Grain boundaries are one of the most important constituents of a polycrystalline material and play a crucial role in dictating the properties of a bulk material in service or under processing conditions. Bulk properties of a material like fatigue strength, corrosion, liquid metal embrittlement, and others strongly depend on grain boundary properties such as cohesive strength, energy, mobility, etc. These boundary properties in turn are governed by the structure and chemistry of a grain boundary. Furthermore, it has recently been realized that grain boundaries themselves can be described as interface-stabilized phases. We are just at the advent to utilize the phase character of grain boundaries as a material design element.
In the first part of this project, we are focusing on the atomic structure and phase transformation in special grain boundaries in aluminum by using dedicated transmission electron microscopy techniques in combination with the atomistic simulations. Epitaxial aluminum thin films are deposited on sapphire substrate by molecular beam epitaxy or other physical vapor deposition techniques to establish a template based methodology for obtaining specific grain boundary types. Electron backscatter diffraction measurements are employed to characterize the global grain boundary structure and types present in the films. Focused ion beam sample preparation allows then to extract specific grain boundaries for further atomic scale investigations of their structure, chemistry and transitions.
The second part of the project is focusing on in-situ TEM experiments to study the phase transformation behavior of the pre-characterized grain boundaries. The main objective is to develop unified correlations of the grain boundary structure, their transitions and properties.
Last, but not least, we will explore the influence of impurity elements on the structure and properties of grain boundaries and how they can be utilized to tailor the phase behavior of these interfaces.
International researcher team presents a novel microstructure design strategy for lean medium-manganese steels with optimized properties in the journal Science
Adding 30 to 50 at.% aluminum to iron results in single-phase alloys with an ordered bcc-based crystal structure, so-called B2-ordered FeAl. Within the extended composition range of this intermetallic phase, the mechanical behavior varies in a very particular way.
This project aims to correlate the localised electrical properties of ceramic materials and the defects present within their microstructure. A systematic approach has been developed to create crack-free deformation in oxides through nanoindentation, while the localised defects are probed in-situ SEM to study the electronic properties. A coupling…
By using the DAMASK simulation package we developed a new approach to predict the evolution of anisotropic yield functions by coupling large scale forming simulations directly with crystal plasticity-spectral based virtual experiments, realizing a multi-scale model for metal forming.
The aim of this project is to correlate the point defect structure of Fe1-xO to its mechanical, electrical and catalytic properties. Systematic stoichiometric variation of magnetron-sputtered Fe1-xO thin films are investigated regarding structural analysis by transition electron microscopy (TEM) and spectroscopy methods, which can reveal the defect…
In collaboration with Dr. Edgar Rauch, SIMAP laboratory, Grenoble, and Dr. Wolfgang Ludwig, MATEIS, INSA Lyon, we are developing a correlative scanning precession electron diffraction and atom probe tomography method to access the three-dimensional (3D) crystallographic character and compositional information of nanomaterials with unprecedented…
Conventional alloy development methodologies which specify a single base element and several alloying elements have been unable to introduce new alloys at an acceptable rate for the increasingly specialised application requirements of modern technologies. An alternative alloy development strategy searches the previously unexplored central regions…