About this Abstract |
| Meeting |
2026 TMS Annual Meeting & Exhibition
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| Symposium
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Fracture and Deformation Across Length Scales: Celebrating the Legacy of William Gerberich
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| Presentation Title |
Effects of Grain Size on Plasticity Mechanisms of Nanocrystalline MgAl₂O₄ Spinel under Nanoindentation: Hall-Petch vs. Inverse Hall-Petch |
| Author(s) |
Zachary S Arenella, Sarshad Rommel, Zachary Aitken, Heonjune Ryou, James A Wollmershauser, Edward P Gorzkowski, Boris N Feigelson, Yong-Wei Zhang, Mark Aindow, Seok-Woo Lee |
| On-Site Speaker (Planned) |
Zachary S Arenella |
| Abstract Scope |
Understanding how grain size affects the mechanical properties of nanocrystalline magnesium aluminate (MgAl₂O₄) spinel is vital for its transparent structural applications. This study examines MgAl₂O₄ samples with grain sizes ranging from 3.7 to 80 nm, synthesized via environmentally controlled pressure-assisted sintering. Nanoindentation testing investigated plasticity mechanisms across the Hall-Petch regime (80 nm), inverse Hall-Petch regime (3.7 nm), and the transition zone (10.5 nm). Transmission electron microscopy of the 80 nm sample revealed dislocation plasticity, local lattice distortion, and grain boundary decohesion. In contrast, the 3.7 nm sample showed no dislocation activity, even beneath indents, with plastic deformation occurring primarily through shear banding. Atomic-scale grain boundary decohesion was also observed within shear bands. Atomistic simulations confirmed that, in the 3.7 nm sample, plastic strain developed at grain boundaries without dislocation nucleation. These findings demonstrate that grain boundary sliding and shear banding govern plasticity in the inverse Hall-Petch regime, providing new insight into the deformation mechanisms of nanocrystalline ceramics. |
| Proceedings Inclusion? |
Planned: |
| Keywords |
Mechanical Properties, Modeling and Simulation, Characterization |