Nanoengineering the glassy state: toward novel thin film metallic glasses with outstanding combination of mechanical properties
Résumé
Thin film metallic glasses (TFMGs) are emerging materials characterized by a unique combination of mechanical involving large yield strength (~3 GPa) and large ductility (>10%) [1]. Nevertheless, the synthesis of advanced TFMGs with engineered microstructure and the understanding of their mechanical properties are barely tackled. Here, I will present recent results involving two (2) strategies to develop nanoengineered TFMGs with a controlled microstructure down to the atomic scale, resulting in outstanding and tunable mechanical properties.
Firstly, I will show the potential of Pulsed Laser Deposition (PLD) as a novel technique to synthetize nanostructured Zr50Cu50 (%at.) TFMGs. I will show how the control of PLD process parameters enables to synthetize a variety of film microstructures, e.g. compact fully amorphous and amorphous nanogranular, showing large free volume (Fig. a) [2]. This results in unique mechanical behavior as shown by in situ TEM/SEM tensile/compression tests, reporting homogeneous deformation for nanogranular TFMGs combined with large yield strength (>3 GPa) and ductility (>9%) [2].
In the second case, I will focus on the fabrication of multilayers with nanoscale period alternating either fully amorphous or amorphous/crystalline sublayers (Fig. b). I will show how the control of the sublayer thickness influences the deformation behavior affecting shear bands formation and tuning the mechanical properties. As an example, alternating CrCoNi (crystalline)/TiZrNbHf (amorphous) nanolayers results in an ultrahigh compressive yield strength (3.6 GPa) and large homogeneous deformation (~15%) [3].
References:
[1] M. Ghidelli et al. Acta Mater., 131, 246, 2017.
[2] M. Ghidelli et al. Acta Mater., 213, 116955, 2021.
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