Mechanical alloying of Cu and Fe induced by severe plastic deformation of a Cu-Fe composite

A filamentary composite elaborated by cold drawing was processed by high pressure and torsion (HPT). The nanostructure resulting from this severe plastic deformation (SPD) was investigated thanks to scanning electron microscopy, transmission electron microscopy, X-ray diffraction and 3D atom probe. Although the mutual solubility of Cu and Fe is extremely low at room temperature in equilibrium conditions, it is shown that nanoscaled Fe clusters dissolve in the Cu matrix. The non-equilibrium copper supersaturated solid solutions contain up to 20 at.% Fe. The driving force of the dissolution is attributed to capillary pressures and mechanisms which could enhance the atomic mobility during HPT are discussed. We conclude that the interdiffusion is the result of a dramatic increase of the vacancy concentration during SPD.