Source: Dissertation Abstracts International, Volume: 77-12(E), Section: B.

Adviser: Jan Schroers.

Metallic glasses (MGs) have advanced into a new era of structural materials due to their superior mechanical properties such as high elasticity and high strength associated with the isotropic amorphous structure. Unique among metals, the existence of a supercooled liquid regime in MGs allows thermoplastic forming (TPF) of MGs like plastics. Toward applications, microstructure-property-processing relationships are generally important but challenging to determine since microstructural features are mutually interdependent. In order to study this challenge, we introduce a novel "artificial microstructures" approach, which comprises of silicon photolithography and TPF of MGs. This approach allows us to approximate a vast range of MG microstructural architectures and internal microstructuers over a wide range of length scales. We can independently vary and manipulate microstructural features with a high precision of ~ 1 microm, and thereby systematically decode the microstructure-property-processing relationships in MGs.

Through this approach, the relationships between MGs' microstructural features and mechanical properties such as flaw tolerance and fracture toughness have been examined. Specifically, two different levels of microstructures are considered. One is MG microstructural architectures with a variety of topologies including periodic, stochastic, and biomimetic structures. The correlation between different microstructural topologies and the mechanical behavior is revealed. Another aspect of microstructure is MGs' atomic microstructure. A wide range of different internal microstructures are systematically investigated by different processing procedures through the artificial microstructures approach to decode the atomic microstructure-property-processing relationships in a wide range of MGs. Many specific challenges in understanding the mechanical behavior of MGs are concerned, such as the origins of the significant variability in MGs' toughness evaluation, the flaw tolerance behavior of MGs, and the mechanistic origins that govern the toughness of different MG alloys. In general, the high precision, versatility, and predictability of the introduced artificial microstructures approach demonstrate it as a powerful toolbox to understand the microstructure-propertyprocessing relationships in MGs and design high performance MGs and architectures.