-based superalloy. The results showed that dislocation substructures governed the dynamic recrystallization mechanisms and acted as precursors for new grains, while dynamic recovery promoted the transition of dislocation substructures. Continuous dynamic recrystallization was influenced by independent substructures within deformed grains, while discontinuous dynamic recrystallization was influenced by substructures attached to original grain boundaries. The sacrifice of dislocation substructures drove recrystallization kinetics, as the recrystallized volume fraction was inversely proportional to the content of sub-boundaries after deformation. The distance between adjacent sub-boundaries determined the new grain size during continuous dynamic recrystallization, and a weight model was proposed for grain size prediction based on continuous rotation processing.