Dynamic balance between grain refinement and grain growth during high-pressure torsion of Cu powders |
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| Authors: | Haiming Wen Rinat K. Islamgaliev Konstantin M. Nesterov Ruslan Z. Valiev Enrique J. Lavernia |
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| Affiliation: | 1. Department of Chemical Engineering and Materials Science , University of California , Davis , CA , 95616 , USA hmwen@ucdavis.edu;3. Institute of Physics of Advanced Materials , Ufa State Aviation Technical University , Ufa , 450000 , Russia;4. Department of Chemical Engineering and Materials Science , University of California , Davis , CA , 95616 , USA |
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| Abstract: | High-pressure torsion (HPT) was applied to unmilled coarse-grained (CG) Cu powders with low initial dislocation density and cryomilled nanocrystalline (nc) Cu powders with high initial dislocation density, with identical processing parameters. HPT of unmilled CG Cu powders resulted in exceptional grain refinement and increase in dislocation density, whereas significant grain growth and decrease in dislocation density occurred during HPT of cryomilled nc Cu powders. Equilibrium structures were achieved under both conditions, with very similar stable grain sizes and dislocation densities, suggesting dynamic balances between deformation-induced grain refinement and grain growth, and between deformation-induced dislocation accumulation and dislocation annihilation. The equilibrium structures are governed by these two dynamic balances. |
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| Keywords: | high-pressure torsion nanostructured materials grain growth grain refinement deformation mechanism dislocations |
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