Micro-/Nanomechanics of materials
High performance material systems are usually complex with respect to their elemental and phase composition and their response to plastic deformation is governed by local, intrinsic processes. However, to understand the complex interplay of the different microstructural features of such a material during deformation, it is critical that one properly understands the deformation behavior of these individual features. Consequently, a major goal of our research aims at revealing fundamental deformation mechanisms at the small scale to better understand the complex behavior of macroscopic materials that are used in electronic components, for structural applications or in energy-related material systems. We use different nanoindentation-based techniques to study localized plastic deformation mechanisms ex-situ and in-situ inside the SEM and TEM, at room and elevated temperatures and at different strain rates. Miniaturized experiments, such as uniaxial compression/tension, beam bending and fracture as well as high-cycle fatigue are frequently used in this regard.
Innovative manufacturing technologies such as additive manufacturing (AM) contribute to the ambition of energy transition and the digitilization of manufacturing industries. Within the AM group we are adopting multi-disciplinary approaches to qualify and to develop new metallic AM-alloys for energy applications, and to implement the AM technology in manufacturing advanced and sustainable metallic materials. The overarching aim is to advance the field-specific knowledge as well as to establish the essential methods and development steps in order to address the fundamental questions related to appropriateness/qualification of AM-alloys for energy transition. Our research is focusing on various themes including:
- Exploring the feedstock-process-microstructure-property correlations of AM-suited alloys
- Qualification of new alloys for metal AM
- Implementation of AM technology in materials processing for energy transition
- Development of advanced and sustainable metallic alloys for energy applications
- Hydrogen applications and hydrogen effects on AM-alloys behavior
Artificial architectured metamaterials
Materials that we are commonly used to are solid and more or less heavy. However, by now it is well-known that targeted material removal in a solid to create special architectures can lead to interesting material properties, such as high relative strengths, a negative refractive index or outstanding energy absorption. These architectured materials are referred to as metamaterials and have a great potential for exciting properties. Using a polymer-based 3D stereoprojection printer we explore how special material designs can lead to better light weight materials or functional materials that benefit from the increased surface area of the highly porous materials. Consequently, these light-weight, functional materials call for applications in the energy sector.
A simple relation holds true in many materials, i.e. the smaller the better. For example, reduced grain sizes of a material generally increase the materials strength. The same trend appears in laminated materials such as multilayer stacks. Reduction in the layer thickness generally increases the strength of the system. In addition, the reduction of grain size or layer thickness generally increases the internal interface content – grain boundaries and hetero interfaces - of such materials. Especially when the critical feature length drops into the nanometer length scale, massive interface fractions exist, which provide a huge playground for material property manipulations. We therefore explore these nanostructured materials from a (micro)structural point of view by advanced electron microscopy techniques, but additionally how modifications of interface properties can be influenced by mechanical stresses or plastic deformation.