Effect of primary grain size on the secondary recrystallization of mechanically alloyed oxide dispersion strengthened nickel-based superalloy

The aim was to investigate the influence of the initial microstructure of an as-extruded ODS Ni-based superalloy on the secondary recrystallization behavior during zone annealing. It appears that when the average grain size is below the critical value (0.45 mu m), the nucleation rate of secondary recrystallization is greater than that of the grain growth rates, resulting in lower GAR (grain aspect ratio) values. When the average grain size is above the critical value (0.55 mu m), the driving force of grain growth is reduced somehow. However, the exact mechanism is not known at this time.