Project leader:Daniel Șopu
Co-Proposer:Christoph Gammer
The FWF project entitled “Unraveling the atomic-scale deformation behavior of metallic glasses through combined modelling and experimental techniques” aims to develop new tools to better understand and control the atomic structure and the fundamental deformation mechanism of metallic glasses (MGs). The combination of multi-scale simulations and advanced experiments will provide a synergistic basis for realizing the design aim of the project to develop novel tailored MGs with enhanced mechanical properties.
Shear bands (SBs) are the plasticity carriers of metallic glasses (MGs) and the rapid runaway of a detrimental SB often leads to catastrophic failure of MGs under applied stress. The ability to control the plastic deformation of MGs is based on the ability to influence the percolation of shear transformation zones (STZs), which ultimately leads to the formation of SBs. Despite recent research progress, it remains a long-standing challenge to elucidate the atomic-scale mechanism of shear banding and its correlation with the structure of MGs, and ultimately to establish a universal structure-plasticity picture.
In this context, this project proposes to break the old vision of SB formation and thus to elucidate the atomic-scale deformation behavior of MGs through a synergetic combination of multiscale simulations and advanced experiments capable of reaching nm resolution.
In addition, the use of the local entropy-based structural descriptor combined with activation energy spectrum, Voronoi polyhedron descriptors and machine learning, notable progress could been made in predicting the deformation and relaxation mechanisms of MGs, ultimately aiming at the property-driven design of MGs.
To unravel the atomistic details of the mechanism of STZ self-assembly and SB nucleation and propagation in MGs, a combination of atomistic simulations and advanced scanning transmission electron microscopy (STEM) experiments will be used. The main aspects will rely on the innovative STZ-vortex model and new STEM techniques capable of analysing individual shear bands in MGs.
STZ-vortex mechanism, a novel approach - An STZ induces quadrupolar elastic displacements in their surrounding matrix, effectively behaving as Eshelby-like inclusions (see figure below, left hand side panel). Such a Eshelby-like quadrupole show directionality with tensile and compressive strain components perpendicular to each other (marked with white arrows). This antisymmetric strain field around the STZ generates a vortex-like motion of the neighboring atoms. The rotation field generated by the complex strain distribution around the STZ shows also a quadrupolar distribution between the four wings of the atomic strain (right hand side panel). The reiteration of the STZ-vortex unit controls the activation and percolation of STZs and thus the formation of shear bands in MGs.
Next, based on molecular dynamics (MD) and static simulations together with machine learning frameworks and other dedicated softwares for materials modeling, new tools will be developed to better predict, visualize and understand the fundamental deformation mechanisms of MGs from local elastic excitations to the macroscopic plasticity. The results will be correlated with experimental investigations performed using 4D-STEM. Along this line, many unsolved issues concerning two-unit STZ-vortex mechanism will be addressed.
Due to the achievable spatial resolution of <2 nm, it is possible to obtain maps using 4D-STEM and MD simulations at the same scale and directly compare the experimental strain map with the structural features observed in the MD simulation, which is key to this project. A possible quantitative comparison between experimental and simulation results may provide the necessary knowledge for the design of tailored modulated MG structures and guide the development of new strong and ductile materials.
The project is based on an intense co-operation between theoretical and experimental researchers at the Erich Schmid Institute of Materials Science (ESI), Austrian Academy of Science in Leoben and the group of Computational Materials Design at Materials Center Leoben (MCL). Additional support will be provided by external partners.
Dr. Daniel Șopu
daniel.sopu(at)oeaw.ac.at
Project duration
01.01.2025 – 31.12.2027
Cooperation partner
Dr. Oleg Peil, MCL Leoben
