Dynamic recrystallization mechanism of as-cast nickel base superalloy N10276 during primary hot working

The dynamic recrystallization(DRX)mechanism of as-cast nickel base superalloy N10276 during primary hot working was investigated by compression tests at temperatures of 1000–1200℃ and strain rates between 0.01 and 10 s^(-1).Optical microscopy,scanning electron microscopy,electron backscattered diffraction technique and transmission electron microscopy were used to characterize the evolution of microstructure.At higher deformation temperature or lower strain rate,the true stress–true strain curves exhibit the characteristic of a peak stress followed by a steady state flow stress under large strains,confirming the occurrence of DRX.The degree of DRX increases with elevating deformation temperature.With the progress of DRX,low angle grain boundaries gradually decrease,while high angle grain boundaries increase continuously.Microstructure studies have shown that discontinuous dynamic recrystallization is the main recrystallization mechanism.Since there are few original grain boundaries and twin boundaries,and lack of second phase particles for particle stimulated nucleation,geometrically necessary boundaries are formed as supplementary nucleation sites through sub-grain boundary rotation and deformation twin boundaries.The annealing twins dominated by Σ3 grain boundaries are generated in large quantities during the growth of recrystallized grains.