New Ag-Cu composite wires

22 January 2020 par Super Administrateur
S. Tardieu, F. Lecouturier-Dupouy, N. Ferreira (LNCMI) and D. Mesguich, A. Lonjon, G. Chevallier, A. Proietti, C. Estournès, C. Laurent (CIRIMAT)

New Ag-Cu composite wires are developed for the winding of non-destructive pulsed magnets. 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 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.

Figure: Ultimate tensile strength versus electrical resistivity at 77 K for a selection of the present Cu (black diamond) and 1Ag–Cu (blue triangles), 5Ag–Cu (red circles), 10Ag–Cu (green squares) wires and other wires: CNT-Cu wires (purple circles) and Ag–Cu alloy wires (24–28 wt% Ag) (black squares).

Nanostructured 1% silver-copper composite wires with a high tensile strength and a high electrical conductivity; S. Tardieu, D. Mesguich, A. Lonjon, F. Lecouturier, N. Ferreira, G. Chevallier, A. Proietti, C. Estournès, C. Laurent, Materials Science and Engineering: A 761, 138048 (2019) (