Abstract: Monolithic bulk metallic glasses (BMGs) are emerging as a novel and highly performant class of structural materials. Since their structure is atomically disordered, BMGs are in contrast to crystalline metals generally considered to be free of internal length scales. In this talk we will highlight different types of structural heterogeneities that may emerge due to the application of an external bias, such as stress. In particular, we will discuss time-scales and structural length-scales introduced by strain localization into shear bands. This includes the spatial structure of shear bands, how such nano-scale defects can result in long-range residual stresses, macro-scale cavitation and crack initiation, and how their residual stress signature can significantly affect the relaxation dynamics of the material. Subsequently, we transition to effects that arise during nominally elastic loading of a metallic glass. In this case, it is exemplified how simple elastic loading-protocols can alter the glassy structure via the introduction of nano-scale heterogeneities that we spatially resolve across the surface. The combined observations underline the importance of considering structural micro- and nano-scale length-scales in metallic glasses and how they may give rise to specific properties at the bulk scale.
Biography: Robert Maass received a triple diploma in Materials Science and Engineering from the Institut National Polytechnique de Lorraine (INPL-EEIGM, France), Luleå Technical University (Sweden) and Saarland University (Germany) in 2005. In 2009, he obtained his PhD from the Materials Science Department at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. During his doctoral work, Robert designed and built an in-situ micro-compression set-up that he used to study small-scale plasticity with time-resolved Laue diffraction at the Swiss Light Source. From 2009-2011 he worked as a postdoctoral researcher at the Swiss Federal Institute of Technology (ETH Zurich) on plasticity of metallic glasses. Subsequently, he joined the California Institute of Technology as an Alexander von Humboldt postdoctoral scholar to continue his research on plasticity of metals. After working as a specialist management consultant for metals at McKinsey & Co., he transferred to the University of Göttingen as a junior research group leader. He joined the faculty of the University of Illinois at Urbana-Champaign as Assistant Professor of Materials Science and Engineering in 2015. Hi research interests include microstructure-property relations, size effects, strain localization and defect structures of amorphous and crystalline metals, defect dynamics, mechanical properties, microplasticity, glass transition phenomena, and test system development. His honors include the Young Scientist Award by the German Materials Society, an Alexander von Humboldt Fellowship, the prestigious Emmy Noether award from the German Research Foundation, and the NSF Career Award.