Seznam abstraktů 2026: POSTEROVÁ SEKCE E

The development of temporary biomedical implants is currently focused on bioresorbable metallic materials that provide mechanical support during tissue healing and subsequently degrade in the human body without the need for surgical removal. Zinc-based alloys represent a highly promising material system for orthopedic applications due to their favorable biocompatibility and controllable degradation rate. Therefore, the development of novel Zn alloys is directed toward optimizing their chemical composition to achieve the required mechanical performance while ensuring safe and effective temporary bone fixation.
In this study, the as-cast Zn-0.4Mg (wt.%) alloy state was processed by equal channel angular pressing (ECAP) after a prior homogenization annealing. The applied severe plastic deformation resulted in a significant modification of the microstructure, which resulted in a substantial improvement of mechanical properties. After processing, the alloy exhibited an ultimate tensile strength of approximately 220 MPa together with high ductility of about 87%. In contrast, the as-cast Zn alloy state showed a tensile strength of only about 120 MPa and negligible ductility below 1%. These results confirm that the combination of ECAP and heat treatment represents an effective approach for optimizing the mechanical behavior of Zn alloys for potential biomedical applications.

Lead-free Sn-Ag-Cu (SAC) solders are widely used in battery electronics, especially in battery management system PCBs and power modules, where reliable solder joints are essential [1]. This study investigates the separate effects of bismuth and gallium on the microstructure and thermal properties of SAC305 solders. Alloys containing 1, 2, and 4 wt.% Bi, as well as 1, 2, 4, and 6 wt.% Ga, were prepared and analyzed using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and differential scanning calorimetry.
Ga-modified SAC305 alloys showed refined Ag-rich regions with Ag₂Ga formation replacing Ag₃Sn, and suppression of Cu₆Sn₅ via γ-Cu₂Ga and CuGa₂ phases. Melting temperature decreased from 219.7 °C to 201.5 °C. Small Ga additions (1-2 wt.%) improved mechanical properties, while higher contents (4-6 wt.%) induced brittleness. Electrical resistivity slightly increased but remained industrially acceptable.
Bi-modified SAC305 exhibited a melting temperature drop of up to 15 °C. Ag₃Sn lamellae concentrated in interdendritic regions, while Cu₆Sn₅ evolved to vermicular shapes at higher Bi levels. Low Bi (1 wt.%) enriched the Sn matrix, whereas >2 wt.% Bi formed discrete particles along intermetallic boundaries or as globular phases in the Sn+Bi eutectic.
These microstructural and thermal changes affect soldering conditions and joint reliability, highlighting the potential of Bi- and Ga-modified SAC solders for optimized thermal, mechanical, and processability performance in high-reliability battery electronics.

Reference:
[1] Jeyun Yeom et al., Degradation of high reliability lead‑free solder joints under harsh thermal cycling test — Microelectronics Reliability 173 (2025) 115868.

Acknowledgement:
Funded by the EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under the project No. 09I04-03-V02-00046.

Investigating hydrogen sorption in hydride-forming materials is essential for advancing a wide range of industrial technologies, particularly hydrogen storage. Among such materials, LaNi5 is a well-known candidate due to its ability to form multiple hydride phases.
We have employed Density Functional Theory (DFT) calculations implemented in the VASP code to investigate the structural, energetic, and magnetic properties of hydrogen in the LaNi5 structure (space group P63/mmc, No. 194). First, the equilibrium lattice parameters of the pristine LaNi5 structure were determined. Subsequently, several hydrogenated configurations were constructed by introducing hydrogen atoms into additional interstitial sublattices of the host structure, specifically the 2b, 6c (in two different configurations), and 12d sites. In these models, the selected sublattices were assumed to be fully occupied by hydrogen. An additional configuration was also considered in which hydrogen simultaneously occupied all the above-mentioned interstitial sites.
Furthermore, the thermodynamic end-member LaSn5H6 was also investigated using first-principles calculations. The results of our calculations can serve as input for thermodynamic modeling of the system within the CALPHAD (CAlculation of PHAse Diagrams) framework.
Our results provide insight into the influence of hydrogen incorporation on the structural stability and magnetic properties of LaNi5-based hydrogen storage materials.
This work was created as part of the project No. CZ.02.01.01/00/22_008/0004631 Materials and technologies for sustainable development within the Jan Amos Komensky Operational Program financed by the European Union and from the state budget of the Czech Republic. Computational resources were provided by the e-INFRA CZ projects (ID:90254 and LM2018140), supported by the Ministry of Education, Youth and Sports of the Czech Republic. These resources were utilized through IT4Innovations National Supercomputing Center, MetaCentrum, CERIT Scientific Cloud as well as CERIT center.

This study investigates the deposition conditions of carbonate-based coatings on AZ31 magnesium alloy pretreated with an Mg(OH)₂ interlayer in the presence of ammonium ions. The effect of temperature and exposure time on phase formation, growth mechanism, and corrosion performance was systematically evaluated. At laboratory temperature, no continuous carbonate coating was even formed after 12 or 24 h of deposition. Instead, substrate corrosion occurred, accompanied by further Mg(OH)₂ and hydrotalcite formation and crack development within the surface layer. Increasing the temperature to 50 °C led after 6 h primarily to chemical destabilization and partial dissolution of the Mg(OH)₂ interlayer rather than controlled carbonation. The first nuclei appeared after 12 h of exposure, and after 24 h the surface was fully covered by the newly formed layer. However, EDS and XRD analyses revealed that the coating predominantly consisted of hydromagnesite rather than anhydrous magnesium carbonate.
Increasing the temperature up to 90 °C under hydrothermal conditions, hydromagnesite remained the dominant phase. The resulting hydromagnesite coating was compact, homogeneous, and significantly improved the corrosion resistance of the system.
The results demonstrate that increasing temperature in the presence of ammonium ions is insufficient to induce controlled carbonation of the Mg(OH)₂ interlayer. Hydrothermal conditions primarily enhance the crystallinity and protective performance of hydromagnesite-based coatings.

Microbial activity can represent a significant factor in the degradation of metallic materials. Nevertheless, microbially influenced corrosion (MIC) of magnesium alloys has received limited attention. Methanogens are microorganisms that use hydrogen to produce methane and can influence corrosion processes. The study of MIC requires experiments conducted in cultivation media; for methanogens, NITE 927 medium is commonly used, containing a wide range of chemical components. To correctly interpret the specific effect of methanogens on corrosion, it is essential to first assess the influence of key medium constituents on the corrosion behavior of the investigated material.
This work focuses on the effect of HEPES and cysteine on the corrosion behavior of AZ31 alloy. Immersion tests and potentiodynamic polarization showed that HEPES significantly accelerates the corrosion of the AZ31 alloy and promotes the initiation of pitting corrosion. Cysteine also increases the corrosion rate of AZ31, although to a lesser extent. Neither HEPES nor cysteine adsorb on the corrosion products, which consist predominantly of magnesium hydroxide and magnesium phosphate.

Titanium alloys are widely investigated for biomedical implants because of their favorable combination of biocompatibility, strength, and the possibility of achieving a lower elastic modulus compared to conventional Ti-6Al-4V. Additive manufacturing offers an effective route for producing such alloys while allowing control over microstructure and resulting properties. In this work, selected Ti alloys were prepared by the methods of additive manufacturing and systematically characterized to evaluate their suitability for implant applications.

Samples were fabricated under different processing conditions to assess their effect on microstructure, porosity, and mechanical behavior. Microstructural observations were carried out using scanning electron microscopy and optical microscopy, focusing on grain morphology, uniformity, and the presence of unmelted or coarsened regions. Porosity was evaluated through image analysis and density measurements. In addition, oxygen and nitrogen levels were monitored to ensure that processing did not introduce excessive contamination, which could negatively influence mechanical properties.

Mechanical behavior was assessed using Vickers microhardness testing and resonant ultrasound spectroscopy, enabling determination of elastic moduli. The results identified processing conditions that produced fully dense materials with refined microstructures and low porosity. The measured Young’s modulus and hardness varied as expected with changes in alloy composition and microstructure, reflecting differences in phase stability and solid-solution strengthening.

Overall, the study demonstrates that Ti alloys prepared by additive manufacturing can achieve adjustable mechanical properties and consistent microstructural quality, confirming their potential for further development in biomedical implant applications.

Beta titanium alloys are promising materials for biomedical and aerospace applications due to their low elastic modulus, high strength, and biocompatibility. For such applications, however, a thorough understanding of their fatigue behaviour is essential. This study provides an initial insight into the fatigue properties of two additively processed beta titanium alloys (Ti-13Nb-13Zr and Ti-15Mo) produced from recycled feedstock. Both alloys were manufactured by recycling titanium scrap (offcuts and similar waste), followed by powder preparation for 3D printing of fatigue test specimens. The aim was to evaluate whether the combination of recycling and additive manufacturing can deliver adequate fatigue performance.
Basic fatigue tests were conducted on a limited number of samples, focusing on comparison of the two alloys and complemented by fractographic analysis and evaluation of the results with respect to available literature, which remains scarce for fatigue behaviour of the investigated beta titanium alloys produced via additive manufacturing. The integration of additive processing with the aspect of recycling makes this work a unique contribution to the field.
Although the limited number of specimens did not allow the construction of a complete S N curve, the obtained results confirm the potential of recycled beta titanium alloys for applications subjected to cyclic loading and indicate directions for further optimisation of the manufacturing route.

Nickel-based superalloys are essential for the hot-end components of aero-engines due to their exceptional strength and stability at elevated temperatures. This research focuses on BZL-12Y, a cost-effective, low-density γʹ-strengthened cast superalloy intended for expandable jet engine applications. Despite its favorable density profile, the current commercial heat treatment, comprising a two-step homogenization and a two-step aging process, fails to meet industry standards for mechanical properties. The alloy exhibits reduced ductility, a diminished creep life, and lower resistance to low-cycle fatigue (LCF).A thorough analysis of the failure mechanisms was conducted on the industrially heat-treated alloy to address these performance limitations. A microstructural analysis utilizing scanning electron microscopy (SEM) and fractography revealed that the microstructure predominantly exhibited a dendritic formation, with failures consistently initiating in the inter-dendritic regions. High-magnification measurements revealed that MC carbides serve as the primary nucleation sites for micro-cracks. By employing Electron Backscatter Diffraction (EBSD), we acquired enhanced insights into the strain fields that intersect between adjacent carbides, facilitating the coalescence of micro-cracks. The crack propagation trajectory traverses high-energy interdendritic regions before ultimately breaching grain boundaries, resulting in catastrophic failure.This work proposes a microstructural refining technique utilizing an enhanced homogenization process developed with Thermo-Calc software. The primary objective is to eliminate dendritic segregation and dissolve detrimental interdendritic phases without initiating melting. Thermodynamic modeling was employed to determine the precise temperature range for homogenization by contrasting the γʹ-solvus temperature with the solidus of the non-equilibrium eutectic phases. We employed Scheil-Gulliver simulations to determine the temperature at which the "last liquid" solidifies, leading to the selection of a crucial safety threshold of 1090°C. A novel multi-stage heating protocol (1200-1240°C for 1-25 hours) has been established to enhance the uniformity of the chemicals. This study establishes the foundation for enhancing BZL-12Y's strength by transforming its susceptible cast state into a homogenized microstructure capable of meeting the rigorous demands of next-generation jet propulsion.

Extending the service life of tungsten electrodes while maintaining high welding quality remains a key challenge in optimizing the TIG process. This work addresses this issue by investigating two critical factors: the type of dopant added to tungsten and the influence of repeated arc ignition/extinction cycles. By comparing electrodes doped with ThO₂ and La₂O₃ subjected to two operating regimes (continuous and intermittent), this study examines the morphological, microstructural, chemical, and mechanical evolution of the electrodes. Particular emphasis is placed on contamination by metallic vapors, a phenomenon still insufficiently documented yet directly impacting electrode integrity and arc stability. The study highlight that the choice of electrode must be conditioned to both the operating regime and the metallurgical context of welding. Accordingly, W-ThO₂ electrodes are recommended for continuous welding regime with stable thermal constraints, whereas W-La₂O₃ electrodes are more suitable for intermittent welding, despite requiring careful consideration of chemical contamination.

Flax biocomposites are increasingly being considered for lightweight structures within the framework of circular economy principles, including end-of-life reuse and mechanical recycling. However, under real-world operating conditions, natural fibers are highly hygroscopic and may be exposed not only to water but also to urea-based automotive fluids, such as AdBlue. These media can affect fiber swelling and the fiber-matrix interface. This paper aims to verify whether the controlled sorption of these fluids alters load transfer and, consequently, the tensile properties of the flax biocomposite. For the purposes of this study, specimens comprising flax reinforcement and a polymer matrix were prepared and divided into three groups: a dried reference group, a water-saturated group, and an AdBlue-saturated group. Following immersion conditioning to a constant mass, standardized tensile testing is performed, complemented by fracture surface analysis to identify the dominant failure mechanisms. The paper will discuss the dependence of the tensile response on the type of medium, focusing on phenomena such as water-induced matrix plasticization, interfacial adhesion changes, and the potential influence of dissolved AdBlue components on crack initiation. The objective of this study is to evaluate the impact of various saturation levels on composite strength and potential interfacial debonding. The findings will provide practical recommendations for the design and qualification of flax biocomposites exposed to moisture and operating fluids, thereby linking operational exposure with recycling-oriented reuse scenarios.

The influence of intermetallic phase precipitation on the microstructure and mechanical properties of zirconium alloys Zr-4Nb-1Fe and Zr-4Sn-1Cr was investigated. Both alloys were initially homogenized at 1200 °C, water quenched and subsequently annealed at 550 °C for durations ranging from 1 to 72 h. Phase evolution was studied using X-ray diffraction and differential scanning calorimetry, while microstructural changes were analysed by scanning electron microscopy. Mechanical properties were evaluated by Vickers microhardness testing. The precipitation of intermetallic phases ZrFe₂ in Zr-4Nb-1Fe and ZrCr₂ in Zr-4Sn-1Cr was confirmed after annealing using X-ray diffraction. In the Zr-4Nb-1Fe alloy, annealing led to the transformation of metastable phases present in the quenched condition and precipitation of the α phase, resulting in a decrease in microhardness despite intermetallic particle growth. In the Zr-4Sn-1Cr alloy, microhardness gradually decreased with increasing annealing time, which is attributed primarily to coarsening of α lamellae. The results show that, in both alloys under the chosen annealing regime, the supposed strengthening caused by precipitation of intermetallic phases is outweighed by microstructural softening mechanisms.

This study investigates chemical and electrochemical post-processing of additively manufactured WE43 Mg alloy in order to remove adhered partially melted powder particles. The objective was to evaluate the influence of different etching media on surface morphology, strut removal uniformity, and the extent of localized corrosion damage. Chemical etching was performed in 30% and 50% H3PO4 solutions. In both cases, intensive strut surface phosphating occurred, accompanied by excessive material dissolution and localized corrosion attack of the base struts. Etching in a 5% mixture of HCl and HNO3 resulted in visible pitting and significant surface oxidation. The most favorable results were achieved by electrochemical etching in a 5% HNO₃ solution in water-ethanol mixture for 300 s under applied voltage of 1V. This treatment enabled controlled and homogeneous removing of adhered particles without pronounced corrosion attack and minimal oxidation of base struts compared to the other tested conditions. The results demonstrate that appropriately selected electrochemical parameters provide a more controlled surface modification route for additively manufactured WE43 alloy, minimizing localized corrosion effect while ensuring uniform surface refinement. The findings contribute to optimizing post-processing strategies for Mg alloys produced by additive manufacturing, where controlled surface quality and preservation of structural integrity are critical for subsequent functional performance.

This study evaluates the influence of chemical composition on proton-induced primary radiation damage in selected Al-Li-X alloys relevant to space applications. The hypothesis assumes that variations in alloying additions lead to measurable differences in defect magnitude and spatial distribution under identical irradiation conditions. Monte Carlo simulations based on the Binary Collision Approximation were performed to model proton irradiation in a near-Earth space environment over a broad energy range, followed by detailed calculations at 30, 90, and 2000 keV. The results show a clear dependence of primary radiation damage on proton energy. Maximum vacancy concentration and damage uniformity factor decrease with increasing energy. Differences between alloys are most pronounced at low energy, where elastic collisions dominate atomic displacements. At higher energies, defect magnitude and spatial distribution become largely independent of composition. The results support the proposed hypothesis and provide insight relevant to the selection of Al-Li-X alloys for structural applications in the space radiation environment.

The study focuses on a comprehensive analysis of the structure and thermal stability of the magnetic parameters of two commercial ring-shaped strontium ferrite magnets, for which the manufacturing conditions were unknown. Structural characterization was carried out using powder X‑ray diffraction (XRD) and scanning electron microscopy (SEM) with EDX analysis. XRD confirmed the magnetoplumbite-type structure SrFe12O19 in both samples. The evaluation of the March parameter revealed a pronounced preferential grain orientation in the (001) plane for the anisotropic sample, whereas the second sample was classified as isotropic, exhibiting no significant texture.
Magnetic properties were determined from the J-H and B-H magnetization curves measured using the hystergraph in the temperature range of 25-190 °C. Anisotropic sample exhibited a rectangular magnetization curve with a remanence-to-saturation ratio of 0.951-0.923, which decreased only by a few hundredths with increasing temperature. In isotropic sample, this ratio was lower (0.663-0.649), and the curves displayed a significantly more rounded shape. With increasing temperature, both samples showed a linear decrease in remanent induction, saturation polarization, and the maximum energy product BHmax (Pearson correlation coefficient ≈ 0.99). The slope of the remanent induction decrease was −1.178 mT·K-1 for anisotropic and approximately −0.423 mT·K-1 for isotropic sample. A similar trend was observed for saturation polarization and BHmax. In contrast, the coercive field HcJ increased linearly, with slopes of 0.908 kA·m-1·K-1 for anisotropic and 0.735 kA·m-1·K-1 for isotropic sample. The results confirm higher remanent induction and energy product values for the anisotropic ferrite; however, these are accompanied by a more pronounced temperature dependence of the magnetic parameters.

The article analyses the dynamic response of a spinning module body made of an aluminium alloy, aiming to improve its damping properties under high-frequency vibrations in the pre-resonance and resonance regions, which are a critical factor influencing system stability and service life. Since the inherent damping capacity of the aluminium alloy body is insufficient for the operating conditions, structural modifications were proposed, including the application of a damping material to the body cavities (forming a hybrid metal-damping material structure) and an increase in stiffness through thicker ribbing. The system’s dynamic response was analysed using FFT analysis and wavelet transform, enabling evaluation of the signal in both the time and frequency domains and capturing non-stationary and transient effects. The results showed that the hybrid metal-damping material structure reduces high-frequency vibration amplitudes primarily at low excitation levels (up to 5g), while its effectiveness decreases at large high-frequency amplitudes (excitation above 10g). Increasing structural stiffness through thicker ribbing led to vibration amplitude reductions of up to 50% within a certain speed range, along with slight shifts in the system’s natural frequencies. The combination of both approaches produced a significant improvement in dynamic behaviour, with the safe operating limit shifted by up to 20%. The proposed design enables effective vibration reduction even under excitation with large high-frequency amplitudes, improves frequency response characteristics, and subsequently allows operation at higher rotational speeds, thereby enhancing overall system performance under demanding conditions.
ACKNOWLEDGEMENTS: The author gratefully acknowledges Technická diagnostika, Ltd. for their cooperation, and the Cultural and Educational Grant Agency of the Ministry of Education, Research, Development and Youth of the Slovak Republic (grant no. 052TUKE-4/2024) and the Slovak Research and Development Agency (grant no. APVV-18-0316) for their financial support.

The superior performance of metal matrix composites (MMCs) makes them highly attractive for demanding applications in the aerospace, automotive, and electronics industries, where they are used in structural components such as aircraft wings, fuselages, and engine parts, as well as in thermal management systems including heat sinks and heat spreaders. In parallel, additive manufacturing (AM) is rapidly transforming materials engineering by enabling the fabrication of complex geometries and tailored microstructures, positioning composite materials at the forefront of next-generation AM technologies. We introduce a novel materials design approach that integrates extrusion-based additive manufacturing with liquid metal infiltration (LMI), a well-established technique for composite fabrication. Beyond single-ceramic systems, multimaterial ceramic composites are also investigated, incorporating reinforcements such as boron carbide (B₄C), silicon carbide (SiC), and aluminum oxide (Al₂O₃). These materials are selected for their complementary properties, including high hardness, wear resistance, thermal stability, and chemical inertness. In addition, aluminum nitride (AlN) is utilized for its high thermal conductivity and electrical insulation capability. When infiltrated with aluminum, the resulting MMCs combine the low density, high specific strength, and corrosion resistance of the metal with the functional and mechanical advantages of the ceramic reinforcements. This study analyzes the feasibility of the process, with particular emphasis on the microstructural evolution at each stage of fabrication.

Magnesium, the lightest structural metal, is attractive for applications ranging from aerospace to biomedicine due to its low density, favorable mechanical properties, and biodegradability. However, its broader utilization is limited by insufficient corrosion resistance associated with the weakly protective oxide surface layer.
While MgO forms spontaneously on magnesium powders, its chemical modification into a more stable surface compound offers a promising pathway for enhanced performance. In this work, we investigated the controlled transformation of naturally formed MgO into a thin MgCO₃ layer using low-temperature RF plasma activation of CO₂. Plasma-assisted processing enables improved reaction control and higher conversion efficiency without thermal treatment.
The influence of reaction gas composition, RF power, and plasma exposure time was systematically optimized to achieve a uniform carbonate layer. The chemical nature of the modified surface was confirmed by X-ray Photoelectron Spectroscopy (XPS). The developed plasma-based approach represents a rapid, controllable, and environmentally friendly method for surface engineering of magnesium powders, offering potential for improved corrosion stability and tailored functional properties.

Lithium-ion batteries employing high-nickel layered oxide cathodes such as NMC811 and Si-graphite anodes offer high energy density but are susceptible to structural degradation during repeated electrochemical cycling [1, 2]. The aim of this work is to investigate morphological and structural changes in an NMC811/Si-graphite electrode system after galvanostatic cycling.
The microstructure of the electrodes before and after 50 charge-discharge cycles was analyzed using scanning electron microscopy in both topographic (LEI) and compositional (COMPO) imaging modes. Elemental distribution was evaluated by energy-dispersive X-ray spectroscopy, while structural changes in the electrode materials were analyzed by X-ray diffraction (XRD).
The pristine Si-graphite anode exhibited a relatively homogeneous morphology with silicon particles uniformly dispersed within the graphite matrix. After cycling, increased surface roughness, local porosity and fragmentation of silicon particles were observed due to repeated volume changes during lithiation and delithiation. Cross-sectional SEM analysis revealed microcracks inside the electrode layer. SEM observations of the NMC811 cathode also showed cracking of secondary particles after 50 cycles, indicating mechanical degradation of the cathode material during cycling.
REFERENCES: [1] Zhang, Y. et al. Aging mechanisms of NMC811/Si-Graphite Li-ion batteries. Journal of Power Sources, 599 (2024) 234159. https://doi.org/10.1016/j.jpowsour.2024.234159; [2] Dubarry, M. et al. Lithium-Ion Battery Degradation: Measuring Rapid Loss of Active Silicon in Silicon-Graphite Composite Electrodes. ACS Applied Energy Materials, 2022. https://doi.org/10.1021/acsaem.2c02047.
ACKNOWLEDGEMENTS: Funded by the EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under the project No. 09I04-03-V02-00046.

Porous metallic lattices produced by additive manufacturing (AM) have garnered significant attention in biomedicine. Among various AM techniques, sinter-based methods that incorporate powder sintering as a final processing step, such as direct ink writing (DIW), provide control over both the material macro - and microporosity. Our previous research has surprisingly shown that the DIW “porous” titanium scaffolds with the 15 % microporosity of strands exhibited an order of magnitude better fatigue life than the “compact” scaffolds with the smaller 6 % microporosity. Therefore, two additional lattices with different microporosities were prepared to optimise the fatigue properties using a robotic deposition system (BSN3D+, Fundació CIM, Spain. The ink comprised spherical Ti powder of 20-63 μm mixed at a 3:1 weight ratio with a 10 wt.% bovine type B gelatine-based binder solution. Printed lattices were dried at room temperature for 12 h, debinded in air at 350 °C for 12 h, and sintered in argon at various temperatures and time periods. The article presents the statistical analysis of porosity and microstructure of four studied lattice filaments with different microporosity, performer using the confocal laser microscope Olympus LEXT™ OLS5100, Japan.

Multiphase high-entropy alloy FeAlCrNiTi0,5 proposed for high-temperature applications was in this study exposed at temperatures up to 1000 °C for 100 h. Oxidation kinetics was evaluated by thermogravimetric analysis, from which the activation energy of oxidation was derived. The microstructures of the samples before and after oxidation and the formed oxide layers were characterized by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy. Also, the microhardness was measured in both the as-cast state and after thermal exposure. These experimental results were compared with other alloys designed for high-temperature applications and it was concluded that further investigation of this alloy system is very promising. Thermo-Calc calculations showed that other concentrations: FeAlCrNi+xTi (x = 1, 4, 7, and 10 at.%) should lead to beneficial fine two-phase structure (BCC+B2). This prediction was confirmed by SEM imaging and the preliminary results also showed excellent thermal stability of these alloys up to 1000 °C. An ongoing work focuses on investigations of oxidation behaviour and microstructural evolution in these materials.

The niobium content influences the mechanical properties and microstructure of metastable beta-titanium alloys. Its influence was systematically studied by means of Vickers microhardness, resonant ultrasound spectroscopy, scanning electron microscopy and electron back-scatter diffraction. With increasing Nb content, the structure transforms from pure alpha, via alpha+beta to pure beta around 40 wt.% Nb. The course of mechanical properties is not monotonous - the elastic modulus decreases with the increasing Nb content; however, it reaches a local maximum around 25 wt.% Nb.

Hydrogen can significantly influence the plastic deformation behaviour of high entropy alloys (HEAs) by altering the dominant deformation mechanisms. In this work, the tensile deformation of a face-centred cubic (FCC) Al0.35CoCrFeNi alloy was investigated using acoustic emission (AE) analysis before and after hydrogen charging, with a focus on statistical evaluation of deformation mechanisms. The mechanical response shows only minor changes after hydrogen charging, with a slight increase in yield strength (Rp0.2 from 214 ± 2 MPa to 228 ± 3 MPa) and ultimate tensile strength (Rm from 576 ± 3 MPa to 587 ± 5 MPa), while ductility remains nearly unchanged (elongation ~65%). Despite these small differences, the AE response reveals a pronounced transition in deformation behaviour. Hydrogen charging under tensile loading leads to a significant increase in AE activity and promotes a transition from twinning-dominated to dislocation-controlled plasticity. This transition is accompanied by a higher occurrence of high-energy AE events, indicating more intense and localized deformation processes. Statistical analysis confirms that these changes are highly significant and that hydrogen markedly increases the likelihood of dislocation-related AE events. The observed behaviour is consistent with Hydrogen Enhanced Localized Plasticity (HELP), suggesting that hydrogen under tensile loading enhances localized dislocation movement while suppressing competing mechanisms such as twinning. These results demonstrate that acoustic emission combined with statistical analysis provides a sensitive and reliable tool for identifying hydrogen-induced changes in deformation mechanisms, even when conventional mechanical properties remain largely unaffected.

This study presents a comparative evaluation of a conventional Cu-based friction material and a newly designed Fe-based composite with reduced environmental impact due to the lower toxicity of iron. Both metal-ceramic materials are widely used in practical applications, particularly in industrial systems such as railway and tram braking systems. The materials were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. Their friction and wear behaviour was experimentally evaluated using a brake dynamometer in accordance with the SAE J2522 test standard, which enables comparison under varying temperatures, initial and final braking speeds, and brake system pressures. The results show that the Cu-based material exhibits a decrease in the coefficient of friction with increasing temperature, declining from approximately 0.47 to 0.37. In contrast, the Fe-based material demonstrates significantly more stable friction behaviour, maintaining a relatively constant average coefficient of friction of around 0.45 over a wide temperature range (80-300 °C at the brake disc). Regarding wear performance, the Fe-based material exhibits a substantial reduction in brake pad wear, achieving up to 50 % lower values compared to the conventional Cu-based material, which also leads to reduced particulate emissions during braking. However, the Fe-based material causes increased wear of the brake disc relative to the Cu-based counterpart. Despite this drawback, the overall results indicate that the Fe-based material provides improved braking performance at elevated temperatures while significantly reducing brake pad wear and eliminating the use of copper. These findings highlight its strong potential as a more environmentally friendly alternative to traditional Cu-based friction materials.

The paper is concerned with the technological peculiarities of the production of copper sheet from CuNiSi alloy by the method of semi-continuous casting and subsequent stages of hot and cold rolling. Pouring defects which have an impact on the copper sheet quality are presented. There was shown that gas pores in a cast billet are among the main causes for appearance of defects in the copper sheets after rolling.
The emphasis is placed on the influence of the secondary cooling rate of the melt in the crystallizer on the change in the size of the liquid phase. It has been established that increasing the cooling water flow rate leads to accelerated formation of a hard crust and a shift of the crystallization front up the casting axis. The established decrease in the depth of the liquid phase favors heat removal in the crystallizer and leads to the production of a casting with reduced porosity.
In the work, a chemical analysis of the cast alloy was performed, the stages of subsequent thermo-mechanical treatment to obtain a copper sheet were traced, a visual and microscopic analysis of the defects observed after rolling was carried out. The quality of the copper sheets obtained by rolling billets crystallized at different secondary cooling rates was established by microstructural and mechanical tests. A technological regime of semi-continuous casting and rolling is proposed, in which a sustainable improved quality of the copper sheet is achieved.

Polyurethane (PU) modelling boards and foams are widely used for manufacturing prototypes, models, and moulds; however, CNC machining generates substantial amounts of fine chips and dust that are typically downcycled or landfilled. This paper presents a mechanically straightforward upcycling route in which PU machining chips are milled, sieved, and re-used as a loose particulate core in carbon/epoxy sandwich composites. The sandwich panels were manufactured by hand lay-up with vacuum assistance or by vacuum infusion to keep the process low-tech and readily transferable to prototyping practice. Flexural behaviour was assessed by three-point bending in accordance with ISO 178, and the results were interpreted using load-deflection responses complemented by macroscopic inspection and fractographic evaluation of failed specimens. A characteristic sandwich response was observed, with damage initiation in the core (shear and local densification) followed by a transfer of load being carried predominantly by the facesheets. The discussion shows that mechanical stability is particularly sensitive to the homogeneity of the particulate layer, local porosity, and the degree of matrix infiltration, which together govern the core shear capacity and the adhesion at the facesheet-core interface. The proposed approach demonstrates the material potential of recycled PU chips for lightweight composite panels and identifies key optimisation directions to improve process repeatability and scalability in model and mould manufacturing. The concept leverages the fact that the flexural stiffness and strength of a sandwich are primarily determined by the facesheets, whereas the core обеспечивает shear transfer and stabilisation. Overall, the study contributes to circular-economy strategies for modelling materials and highlights practical pathways for value-added utilisation of waste PU fractions.