About this Abstract |
Meeting |
2024 TMS Annual Meeting & Exhibition
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Symposium
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Mechanical Behavior at the Nanoscale VII
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Presentation Title |
Grain Size Effect on Microstructural Evolution in Nanocrystalline MgAl2O4 under Nanoindentation |
Author(s) |
Zachary Arenella, James A Wollmershauser, Edward P Gorzkowski, Boris N Feigelson, Seok-Woo Lee |
On-Site Speaker (Planned) |
Zachary Arenella |
Abstract Scope |
To develop transparent materials with superior mechanical properties, nanocrystalline magnesium aluminate (MgAl2O4) spinel with grain sizes ranging from 3.7 to 80nm has been synthesized by environmentally controlled pressure assisted sintering. In this study, we investigated the grain size dependence of microstructural changes during nanoindentation by performing high-resolution transmission electron microscopy (TEM). Hardness data show that the transition from the Hall-Petch relation to the inverse Hall-Petch relation occurs at 10.5nm in grain size. TEM analysis confirms that for grain sizes below 10.5nm, dislocation plasticity is completely suppressed, and grain-boundary (GB) assisted mechanisms control plasticity. Unlike in nanocrystalline metals, GB plasticity does not cause any noticeable structural changes associated with grain growth, amorphization, or the accumulation of residual stress even after extensive amounts of plasticity. The conservation of overall microstructure in the inverse Hall-Petch regime will be discussed in terms of a cooperative grain boundary sliding and migration process. |
Proceedings Inclusion? |
Planned: |
Keywords |
Mechanical Properties, Thin Films and Interfaces, Characterization |