Identification of interrelated microstructural properties

Microstructure, Residual Stresses

We investigate the effect of manufacturing processes and operational loads on the microstructure and the internal stress in materials and components. A particular focus lies on the identification of the combinatory degradation mechanisms of high temperature corrosion, stress corrosion cracking and hydrogen embrittlement. This is done using experimental methods, such as permeation tests with superimposed mechanical loads, and numerical methods, such as the simulation of microstructure and internal stress formation. This lays the groundwork for the correct selection of materials or the optimization of materials and processes and the prediction of operational behavior.

 

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Analysis and assessment of material microstructures in relation to the manufacturing process and operating conditions

Simulation, experimental identification and assessment of residual stresses

Investigations of material degradation due to corrosion, stress corrosion cracking, high temperature corrosion and hydrogen embrittlement

Thermodynamic simulation of microstructural formation

Identification of interrelated microstructural properties

Damage analysis, identification of technical liability, surveys carried out through publically appointed and impartial experts

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Microstructure, Assessment
 

Microstructures are responsible for the properties of raw materials and therefore for the properties of the resulting components which are produced. Microstructures are adjusted using different manufacturing steps. In use, they can change both positively and negatively. We uncover the relationships between the raw materials’ properties and those of the microstructure and use this information for optimized raw material properties and for the optimized use of raw materials - for example with regard to mechanical properties, long-term behavior, life expectancy, abrasive properties, corrosion properties, etc.). By using computer simulations, we can predict microstructures and assess them with regard to the reliability, safety and expected lifetime of components. Building on this, we develop concepts to design components and optimize manufacturing.

 

 

Residual stress analyses


Our aim is to create residual stress optimized components for our clients.
To do so, we determine manufacturing and use-caused residual stresses, assess them with regard to the reliability, safety and lifetime of parts and develop recommendations and concepts for component design, raw material use and manufacturing processing.
In order to prepare requirements to use components safely and reliably, we investigate and analyze residual stresses in connection with the underlying raw material microstructure, environmentally-caused degradation....

 

Hydrogen embrittlement in metals


Atomic hydrogen is capable of significantly reducing the ductility of metals. This can cause components to fail unexpectedly. The potential risk is generally related to the diffusible portion of the hydrogen. In order to predict the effects of hydrogen on material and component behavior via numerical simulations, we determine the dependence of the hydrogen diffusion constants on mechanical stress and temperature. The effects of hydrogen on the mechanical parameters of a metal are...

 

Simulation of heat treatment processes


The heat treatment of metals is an important means of creating a favorable microstructure and residual stress within a component. A movable inductor is often used to heat up the components. The experimental optimization of the treatment parameters is time-consuming and costly, particularly for larger components such as wind turbine bearings. Thanks to our effective mapping techniques and an enhanced simulation environment, we are able to...

 

Relationship between microstructure and properties in re-melted surface


In many cases, the surface of a component is critical to operational behavior and can be modified in various ways. A new technique, laser re-melting of surface layers, finely polishes or adds structure to a surface. The mechanical properties in the surface layers are modified by adjusting the laser parameters. The effect of process parameters on residual stresses, hardness and carbon content was investigated...

 

Characterization and simulation of precipitation development in copper alloys


Precipitation particle size and distribution has a decisive influence on the subsequent mechanical properties of high-strength and highly conductive precipitation hardened copper alloys. The precipitation particle size for a specific Cu-Ni-Si alloy was investigated for various rolling and annealing processes. The data is entered into a thermodynamic-kinetic model that is capable of calculating the development of particle size in...

 

Solarthermal Power Plants: Degradation of Materials in Molten Salts
 

The long-term use of renewable, fluctuating energy sources requires the development of assessment and qualification concepts for materials in the high-temperature reservoirs of solar power plants based on molten salt (TES - Thermal Energy Storage, CSP - Concentrated Solar Power Plants). Molten salt is used in many branches of industry, for example as baths made of molten chloride-salt mixtures for surface alloys or as fluoride salts to clean metal surfaces. In the meantime, molten salt from nitrates and nitrites have become more important as they are attractive heat conductivity and storage media for applications in energy generation.

 

Marginalized Layer Strength Improvement in Brittle Materials through Shot Peening


Shot peening is a widely used surface treatment to improve the static and cyclical strength of metal components. It is utilized in the mechanical stabilization of edge layers and for incorporation of more advantageous residual stresses. Shot peening is generally viewed as detrimental regarding brittle materials and is therefore not utilized. Experience has shown that in room temperature, brittle materials such as ceramic break as opposed to deforming. Experiments on brittle ceramic materials carried out at the Fraunhofer IWM have shown that under precise boundary conditions shot peening can yield high compressive residual stress to over 2 GPa. This allows for drastic...

 

Publications regarding Microstructure, Residual Stresses


Contributions to newspapers, books and conferences as well as dissertations and project reports...

Training

Here you can enroll for an apprenticeship as a materials tester, with a focus on metal technology. These specialists investigate materials, particularly metals, to determine their properties or any damage incurred, and monitor manufacturing processes.

Once qualified, materials testers can work in material development, manufacturing and processing companies and institutes. These include material testing authorities, testing laboratories, vehicle manufacturers and mechanical engineering companies and the electrical and electronics industry. Materials testers often work in laboratories or specially equipped testing laboratories or in factory workshops.

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