Evolution of Microstructure and Properties of Oxygen-Free Copper During Severe Drawing Process

Oxygen-free copper wires are widely required in advanced electronic and electrical systems. However, the relationship between deformation-induced microstructure evolution and property variation during severe cold drawing is not fully understood. In this study, oxygen-free copper rods with a diameter of φ20 mm were fabricated by upward continuous casting, followed by multi-pass cold drawing with deformation degrees up to 99.75%. The microstructure evolution, texture transformation, and property changes during drawing and annealing were systematically investigated. It found that increasing drawing deformation progressively elongated, fragmented, and refined the grains, reducing the average grain size from 339.18 μm to 2.12 μm. Dense dislocation cells, substructures, and nanoscale twins were generated during severe deformation, while the texture gradually evolved from random orientations to preferred and textures. After annealing, fine recrystallized equiaxed grains with abundant annealing twins formed together with recrystallization texture. At 99.75% deformation, the tensile strength reached 486 MPa, with an electrical conductivity of 96.7% IACS (International Annealed Copper Standard). After annealing, the electrical conductivity recovered to 101.5% IACS, while the tensile strength decreased to 187 MPa. This work establishes the relationship between severe deformation microstructure evolution and property response in oxygen-free copper, providing guidance for the fabrication of high-strength and high-conductivity copper conductors.