Microstructure evolution of high-strength and ultra-high-conductivity microfilament wire prepared by continuous deformation of single-crystal copper

The φ16 mm single-crystal copper rod billet was prepared by the heated mold horizontal continuous casting process. After cold drawing + 600 °C× 5 s annealing to φ1 mm, the annealed φ1 mm single-crystal copper processing wire was cold drawn to φ0.2 mm (φ1 mm → φ0.2 mm), and the electrical conductivity, tensile strength and microstructure evolution of single-crystal copper wire were compared and analyzed. The research shows that the conductivity of the as-cast single-crystal copper rod is 102.1% IACS, the tensile strength is 141 MPa, the conductivity is as high as 97.26% IACS, after cold drawing to φ0.2 mm, and the tensile strength is greatly increased to 506 MPa. Compared with the as-cast properties, the electrical conductivity of the as-drawn wire is only reduced by 4.7%, while the tensile strength is increased by 258.9%. The as-cast rod exhibits typical characteristics of single-crystal copper; with the increasing amount of deformation, the microstructure evolves in the following form: dislocations generated by slip entanglement into dislocation cells → microstrip structure → layered structure → twin structure. A prediction model for the strength and electrical conductivity of single-crystal copper wire was constructed. The results show that grain refinement strengthening and dislocation strengthening are the key factors affecting the strength and conductivity of single-crystal copper wire, when deformed to φ0.2 mm, and twinning strengthening is superimposed in the above strengthening mechanism.