About this Abstract |
Meeting |
2021 TMS Annual Meeting & Exhibition
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Symposium
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Advanced Characterization Techniques for Quantifying and Modeling Deformation
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Presentation Title |
Revisiting the Origin of Indentation Size Effect at Sub-micrometer Scales |
Author(s) |
Xiaolong Ma, Wesley Higgins, Zhiyuan Liang, Dexin Zhao, George M Pharr, Kelvin Y. Xie |
On-Site Speaker (Planned) |
Xiaolong Ma |
Abstract Scope |
Understanding the size effect in indentation testing is crucial to interpreting the mechanical behavior of materials in the small world. The Nix-Gao model and its derivatives, based on the strain gradient assumption, have been widely used to explain the depth-dependent indentation hardness and agree quite well with results from micro-indentation experiments. However, experimental behavior below 1 um starts to deviate from its predictions as depth becomes small. Here, using precession electron diffraction techniques, we characterize the microstructure evolution underneath indents from 100nm to 800nm. We show that dislocations appear relatively more mobile during very low-depth indentation and thus less constrained in the conventionally perceived deformation volume. A mechanism transition from source-limited hardening to dislocation Taylor hardening at the nanometer scale is hypothesized to explain the deviation from the Nix-Gao model. Further indentation experiments on samples with high and low initial dislocation densities lend further support to the hypothesis. |
Proceedings Inclusion? |
Planned: |
Keywords |
Nanotechnology, Characterization, Other |