Room temperature electron beam sensitive viscoplastic response of ultra-ductile amorphous olivine films
(2024) EMMC19 - 19th European Mechanics of Materials Conference — Location: Madrid, Spain (29.May.2024)
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- Recent studies demonstrating amorphization of olivine under high-stress have raised interest in the mechanical properties of amorphous olivine (a-olivine) [1, 2]. In this study we investigate the mechanical properties of amorphous olivine deformed at room temperature either ex situ by nanoindentation, or in situ in a TEM under uniaxial tension using a Push-to-Pull (PTP) device. Thin films of a-olivine were deposited by pulsed laser deposition (PLD). In nanoindentation, a-olivine a-olivine exhibit a viscoelastic-viscoplastic behavior without fracture. Long-term relaxation tests show a strain-rate sensitivity m∼0. 05 [3]. Under uniaxial tension in situ in the TEM, a-olivine deforms plastically but with a gradual transition that makes impossible the determination of a precise threshold. The strength attains values up to 2.5 GPa. The fracture strain reaches values close to 30 % without e-beam irradiation. Under electron illumination at 200 kV, the strength is lower, around 1.7 GPa while higher elongations close to 36 % are obtained. Alternating beam-off and beam-on sequences lead to exceptionally large fracture strains equal to 68 % at 200 kV and 139 % at 80 kV. EELS measurements were performed to characterize the interaction between the electron beam and a-olivine. At a voltage of 80 kV, radiolysis accompanied by oxygen release dominates whereas at high voltage the interaction is dominated by knock-on type defects. Radiolysis is also the dominant interaction mechanism at 200 kV with low exposition which corresponds to most of our deformation experiments. [1] K. Kranjc et al. (2020). Amorphization and plasticity of olivine during low‐temperature micropillar deformation experiments. Journal of Geophysical Research: Solid Earth, 125, e2019JB019242. [2] V. Samae et al. (2021) Stress-induced amorphization triggers deformation in the lithospheric mantle. Nature 591, 82–86. [3] P. Baral et al. (2021) Rheology of amorphous olivine thin films characterized by nanoindentation. Acta Materialia, 219, 117257.
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Cordier, P., Orekhov, A., Gauquelin, N., Kermouche, G., Baral, P., Dohmen, R., Coulombier, M., Verbeeck, J., Raskin, J.-P., Pardoen, T., Schryvers, D., & Idrissi, H. (2024). Room temperature electron beam sensitive viscoplastic response of ultra-ductile amorphous olivine films. EMMC19 - 19th European Mechanics of Materials Conference, Madrid, Spain. https://hdl.handle.net/2078.5/238815