Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9795961 | Materials Science and Engineering: A | 2005 | 10 Pages |
Abstract
This paper presents the results of an experimental study of indentation size effects in Au, Ag and Ni single crystals with (0 0 1), (0 1 1) and (1 1 1) orientations. The studies show clearly that the hardness increases with decreasing indentation size, for indents between â¼30 and 600 nm in depth. The observed size dependence is rationalized using the mechanism-based strain gradient plasticity theory by Nix and Gao. The shape and extent of material pile-up is shown to depend strongly on the material hardness and crystal orientation. In the case of (0 0 1) oriented crystals, the extent of material pile-up is low in Ag, compared to that in the Au and Ni crystals. The material pile-up profiles are conventional three-lobes shapes. However, for indents in (0 1 1) crystals, butterfly shaped pile-up profiles are observed in Ni, compared to conventional pile-up profiles in Au and Ag. In contrast, flower shaped pile-up profiles are observed in (1 1 1) Ni crystals, compared to conventional pile-up profiles in Au and Ag. Displacement bursts are also shown to occur in (0 1 1) and (1 1 1) oriented Ni at indentation load levels of â¼80-100 μN. These are attributed to the initial onset of dislocation slip activity, when the shear stress exceeds the estimated theoretical shear strengths of the materials.
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Physical Sciences and Engineering
Materials Science
Materials Science (General)
Authors
Zong Zong, Wole Soboyejo,