LAUSR

Abstract A grain refinement process for a GH4169 superalloy sheet was proposed with the following parameters: solid solution (1050 °C × 0.5 h), cold rolling (50% reduction rate), δ phase precipitation treatment (890 °C × 10 h), high-pressure torsion (HPT) (3, 4, and 5 GPa), and recrystallization annealing (950 °C × 3 h). An ultrafine-grained sheet with an average grain size of 0.8 μm was prepared. The microstructure transformation, recrystallization process, and grain refinement mechanism of the materials in each stage were examined. Results revealed that large amounts of subgrain structures and irregularly shaped δ phases existed in the GH4169 superalloy exposed to HPT. During the recrystallization annealing at 950 °C, the dispersed and uniformly distributed δ phase blocked the migration of the recrystallized grain boundaries. The distorted microstructure after HPT was replaced with the newly formed fine grain without distortion, eventually forming an ultrafine grain structure with high-angle grain boundaries. After HPT processing was performed at 5 GPa × 2 turns, a cubic texture in the {100} direction was produced in the GH4169 superalloy.