Diffusion in ultra-fine-grained CoCrFeNiMn high entropy alloy processed by equal-channel angular pressing

Grain boundary diffusion in severely plastically deformed (SPD) CoCrFeMnNi high entropy alloy (HEA) has been studied by applying the tracer diffusion technique. After two passes of equal channel angular pressing (ECAP), three untra-fast diffusion paths in ECAP-processed CoCrFeMnNi HEA were distinguished, which were identified with twin boundaries, high-angle grain boundaries and porosity defects. The enhanced diffusivity is induced by a high strain localization in the vicinity of interfaces in a deformation-induced non-equilibrium state that is correlated with the pronounced deformation twinning due to the low stacking fault energy of the material.