5.0 Abteilungsleitung und andere
Filtern
Dokumenttyp
- Zeitschriftenartikel (40)
- Vortrag (23)
- Beitrag zu einem Tagungsband (3)
- Buchkapitel (1)
- Sonstiges (1)
- Posterpräsentation (1)
- Forschungsdatensatz (1)
Schlagworte
- Additive manufacturing (7)
- Metallic glasses (6)
- Oxidation (6)
- Corrosion (5)
- Neutron diffraction (5)
- Residual stress (5)
- Metallic glass (4)
- Nanoindentation (4)
- Additive Manufacturing (3)
- Diffraction (3)
- Glass (3)
- IN718 (3)
- Plasticity (3)
- Residual Stresses (3)
- Selective Laser Melting (3)
- Selective laser melting (3)
- Spectroscopy (3)
- Transmission electron microscopy (3)
- Additive Fertigung (2)
- Dehnungsfehler (2)
- Digitalisierung (2)
- Ductile iron (2)
- Elastic microstructure (2)
- Extensometer (2)
- High Entropy Alloys (2)
- High entropy alloys (2)
- High temperature (2)
- High temperature corrosion (2)
- In situ (2)
- Mechanical properties (2)
- Microstructure and texture (2)
- Molecular dynamics (2)
- Niobium alloying (2)
- Ressidual stress (2)
- SIMS (2)
- SLM (2)
- Shape-memory alloys (2)
- Shear bands (2)
- Sulfidation (2)
- Temperaturschwankungen (2)
- X-ray absorption spectroscopy (2)
- XRD (2)
- 150 Years (1)
- 4-Dimensional scanning transmission (1)
- Abrasion (1)
- Active thermography (1)
- Adolf Martens (1)
- Advanced high strength steels (1)
- Aging (1)
- Al-Cu binary alloy system (1)
- Alloy (1)
- Aluminium alloys (1)
- Bond energy (1)
- Bulk metallic glasses (1)
- Carbidic austempered ductile iron (1)
- Chalcogenides (1)
- Chemically complex alloys (1)
- Coordinate measurement machine (1)
- Copper vacancies (1)
- CrCoNi (1)
- CrMnFeCoNi (1)
- Creation-relaxation algorithm (1)
- Cryogenic cycling (1)
- Crystal lattice (1)
- Crystallographic texture (1)
- Deposition microstructure (1)
- Dislocation avalanches (1)
- Druckgasspeicher (1)
- Dynamic recrystallization (1)
- EDXRD (1)
- EXAFS (1)
- Electron back-scattered diffraction (1)
- Electron microscopy, transmission (1)
- Energiespeicherung (1)
- Epitaxial films (1)
- Equilibrium relaxation (1)
- Experimental and numerical techniques (1)
- Explosionsschutz (1)
- Ferritic Alloys (1)
- Fiber (1)
- Fracture surface energy (1)
- Fracture toughness (1)
- Fraktographie (1)
- Friction stir processing (1)
- Gasdetektion (1)
- Gassensorik (1)
- Gasturbinen (1)
- Glass transition (1)
- Glasspeicher (1)
- Heißgaskorrosion (1)
- Hierarchical microstructure Premartensite (1)
- High Temperature Corrosion (1)
- High entropy alloy (1)
- High temperature oxidation (1)
- High-entropy alloy (1)
- High-temperature corrosion (1)
- Hochentropielegierungen (1)
- In situ thermal-annealing experiment (1)
- In-situ (1)
- In718 (1)
- Incipient plasticity (1)
- Intermetallic (1)
- Intermittent microplasticity (1)
- Iron (1)
- Korrosion (1)
- Kunststoffe (1)
- Laboratory X-ray diffraction (1)
- Laser (1)
- Laser powder bed fusion (1)
- Lattice distortions (1)
- Lindemann criterion (1)
- Liquid metal embrittlement (1)
- Magnetic shape memory (1)
- Martensitic structure (1)
- Martensitic transformation (1)
- Materialwissenschaft (1)
- Medium Entropy Alloys (1)
- Medium entropy alloys (1)
- Metallic materials (1)
- Microplastic stress (1)
- Microstructural changes of a Fe Si alloy (1)
- Microstructural evolution (1)
- Mini-UAV (1)
- Mixed conductors (1)
- Mixed gas atmosphere (1)
- Mn-oxides (1)
- Nano-composite (1)
- Nanocrystalline structure (1)
- NiMaGa (1)
- Nickel-based superalloys (1)
- Non-serrated inhomogeneous flow (1)
- Nucleation tendency (1)
- Ontologien (1)
- Optic (1)
- Oxides (1)
- Physical aging (1)
- Plastic deformation (1)
- Plattform Material Digital (1)
- Polymer matrix composites (1)
- Powder diffraction (1)
- Power-to-Gas (1)
- Rejuvenation (1)
- Relaxation (1)
- Relaxation metallic glasses (1)
- Residual strains (1)
- Residual stresses (1)
- Risikoanalyse (1)
- SEM (1)
- SHM (1)
- Salzschmelzen (1)
- Scale-dependent behavior (1)
- Scan strategies (1)
- Schwingbrüche (1)
- Shear (1)
- Shear strain (1)
- Shear-band cavitation (1)
- Shear-band structure (1)
- Short-range order (1)
- Size effect (1)
- Slip localization (1)
- Slip-rolling (1)
- Small-scale (1)
- Split-vacancy defect complexes (1)
- Steel (1)
- Structural dynamics (1)
- Structured heating (1)
- Subsurface defects (1)
- Sulfiding (1)
- Sulphidation (1)
- Superlegierungen (1)
- Support configurations (1)
- Synchrotron X-ray diffraction (1)
- Thermal expansion (1)
- Thin films (1)
- Tribologie (1)
- Twinning (1)
- VCSEL (1)
- Vernetzung (1)
- Virtueller Materialdatenraum (1)
- Viscosity (1)
- Wasserstoff (1)
- Wasserstofferzeugung (1)
- Werkstoffdaten (1)
- Wärmespeicher (1)
- XPCS (1)
- arbidic austempered ductile iron (1)
- electron microscopy (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (70)
- 5.0 Abteilungsleitung und andere (70)
- 9 Komponentensicherheit (18)
- 8 Zerstörungsfreie Prüfung (15)
- 5.1 Mikrostruktur Design und Degradation (11)
- 8.5 Röntgenbildgebung (11)
- 9.4 Integrität von Schweißverbindungen (11)
- 6 Materialchemie (4)
- 8.0 Abteilungsleitung und andere (3)
- 9.2 Versuchsanlagen und Prüftechnik (3)
Eingeladener Vortrag
- nein (23)
We report on the mechanical properties of Cu–Nb alloys produced by combinatorial magnetron sputtering.
Depending on the composition, the microstructure is either fully amorphous (~30–65 at.% Cu), a dispersion of Cu crystallites in an amorphous matrix (~70 at.%), or a dominant crystalline phase with separated nanoscale amorphous zones (~80 at.% Cu). Nanomechanical probing of the different microstructures reveals that the hardness of the fully amorphous alloy is much higher than a rule of mixture would predict. We further demonstrate a remarkable tunability of the resistance to plastic flow, ranging from ca. 9 GPa in the amorphous regime to ca. 2 GPa in the fully crystalline regime. We rationalize these findings based on fundamental structural considerations, thereby highlighting the vast structure-property design space that this otherwise immiscible binary alloy provides.
Mit der Initiative MaterialDigital fördert das BMBF seit dem letzten Jahr ein wichtiges Instrument zur Digitalisierung der Materialwissenschaft und Werkstofftechnik in Deutschland. In der ersten Phase dieser Initiative wird seit Juli 2019 die Plattform MaterialDigital von einem Konsortium aufgestellt. Ziel dieser Plattform ist der Aufbau eines virtuellen Materialdatenraums, um zusammen mit allen Interessenten die Systematisierung des Umgangs mit Werkstoffdaten voranzutreiben. In einer zweiten Phase werden akademische F&E-Projekte voraussichtlich Anfang 2021 gefördert. In jedem dieser Projekte wird an einer konkreten Fragestellung das Themenfeld „Digitalisierung der Materialwissenschaft und Werkstofftechnik“ adressiert und multidisziplinär bearbeitet. In einer dritten Phase werden im Rahmen industriegeführter vorwettbewerblicher Verbundprojekte mit der gleichen Zielsetzung gefördert.
Im Rahmen der DGM/DVM AG Fraktographie wird an der BAM eine fraktographische online-Datenbank aufgebaut. Während von metallischen Werkstoffen viele Beispiele vorliegen, die auch gut verstanden sind, sind die Brüche von Kunststoffen bislang weniger prominent vertreten. Eine teils ungeklärte Frage ist, in welcher Form sich an Kunststoffen klassische Schwingbrüche nachweisen lassen, wie sie von metallischen Werkstoffen bekannt sind. Der Vortrag zeigt einige Beispiele im Detail und stellt diese zur Diskussion.
Influence of deposition hatch length on residual stress in selective laser melted Inconel 718
(2018)
The present study aims to evaluate the bulk residual stresses in SLM parts by using neutron diffraction measurements performed at E3 line -BER II neutron reactor- of Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. Together with microstructure characterization and distortion measurements, it is possible to describe the stress state throughout the whole sample. The sample was measured in as-build condition (on a build plate) and after releasing from the build plate. The used material is the nickel based superalloy 718. This alloy is widely used in aerospace and chemical industries due to its superior corrosion and heat resistant properties.
Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component. The normal and transversal component exhibits a rather compressive behavior while the longitudinal was tensile in the center part of the sample and became compressive towards the tip. As expected, the absolute values of all stress components decreased after releasing the sample from the building plate. A surface scan utilizing a coordinate-measuring machine (CMM) allowed us to present top surface distortion before and after releasing. The top surface showed a distortion around ±80µm after releasing. Microstructure evolution in the scanning-building cross-section is largely dominated by columnar grains. In addition, many small random orientated grains are prominent in the regions of a laser overlap during SLM.
In summary, for the sample of superalloy 718 manufactured by SLM, a small distortion occurred when removing the sample from the build plate whereby the residual stress state decreases. Moreover, the observed columnar grains in the building direction could give a reason for the lowest stress values in that normal direction. However, the most important parameter controlling the residual stresses is the temperature gradient. Hence, future investigations are planned for a different scan strategy to distribute the laser impact in a more homogenous manner.
Subjecting metallic glasses repeatedly to liquid nitrogen temperature has become a popular method to homogeneously rejuvenate the material. Here we reveal the atomic-scale structural dynamics using in- situ x-ray photon correlation spectroscopy (XPCS) during and after cryogenic cycling of a Zr-based metallic glass in two structural states (plate and ribbon). Heterogeneous structural dynamics is observed at 300 K that changes to monotonic aging at 78 K. It is found that cryogenic cycling homogenizes the relaxation time distribution. This effect is much more pronounced in the ribbon, which is the only structural state that rejuvenates upon cycling. We furthermore reveal how fast atomic-scale dynamics is correlated with longtime structural relaxation times irrespective of the structural state, and that the ribbon exhibits unexpected additional fast atomic-scale relaxation in comparison to the plate material. A structural picture emerges that points towards heterogeneities in the fictive temperature as a requirement for cryogenic energy storage.
Metallic glasses are known to have a remarkably robust yield strength, admitting Weibull moduli as high as for crystalline engineering alloys. However, their postyielding behavior is strongly varying, with large scatter in both flow stress levels and strains at failure. Using x-ray tomography, we reveal how a strain-dependent internal evolution of shear-band cavities underlies this unpredictable postyielding response.We demonstrate how macroscopic strain softening coincides with the first detection of internal shear-band cavitation. Cavity growth during plastic flow is found to follow a power law, which yields a fractal dimension and a roughness exponent in excellent agreement with self-similar surface properties obtained after fracture. These findings demonstrate how internal microcracking coexists with shear-band plasticity along the plastic part of a stress-strain curve, rationalizing the large variability of plastic flow behavior seen for metallic glasses.
How thermally activated structural excitations quantitatively mediate transport and microplasticity in a model binary glass at the microsecond timescale is revealed using atomistic simulation. These local excitations, involving a stringlike sequence of atomic displacements, admit a far-field shear-stress signature and underlie the transport of free-volume and bond geometry. Such transport is found to correspond to the Evolution of a disclination network describing the spatial connectivity of topologically distinct bonding environments, demonstrating the important role of geometrical frustration in both glass structure and its underlying dynamics.
Using the creation relaxation algorithm developed for the atomistic modeling of the high-dose irradiation limit of crystalline systems, we explore the limits of the structural rejuvenation of a highly excited model binary glass. This high-energy athermal amorphous structure exhibits a direct transition to homogeneous plastic flow and a microstructure that is largely insensitive to this flow, being characterized by a porous system-spanning network of minimally frustrated structural motifs. The observed homogeneous plasticity is mediated by the same string-like structural excitations, which mediate structural relaxation and microplasticity at finite temperature in more relaxed structures. This highly rejuvenated structural asymptote is not far from the structural state of regions, which have experienced athermal shear localization in more relaxed samples, suggesting an optimally rejuvenated glassy structure will always be limited by that produced by shear localization.
The impact of the microstructure of Fe-16Cr-0.2C on high-temperature oxidation – sulphidation in SO2
(2021)
This study elucidates the impact of the microstructure of Fe-16Cr-0.2C on oxide layer formation at 650 ◦C in Ar-0.5 % SO2. A cold-rolled and two heat-treated states of the alloy were exposed for up to 1000 h. The samples were characterised in detail from microstructural and chemical perspectives using scanning electron microscopy (SEM), X-ray diffraction (XRD) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The microstructural modification of the alloy by heat-treatment was advantageous. It was found that Cr-carbides support chromia formation and reduce sulphidation when their area fraction is low and diameter is small.
Extended X-ray absorption fine structure (EXAFS) conducted on an equiatomic MoNbTaW bcc medium-entropy alloy that was annealed at 2273 K reveals unexpectedly small 1st and 2nd shell element-specific lattice distortions. An experimental size-mismatch parameter, δexp, is determined to be ca. 50% lower than the corresponding calculated value. Around W, short-range order (SRO) preferring 4d elements in the 1st and 2nd shells persists. A Nb-W ordering is found, which is reminiscent of ordering emerging at lower temperatures in the B2(Mo,W;Ta,Nb)- and B32(Nb,W)-phases. With high-temperature ordering preferences in fcc also foreshadowing low-temperature phase, these findings suggest a general feature of high-temperature SRO.