Manufacturing of pure copper with extraordinary strength-ductility-conductivity balance by cryorolling and annealing

Abstract

To obtain a pure copper with extraordinary strength-ductility-conductivity balance, asymmetric cryorolling followed by low-temperature (200 °C) annealing was employed. The microstructural-mechanical-electrical properties of the samples were investigated. The results showed that multiple twinning was formed after the partial annealing of deformed copper. The copper annealed for 60 min exhibited a hardness, yield strength, and tensile strength of 38.1 HB, 192 MPa, and 422 MPa, respectively, while a large total elongation of 37.2% was obtained. Also, the annealed copper had a larger strain hardening rate at ε higher than 0.023 owing to the creation of twin chains. The fracture surface of the 60-min annealed copper was dominated by only ductile dimple features. The post-annealed copper showed an extraordinary electrical conductivity of 99.58%IACS, which is much larger than that for all pure coppers with UTS higher than 400 MPa. It was found that using second phase particles with high electrical conductivity was a better strengthening mechanism than strain hardening and grain boundary strengthening. An extraordinary strength-ductility-conductivity balance was achieved in the current pure copper compared to other pure coppers. This was due to the existence of copper oxide, and the formation of twin chains in the present work.