期刊
SCIENCE ADVANCES
卷 7, 期 8, 页码 -出版社
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/sciadv.abc6714
关键词
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资金
- MOST 973 of China [2015CB856800]
- National Natural Science Foundation of China [11327902, 51271113, 11704245, 51821001, 51850410501]
- fusion research program of World Premier International Research Center (WPI) Initiative by MEXT, Japan
- Whiting School of Engineering
- Johns Hopkins University
- NSF (NSF) [NSF-DMR-1804320]
The onset of shear amorphization in single-crystal boron carbide was experimentally measured through nanoindentation and transmission electron microscopy. It was found that rate-dependent loading discontinuity in nanoindentation load-displacement curves results from the formation of nanosized amorphous bands via shear amorphization. Stochastic analysis of the pop-in events revealed characteristics such as exceptionally small activation volume, slow nucleation rate, and lower activation energy, indicating that the high-pressure structural transition is activated and initiated by dislocation nucleation.
The failure of superhard materials is often associated with stress-induced amorphization. However, the underlying mechanisms of the structural evolution remain largely unknown. Here, we report the experimental measurements of the onset of shear amorphization in single-crystal boron carbide by nanoindentation and transmission electron microscopy. We verified that rate-dependent loading discontinuity, i.e., pop-in, in nanoindentation load-displacement curves results from the formation of nanosized amorphous bands via shear amorphization. Stochastic analysis of the pop-in events reveals an exceptionally small activation volume, slow nucleation rate, and lower activation energy of the shear amorphization, suggesting that the high-pressure structural transition is activated and initiated by dislocation nucleation. This dislocation-mediated amorphization has important implications in understanding the failure mechanisms of superhard materials at stresses far below their theoretical strengths.
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