Fraunhofer Institute for Mechanics of Materials IWM
Fraunhofer Institute for Mechanics of Materials IWM

Identification of microstructure and property relationships

© Achim Käflein

Microstructure and 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 basis for the appropriate selection of materials or the optimization of materials and processes and the prediction of operational behavior.

What we offer

 

  • Analysis and evaluation of material microstructures due to production
  • Thermodynamic simulations to predict microstructure evolution
  • Elucidation of microstructure property relationships
  • Experimental determination, simulation and evaluation of residual stresses in components
  • Characterization of materials in contact with hydrogen and analysis of degradation mechanisms
 

Reasons for collaboration

  • »Anomalies« in production, test operations or in use (e.g. reductions in strength, crack formation, corrosion, surface defects)
  • Cases of damage
  • Compliance with specifications for raw materials and components and ensuring standards
  • Clarifying property changes in operation due to external factors (thermal, mechanical, chemical or coupled)
  • Questions of quality assurance when converting production processes
  • Assessing new raw materials regarding manufacturability, corrosion, long-term stability, strength and dimensional accuracy
  • Targeted generation of favorable properties in manufacturing
  • Need for input data for material simulations
  • Need for quantitative evaluations of raw materials (e.g. pore proportion, phase proportion, structure morphology, texture and raw material gradients)
  • Information on quantitative microstructure property relationships

 

Examples

  • Basis for decisions to use (replacement) materials
  • Approaches for increasing the performance of the materials used (e.g. by pre-treatment, heat treatment, coating, etc.)
  • Procedures to improve manufacturing steps (welding, surface treatment, heat treatment)
  • Suggestions for component optimization
  • Causes of damage and damage appraisals

 

It’s worth getting in touch with us

  • Our experienced staff provide the results of analysis and research efficiently, providing a reliable basis for our clients to take decisions
  • Our expertise in material microstructures, damage mechanisms in materials and components and residual stress allows us to consider problems holistically and deliver sustainable solutions
  • Our equipment allows us to investigate a wide variety of materials (ceramics, metals, layers, composites)
  • At the institute, we have a large pool of experts in a wide variety of specialist areas of material science. This leads to quick and efficient solutions for our clients
  • Our range of equipment and facilities allows us to carry out an efficient combination of measurement and analysis procedures based on the needs of the client
  • We have our own sample production facilities and can handle large components
 

Topics

 

© Fraunhofer IWM

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.

 

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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....

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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...

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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...

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Microstructure and property relationships within remelted surfaces


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...

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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.

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Damage analysis: metals

 

We answer questions that occur during the quality assurance phase of industrial production or due to failure during service. The scientific investigation of damage to and failures of metals and metallic components is well established within the Fraunhofer IWM. We will build an expert project team customized for your individual task, which will assess the situation and discuss the next steps with you to reach an effective solution.

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Microstructure, Residual Stresses publications

 

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

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