Atomic force microscopy was used to study slip step patterns, which form around indentations in FCC alloys. These patterns form in a consistent and repeatable manner. From these observations it was determined that slip steps increased in height only in the outer region of the plastic zone leading to the cessation of their growth as the plastic zone expands outward. Electron back-scattering diffraction techniques were used to map grain orientation and the effect of different surface orientations as well as different tip geometries on slip step behavior was explored. Changes in resolved shear stress on different slip planes could be observed qualitatively from changes in the slip step patterns as surface orientation and tip geometry were varied. Pile up was shown to form above the regions with the largest amounts of strain downward into the bulk. Changes in slip step patterns could be predicted based upon changes in resolved shear stress. Discreet dislocation dynamics simulations were performed to support these observations.

Analysis of Dislocation Mechanisms around Indentations through Slip Step Observations. K.A.Nibur, F.Akasheh, D.F.Bahr: Journal of Materials Science, 2007, 42[3], 889-900