Modelisation multi-´ echelle du comportement ´ de nano-composites Cu-Nb

Multiscale modeling of the electrical behavior of Cu-Nb nano- composites. Nanostructured and architectured copper niobium composite wires are very good candidates for the generation of very high magnetic fields as they combine both high strength and high electrical conductivity. They are fabricated by co-deformation of a Cu-Nb composite assembly. A multiscale microstructure formed by 85 3 Cu-Nb elementary patterns with dimensions of the order of nanometers, is obtained. In order to investigate the link between the effective electrical conductivity and the wire microstructure, two homogenization methods are applied: first, using a mean field theory (generalized self-consistent model) in which a microstructure formed by co-cylindrical long fibers with a random distribution is considered, and second a full field method (Finite Elements) in which the periodic character of the experimental microstructure is taken into account. The size effect of components (nm), temperature, and dislocation density are taken into account into the definition of the local conductivity. The multiscale character of the material is taken into consideration through an iterative process. The longitudinal and transverse effective conductivities obtained by both methods perfectly match with each other, showing the limited influence of the effect of fiber distribution for this behavior. Results also compare well with the available experimental data.