Relationship among processing technology, microstructure and properties of Cu-Ni-Si alloy prepared by temperature controlled mold continuous casting and mechanism

Temperature controlled mold continuous casting (TCMCC) technology was used to produce C70250 copper alloy strips. The strips were cold rolled and aged at different temperatures and time. The relationships among processing technology, microstructure, mechanical properties and electrical conductivity were investigated to reveal the mechanism. The results show that the C70250 copper alloy strips prepared by TCMCC have coarse columnar grain structure with less transverse grain boundaries. After cold rolling with the deformation of 97.5%, the fibrous microstructure is formed along the rolling direction. When the aging temperature and the aging time are 450℃ and 60min, the tensile strength and the electrical conductivity of the alloy are 758MPa and 54.5%IACS. Compared with the alloy prepared by traditional process, the tensile strength and the electrical conductivity increase by 5.3% and 36.3% respectively, which means the strength and electrical conductivity are improved simultaneously. Under this condition, the alloy retains the fibrous microstructure and a large number of Ni2Si phases are uniformly precipitated with the size of 6-10nm. The strength of the alloy is improved with the joint action of work hardening and Orowan strengthening. The electrical conductivity of the C70250 copper alloy is significantly improved by the fully precipitated solute atoms and the reduced transverse grain boundaries