5 Werkstofftechnik
Filtern
Dokumenttyp
- Zeitschriftenartikel (43)
- Vortrag (37)
- Beitrag zu einem Tagungsband (9)
- Forschungsdatensatz (3)
- Buchkapitel (2)
- Posterpräsentation (2)
- Dissertation (1)
Sprache
- Englisch (97) (entfernen)
Schlagworte
- CALPHAD (9)
- Nickel-base superalloys (8)
- Creep (7)
- Fatigue (7)
- Crack growth (6)
- Crystal plasticity (6)
- Additive manufacturing (5)
- Anisotropy (5)
- Microstructure (5)
- Thermomechanical fatigue (5)
- Crack tip opening displacement (4)
- Finite element analysis (4)
- Microstrucrue Design (4)
- Microstructure Design (4)
- Scale-bridging (4)
- Virtual experiments (4)
- Additive Manufacturing (3)
- Concrete (3)
- Crack propagation (3)
- Dislocation (3)
- EBSD (3)
- Ferritic-martensitic steels (3)
- Fracture mechanics (3)
- Grain boundary engineering (3)
- HIP (3)
- LCF (3)
- Low cycle fatigue (3)
- Phase-field (3)
- Phase-field simulation (3)
- Residual stress (3)
- Single-crystals (3)
- Viscoplasticity (3)
- Ageing (2)
- Characterization (2)
- Continnum damage model (2)
- Cyclic softening (2)
- Damage (2)
- Density-based Phase-Field Modelling (2)
- Density-based Thermodynamics (2)
- Density-based model (2)
- Densty-based Thermodynamics (2)
- Diffusion (2)
- Distribution function (2)
- Elasticity (2)
- Environmental stress cracking (ESC) (2)
- Environmentally assisted cracking (2)
- Grain boundaries (2)
- Machine Learning (2)
- Mass transport (2)
- Materials Modelling (2)
- Micromechanical model (2)
- Microstructural characterization (2)
- Monte-Carlo Simulation (2)
- Notches (2)
- Ontology (2)
- P92 (2)
- Phase-Field Simulations (2)
- Refractory high entropy alloys (2)
- Safety assessment (2)
- Scanning electron microscopy (2)
- Simulation (2)
- Simulation of concrete (2)
- Single-Crystal (2)
- Steels (2)
- Superalloys (2)
- Thermodynamics (2)
- Transmission electron microscopy (2)
- Transmission electron microscopy (TEM) (2)
- Under cyclic loading (2)
- Weibull Distribution (2)
- 9-12% Cr ferritic-martensitic steels (1)
- 9-12%Cr steel (1)
- AGIL (1)
- AM (1)
- Accelerated integration scheme (1)
- Accelerated temporal integration (1)
- Additive Fertigung (1)
- Adiabatic shear bands (1)
- Aging (1)
- Al alloys (1)
- Al-Cu alloy (1)
- Alloy Safety (1)
- Alloy design (1)
- Alloy microstructure (1)
- Alloys' Safety (1)
- Atomistic Simulation (1)
- Austenitischer Stahl (1)
- Automated finite element analysis (1)
- Automatische Finite Element Simulation (1)
- Brittle fracture (1)
- Burst (1)
- Burst test (1)
- CALPHAD database analysis (1)
- Chemically complex alloy (1)
- Chemo-mechanical coupling (1)
- Co-segregation (1)
- Composite pressure vessels (1)
- Contact mechanics (1)
- Creep anisotropy (1)
- Creep-fatigue (1)
- Crystal Defects (1)
- Crystal Plasticity Modelling (1)
- Cycle jump (1)
- Cyclic loading (1)
- Cyclic oxidation (1)
- Data Fusion (1)
- Data Management (1)
- Data Structures (1)
- Data structure (1)
- Defects engineering (1)
- Defects phase diagram (1)
- Defects thermodynamics (1)
- Deformation mechanisms (1)
- Degradation (1)
- Density-based Model (1)
- Density-based phase-field modelling (1)
- Differential scanning calorimetry (DSC) (1)
- Digital image correlation (1)
- Digitalization (1)
- Digitization (1)
- Directional grain growth (1)
- Dislocations (1)
- EXAFS (1)
- Elastic constants (1)
- Elastic energy (1)
- Electron backscattered diffraction (EBSD) (1)
- Electron microscopy (1)
- End of life (1)
- Environmental Stress Cracking (1)
- FCH JU (1)
- FNCT (1)
- Failure rate (1)
- Fatigue damage (1)
- Fe-Mn steels (1)
- Ferritic–martensitic steel (1)
- Finite-Elemente-Methode (1)
- Fourier series (1)
- Fracture surface analysis (1)
- Fracture surfaces (1)
- Full notch creep test (FNCT) (1)
- Full-Notch Creep Test (1)
- Full-Notch Creep Test (FNCT) (1)
- Full-notch creep test (1)
- Fullerite (1)
- Global stability criterion (1)
- Grade S960QL steel (1)
- Gradient-enhanced damage (1)
- Gradient-enhanced fatigue model (1)
- Grain Boundary (1)
- Grain Boundary Phase Diagram (1)
- Grain Boundary Segregation (1)
- Grain Boundary Spinodal (1)
- Grain boundary (1)
- Grain boundary phase diagram (1)
- Grain boundary structure (1)
- Grain boundary thermodynamics (1)
- Grain growth (1)
- Heat Treatments (1)
- Hertzian cracks (1)
- High Entropy Alloys (1)
- High-Entropy Alloys (1)
- High-Entropy Materials (1)
- High-entropy alloys (1)
- Horizon 2020 (1)
- Hot isostatic pressing (HIP) (1)
- Hydrogen (1)
- IN738LC (1)
- Inconel 718 (1)
- Incremental lifetime models (1)
- Interfacial Spinodal (1)
- Interfacial anisotropy (1)
- Knowledge Representation (1)
- Laser beam melting (LBM) (1)
- Laser powder bed fusion (1)
- Laser scanning microscopy (LSM) (1)
- Lattice distortions (1)
- Liquid Metal Embrittlement (1)
- Liquid-metal embrittlement (1)
- Long-term aging (1)
- Low strain (1)
- Machine learning (1)
- Material digital (1)
- Material modeling (1)
- Mean-field modelling (1)
- Mechanical anisotropy (1)
- Mechanical behavior (1)
- Mechanical testing (1)
- Mechanistic Modelling (1)
- Mehrskalenmodell (1)
- Microstructural evolution (1)
- Microstructure Evolution (1)
- Microstructure characterisation (1)
- Microstructure design (1)
- Microstructure evolution (1)
- Microstructure modification (1)
- Misfitting precipitate (1)
- Model (1)
- Modeling (1)
- Molecular Dynamics (1)
- Monte-Carlo-Analysis (1)
- Nanocrystalline alloys (1)
- Nanoindentation (1)
- Nanoparticles (1)
- Net zero (1)
- Nickel alloys (1)
- Nickel-base alloy (1)
- Nickel-base superalloy (1)
- Non-destructive testing (1)
- Optical criterion (1)
- Optical criterion of brittleness (1)
- Ordering (1)
- Ostwald ripening (1)
- P92 steels (1)
- PE-HD (1)
- Parametric modeling (1)
- Phase Diagram (1)
- Phase Diagrams (1)
- Phase field model (1)
- Phase stability (1)
- Phase-Field Simulation (1)
- Phase-field Simulation (1)
- Phase-field modelling (1)
- Physically based material model (1)
- Physics-informed Neural Network (1)
- Plasticity (1)
- Polyethylene (1)
- Polyethylene, PE-HD (1)
- Pore (1)
- Pores (1)
- Porosity (1)
- Power plant (1)
- Precipitate shape (1)
- Precipitation (1)
- Production scatter (1)
- Rafting (1)
- Refractory superalloys (1)
- Relaxation fatigue (1)
- Resistance spot welding (1)
- Rissausbreitung (1)
- S-phase (1)
- S355 steel sheet (1)
- Segregation Engineering (1)
- Segregation engineering (1)
- Selective laser melting (SLM) (1)
- Semantic Web Technologies (1)
- Short-range order (1)
- Single crystal superalloys (1)
- Spinodal Decomposition (1)
- Spinodal decomposition (1)
- Split Hopkinson bar (1)
- Strain energy (1)
- Superalloy (1)
- Surface-induced Melting (1)
- Symmetric dwell periods (1)
- TAHYA (1)
- TEM (1)
- Tempered Martensite Ferritic Steels (1)
- Tempered martensite ferritic steel (1)
- Tempered martensite ferritic steels (1)
- Tensile test (1)
- Tensile testing (1)
- Thermo-Mechanical Fatigue (1)
- Thermo-mechanical fatigue (1)
- Thermomechanische Ermüdung (1)
- Turbine disk (1)
- Vacancies (1)
- X-Ray Diffraction (1)
- γ″ phase (1)
- θ′ phase (1)
- θ′-(Al2Cu) precipitate phase (1)
Organisationseinheit der BAM
- 5.5 Materialmodellierung (97) (entfernen)
Paper des Monats
- ja (2)
Eingeladener Vortrag
- nein (37)
Virtual-lab-based determination of a macroscopic yield function for additively manufactured parts
(2019)
This work aims for a yield function description of additively manufactured parts of S316L steel at the continuum-mechanical macro-scale by means of so-called virtual experiments using a crystal plasticity (CP) model at meso-scale. Additively manufactured parts require the consideration of the specific process-related microstructure, which prevents this material to be macroscopically treated as isotropic, because of crystallographic as well as topological textures. From virtual experiments, yield loci under various loading conditions are simulated. The scale bridging from meso- to macro-scale is realised by the identification of the simulated yield loci as a modified anisotropic Barlat-type yield model representation.
Virtual-lab-based determination of a macroscopic yield function for additively manufactured parts
(2019)
This work aims for an yield function description of additively manufactured (AM) parts of S316L steel at the continuum-mechanical macro-scale by means of so-called virtual experiments using a crystal plasticity (CP) model at meso-scale. Additively manufactured parts require the consideration of the specific process-related microstructure, which prevents this material to be macroscopically treated as isotropic, because of crystallographic as well as topological textures.
EBSD/CT-Scans from in-house additively manufactured specimen extract the unique microstructural topology which is converted to a representative volume element (RVE) with grain structure and crystal orientations.
Crystal plasticity model parameters on this RVE are calibrated and validated by means of mechanical testing under different texture angles. From virtual experiments on this RVE, yield loci under various loading conditions are simulated. The scale bridging from meso- to macro-scale is realised by the identification of the simulated yield loci as a modified anisotropic Barlat-type yield model representation.
Virtual-lab-based determination of a macroscopic yield function for additively manufactured parts
(2018)
This work presents a method for the yield function determination of additively manufactured parts of S316L steel. A crystal plasticity model is calibrated with test results and used afterwards to perform so-called virtual experiments, that account for the specific process-related microstructure including crystallographic and morphological textures. These simulations are undertaken on a representative volume element (RVE), that is generated from EBSD/CT-Scans on in-house additively manufactured specimen, considering grain structure and crystal orientations. The results of the virtual experiments are used to determine an anisotropic Barlat yield function, that can be used in a macroscopical continuum-sense afterwards. This scale-bridging approach enables the calculation of large-scale parts, that would be numerically too expensive to be simulated by a crystal plasticity model.
Virtual-lab-based determination of a macroscopic yield function for additively manufactured parts
(2018)
This work presents a method for the yield function determination of additively manufactured parts of S316L steel. A crystal plasticity model is calibrated with test results and used afterwards to perform so-called virtual experiments, that account for the specific process-related microstructure including crystallographic and morphological textures. These simulations are undertaken on a representative volume element (RVE), that is generated from EBSD/CT-Scans on in-house additively manufactured specimen, considering grain structure and crystal orientations. The results of the virtual experiments are used to determine an anisotropic Barlat yield function, that can be used in a macroscopical continuum-sense afterwards. This scale-bridging approach enables the calculation of large-scale parts, that would be numerically too expensive to be simulated by a crystal plasticity model.
Results of an extended TMF test program on grade P92 steel in the temperature range of 620 °C - 300 °C, comprising in-phase (IP) and out-of-phase (OP) tests, partly performed with symmetric dwells at Tmax/Tmin, are presented. In contrast to previous studies, the low-strain regime is also illuminated, which approaches flexible operation in a power plant with start/stop cycles. At all strain amplitudes, the material performance is characterized by continuous cyclic softening, which is retarded in tests at lower strains but reaches similar magnitudes in the course of testing. In the investigated temperature range, the phase angle does not affect fatigue life in continuous experiments, whereas the IP condition is more detrimental in tests with dwells. Fractographic analyses indicate creep-dominated and fatigue-dominated damage for IP and OP, respectively. Analyses of the (micro)hardness distribution in the tested specimens suggest an enhanced microstructural softening in tests with dwell times for the low- but not for the high-strain regime. To rationalize the obtained fatigue data, the fracture-mechanics-based D_TMF concept, which was developed for TMF life assessment of ductile alloys, was applied. It is found that the D_TMF parameter correlates well with the measured fatigue lives, suggesting that subcritical growth of cracks (with sizes from a few microns to a few millimeters) governs failure in the investigated range of strain amplitudes.
Detailed microstructural characterization of the AlMo0.5NbTa0.5TiZr refractory high entropy superalloy in the as-cast state is reported for first time and compared with the state annealed at 1400 oC for 24 h. The former shows a dendritic structure, with a mixture of A2/B2 phases < 20 nm in both the dendritic and interdendritic regions. A mostly amorphous phase, rich in Al and Zr, is found within the interdendritic region. The annealed state reproduced the combination of A2/B2/Al-Zr-rich phases reported previously. Calculations from two relevant ThermoCalc databases were compared with the experimental results. Equilibrium calculations were compared with results for the annealed alloy, whereas solidification paths calculated using Scheil-Gulliver model were used for comparison with the as-cast alloy. A previously hypothesized spinodal decomposition during cooling as the mechanism responsible for the patterned A2/B2 microstructure is confirmed via the CALPHAD calculations, pointing to its use as an efficient design tool for such alloys. Finally, the comparison between the experimental and computational findings allowed better understanding the solidification path and equilibrium stability of this alloy, giving a base to make better decisions on the field of new refractory superalloy design.
For more than half a century, spinodal decomposition has been a key phenomenon in considering the formation of secondary phases in alloys. The most prominent aspect of the spinodal phenomenon is the lack of an energy barrier on its transformation pathway, offering an alternative to the nucleation and growth mechanism. The classical description of spinodal decomposition often neglects the influence of defects, such as grain boundaries, on the transformation because the innate ability for like-atoms to cluster is assumed to lead the process. Nevertheless, in nanocrystalline alloys, with a high population of grain boundaries with diverse characters, the structurally heterogeneous landscape can greatly influence the chemical decomposition behavior. Combining atom-probe tomography, precession electron diffraction and density-based phase-field simulations, we address how grain boundaries contribute to the temporal evolution of chemical decomposition within the miscibility gap of a Pt-Au nanocrystalline system. We found that grain boundaries can actually have their own miscibility gaps profoundly altering the spinodal decomposition in nanocrystalline alloys. A complex realm of multiple interfacial states, ranging from competitive grain boundary segregation to barrier-free low-dimensional interfacial decomposition, occurs with a dependency upon the grain boundary character.
Simulation of the θ′ Precipitation Process with Interfacial Anisotropy Effects in Al-Cu Alloys
(2021)
The effects of anisotropic interfacial properties and heterogeneous elasticity on the growth and ripening of plate-like θ′-phase (Al2Cu) in Al-1.69 at.% Cu alloy are studied. Multi-phase-field simulations are conducted and discussed in comparison with aging experiments. The precipitate/matrix interface is considered to be anisotropic in terms of its energy and mobility. We find that the additional incorporation of an anisotropic interfacial mobility in conjunction with the elastic anisotropy result in substantially larger aspect ratios of the precipitates closer to the experimental observations. The anisotropy of the interfacial energy shows comparably small effect on the precipitate’s aspect ratio but changes the interface’s shape at the rim. The effect of the chemo-mechanical coupling, i.e., the composition dependence of the elastic constants, is studied as well. We show that the inverse ripening phenomenon, recently evidenced for δ’ precipitates in Al-Li alloys (Park et al. Sci. Rep. 2019, 9, 3981), does not establish for the θ′ precipitates. This is because of the anisotropic stress fields built around the θ′ precipitates, stemming from the precipitate’s shape and the interaction among different variants of the θ′ precipitate, that disturb the chemo-mechanical effects. These results show that the chemo-mechanical effects on the precipitation ripening strongly depend on the degree of sphericity and elastic isotropy of the precipitate and matrix phases.
Single crystal superalloys usually contain pores of sizes 5-10 micro-m after casting and heat treatment. These pores can be reduced under compression by combined creep and diffusion in a subsequent treatment called Hot Isostatic Pressing (HIP). The paper presents a methodology to simulate pore shrinkage under HIP conditions in two dimensions (2D).
At the scale of the pores, which is also the scale of the sub-grains (<50 micro-m) the dislocation sources cannot be assumed to be homogeneously distributed. Thus, the applicability of classical crystal plasticity is questionable. In this case, the transport of dislocations under an applied stress from the location where they are nucleated must be explicitly modelled. This is done by solving the transport equations for the dislocation densities and the elasticity equations in 2D. The dislocations are assumed to be nucleated at Low Angle Boundaries. They glide or climb through the sub-grains with a stress dependent velocity.
The transport equations are solved by the Flux-Corrected Transport method, which belongs to the predictor-corrector class of algorithms. In the first step, an artificial diffusion is introduced, which suppresses spurious oscillations of the solution. In a second step, the solution is corrected in such a way that no additional extremes appear and that the extremes do not grow. The algorithm is validated by simulating the transport of simple distributions with a constant velocity field.
With the dislocation velocities and the computed dislocation densities, the inelastic shear rate at the slip system level is computed by integrating the Orowan equation. In the 2D-setting, three slip systems are considered. The contributions of these slip systems are summed up to obtain the total inelastic strain rate. Dislocation glide and climb and the coupling of climb with vacancies diffusion are considered.
The resolution of the equilibrium equations from the inelastic strains turned out to be prone to numerical instabilities. As an alternative, the stresses are directly computed from the distribution of geometrically necessary dislocations following the method presented in. The resulting boundary value problem is solved by the Least-Square Finite Element method.
Examples of simulations are presented for a representative region under creep tension and for a pore shrinking under external pressure.