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

Dislocation tangles in γ and stacking faults in γ′ were induced by a grit-blasting.During recovery, γ′ dissolved and merged into localized irregular agglomerates.Intersecting dislocation walls cause the formation of bulges as nucleation sites.Formation of twins effectively lowers the energy during recrystallization.

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 30 min, 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.

Figure optionsDownload as PowerPoint slide