Recrystallization of a single crystal Ni-base superalloy in 〈011〉 and 〈111〉 orientations

The recrystallization behavior below the γ′ solvus of a single crystal nickel base superalloy was investigated. Both tension and surface grinding were adopted to introduce the pre-deformation before annealing. The results showed that surface recrystallization of the tensile samples were mainly controlled by the nucleation process which was closely associated with the dislocation density in the matrix channels. Full recrystallization occurring in the deformation bands of fractured 〈011〉 sample indicated that the pinning effect of the second phase could be significantly weakened by sufficient shearing of dislocations. The tendency of recrystallization was reversed in annealed samples processed by surface grinding. This was attributed to the high ability of nucleation on the grinded surface and the change of controlling mechanism to the pinning effect of the γ′ phase in the deformation layer.