Fractal structure and nano-precipitates break comprehensive performance limits of CuCrZr alloys

Modern industrial materials are often required to have excellent comprehensive properties. Contact wire used in high-speed train needs possess high strength and toughness, high conductivity and wear resistance, which are often trade-off with each other. In this work, we constructed a fractal structure with high-density nano-precipitates in CuCrZr alloy via rotary swage plus aging, and break the strength, conductivity and ductility limits of existing Cu alloys. The CuCrZr alloy exhibits unprecedented comprehensive properties of a high ultimate tensile strength of 626 MPa, a ductility of 19% and an electrical conductivity of 82% international annealed copper standard (IACS). Microstructural analysis indicates that the fractal structure and high-density nano-Cr precipitates block and accumulate dislocations, but allow electrons to flow unimpededly along the axis of CuCrZr wire, resulting in the high toughness and conductivity. Our finding verifies fractal structure has the potential to obtain materials with super excellent comprehensive properties.