Enhanced electrical conductivity and mechanical properties in thermally stable fine-grained copper wire

Strength and electrical conductivity are generally mutually exclusive properties in copper wires, both of which are required in applications such as high-speed rail. Here, rotary swaging is used to manufacture copper wires that combine high strength and conductivity, and are thermally stable. The rapid development of high-speed rail requires copper contact wire that simultaneously possesses excellent electrical conductivity, thermal stability and mechanical properties. Unfortunately, these are generally mutually exclusive properties. Here, we demonstrate directional optimization of microstructure and overcome the strength-conductivity tradeoff in copper wire. We use rotary swaging to prepare copper wire with a fiber texture and long ultrafine grains aligned along the wire axis. The wire exhibits a high electrical conductivity of 97% of the international annealed copper standard (IACS), a yield strength of over 450 MPa, high impact and wear resistances, and thermal stability of up to 573 K for 1 h. Subsequent annealing enhances the conductivity to 103 % of IACS while maintaining a yield strength above 380 MPa. The long grains provide a channel for free electrons, while the low-angle grain boundaries between ultrafine grains block dislocation slip and crack propagation, and lower the ability for boundary migration.

Automated summary

Strength and electrical conductivity are generally mutually exclusive properties in copper wires, but copper wires manufactured using rotary swaging overcome this tradeoff. By directionally optimizing the microstructure, the copper wire exhibits high strength, high electrical conductivity, and thermal stability simultaneously.