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Research Projects

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 X-ray absorption near edge structure spectroscopy (XANES), which can reveal the defect point defect structure caused by chemical variation. Following this, the defect structure can be correlated to mechanical properties such as fracture toughness, electrical resistivity, and the catalytic properties for possible future water-splitting applications. more
This project (B06) is part of the SFB 1394 collaborative research centre (CRC), focused on structural and atomic complexity, defect phases and how they are related to material properties. The project started in January 2020 and has three important work packages: (i) fracture analysis of intermetallic phases, (ii) the relationship of fracture to temperature (BDTT) and composition, and (iii) interfacial shear strength analysis of Mg-Intermetallic thin films. more
This project with the acronym GB-CORRELATE is supported by an Advanced Grant for Gerhard Dehm by the European Research Council (ERC) and started in August 2018.
The project GB-CORRELATE targets on (i) predicting and resolving GB phase transitions, (ii) establishing guidelines for GB phase transitions and GB phase diagrams, (iii) correlating GB phase transitions with property changes, (iv) providing compositional-structural design criteria for GB engineering, (v) which will be tested by demonstrators with tailored GB strength and GB mobility. GB-CORRELATE focusses on Cu and Al alloys in form of thin films as this allows to implement a hierarchical strategy expanding from individual special GB to GB networks and a transfer of the GB concepts to thin film applications. more
In this project, we aim to synthetise novel ZrCu thin film metallic glasses (TFMGs) with controlled thickness, composition and microstructure, while investigating the relationship with the mechanical behaviour focusing on the nanometre scale deformation mechanisms. Moreover, we aim to study the mechanical properties of film with complex architectures such as multilayers and amorphous-nanocrystalline composites. more
The thorough, mechanism-based, quantitative understanding of dislocation-grain boundary interactions is a central aim of the Nano- and Micromechanics group of the MPIE. For this purpose, we isolate a defined grain boundary in a micron-sized sample. Subsequently, we measure and compare the mechanical properties with respect to single crystalline samples. [1-8] more
This project deals with the phase quantification by nanoindentation and electron back scattered diffraction (EBSD), as well as a detailed analysis of the micromechanical compression behaviour, to understand deformation processes within an industrial produced complex bainitic microstructure. more
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 of dielectric spectroscopy is made with in-situ micro/nano-mechanical testing. The correlation between defects and electrical properties provides information about the local deformation-conductivity phenomena, improving electrical properties of material, and may enable predicting failure of materials. more
The dislocation – grain boundary interactions are shown to depend strongly on the type of grain boundaries, for example in micropillar compression tests on bicrystalline copper [1]. The coherent Σ3/{111} twin is shown to be a weak obstacle for dislocation motion where perfect slip transfer can take place across the grain boundary [2]. However, a large number of CTBs in nanotwinned metals lead to increase in yield strength [3]. Within this project we aim for extending the work on micropillar compression of bicrystals with a single CTB to those with multiple CTBs to investigate the critical role of microstructure constraints on slip transfer. more
The TRR 188 aims for a thorough understanding and quantitative control of damage in advanced materials. As a subpart of TRR188, this project aims at microscopically studying the initiation of damage on dual phase steel DP800. more
Nano- and Micromechanical experiments are nowadays widely explored to investigate site specific mechanical properties of materials and material systems which were not previously accessible in bulk dimensions [1]. Currently, the testing protocols for materials at non-ambient conditions, like high temperature or chemical non-inert atmospheres, are developed worldwide for micro/nanoscale testing (e.g. [2-4]). more
The local accumulation of fatigue damage is not understood for micron sized materials possessing grain and phase boundaries. This is primarily due to the lack of a characterization technique measuring the decisive material parameters (e.g. local strains, dislocation densities, grain boundary character, etc.) non-destructively with high spatial resolution (<1μm). more
Probing material properties at the micron scale requires dedicated machines and setups for sample manufacture, sample testing, and in-situ as well as post mortem defect analysis. Within the past years capabilities to produce and deform micron and submicron sized samples has been developed in the department for Structure and Nano-/ Micromechanics: more

Closed Projects

Copper is widely used in in micro- and nanoelectronics devices as interconnects and conductive layers due to good electric and mechanical properties. But especially the mechanical properties degrade significantly at elevated temperatures during operating conditions due to segregation of contamination elements to the grain boundaries where they cause grain boundary embrittlement and promote mechanical failure, limiting the lifetime of devices. more
The elasto-plastic fracture mechanics is well established at the micron scale. However, can test protocols be easily downscaled to the micrometer length scale? more
Current engineering materials are designed to exhibit superior mechanical properties by carefully balancing their chemical composition and microstructure. However, once the material is produced, the material properties and behavior tend to remain same under the certain boundary conditions. more
A novel design with independent tip and sample heating is developed to characterize materials at high temperatures. This design is realized by modifying a displacement controlled room temperature micro straining rig with addition of two miniature hot stages. more
A novel design with independent tip and sample heating is developed to characterize materials at high temperatures. This design is realized by modifying a displacement controlled room temperature micro straining rig with addition of two miniature hot stages. more
The fracture toughness of AuXSnY intermetallic compounds is measured as it is crucial for the reliability of electronic chips in industrial applications. more
While several methods are well-suited for studying dislocation transmission through grain boundaries, a quantitative approach understanding dislocation source activation in grain boundaries is currently lacking. more
Focus: Microcantilever fracture tests were carried out on various metallic glass thin films systems to evaluate their fracture strength and fracture toughness as a function of Poisson’s ratio. more
Even though most structural materials are polycrystalline, the dislocation grain boundary interaction is not thoroughly understood. more
The focus lies on the analysis of the mechanical behavior and their underlying deformation mechanisms in new ductile solid solution Mg alloys by performing micromechanical experiments with electron microscopy analyses. more
Experimental studies of the interfacial adhesion and interfacial fracture strength (energy release rate) are crucial to pave the way for mechanically and thermo-mechanically robust and reliable electronic devices. Our research mission is to examine the adhesion and fracture strength of interfaces between dissimilar materials. more
The mechanical response of miniaturized material systems strongly depends on the sample size. Macroscopically well documented material properties like the yield stress or the hardening rate are changing when the smallest sample dimension reaches the micrometer range. more
Understanding the mechanical behavior and microstructure correlation of copper-chromium films is of paramount importance both from scientific and technological perspectives. more
The research focused on the mechanical behaviour of nanostructured materials and the deformation mechanisms underlying the outstanding mechanical properties with respect to their microstructure. more
Focus: The research focused on testing the reliability of various novel fracture toughness test geometries at the small length scales using in-situ fracture tests in the SEM. more
Focus: Role of the interface in the deformation and fracture behavior of nanolaminate metallic systems have been studied in-situ in the SEM. more
Driven by increasing reliability requirements in automotive microelectronics and severe restrictions on lead-containing solders, recent research is focused on the examination of failure mechanisms in lead-free solder joints. more
The production of reliable flexible electronic devices are believed to be a future key-technology. The material systems thereby suffer from various loading conditions (e.g. temperature variation, monotone and cyclic strains,…). The pronounced differences in mechanical behavior between metal and polymer makes film/substrate systems prone to failure. more
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