Effect of Wire-Drawing Process Conditions on Secondary Recrystallization Behavior During Annealing in High-Purity Copper Wires

The relationship between the process condition of wire-drawing and the microstructural evolution during the subsequent annealing was investigated for the production of high-purity copper wires. Three wire-drawing process conditions were considered according to the reduction in the area per pass and the die angle, and their effects on the evolution of the grain structure and texture during annealing were investigated. Strain distributions, calculated using the finite element method, showed that the shear strain near the wire surface varies according to the process condition. The electron backscatter diffraction results indicate that the location on the cross-section of the wire, where secondary recrystallization initiates during annealing, is closely related to the shear strain during wire-drawing. Meanwhile, the effect of shear deformation on the grain structure and texture after primary recrystallization is insignificant. Drawing process conditions with a small reduction in the area per pass and die angle resulted in a relatively small shear strain and gave rise to the onset of secondary recrystallization at the central region of the wires. In contrast, the condition with a large reduction in the area per pass and die angle led to a high shear strain and the onset of secondary recrystallization at the peripheral region of the wire. The observed primary and secondary recrystallization behavior during annealing was explained from the viewpoint of dynamic material phenomena and inhomogeneity in the local recrystallization texture, regulated by the extent of shear deformation during wire-drawing.