Design of novel silver – copper nanocomposite wires to break the usual strength-resistivity trade-off

08 November 2023 par Super Administrateur

The generation of record pulsed magnetic fields above 100 T requires the use of coils wound with low- resistivity wires in order to limit the heating, and with a very high mechanical strength in order to be able to resist the Lorentz forces. The LNCMI and the CIRIMAT are exploring the design of novel silver – copper nanocomposite wires with the aim to break the usual strength-resistivity trade-off.

Composite wires containing only 1 vol.% silver nanowires dispersed in a bimodal (1 µm / 20 µm) copper matrix are prepared by a combination of powder metallurgy, Spark Plasma Sintering and room-temperature wire- drawing.

We bring to light that:

  • it is possible to improve the low resistivity – high ultimate tensile strength (UTS) compromise of the composite wires by simply adding large grains of Cu during the composite powder preparation step,
  • the larger copper grains act as channels for fast electron conduction thus allowing to maintain a low electrical resistivity (0.45 μΩ.cm, at 77 K),
  • compared to wires with only fine-grained copper, this represents a 12 % lower electrical resistivity for the same UTS (1082 MPa at 77 K), which is provided by the finer copper grains and the silver nanowires,
  • the strength – resistivity trade-off can be fine-tuned simply by adjusting the large grain / fine grain proportion.

Schematic representation of the method and the expected microstructure of the powder, cylinder and wire samples.

UTS vs electrical resistivity at 77 K for wires with diameter from 1 mm to 0.2 mm for W50/50 (), W75/50 () and W100 (). The dotted lines are used to indicate wires with a diameter of 1 mm and the 0.2 mm wire in the case of W50/50.

Publication : S. Tardieu, D. Mesguich, A. Lonjon, F. Lecouturier-Dupouy, N. Ferreira, G. Chevallier, A. Proietti, C. Estournès, C. Laurent, Influence of bimodal copper grain size distribution on electrical resistivity and tensile strength of silver – copper composite wires, Materials Today Communications 107403 (2023)

Contact: simon.tardieu@lncmi.cnrs.fr, florence.lecouturier@lncmi.cnrs.fr

 

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