The indentation size effect of single-crystalline tungsten revisited

Abstract

In this study, we have investigated the indentation size effect (ISE) of single crystalline tungsten with low defect density. As expected, the hardness shows a pronounced increase with decreasing indentation depth as well as a strong strain rate dependence. For penetration depths greater than about 300 nm, the ISE is well captured by the Nix–Gao model in the context of geometrically necessary dislocations. However, clear deviations from the model are observed in the low depth regime resulting in a bilinear effect. The hardness behavior in the low depth regime can be modeled assuming a non-uniform spacing of the geometrically necessary dislocations. We propose that the bilinear indentation size effect observed reflects the evolution of the geometrically necessary dislocation density. With increasing strain rate, the bilinear effect becomes less pronounced. This observation can be rationalized by the activation of different slip systems. Graphic abstract

Indentation Size Effect in CoCrFeMnNi HEA Prepared by Various Techniques

“…The overestimation of hardness at low depths by this model is believed to be caused by the strong repulsive force between GNDs [ 25 ]. Various models taking into account the spread of the GNDs out of the supposed volume by its extension, limiting the maximum density of GNDs, or their non-uniform distribution, were proposed [ 26 , 27 , 28 , 29 , 30 , 31 ].…”

Current trends in nanomechanical testing research

“…In 2002, it became the first and, to date, the only nanomechanical testing method sanctioned with an ISO norm (ISO:14,577 [7]). Still, a non-negligible number of the contributions to this focus issue are devoted to further improving its reliability [8][9][10][11][12][13], based on emerging technologies. These include more accurate imaging [8,10,11] and faster data processing [9], which, for example, allow for improved characterization of the geometry of the indenter tip and the resulting contact area.…”

Experimental investigations and FE modeling considering microstructural inhomogeneity of laser welded steel-aluminum joints

“…H 0 in this equation was the macroscopic hardness. Nevertheless, the Nix-Gao model was widely applied to capture the ISE over indentation depths ranging from several micrometers to some hundred nanometers [55]. Thus, in this work the hardness values H 0 were obtained from the experimentally determined loading-unloading curve, as shown in Fig.…”