Size effect in nanoindentation: Taylor hardening or dislocation source-limited effect?

Abstract

In the present work, a 3D discrete dislocation dynamics (DDD) method was used to explore the indentation size effect (ISE) in the nanoindentation of single crystals. The distribution of geometrically necessary dislocation (GND) underneath the indent obtained from the DDD simulations was compared with that in experiments. The results show that the GND density increases as the indentation depth increases, which is inconsistent with the Nix-Gao model that is usually used to interpret the ISE phenomenon. The spatial-temporal evolution of dislocation structures indicates that the available dislocation sources are limited at smaller indentation depths, thus requiring higher stress to accommodate the plastic deformation. The authors do not have permission to share data. • The indentation size effect was investigated by 3D discrete dislocation dynamics. • The patterns of GNDs are correlated with the dislocation motions on slip planes. • The GND density increases as the indentation depth increases. • The indentation size effect is caused by the limitation of dislocation sources.