A transmission electron microscopic study of the dislocation distribution under an indentation revealed that a complex sequence of loop nucleation, cross-slip and re-nucleation resulted in a cross-like network at the free surface and a square-like network below. These distributions comprised 2 types of dislocation. These were redundant dislocations that were responsible for general plasticity and work hardening, and shielding dislocations that were responsible for the equilibrium of forces. The former were about an order of magnitude more prevalent. The total number of dislocations was consistent with continuum plasticity theory, while the shielding density was consistent with a super-dislocation pile-up model.

W.Zielinski, H.Huang, S.Venkataraman, W.W.Gerberich: Philosophical Magazine A, 1995, 72[5], 1221-37