Abstract
Abstract A study of the dependence of nanoindentation pile-up patterns on the indentation load and crystallographic orientation is presented. Three different orientations—(001), (011), and (111)—of single crystal copper were investigated. Experiments were conducted on a CSM ultra-nanoindentation tester using a Berkovich tip. The topographic images were obtained using an atomic force microscope. The evolution of pile-up patterns with different applied loads was observed. The results show that for applied loads equal to 0.45 mN and smaller the pile-up patterns do not depend on the crystallographic orientation of the indented surface; instead, they depend on the tip’s geometry. On the other hand, in the case of indentation loads bigger than 2 mN, pile-up patterns on the surfaces of (001)-, (011)-, and (111)-oriented single crystals have fourfold, twofold, and sixfold (or threefold) symmetry, respectively. An intermediate state was also reported. Furthermore, a detailed analysis of residual impressions with maximal applied loads equal to 2 mN and bigger reveals that both pile-up and sink-in patterns are present.
Highlights
NANOINDENTATION is a technique which has been used recently to determine the mechanical properties and characterizes the mechanical behavior of materials and thin films at nano- and micro-scales
As outlined in the introduction, the anisotropy associated with nanoindentation of a single crystal in different crystallographic orientations has been intensively studied recently due to the fact that the pile-up and sink-in patterns are significantly different than in the case of isotropic materials
Our results indicate that in the case of small indents, the shapes and spatial locations of the pile-ups which appear on the copper single crystal surfaces are significantly different
Summary
NANOINDENTATION is a technique which has been used recently to determine the mechanical properties and characterizes the mechanical behavior of materials and thin films at nano- and micro-scales. The generation of pile-ups and sinkins in indentation tests is correlated with material properties.[1] Maximum pile-up is observed in the case of elastic-perfectly plastic materials, where strain hardening does not occur. The maximum sink-in appears when the indented material exhibits a strong strain hardening. With moderate strain hardening there is neither pile-up nor sink-in, and the boundary of contact can be determined as a crosssection of the tip under loading and a surface of the sample prior to the deformation. The mode of material deformation in the vicinity of a contact boundary, that is, formation of a pile-up or a sink-in, depends uniquely on the material properties and not on the applied load. Pile-up and sink-in patterns can provide useful information about the mechanical behavior of the investigated material
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