Microstructural evolution on the initiation of sub-solvus recrystallization of a grit-blasted single-crystal superalloy

In this work, the initiation of cellular recrystallization of a grit-blasted single-crystal superalloy has been investigated by combined TEM and EBSD techniques. Based on microstructure observations of the grit-blasted surface, the formation of dislocation tangles in γ channel and stacking faults in γ′ precipitates has been validated. After subsequent annealing at 1100°C for 30min, in the original matrix, neighboring γ′ precipitates have partially dissolved and merged into localized irregular agglomerates; concurrently, dense dislocation walls have formed and transformed to subgrain boundaries. For cellular recrystallized region, the formation of twins played a significant role in lowering the energy for sub-solvus recrystallization, which facilitated the transformation process.