The effects that arose when crystalline materials were mechanically deformed in small volumes were considered. It was shown that indentation-size effects at the μm-scale could be understood in terms of the hardening associated with strain gradients andgeometrically necessary dislocations. Indentation-size effects at the nm-scale involved the concepts of dislocation starvation and dislocation nucleation. Uniaxial compression experiments on μm-sized pillars of single-crystal Au were also described and surprisingly strong size-effects were found; even though no significant strain-gradients were present and the crystals were not initially dislocation-free. It was argued that these size effects were caused by dislocation starvation hardening; with dislocations leaving the crystal more quickly than they multiplied and thus leading to the requirement of continuous dislocation nucleation during deformation. A new length-scale for plasticity - the distance which a dislocation travelled before it created another - arose naturally. Hardening of crystals smaller than this characteristic size was expected to be dominated by dislocation starvation. Crystals which were much larger than this size were expected to exhibit normal dislocation plasticity.

Deformation at the Nanometer and Micrometer Length Scales - Effects of Strain Gradients and Dislocation Starvation. W.D.Nix, J.R.Greer, G.Feng, E.T.Lilleodden: Thin Solid Films, 2007, 515[6], 3152-7