Texture evolution and its influence mechanism on properties of single crystal copper and polycrystalline copper during cumulative deformation

Abstract

The φ16 mm single crystal copper rod was prepared by heated-mold horizontal continuous casting, and the φ16 mm polycrystalline copper rod was prepared by up-casting technology. Both of them were drawn to φ0.2 mm, the conductivity, strength, elongation, and microstructure evolution of single-crystal copper wire and polycrystal copper wire were compared and analyzed. The results show that the plasticity of as-cast single-crystal copper rod is 13.94% higher than that of as-cast polycrystalline copper rod. When drawing to φ0.2 mm, a single crystal copper wire with high strength (506 MPa) and high conductivity (98.01% IACS). At the same deformation amount, the single crystal copper wire obviously deforms more slowly and has a higher plastic deformation capacity; the texture transformation of single crystal copper wire is from soft → hard orientation, selective orientation to discrete distribution, while the weave transformation of polycrystalline copper wire is from soft → hard orientation, then from hard → soft orientation, and finally stabilizes to selective orientation. The microstructural evolution of single-crystal copper wire and polycrystalline copper wire during continuous deformation was observed: dislocation entanglement into dislocation cells by slip → microstrip structure → lamellar organization → twinning organization, single-crystal copper wire appears twinning later, single-crystal copper deformation coordination ability is better than polycrystalline copper. It is found that the increase of dislocation density, the decrease of grain width and the increase of <111> texture are the main factors for the strength improvement of micro-nano pure copper wires.