Manufacturing uniform copper strips by a novel near-isometric continuous expansion extrusion process

In this paper, a novel near-isometric continuous expansion extrusion was developed to fabricate copper strips. The technique was realized by modifying the deformation channels in continuous extrusion to form a C-shaped cross-section, where an accumulative strain of ~50 across the entire cross-section was achieved. Apart from this, the novel-designed deformation channels homogenize the strain distribution and thus facilitate the uniformity of strain rates and temperatures. Microstructure characterization and mechanical testing at the center and edge areas of the strip confirm the uniformity of the strip, demonstrating the superiority of this technique for manufacturing uniform strips. For comparison, the traditional flat strips produced by continuous extrusion were investigated, where non-uniformly distributed strain, strain rate, and temperature fields were revealed. The microstructures at the center and edge areas of the strip exhibit differences in grain size, dislocation density, and texture, resulting in different mechanical properties. Additionally, the newly designed near-isometric continuous expansion extrusion lowers the 20 % torque force, which shows great potential for extending the extrusion width-thickness ratio. Thus, compared with the traditional flat continuous extrusion and other severe plastic deformation techniques, the developed near-isometric continuous expansion extrusion shows considerable promise for manufacturing uniform metal strips.