Effect of Deformation Conditions on the Dynamic Recrystallization of GH690 Alloy

Hot compression tests were conducted using a Gleeble–3500 thermomechanical simulator to investigate the effect of hot deformation conditions on dynamic recrystallization (DRX) of GH690 alloy. The results show that the DRX process of GH690 alloy is controlled by deformation temperature and strain rate. Under the investigated condition at a constant strain rate ranging from 0.001 to 1 s−1, the temperature needed for fully dynamic recrystallization increases with the increases of strain rate, and the size of dynamically recrystallized grain is greatly affected by the increase of deformation temperature. The values of critical strain for the initiation of DRX can be determined from the strain-stress curves, and a equation related to the Zener-Hollomon Parameter is as follows: ɛc =1.135×10−3Z0.14233. A discontinuous dynamic recrystallization (DDRX) mechanism with nucleation of bulging of the original grain boundaries is the operating nucleation mechanism of DRX of GH690 alloy. A continuous dynamic recrystallization (CDRX) with subgrain rotation, which can only be considered as an assistant nucleation mechanism of DRX, occurs simultaneously with the DDRX.