Grain Refinement of Niobium by Severe Plastic Deformation
- Department of Mechanical Engineering, Texas A and M University, College Station, Texas 77843-3123 (United States)
Large grained pure niobium was processed by multi-pass equal channel angular extrusion and then annealed with the objective of producing a fine-grained uniform recrystallized microstructure. Extrusions were performed on 25 mm square cross-section bars in a right angle die at room temperature. Material was processed through 1, 2, 4 and 8 consecutive extrusion passes corresponding to plastic strains of 1.15, 2.3, 4.6 and 9.2. The Vicker's hardness increased from 66, for the cast material, to 155 after eight extrusions. The temperature for which full recrystallization is achieved for two pass material is near 1100 deg. C and decreases for higher strains. The recrystallized grain size after two passes is near 50 {mu}m but spans the range 10{mu}m to 100{mu}m with distinct regions or 'bands' showing different average grain size. The average recrystallized grain size decreases with increased strain and becomes more uniform but larger for higher annealing temperatures. Work on improved thermo-mechanical processing strategies to eliminate 'banding' and produce further reductions in the recrystallized grain size is underway.
- OSTI ID:
- 20653225
- Journal Information:
- AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 711; ISSN APCPCS; ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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