Indentation of a soft metal film on a hard substrate: strain gradient hardening effects
By R. Saha, Zhenyu Xue, Young Huang, W. Nix. 2001
191 citations recorded by the source corpus.
A new type of nanoindentation experiment showing the effect of a strain gradient on the flow strength of a crystalline material is conducted and analyzed. We show that by indenting a soft metal film (Al) on a hard substrate (glass) with a sharp diamond indenter a strong gradient of plastic strain is created. The true hardness of the film is observed to increase with increasing depth of indentation when the indenter tip approaches the hard substrate, in sharp contrast to the falling hardness with increasing depth in bulk materials. We associate this rise in hardness with the strong gradient of plastic strain created between the indenter and the hard substrate. We use the mechanism-based strain gradient (MSG) plasticity theory to model the observed indentation behavior. The modeling shows that the MSG plasticity theory is capable of describing not only the decreasing hardness with increasing depth of indentation at shallow indentations, as observed in bulk materials, but also the rise in hardness that occurs when the indenter tip approaches the film/substrate interface.
Subfields: Materials Chemistry, Mechanics of Materials
View Paper: https://www.semanticscholar.org/paper/22304694d09b65003ddb429f28263da6571bf971
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In Materials Chemistry
- R. A. Abu Al-Rub
- George Z. Voyiadjis
- Han Li
- J. Vlassak
- Sun-Myung Kim
- M. Yaghoobi
- R. Peters
- S. Forest
In Mechanics of Materials
Citations in the corpus
- Determining the elastic modulus and hardness of an ultra-thin film on a substrate using nanoindentation (2009, background): “It is not clear at present whether this deviation is caused by the constraining effect of the silicon substrate on plastic flow in the coating [29] or because the analysis method loses accuracy when the indenter tip depth approaches the film/substrate interface.”
- Gradient plasticity theory with a variable length scale parameter (2005, background): “2(b) and (c)), where four values of ‘ are used to fit well the experimental results of Shrotriya et al. (2003). This confirms that ‘ is not a fixed parameter but it depends on the microstructure of the material.”