A5048275594- Quasicrystal Structures and Properties
- Microstructure and mechanical properties
- X-ray Diffraction in Crystallography
- High Entropy Alloys Studies
- High-Temperature Coating Behaviors
- Intermetallics and Advanced Alloy Properties
- Mineralogy and Gemology Studies
- Metallic Glasses and Amorphous Alloys
- Aluminum Alloy Microstructure Properties
- Advanced Materials Characterization Techniques
- Metallurgical and Alloy Processes
- Rare-earth and actinide compounds
- Aluminum Alloys Composites Properties
- Magnesium Alloys: Properties and Applications
- Magnetic properties of thin films
- Theoretical and Computational Physics
- Hydrogen Storage and Materials
- Thermodynamic and Structural Properties of Metals and Alloys
- Additive Manufacturing Materials and Processes
- Nanocluster Synthesis and Applications
- Ammonia Synthesis and Nitrogen Reduction
- Metal and Thin Film Mechanics
- Material Dynamics and Properties
- Magnetic Properties of Alloys
- Surface and Thin Film Phenomena
Forschungszentrum Jülich
2016-2025
Ernst Ruska Centre
2015-2025
Stadtwerke Jülich (Germany)
2009
Kranj School Centre
2008
Institute of Mathematics, Physics, and Mechanics
2008
Science et Ingénierie des Matériaux et Procédés
2007
Scientific Research and Development (Germany)
1998
Max Planck Institute of Microstructure Physics
1997
FH Aachen
1995
RWTH Aachen University
1994
High-entropy alloys (HEAs) are multicomponent mixtures of elements in similar concentrations, where the high entropy mixing can stabilize disordered solid-solution phases with simple structures like a body-centered cubic or face-centered cubic, competition ordered crystalline intermetallic phases. We have synthesized an HEA composition Ta34Nb33Hf8Zr14Ti11 (in at. %), which possesses average structure lattice parameter a=3.36 Å. The measurements electrical resistivity, magnetization and...
We report on the discovery of a high-entropy alloy with hexagonal crystal structure. Equiatomic samples in system Ho-Dy-Y-Gd-Tb were found to solidify as homogeneous single-phase alloys. The results our electron diffraction investigations and high-resolution scanning transmission microscopy are consistent Mg-type possibility alloys other systems is discussed.
Bulk samples of Pd41Ni10Cu29P20 glass were tested at constant true stress (20–636MPa) in compression 550, 555, and 565K to study the transition from steady-state creep low deformation-induced softening high stress. In high-stress regime strongly accelerating was observed. All deformation homogeneous. The activation volume 106Å3. isoconfigurational energy 9.03±0.64eV. disordering rate is proportional applied power density (stress×strain rate). process inefficient production free volume.
Rare earth based equimolar Ho-Dy-Y-Gd-Tb hexagonal high-entropy alloy (HEA) is a prototype of an ideal HEA, stabilized by the entropy mixing at any temperature with random elements on close-packed lattice. In order to determine intrinsic properties HEA characterized enormous chemical (substitutional) disorder weakly distorted simple lattice, we have performed measurements its magnetic and electrical response specific heat. The results show that exhibits rich complex field-temperature $(H,T)$...
For the first time quasicrystal surfaces produced by in situ cleavage ultrahigh vacuum have been investigated scanning tunneling microscopy. Twofold and fivefold of icosahedral AlPdMn single quasicrystals studied. The were found to be rough. Their structure is determined cluster aggregates formed on basis an elementary whose contrast behavior diameter about 1 nm point Mackay-type cluster. Crack propagation occurs along zones lower strength between clusters. This supports approach structure.
Abstract High-entropy alloys are multicomponent metallic materials currently attracting high research interest. They display a unique combination of chemical disorder and crystalline long-range order due to their attractive properties promising candidates for technological application. Many high-entropy possess surprisingly strength, occasionally in with ductility low density. The mechanisms effecting these mechanical not understood. This study addresses the deformation mechanism Al 28 Co 20...
We determined the entropy of high alloys by investigating single-crystalline nickel and five alloys: two fcc-alloys, bcc-alloys one hcp-alloy. Since configurational these single-phase differs from using a base element, it is important to quantify entropy. Using differential scanning calorimetry, cp-measurements are carried out −170 °C materials’ solidus temperatures TS. From experiments, we thermal compared for each studied alloys. applied rule mixture predict molar heat capacities at room...
The influence of chemical composition changes on the room temperature mechanical properties in binary Ca33Al67 C15 CaAl2 Laves phase were investigated two ternary alloys with off-stoichiometric compositions 5.7 at.% Mg substitution (Ca33Al61Mg6) and 10.8 3.0 Ca (Ca36Al53Mg11) compared to stoichiometric (Ca33Al67) composition. Cubic Ca-Al-Mg phases multiple crystallographic orientations characterised deformed using nanoindentation. hardness indentation modulus measured be 4.1 ± 0.3 GPa 71.3...
Abstract The plastic deformation of icosahedral Al-Pd-Mn single quasicrystals has been studied by in situ straining experiments a high-voltage electron microscope at elevated temperatures. results provide the first direct evidence for dislocation motion quasicrystals. velocity, an applied stress 390 MPa, was determined as 7×10−7ms−1. It found that takes place planes which are perpendicular to threefold and fivefold lattice directions.
The mechanical properties of high-entropy alloys (HEAs) are still not deeply understood. Detailed knowledge the strengthening mechanism, especially, atomistic origin solid solution hardening and its interplay with dislocation plasticity is needed. Here, we report on glide behavior a FeCoCrNiMn face-centered cubic (FCC) single crystal studied by in situ deformation transmission electron microscope (TEM). threshold shear stress for thin foil measured from curvature as exceeding 400 MPa....
Abstract Al[sbnd]Pd[sbnd]Mn single-quasicrystals have been plastically deformed at temperatures between 730 and 800°C up to different strain values analysed in the transmission electron microscope. Dislocations were created during deformation. The dislocation density ranged 1·7 × 107 cm−2 undeformed samples 7·8 108cm−2in material 732°C. Six-dimensional Burgers vectors determined employing convergent-beam diffraction technique. 87% of these oriented parallel twofold directions...
We have investigated the plastic deformation properties of single-phase Zr–Nb–Ti–Ta–Hf high-entropy alloys from room temperature (RT) up to 300 °C. Uniaxial tests at a constant strain rate 10−4 s−1 were performed, including incremental such as stress relaxations, strain-rate changes, and changes in order determine thermodynamic activation parameters process. The microstructure deformed samples was characterized by transmission electron microscopy. strength phase is not high values frequently...
The electrical and thermal transport properties of a single-phase quasicrystalline material composition Al70.8Pd20.9Mn8.3 have been measured as function temperature (T) over range 10 K<T<320 K. following room-temperature values were found: conductivity [640 (Ω cm)−1], Seebeck coefficient (85 μV/K), (1.6 W/m K). As the was decreased from room temperature, undergoing minimum at T≈50 K after which it increased slightly monotonically. with exhibited broad plateau region between 50...
Abstract Plastic deformation experiments were performed on icosahedral Al-Pd-Mn single-quasicrystals to determine the thermodynamic activation parameters of process. The stress exponent and strain-rate sensitivity flow obtained by means relaxation experiments. enthalpy process was measured temperature change In range from 730 800°C a nearly constant value about 7 eV determined.
High-Entropy Alloys (HEAs) are a new family of crystalline random alloys with four or more elements in simple unit cell, at the forefront materials research for their exceptional mechanical properties. Their strong chemical disorder leads to mass and force-constant fluctuations which expected strongly reduce phonon lifetime, responsible thermal transport, similarly glasses. Still, long range order would associate HEAs crystals complex disordered cell. These two families materials, however,...
A single crystal of the ${\ensuremath{\xi}}^{\ensuremath{'}}$-AlPdMn phase was plastically deformed in a three-point bending geometry. The shows periodic lattice phason lines. In high-resolution electron microscopy (HREM) study novel dislocation type, termed metadislocation, observed for first time. magnitude its Burgers vector is 171 \AA{}. At core metadislocation ${\ensuremath{\xi}}^{\ensuremath{'}}$ structure found. For time and were determined by HREM. direction it equivalent to most...