Self-organization of Cu-Ag during controlled severe plastic deformation at high temperatures

Cu90Ag10 alloys were subjected to severe plastic deformation at temperatures ranging from 25 to 400 degrees C and strain rates ranging from 0.1 to 6.25 s(-1) using high-pressure torsion. The deformed samples were characterized by x-ray diffraction, transmission electron microscopy, and atom-probe tomography. A dynamic competition between shear-induced mixing and thermally activated decomposition led to the self-organization of the Cu-Ag system at length scales varying from a few atomic distances at room temperature to approximate to 50 nm at 400 degrees C. Steady-state microstructural length scales were minimally affected by varying the strain rate, although at 400 degrees C, the grain morphology did depend on strain-rate. Our results show that diffusion below 300 degrees C is dominated by nonequilibrium vacancies, and by comparison with previous Kinetic Monte Carlo simulations [D. Schwen et al., J. Mater. Res. 28, 2687-2693 (2013)], their concentration could be obtained.