5 Werkstofftechnik
Filtern
Dokumenttyp
- Zeitschriftenartikel (27)
- Forschungsdatensatz (12)
- Beitrag zu einem Tagungsband (11)
- Vortrag (7)
- Buchkapitel (1)
- Posterpräsentation (1)
Sprache
- Englisch (59) (entfernen)
Schlagworte
- Creep (11)
- Aging (9)
- Microstructure (7)
- Additive manufacturing (5)
- Aluminium alloy (5)
- Ontology (5)
- Shear modulus (5)
- Young's modulus (5)
- EN AW-2618A (4)
- Elastic modulus (4)
- Mechanical testing (4)
- P92 (4)
- Stress relaxation (4)
- AISI 316L (3)
- Additive Manufacturing (3)
- Aluminium (3)
- Aluminum alloys (3)
- Fatigue (3)
- Reference data (3)
- S-phase (3)
- Tempered martensite-ferritic steel (3)
- Ti-6Al-4V (3)
- AGIL (2)
- Alloy 2618A (2)
- Aluminum alloy (2)
- Brinell hardness (2)
- Coarsening (2)
- Copper alloys (2)
- Creep-fatigue (2)
- Damage (2)
- Data management (2)
- Data mapping (2)
- Dataset (2)
- Degradation (2)
- Electron microscopy (2)
- FAIR data (2)
- Microstructure evolution (2)
- Nickel-base alloy (2)
- Ostwald ripening (2)
- Phase-field simulation (2)
- Precipitation (2)
- Residual stress (2)
- S-Phase (2)
- TEM (2)
- Tempered Martensite Ferritic Steels (2)
- Tensile test (2)
- Thermomechanical fatigue (2)
- Transmission electron microscopy (2)
- 316L (1)
- 9-12%Cr steel (1)
- AM (1)
- Al-Cu alloy (1)
- Al-Cu-Li-alloy (1)
- Al2CuMg (1)
- Alloy 2818A (1)
- Anisotropy (1)
- Austenitic cast iron (1)
- Automated image analysis (1)
- Bitter technique (1)
- CALPHAD (1)
- Casting (1)
- Characterisation (1)
- Charpy test (1)
- Chemo-mechanical coupling (1)
- Computed Tomography (1)
- Creep behavior (1)
- Creep data (1)
- Creep, Creep Rupture, and Stress Rupture (1)
- Creep-Fatigue (1)
- Creep-fatigue interaction (1)
- Crystal Defects (1)
- Crystal plasticity (1)
- Cyclic loading (1)
- Cyclic softening (1)
- Data Interoperability (1)
- Data Mapping (1)
- Data format (1)
- Data infrastructures (1)
- Data linking (1)
- Defects phase diagram (1)
- Defects thermodynamics (1)
- Deformation (1)
- Density-based model (1)
- Differential scanning calorimetry (DSC) (1)
- Digital image correlation (1)
- Digital material representation (1)
- Digital representation (1)
- Digital representations (1)
- Digital workflows (1)
- Digitization (1)
- Domain Ontology Development (1)
- Dwell periods (1)
- Dwell times (1)
- Dwell-Fatigue (1)
- EBSD (1)
- EN AW 2618A a (1)
- Elasticity (1)
- Environment (1)
- Expanding cavity model (1)
- FAIR (1)
- FAIR Data (1)
- FAIR Data Management (1)
- FAIR research data management (1)
- Fatigue crack growth (1)
- Fatigue crack propagation (1)
- Fatigue damage (1)
- Fe-Al alloys (1)
- Ferritic-martensitic steels (1)
- Ferritic–martensitic steel (1)
- Fractography (1)
- General Chemistry (1)
- General Computer Science (1)
- General Engineering (1)
- General Materials Science (1)
- Hardness test (1)
- Heat treatment (1)
- High cycle fatigue (1)
- High temperature mechanical properties (1)
- IN 718 (1)
- IN718 (1)
- In-situ Process Monitoring (1)
- Inconel 718 (1)
- Indentation (1)
- Industrial and Manufacturing Engineering (1)
- Interfacial anisotropy (1)
- Intermetallics (1)
- Iron aluminides (1)
- Knowledge Graph (1)
- Knowledge Representation (1)
- Knowledge graph (1)
- Knowledge graphs (1)
- Laser Powder Bed Fusion (1)
- Laser Powder Bed Fusion (LPBF) (1)
- Laser beam melting (LBM) (1)
- Laser powder bed fusion (1)
- Laser powder-based directed energy deposition (1)
- Lifetime prediction (1)
- Long-term aging (1)
- Long-term behavior (1)
- Low Cycle Fatigue (1)
- Low Cycle Fatigue (LCF) (1)
- Low cycle fatigue (1)
- Low strain (1)
- Low-cycle fatigue (1)
- Low-cycle fatigue. (1)
- Magnetic domain distribution (1)
- Magnetic stray fields (1)
- Magnetomechanical effect (1)
- Material degradation (1)
- Materials Chemistry (1)
- Materials Testing (1)
- Materials informatics (1)
- Mechanical Engineering (1)
- Mechanical anisotropy (1)
- Mechanical behavior (1)
- Mechanics of Materials (1)
- Metadata schema (1)
- Metal magnetic memory (1)
- Metal seal (1)
- Metals and Alloys (1)
- Micromechanical model (1)
- Microstructure analysis (1)
- Microstructure-property-correlation (1)
- Misfitting precipitate (1)
- Modeling (1)
- Multiaxial deformation (1)
- Ni-Resist (1)
- Nimonic 75 (1)
- Non-destructive Materials (1)
- Notch (1)
- Number density (1)
- Ontologies (1)
- PBF-LB/M/316L (1)
- Parametric modeling (1)
- Plastic deformation (1)
- Precipitate shape (1)
- Precipitation hardening (1)
- Process development (1)
- Radii distribution (1)
- Reference material BCR-425 (1)
- Referenzdaten (1)
- Reheating (1)
- Relaxation fatigue (1)
- Relaxation tests (1)
- Reproducibility (1)
- S355 steel sheet (1)
- Safety (1)
- Selective laser melting (SLM) (1)
- Semantic Web Technologies (1)
- Simulation (1)
- Standardisation (1)
- Standardization (1)
- Strain difference (1)
- Strength (1)
- Structural steel (1)
- Symmetric dwell periods (1)
- Syngle Crystal alloy (1)
- T1 precipitate (1)
- Temperature dependence (1)
- Tensile Test Ontology (1)
- Tensile data (1)
- Tensile properties (1)
- Tensile strength (1)
- Tensile testing (1)
- Thermo-Mechanical Fatigue (1)
- Thermomechanical Fatigue (TMF) (1)
- Thesaurus (1)
- Thickening (1)
- Topography (1)
- Transmission electron microscopy (TEM) (1)
- Vickers Hardness (1)
- Vickers hardness (1)
- Visual ontology development (1)
- Vocabulary providers (1)
- Volume fraction (1)
- microstructural changes (1)
- γ″ phase (1)
- θ′ phase (1)
- θ′-(Al2Cu) precipitate phase (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (59)
- 5.2 Metallische Hochtemperaturwerkstoffe (59)
- 5.5 Materialmodellierung (11)
- 9 Komponentensicherheit (11)
- 5.1 Mikrostruktur Design und Degradation (10)
- 8 Zerstörungsfreie Prüfung (9)
- 9.6 Additive Fertigung metallischer Komponenten (7)
- 8.5 Röntgenbildgebung (6)
- 8.0 Abteilungsleitung und andere (3)
- 9.3 Schweißtechnische Fertigungsverfahren (3)
Eingeladener Vortrag
- nein (7)
The current competitive situation on electricity markets forces power plants into cyclic operation regimes with frequent load shifts and starts/shutdowns. In the present work, the cyclic mechanical behavior of ferritic-martensitic 9-12 % Cr steels under isothermal and thermomechanical loading was investigated for the example of grade P92 material. A continuous softening was observed under all loading conditions. The introduction of hold periods to the applied cycles reduced material lifetime, with most prominent effects at technologically relevant small strain levels. The microstructural characterization reveals a coarsening of the original “martensitic” lath-type microstructure to a structure with polygonal subgrains and reduced dislocation density. The microstructural data forms the input for a physically-based modelling approach.
Creep-fatigue of P92 in service-like tests with combined stress- and strain-controlled dwell times
(2023)
Complex service-like relaxation- and creep-fatigue tests with strain- and stress-controlled dwells and fatigue cycle durations of approx. 2200 s were performed exemplarily on a grade P92 steel at 620 ◦C in this study. The results indicate deviations in the prevailing creep mechanisms of long-term relaxation and creep dwells, affecting subsequent dwells, load shifts, and the macroscopic softening behavior quite differently. In addition, fracture surfaces and longitudinal metallographic sections reveal intergranular crack growth for complex loading with stress-controlled dwells, whereas complex strain-controlled tests enhance oxidation and transgranular crack propagation. These findings substantiate the limited transferability of relaxation-fatigue to creep-fatigue conditions.
In Germany spent nuclear fuel and high level radioactive waste is stored in interim storage containers with double lid systems. Those lids are equipped with metal seals (e.g. Helicoflex®) that ensure the safe enclosure of the inventory. The used metal seals consist of three components as can be seen in the cross-sectional view in Figure 1. The innermost part is a helical spring that is surrounded by an inner jacket made of stainless steel. The outer jacket that is made of a softer material which in case of assembly in the aforementioned storage containers is silver or aluminum (i.e. Al 99.5). During application the seal is compressed and due to the restoring force of the helical spring, the outer jacket is plastically deformed and adapts to the sealing surface. Hence, leakage paths are closed and the sealing function is generated. In Germany the above-mentioned containers are licensed for up to 40 years of interim storage, which in case extended storage becomes necessary before a final repository is available will have to be extended to even longer periods. Therefore, the evaluation of the long-term behavior of the seals is necessary, taking into account storage conditions, decay heat and possible mechanical loads as well.
At Bundesanstalt für Materialforschung und –prüfung (BAM) long-term investigations are being conducted in which seals are assembled in test flanges and aged at temperatures ranging from room temperature to 150°C for accelerated aging. The aged seals are tested semi-annually (after the first 6 months in which the seals are tested more frequently) regarding the sealing performance, the remaining seal force, and the useable resilience upon decompression. Results of these investigations have been published over the past years (e.g. Grelle, Wolff, Probst, Jaunich, & Völzke, 2017; Völzke, Wolff, Probst, Nagelschmidt, & Schulz, 2014). It was found that the seal force and the useable resilience decrease with time and temperature, which is in agreement with the result of other studies (Sassoulas et al., 2006; Wataru et al., 2016) as well. Geometry change of the outer jacket has been identified as the main reason for this seal behavior. At the prevailing operating temperatures and stresses the aluminum is subjected to creep deformation leading to a thinning of the outer jacket. Since the seal groove depth remains unchanged the helical spring expands, which in turn leads to a decrease of the generated spring and seal force.
Although the main reason for the change of seal parameters over time and temperature is known, a detailed characterization of the seal behavior and a reliable prediction of the parameter development for aging times that exceed the experimental time frame have not been possible, yet.
For deeper understanding of the aging processes, an Investigation program, which is covered in this contribution, is conducted at Bundesanstalt für Materialforschung und –prüfung (BAM) that focusses on the behavior of the aluminum jacket and its influence on the long-term sealing performance. The program investigates properties of material samples as well as the behavior of the seal as a component.
Original sheet material of the same aluminum that is used for manufacturing of the seals is investigated in compression creep tests. For this, a DMA (dynamic mechanical analysis) machine is employed (here used for static tests) that allows for a measurement of the specimens deformation under forces of up to 500 N. The advantage of this method is that the original material can be tested in the same shape as used for the seals which is 0.5 mm thick sheet material. For investigation of tensile creep standard specimens are used, that were machined from surrogate material of the same composition and annealing condition.
Furthermore, aluminum seals that are cut into smaller segments are assembled in flanges and placed in heating chambers at temperatures ranging from 23°C to 150°C. After different periods of time from 3 days to 300 days the segments are taken out of the flanges and are investigated, thus giving information on different states of aging. Measurements of the development of the seal contact width and the aluminum jacket thickness are done with an optical microscope. Further investigations on the segments will include metallography and hardness measurements.
From the detailed material and component behavior including the results of the long-term seal force and useable resilience investigations a better understanding of the overall seal behavior can be gained. The aim is to contribute to the development of material models and analytical approaches for the prediction of the sealing behavior in dependence of time and temperature.
Creep and creep damage behavior of stainless steel 316L manufactured by laser powder bed fusion
(2022)
This study presents a thorough characterization of the creep properties of austenitic stainless steel 316L produced by laser powder bed fusion (LPBF 316L) contributing to the sparse available data to date. Experimental results (mechanical tests, microscopy, X-ray computed tomography) concerning the creep deformation and damage mechanisms are presented and discussed. The tested LPBF material exhibits a low defect population, which allows for the isolation and improved understanding of the effect of other typical aspects of an LPBF microstructure on the creep behavior. As a benchmark to assess the material properties of the LPBF 316L, a conventionally manufactured variant of 316L was also tested. To characterize the creep properties, hot tensile tests and constant force creep tests at 600 °C and 650 °C are performed. The creep stress exponents of the LPBF material are smaller than that of the conventional variant. The primary and secondary creep stages and the times to rupture of the LPBF material are shorter than the hot rolled 316L. Overall the creep damage is more extensive in the LPBF material. The creep damage of the LPBF material is overall mainly intergranular. It is presumably caused and accelerated by both the appearance of precipitates at the grain boundaries and the unfavorable orientation of the grain boundaries. Neither the melt pool boundaries nor entrapped gas pores show a significant influence on the creep damage mechanism.
A study was made on the effect of creep loading on the precipitate radii evolution of the aluminum alloy 2618A.
The overageing process of the alloy was investigated under load at a temperature of 190 °C with stresses between 79 and 181 MPa and compared to stress free isothermal ageing. The precipitates responsible for strength were characterized using dark-field transmission electron microscopy (DFTEM). This allows the experimental Determination of radii distributions of the rod-shaped Al2CuMg precipitates and the evaluation regarding their mean precipitate radius. It was found that the mean precipitate radius enables the comparison of the different microstructural conditions of crept and uncrept samples. The mean precipitate radii of the samples experiencing creep are significantly higher than those of undeformed samples. It was shown that the acquired radii distributions are viable to determine averaged particle radii for comparison of the aged samples. A ripening process including pipe diffusion along dislocations describes the data on coarsening very well for the creep samples.
Characterization of Ti-6Al-4V fabricated by multilayer laser powder-based directed energy deposition
(2022)
Laser powder-based directed energy deposition (DED-L) is increasingly being used in additive manufacturing (AM). As AM technology, DED-L must consider specific challenges. It must achieve uniform volume growth over hundreds of layers and avoid heat buildup of the deposited material. Herein, Ti–6Al–4V is fabricated using an approach that addresses these challenges and is relevant in terms of transferability to DED–L applications in AM. The assessment of the obtained properties and the discussion of their relationship to the process conditions and resulting microstructure are presented. The quality of the manufacturing process is proven in terms of the reproducibility of properties between individual blanks and with respect to the building height. The characterization demonstrates that excellent mechanical properties are achieved at room temperature and at 400 °C.
The Gibbs free energy of a grain boundary is a complex thermodynamic function of temperature, pressure, and composition. These complexities add to the intrinsic crystallographic and chemical constraints imposed by the adjacent bulk phase. Recently we have proposed a density-based model for assessing grain boundary thermodynamics that enables a CALPHAD-informed description of the grain boundary. As such, the Gibbs free energy of the grain boundary is directly linked with available CALPHAD thermodynamic data. In this talk, new aspects of interfacial segregation and phase transformation are revealed by benchmarking the current model for various experimental cases, including several steels, high-entropy alloys and aluminum alloys. The effects of elastic interactions on the grain boundary segregation and the application of the model to a nanocrystalline Pt-Au alloy, with numerous grain boundaries of various characters, will be discussed.
The article covers data on the Brinell hardness of the forged precipitation-hardened aluminum alloy EN AW-2618A in the initial T61 condition (i. e. slightly underaged) and after isothermal aging for up to 25,0 0 0 h at aging temperatures between 160 °C and 350 °C. In addition, the hardness was determined on specimens after creep testing at 190 °C and various stresses. The hardness decreases with increasing ag- ing time due to the microstructural evolution of the harden- ing precipitates. The drop occurs faster the higher the aging temperature. Aging under creep load additionally accelerates the hardness decrease.