A5091649158- High Temperature Alloys and Creep
- Advanced Materials Characterization Techniques
- Intermetallics and Advanced Alloy Properties
- High-Temperature Coating Behaviors
- Nuclear Materials and Properties
- Microstructure and Mechanical Properties of Steels
- Advanced materials and composites
- Microstructure and mechanical properties
- High Entropy Alloys Studies
- Metallurgy and Material Forming
- Hydrogen embrittlement and corrosion behaviors in metals
- earthquake and tectonic studies
- Metal Alloys Wear and Properties
- Geophysics and Sensor Technology
- Aluminum Alloys Composites Properties
- Seismic Waves and Analysis
- Metallic Glasses and Amorphous Alloys
- Seismology and Earthquake Studies
- Powder Metallurgy Techniques and Materials
- Additive Manufacturing Materials and Processes
- Seismic Imaging and Inversion Techniques
- Composite Material Mechanics
- Fatigue and fracture mechanics
- Earthquake Detection and Analysis
- Orthopaedic implants and arthroplasty
Friedrich-Alexander-Universität Erlangen-Nürnberg
2020-2024
RWTH Aachen University
2015-2017
Abstract Pushing the maximum service temperature of aircraft engines and industrial gas turbines is major pathway to improve their energy efficiency reduce CO 2 emissions. This mostly limited by capability key-component materials, including superalloys. In this alloy class, segregation elements facilitates plastic deformation generally considered cause softening during high-temperature deformation. Here, we show that segregation-assisted processes can also lead strengthening induce an...
Abstract Novel compositionally complex CoNiCr-based superalloys with excellent mechanical properties have been developed, which combine the multiprincipal element nature of high-entropy alloys precipitation strengthening in superalloys. A series advanced polycrystalline γ ′-strengthened superalloys, called CoWAlloys, varying contents Al, W, Ti, Ta, Mo, and Nb are investigated terms microstructure, thermophysical properties, yield, creep strength. The microstructure all CoWAlloys consists an...
Deformed quartz veins next (1-1.5m) to an exhumed pseudotachylyte-bearing (i.e. anciently seismic) fault within the Schobergruppe (Austroalpine Crystalline Complex, Eastern Alps) contain intensely kinked grains. In general, kinking requires presence of a planar mechanical anisotropy, e.g. multi-layered structure with regular periodic alternation thin weakly bounded layers (or high viscosity interleaved low ones) such as in minerals strong cleavage, micas or industrial metallic...
Abstract The creep resistance of single-crystalline Ni-base superalloys at elevated temperatures depends among others on solid solution strengthening the γ -matrix. To study influence various strengtheners mechanical properties, a series with same content different alloying elements (Ir, Mo, Re, Rh, Ru, W) or element combinations (MoW, ReMo, ReW) was investigated. Nanoindentation measurements were performed to correlate partitioning behavior hardness individual phases. lowest ′/ -hardness...
Abstract The creep strength of single-crystalline Co-based superalloys was found to be comparable first-generation Ni-base superalloys. However, considerable shearing the γ ′ precipitates observed in early stages. To determine strengthening contribution Ta-containing ′-Co 3 (Al,W) precipitates, several Co-Al-W-Ta determined as a function volume fraction at 1223 K (950 °C) and stress levels between 25 600 MPa. Employing Lagneborg–Bergman–Reppich (LBR) approach, it is that increases...
The anomalous yielding behavior known from Ni3Al or Ni-base superalloys is explained by the formation of immobile dislocation configurations via cross-slip leading superpartial anti-phase boundary-coupled pairs. A systematic investigation a single-crystalline Co-11Ti-15Cr superalloy transmission electron microscopy revealed absence similar sessile during initial stage. Shearing γ' precipitates superlattice stacking fault dominant deformation mechanism at peak temperature. Furthermore, high...
Abstract The deformation mechanisms operating in superalloys depend on different parameters such as composition, temperature and rate. So far, the transition from shearing by APB-coupled dislocations to under formation of stacking faults has been studied exclusively a function but not strain Therefore, interrupted compression tests with rates between 10 –3 s −1 –5 were performed single-crystalline CoNi-base superalloy ERBOCo-4 at 850 °C. evolution defect structures analyzed conventional...
Abstract The γ′ volume fraction is a key parameter in precipitation-strengthened Co- and Ni-base superalloys mainly determines the alloys’ properties. However, systematic studies with varying fractions are rare influence on thermal expansion has not been studied detail. Therefore, series of six Ta-containing Co-based alloys was designed compositions γ – tie-line, where changes systematically. During solidification, Laves (C14-type) µ (D8 5 -type) phases formed high levels W Ta. Single-phase...
Abstract In nickel-based superalloys, the lattice misfit between γ and ′ phases propensity to TCP phase formation at service temperatures critically influence microstructural evolution that takes place hence resultant mechanical properties. this work, misfits of a series highly alloyed Ru-containing 4th generation Ni-base superalloys are investigated by in situ X-ray diffraction (XRD) high temperature. While values all alloys range − 0.3 1.3 pct room temperature, they show an atypical...
Abstract Recent studies revealed the excellent high temperature properties of polycrystalline CoNi-base superalloys. However, their underlying deformation behavior has been reported only scarcely so far. In this work, mechanisms four compositionally complex superalloys with slightly varying chemical compositions were investigated by compression and creep experiments at temperatures between 750 °C 850 strain-rates 10 –3 –8 s −1 . two (Ta + Ti)-rich alloys, a transition mechanism from shearing...
The defect evolution associated with an anomalous work hardening behavior of a single crystalline quaternary Co-Al-W-Ta superalloy at 950 °C was investigated by transmission electron microscopy. As plastic deformation is initially confined to the γ matrix channels, plateau arises in stress-strain curve after yielding. At about 1% strain, extensive shearing γ′ precipitates under superlattice stacking fault formation occurs leading extreme rates up 12 GPa and total increase stress 200 MPa....
Understanding the influence of γ′ and secondary-phase fractions on mechanical properties superalloys is very important to optimize these high-strength materials. So far, this has not been systematically investigated for novel class Co-based superalloys. In study, a Co–Al–W–Ta model alloy series was designed with compositions γ/γ′ tie-line an increasing volume fraction up 70% after heat treatment at 900 °C, while few alloys are unexpectedly out two-phase region additional secondary phase 15%....
Recognition of seismically induced microstructures is important to unravel the different deformation processes during seismic cycles, especially at base upper crust where many earthquakes nucleate. Deformed quartz veins related a strike-slip shear zone within Schobergruppe (Austroalpine Crystalline Complex, Eastern Alps) contain intense kinking in elongated grains. The kink band boundaries are inclined into general dextral sense shear. Cathodoluminescence (CL) images reveal that entire thin...