Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (47) (entfernen)
Sprache
- Englisch (43)
- Deutsch (2)
- Mehrsprachig (2)
Schlagworte
- Microstructure (8)
- Aging (5)
- Creep (5)
- Fatigue (4)
- Additive Manufacturing (3)
- Cast iron (3)
- AGIL (2)
- AISI 316L (2)
- Additive manufacturing (2)
- Aluminum alloy (2)
- Aluminum alloys (2)
- Cyclic softening (2)
- Damage (2)
- Elasticity (2)
- Electron microscopy (2)
- Fatigue damage (2)
- Mikrostruktur (2)
- Number density (2)
- Ostwald ripening (2)
- P92 (2)
- Phase-field simulation (2)
- Precipitation (2)
- Residual stress (2)
- S-Phase (2)
- Schädigung (2)
- Stress relaxation (2)
- Tempered martensite-ferritic steel (2)
- Tensile strength (2)
- Thermo-mechanical fatigue (2)
- Thermomechanical fatigue (2)
- Ti-6Al-4V (2)
- Volume fraction (2)
- 316L (1)
- 9-12%Cr steel (1)
- Acoustic emission (1)
- Advanced ceramic (1)
- Age hardening (1)
- Al-Cu alloy (1)
- Al-Cu-Li-alloy (1)
- Alterung (1)
- Aluminiumlegierung (1)
- Al‐Cu‐Li‐alloy (1)
- Anisotropie (1)
- Automated image analysis (1)
- Axial-torsional Loading (1)
- Axial-torsional loading (1)
- Bitter technique (1)
- Brinell hardness (1)
- Carbon capture and storage (CCS) (1)
- Casting skin (1)
- Ceramics (1)
- Chaboche (1)
- Characterisation (1)
- Chemo-mechanical coupling (1)
- Computed Tomography (1)
- Computersimulation (1)
- Corrosion behaviour (1)
- Cracks (1)
- Creep behavior (1)
- Creep strength (1)
- Creep testing (1)
- Creep-fatigue (1)
- Creep-fatigue interaction (1)
- Crystal plasticity (1)
- Damage analysis (1)
- Data Interoperability (1)
- Data infrastructures (1)
- Data mapping (1)
- Deformation (1)
- Differential scanning calorimetry (DSC) (1)
- Digital image correlation (1)
- Digital representations (1)
- Digital workflows (1)
- Domain Ontology Development (1)
- Dwell periods (1)
- Dwell times (1)
- EN AW-2618A (1)
- Elastic modulus (1)
- Elastische Energie (1)
- Emission coefficient (1)
- Environment (1)
- Expanding cavity model (1)
- FAIR (1)
- FAIR Data Management (1)
- FAIR research data management (1)
- Fatigue assessment (1)
- Fatigue life time (1)
- Ferritic–martensitic steel (1)
- Fossil fuel power plants (1)
- Fracture (1)
- Fraktographie (1)
- Gamma titanium aluminide (1)
- Gamma-Titanium Aluminide (1)
- General Chemistry (1)
- General Computer Science (1)
- General Engineering (1)
- General Materials Science (1)
- Growth kinetics (1)
- Hall-Petch relationship (1)
- Heat resistant steels (1)
- Heat treatment (1)
- High Cycle Fatigue (HCF) (1)
- High efficiency power plants (1)
- Hocheffiziente Kraftwerke (1)
- IN 718 (1)
- In-situ Process Monitoring (1)
- Inconel 718 (1)
- Indentation (1)
- Industrial and Manufacturing Engineering (1)
- Interfacial anisotropy (1)
- Isothermal fatigue (1)
- Knowledge Representation (1)
- Knowledge graphs (1)
- Kohlendioxidabscheidung und -speicherung (CCS) (1)
- Korrosionsverhalten (1)
- Kriechen (1)
- Laser Powder Bed Fusion (1)
- Laser Powder Bed Fusion (LPBF) (1)
- Laser beam melting (LBM) (1)
- Laser irradiation (1)
- Laser powder bed fusion (1)
- Laser powder-based directed energy deposition (1)
- Laser-thermal shock (1)
- Lebensdauerabschätzung (1)
- Lebensdauervorhersage (1)
- Life time prediction (1)
- Lifetime (1)
- Lifetime prediction (1)
- Long-term aging (1)
- Low cycle fatigue (1)
- Low strain (1)
- Low-cycle fatigue (1)
- Magnetic domain distribution (1)
- Magnetic stray fields (1)
- Magnetomechanical effect (1)
- Materialmodell (1)
- Materials Chemistry (1)
- Materials Testing (1)
- Materials informatics (1)
- Mechanical Engineering (1)
- Mechanical anisotropy (1)
- Mechanical properties (1)
- Mechanics of Materials (1)
- Mechanische Eigenschaften (1)
- Metal magnetic memory (1)
- Metal matrix composites (1)
- Metals and Alloys (1)
- Microscopy (1)
- Microstructure evolution (1)
- Miniature specimen (1)
- Misfitting precipitate (1)
- Molybdenum (1)
- Multiaxial deformation (1)
- Multi‐component diffusion (1)
- Nickel-base alloy (1)
- Non-destructive Materials (1)
- Notch (1)
- Ontologies (1)
- Ontology (1)
- P91 (1)
- PBF-LB/M/316L (1)
- Parametric modeling (1)
- Phase‐field modeling (1)
- Plastic deformation (1)
- Precipitate shape (1)
- Precipitates (1)
- Process development (1)
- Quantitative Analyse (1)
- Radiation thermometry (1)
- Reference data (1)
- Reheating (1)
- Relaxation fatigue (1)
- Reproducibility (1)
- S-phase (1)
- SSiC (1)
- Safety (1)
- Selective laser melting (SLM) (1)
- Semantic Web Technologies (1)
- Shear modulus (1)
- Size effects (1)
- Solid solution softening (1)
- Solid solution strengthening (1)
- Standardisation (1)
- Strain difference (1)
- Stress distribution (1)
- Structural steel (1)
- Symmetric dwell periods (1)
- T1 precipitate (1)
- TMF (1)
- TNB-V5 (1)
- Temperature dependence (1)
- Temperature measurement (1)
- Tempered martensite ferritic steels (1)
- Tensile Test Ontology (1)
- Tensile properties (1)
- Thermal barrier coating (TBC) (1)
- Thermal shock (1)
- Thermal shock stress (1)
- Thermo-mechanical Fatigue (1)
- Thermography (1)
- Thermomechanical Fatigue (TMF) (1)
- Thermomechanical fatigue (TMF) (1)
- Thermoschock (1)
- Thickening (1)
- Titanaluminide (1)
- Titanium alloys (1)
- Topography (1)
- Transmission electron microscopy (1)
- Transmission electron microscopy (TEM) (1)
- Visual ontology development (1)
- Vocabulary providers (1)
- Warmfeste Stähle (1)
- Weibull statistics (1)
- Young's modulus (1)
- Yttria stabilized zirconia (1)
- microstructural changes (1)
- γ″ phase (1)
- θ′ phase (1)
- θ′-(Al2Cu) precipitate phase (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (28)
- 5.2 Metallische Hochtemperaturwerkstoffe (28)
- 8 Zerstörungsfreie Prüfung (9)
- 5.1 Mikrostruktur Design und Degradation (8)
- 9 Komponentensicherheit (8)
- 5.5 Materialmodellierung (6)
- 8.5 Röntgenbildgebung (6)
- 9.6 Additive Fertigung metallischer Komponenten (4)
- 8.0 Abteilungsleitung und andere (3)
- 9.3 Schweißtechnische Fertigungsverfahren (3)
MoSi alloys containing up to 1 wt.% Si were fabricated by powder-metallurgical processing and their lattice parameters, elastic constants, densities, grain sizes, strengths, ductilities, and fracture toughness values were measured. The yield strength was insensitive to the grain size, i.e., a HallPetch relationship was not observed. Generally, Si additions caused pronounced solid solution strengthening. However, for small Si concentrations (≤0.1 wt.%) solid solution softening was observed at room temperature and below. With increasing Si concentration, the room temperature ductility and fracture toughness dropped precipitously. This is attributed to the increase in strength and a transition from transgranular to intergranular fracture.
A miniature specimen geometry is presented that allows to extract small samples for tensile creep tests directly from critical components of steam generators in power plants like e.g. superheater tubes. In this way, material can be tested which has been subjected to the full processing chain of the component. The specimens then exhibit all microstructural modifications that are present in the component after the shaping process and heat treatment, and representative mechanical properties are determined. Similarly, specimens can be extracted from pre-corroded test pieces or used components after service to determine the impact of complex aging/loading/oxidation conditions during service on the mechanical properties of the material. The applicability of the miniature specimen test method is demonstrated in a comparative creep study involving standard and miniature specimens of P91 tempered martensite ferritic steel. Test results indicate satisfactory accuracy/repeatability of the method. Comparison with large scale specimen data reveals an influence of specimen size on the obtained creep behavior. These size effects need to be considered for a correct interpretation of results from miniature specimen creep tests.
The uniaxial, torsional and axial-torsional thermomechanical fatigue (TMF) behavior of the near-γ TiAl-alloy TNB-V5 was investigated. TMF tests were performed at 400-800 °C with mechanical strain amplitudes ranging from 0.15% to 0.7%. The tests were conducted thermomechanically in-phase (IP) and out-of-phase (OP).
For the same lifetimes, uniaxial IP tests required the highest strain amplitudes, while OP test conditions were most damaging and needed the lowest strain amplitudes. The Mises equivalent mechanical strain amplitudes of pure torsional tests were found in between uniaxial in-phase and out-of-phase tests for the same lifetimes. The non-proportional multiaxial out-of-phase test showed a lower lifetime at the same equivalent mechanical strain amplitude compared to the other types of tests.
The microstructure has been characterized applying electron microscopy and microstructural parameters such as fraction of twinned grains, grain size, lamellar distance and dislocation density have been quantified.
In recent years, the design and development of materials are strongly interconnected with the development of digital technologies. In this respect, efficient data management is the building block of material digitization and, in the field of materials science and engineering (MSE), effective solutions for data standardization and sharing of different digital resources are needed. Therefore, ontologies are applied that represent a map of MSE concepts and relationships between them. Among different ontology development approaches, graphical editing based on standard conceptual modeling languages is increasingly used due to its intuitiveness and simplicity. This approach is also adopted by the Materials-open-Laboratory project (Mat-o-Lab), which aims to develop domain ontologies and method graphs in accordance with testing standards in the field of MSE. To suit the actual demands of domain experts in the project, Ontopanel was created as a plugin for the popular open-source graphical editor diagrams.net to enable graphical ontology editing. It includes a set of pipeline tools to foster ontology development in diagrams.net, comprising imports and reusage of ontologies, converting diagrams to Web Ontology Language (OWL), verifying diagrams using OWL rules, and mapping data. It reduces learning costs by eliminating the need for domain experts to switch between various tools. Brinell hardness testing is chosen in this study as a use case to demonstrate the utilization of Ontopanel.
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.
A material family to replace the current superalloys in aeronautical gas turbine engines is
considered to be that of gamma Titanium Aluminide (γ-TiAl) alloys. Structural components in
aeronautical gas turbine engines typically experience large variations in temperatures and multiaxial
states of stress under non-isothermal conditions. The uniaxial, torsional and bi-axial thermomechanical
fatigue (TMF) behaviour of this γ-TiAl alloy have been examined at 400 800°C with
strain amplitudes from 0.15% to 0.7%. The tests were conducted at both in-phase (IP) and out-ofphase
(OP). The effects of TMF on the microstructure were also investigated. For the same
equivalent mechanical strain amplitude uniaxial IP tests showed significantly longer lifetimes than
pure torsional TMF tests. The non-proportional multiaxial OP test showed the lowest lifetimes at
the same equivalent mechanical strain amplitude compared to the other types of tests.
The present work covers the mechanical behaviour of Timetal LCB under fatigue loading and utilizes transmission electron microscopy (TEM) to study the associated microstructural evolution. Fatigue specimens were taken out of LCB wire made for automotive suspension spring manufacturing in a solution treated as well as an additionally aged state. Uniaxial fatigue tests were carried out in total strain control with R = 0.1. Solution treated specimens tested at 3% and 4% maximum total strain showed a saturating force response, which differed from all other total strain controlled tests, and a distinct fracture behaviour. In addition, an increase of the dynamic Young's modulus is observed under these test conditions and in this material state. These findings are interpreted as a deformation induced precipitation of nanosize α- or ω-phase.
In the aged state, the α-phase carries the major part of deformation work, noticeable by distinct α-substructures in fatigued specimen states.
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.
Due to their excellent creep resistance and good oxidation resistance, 9–12% Cr ferritic–martensitic stainless steels are widely used as high temperature construction materials in power plants. However, the mutual combination of different loadings (e.g., creep and fatigue), due to a “flexible” operation of power plants, may seriously reduce the lifetimes of the respective components. In the present study, low cycle fatigue (LCF) and relaxation fatigue (RF) tests performed on grade P92 helped to understand the behavior of ferritic–martensitic steels under a combined loading. The softening and lifetime behavior strongly depend on the temperature and total strain range. Especially at small strain amplitudes, the lifetime is seriously reduced when adding a hold time which indicates the importance of considering technically relevant small strains.
Components in the Aerospace, Power and Automotive engineering sectors are frequently subjected to cyclic stresses induced by thermal fluctuations and mechanical loads. For the design of such components, reliable material property data are required which need to be acquired using well accepted and reproducible test procedures for thermo-mechanical fatigue (TMF) loading. There is limited availability of proven TMF data indicating there is need for further research and testing. The TMF behaviour of materials is often desired to be simulated in models which describe the cyclic stress-strain behaviour, the fatigue life and the cyclic crack growth behaviour. There is a continuous need for the development and amendment of such models. Models can be validated by using materials in industrial applications which are subjected to TMF loading.
The 3rd Workshop on Thermo-Mechanical Fatigue was held on 27–29 April 2016 at BAM, Berlin, Germany. The workshop was attended by 90 attendees coming from 17 countries in the world. 38 presentations including five poster presentations were held.
The following topics were covered by the workshop:
– TMF of materials coated with Thermal Barrier Coatings.
– Thermal Gradient Mechanical Fatigue.
– TMF crack growth.
– TMF + High Cycle Fatigue.
– TMF Modelling and Lifetime Prediction.
– TMF Properties of steels, cast iron, Al-, Mg- and Ni-alloys
– Advanced TMF Testing Techniques.
– Industrial Applications.
A panel discussion was held regarding the present state of TMF testing standards (ISO and ASTM) and their potential for improvement. The discussion and contributions were summarized and forwarded to the standard committees. The 3rd TMF-Workshop ensured the continuation of international exchange of knowledge providing a forum to present and discuss all recent developments in the field of thermo-mechanical fatigue.
The current special issue publishes eleven selected papers of the 3rd TMF-Workshop 2016. The papers were peer reviewed by a number of experts in the Thermo-Mechanical Fatigue sector. I hope you will enjoy reading papers of this special issue.
Werkstoffe im Hochtemperatureinsatz verändern mit der Zeit ihre Mikrostruktur. Mit diesem Alterungsprozess einher geht eine Veränderung der mechanischen Eigenschaften ebenso wie eine Veränderung des Schädigungsverhaltens. Im Rahmen des FVV Vorhabens „Alterung und Lebensdauer“ haben das Fraunhofer IWM in Freiburg und die BAM in Berlin die weit verbreitete warmfeste Aluminiumlegierung EN AW-2618A in verschiedenen Alterungszuständen experimentell charakterisiert und darauf aufbauend Modelle für die Lebensdauerbewertung mit der Finite-Elemente- Methode implementiert.
Materials subjected to high-temperature service conditions will change their microstructure with time. Associated with this aging process is a change of mechanical properties as well as a change of damage mechanisms. Within the scope of the FVV project Aging and Lifetime, Fraunhofer IWM in Freiburg and BAM in Berlin (both Germany) experimentally characterized the widespread high-temperature aluminum alloy EN AW-2618A in different overaging states. Based on the experimental findings, models for numerical lifetime assessment with the finite-element method were implemented.
Iron aluminides, already reported in the late 19th century, did not cease to attract the interest of scientists and engineers ever since. Besides good oxidation resistance, low density and resource availability, potentials for hightemperature strengths that compete with high-alloy steels were unlocked by low alloy contents. Still, research on alloy design continues, as alloying usually comes at the price of brittleness in low-temperature regimes. A potential candidate is the quinary Fe–Al–Mo–Ti–B system which is strengthened by solid solution and eutectic borides. It was shown to have good strength and outstanding creep resistance under compressive loading up to elevated temperatures. Although the individual effect of alloy additions is well understood in iron aluminides, little is known about the combined effects of alloying concentrations on microstructure, phase stability and mechanical properties. Therefore a systematic study of two Ti-doped near-Fe3Al alloys with varying contents of Mo (2–4 at.%) and B (0.5–1 at.%) was conducted. In total eight different alloys were fabricated by investment casting into ceramic shell molds. Alloys were characterized and compared by grain size, phase transitions, microstructure evolution as well as elemental compositions and volume fractions of phases. For mechanical characterization, macrohardness and microhardness tests as well as tensile tests at ambient and high tempera tures were conducted. Independent of alloy additions, alloys with 24–25 at.% Al exhibit superior proof strength due to a higher matrix hardness. Decreasing B content generally decreases strength by lower secondary phase fractions which contribute via particle hardening. Reducing Mo content decreases both the solute concentration in the matrix and secondary phase fractions. Surprisingly, strength is similar or even superior to alloys with higher Mo content. Strength relations are discussed with a focus on solid-solution hardening theory and other competing strengthening mechanisms.
The fatigue behaviour of cast iron is usually investigated on machined specimens. Components of cast iron, however, have a casting skin; therefore the investigation of the influence of the casting skin on the lifetime is of interest. To study this influence isothermal fatigue tests were carried out on heat-resisting spheroidal graphite cast iron EN GJS SiMo 4.05 in 4–point-bending set-up at 400 °C. Specimens with and without casting skin were investigated comparatively. The number of cycles to failure was significantly lower for specimens with casting skin. Metallographic investigations underline the reduction of lifetime caused by casting skin.
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.
A titanium (Ti-6242) matrix composite reinforced with continuous SiC fibers was studied. The mechanical behavior of the matrix and the composite was characterized by tensile, creep and isothermal fatigue tests at room temperature and up to 550°C. The thermo-mechanical fatigue behavior under in-phase and out-of-phase conditions was investigated for the composite between 100 and 550°C. Fracture surfaces were characterized by confocal light microscopy and by scanning electron microscopy to identify the damage mechanisms.
Der vorliegende Beitrag beschreibt typische Bruchmuster, die an SSiC Proben nach Thermoschockexperimenten beobachtet wurden und korreliert diese qualitativ mit der aufgebrachten Belastung. Der Thermoschock wird durch eine schnelle, in der Probenmitte beginnende spiralförmige Aufheizung dünner Scheiben mit Laserstrahlung realisiert. Durch diese Versuchsführung wandert ein zunehmender Temperaturgradient von der Mitte beginnend in radialer Richtung durch die Probe. Dieser Temperaturgradient ist für die Ausbildung von Druckspannungen im Probeninneren und Zugspannungen im kalten Randbereich der Probe verantwortlich. Beim Erreichen einer kritischen, versagensrelevanten Spannung tritt Probenbruch auf. Dabei wird die bis zu diesem Zeitpunkt in der Probe gespeicherte elastische Energie teilweise in die Schaffung von Rissoberflächen umgewandelt. Der Zusammenhang zwischen gespeicherter elastischer Energie und Bruchmuster wird dargestellt.
Thermal barrier coatings (TBCs) are used to increase the operating temperature of land-, sea-, or air-based turbines. As failure of the coating may result in serious damage of the turbine, reliable estimation of the lifetime is essential. Most experiments to assess the lifetime or to determine parameters for simulations of the behavior of TBCs are done by burner-rig-tests, where the operating conditions are simulated by cyclic heating of the surface and cooling of the backside of a coated sample.
In this work a possibility is presented to do comparable experiments by heating the surface with laser irradiation instead of a burner. For this purpose a Nd:YAG-laser with a maximum output power of 1?kW and a wavelength of 1064?nm is used. The laser spot can be moved by integrated optics across the sample surface to achieve homogeneous heating of the coating. Cooling of the backside is done by air. The temperature of the sample surface is determined by an infrared-camera which also enables the possibility to detect failures in the coating via thermography. Additionally, acoustic sensors attached to the sample holder are used to detect failures in the sample. The investigated ceramic material (yttria stabilized zirconia) has a very low absorption coefficient at the used laser wavelength. Therefore, a pre-treatment of the samples was needed to increase the absorption coefficient to be able to heat up the samples.
In this paper, the experimental setup and first experimental results are presented.