Room temperature electron beam sensitive viscoplastic response of ultra-ductile Al/a-Al2O3 model system
(2024) EMMC19 - 19th European Mechanics of Materials Conference — Location: Madrid, Spain (29.May.2024)
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- Authors
Kashiwar, Ankush 
- Abstract
- Hybrid nanolaminates (NLs) consisting of alternating layers of metal and metal oxide exhibit excellent mechanical properties and resistance to irradiation damage, which are critical for various structural and functional applications. The strength and ductility of NLs very much depend on layer thicknesses and interfacial characteristics. Investigations by in situ nanomechanical testing in a transmission electron microscope (TEM) are extremely valuable in relating the mechanisms of deformation and failure to microstructural evolutions within individual layers as well as at the interfaces. In addition, the influence of the electron beam irradiation (EBI) must be assessed to evaluate possible artifacts but also to enlarge the range of test conditions. Here, we address Al/Al2O3/Al tri-layer model systems involving two amorphous/crystal interfaces that exhibit enhanced ductility over 50% with a high ultimate tensile strength above 1550 MPa under uniaxial tension. The extreme plasticity results from the time-dependent viscoplastic response under low-strain rate (10-6 s-1) deformation which is very much controlled by EBI. The influence of EBI on the stress-strain behavior was systematically confirmed by switching on and off the electron beam which led to drastic changes in the mechanical response. The microstructure of the NL deformed under beam-on was characterized by significant delocalization of the plasticity. Intriguingly, both Al-layers exhibited localized necking at the majority of grain boundaries (GBs). This suggests that GB diffusion creep is the dominant mechanism operating at low-strain rates and this feature did not manifest itself in samples deformed at higher strain rates or in the absence of EBI. Furthermore, the localized plasticity at GBs is associated with GB migration which we have analyzed in our study based on the novel combination of nanoscale digital image correlation (DIC) with nanomechanical testing inside TEM. The role of the crystal/amorphous interface and the transmission of plasticity at this interface is also discussed.
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Citations
Kashiwar, A., Orekhov, A., UI Haq, I., Coulombier, M., Raskin, J.-P., Schryvers, D., Pardoen, T., & Idrissi, H. (2024). Room temperature electron beam sensitive viscoplastic response of ultra-ductile Al/a-Al2O3 model system. EMMC19 - 19th European Mechanics of Materials Conference, Madrid, Spain. https://hdl.handle.net/2078.5/238813