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Deformation in Nanocrystalline Ceramics: A Microstructural Study

23 Pages Posted: 3 Jul 2019 First Look: Accepted

See all articles by Barak Ratzker

Barak Ratzker

Ben-Gurion University of the Negev - Department of Materials Engineering

Avital Wagner

Ben-Gurion University of the Negev - Department of Materials Engineering

Maxim Sokol

Drexel University - Department of Materials Science and Engineering

Louisa Meshi

Ben-Gurion University of the Negev - Department of Materials Engineering

Sergey Kalabukhov

Ben-Gurion University of the Negev - Department of Materials Engineering

Nachum Frage

Ben-Gurion University of the Negev - Department of Materials Engineering

Abstract

Contrary to the characteristic strengthening of polycrystalline ceramics with a decrease in grain size, extremely fine nanocrystalline ceramics exhibit softening, increased plasticity and sometimes an inverse Hall-Petch relation. Despite experimental evidence, questions remain regarding the underlying deformation mechanisms governing this abnormal mechanical behavior. In the present study, an in-depth microstructural examination was performed on nanostructured transparent magnesium aluminate spinel (MgAl2O4) subjected to microhardness tests. Microstructural observations revealed regions strained to various degrees below the point of indentation, containing varying amounts of dislocations and nano-cavities. Furthermore, the residual strain in different areas was estimated by local electron diffraction. This provided evidence supporting the roles of both dislocation motion and grain boundary sliding (GBS) mechanisms. Moreover, shear bands formed and were found to be associated with micro-cracking. By combining the microstructural analysis with suitable models, it was concluded that these mechanisms govern plastic deformation. By elucidating how strain is accommodated within nanocrystalline ceramics, a deeper understanding of their unique mechanical behavior is gained.

Keywords: nanocrystalline ceramics, indentation, dislocations, grain boundary sliding, shear bands

Suggested Citation

Ratzker, Barak and Wagner, Avital and Sokol, Maxim and Meshi, Louisa and Kalabukhov, Sergey and Frage, Nachum, Deformation in Nanocrystalline Ceramics: A Microstructural Study (July 3, 2019). Available at SSRN: https://ssrn.com/abstract=3414008 or http://dx.doi.org/10.2139/ssrn.3414008

Barak Ratzker (Contact Author)

Ben-Gurion University of the Negev - Department of Materials Engineering

Israel

Avital Wagner

Ben-Gurion University of the Negev - Department of Materials Engineering

Israel

Maxim Sokol

Drexel University - Department of Materials Science and Engineering

Philadelphia, PA 19104
United States

Louisa Meshi

Ben-Gurion University of the Negev - Department of Materials Engineering

Israel

Sergey Kalabukhov

Ben-Gurion University of the Negev - Department of Materials Engineering

Israel

Nachum Frage

Ben-Gurion University of the Negev - Department of Materials Engineering ( email )

Israel

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