5 Werkstofftechnik
Filtern
Erscheinungsjahr
- 2019 (31) (entfernen)
Dokumenttyp
- Posterpräsentation (31) (entfernen)
Referierte Publikation
- nein (31) (entfernen)
Schlagworte
- Glass (5)
- Degradation (3)
- Microstructure (3)
- Additive Manufacturing (2)
- Alloy 2618A (2)
- Coarsening (2)
- Corrosion (2)
- Crack growth (2)
- Fatigue (2)
- Oxidation (2)
- Transmission electron microscopy (2)
- Water content (2)
- 316L (1)
- 3D (1)
- 3D imaging (1)
- 5G (1)
- Additive manufacturing (1)
- Aggressive environment (1)
- Al-Cu-Li alloys (1)
- Anisotropy (1)
- Atomization (1)
- BTS (1)
- Brittle fracture (1)
- CALPHAD (1)
- CALPHAD databases analysis (1)
- Chemically Complex Alloy (1)
- Co-axial monitoring (1)
- Complex concentrated alloy (CCA) (1)
- Composite (1)
- Computed Tomography (1)
- Corrosion resistance (1)
- Crack Propagation (1)
- Crack healing (1)
- Crystal orientation (1)
- Crystal plasticity (1)
- Crystallization (1)
- DCB (1)
- DED-L (1)
- Dark-field transmission electron microscopy (DFTEM) (1)
- Destabilization (1)
- Diesel (1)
- Digital material representation (1)
- Diopside (1)
- Distributed fiber optic sensors (1)
- EBSD (1)
- Electromicroscopy (1)
- Environmental stress cracking (ESC) (1)
- FeCr- alloys (1)
- Fracture surface analysis (1)
- Fraktografie (1)
- Fresnoit (1)
- Full-Notch Creep Test (FNCT) (1)
- Glass ceramic (1)
- Glass fiber reinforced polymers (1)
- Glass matrix composite (1)
- Glass-ceramic (1)
- HDPE Sorption (1)
- Hardness (1)
- High Temperature Testing (1)
- High temperature (1)
- High temperature corrosion (1)
- IR (1)
- Inconel 686 (1)
- Internal friction (1)
- Kavitation (1)
- LMD (1)
- LTCC multilayer (1)
- Laser Beam Melting (1)
- Laser cladding (1)
- Lightweight materials (1)
- Low Cycle Fatigue (1)
- Machine Learning (1)
- Metal powder characterization (1)
- Metrology (1)
- Microstructure analysis (1)
- Mikrostruktur (1)
- Modeling (1)
- NMR (1)
- Nanoparticles (1)
- Optical criterion (1)
- Orientation (1)
- Polyethylene, PE-HD (1)
- Polymer (1)
- Process Monitoring (1)
- Röntgenbeugung (1)
- Röntgenrefraktion (1)
- Salt melt (1)
- Sandwich (1)
- Scale-bridging (1)
- Schadensanalyse (1)
- Selective laser melting (1)
- Silver glass paste (1)
- Sintering (1)
- Slurry (1)
- Soda-lime silicate glass (1)
- Sulfidation (1)
- Surface crystallization (1)
- Synthetic air (1)
- Tensile Properties (1)
- Thermodynamic analysis (1)
- Thermomechanics (1)
- Ti-6Al-4V (1)
- Titanium (1)
- Topografie (1)
- Ultrasound (1)
- VM12 SHC (1)
- VSSA (1)
- Vickers (1)
- Vickers indentation (1)
- Virtual experiments (1)
- Water speciation (1)
- Wind turbine blades (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (31) (entfernen)
Morphologies of Fresnoite surface crystals of BT0.75S glass under different atmospheric conditions
(2019)
Fresnoite glass-ceramics are characterized by piezoelectric, pyroelectric and non-linear optical properties. These properties can be adjusted by orienting the fresnoite crystals during crystallization. Crystallization begins at the surface. The first surface crystals are not oriented perpendicular and, therfore, produce a surface layer that has not the intended properties. To overcome this issue, the formation of fresnoite surface crystals at different atmospheric conditions was studied.
The full-notch creep test (FNCT) is a common method to evaluate the environmental stress cracking (ESC) behavior of high-density polyethylene (PE-HD) container materials . The test procedure as specified in ISO 16770 provides a comparative measure of the resistance against ESC using the time to failure of specimens mechanically loaded in a well-defined liquid environment. Since the craze-crack damage mechanism underlying the ESC process is associated with brittle failure, the occurrence of globally brittle fracture surfaces is a prerequisite to consider an FNCT measurement as representative for ESC . Therefore, an optical evaluation of FNCT fracture surfaces concerning their brittleness is essential. Due to the experimental setup, an inevitable increase of the true mechanical stress and the associated appearance of small ductile parts on fracture surfaces is induced in any case. Hence, an FNCT experiment is considered as 'valid', if the corresponding fracture surface is predominantly brittle . Based on laser scanning microscopy (LSM) height data of FNCT fracture surfaces , a universal and easy-to-use phenomenological criterion was developed to assess the validity of distinct FNCT experiments. This criterion is supposed to facilitate a quick evaluation of FNCT results in practical routine testing.
The life time of mechanical components in high temperature applications is basically determined by their workings. Corrosion determines the loss of material corresponding to the loss of the effective load-bearing section and consequently increasing stress levels. To improve the material selection for such applications a numerical life prediction corrosion model for different alloys and environments is needed. Based on the ferritic alloys FeCr and FeCrCo a first quantitative model is to be developed. For this purpose, the alloys are aged at 600°C, 650°C and 700°C in synthetic air under normal pressure for between 10 and 240 hours. The first objective is to establish a quantitative relationship between the oxidation rate as a function of composition and microstructure of the alloys. The influence of the inner interface as an essential parameter for transport by diffusion on the oxidation kinetics is discussed in this presentation.
Introduction/purpose:
Multi-principal-element alloys (MPEAs), also known as complex concentrated alloys (CCAs), have recently come to the attention of the scientific community due to some interesting and unexpected microstructures, and their potential for improving properties such as, e.g. mechanical strength and oxidation resistance in high temperature structural applications. The AlMo0.5NbTa0.5TiZr refractory (r)CCA is one such candidate, showing a two-phase microstructure after a two-stage heat treatment under argon atmosphere at a controlled cooling rate. Since the application conditions intended for this alloy require a long-term high temperature (> 700 °C) mechanical and oxidation resistance, it becomes necessary to assess the possible phase development in this regime.
Methods:
In this contribution, the CALPHAD method is used to calculate phase equilibria for the AlMo0.5NbTa0.5TiZr CCA in the presence and absence of oxygen. Equilibrium phase amount evolution with temperature and Scheil Model for solidification (e.g. Fig.1a and Fig.1b, respectively) are analyzed, which are obtained using the databases TCNI9 and TTNI7 and the Gibbs energy minimizer in the Thermo-Calc software.
Results:
The diagrams reveal that two BCC-based phases could form during alloy solidification, where one phase would be enriched with Mo, Nb and Ta while the other phase, with Al, Ti and Zr. Activity oxides diagrams show that a stable form of aluminum oxide (α-Al2O3, Pearson symbol: hR10, corundum) can be formed. Results obtained by both databases, as well as discrepancies between property phase and Scheil approaches are discussed on the base of experimental results.
Conclusions:
A modeling tool is used to support alloy characterization and development, providing also the possibility to feedback information to improve existing thermodynamic databases.
Thermodynamic study of a refractory complex concentrated alloy (rCCA) using the CALPHAD method
(2019)
Multi-principal-element alloys (MPEAs), have recently come to the attention of the scientific community due to their potential for improving properties such as, e.g. mechanical strength and oxidation resistance in high temperature structural applications. The AlMo0.5NbTa0.5TiZr refractory (r)CCA is one such candidate, showing a two-phase microstructure after a two-stage heat treatment under argon atmosphere at a controlled cooling rate. Since the application conditions intended for this alloy require a long-term high temperature (> 700 °C) mechanical and oxidation resistance, it becomes necessary to assess the possible phase development in this regime. The diagrams reveal that two BCC-based phases could form during alloy solidification, where one phase would be enriched with Mo, Nb and Ta while the other phase, with Al, Ti and Zr. Activity oxides diagrams show that a stable form of aluminum oxide (α-Al2O3, Pearson symbol: hR10, corundum) can be formed.
Fiber reinforced polymers (FRPs) are a well established material in lightweight applications, e.g. in automotive, aerospace or wind energy. The FRP components are subjected to multiaxial mechanical as well as hygrothermal loads. Common operation temperatures are in the range of 213 K and 373 K (-60 °C and 100 °C) at a relative humidity of 10% to 90%. In spacecraft applications, the environmental conditions are even more extreme. However, the correlation between multiaxial mechanical loading and harsh environment conditions have to-date not been investigated in detail. The project aims to investigate the fatigue behavior of FRPs dependent on multiaxial mechanical loading, temperature, and humidity. Extensive experimental testing is performed on flat plate and cylindrical tube specimens, accompanied by numerical and analytical calculations.
Glass strength and fatigue is limited by surface cracks. As subcritical crack growth (SCCG) is governed by ambient humidity, stress corrosion at the crack tip is widely accepted to be the underlying mechanism. However, as water is known to have decisive effect on glass properties and can rapidly enter the crack tip near glass region, SCCG could be affected by such water related phenomena. We tried to mimic these effects studying water dissolution and speciation, mechanical properties, and SCCG in water-bearing glasses. For this purpose, glasses up to 8 wt% water have been prepared by means of high-pressure melting of glass powder - water mixtures.
As part of this effort, SCCG in dry and hydrous commercial micros¬cope slide glass (CW = 6 wt%) was studied in double cantilever beam (DCB) geometry and sub-Tg relaxation was measured by Dynamic Mechanical Analysis (DMA).
For SCCG in ambient air (24% r.h.), SCCG was promoted by the presence of 6wt% bulk water with respect to the dry glass. On the other hand, stress intensity values, KI, required to cause slow crack growth (v < 10-6 ms-1) resemble literature findings for float glass of similar composition in liquid water, which might represent the maximum possible promoting effect of ambient water on SCCG.
For SCCG in vacuum (10-3 mbar), dissolved bulk water causes even more pronounced effects. Most strikingly, it strongly decreases the slope of the log v(KI)-curve, which is a measure of dissipated energy during fracture. A strong increase of sub-Tg relaxation with increasing water content was confirmed by DMA. As a consequence, slow crack growth occurs at KI values as measured in the dry glass whereas fast crack growth occurs at much larger KI than that of the dry glass. Kinks and shoulders shown by the inert log v(KI)-curve indicate that bulk water does not simply affect bulk mechanical properties.
Quality Aspects of Additively Manufactured Medical Implants - Defect Detection in Lattice Parts
(2019)
Additive Manufacturing technologies are developing fast to enable a rapid and flexible production of parts. Tailoring products to individual needs is a big advantage of this technology, which makes it of special interest for the medical device industry and the direct manufacturing of final products. Due to the fast development, standards to assure reliability of the AM process and quality of the printed products are often lacking. The EU project Metrology for Additively Manufactured Medical Implants (MetAMMI) is aiming to fill this gap by investigating alternative and cost efficient non-destructive measurement methods.