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Size Effect and Geometrical Effect of Polycrystals and Thin Film/Substrate System in Micro-indentation Test

Published online by Cambridge University Press:  01 February 2011

Y. Wei ,
M. Zhao ,
X. Wang  and
S. Tang
Y. Wei
Affiliation:
LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China
M. Zhao
Affiliation:
LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China
X. Wang
Affiliation:
LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China
S. Tang
Affiliation:
LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China
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Abstract

Micro-indentation test at scales on the order of sub-micron has shown that the measured hardness increases strongly with decreasing indent depth or indent size, which is frequently referred to as the size effect. Simultaneously, at micron or sub-micron scale, the material microstructure size also has an important influence on the measured hardness. This kind of effect, such as the crystal grain size effect, thin film thickness effect, etc., is called the geometrical effect. In the present research, in order to investigate the size effect and the geometrical effect, the micro-indentation experiments are carried out respectively for single crystal copper and aluminum, for polycrystal aluminum, as well as for a thin film/substrate system, Ti/Si3N4. The size effect and geometrical effect are displayed experimentally. Moreover, using strain gradient plasticity theory, the size effect and the geometrical effect are simulated. Through comparing experimental results with simulation results, the length-scale parameter appearing in the strain gradient theory for different cases is predicted. Furthermore, the size effect and the geometrical effect are interpreted using the geometrically necessary dislocation concept and the discrete dislocation theory.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 731: Symposium W – Modeling and Numerical Simulation of Materials Behavior and Evolution , 2002 , W8.16
Copyright
Copyright © Materials Research Society 2002

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