Forced chemical mixing of immiscible Ag-Cu heterointerfaces using high-pressure torsion

Forced chemical mixing in nanostructured Ag₆₀Cu₄₀ eutectic alloys during severe plastic deformation by high-pressure torsion (HPT) was quantitatively studied using x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. Nearly complete chemical homogenization of the original lamellar structure with a wavelength of ≈ 165 nm was achieved after a shear strain of ≈ 350. The chemical mixing is accompanied by extensive grain refinement leading to nanocrystalline grains with average sizes of ≈ 42 nm. A Monte Carlo computer simulation model, which attributes mixing to dislocation glide, shows reasonable agreement with the experimental results. The model also shows that the characteristic strain for chemical homogenization scales linearly with the length scale of the system L, and not with the square of the length scale L², as would be expected for Fickian diffusion.