Effect Of Strain On Recrystallization Of A Ni-Based Single Crystal Superalloy

The effect of strain induced by compression testing on recrystallization (RX) of a single crystal superalloy DD6 was investigated. The evolution of surface structure during annealing at the temperatures of 1000, 1100, 1220 degrees C was characterized by Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS). The element distribution and microstructure of the oxidation layer after annealing at 1100 degrees C showed that the main chemical elements were mainly Al, Ta, Cr, Ni, O. This indicated that the formation process of oxides included the inward diffusion of O and the outward diffusion of oxide-rich elements (Al, Cr, etc.). The thickness of RX layer was measured. At 1000 degrees C, no recrystallization but PFZ (precipitate free zone) was observed under oxidation layer. However, when annealing at higher temperature, the thickness of RX layer increased obviously with the increasing deformation strain. Cellular recrystallization could be detected in the samples annealed at 1100 degrees C, whereas isometric recrystallization and annealing twin formed in the specimen annealed at 1220 degrees C.