Preparation of ultrafine-grained GH4169 superalloy by high-pressure torsion and analysis of grain refinement mechanism

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 (9...

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Bibliographic Details
Published in:Journal of alloys and compounds 2019-03, Vol.777, p.157-164
Main Authors: Luo, Junting, Yu, Wenlu, Xi, Chenyang, Zhang, Chunxiang, Ma, Chunhui
Format: Article
Language:English
Subjects:
Annealing
Cold rolling
Cube texture
GH4169 superalloy
Grain boundaries
Grain refinement
Grain refinement mechanism
Grain structure
High-pressure torsion
Microstructure
Migration
Recrystallization
Solid solutions
Superalloys
Torsion
Ultrafine grain
Ultrafines
δ phase
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Summary: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. •A new grain refinement process for a GH4169 superalloy sheet was proposed.•Ultrafine-grained sheet with an average grain size of 0.8 μm was prepared.•Grain refinement mechanism of the GH4169 superalloy sheet was analyzed by EBSD.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2018.10.385