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Copper-based conductive wires with both a high strength and a high electrical conductivity could find applications in aerospace and power engineering as well as in niche scientific applications such as materials for the production of high-field pulsed magnets. Indeed, in order to produce non-destructive fields, the coils must be wound of wires with a very high mechanical strength to resist Lorentz forces. LNCMI-Toulouse produces some of the most intense non-destructive pulsed magnetic fields in the world with a European record of 98.8 T and aims at reaching more than 100 T.
This study explores the potential of the cold spray (CS) technique to produce dense composite cylinders of copper (Cu) and tungsten (W), which act as precursors for wire-drawing processes. The cold spray technique, a solid-state deposition process, consolidates powders into dense structures without melting the feedstock material. This method is particularly advantageous for preserving the microstructural integrity of materials while achieving high-density composites. Additionally, the high velocity of the deposited particles during cold spraying results in significant plastic deformation, leading to enhanced mechanical properties, such as elevated ultimate tensile strength (UTS), and unique microstructural characteristics.
The composite powder used in this study comprises Cu particles (15–45 µm) coated with an ultrathin W layer (1 vol% W; ~100 nm) created via Fluidized Bed Chemical Vapor Deposition (FBCVD). The choice of feedstock material played a pivotal role in determining the final properties of the composite wires. The W coating provided a homogeneous dispersion of the second phase, ensuring a nanoscale distribution critical to achieving the desired combination of electrical and mechanical performance.
W-Cu cylinders (diameter 8 mm or 14 mm, length 80 mm) prepared by CS serve as precursors to wire-drawing. The diameter of the cylinders is reduced by wire-drawing at room temperature, in several passes, thus producing progressively finer wires (diameter in the range 1-0.2 mm).
The electrical resistivity and tensile strength were measured at 293 K and 77 K. The composite wires containing 1 vol.% W achieved a tensile strength of 757 MPa and a low electrical resistivity of 0.33 µΩ·cm.
The results of this study underscore the effectiveness of the cold spray technique in fabricating advanced composite materials with tailored properties, paving the way for their implementation in cutting-edge scientific and industrial applications.
