Recent progress on the study of the microstructure and mechanical properties of ECAE copper |
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Authors: | Florian H Dalla Torre Azdiar A Gazder Elena V Pereloma Christopher H J Davies |
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Affiliation: | (1) Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, Zurich, 8093, Switzerland;(2) Department of Materials Engineering, Monash University, Melbourne, VIC, 3800, Australia;(3) Victorian Centre for Advanced Materials Manufacturing, Belmont, VIC, Australia |
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Abstract: | Results on the microstructure and the tensile properties of equal channel angular extruded (ECAE) copper processed for one
to 16 passes are presented and compared with the available literature data. With increasing number of passes (N), the microstructure
changes from a strongly elongated shear band structure after N = 1 and 2, towards a more equiaxed subgrain and grain structure.
This is accompanied by a decrease in the cell wall or subgrain-boundary widths and an increase in recovered or even recrystallised
grain structures with low dislocation densities. Electron backscatter diffraction measurements have indicated that for lower
N, the location of Σ3 boundaries is restricted to shear bands, while at greater N, Σ3 boundaries were found to be more widely
distributed. Texture measurements indicate close similarity with simple shear texture components and a spread of the orientation
components with greater N. Upon comparing the tensile behaviour of as-ECAE Cu with the surveyed literature, broad agreement
on the strength of the material is achieved. However, a strong variation in the percentage elongation to failure is also noted.
Strain hardening and deformation kinetic analysis via strain rate jump tests indicate an evolution from stage III to V hardening
during post-ECAE compression and a saturation in the strain rate sensitivity after N = 4 resulting in maximum values of ∼0.02.
Our results suggest that rather than a change in deformation mechanism, the increase in ductility with increasing N is associated
with an increase in the mean free path of dislocations—with the grain boundaries remaining actively involved as the transmitter
of plastic strain and their interaction with dislocations being the rate controlling deformation mechanism.
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