Closed Projects in alphabetical order

The goal of this project is to optimize the orientation mapping technique using four-dimensional scanning transmission electron microscopy (4D STEM) in conjunction with precession electron diffraction (PED). The development of complementary metal oxide semiconductor (CMOS)-based cameras has revolutionized the capabilities in data acquisition due to their high sensitivity and fast read out speeds. While scanning an almost parallel, nanometer sized electron probe across the sample, it is now possible to acquire high quality diffraction patterns at each beam position. This produces a complex 4D dataset, where local crystal symmetries, lattice strain and crystal orientation are encoded in the 2D diffraction patterns obtained for each point of the 2D raster grid. The high image quality of the diffraction patterns significantly improves the reliability to determine lattice symmetries and orientations and with this greatly enhances orientation mapping. [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]

Carbon(C)-containing martensitic steels are ideal candidates for high-strength applications, e.g. in automotive and aerospace applications, due to their excellent mechanical properties and low cost. Carbon can even redistribute at room temperature leading to the formation of nanoscale carbides that can significantly influence the mechanical properties. [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]

In this project, we explore the hydrogen-storage capabilities of quaternary refractory high-entropy alloys (RHEAs) showing transformation-induced plasticity (TRIP) by electro-chemical charging. The initially body-centered cubic (BCC) alloy can be partially transformed into the hexagonal close-packed (HCP) phase upon room temperature straining, allowing to adjust the HCP fraction by the pre-straining conditions. After electro-chemical charging a high fraction of compositionally complex face-centered cubic (FCC) hydrides form in the HCP phase. We employ atomic resolution imaging, electron energy loss spectroscopy (EELS) and in situ heating in the transmission electron microscope (TEM) to determine the hydride formation sequence, their stability and dissolution mechanisms. [more]

In this project, we study the atomistic structure and phase transformations of tilt grain boundaries in Cu by using aberration-corrected scanning transmission electron microscope to build a relation to the transport properties of the grain boundaries via macroscopic tracer diffusion experiments. In the meantime, we address the impact of the grain boundary bicrystallography and solute segregation on both the grain boundary structure and diffusion properties. [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 explores the presence and consequences of grain boundary phase transitions (often termed “complexions” in literature) in pure and alloyed Cu and Al. If grain size gets smaller and smaller - like in nanocrystalline materials - the grain boundary (GB) volume can exceed several 10% of the total material volume and become a powerful lever to manipulate and set properties. The atomic coordination and chemistry of such GBs may undergo phase transitions, abrupt changes in structure and/or chemistry, which will impact the material behavior - like strength, thermal stability, electrical resistance – even for conventional materials. However, this interplay between GB phases and material properties is poorly understood. Experimentally, GBs are difficult to study - it needs atomic resolution and sensitivity with respect to chemistry to uncover their structure and possible complexions. In addition, it is unknown under which conditions phase transformations of GBs occur. A fundamental understanding requires atomistic modelling connected with smart experiments.
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Metallic glasses are continuously prone to structural changes due to their metastable character. These structural modifications, such as segregation or crystallization, can be used to produce nanocomposite or nanocrystalline functional materials or they can represent a deterioration of the material properties. In either case, a fundamental understanding of the process kinetics and chemical/structural evolution is essential. [more]

  Scanning transmission electron microscopy (STEM) has become an increasingly versatile and sophisticated instrument for studying materials at the atomic scale, due to advancements in in situ capabilities, novel imaging and spectroscopy modalities and ultrafast detectors. The large multidimensional datasets that are produced are enormously rich in quantitative information about the sample, but they call for new approaches in terms of data and metadata management. At present, the multitude of proprietary data formats developed by instrument manufacturers hinder easy access to the raw data. Each format also has their own metadata representation. In light of FAIR (Findable, Accessible, Interoperable, Reusable) principles, it is becoming increasingly important to standardize (meta)data representation. The goal of this project is to develop universal, instrument and experiment independent TEM data and metadata formats.  [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]

The goal of this project is to study the deformation mechanism, mechanical properties of silicon (Si) single crystal under nanotribological loading conditions by using ex situ scanning electron microscopy (SEM) and in situ transmission electron microscopy (TEM). The quantitative correlation between the mechanical properties linked with real time observations of deformation processes will provide a fundamental understanding of the tribological behavior of Si at the nanoscale. [more]

This project aims at getting a deeper understanding of  dendrite-like precipitates formed by a solid state decomposition of the high-temperature phase. To investigate this phenomena systematic variation of cooling rates and annealing times and temperatures for different alloy compositions are carried out.

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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]

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 objectives of this project is to understand the strengthening mechanisms of high entropy alloys (HEAs) from a dislocation plasticity point of view. The effects of microstructure and local composition, down to the atomic scale, on the plastic deformation are also investigated to establish a fundamental structure-property relationship of HEAs. [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 [1-8]. For this purpose, we isolate a single defined grain boundary in micron-sized sample. Subsequently, we measure and compare the uniaxial compression properties with respect to single crystalline samples, using in situ micromechanical techniques. Two specific boundaries are targeted in this project:
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Even though most structural materials are polycrystalline, the dislocation grain boundary interaction is not thoroughly understood. [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]

Smaller is stronger” is well known in micromechanics, but the properties far from the quasi-static regime and the nominal temperatures remain unexplored. This research will bridge this gap on how materials behave under the extreme conditions of strain rate and temperature, to enhance fundamental understanding of their deformation mechanisms. The mechanical behavior of metals with different crystal topologies, i.e. FCC, BCC and HCP and alloy systems, will be investigated in a statistically relevant manner using dewetted microparticles as the test-beds. [more]

Because of their excellent corrosion resistance, high wear resistance and comparable low density, Fe–Al-based alloys are an interesting alternative for replacing stainless steels and possibly even Ni-base superalloys. Recent progress in increasing strength at high temperatures has evoked interest by industries to evaluate possibilities to employ Fe–Al-based alloys for various applications. These activities have matured to a point that industrial processing of parts is now investigated in more detail by considering economic aspects. [more]

The goal of this project is to develop an environmental chamber for mechanical testing setups, which will enable mechanical metrology of different microarchitectures such as micropillars and microlattices, as a function of temperature, humidity and gaseous environment. [more]

The project in the scope of research activities of the Advanced Transmission Electron Microscopy group has two main objectives: (i) epitaxial thin film deposition and (ii) in-situ TEM tensile experiments. [more]

Within the EU project „ADVANCE - Sophisticated experiments and optimisation to advance an existing CALPHAD database for next generation TiAl alloys”, MPIE collaborated with Thermocalc-Software AB, Stockholm, Montanuniversität Leoben and Helmholtz-Zentrum Hereon, Geesthacht. At MPIE the focus lay on the production and heat treatments of model alloys and their analysis through metallography, X-ray diffraction, electron probe microanalysis and differential thermal analysis. Colleagues in Leoben performed transmission electron microscopy and at Helmholtz-Zentrum Hereon in situ synchrotron X-ray diffraction was carried out. All obtained data were optimised at the company Thermocalc and checked for consistency before they were implemented into the database. [more]

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 of multi-component phase space for alloys whose properties can be tuned with a greater degree of control than previously achievable. The targeted exploration of composition spaces containing five or more elements presents a significant challenge due to the vast number of possible alloy combinations. Novel approaches are required to efficiently map the boundaries of unique phase and morphology formation domains over large regions of multi-principle-element composition space. [more]

The next generation of Advanced Ultra Supercritical Coal-fired power plants (A-USC) aim at operating temperatures of approx. 700 °C and pressures of approx. 320 bars. Under these conditions, conventional ferritic steels are no longer usable. [more]

The formation of a face-centered cubic (FCC) titanium (Ti) phase is still one of the mysteries in this environmentally sensitive alloy family. We show in this project, how hydrides in Ti can be formed during sample preparation, reveal the underlying mechanisms and establish pathways to suppress or even eliminate the unexpected hydride formation. Hydride formation is mostly associated with the high diffusion rate and low solubility of hydrogen within the HCP matrix. Through plasmon loss electron energy loss spectroscopy (EELS) and atomic resolution imaging in combination with atom probe tomography (APT) we establish that predominantly TiH_X (x~50 at.%) forms in commercially pure Ti and show that focused ion beam preparation at cryogenic temperatures can suppress hydride formation. [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]

The current understanding of wear of metals shows that the crack initiation mechanism is related to surface fatigue which occurs as the metal experiences repeated loading cycles. However, it was revealed that cracks can form even in single stroke tracks and that the crystal orientation determines the crack patterns. [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]

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 segregation of impurities to grain boundaries (GBs) has a significant influence on the cohesive properties, atomic arrangements and properties of such interfaces. The segregation strongly depends on the structural units of the GB as well as on the impurity atom itself. Aberration–corrected (S)TEM techniques in combination with atomistic simulations are applied to unravel the connection of grain boundary structure and chemistry at atomic resolution. [more]

Fusion is one of the most promising safe, emissionless and limitless sources of energy. The extreme conditions in a fusion reactor, require the development of novel materials to withstand high temperature ion irradiation and at the same time provide sufficient mechanical stability. [more]

A structural hierarchy due to chemical ordering, dimensionality and spatial arrangement of the constituent phases was obtained in a precipitation strengthened ferritic alloy. Nearest-neighbor ordered B2-NiAl precipitates were coherently embedded in the disordered bcc-Fe matrix. Throughout the solid-state aging heat treatment a coherent substructure of the next-nearest-neighbor ordered L2₁-Ni₂TiAl phase formed only within the primary B2-NiAl precipitates. [more]

The goal of this project is the investigation of interplay between the atomic-scale chemistry and the strain rate in affecting the deformation response of Zr-based BMGs. Of special interest are the shear transformation zone nucleation in the elastic regime and the shear band propagation in the plastic regime of BMGs. [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]

Hydrogen embrittlement (HE) of steel is a great challenge in engineering applications. However, the HE mechanisms are not fully understood. Conventional studies of HE are mostly based on post mortem observations of the microstructure evolution and those results can be misleading due to intermediate H diffusion. Therefore, experiments with a simplified stress states and in-situ mechanical loading are required to better understand HE. [more]

Hydrogen is a clean energy source as its combustion yields  only water and heat. However, as hydrogen prefers to accumulate in the concentrated stress region of metallic materials, a few ppm Hydrogen can already cause the unexpected sudden brittle failure, the so-called “hydrogen embrittlement”. The difficulties in directly tracking hydrogen limits the analysis to post-mortem probes ignoring hydrogen migration before and during testing, leading to debates about the governing mechanisms. Therefore, a more comprehensive understanding of hydrogen-metal interaction with microstructural features is necessary to prevent hydrogen-introduced damage and further contribute insights into developing hydrogen-resistant materials. [more]

The mostly unknown influence of Ag as solute segregate at copper grain boundaries on mechanical properties is studied by aberration-corrected STEM from an atomistic structural point of view and by in-situ TEM nanocompression experiments to visualize dislocation-grain boundary interactions. [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]

By combining advanced characterization and mechanical testing of microsized, single-phase intermetallic samples through in situ micromechanical experiments inside an SEM or TEM, the mechanical response can be measured while simultaneously observing the microstructural changes. From these experiments, it is expected to get a much deeper insight in the complicated deformation mechanism of intermetallic phases, which is very much different from that in pure metals. [more]

Here, we study strain und temperature induced phase transformation pathways in high entropy alloys (HEA) by aberration-corrected and in situ scanning transmission electron microscopy (S/TEM). The bidirectional phase transformation (face-centered cubic (FCC) → hexagonal close packed (HCP) → FCC) in a transformation-induced plasticity (TRIP)-assisted high-entropy alloy (HEA) is explored by a combination of atomic resolution imaging and in situ tensile straining. In a similar HEA, the temperature induced transformation from HCP to nanotwinned FCC and associated formation of nanocarbides at the nanotwin boundaries are investigated at atomic resolution by in situ heating. We aim to reveal the atomic scale origins of phase transformations to guide the design of advanced HEAs with a unique combination of strength, ductility and thermal stability. [more]

The objective of this large-scale collaborative research project is the development of intermetallic materials for application in large diesel ship engines. [more]

Peritectoid transformations are a comparatively rare type of invariant reaction where in the solid state of a material, a phase A decomposes on heating into a mixture of two other phases B and C [more]

Fe-Al alloys in the composition range up to 50 at.% Al with disordered A2 or ordered B2 or D0₃ crystal structure are intensively discussed in the literature as potential materials for structural applications at elevated and high temperatures especially due to their excellent corrosion resistance and low density compared to conventional steels. [more]

Today there is an increasing economic and ecological need for the development of new structural materials for applications at high temperatures. Possible candidates for such materials are metallic alloys containing high-melting intermetallic phases which retain high strengths at high temperatures. [more]

This project focused on the interface between dielectric materials and different metals. [more]

Ferritic superalloys are an attractive alternative to Cr-rich martensitic steels or Ni-based superalloys for high-temperature applications in thermal power plants due to their excellent mechanical properties, oxidation resistance and low density. Strengthening of the Fe-matrix by coherent B2-NiAl precipitates leads to an increase in creep resistance up to temperatures of 700 ºC and stresses of 100 MPa. [more]

The fracture toughness of Au_XSn_Y intermetallic compounds is measured as it is crucial for the reliability of electronic chips in industrial applications. [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]

The development of nanostructured metals and alloys with superior mechanical properties is of paramount importance for both, a fundamental scientific understanding of the structure property relationship of materials and future technological applications in modern micro- and nanotechnologies. [more]

Nanotribology mechanisms, i.e. friction and wear, gain greater importance as the size of technological devices shrinks to the micro- and nanoscale. This project focuses on tribological experiments at the micro- and nanoscale of iron alloy microstructures. [more]

Deviations from the ideal, stoichiometric composition of tcp (tetrahedrally close-packed) intermetallic phases as, e.g., Laves phases can be partially compensated by point defects like antisite atoms or vacancies, but also planar defects may offer an opportunity to accommodate excess atoms. [more]

Understanding the mechanical behavior and microstructure correlation of copper-chromium films is of paramount importance both from scientific and technological perspectives. [more]

This project was a joint collaboration between Tata Steel and the SN department with the aim of performing quantitative characterisation of multi-phase precipitates in grain oriented electrical steel (GOES) using high-resolution chemical composition mapping by means of Energy-Filtering Transmission Electron Microscopy (EF-TEM). [more]

Substitution of so-called strategic elements such as Co, Nb, Ta or W becomes increasingly important to avoid political and economic dependencies. A possible replacement for alloys containing large amounts of strategic elements such as Cr-Ni steels or Ni- and Co-based alloys are Fe-Al-based alloys. Parts constructed out of Fe-Al-based alloys can be operated under high loads at high temperatures in aggressive environments. [more]

The Ni- and Co-based γ/γ’ superalloys are famous for their excellent high-temperature mechanical properties that result from their fine-scaled coherent microstructure of L1₂-ordered precipitates (γ’ phase) in an fcc solid solution matrix (γ phase). The only binary Co-based system showing this special type of microstructure is the Co-Ti system, where the Co solid solution is the γ phase and TiCo₃ the L1₂-ordered γ’ phase. [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]

Grain boundaries (GB) are typically considered as 2-dimentional interfaces separating two differently oriented crystals inside a polycrystalline material. Understanding their structure and composition down to nano-scale regime is fundamental to explain their macroscopic properties. Discerning the contribution of GBs towards strength, corrosion resistance and high temperature properties is necessary to boost our efforts of making metals lighter, stronger and hence greener. Titanium (Ti) is one of the most attractive materials for aerospace and bio-medical industries where high strength to weight ratio and chemical inertness play a vital role. Ti also makes an interesting case owing to its allotropic transition from the hexagonal close packed (HCP) to the body-centred cubic (BCC) phase at 882 ºC. Despite of its widespread industrial use very little is known about its GB structure and their possible transitions. Hence, the aim of this project is to look deeply into the atomic structure of GBs in Ti and to resolve the impact of alloying additions on their structure through advanced transmission electron microscopy (TEM) techniques. A challenging, yet intriguing task is to obtain defined tilt GBs in Ti and we found that epitaxial thin films are excellent candidates for generating thin films containing pure tilt boundaries in them. [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]

Grain boundaries are one of the most prominent defects in engineering materials separating different crystallites, which determine their strength, corrosion resistance and failure. Typically, these interfaces are regarded as quasi two-dimensional defects and controlling their properties remains one of the most challenging tasks in materials engineering. However, although more than 50 years ago the concept that grain boundaries can undergo phase transformations was established by thermodynamic concepts, they have not been considered, since they could not be observed. Through a combination of atomic resolution scanning transmission electron microscopy (STEM) and advanced atomistic modelling we establish pathways to directly observe and explore grain boundary transitions in metallic alloys. [more]

The segregation of impurity elements to grain boundaries largely affects interfacial properties and is a key parameter in understanding grain boundary (GB) embrittlement. Furthermore, segregation mechanisms strongly depend on the underlying atomic structure of GBs and the type of alloying element. Here, we utilize aberration-corrected scanning transmission electron microscopy (STEM) in combination with atom probe tomography (APT) and first-principles density functional theory (DFT) calculations to explore the atomistic and thermodynamic origins of co-segregation of interstitial boron and carbon as well as substitutional aluminum in bcc-Fe. The impact on zinc segregation and its possible effect on liquid metal embrittlement are currently investigated by atomic scale microscopy. [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 research focused on the mechanical behaviour of nanostructured materials and the deformation mechanisms underlying the outstanding mechanical properties with respect to their microstructure. [more]

One of the still mysterious effects in high entropy alloys (HEAs) is how atoms in highly supersaturated solid solutions locally arrange in the given crystal lattice. Recent investigations indicate that chemical short range order (SRO) and local compositional fluctuations are characteristic for HEAs, which can significantly affect the mechanical properties. In this project, the characteristics of short range order and local compositional fluctuations in refractory high entropy alloys are revealed at atomic resolution and are correlated to micro- and macroscopic mechanical properties. [more]

Wear and abrasion occur during sliding friction of metallic body and counter-body. Surface roughness is purposefully introduced into the metal to reduce wear and abrasion and to increase the lubricant flow. [more]

Nb-based intermetallic alloys consisting of Nb solid solution and high-melting, strengthening intermetallic phases are of considerable interest for structural applications at very high temperatures. [more]

Copper structures in microelectronic devices have to fulfill two important requirements, a high electrical and thermal conductivity. However, the lifetime is determined by the static and dynamic mechanical properties of the Cu structures. [more]

Statistical significance in materials science is a challenge that has been trying to overcome by miniaturization. However, this process is still limited to 4-5 tests per parameter variance, i.e. Size, orientation, grain size, composition, etc. as the process of fabricating pillars and testing has to be done one by one. With this project, we aim to fabricate arrays of well-defined and located particles that can be tested in an automated manner. With a statistically significant amount of samples tested per parameter variance, we expect to apply more complex statistical models and implement machine learning techniques to analyze this complex problem. [more]

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. [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]

Global energy consumption to overcome friction is significant and minimization of this  consumption will allow monetary savings and a greener environment. [more]

Extensive research has been focusing on face-centered cubic (FCC) high entropy alloys (HEAs) to establish the underlying mechanisms for their outstanding mechanical properties, for instance, an impressive combination of strength and ductility at cryogenic temperatures. One possibility suggested is that these new types of alloys show stronger Hall-Petch strengthening, where the grain size has a stronger impact on their yield strength. The origin of this grain boundary strengthening in HEAs seems to be originating from the different atomic radii of the supersaturated solid solution inducing high lattice strains. Hence, resolving the impact of compositional complexity on the atomic structure of grain boundaries in HEAs is crucial to understand their role in the strengthening mechanisms. [more]

TiAl-based alloys currently mature into application. Sufficient strength at high temperatures and ductility at ambient temperatures are crucial issues for these novel light-weight materials. By generation of two-phase lamellar TiAl + Ti₃Al microstructures, these issues can be successfully solved. Because oxidation resistance at high temperatures is still a problem which could be improved by increasing the Al content, Al-rich TiAl alloys have recently come into focus. [more]

The local accumulation of fatigue damage is not understood for 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.) nondestructively with high spatial resolution (<1μm). [more]

The mechanical properties of bulk CrFeCoNi compositionally complex alloys (CCA) or high entropy alloys (HEA) are widely studied in literature [1]. Notably, these alloys show mechanical properties similar to the well studied quinary CrMnFeCoNi [2] . Nevertheless, little is known about the deformation mechanisms and the thermal behavior of these alloys in thin film form. The current project aims to investigate these properties within the framework of a joint  DFG/ANR project involving the collaboration of Prof. Alfred Ludwig (Ruhr-Universität Bochum, Germany), Dr. Dominique Chatain (CINaM, Marseille, France) and Dr. Natalie Bozzolo (CEMEF, Sophia Antipolis, France). [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 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]

To make electricity production more sustainable requires the development of novel high-temperature-stable materials capable of operating in harsh environments and not requiring large amounts of expensive and rare elements.  Conventional alloy development methodologies which specify one or two base elements and several alloying additions have been unable to introduce new alloys with the required combination of properties for these high temperature applications.  An alternative alloy development strategy searches the relatively unexplored central regions of multicomponent phase space for multi-principle-element alloys which can be optimised with a greater degree of control than possible using conventional alloying techniques. [more]

The aim of this project is to develop novel nanostructured Fe-Co-Ti-X (X = Si, Ge, Sn) compositionally complex alloys (CCAs) with adjustable magnetic properties by tailoring microstructure and phase constituents through compositional and process tuning. The key aspect of this work is to build a fundamental understanding of the correlation between microstructure and magnetic properties by length scale bridging characterization and property determination. The ultimate goal is to establish guidelines for designing alloys with high magnetization saturation (Ms) and low coercivity (Hc), to optimize the magnetic properties of CCAs for high frequency magnetic field applications. [more]

In conventional metallic materials, the increase of strength by dislocation hardening generally sacrifices ductility. In recent years, a novel alloy design concept has drawn great attention, where multi-principal elements are mixed at equimolar or near equimolar concentrations to form highly concentrated solid solutions, termed high-entropy alloys (HEAs). To promote the wide use of HEAs as structural materials, it is highly desirable to improve the strength of HEAs while maintaining good ductility. In this project, we demonstrate an approach to improve the strength and ductility simultaneously by tuning the stacking fault energy and deformation mechanism in single-phase face-center cubic (FCC) high-entropy alloys (HEA) as shown in Fig. 1. [more]