Effect of Shear Deformation During Drawing on Inhomogeneous Microstructures and Textures in High Purity Copper Wires After Annealing

摘要

To determine the origin of the inhomogeneous microstructure and texture observed in drawn and annealed high purity copper wires, two kinds of drawing process conditions and their influence was investigated. The regular condition, based on a symmetric die, and a condition designed intentionally to produce an inhomogeneous shear deformation using an asymmetric die were employed. The difference in intensity of 111-100 distributed texture between the two wires confirmed that the wire drawn under the asymmetric die condition experienced a higher amount of shear deformation. The extensive shear strain in the wire drawn under the asymmetric die condition gave rise to inhomogeneous primary and secondary recrystallization behavior. After annealing at 200 degrees C, grains with 100 texture, which were larger than the surrounding recrystallized grains, were extensively present on one half circle of the wire drawn under the asymmetric die condition, while larger grains with 100 were sparsely observed around the middle region of the wire drawn under the regular condition. Interestingly, the area where the larger grains with 100 texture existed was identical to the area where the high shear strain occurred during drawing in both wires. During annealing at 400 degrees C, grains with 112 texture started to grow abnormally at the center of both wires as a result of secondary recrystallization. After annealing at 900 degrees C grains with 112 due to secondary recrystallization occupied the entire region of the wire drawn under the regular condition. On the other hand, in the wire drawn under the asymmetric die condition and then annealed at 900 degrees C, the 100 oriented grains as a result of the normal grain growth of the larger 100 grains which were observed after annealing at 200 degrees C, coexisted with the abnormally grown 112 grains. These results indicate that dynamic recrystallization induced by the shear strain during drawing plays an important role in the inhomogeneity of the microstructure and texture of wires after annealing.