Nanostructured 1% silver-copper composite wires with a high tensile strength and a high electrical conductivity

High-strength, high-conductivity silver-copper composite wires were prepared by powder metallurgy, spark plasma sintering and room-temperature wire-drawing. Silver nanowires were mixed with a commercial micrometric copper powder (1, 5 and 10 vol% silver). The powders were consolidated by spark plasma sintering in cylinders, which served as precursors for room temperature wire-drawing, producing samples of wires with progressively decreasing diameters. The Vickers microhardness for the wires is higher than that for the cylinders, reflecting both densification and grain refinement. Investigation of the microstructure reveals that the silver nanowires are located at the grain boundaries of ultrafine copper grains, elongated over several micrometers. The electrical resistivity and tensile strength were measured at 293 K and 77 K. The tensile strength is more than twice for the composite wires compared to the corresponding pure copper wires. Although higher tensile strengths are obtained using 5 vol% Ag, the wires containing only 1 vol% Ag offer the best combination of high strength (1100 ± 100 MPa at 77 K) and low electrical resistivity (0.50 μΩ cm). The 1 vol% Ag–Cu composite wires compare favorably with Ag–Cu alloy wires containing about 20 times more silver.