Role of as-cast dendritic microstructure in recrystallization of a Ni-based single crystal superalloy

The role of as-cast dendritic microstructure in the recrystallization of a nickel-based SX superalloy DD6 was investigated. SX alloys were deformed at 980 °C using a Gleeble 1500D and subsequently annealed at lower temperatures under an inert argon atmosphere. Recrystallization initially nucleates in the dendritic arms and rapidly grows. In the interdendritic regions, nucleation was observed in the form of a large amount of annealing twinning. Recrystallization can occur in eutectics before it is completed in the interdendritic regions. Fine grains with plenty of twinning grains remained in this region. It was difficult for grain coarsening to occur as a result of the abundant twinning. Finally, the mechanism of the nucleation and growth of the annealing twinning was discussed.