Effect of cold rolling reduction rate on mechanical properties and electrical conductivity of Cu-Ni-Si alloy prepared by temperature controlled mold continuous casting

The contradictory relation between the strength and electrical conductivity of Cu-Ni-Si alloy after cold deformation is a significant scientific issue, break the contradictory relation is an important challenge for preparing the Cu-Ni-Si alloy with high strength and electrical conductivity. The C70250 copper alloy strips were prepared by temperature controlled mold continuous casting (TCMCC) and cold rolled. The effects of different cold rolling reduction rates on mechanical properties and electrical conductivity of the alloy were investigated, and the mechanism was revealed. The results indicate that the C70250 copper alloy strip prepared by TCMCC can be directly cold rolled with large deformation. When the cumulative cold rolling reduction rate reaches 97.5%, the strength and electrical conductivity of the alloy increase by 327 MPa and 0.6 IACS%, respectively. With the increase of cold rolling reduction rate, the shear deformation degree of columnar grain structure with strong [001] orientation increases gradually in C70250 copper alloy prepared by TCMCC. The alloy forms a large number of parallel shear bands consisting of high density dislocations, which seriously hinder the slip of dislocations and lead to the continuous increase of strength of the alloy. The parallel distributed shear bands in the C70250 copper alloy uniformly cut the matrix during the cold rolling process, and finally form a fibrous-shaped microstructure. The transverse grain boundary density is significantly reduced after cold deformation, which greatly reduces the influence of transverse grain boundary on the electrical conductivity and leads to abnormal increase of the electrical conductivity of the alloy.