A combination of electron channelling contrast imaging and nano-indentation 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 was shown that a very low dislocation density was necessary to observe the pop-in, and at high dislocation density the dislocation sources become activated instead of dislocation nucleation.

Correlation between Dislocation Density and Pop-In Phenomena in Aluminum Studied by Nanoindentation and Electron Channeling Contrast Imaging. A.Barnoush, M.T.Welsch, H.Vehoff: Scripta Materialia, 2010, 63[5], 465-8