A multiphase strengthened Cu-Nb-Si alloy with high strength and high conductivity

Abstract There is a challenging trade-off between the high strength and high electrical conductivity in copper-based alloys. Designed Cu-3.65 wt%Nb (CN) and Cu-3.48 wt%Nb-0.11 wt%Si (CNS) alloys were fabricated by vacuum melting and followed by thermal-mechanical treatment. Microstructure evolutions and properties measurements were studied. Results indicate that morphologies of the Nb3Si phase in the CNS alloy are solid or hollow regular polygons whose boundaries are parallel to one of Nb3Si's crystal faces. The Nb3Si's precipitation can effectively improve the strength, while the Nb3Si tip is easy to form stress concentration, which leads to crack and failure. The high electrical conductivity of the CNS alloy was because of the decomposition precipitation of Nb and Nb3Si during aging treatment. After hot-rolled by 80% at 900 °C, cold-rolled with a strain of 2.30, the ultimate tensile strength of CN and CNS alloys were 488 MPa and 510 MPa, electrical conductivities were 88.06%IACS (International Annealed Copper Standard) and 93.20%IACS, and elongation rates were 9.3% and 7.1%, respectively. These findings reported a new method to fabricate high-strength and high-conductivity copper alloy.