Percolating network of ultrafast transport channels in severely deformed nanocrystalline metals

Severe plastic deformation is nowadays used to produce sizable amounts of bulk nanocrystalline materials, which render them suitable for innovative applications ranging from biomedical implants to off-shore or aerospace structures, owing to favorable combinations of high mechanical strength and enhanced ductility they offer. Enhanced atom diffusion along internal interfaces is largely responsible for the resulting property combinations. Severe plastic deformation processing of metals is demonstrated to create bulk nanostructured materials with a hierarchy of internal interfaces. On top of that, specific diffusion channels providing pathways for ultrafast transport of atoms have been identified. The defects that represent the constituents of the fast diffusion network were visualized by means of the focused ion beam technique. Nonequilibrium grain boundaries, nonequilibrium triple junctions, and microvoids/microcracks compose the percolating network of ultrafast diffusion channels, which represent an important and newly recognized feature of severely deformed materials. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3211966]