Aluminium-silicon (Al-Si) cast alloys play a crucial role in the automotive industry, with increasing demand in electric vehicles (EVs). In EV applications, aluminium components are often exposed to atmospheric conditions, making corrosion resistance a critical factor, as well as mechanical performance. This study examines the effects of melt treatments - grain refinement and modification - along with chemical composition on the corrosion resistance and mechanical properties of Al-Si alloys. Three common alloys (AlSi9Cu3, AlSi10, and AlSi12) are cast using sand casting and gravity die casting to evaluate the influence of casting processes with different cooling rates. Each alloy is tested under three conditions: untreated, grain refined, and grain refined/modified. Mechanical properties are evaluated via tensile tests according to DIN 50125, while corrosion resistance is assessed through immersion in an HCl-NaCl solution, based on ISO 11846. Results indicate that iron content reduces ductility due to formation of β-Al5FeSi, while modification enhances elongation, particularly in die-cast samples. Copper presence in AlSi9Cu3 significantly deteriorated its corrosion resistance. Higher cooling rates and modification treatment further decrease corrosion resistance. This study provides insights into the correlation between casting methods, alloy composition, and melt treatments on the corrosive and mechanical performance of Al-Si cast alloys.

Recycling silicon carbide-reinforced aluminium metal matrix composites (Al-MMCs) through conventional remelting presents a significant challenge because the process leads to melt quality and promotes the formation of defects that are difficult to reverse. In this study, industrial AlSi9Mg–20

AbstractCeramic foam filtershavebeen usedin aluminum foundries since 1974 to increase the purity of the melt. In practice, the implementation of the foam ceramic filter in the casting system is in most cases a question of space on the pattern plate. It does not follow any defined rules but is at best guided by design recommendations from the filter manufacturers. To increase the filtration efficiency, the filter position in the casting system is examined. For this, 20 and 30 ppi filters were scanned with computer tomography (CT). The data from the CT were then loaded into the simulation program Flow 3D. With this program, four different filter positions as well as the influence of the filter length and roughness of the filter surface are investigated concerning their filtration effectiveness. The simulation results are subsequently evaluated with casting trials. For this, four different molds for four different filter positions were created. The same alloy (AlSi7) was used for the trials as for the simulation. To study the behavior of particles during the filtration process, impurities were added to the melt using 3 wt.% Al2O3 - Metal Matrix Composite. After the samples were casted, the filters are cut out and the Al2O3 particles in the filter are counted for each filter position. The comparability of the casting trials and the results of the simulation have been examined.

AbstractIron (Fe) provides a non-reactive dissolved impurity in aluminum (Al) alloys, which forms a coarse, plate-shaped intermetallic β-phase during solidification. This β-phase is detrimental to the mechanical and casting properties. Therefore, the reduction of Fe by binding in Fe-containing intermetal-lics (sludge phase) was realized via a two-stage procedure, which consisted of conditioning of the melt by manganese (Mn) and chromium (Cr) with subsequent-ly applied metal melt filtration. For this purpose, the formation characteristics of the Fe-rich intermetallic phases were investigated regarding the temperature, time, and initial chemical composition to separate these intermetallics from the residual melt. To evaluate the different process parameters of Fe removal for a potential implementation in lightweight metal foundries, a process technology on an indus-trial scale was developed in cooperation with an industrial partner. The examina-tion of samples in optical microscopy (OM) using image analysis were conducted to determine the area fractions of Fe-rich intermetallics. In addition, optical emis-sion spectrometer (OES) measurements were performed. Complementary investi-gations were achieved by scanning electron microscopy (SEM), with energy dis-persive spectroscopy (EDS), and electron backscatter diffraction (EBSD) to measure the partial chemical composition and for phase identification. The for-mation characteristics of the Fe-containing phases were investigated using DSC cooling curves and selective sampling in quenching experiments. In the experi-mental trials, a maximum reduction of iron of ≈50% was revealed compared to the unfiltered sample, whereby greater influence on the formation of α-intermetallics was inferred by temperature than by time. Moreover, the elements Mn and Cr were reduced by about 66% and 86% at 620 °C, respectively, thus, the element contents in the filtered samples approached the chemical composition of the standard alloy (EN-AC-AlSi9Cu3(Fe)).

In this study, filtration of aluminum alloy (Al) with different weight fractions of SiC particles (SiCp) was investigated. Therefore, three different filter materials of 20 pores per inch (ppi) ceramic foam filters (CFF) were tested. A special three-chamber furan mold was used for the casting trials to provide uniform filling and flow conditions for the filtration process. Samples from sections of the gating system, as well as from the filter, were analyzed by optical light microscopy to determine the amount, size, and distribution of SiCp. A scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS) was used for obtaining the element distribution in the composite. The filtration efficiency increased by decreasing the weight fraction from 20 to 5% of SiCp and reached a significant particle reduction of over 90%. Investigations of CFFs with a weight fraction of 10% have shown a clogging effect and metal flow interruption through the 20 ppi filter. An oxide layer was detected around the respective SiCp in the EDS. Moreover, a strong accumulation effect was observed, indicated by a steadily flattening curve of the density functions after each additional remelting cycle of the same composite material.

The vapor pressure deficit reflects the difference between how much moisture the atmosphere could and actually does hold, a factor that fundamentally affects evapotranspiration, ecosystem functioning, and vegetation carbon uptake. Its spatial variability and long-term trends under natural versus human-influenced climate are poorly known despite being essential for predicting future effects on natural ecosystems and human societies such as crop yield, wildfires, and health. Here we combine regionally distinct reconstructions of pre-industrial summer vapor pressure deficit variability from Europe’s largest oxygen-isotope network of tree-ring cellulose with observational records and Earth system model simulations with and without human forcing included. We demonstrate that an intensification of atmospheric drying during the recent decades across different European target regions is unprecedented in a pre-industrial context and that it is attributed to human influence with more than 98% probability. The magnitude of this trend is largest in Western and Central Europe, the Alps and Pyrenees region, and the smallest in southern Fennoscandia. In view of the extreme drought and compound events of the recent years, further atmospheric drying poses an enhanced risk to vegetation, specifically in the densely populated areas of the European temperate lowlands. The atmosphere has dried across most regions of Europe in recent decades, a trend that can be attributed primarily to human impacts, according to tree ring records spanning 400 years and Earth system model simulations.

The formation of iron (Fe)‐containing intermetallics during solidification is challenging due to the influences of cooling rate and chemical composition. Differential scanning calorimetry (DSC) is an accurate analysis method but merely replicates adjustable cooling conditions. Thereby, the solidification range is traversed several times before DSC measurement. For this purpose, thermal analysis cooling curves with double thermocouple are conducted to investigate the formation temperature of Fe‐rich intermetallics in different AlSi casting alloys. In addition, the influence of chemical composition is examined by increasing the initial contents of iron, manganese, and chromium to 0.8 wt% each. The double thermocouple setup allows determining feeding points and solid fractions of the alloy compounds. To evaluate the data sets, the statistical program R is used to improve data processing and smoothing. The signature of Fe‐rich intermetallics in the temperature–time plots corresponds to the detected phases in optical micrographs. In addition, scanning electron microscopy with energy‐dispersive spectroscopy and electron backscattering diffraction are used to measure the local chemical composition and identify the iron‐rich intermetallics. Real‐time evaluation (differential calculation, first derivative, incl. smoothing) for an applicable filtration process can be performed using thermocouples with analog‐to‐digital converter and Python programs with an interactive graphical interface.

The European Dendroecological Fieldweek (EDF) is a one-week course that takes place every year at varying locations in Europe according to the principle "Bring tree-ring research to the people". The EDF welcomes early -career to advanced researchers, but also forest service and other federal agency employees and private people interested in tree-ring sciences from all over the world. It encompasses a large spectrum of dendrochronological field, laboratory and data analysis methods and scientific fields including climatology, ecology, physiology, geomorphology and archaeology. Multiple scales of observations from the individual cell to the ecosystem level and from seasonal to multi-centennial periods are covered. Work on mini research projects in topic groups al-ternates with keynote lectures and individual participants' presentations.As one of the first in-person tree-ring meetings since the start of the COVID-19 pandemic the 31st EDF was held in summer 2021 in Val Mustair, Switzerland. Topics included i) Tree age and climate sensitivity of a relict, old -growth Scots pine stand, ii) Blue intensity-based climate sensitivity of Norway spruce growth, iii) Tree rings as indicators of grey larch budmoth outbreaks, iv) Growth of larch trees along an abandoned irrigation channel, v) Wood anatomical characteristics of two alpine creeping shrub species, and vi) Historical dating of a stable and a residential house. Alongside with their educational value these projects allowed novel insight into the age structure and growth dynamics of the sub-alpine forests and beyond in the valley and provided valuable outcome to the local stakeholders such as the Nature Park Biosfera Val Mustair, the local forest service and the public of Val Mustair.Under hindered conditions due to the pandemic, the 31st EDF still demonstrated its strength as an international educational and interdisciplinary scientific field and lab course, combining teaching with the application of cutting-edge technologies.

The influence of chemical composition and cooling rate is investigated on a secondary die‐casting alloy with the aim of reduction of iron using metal melt filtration in a specially developed laboratory filtration apparatus. Based on the defined thermal conditions of the device, differential scanning calorimetry (DSC) cooling curves are determined to obtain formation temperatures of the primary iron‐containing intermetallic phases (also called sludge phases) for an EN AC‐AlSi9Cu3(Fe) alloy with different contents of Fe, Mn, and Cr. The DSC samples are then analyzed metallographically, and the results are compared with CalPhaD calculations. After that, the temperature of the sludge formation is adjusted using furnace‐operating curves to confirm the presence of the intermetallic phases by sedimentation and filtration trials. The Fe content is reduced by about 50%, as shown by chemical analysis based on remelted materials in optical emission spectroscopy. The elements Mn and Cr decrease by ≈66% and 86% after filtration at 620 °C, respectively.

The present study investigates the influence of melt conditioning and filtration on iron-rich phases in AlSi9Cu3 alloy. This method avoids the formation of brittle β phase (Al4.5FeSi) and reduces the iron content by sedimentation and subsequent filtration. The comparison of this method to conventional casting (reference) with a higher Fe content is performed by means of scanning electron microscopy, tensile tests, ultrasonic fatigue tests, X-ray diffraction and X-ray microtomography. The reference batch revealed a high proportion of β plates, which are responsible for low strength compared to melt conditioned batch under uniaxial tensile stress. The fatigue properties of melt conditioned batch are significantly improved compared to the reference state. X-ray microtomography scans before and after ultrasonic fatigue tests were evaluated by machine learning algorithms (Trainable Weka Segmentation). The superposition of the segmented fatigue crack with the initial, undeformed state was performed for the first time and showed that the fatigue crack path is strongly influenced by the brittle Fe-rich phases.

The development of an innovative hybrid lightweight piston for marine engines is intended to help reduce emissions and operating costs. The piston consists of a piston base and a top part. In the manufacture of the piston base a preform is cast and the final geometry is produced by means of subsequent forming (forging). This significantly improves the mechanical properties of the material. As a result of the possible material advantages in the overall process chain, the piston base can be designed as a “lightweight component”. By examining the entire process chain of “primary casting - forging", the amount of used materials is significantly reduced, especially in the “casting” production route, since even minor internal defects can be tolerated after the preform has been cast. For the subsequent forging process, this material pre-distribution thus represents an optimum initial forging shape. The upper part of the piston is made of a layered composite material. Here, the special material is already applied to the blank prior to the forging process by laser or PTA build-up welding. This means that the filler material is also formed together with the base material, which in turn has a positive effect at the mechanical properties. This is followed by a heat treatment, which further improves the high temperature resistance. Due to the higher strength and corrosion resistance of the piston head, the temperature and pressure of the combustion chamber can be increased, enabling the required reduction of emissions and fuel.

In view of filtration of Fe‐enriched intermetallics to decrease Fe content in secondary aluminum alloys, the formation of so‐called sludge particles has been investigated depending on dwell time and chemical composition using an AlSi9Cu3 secondary alloy with high Fe content. To evaluate the dwell time dependency, samples are cast into ceramic crucibles and held at 620 °C for varying times. Furthermore, Mn and Cr have been added to the melt in different amounts and the alloys are treated for 6 h at 620 °C. The samples are analyzed using light optical micrographs and image analysis to reveal particle sizes and distribution as well as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD) for phase identification. It is found that the growth of Fe containing sludge particles stagnates after reaching a specific value and is not significantly affected by ultra‐long dwell times. Mn addition has a minor effect on the the particle size distribution preserving large particle sizes, whereas Cr addition leads to a smaller sludge particles. Generally, the sludge consists of the cubic α‐phase. Additionally in the presence of Cr, Fe, and Cr concentration gradients occur in the cubic α–Al–(Fe,Mn,Cr)–Si phase and the Al13Cr4Si4‐phase is contained in the centers of the sludge particles. It is concluded that Mn addition is favored due to larger particle size and higher efficiency to bind Fe in the α‐phase than by Cr or Cr and Mn addition.