Mechanical alloying and amorphization in Cu–Nb–Ag in situ composite wires studied by transmission electron microscopy and atom probe tomography

We have studied deformation-driven alloying in a Cu–5 at.% Ag–3 at.% Nb in situ composite by transmission electron microscopy and atom probe tomography. In addition to alloying at interfaces, amorphization of nanosized Cu areas was observed after heavy wire drawing (true strain: η = 10.5) at some of the Cu–Nb interfaces. We discuss the alloying in terms of trans-phase dislocation-shuffling and shear banding mechanisms where lattice dislocations penetrate the interfaces between abutting phases. We interpret local amorphization in terms of the thermodynamic destabilization of a Cu–Nb crystalline phase between 35 and 80 at.% Cu due to enforced mixing. Deformation-driven mechanical alloying and amorphization are hence closely associated phenomena.