INT-Seminar "Toward microstructural design thin metallic glass films with tunable mechanical properties" by Dr. Matteo Ghidelli, Department of Structure and Nano/-Micromechanics of Materials, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany

Introduction: Prof. Horst Hahn

Abstract:

Thin film metallic glasses (TFMGs) are emerging materials characterized by outstanding mechanical properties with a mutual combination of high strength (close to the theoretical limit) and ductility (> 10%) [1]. However, several scientific challenges arise when dealing with sub-micrometer size specimens among which the difficulty of manipulation/testing hindering the comprehension of the size dependent mechanical behavior. In addition, the control of mechanical properties based on a microstructural design represents a relative new concept for TFMGs, opening fascinating scenarios for advanced applications.

In this talk, I will cover several aspects of the synthesis and mechanical behavior of TFMGs, focusing on (i) the thickness-dependent mechanical properties and on (ii) the development of novel nanostructured TFMGs with tunable mechanical properties.

First, I will discuss the mechanical properties of freestanding Zr₆₅Ni₃₅ (%at.) TFMGs using an innovative method based on residual stress actuated micro-tensile set-up. I will show that TFMGs can sustain large homogenous deformation (~15%) without catastrophic shear banding, while the yield strength reaches the theoretical limit of ~3 GPa [2]. Then, I will discuss the fundamental plasticity mechanisms at the nanoscale showing that TFMGs report a fine short range order, with dense ~2-3 nm Zr/Ni-rich clusters, which is progressively disrupted by increasing the plastic deformation, but without formation of mature shear bands [3].

In the second part of the talk, I will present recent results related with the synthesis of nanostructured Zr₅₀Cu₅₀ (%at.) TFMGs by Pulsed Laser Deposition (PLD). I will show how is possible to synthetize different film microstructures including compact fully amorphous, amorphous nano-porous, and amorphous embedded with nanocrystals, all reporting a unique self-assembled nano-laminated atomic structure, alternating Zr-rich and Cu-rich layers. Then, I will discuss the mechanical properties and how the product yield strength/ductility can be modulated by controlling the nanoporosity content reaching the outstanding values of 3 GPa and 9%, respectively. Finally, I will show how these materials can be used for promising applications in wearable electronics.

[1] L. Tian et al., Nat. Commun. 3:609 (2012) 1-4.

[2] M. Ghidelli et al., Acta Mater. 131 (2017) 246-259.

[3] H. Idrissi, M. Ghidelli et al., Scientific Reports. 9, (2019) 1-11.