Correlation between dislocation density and pop-in phenomena in aluminum studied by nanoindentation and electron channeling contrast imaging

A combination of electron channeling contrast imaging and nanoindentation tests was conducted to reveal the interconnected nature of the pop-in (yield point phenomena) with the underlying dislocation substructure in aluminum. Using digital image processing, it was possible to reveal the dislocation substructure in a bulk sample. It is shown that a very low dislocation density is necessary to observe the pop-in, and at high dislocation density the dislocation sources become activated instead of dislocation nucleation.