Superstrength through nanotwinning
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Authors
An, Qi
Goddard III, William A.
Xie, Kelvin Y.
Sim, Gi-dong
Hemker, Kevin J.
Munhollon, Tyler
Toksoy, M. Fatih
Haber, Richard A.
Issue Date
2016
Type
Citation
Language
Keywords
Deformation mechanism , DFT , hardness , nanoindentation , Superhard ceramics
Alternative Title
Abstract
The theoretical strength of a material is the minimum stress to deform or fracture the perfect single crystal material that has no defects. This theoretical strength is considered as an upper bound on the attainable strength for a real crystal. In contradiction to this expectation, we use quantum mechanics (QM) simulations to show that for the boron carbide (B4C) hard ceramic, this theoretical shear strength can be exceeded by 11% by imposing nano-scale twins. We also predict from QM that the indentation strength of nano-twinned B4C is 12% higher than that of the perfect crystal. Further we validate this effect experimentally, showing that nano-twinned samples are harder by 2.3% than the twin-free counterpart of B4C. The origin of this strengthening mechanism is suppression of twin boundary (TB) slip within the nano-twins due to the directional nature of covalent bonds at the TB.
Description
Citation
Publisher
American Chemical Society
License
In Copyright
Journal
Volume
Issue
PubMed ID
ISSN
1530-6984