Physical Metallurgy
Head of the Group
Scientific Staff
Dr.-Ing. Daniel Schliephake (Head of the Materialography Lab)
Dr. rer. nat. Sandipan Sen
Raja Jothi Vikram, PhD (Fellow of the AvH Foundation)
M.Sc. Georg Winkens
M.Sc. Marcel Münch (LGF scholar)
M.Sc. Liu Yang (CSC scholar)
M.Sc. Gabriely Falcão
M.Eng. Jan Lars Riedel (joint member with Fatigue)
M.Sc. Sri Rathinamani Ramdoss
M.Sc. Amin Radi
We get support by our APT experts at KNMF:
M.Sc. Michael Eusterholz
Dr. Pamela M. Pineda Dominguez
Research Mission
The Physical Metallurgy group focuses on the development of metallic and intermetallic materials for extreme application conditions. The identification of suitable alloy compositions and tailoring of the microstructures is particular aim of our work.
The investigation and optimization of materials for engines operating at high temperatures is of central interest. Outstanding high temperature stability (mechanical and microstructural) in conjunction with reasonable toughness at room temperature as well as suitable oxidation resistance are the main objectives in this case. Furthermore, other extreme application conditions became relevant over time, for example deformation at cryogenic temperatures close to 0 K. The research activities all have the identification of fundamental mechanisms of the important phenomena, their relationship to materials properties and application to materials tailoring in common. In order to address these objectives, we routinely apply various materials synthesis techniques and scale-bridging characterization methods.
Synthesis of New Materials
The synthesis of new materials is based on the following methods that are available in house:
- cast metallurgy: arc melter and zone melting
- powder metallurgy: attritor grinding mill, planetary ball mill, hot uniaxial pressing
- heat treatments in various atmospheres
Characterization Methods
The characterization of mechanical and thermo-physical properties as well as microstructure of metallic and intermetallic materials is performed by means of:
- standard metallographic procedures
- mechanical testing under various loading conditions (tension, compression, cyclic, creep conditions, various atmospheres)
- thermal analysis: thermogravimetry (TGA) and differential scanning calorimetry (DSC)
- focused ion beam (FIB) for microscopic preparation
- analytical scanning electron microscopy: energy-dispersive X-ray spectroscopy (EDX) and electron backscatter diffraction (EBSD)
- X-ray diffraction (XRD)
- 3D atom probe tomography (APT)
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We congratulate Michael Eusterholz on the successful defense of his doctoral thesis. He was awarded the doctorate for his work on “Grenzflächenreaktionen in refraktären Metall-Keramik-Verbundwerkstoffen”. In the framework of the REFRABUND research unit (FOR3010) coordinated by TU Bergakademie Freiberg and funded by Deutsche Forschungsgemeinschaft (DFG), he contributed to the understanding of interface reactions in novel refractory composites made of ceramics and refractory metals.
Michael successfully revealed the reaction products in alumina-niobium and alumina-tantalum composites which are formed during the consolidation process. Furthermore, the nanoscale interface characteristics were identified by atom probe tomography, like interphases and segregation of impurities.
In collaboration with IAM-AWP at KIT, he was able to study the interface reactions under controlled conditions by synthesizing sputter deposited thin film model systems of refractory metals on sapphire substrates.
He provides evidence for (i) the forming oxidic phases in the different systems, (ii) segregating species and the amounts thereof, (iii) relevance of the external conditions and grain boundaries for phase formation as well as potential inconsistencies of thermodynamic data available so far.
You can find Michael’s contributions for example here:
https://doi.org/10.1002/adem.202200161
https://doi.org/10.1002/adem.202201441
We wish Michael all the best for his further career as the newly appointed atom probe tomography group leader at IAM-WK and look forward to discoveries in the field of nanoscale analyses in the future.
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We congratulate Georg Winkens on the successful defense of his doctoral thesis. He was awarded the doctorate for his work on “Solid solution strengthening in single-phase Mo alloys”. In the framework of the RTG2561 funded by DFG, he contributed to improved understanding of the strengthening contributions by different dislocation types in refractory solid solutions.
He successfully implemented the recently developed models by Maresca and Curtin for the use within our research groups and the alloy development of the RTG. By the experimental synthesis of binary model alloys, he was able to test these modern models against others as well as to investigate the potential change of strengthening contributions by screw and edge dislocations depending on alloy composition:
https://doi.org/10.1038/s43246-023-00353-8
Apart from the Mo based solid solutions subject to the RTG, he contributed to the application of the respective models to refractory high entropy alloys from the Ta-Mo-Ti-Cr-Al system. These recent results were published in the RTG special issue in Advanced Engineering Materials:
https://doi.org/10.1002/adem.202301797
You may also see Georg's open access publications of research data and program codes on KIT's repository to improve the accessibility of our research results:
https://doi.org/10.35097/1784
https://doi.org/10.35097/1866
https://doi.org/10.35097/1786
https://doi.org/10.5445/IR/1000157208
https://doi.org/10.5445/IR/1000157205
We wish Georg all the best for his further career and look forward to discoveries in the field of physical metallurgy in the future.
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The development and investigation of novel Mo-Si-Ti alloys has been one of our core competencies in recent years. These alloys are potential candidates for high temperature applications due to their balanced property portfolio of high temperature strength, oxidation resistance and lightweight potential. In our most recent study, we investigated the creep deformation mechanisms of a eutectic Mo-Si-Ti alloy together with our colleagues from Karlsruher Institut für Technologie (KIT), Laboratory for Electron Microscopy #LEM. In contrast to earlier investigations, we found that creep at 1200 °C can be divided into two regimes dominated by (i) diffusion creep below 100 MPa and (ii) dislocation climb controlled creep at and above 100 MPa. An attempt has been made to correlate the microstructural changes occurring at different microstructural length scales with the nature of the creep curve at 1200 °C and 100 MPa. The creep curve shows a transient strain hardening region followed by a distinct minimum and then acceleration of the creep rate. Microstructural investigations using TEM revealed the formation of a high proportion of disperse (Ti,Mo)5Si3 precipitates in the solid solution, which led to significant strengthening in the transient creep regime. By simultaneously decreasing the initially high dislocation density in the solid solution, the diffusion creep contribution becomes more dominant to the effective creep behavior. At a minimum, the load and strain are also carried by the silicide phase, which undergoes plastic deformation. Continuous coarsening of precipitates and loss of precipitation strengthening in the solid solution and dynamic recovery in the silicide phase led to creep acceleration at strains above the minimum creep rate.
to Advanced Engineering Materials![materials](/wk/img/phm002_rdax_1230x692s.jpg)
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Digitalization and Research Data Management
In order to address the increasing complexity of materials development and to increase the efficiency of materials characterization, our entire research activity is digitally documented in kadi4mat. We focus on documentation of complex synthesis from various raw materials and using several processing steps. Also materials characterization is recorded in detail. By contributions of Daniel Schliephake, Georg Winkens, Marcel Münch and Stephan Laube, we established the following framework:
- Research Structure
- Synthesis
- Processing
- Preparation
- Analysis
- Mechanical Testing
- Calibration
Furthermore, we make our research data publicly available along with our journal articles. In case, this did not take place, please do not hesitate to contact us for exchange of the research data.