It was recalled that nano-phase metals possessed grain-size dependent mechanical properties that were significantly different to those of the coarse-grained equivalents. Pure metals were much stronger, and apparently less ductile, than conventional ones. Intermetallics were also strengthened, but they tended towards an increased ductility at the smallest grain sizes. Such property changes were related mainly to the grain size, but they were also affected by the large percentage of atoms in grain boundaries and other microstructural features. Strengthening appeared to result from a limitation of dislocation activity, while an increased ductility probably resulted from grain-boundary sliding.

R.W.Siegel, G.E.Fougere: Nanostructured Materials, 1995, 6[1-4], 205-16