Persistence of ultrafast atomic diffusion paths in recrystallizing ultrafine grained Ni

Tracer self-diffusion is investigated in ultrafine grained Ni prepared by high pressure torsion. Under identical diffusion annealing conditions the ultrafine grained structure of less pure Ni remains stable, while recrystallization and subsequent grain growth occur in high purity Ni. Nevertheless, qualitatively similar ultrafast diffusion rates are measured in the samples of both purity levels. A model explaining retention of deformation-induced ultrafast diffusion paths in recrystallized Ni in terms of solute redistribution in front of the moving boundary is suggested.