Brittleness study of intermetallic (Cu, Al) layers in copper-clad aluminium thin wires

Heat treatments performed on copper-clad aluminium thin wires increase the ductility of copper and aluminium but activate diffusion between both layers, creating brittle intermetallic compounds. Ductility reaches a maximum for an optimal intermetallic thickness related to appropriate annealing conditions in order to avoid Kirkendall void formation assisted by stress gradients.