Effects of size and geometry on the plasticity of high strength copper/tantalum nanofilamentary conductors obtained by severe plastic deformation

Vanessa Vidal (1, 2) , Ludovic Thilly (2) , Florence Lecouturier (1) , Pierre-Olivier Renault (2)

1 LNCMP - Laboratoire National des Champs Magnétiques Pulsés
2 LMP - Laboratoire de métallurgie physique

Copper-based high-strength nanofilamentary wires reinforced by tantalum nanofilaments were prepared by severe plastic deformation (repeated hot extrusion and cold drawing steps) to be used in the windings of high-pulsed magnets. This application requires a complete characterization of the microstructure and the strength and their relationship for further optimization: after heavy strain, the Cu matrix is nanostructured and the Ta nanofilaments develop a strong ribbon-like shape resulting in an early microstructural refinement. The macroscopic strength is greater than rule-of-mixture predictions as confirmed by nanohardness values. The observed size effect is related to the dislocation starvation in the nanostructured materials combined with the barrier role of Cu/Ta interfaces. The strengthening is lower, however, as expected, because of the distorted ribbon morphology of the Ta filaments preventing them from behaving as nanowhiskers, as Nb fibers do in Cu/Nb wires. This shows that size and geometry play key roles in the plasticity of nanomaterials.

Mots clés: Severe plastic deformation; Nanoindentation; TEM; Nanostructure; Fiber-reinforced composites

Domaines: Supraconductivité [cond-mat.supr-con]

Vanessa Vidal, Ludovic Thilly, Florence Lecouturier, Pierre-Olivier Renault. Effects of size and geometry on the plasticity of high strength copper/tantalum nanofilamentary conductors obtained by severe plastic deformation. Acta Materialia, 2006, 54 (4), pp.1063-1075. ⟨10.1016/j.actamat.2005.10.031⟩. ⟨hal-00118779⟩