5 Werkstofftechnik
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- 2022 (54) (entfernen)
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- Additive manufacturing (7)
- Additive Manufacturing (6)
- Ceramics (5)
- Ontology (5)
- Fractography (4)
- Aluminium Alloy (3)
- Corrosion (3)
- EN AW-2618A (3)
- In-space manufacturing (3)
- LCF (3)
- Machine Learning (3)
- Microgravity (3)
- Microstructure (3)
- Transmission electron microscopy (3)
- μ-gravity (3)
- 3D printing (2)
- AGIL (2)
- Alkali zinc borate glasses (2)
- Aluminium alloy (2)
- CALPHAD (2)
- CO2 (2)
- Copper (2)
- Fatigue (2)
- Glass (2)
- High Cycle Fatigue (2)
- Laser beam melting (2)
- Laser powder bed fusion (2)
- Lunar regolith simulant (2)
- Material digital (2)
- Mechanical behavior (2)
- Microstructure Design (2)
- Neutron diffraction (2)
- Nickel-base superalloys (2)
- Notches (2)
- Sintering (2)
- Texture (2)
- Topography (2)
- 3D (1)
- Advanced ceramics (1)
- Advanced manufacturing (1)
- Aerospace (1)
- Aging (1)
- Alumina (1)
- Atmospheric plasma spraying (1)
- Austenitic steel 316L (1)
- Biaxial strength (1)
- Bioactive Glass (1)
- Bond energy (1)
- Brinell hardness (1)
- CCS (1)
- CCU (1)
- CO2 quality (1)
- Cantor alloy (1)
- Certified Referencematerial (1)
- Characterization (1)
- Co-firing (1)
- Creep data (1)
- Cross linking (1)
- Crystallization (1)
- Cubical Iron Oxide (1)
- Cure process (1)
- Damage Behavior (1)
- Data linking (1)
- Data management (1)
- Data mapping (1)
- Data structure (1)
- Degradation (1)
- Dielectric breakdown strength (1)
- Dielectric characterization (1)
- Diffraction (1)
- Digitization (1)
- Dynamic mechanical analysis (DMA) (1)
- EAC-1A (1)
- EBSD (1)
- EDX (1)
- Electric field distribution (1)
- Electrical insulation (1)
- Electron Microscopy (1)
- Electron backscatter diffraction (1)
- FAIR (1)
- FIB (1)
- Fatigue crack growth (1)
- Fe-Al alloys (1)
- Finite elmenet simulation (1)
- Fluorescence spectroscopy (1)
- Fracture surface (1)
- Fracture toughness (1)
- GD-OES (1)
- Geothermal (1)
- Glass fiber reinforced polymers (1)
- Graphic design (1)
- High entropy alloy (1)
- High temperature mechanical properties (1)
- Hydrogen sensor (1)
- ISRU (1)
- Implants (1)
- Infrastructure (1)
- Intermetallics (1)
- Interoperability (1)
- Iron aluminides (1)
- LTCC (1)
- Laser induced slipcasting (1)
- Layerwise slurry deposition (1)
- Life cycle (1)
- Lithium Ion Batteries (1)
- Low-Cycle-Fatigue (1)
- Lunar habitat (1)
- Mat-o-lab (1)
- Material Digital (1)
- Materials Modelling (1)
- Materials Science (1)
- Materials testing (1)
- Mechanical testing (1)
- Melt pool boundary (1)
- Microstructural characterization (1)
- Mortar (1)
- Multilayer technology (1)
- Nanoparticles (1)
- Nucleation mode (1)
- Ontology development (1)
- Oriented surface crystallization (1)
- Oxide glass (1)
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- Phase Diagrams (1)
- Phase-Field Simulations (1)
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- Platform MaterialDigital (PMD) (1)
- Powder (1)
- Precipitation Analysis (1)
- Precipitation hardening (1)
- Process monitoring (1)
- Residual Stress (1)
- Residual stress analysis (1)
- Roughness (1)
- S355 steel sheet (1)
- SEM (1)
- Scarf repairs (1)
- Silver cluster (1)
- Silver diffusion (1)
- Silver metallization paste (1)
- Slurry (1)
- Small-Angle X-ray Scattering (1)
- Solar sintering (1)
- Space exploration (1)
- Spark plasma sintering (1)
- Spray drying (1)
- Stainless steel (1)
- Structure (1)
- Sulfiding (1)
- Surface energy (1)
- TMF (1)
- TMF experiments (1)
- Tensile data (1)
- Tensile test (1)
- Thermoelectrics (1)
- Thermoset polymers (1)
- Thesaurus (1)
- Ti-6Al-4V (1)
- Tools (1)
- Transmission electron microscopy (TEM) (1)
- Ultrasound (1)
- Viscosity (1)
- X-ray diffraction (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (54)
- 5.2 Metallische Hochtemperaturwerkstoffe (18)
- 5.4 Multimateriale Fertigungsprozesse (17)
- 5.1 Mikrostruktur Design und Degradation (14)
- 5.6 Glas (6)
- 5.5 Materialmodellierung (5)
- 8 Zerstörungsfreie Prüfung (5)
- 9 Komponentensicherheit (5)
- 8.5 Röntgenbildgebung (4)
- 9.4 Integrität von Schweißverbindungen (3)
Artificial bone replacement by individual customized three-dimensional resorbable bioactive glass has not yet been widely established in the clinical use. This is mainly due to the antagonism of sintering ability and suitable bioactivity. Competitive crystallization often prevents the generation of dense sintered bodies, especially for additive manufactured 3D structures. Previous studies of the fluoride-containing glass F3 have shown its potential to combine both sintering ability and suitable bioactivity. Furthermore, the occurring sintering blockade by surface crystallization of Na2CaSi2O6 was tunable by glass particle size.
In this study the glasses F3, F3-Cu with 1 mol% CuO added at the expense of CaO and the well-known 13-93 were chosen to determine the influence of surface crystallization on 3D printed sinter bodies. For this purpose, grain size fractions in range of smaller 32 µm to 315 µm in fraction size of 6-20 µm were sieved from jaw crushed glass frit as well as glass cubes were cut from casted blocks for all glasses. Sintering behavior of both pressed and printed powder compacts was observed via heating microscopy. Crystallization was determined by DTA and crystallization progress was monitored on fractured sinter bodies and polished cubes via electron and laser scanning microscopy as well as with diffractometry.
Depending on grain size the formation of crystalline support framework along former grain boundaries shows the capability to stabilize fully densified sinter bodies before softening. Beside of this, the generation of complex hierarchic porosity was possible as well.
Due to combined cyclic mechanical and thermal loading during operation, the material of exhaust gas conducting components of combustion engines is exposed to thermomechanical fatigue (TMF). This leads to formation and growth of cracks, especially at the most highly stressed points of these components. In order to better predict the service life of cracked components before failure, it is necessary to identify a crack propagation law for the material used. Isothermal crack propagation tests have been carried out at several temperatures with a typical cast iron to identify such a law. The crack length is measured by the potential drop method. The compliance method, fractography and thermographic camera measurements have been used to validate and calibrate the potential drop measurements. Each of the isothermal tests has been simulated using a specially developed FEM-algorithm based on remeshing and remapping. This algorithm has been implemented in python and ABAQUS. Thereby, the crack tip region is modeled by collapsed Quad8 elements. From the individual simulations, the cyclic crack tip opening displacement (ΔCTOD) is extracted and regarded as a potential fracture mechanics parameter which controls the crack growth rate. By combining the data from the experiments and the simulations, the crack propagation law has been identified. Finally, anisothermal crack propagation tests have been performed for validation of the crack growth law.
Powder bed technologies are amongst the most successful Additive Manufacturing (AM) techniques. Powder bed fusion and binder jetting especially are leading AM technologies for metals and polymers, thanks to their high productivity and scalability.
The application of these techniques to most ceramics has been difficult so far, because of the challenges related to the deposition of homogeneous powder layers when using fine powders.
In this context, the "layerwise slurry deposition" (LSD) has been developed as a layer deposition method which enables the use of powder bed AM technologies also for advanced ceramic materials. The layerwise slurry deposition consists of the layer-by-layer deposition of a ceramic slurry by means of a doctor blade, in which the slurry is deposited and dried to achieve a highly packed powder layer. This offers high flexibility in the ceramic feedstock used, especially concerning material and particle size.
The LSD technology can be combined with binder jetting to develop the so-called “LSDprint” process for the additive manufacturing of ceramics.
The LSDprint technology combines the high-speed printing of binder jetting with the possibility of producing a variety of high-quality ceramics with properties comparable to those achieved by traditional processing.
In this presentation, the LSD process will be introduced and several examples of application ranging from silicate to high-performance ceramics will be shown.
Recent developments towards the scale-up and industrialization of this process will be discussed, alongside future perspectives for the multi-material additive manufacturing.
The mechanical strength of wrought high-strength aluminum alloys is essentially based on precipitation hardening, possibly in combination with prior forming, e. g. by stretching. Important parameters for achieving an optimum combination of hardness, strength, ductility, toughness, and further properties such as corrosion resistance are age-hardening temperature and time.
During thermal (mechanical) treatment, nucleation and growth of precipitates takes place, leading to the desired degree of hardening. In aluminum alloys, precipitation sequences are usually passed through, i. e. a sequence of metastable precipitates is formed before the stable phase can precipitate. The optimum combination of properties is therefore based on a certain (optimum) microstructure, which can, however, change during the use of a component, since the microstructure is not stable. This happens in particular when the operating temperatures are close to the aging temperature and/or the operating times are sufficiently long. An external mechanical load may accelerate the processes. The presentation gives some examples for this.
The studied aluminium alloy is EN AW-2618A (2618A). It is very widely used for exhaust gas turbo-charger compressor wheels. Due to long operating times, high cycle fatigue (HCF) and material aging under the influence of temperatures up to 230 °C is particularly relevant for the wheels. The wheels are typically milled from round wrought blanks. From such round blanks, different testpieces are extracted and a comprehensive series of HCF tests is conducted at room temperature. The tests investigate the materials fatigue performance in the T61 state for two load-ratios, namely R = -1 and R = 0.1. Additionally, two overaged material states are tested, accounting for the aging process the material undergoes during long operating times at high temperatures. The experimental results are evaluated and compared to each other.
Furthermore, the design process of notched specimens is presented. With the notched specimens, it is aimed to quantify the notch sensitivity of the material. Relating thereto, two potential model parameters for the fatigue lifetime model are introduced.
Due to the increasing scarcity of critical raw materials current high-temperature materials are sought to be replaced by alloys based on more abundant metals. One possibility within the class of intermetallics are iron aluminides, which combine sustainability and cost-efficiency with the prospect of mass savings. Iron aluminides show competitive specific strength up to 700 °C and excellent creep and wet corrosion resistance by small additions of Mo, Ti and B. Nevertheless, a Mo content of above 2 at.% which is needed for optimum corrosion resistance results in enhanced brittleness, especially at room temperature. This is why alloys with these Mo fractions were only mechanically tested under compressive loading so far. Still, testing of static and creep properties under tensile loading is required for reliable component design. Besides high standards for crack-free processing, data acquisition for tensile loads is especially complicated by environmental embrittling effects for iron aluminides. To cope with these challenges, the AiF research project “WAFEAL – Materials applications for iron aluminides” was initiated. The main goal is to collect standardised data on ambient and high-temperature tensile properties and creep properties. Samples with a nominal composition of Fe-26Al-4Mo-0.5Ti-1B [at.%] were manufactured via centrifugal casting in ceramic shell moulds followed by machining. Heat treatment for homogenisation and final polishing were carried out where appropriate. A summary of the achieved tensile and creep properties such as yield and tensile strength, maximum elongation, secondary creep rate and stress exponents will be given. Results will be also discussed regarding the influence of temperature, stress level and microstructure on the damage mechanisms. Furthermore, the effect of different alloy concentrations on the mechanical response at different temperatures will be outlined within a small experimental series.
The Binder Jetting BJ process is one of the most versatile additive manufacturing technologies in use. In this process a binder is locally jetted into a powder bed for the consolidation of a 3D structure, layer by layer. Basically, all materials which can be provided as a flowable powder and, thus, spreadable to a thin layer, can be processed. Metals, ceramics and polymers are processable, but also materials from nature, such as sand, wood sawdust and insect frass. Moreover, the BJ technology is adapted to large building volumes of some cubic meters easily. Besides these striking advantages, the manufacture of ceramic parts by BJ is still challenging, as the packing density of the powder bed is generally too low and the particle size of a flowable powder too large for a successful densification of printed parts in a subsequent sintering step to an advanced ceramic product. After an introduction of binder jetting in general and highlighting some examples, strategies for obtaining dense ceramic parts by BJ will be introduced.
Engineering grain boundaries demands a quantitative description of both their segregation and specific phase behavior. Recently I have proposed a density-based model for grain boundary thermodynamics that enables CALPHAD integrated derivation of grain boundary phase diagrams, broadly applied now in studying various alloys. Combining this model with experimental investigations, in this talk, new aspects of interfacial segregation and phase transformation revealed in polycrystalline alloys are discussed. The effect of elastic interaction on grain boundary phase behavior is incorporated. We consider Al alloys and novel high-entropy alloys and discuss a general strategy for grain boundary engineering.
Powder bed technologies are amongst the most successful Additive Manufacturing (AM) techniques. Powder bed fusion and binder jetting especially are leading AM technologies for metals and polymers, thanks to their high productivity and scalability. The application of these techniques to most ceramics has been difficult so far, because of the challenges related to the deposition of homogeneous powder layers when using fine powders. In this context, the “layerwise slurry deposition” (LSD) has been developed as a layer deposition method which enables the use of powder bed AM technologies also for advanced ceramic materials. The layerwise slurry deposition consists of the layer-by-layer deposition of a ceramic slurry by means of a doctor blade, in which the slurry is deposited and dried to achieve a highly packed powder layer. This offers high flexibility in the ceramic feedstock used, especially concerning material and particle size. The LSD technology can be combined with binder jetting to develop the so-called “LSDprint” process for the additive manufacturing of ceramics. The LSDprint technology combines the high-speed printing of binder jetting with the possibility of producing a variety of high-quality ceramics with properties comparable to those achieved by traditional processing. In this presentation, the LSD process will be introduced and several examples of application ranging from silicate to high-performance ceramics will be shown. Recent developments towards the scale-up and industrialization of this process will be discussed, alongside future perspectives for the multi-material additive manufacturing.
Low-temperature co-fired ceramics (LTCC) are used to fabricate multilayer circuits which are robust in harsh environments. Thick-film technology is well established for the metallization of circuit boards and microsystems. For specific sensor applications, the combination of LTCC and thin-film technology is advantageous to reach higher structure resolutions. Due to the high roughness of as-fired LTCC surfaces compared with silicon-wafers, the deposition of low-defect- films with narrowly specified properties is challenging. There is spare literature about thin films on commercial LTCC comparing different material systems or sintering techniques. For developing thin film sensors on multilayer circuits it is crucial to identify thin-film-compatible commercial LTCC material as well as the crucial surface properties. In this work we evaluate the thin-film capability of different LTCC surfaces.
The as-fired surfaces of free-sintered, constrained-sintered (sacrificial tape), and pressure-assisted sintered commercial LTCCs (DP951, CT708, CT800), as well as respective polished surfaces, were analyzed by tactile and optical roughness measurements and scanning electron microscopy. The thin-film capability of the LTCC surfaces was assessed by sheet resistance and temperature coefficient of resistance (TCR) of deposited Ni thin-film layers. Contrary to the expectations, no correlation between roughness and thin-film capability was found. Ni thin films on constrained sintered DP951 show the lowest sheet resistance and highest TCR within the experimental framework of the as-fired surfaces. The influence of surface morphology on the film properties is discussed.