Preparation and mechanisms of Cu–Ag alloy fibers with high strength and high conductivity

Cu–Ag alloy fibers are known for their excellent electrical and thermal conductivity, and are widely used in various fields, such as electronics, transportation, and processing due to their low price and simple preparation process. Nevertheless, this trade-off relation between strength and electrical conductivity of Cu–Ag alloys restricts their scope of application. In order to prepare Cu–Ag alloy fibers with high strength and high electrical conductivity, three different processes: cold drawing, surface electrodeposition and electrolytic polishing, are investigated and comprehensively utilized. By comparing the evolution of microstructure and properties in Cu–Ag alloy fibers, along with the corresponding mechanisms for strengthening and conductivity, one most suitable process path is explored. Cold-drawing is utilized to reduce the grain size, which, in turn, enhances the strength of the fibers. Meanwhile, it refines the internal grains of the alloy by shearing and deflecting each other, ultimately resulting in a fiber texture along the drawing direction. The main contributors to the strength of Cu–Ag alloy fibers are dislocation strengthening, grain boundary strengthening, and texture strengthening. The slight difference is that for electrical conductivity, dislocation and grain boundary play a crucial role. Electrodeposition of copper on the fiber surface is an effective method for improving the electrical conductivity of the fiber, which is achieved by creating a dense conductive pathway on the surface of the fiber. However, this process leads to a reduction in strength. Therefore, electrolytic polishing is subsequently used to regulate the plating thickness in order to obtain Cu–Ag alloy fiber with synchronous increase of strength and electrical conductivity.