Skip navigation
  2. Research
  3. Scientific Departments
  4. Materials Engineering
  5. Physical Analysis
Ein Mann steht an einem Tisch und schaut auf einen Bildschirm mit Grafiken.

The stress and functional behaviour of a component is significantly influenced by its chemical, physical and mechanical properties.

Knowledge of these properties is therefore a decisive prerequisite for understanding and optimizing heat-treated, machined or coated components made of high-strength structural materials. Consequently, the application and further development of physical investigation methods for the characterization of microstructure and residual stress states are the main focus of research within the department.

The measuring methods include, in particular, optical emission spectroscopy, X-ray fine structure measurement methods and micromagnetic methods. The possibilities of the large-scale research facilities (neutron and synchrotron radiation) are also used in the research activities of the department. The further development and application of in-situ X-ray diffraction methods are an important focus of the research activities of the Department of Physical Analysis.

 

[Translate to English:] Ein Mann mit einem Steuergerät in der Hand sitzt neben einem Roboterarm.
Physical analytics is strongly experimentally oriented

The department of physical analysis is strongly experimentally oriented and has 20 modern X-ray diffractometers for fine structure analysis which are optimized for different applications.

These allow, among other things, investigations with high spatial resolution by micro-beam optics, analyses of thin films under grazing incidence, measurements of large components and in production facilities by two mobile diffractometers as well as investigations with high time resolution for in-situ experiments. In addition, different methods with neutron and synchrotron radiation are applied and further developed in the research projects of the department.

The resulting material states, in particular the residual stresses, are analysed according to different manufacturing processes within the scope of various projects, partly with external cooperation partners, using the existing measuring methods. Within the priority program SPP2013, the mechanisms of residual stress generation during rotary swaging are currently being investigated in order to optimize the component properties in a targeted manner.

In-situ X-ray diffraction methods in the laboratory and at large-scale research facilities

The research and application of in-situ X-ray diffraction methods in the laboratory and at large-scale research facilities is a major focus of the research activities of the Department of Physical Analysis. Currently, various processes using laboratory X-ray sources are being fundamentally investigated, such as tempering effects in different steels or the formation of compound layers during nitriding. Thereby, fundamental aspects of material-physical mechanisms are investigated as well as new measuring methods for future sensors for process monitoring in industrial processes are developed.

In addition to the laboratory procedures, various experiments are carried out at synchrotron facilities. At the European Synchrotron Radiation Facility (ESRF), for example, the development of hydrostatic stresses in (residual) austenite during martensitic transformation during quenching could be followed over time and experimentally verified for the first time. The application of synchrotron radiation for in-process investigation of microstructure and stress development has been extended to other processes in recent years. Within the SFB TRR 136 "Process Signatures" a deep rolling process was simulated and analysed by different experimental approaches at the synchrotron (ESRF) and with neutron radiation at the Institut Laue-Langevin (ILL). The determined 2-dimensional stress and strain distributions could be used to develop process signatures for a process-independent prediction of the residual stress distributions during deep rolling.

 

Micromagnetic processes form a further research focus

Current research activities on the application of synchrotron radiation for in-process investigations are currently underway in the fields of additive manufacturing using laser powder cladding or in thermo-mechanical processes such as the continuous bainitization of forged steels within the framework of the DFG's Bragecrim Program at the German Electron Synchrotron in Hamburg (DESY). In addition, low-pressure carburizing is currently being investigated in-situ using a self-developed experimental setup with synchrotron radiation. The local microstructure and stress development is analyzed with spatial and time resolution.

Micro-magnetic processes form a further research focus with basic and application-oriented questions in order to enable reliable non-destructive analyses of material properties and boundary layer states. New approaches for depth-dependent measurement of residual stresses and hardness based on frequency-dependent signal acquisition and evaluation have already been investigated. The capabilities of a Barkhausen eddy current microscope for the fast acquisition of material and component properties on the microscale are currently being tested and further developed within the framework of SFB 1232 "Coloured states". Finally, new approaches for non-destructive testing of grinding burns in industrial production are being developed and directly implemented in practice within the framework of bilateral research projects with industry.

In addition, new strategies will be developed within the priority program SPP2086 to enable the application of this measurement technique in grinding plants.

Projects of the Physical Analysis

SafeAIR – Safe use of aluminum alloys for applications with liquid hydrogen in emission-free aircraft

Within the project, the resistance of promising additively manufactured aluminum alloys to hydrogen embrittlement is investigated by correlating mechanical behavior with the distribution of hydrogen atoms.

Within the Leibniz-IWT sub-project, and in collaboration with Helmholtz-Zentrum Hereon GmbH, the resistance of promising additively manufactured aluminum alloys to hydrogen embrittlement is investigated by correlating mechanical behavior with the distribution of hydrogen atoms.

The core objective of this individual project is to gain insights - within the multidisciplinary framework of the overall project - into the effects of hydrogen interactions with microstructural features and defects (dislocations, grain boundaries, and in particular precipitates) on the mechanical properties of aluminum alloys at cryogenic temperatures down to 20 K. Understanding these mechanisms is essential to prevent premature failure of critical components in future emission-free, hydrogen-powered aircraft and to ensure the required component safety. The project lays the foundations for the future development of safe LH2 systems in aviation by investigating material–hydrogen interactions using two different aluminum alloy systems (6xxx and 2xxx), produced both through conventional manufacturing routes and laser-based additive manufacturing, in various microstructural states.

Figure: Goals and approach

Collaboration: Leibniz-IWT WT-PA, WT-LW, Helmholtz-Zentrum hereon GmbH
Funding: LuFo VII-1 20E2406A
Duration: 01.03.2026 to 28.02.2029

This project is part of the research focus on "Hydrogen Technologies" at Leibniz-IWT Bremen.

Contact:
Dr. Lisa Belkacemi
Phone: +49 421 218 51372
E-Mail: belkacemi@iwt-bremen.de 

Non-destructive characterization of grinding-generated surface-layer modifications depending on the material condition using micromagnetic testing methods (FVA 723 III)

Aim of this project is the investigation of so far unknown effects on the micromagnetic detection of thermo-mechanical surface damages at ground gear flanks. Based on previous projects, investigations are carried out on profile and generating ground gears from case-hardening steel 20MnCr5 in different heat treatment conditions.

Building on already completed predecessor projects, investigations are being conducted on profile-ground and generating-ground gears made from case-hardening steel 20MnCr5 in various heat treatment conditions. Different surface layer states were generated through progressive loading of the grinding wheel (profile grinding) and variation of grinding parameters (generating grinding) and comprehensively characterized. In addition to Barkhausen noise measurements and nital etching, the X-ray diffraction half-width was determined on selected flanks of each gear. Representative flanks corresponding to the nital etching classes were characterized using metallographic sections, hardness measurements, and residual stress depth profiles.
 

 

Cooperation: Leibniz-IWT WT/FT
Funding: BMWi-AiF/IGF (FVA)

 

Contact:
Dr.-Ing. Jérémy Epp
Tel.: +49 421 218 51335 
E-Mail: epp@iwt-bremen.de 

Improvement of the Fatigue Strength of Riveted Lap Joints of Aerospace-Grade 7xxx Series Aluminum through Laser Shock Peening (LSP)

Cold working of rivet holes is frequently used for the repair and manufacturing of riveted lap joints in the aerospace industry.

However, this process generates zones with critical transitions from compressive to tensile residual stresses, which can serve as crack initiation points. Laser shock peening could be a promising alternative, as it offers more degrees of freedom in parameter selection. For this purpose, specimens with treated riveted joints were tested in tensile fatigue tests and subsequently analyzed non-destructively using synchrotron radiation. This demonstrated that the residual stress distribution differs significantly between the processes, but that these stresses remain stable under loading.
 

 

Cooperation: Airbus SE
Funding: BMWK/(Aviation Research Program VI-2)

 

Contact:
Dr.-Ing. Jérémy Epp
Tel.: +49 421 218 51335 
E-Mail: epp@iwt-bremen.de

Mechanism-based analysis and optimization of additive manufacturing process for hardenable tool steel by means of In situ X-ray diffraction experiments

Laser-directed energy deposition (L-DED) enables the production of complex, near-net-shape components with an optimized strength-to-weight ratio.

However, the process generates complex thermal cycles that lead to heterogeneous phase transformations and carbide precipitates. In this project, the mechanisms of microstructure development are investigated using in-situ X-ray diffraction, electron microscopy, and atomic probe tomography
(APT) on X40CrMoV5-1 steel. The combination of these advanced techniques enables the characterization of the various precipitates in the microstructure and the tracking of the formation of these precipitates throughout the entire process.

 

Funding: DAAD (PKZ91793403)

 

Contact:
Dr.-Ing. Jérémy Epp
Tel.: +49 421 218 51335 
E-Mail: epp@iwt-bremen.de 

Targeted Adjustment of Surface Layer Properties through In-Process Monitoring and Adaptive Process Control during Grinding

Following the grinding of hardened components, non-destructive testing for thermo-mechanical surface layer damage is typically performed. In-process testing methods, however, enable early response to negative changes and time savings by eliminating post-process testing.

In this project, the potential of soft sensor-based process control was demonstrated for preventing surface layer damage while maintaining high productivity. The soft sensor combines a thermal limit dependent on contact surface-related grinding power Pc'' and contact time ∆t, which enables the prevention of tempering zones, with in-process measured Barkhausen noise. When using CBN as the cutting material, a shift in the process limit determined for corundum was observed. The Barkhausen noise is influenced not only by the generated surface layer condition but also by the mechanical effect of the grinding wheel engagement, which primarily affects the signal in the saturation range. 

 

Cooperation: Leibniz-IWT WT/FT, Fraunhofer IWU Chemnitz 
Funding: DFG (SPP 2086)

 

Contact: 
Dr.-Ing. Jérémy Epp
Tel.: +49 421 218 51335 
E-Mail: epp@iwt-bremen.de 

Energy-Efficient Process Chain for New Bainitic Forging Steels through the Application of Thermo-Mechanical Processes

The project aims at developing a process route for forging-bainitic steels that can be led directly to final properties through continuous cooling from forging temperature.

Using in-situ experiments at the synchrotron, the transformation behavior was investigated under controlled conditions. To track the microstructure development during cooling under production-like conditions, an eddy current sensor was employed. The results show that both techniques are capable of providing accurate and partially comparable information about the occurring processes. The synchrotron experiments deliver diverse and precise data on microstructure development during the process, while the eddy current sensor offers an excellent opportunity for monitoring processes in industrial environments.
 

 

Cooperation: UFRGS, Brasilien
Funding: DFG (EP-128/6-2)

 

Contact:
Dr.-Ing. Jérémy Epp
Tel.: +49 421 218 51335 
E-Mail: epp@iwt-bremen.de 

Improved process understanding for case hardening with carburizing at low pressure based on in situ X-ray diffraction experiments

In the second phase of the project, the primary objective was to improve the developed experimental low-pressure carburizing (LPC) system and expand the understanding of the LPC process to different steel grades and include the tempering step in the experimental approach.

For this purpose, a completely new process chamber with active compensation of the sample position by means of laser triangulation was designed. Two measurement campaigns with in-situ experiments were successfully carried out on beamlines P21 and P07 at DESY in Hamburg. Various process parameters were investigated and, among other things, the influence of the boost duration on the formation and re-dissolution of carbides was analyzed. In addition, combined SAXS/WAXS measurements were carried out during annealing to track the formation of fine carbides with temperature and time resolution. 

 

Cooperation: KIT(-IAM-WK) 
Funding: DFG, EP-128/2-2

 

Contact:
Dr.-Ing. Jérémy Epp
Tel.: +49 421 218 51335 
E-Mail: epp@iwt-bremen.de  

Transregional CRC 136 “Process Signatures” – Transfer project T08: Material load oriented development of diamond tools for energy assisted cutting processes

In the transfer-project T08 of the CRC 136, the dependence of local material loads based on the tool geometry in energy-assisted diamond machining of silicon is determined.

Using the load-oriented process signatures approach applied to silicon for the first time, this project investigates the influence of targeted variation of mechanical and thermo-mechanical material loads for geometrically defined machining. With the aid of process simulation, the local loads are determined in the form of von Mises equivalent stress and absolute temperature. For validation, experimental analyses are conducted using vibration- and laser-assisted diamond turning processes. Tool development for these processes is of great economic interest to the industrial project partner. 

 

Cooperation: Gruppe Matzdorf GmbH 
Funding: DFG (SFB/TRR 136)

 

Contact: 
Dr.-Ing. Jérémy Epp
Tel.: +49 421 218 51335 
E-Mail: epp@iwt-bremen.de 

Partitioning-Controlled Heat Treatments for Targeted Adjustment of the Microstructure of Additively Manufactured Medium-Manganese Steels

Medium-manganese steels are at the forefront of third-generation high-strength steels due to their excellent mechanical properties. However, their high Mn content makes their production challenging.

This project aims to address this disadvantage by replacing conventional casting with additive manufacturing. Furthermore, the chemical heterogeneities that arise during production offer the possibility of reducing heat treatment times and adjusting the microstructure to achieve various mechanical properties. The image shows the different concepts for manufacturing and heat treatment of the components, utilizing the targeted use of the stacking fault energy of austenite, which are being pursued in the project. 

 

Funding: DFG

 

Contact: 
Dr.-Ing. Jérémy Epp
Tel.: +49 421 218 51335 
E-Mail: epp@iwt-bremen.de 

Targeted Adjustment of Surface Layer Properties through In-Process Monitoring and Adaptive Process Control during Grinding

Following the grinding of hardened components, non-destructive testing for thermo-mechanical surface layer damage is typically performed. In-process testing methods, however, enable early response to negative changes and time savings by eliminating post-process testing.

In this project, the potential of soft sensor-based process control was demonstrated for preventing surface layer damage while maintaining high productivity. The soft sensor combines a thermal limit dependent on contact surface-related grinding power Pc'' and contact time Δt, which enables the prevention of tempering zones, with in-process measured Barkhausen noise. When using CBN as the cutting material, a shift in the process limit determined for corundum was observed. The Barkhausen noise is influenced not only by the generated surface layer condition but also by the mechanical effect of the grinding wheel engagement, which primarily affects the signal in the saturation range.
 

Cooperation: Leibniz-IWT WT/FT, Fraunhofer IWU Chemnitz
Funding: DFG (SPP 2086)

Contact:
Dr.-Ing. Jérémy Epp 
Tel.: +49 421 218 51335 
E-Mail: epp@iwt-bremen.de