A scannable laser beam is used to generate local thermal gradients in metallic (Co2FeAl) or insulating (Y3Fe5O12) ferromagnetic thin films. We study the resulting local charge and spin currents that ...arise due to the anomalous Nernst effect (ANE) and the spin Seebeck effect (SSE), respectively. In the local ANE experiments, we detect the voltage in the Co2FeAl thin film plane as a function of the laser-spot position and external magnetic field magnitude and orientation. The local SSE effect is detected in a similar fashion by exploiting the inverse spin Hall effect in a Pt layer deposited on top of the Y3Fe5O12. Our findings establish local thermal spin and charge current generation as well as spin caloritronic domain imaging.
We investigate an extraordinarily high ductility in a low alloy carbon steel at an elevated temperature after a quenching and partitioning (Q&P) treatment. The conventional (quenched and tempered) ...reference material does not show similar behavior. Interestingly, the Q&P treated material's ductility is considerably reduced at increasing strain rates while strength remains almost constant. These results indicate the presence of a diffusion-controlled deformation mechanism at elevated temperatures. Our research shows that interlath retained austenite is more stable during deformation at higher temperatures, resulting in a delayed transformation to martensite and therefore to a more pronounced contribution to plastic deformation at (and in the vicinity of) the many interfaces inherently present in this multi-phase steel.
The ability to modify microstructural features and the resulting properties of red gold provides an attractive potential for applications in electronics, dental devices or jewelry. In this study, the ...effect of severe plastic deformation by equal-channel angular pressing (ECAP) on microstructural evolution in an 18-carat AuCuAg alloy, and on the ordering kinetics during subsequent aging, is investigated. Differential scanning calorimetry measurements show that the ordering process is significantly influenced by a plastically deformed microstructure and lattice defects introduced by one or two passes of ECAP. Electron backscatter diffraction and transmission electron microscopy demonstrate that the microstructural evolution during ordering, accompanied by the formation of an L10 superstructure, substantially depends on the thermo-(mechanical) history of the material: While the undeformed material clearly shows a hierarchical structure of twins on different length scales, only a few nanotwins are observed within the strongly deformed microstructures after ECAP. Moreover, after ECAP, static recrystallization is considerably suppressed during long-term annealing at elevated temperatures close to the phase transition temperature. These results clearly highlight the potential of ECAP in combination with heat treatments for microstructural optimization of AuCuAg alloys and their applications.
•ECAP processing of 18-carat AuCuAg alloy (one and two passes) and subsequent aging.•Hierarchical structure of twins is formed during ordering in undeformed AuCuAg.•ECAP substantially changes the ordering kinetics and microstructural features.•Severely deformed microstructure remains stable after (long-term) annealing.•Static recrystallization is considerably suppressed.
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•Plastic food packaging leaches chemicals and toxicity into food simulants.•Probable transfer of toxic chemicals to food, including endocrine disruptors.•Similar toxicity in methanol ...extracts and water–ethanol food simulant.•LDPE, PUR and PVC migrates induce most receptor activity.•Between 8 and 10 631 chemical features migrate into food simulants.
Plastics constitute a vast array of substances, with over 16000 known plastic chemicals, including intentionally and non-intentionally added substances. Thousands of chemicals, including toxic ones, are extractable from plastics, however, the extent to which these compounds migrate from everyday products into food or water remains poorly understood. This study aims to characterize the endocrine and metabolism disrupting activity, as well as the chemical composition of migrates from plastic food contact articles (FCAs) from four countries as significant sources of human exposure. Fourteen plastic FCAs covering seven polymer types with high global market shares were migrated into water and a water–ethanol mixture as food simulants according to European regulations. The migrates were analyzed using reporter gene assays for nuclear receptors relevant to human health and non-target chemical analysis to characterize the chemical composition. Chemicals migrating from each FCA interfered with at least two nuclear receptors, predominantly targeting pregnane X receptor (24/28 migrates). Moreover, peroxisome proliferator receptor gamma was activated by 19 out of 28 migrates, though mostly with lower potencies. Estrogenic and antiandrogenic activity was detected in eight and seven migrates, respectively. Fewer chemicals and less toxicity migrated into water compared to the water–ethanol mixture. However, 73 % of the 15 430 extractable chemical features also transferred into food simulants, and the water–ethanol migrates exhibited a similar toxicity prevalence compared to methanol extracts. The chemical complexity differed largely between FCAs, with 8 to 10631 chemical features migrating into food simulants. Using stepwise partial least squares regressions, we successfully narrowed down the list of potential active chemicals, identified known endocrine disrupting chemicals, such as triphenyl phosphate, and prioritized chemical features for further identification. This study demonstrates the migration of endocrine and metabolism disrupting chemicals from plastic FCAs into food simulants, rendering a migration of these compounds into food and beverages probable.
Understanding the deformation behavior of multi‐phase alloys under external loading requires careful mechanical characterization of the individual constituent phases at various length scales. The ...present study first evaluates the elastic moduli and hardness of the microstructural constituents viz. primary α (αp) and transformed β (secondary α (αs) plus retained prior β) phases in a bimodal Ti–6Al–4V alloy by nano‐indentation using different loads. The bulk mechanical properties of the overall microstructure are then determined by grid wise nano‐indentation, as well as micro‐indentation. The alloy shows a pronounced indentation size effect; the hardness increases with the decrease in indentation load, or depth of penetration. Assuming an iso‐stress condition for individual constituents (αp and transformed β) in the rule of mixture approach, the bulk mechanical properties of the Ti–6Al–4V alloy are reasonably predicted. Such prediction of bulk properties, however, is not possible when a similar calculation is performed using iso‐strain condition. The transformed β phase shows disparity between the estimated and experimental values, while considering the αs and β phases individually, on both iso‐stress and iso‐strain assumptions. From these results, the influence of individual microstructural phases (size, distribution, volume fraction, morphology) and the interfaces between them, is found key in controlling the overall bulk mechanical response of the alloy system.
The study evaluates mechanical properties of microstructural constituents in a bimodal Ti–6Al–4V alloy by nano‐ and micro‐indentation. The role of size, distribution, morphology, volume fraction, and interfaces of these constituents in controlling the bulk mechanical response is rationalized by a rule of mixture based theoretical calculation.
Adiabatic blanking of advanced high-strength steels with initial flow stresses above 1300 MPa is investigated. The blanked edge exhibits a unique S-shape. Localisation and properties of shear bands ...are analysed in shear-compression tests. A shear-compression stress state before separation leads to blanked edges without fracture zone, burr, or roll-over. Numerical modelling predicts the characteristic shape of the blanked edge satisfactorily. Physics-based models reveal that the strain rate sensitivity of the workpiece material is the key parameter affecting the width and the surface hardness of the shear band. Stress triaxiality and strain rate sensitivity determine the minimum size of radii in complex parts blanked without failure.
•First biaxial tension and subsequent biaxial compression study on sheet metal.•Observed biaxial Bauschinger effects differ from uniaxial ones.•Intergranular/intragranular stresses arise due to ...substructure formation.•Dislocation pile-ups near grain boundaries generate elastic back stresses.•Residual stresses directly documented in in-situ neutron diffraction measurements.
Bauschinger effects typically describe a reduction of yield strength after a load path change under uniaxial loading conditions. Here, we use in-plane loading to investigate, for the first time, Bauschinger effects in the sheet metal DC06 under well-defined equi-biaxial loading conditions: We first performed equi-biaxial tensile tests with cruciform specimens up to different maximum tensile strains. Then, smaller specimens were prepared from the equi-biaxially deformed inner part of the cruciform specimens and subjected to equi-biaxial compression. The mechanical results show that the material exhibits distinct Bauschinger effects when subjected to equi-biaxial load path changes, which differ from similar observations under uniaxial loading. Specifically, biaxial Bauschinger effect factors quickly reach a level of saturation, whereas the uniaxial Bauschinger effect factors keep decreasing. These Bauschinger effects can be rationalized by considering the results of TEM and EBSD investigations at the different stages of biaxial loading, particularly by considering the evolution of dislocation densities and the formation of substructures, which are related to intergranular and intragranular stresses. Furthermore, residual stress measurements by XRD and in-situ neutron diffraction show an increase of compressive residual stresses after equi-biaxial tensile deformation and unloading. These residual stresses facilitate yielding during subsequent equi-biaxial compression and therefore also clearly contribute to the observed Bauschinger effects.
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Pseudoelastic NiTi shape memory alloys exhibit different stress⁻strain curves and modes of deformation in tension vs. compression. We have recently shown that under a combination of compression and ...shear, heterogeneous deformation can occur. In the present study, we use digital image correlation to systematically analyze how characteristic features of the nominally uniaxial engineering stress⁻strain curves (particularly the martensite nucleation peak and the plateau length) are affected by extensometer parameters in tension, compression, and the novel load case of shear-compression. By post-experimental analysis of full surface strain field data, the effect of the placement of various virtual extensometers at different locations (with respect to the nucleation site of martensite bands or inhomogeneously deforming regions) and with different gauge lengths is documented. By positioning an extensometer directly on the region corresponding to the nucleating martensite band, we, for the first time, directly record the strain-softening nature of the material-a specific softening behavior that is, for instance, important for the modeling community. Our results show that the stress⁻strain curves, which are often used as a basis for constitutive modeling, are affected considerably by the choice of extensometer, particularly under tensile loading, that leads to a distinct mode of localized deformation/transformation. Under compression-shear loading, inhomogeneous deformation (without lateral growth of martensite bands) is observed. The effects of extensometer gauge length are thus less pronounced than in tension, yet systematic-they are rationalized by considering the relative impact of differently deforming regions.
The public is concerned about plastic pollution, while clear‐cut scientific evidence for an environmental risk of microplastics is absent. This contrast between incomplete scientific knowledge and ...public risk perception is an interesting case for investigating how “environmental risk” is transformed in science communication. This study examines how microplastics risks are framed in peer‐reviewed publications and online newspaper articles, respectively. It also analyzes if the contents conveyed by the frames used in science and the media are consistent. The results show that most scientific studies (67%) frame microplastics risks as hypothetical or uncertain, while 24% present them as established. In contrast, most media articles reporting on microplastic impacts (93%) imply that risks of microplastics exist and harmful consequences are highly probable. The creation of simple narratives (journalists) and the emphasis on potentially negative impacts (scientists) contribute to this inconsistency. The transformation of an uncertain risk into an actual risk is further caused by two inconsistent risk conceptions, namely risk being the probability of a negative outcome (environmental scientists) or being the uncertainty of a negative outcome itself (public). Although the latter differs from the risks identified “objectively” by scientific methods, it allows understanding the risk perception of the public and decision‐makers.
The framing of microplastics risks is analyzed in scientific papers and online newspapers. While scientists mostly refer to uncertainty in their publications, the media report an actual risk. Conflicting risk conceptions, the need to create simple narratives (journalists) as well as the emphasis on potentially negative impacts (scientists) contribute to this inconsistency.
Solid phase extraction (SPE) is often used for enrichment and clean-up prior to analysis of dissolved organic matter (DOM) by electrospray ionization (ESI) coupled to ultrahigh resolution Fourier ...transform ion cyclotron resonance mass spectrometry (FT-ICR MS). It is generally accepted that extraction by SPE is not quantitative with respect to carbon concentration. However, little information is available on the selectivity of different SPE sorbents and the resulting effect for the acquired DOM mass spectra. Freshwater samples were extracted by the widely used PPL, HLB and C18 sorbents and the molecular composition and size distribution of the DOM in the extracts and in the permeates was compared to the original sample. Dissolved organic carbon (DOC) recoveries ranged between 20% and 65% for the three tested SPE sorbents. Size-exclusion chromatography coupled to organic carbon detection (SEC-OCD) revealed that limited recovery by PPL and HLB was primarily due to incomplete elution of a fraction of apparent high molecular weight from the solid phase. In contrast, incomplete retention on the solid phase, mainly observed for the C18 cartridge, was attributed to a fraction of low molecular weight. The FT-ICR mass spectra of the original sample and the SPE extracts did not differ significantly in their molecular weight distribution, but they showed sorbent specific differences in the degree of oxygenation and saturation. We concluded that the selective enrichment of freshwater DOM by SPE is less critical for subsequent FT-ICR MS analysis, because those fractions that are not sufficiently recovered have comparatively small effects on the mass spectra. This was confirmed by the extraction of model compounds, showing that very polar and small molecules are poorly extracted, but also have a low response in ESI-MS. Of the three tested SPE cartridges the PPL material offered the best properties for DOM enrichment for subsequent FT-ICR MS analysis as it minimizes too strong and too weak DOM-sorbent interactions.
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