Open Access

Die Erfindung betrifft ein Verfahren zum Fügen zweier Fügepartner mittels Metallschweißens, umfassend: Bereitstellen zweier Fügepartner, die jeweils mindestens eine Kontaktfläche aufweisen, über die die Fügepartner gefügt werden sollen; Bereitstellen eines aufzutragenden Auftragmittels, wobei das Auftragmittel ein Schichtmaterial beinhaltet, das mindestens ein Metall oder Halbmetall und/oder mindestens ein Oxid eines Metalls oder Halbmetalls enthält; Auftragen des Auftragmittels zur Bildung einer haftenden Schicht auf mindestens einer der Kontaktflächen mit einer vorgegebenen Menge an Schichtmaterial pro Fläche, wobei die Schicht entweder durch Auftragen des Auftragmittels, welches als Dispersion vorliegt, oder durch ein thermisches Spritzverfahren zum Auftragen des Auftragmittels gebildet wird; Fügen der Fügepartner über die mit der haftenden Schicht beschichtete mindestens eine Kontaktflächen unter der Verwendung eines Strahlschweißverfahrens oder Schutzgasschweißverfahrens, vorzugsweise mittels Laser- oder Elektronenschweißens, oder mittels Plasmastichlochschweißens.

Glasses are non‐equilibrium materials that continuously relax toward an equilibrium state. On a macroscopic length scale, glasses exhibit a steady, continuous relaxation over time, as evidenced by changes in volume, viscosity, and enthalpy—aging. However, at the microscopic scale, using high‐resolution techniques such as X-ray photon correlation spectroscopy (XPCS), the dynamics have been reported to occur in stages, where relaxation proceeds via avalanches interspersed with long periods of little to no change3,4. This discontinuous aging of metallic glasses reflects the existence of a heterogeneous microstructure and the complexity of the sampled energy landscape at the atomic level, making the understanding of such relaxation behavior far from trivial. Here, using computational XPCS to analyze microsecond molecular-dynamics simulation trajectories of model glasses and supercooled liquids around Tg, we find that their relaxation dynamics occur in multiple stages with different, growing timescales. These relaxation stages can be traced back to spatially correlated structural dynamics governed by the existence and growth of a percolative network of mobile and immobile domains. The mobile network is responsible for the β-relaxation, while the slow domains, which relax on a much slower timescale, give rise to the long-time relaxation plateau. The percolated domains of immobile atoms are found to have an energetically stable, structurally more ordered configuration, similar to that of the C15 Laves phase. Thus, we present a unified picture that maps dynamical and spatial heterogeneities onto each other and links them to the relaxation behavior of glasses and supercooled liquids, reflecting their heterogeneous microstructure.

Hierarchical nanoporous metals infiltrated with polymers offer enhanced tensile stability while retaining functional porosity, yet their micromechanical deformation mechanisms remain insufficiently understood. Here, a micromechanics-based finite element framework is developed for epoxy-filled hierarchical nanoporous copper (HNPCu) based on experimentally derived structural parameters. The hierarchical ligament architecture across two structural levels as well as selective epoxy infiltration are explicitly resolved, enabling phase-specific analysis of local stress and strain evolution. The predicted tensile response is validated against experiments for different Cu solid fractions (0.1 ≤ 𝜑 ≤ 0.2), and the experimentally observed trends are well reproduced using idealized microstructures. Epoxy infiltration markedly reduces plastic strain localization within the Cu network, leading to a more homogeneous deformation state compared to epoxy-free HNPCu. At the macroscopic level, the tensile response remains largely unaffected by epoxy infiltration at small strains, with differences emerging only at larger deformation. Strain localization is predicted both within Cu ligaments and near Cu–epoxy interfaces, consistent with experimentally observed microcrack formation along phase boundaries and inside the Cu network. These findings provide micromechanical insight into hierarchy-assisted deformation in polymer-infiltrated nanoporous metals and establish a basis for microstructure-guided design of mechanically robust hierarchical materials.

This is the first-ever report of igniting a combustive process that we tentatively denote as a mixing-induced self-propagating reaction (MXSR) in an inorganic system by a simple intensive mixing of the educts. The occurrence of MXSR is proven by observing a spike during in situ temperature monitoring. We demonstrate this on the example of agitating copper and sulfur powders in a ball-free planetary mill jar, igniting a MXSR without the external heating or the mechanical impact. Intensive powder agitation yields a mixture of nanocrystalline covellite (CuS) and digenite (Cu1.8S) in under 2 min. MXSR ignition thresholds are precisely determined (jar filling ≥40%, mixing speed ≥700 rpm, Cu:S molar ratio of 0.625–1.00). If these thresholds are not respected, a gradual reaction partly proceeds and an unstable mixture of digenite and non-reacted sulfur is formed, which is transformed into covellite with time. In specific cases, MXSR can be ignited within a few minutes after the termination of mixing. In the end, scalability to 40 and 62.5 g scales in planetary and mixer mills, respectively, is demonstrated and the products' thermoelectric utility for waste heat conversion is showcased. The proposed MXSR pathway overcomes state-of-the-art limitations in mechanochemistry, including product contamination from milling media abrasion and energy-intensive activation, while achieving decent alignment with green chemistry (100% atom economy, 88% and 91% reaction mass efficiency for the experiments performed on a larger scale in a mixer and planetary mill, respectively).

Repair welding of cast iron components is widely employed to restore structural integrity in large-scale systems such as wind turbine hubs. However the brittleness and susceptibility of cast iron components to crack initiation and combined effect of weld bead geometry and Residual Stresses (RSs) on Fatigue Crack Growth (FCG) highlights the need for a thorough understanding and potential optimisation of the process. This study develops an integrated experimental–numerical framework to elucidate the FCG behaviour of repair-welded ductile cast iron, explicitly accounting for RS and geometric effects. FCG tests were conducted on welded specimens extracted from three different areas, namely Weld Metal (WM), Heat-Affected Zone (HAZ), and Base Metal (BM) to determine material-specific crack growth parameters. A coupled thermo-mechanical finite element model is used to predict the RS fields induced during single- and multi-pass repair welding, followed by three-dimensional FCG simulations incorporating semi-elliptical surface defects and elliptical embedded cracks under the influence of RS. Parametric analyses are performed to evaluate the effects of weld bead removal, number of passes, and inter-pass temperature on the RS evolution, Stress Intensity Factors (SIFs), and synthetic S–N curves. The experimental results show the WM exhibits the lowest threshold SIF range, while the BM shows the highest. The numerical results indicate that multi-pass welding with controlled inter-pass temperature reduces RS magnitudes by up to 25%, whereas weld bead removal improves the fatigue life by mitigating local stress concentration. The developed numerical framework is applied to a large-scale wind turbine hub to demonstrate its predictive capability, with the results showing that RS can entail a twofold reduction of the fatigue life. The proposed methodology provides a robust basis and highly cost efficient means for optimising repair welding parameters to enhance fatigue performance in service-critical cast iron structures.