POSTER SESSION

Magnesium alloys, known for their excellent strength-to-weight ratio, are emerging as promising materials in the automotive and aerospace industries. However, due to their high reactivity with oxygen, low ignition temperature and rapid degradation of mechanical properties at elevated temperatures, their applications are limited. In this study, we explored three magnesium alloy systems enriched with rare earth (RE) elements and calcium: Mg-4.5Gd-3.4Y-2.6Ca, Mg-2Y-2Gd-1Ca, and Mg-4Ca-1Y (weight %). These alloys were prepared through casting and then extruded at temperatures of 300°C, 350°C, and 400°C, with extrusion ratios of 11 and 25. This approach allowed us to examine the effects of both composition and processing techniques on the materials. The microstructure primarily consisted of a solid solution of magnesium and the Mg2Ca phase, along with minor amounts of RE-hydrides, RE-oxides, and Mg-RE particles. Notably, extrusion at 400°C resulted in a larger grain size (5.5 μm) compared to lower extrusion temperatures (around 2.5 μm). The obtained results showed the exceptional ignition resistance of these alloys. The ignition temperature ranged from approximately 950°C for Mg-2Y-2Gd-1Ca to over 1100°C for Mg-4.5Gd-3.4Y-2.6Ca and Mg-4Ca-1Y. This high resistance results from the synergistic effects of Y, Gd, and Ca oxides. Compression tests revealed alloys with higher RE content exhibited superior mechanical properties compared to those with more calcium. However, Mg-4Ca-1Y still achieved remarkable ignition resistance. This work was supported by GACR, project no. 22-22248S, and by Specific university research, project No. A1_FCHT_2024_007.

The aim of our study was to perform a metallographic analysis of a thick-walled plate made of powdered austenitic steel AISI316L by direct energy deposition (DED) technology. After the plate was manufactured, it was heat treated and surface machined. The metallographic analysis performed consisted of the analysis of samples taken in different areas of the plate and in different directions with respect to the printing axes. The structure of the collected samples was evaluated by light and scanning electron microscopy. Thanks to the analysis carried out, it was possible to indicate that pores as large as hundreds of micrometres were present in the plate structure. On the inner edge of the pores there were oxide envelopes with a higher proportion of chromium and manganese. The chemical composition of the matrix was homogeneous. Hardness and grain size were similar in the areas evaluated.

This study investigates additive manufacturing methods for Nitinol, a shape memory alloy extensively used in medical and aerospace applications. It focuses on the relationship between mechanical properties and process parameters in the additive manufacturing of Nitinol. Through a comprehensive review of existing literature, we analyze how variations in parameters such as laser power, scanning speed, and layer thickness influence the tensile strength and elongation of additively manufactured Nitinol components. The mechanical properties resulting from different methods and specific process parameters are summarized, and the correlation between these parameters and mechanical properties is evaluated. Our findings indicate that mechanical performance can be fine-tuned by balancing process parameters. While effective results are achievable within certain parameter ranges, each application requires a specific balance to meet its unique material property demands.

Eutectoid steels offer significant advantages in terms of high strength, ductility, toughness and wear resistance. In addition to these properties, they can be used as a cheaper alternative to high-strength low-alloy (HSLA) steels in industrial applications where weldability is not a critical factor. Eutectoid steels (C67) consist of a pearlitic structure containing layered cementite and ferrite phases. Annealing of eutectoid steels at high temperatures spheroidizes the pearlitic structure and increases the distance between layers. The spheroidization process ensures that the layered pearlitic cementite grains, which have a hard and brittle structure, become rounder and more homogeneous. In this way, the machinability value of steel increases.
This study examines the effects of heat treatment (annealing) and cold deformation (cold rolling) on the temperature and duration parameters applied to C67 steel. The aim of the applied heat treatment and cold deformation processes is to achieve spheroidization in the pearlitic structure. The spheroidization process is applied to improve the mechanical properties of the steel, enhance its machinability to be able to reduce material thickness. In this study, experiments were conducted using different levels of deformation 0%, 10%, 20%, 30%, 40% cold reductions by rolling) of 2 mm thickness sheet steel, various spheroidization temperatures (700-730°C), and durations (1-10 hours) in laboratory scale furnace. After heat treatment microstructure of steel samples were examined by SEM and spheroidized volume fraction was determined by image analysis. Tensile and hardness tests were applied for mechanical properties and work hardening behavior of heat-treated samples were compared.
The results obtained show that the level of deformation is related to the spheroidization temperature and duration. Notably, increasing levels of deformation result in successful spheroidization at lower temperatures and shorter durations. This study provides valuable insights into the heat treatments of C67 grade steels, contributing to more efficient production processes.

The authors gratefully acknowledge Nur Sena GÖKALP for her invaluable assistance in laboratory work.

The article is aimed on material behaviour of GOST 08CH18N10T stainless steel and its changes due to thermal aging influence. The study summarizes material properties, particularly material changes in impact energy measured on small notched specimens at various temperatures and in thermo-electric force measurements. The testing material involves initial states of stainless steel, material thermally aged in laboratory conditions and material after 28 years of operation in power plant conditions. The influence of chemical composition and microstructure is discussed.

Selective Laser Melting (SLM) is a leading additive manufacturing technique for producing metallic components with complex geometries and superior properties. SLM builds parts layer-by-layer using high energy laser beams, which offers higher flexibility compared to the conventional process like casting. The rapid heating and cooling rates in SLM result in distinctive microstructures, which can significantly enhance the mechanical properties of the components. Additionally, SLM parts typically require minimal post-processing, making the process thus very efficient.

However, one of the well-known problems of SLM is the relatively poor surface quality compared to conventional methods, which leads to decreased mechanical strength and reduced long-term stability. As a result, the widespread adoption of SLM technology is limited to those familiar with the technology.

This poster presents the initial results from our research collaboration, including surface modifications achieved by optimizing laser scanning speed and other parameters. The preliminary data indicate a substantial improvement in surface roughness compared to initial results. We also discuss future plans and the broader implications of our findings.

The project AM-Surf is the cooperation between Germany and Czech Republic. The main focus of this project is the improvement of surface quality from metallic 3D printing. Through this interdisciplinary and cross-border collaboration between the three research institutions COMTES FHT, OTH Amberg-Weiden and TH Deggendorf, we could transfer the promising results from scientific research to the industrial application by the assistance of Klastr Mechatronika.

The DELISA-LTO (DEscription of the extended LIfetime and its influence on the SAfety operation and construction materials performance - Long Term Operation with no compromises in safety) project is part of the HORIZON-EURATOM-NRT-01 call. This four-year project (2022-2026) is focused on WWER-type (eastern) reactors. DELISA-LTO offers a unique opportunity to obtain and analyze components from selected decommissioned Nuclear Power Plants (NPPs). The primary goal of the DELISA-LTO project is to gain a detailed understanding of material degradation phenomena, such as thermal aging and swelling, which are significant degradation processes in the structural materials of nuclear power plants. Experimental techniques, such as mechanical testing and non-destructive testing (NDT) methods, will be employed to deepen the understanding of material degradation. The knowledge gained will be critical for ensuring Long Term Operation (LTO) in existing NPPs that are considering extending their lifetimes. Initially, the project planned to use materials harvested exclusively from the decommissioned Jaslovske Bohunice NPP (WWER 440 V230 type, Slovakia - Unit 1 and Unit 2, which operated for 28 years). However, during the first year, the project's scope expanded to include primary circuit components from other NPPs, such as Paks NPP (Hungary) and WWER 1000 type reactors in Ukraine. The materials are evaluated both in their initial state and after long-term operation, and will also undergo thermal aging simulations replicating NPP operation for at least 60 years. Collaborating partners developed an Experimental Matrix that integrates participating laboratories, materials in various states, testing methods, specimen types, and geometries.

This contribution presents advanced methodologies for assessing the operational integrity of mast structures, with a particular emphasis on detecting hidden defects. Among the promising techniques investigated, thermographic analysis emerges as an effective tool for identifying defects such as cracks, laps from the steel profile manufacturing process, large inclusions, and other anomalies hidden beneath several layers of coatings. The study explores the potential of both passive and active thermography, demonstrating their applicability in field measurements. Measurements involving a thermal camera and induction excitation were conducted from a large truck-mounted platform. The research is also advancing towards the automation of field applications, considering various carriers for the thermal camera and excitation systems, including drones, climbers, and robotic systems capable of traversing mast structures. Potential excitation sources include induction, flashes, lasers, and ultrasound. Complementary monitoring techniques such as strain gauge methods and potential methods, along with the analysis of small material samples for evaluating current mechanical properties using miniature test specimens, will also be utilized. This comprehensive approach enhances the reliability and safety of mast structures in power systems.

Transformers play a crucial role in electric energy transmission and distribution. Despite their efficiency, a part of the energy is lost due to heat conversion. Those losses negatively affect the insulation system and therefore the overall transformer life cycle and performance. Cast resin transformers are operated in protective enclosures, which prevents water and foreign body ingress to live parts. The enclosure is negatively influencing the insulation system due to worse thermal dissipation. Therefore, for proper design of transformers the exact modelling of thermal behaviour is necessary.
This paper summarises of digital twin modelling of the transformer and enclosure coupled task. In the first step the enclosure simplified model was manufactured and the ventilation for different protection classes of the ventilation openings were measured. As per IEC 60076-10 a transformer enclosure should have at least one inlet and one outlet opening on opposite sides. In real applications the enclosure has more then one inliet and outlet opening from all sides, therefore a simplification was done to reproduce this minimal requirement of the standard and enable easier preparation of virtual computing models for the first validation.
In the second step, a computer model was established, and thermal dissipation was analyzed using a CFD tool using the temperature mapping received from the previous step. This approach helps to better understand the ventilation of the transformer enclosures and at the same time to provide an experience base for setting the boundary conditions in the CFD simulation for another geometries and more complex applications.

This study evaluates the potential of Alumina-Forming Austenitic (AFA) steels, containing 2-5% aluminum, derived from SS 310S, as high-temperature corrosion-resistant materials for Supercritical Water Reactors (SCWR) and Small Modular Reactors cooled by Supercritical Water (SCW-SMR) under simulated accident conditions. AFA steels exhibit high-temperature corrosion resistance through alumina (Al₂O₃) scale formation and enhanced mechanical strength via precipitation hardening, with key strengthening phases including NbC, Laves phase, and B2-NiAl. As part of the international ECC SMART project which aims to develop SCW-SMR, flat coupons were exposed to water at the reactor’s inlet temperature of 380 °C and 25 MPa for 1000 hours, where water properties change drastically. The exposed samples were analyzed using SEM-EDS/EBSD to evaluate the bulk material microstructure and to determine the corrosion layer. Based on weight gain and the absence of significant layer formation, a very low corrosion rate was detected, with the calculated wall penetration depth after 30,000 hours of the fuel cycle indicating the alloy's long-term corrosion stability.

WAAM (Wire and Arc Additive Manufacturing) is very popular technology for the production of metal parts and components, which finds application especially in the aviation industry. Compared to conventional methods of manufacturing selected components, WAAM can significantly reduce the BTF (Buy-to-Fly) ratio. The current research is focused on non-contact temperature measurement with a FLIR E95 thermal imaging camera on additively manufactured components from AA5087 aluminium alloy in CMT (Cold Metal Transfer) mode. The main content of the research is the measurement of emissivity in depenence on the TS (Travel Speed) setting. Emissivity is an integral part of temperature calculation in non-contact measurement. The determination of emissivity was carried out according to the ČSN EN ISO 18434-1 standard. The value of the TS generally affects the width and height of the weld bead. With increasing TS, the width and height of the weld bead decrease and the surface appearance also changes. The research results showed that the TS has important influence on the surface emissivity value.

Enhancing traditional materials' mechanical properties can be achieved by adding ultrafine oxide particles to inhibit dislocation movement, thus increasing strength. This technique applies to austenitic steels, improving their strength and high-temperature resistance. Understanding oxide dispersion in metal alloys is crucial for developing new high-strength materials. Tin the study we prepared oxide dispersion-strengthened austenitic stainless steel 316L by mechanically alloying of steel powder with Y2O3. Powder precursors were consolidated using Spark Plasma Sintering (SPS) and Pulse Plasma Sintering (PPS) and analyzed for their microstructure. The mechanical properties of the resulting compacts were then evaluated. Initial findings show the formation of chromium-containing carbides due to minor carbon diffusion from graphite tools during SPS or PPS. Y2O3 particles were successfully incorporated into the matrix during mechanical alloying. The mechanical properties varied based on chemical composition and specific conditions of consolidation. Materials with uniformly distributed Y2O3 particles were successfully created using powder metallurgy. Future research will aim to optimize SPS conditions to prevent carbide formation.
This work was supported by the Czech Science Foundation, project no. 22-04227L.

The Lamb wave structural monitoring method is characterized by high sensitivity and online monitoring capabilities and can be used to simultaneously study large areas of composite structures. The disadvantages of the method in comparison with traditional ultrasonic testing include the presence of significant dispersion, namely the dependence of the wave speed on frequency, mode type and thickness of the composite material sample. Numerical estimates of experimentally measured group velocities of Lamb waves in composite materials with anisotropic characteristics do not coincide with theoretical estimates of group velocities obtained based on the dispersion equation. The presence of a nonzero angle between the directions of the group and phase velocity vectors is the main reason for the mentioned discrepancy between experimental and analytical estimates of group velocities. The main goal of this work is to study the propagation characteristics of Lamb waves in composite samples, primarily such as group velocity and characteristic wave curve. As one of the main results, a reliable method for separating symmetric and antisymmetric wave modes is proposed, based on imposing boundary conditions on the middle plane of a sample of symmetric laminates. A detailed analysis of the dispersive and anisotropic behavior of Lamb waves in two different types of symmetrical laminates was performed. A study of Lamb wave dispersion was performed for a set of ten symmetric and asymmetric modes. The presence of interaction of fundamental modes with composite layers in the low-frequency range is confirmed by the absence of a cutoff frequency for fundamental modes. A high level of group velocity dispersion was found for the SH0 and S0 modes.

To obtain a permission to construct HLM (heavy liquid metal) cooled reactors, it must be demonstrated that the components will retain their structural integrity and functionality over their design life. Design and engineering data, such as the resistance of construction materials, is based on comprehensive testing programs and evaluation and analysis by experts. To demonstrate the integrity of materials and components for structural applications, their performance under the appropriate environmental conditions must be evaluated. Relevant properties need to be measured and assessed. Furthermore, the factors affecting material performance are specific for each material-environment combination.
The objective of this paper is to introduce a research infrastructure for material research in heavy liquid metals. This also includes the technical specification of individual devices and their operational possibilities. Two experimental devices were designed for HLM research. The MATLoo loop was designed for materials research in liquid lead and has environments in a non isothermal forced circulation. The Static tanks were designed for corrosion tests in static environment of liquid Pb.
Both experimental facilities are operated as part of the Large Research project Infrastructures of the Czech Republic - Czech International Center of Research Reactors (CICRR). Czech International Centre of Research Reactors (CICRR) consists of two existing large research infrastructures from the Czech roadmap - Reactors LVR-15 and LR-0 and JHR-CZ. The system of the supporting laboratories, hot cells, loops, and other analytical and research facilities. This project offers the use of research infrastructure, including personnel to ensure operation given infrastructure, subject to open access.

Cold spray is currently the fastest developing heat spray technology. Its unique properties allow it to be used in applications where other thermal spray technologies cannot be used. An example of such an application is 3D printing. The kinetic bonding and parameter optimization allows Cold Spray technology to deposit any thicknesses and geometries of coatings. Due to the uneven distribution of the particles, the material increase corresponding to the Gaussian curve during spraying. For this reason, it is necessary to optimize the process parameters. This property of Cold spray technology limits its ability to create precise geometries, and thus also its possibility of use in 3D printing. The aim of the work is the analysis and proposal of a solution to this issue. Part of the work is the design of a side spraying strategy to compensate for uneven material growth. The coating materials used for the experiment were pure Cu and Inconnel 625. Aluminum was chosen as the material of the underlying substrate. High-pressure cold spray Evo CSII from Impact was used. In the case of the Cu coating, due to the optimization of the process parameters, unevenness with increasing thickness was successfully compensated. In the case of Inconel 625, the underlying substrate was deformed due to thermal stress. The quality of the deposited materials was evaluated through microstructure analysis.

Small punch testing is a well-established testing technology in situations where only tiny fragments of material are at disposal. In addition to the identification of the basic characteristics of the material, the ductility is an important output of such testing. Many existing ductile fracture models could be used for such identification, but the simplicity of the model is, in addition to its reliability, an important feature. The reason is that a limited number of experiments with the same type of specimen prevents the reliable identification of sophisticated ductile fracture models with many material parameters. That is why the work is focused on simple one-parameter criteria such as Rice and Tracey dependent on stress triaxiality, or Cockroft-Latham-Oh related to maximum principal stress, normalized by the equivalent stress. These are calibrated first by notched cylindrical specimens loaded in tension only and second by a set of broader variety of experiments under different stress states. The results of both the ductile fracture models and identification strategies with respective material constants are then applied to the numerical simulation of the small punch testing with element erosion to see their predictability of crack formation and propagation.

This report develops non-contact optical methods for measuring concrete cracks for remote
diagnostics of hard-to-reach building surfaces using unmanned aerial vehicles. The drone's high-
resolution digital camera captures remote close-up photography of the concrete surface under high light
intensity levels. National Instrument hardware and NI LabVIEW software modules have also been
developed for the geometrical method determination of cracks in building structures and for drone
control and communication. Use of the newest optical matrices with high resolution of 102 megapixels
of the Samsung Electronics Company and special lenses allows increasing metrological accuracy to ± 3%
of measurements of geometrical parameters of cracks in concrete. The digital image of the crack
converted in a data matrix, each element of which contains information about the level of reflected light
from the concrete surface and the crack. Using the formulas obtained by us earlier, with the help of
computer processing of the image, the morphology of the crack in real geometrical dimensions can be
calculated. Using special tools computer programs, the crack’s geometrical parameters can be measured
maximal accurately as possible. The proposed remote optical method for non-contact detection of cracks
in concrete when photographing with a drone from a close distance allows achieving an accuracy of
measuring its depth of 7%.

3D printing of materials is currently one of the intensively developing production areas of components and parts. There are also places of application of various printing technologies in the energy sector. For future use in the field, it is necessary to qualify not only the printing process itself, but also to verify the applicability of one of the most widely used methods of non-destructive testing (NDT) of ultrasound for the inspection of printed materials. As part of the TAČR TN02000012/8 NCK II: CANUT II - DP020201 Additive repair technologies project, plates made of austenitic steel 316L, one of the materials widely used in printing, were printed. Printing was done through two different technologies, one of which is Direct Energy Deposition (DED) and the other is Wire Laser Additive Manufacturing (WLAM). From the point of view of ultrasonic testing (UT), the properties were measured at selected points and directions using the Pulse-Echo technique (PEUT) and subsequently the detection of possible internal defects was performed using the phased array technique (PAUT) together with the detection of artificial side-drilled holes defects in the manufactured gauges.

Interest in hydrogen applications and their development is increasing, as it is a clean energy source with high energy density. Many different metallic components, such as pressure vessels, fittings, valves, and electrolyzers, must be designed to withstand hydrogen pressure. Therefore, there is widespread interest in developing cost-effective medium- and high-strength materials capable of safely storing and transporting hydrogen. This paper examines two testing methods for measuring mechanical properties in environments that cause hydrogen embrittlement of materials. Steel 42CrMo4 was used to determine the effects of hydrogen embrittlement.
The first method involves in-situ electrolytic tests that simulate the environment of hydrogen production electrolyzers. In this method, the test tensile specimen is placed in a testing machine equipped with an electrolyte container. During testing, the specimen serves as the cathode, and a Pt electrode is used as the anode. The passage of direct current through the electrolyte results in the formation of hydrogen on the test specimen and its simultaneous saturation with hydrogen.
The second method studied involves tensile tests using hollow specimens filled with gaseous hydrogen at pressures up to 200 bar. This method simulates the effects of hydrogen embrittlement in pressure vessels and fittings. It realistically simulates hydrogen concentration gradients in the walls of pressure vessels and piping systems, increasing the relevance of the obtained data.