Solid State Phenomena Vol. 384

Abstract: The structure evolution and mechanical behavior of the reactive DC magnetron sputtered complex concentrated (or compositionally complex) nitride RM-TiZrHf-N_y coatings with variable nitrogen stoichiometry with RM = V, Nb, and Ta were compared with the reference (TiHfZr)-N_y coatings over a wide range of nitrogen concentrations. Despite the concentrations of the refractory metals deviated from equimolar concentration, homogeneous solid solutions with cubic structures were present in all coatings. Their mechanical properties depended on nitrogen concentration and RM type. The maximum values of hardness (~43 GPa) and indentation modulus (~530 GPa) were achieved in the reference TiZrHf-N_y coatings with (near-) stoichiometric composition. The levels of properties in the coatings with V, Nb, or Ta additions were ~10 % lower and the differences among them were within the scatter of measurements. Thus, the synergy effect from the incorporation of the additional refractory metals into the TiZrHf sub-lattice on mechanical properties was not confirmed.

Abstract: This work investigates the effect of anodized aluminum oxide films on the surface characteristics and corrosion behavior of AlSi10Mg alloy fabricated via laser powder bed fusion (PBF-LB). A ∼10 μm thick oxide layer was formed using sulfuric acid anodizing, under both as-built and stress-relieved (300 °C, 2 h) conditions. Surface morphology, microstructure, and corrosion performance were characterized using scanning electron microscopy, EDS, and immersion testing in 3.5% NaCl solution. Anodizing significantly reduced surface roughness (Ra) from ~14 µm to ~6 µm, with further reduction in extreme topographical features observed in heat-treated samples. Cross-sectional analysis confirmed uniform oxide growth, while immersion tests revealed delayed corrosion onset relative to uncoated material. However, localized pitting was still observed, particularly in heat-treated samples, likely due to Si-network fragmentation. These findings demonstrate that anodizing enhances surface finish and corrosion resistance of AM AlSi10Mg, while microstructural features, such as silicon morphology, remain critical to oxide layer integrity.

Abstract: Over the course of history, the principles of alloying have evolved, with the past fifteen years witnessing the rise of high-entropy alloying theory, which has fundamentally transformed our approach to alloy design. Developing cost-effective and efficient electrocatalysts is critical for large-scale hydrogen production via water splitting. The Ni-Co-W-Zr-P alloy coating offers a promising alternative to noble metal-based electrocatalysts. In this study, we developed a Co-W-Zr-incorporated Ni(P) coating using the electroless plating method. The integration of Co-W-Zr into the Ni(P) matrix notably enhances the number of active sites during the hydrogen evolution reaction. Electrochemical studies revealed a low overpotential of 413.5 mV of the coating when the current density is at −10 mA cm⁻². Kinetic parameters were analyzed using EIS measurements, and a potential mechanism for the hydrogen evolution reaction (HER) was proposed. The coating demonstrated exceptional stability, with no surface degradation even after prolonged electrochemical testing, making it suitable for large or irregularly shaped electrodes required in industrial applications.

Abstract: Glass containers are manufactured by pressing or blowing a hot glass gob (700-1200°C) onto a metallic mould. Beside forming the glass, moulds are heat exchangers for cooling down the glass final product. To this goal, moulds are made of cast iron or copper-nickel alloy due to their thermal properties. If copper-nickel (nickel aluminium bronze) is the most efficient material, cast iron is mainly used for economic purposes. To enhance the properties of the cast iron mould, cold spray coating of a copper-nickel alloy is investigated. Optimization of the parameters process such as spraying temperature (800-1000°C), pressure (40-50bar) and gun’s travel speed (200-400mm/s) lead to a dense and well-bonded “bronze” coating on cast iron. Microstructural analysis is performed thanks to Optical Microscope, Scanning Electron Microscope, Electron BackScattered Diffraction, X-Rays Diffraction and microhardness tests. Finally, a simple thermal experiment has been designed for demonstrating thermal performances of the coating-substrate couple.

Abstract: Magnesium alloys are promising for bioabsorbable stents due to their biocompatibility and degradability. Unlike conventional stainless steel stents that remain in the body and may cause complications, magnesium stents gradually degrade, reducing risks like restenosis and thrombosis. However, magnesium has low corrosion resistance, and its corrosion resistance needs to be improved. The crystal structure is one factor affecting the corrosion properties of metallic materials. Several studies have been conducted on the relationship between crystal structure and corrosion properties to improve magnesium's corrosion resistance. It is essential to elucidate the relationship between crystallographic factors and corrosion mechanisms, in the case of stents, plastic deformation during expansion results in the formation of fine crystal grains and twinning deformation. Therefore, the purpose of this study is to investigate the influence of refined grains and twinning on the corrosion properties of magnesium. Hot rolling and compression are used to refine the crystal grains and form twinning in experiments. The crystal structure can be observed by optical microscopy and SEM-EBSD. Following the evaluation of the crystal structure, immersion tests in brine are conducted to measure the mass loss and observe the corrosion behaviour.

Abstract: The effect of grain size on the initiation behavior of exfoliation corrosion in cold-rolled Mg-14mass%Li-3mass%Al alloy was examined. Exfoliation corrosion initiated after 30 minutes in the coarse-grained structure (279μm), whereas it was delayed to 60 minutes in the fine-grained structure (75μm) and further to 75 minutes in the ultrafine-grained structure (39μm). This delay is attributed to the suppression of shear band formation and localization during cold rolling with decreasing grain size, which enhances the uniformity of surface reactions in the corrosive environment and promotes faster and denser formation of the protective film at the early stage. Accordingly, the improved condition of the initial corrosion film is considered the primary factor responsible for the delayed onset of exfoliation corrosion.

Abstract: Cu and Ni impurities in Mg alloys are deleterious contaminants that reduce the corrosion resistance of the alloy. Mg₂Cu and Mg₂Ni precipitates can cause significant anodic dissolution of the Mg matrix, owing to their potential difference. Suppression of these phases can prevent the deterioration of corrosion resistance. The neutralization of these impurities through the formation of MgZn₂ intermetallic phases has been studied, because the atomic radii of Cu and Ni are similar to that of Zn. As a result, the MgZn₂ phase may precipitate during the rapid cooling that occurs during the solidification of the Mg-6 mass% Zn alloy, and introduce substitutional impurity atoms in the crystal lattice. Mg (Zn, Cu, Ni)₂ phase can be formed instead of Mg₂Cu and Mg₂Ni, in the presence of both of Zn and these impurities. In this study, the solubility of Cu and Ni into MgZn₂ phase when they contain simultaneously was investigated by preparing the intermetallic compounds and the crystal structure evaluation. The lattice parameter of the MgZn₂ phase containing both Cu and Ni impurity decreased to about 5.14 Å with increasing impurity concentration. Cu and Ni impurities are concentrated in the MgZn₂ phase while maintaining the crystal structure, when the impurity concentrations are within the composition range of Cu + 2Ni ≦ 20 at.%. When the concentrations of Cu and Ni exceeded this range, the crystal structure of the MgZn₂ phase transformed from hexagonal (hP12) to cubic (cF24).

Abstract: AZ31 magnesium alloy is a representative magnesium alloy with well-balanced mechanical properties and castability. However, AZ31 magnesium alloy also has the disadvantage of poor corrosion resistance due to its low aluminium content. In previous research, it is known that the corrosion mechanism is such that filamentous corrosion is generated and then changes to full-scale corrosion. However, the relationship between corrosion and bending properties has not been revealed. In this study, AZ31 magnesium alloy was immersed in salt water with a concentration of 5%, and three-point bending tests were conducted to confirm changes in bending stress and strain due to strength loss caused by corrosion. Then, investigated which parameters Ra and Rz, which are indicators of surface roughness, are related to the maximum bending stress of the fully corroded AZ31 magnesium alloy. As a result, when evaluating the relationship between maximum bending stress and corrosion, it was found that it is better to evaluate by Ra of the corroded surface rather than by Rz.

Abstract: Understanding damage mechanisms across scales is crucial to ensure the structural integrity of nickel-based superalloy components under demanding conditions. This study highlights key aspects of a multi-scale experimental approach for analyzing oxygen-induced cracking in Alloy 718. Microcantilever bending tests on specific grain boundaries were combined with corrosion tests and detailed analyses using high-resolution scanning electron microscopy, electron backscatter diffraction, and energy-dispersive X-ray spectroscopy. The results suggest that susceptibility to oxidative attack is significantly impacted by the type of grain boundary, emphasising the importance of local crystallography in oxygen diffusion and elemental redistribution. By bridging local microstructural features with global mechanical response, the presented multi-scale approach allows the parameterization of physically based material models and identifies grain boundary engineering as a promising strategy for improving damage tolerance.