Publikační činnost Katedry materiálového inženýrství a recyklace / Publications of Department of Materials Engineering and Recycling (653)

Permanent URI for this collectionhttp://hdl.handle.net/10084/146154

Kolekce obsahuje bibliografické záznamy publikační činnosti akademických pracovníků Katedry materiálového inženýrství a recyklace (653) v časopisech registrovaných ve Web of Science od roku 2022.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

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A review on additive manufacturing methods for NiTi shape memory alloy production
(MDPI, 2024) Kubášová, Kristýna; Drátovská, Veronika; Losertová, Monika; Salvetr, Pavel; Kopelent, Michal; Kořínek, Filip; Havlas, Vojtěch; Džugan, Ján; Daniel, Matej
The NiTi alloy, known as Nitinol, represents one of the most investigated smart alloys, exhibiting a shape memory effect and superelasticity. These, among many other remarkable attributes, enable its utilization in various applications, encompassing the automotive industry, aviation, space exploration, and, notably, medicine. Conventionally, Nitinol is predominantly produced in the form of wire or thin sheets that allow producing many required components. However, the manufacturing of complex shapes poses challenges due to the tenacity of the NiTi alloy, and different processing routes at elevated temperatures have to be applied. Overcoming this obstacle may be facilitated by additive manufacturing methods. This article provides an overview of the employment of additive manufacturing methods, allowing the preparation of the required shapes of Nitinol products while retaining their exceptional properties and potential applications.
Effect of change in current density on hydrogen embrittlement of advanced high-strength steel S960MC during hydrogenation
(Univerzita Jana Evangelisty Purkyně v Ústí nad Labem, 2024) Drímalová, Petra; Nový, František; Uhričík, Milan; Váňová, Petra; Šikyňa, Lukáš; Chvalníková, Veronika; Slezák, Martin
Hydrogen embrittlement involves the interaction between hydrogen and the microstructure of metals, which can lead to an alarming loss of mechanical properties. For advanced high-strength (AHS) steel S960MC grade, which finds application in fields ranging from heavy machinery to construction, understanding this phenomenon is important. The material's complex crystalline lattice, carefully engineered to maximize strength, becomes vulnerable in the presence of hydrogen. The sources of hydrogen that can lead to embrittlement of steel are various. From the exposure of steel to hydrogen during production processes to the absorption of hydrogen from the environment. After the absorption of hydrogen into the material, hydrogen atoms diffuse in the microstructure and look for places with high stress concentration (cracks, inclusions, grain boundaries, etc.). In these regions, atomic hydrogen disrupts interatomic bonds, weakening the material and making it susceptible to embrittlement and subsequent complete failure of the component. This research is focused on how the change in current density affects the hydrogen embrittlement of AHS steel S960MC during hydrogenation. It was found that the mechanical properties of steel decrease at a lower current density, but not to the same extent as at a higher current density. Thus, it can be said that the change in current density influences the hydrogen embrittlement of S960MC steel.
Analysis of hydrogen in a hydrogenated, 3D-printed Ti–6Al–4V alloy by glow discharge optical emission spectroscopy: sample heating effects
(Royal Society of Chemistry, 2024) Weiss, Zdeněk; Čapek, Jaroslav; Kačenka, Zdeněk; Ekrt, Ondřej; Kopeček, Jaromír; Losertová, Monika; Vojtěch, Dalibor
Depth profile analysis of a hydrogenated Ti–6Al–4V alloy by glow discharge optical emission spectroscopy (GDOES) is described. Besides the earlier reported ‘hydrogen effects’, causingchanges in emission intensities of other elements if hydrogen is present, the analysis of hydrogen itself was found to be affected by the redistri bution of hydrogen inthe region adjacent to the analyzed spot, due to sample heating and the thereby increased hydrogen diffusivity. A simple model of heat transfer within the sample during the GDOES analysis is proposed and the surface temperature of the analyzed spot is estimated to be z365 °C, in the given experimental setup.
Creep behaviour and microstructure evolution in Super 304H–P92 heterogeneous welds
(Taylor & Francis, 2023) Vodárek, Vlastimil; Kuboň, Zdeněk; Palupčíková, Renáta; Hradečný, Kryštof; Váňová, Petra
The paper deals with results of long-term stress rupture tests on "cross-weld" specimens made of Super 304 H - P92 heterogeneous welds. Stress rupture tests were carried out at temperatures of 625 degrees C and 650 degrees C up to 20,000 hours to rupture. Creep rupture strength and WSF values of Super 304 H - P92 welds for 10,000 hours at both 625 degrees C and 650 degrees C were calculated. The preferential location of failure was the intercritical part of the heat affected zone in P92 steel. Hardness of both base materials did not show significant changes during creep exposure at both 625 degrees C and 650 degrees C. However, gradual hardening of the weld metal occurred. Metallographic studies were performed in individual parts of heterogeneous welds. A special attention was paid to precipitation reactions in both base materials and heat affected zones. A residual content of vanadium in Super 304 H steel affected precipitation processes. Vanadium partly substituted niobium in the modified Z-phase ((V,Nb)CrN).
Influence of ion nitriding on microstructure and properties of Haynes 282 nickel superalloy specimens produced using DMLS technique
(MDPI, 2023) Sitek, Ryszard; Kulikowski, Krzysztof; Paradowski, Krystian; Gancarczyk, Kamil; Losertová, Monika; Kobayashi, Akira; Moneta, Joanna; Kamiński, Janusz
The paper investigates the influence of the ion-nitriding process on the microstructure, corrosion resistance, and tensile strength at elevated temperatures of Haynes 282 nickel superalloy specimens produced by the Direct Metal Laser Sintering (DMLS) technique. The study was performed for two conditions, i.e., as-built by DMLS method and as-built by DMLS method + covered by a layer containing CrN + Cr2N phases. An analysis of the surface morphology revealed that the ion-nitriding process significantly affects the physical and chemical phenomena occurring on the specimen’s surface. The XRD measurement of the specimens showed that preparing them with the DMLS method as well as following a nitriding process produced residual tensile stresses. Based on the measurement of the nanohardness distribution through the layer approximatively of 7 µm in width and the superalloys substrate, the results of the nanohardness showed the maximum values of 27 GPa and 13.5 GPa for the nitrided layer and the substrate, respectively. The surface protection from the nitrided layer proved a positive effect on the corrosion resistance of the DMLS specimens in the solution of 0.1 M Na2SO4 + 0.1 M NaCl at room temperature. The results of the tensile tests at 750 ◦C showed that the ion-nitriding process did not significantly affect the elevated-temperature tensile strength of the superalloy specimens produced with the DMLS technique.
Comparison of continuous and pulsating water jet during piercing of ductile material
(MDPI, 2023) Nag, Akash; Srivastava, Madhulika; Petrů, Jana; Váňová, Petra; Srivastava, Ashish Kumar; Hloch, Sergej
More efficient ways to process materials are constantly being sought, even in the case of continuous water flow technology, which acts on materials mainly by stagnant pressure. An alternative method is an ultrasound-stimulated pulsating water jet, the basis of which is the repeated use of impact pressure, which reduces the time interval for mechanical relaxation. This article focuses on a comparative study from the point of view of water mass flow rate on material penetration and its integrity. Relatively low pressures (p = 20, 30, and 40 MPa) with varying nozzle diameters (d = 0.4 and 0.6 mm) were used to identify the effectiveness of the pulsating water jet. The time exposure of the jet at a fixed place was varied from t = 0.5 to 5 s for each experimental condition. The results showed that with an increase in the pressure and diameter values, the disintegration depth increased. In addition, the surface topography and morphology images showed signs of ductile erosion in the form of erosion pits, upheaved surfaces, and crater formation. The microhardness study showed an increase of 10% subsurface microhardness after the action of the pulsating water jet as compared to the original material.
The effect of vanadium on modified Z-phase characteristics in austenitic steels
(MDPI, 2023) Vodárek, Vlastimil; Holešinský, Jan; Kuboň, Zdeněk; Palupčíková, Renáta; Hradečný, Kryštof; Váňová, Petra; Hlinka, Josef
In austenitic steels, the tetragonal Z-phase (NbCrN) has frequently been credited with beneficial strengthening effects during dislocation creep. In the modified Z-phase, niobium is partially substituted by vanadium. The basic objective of this contribution is a detailed characterization of the modified Z-phase in vanadium bearing austenitic AISI 316LN+Nb+V and HR3C steels. Experimental activities were focused on crystallography, thermodynamic and dimensional stability, kinetics of precipitation (TTP diagram) and solvus temperature of the modified Z-phase in the steels examined. Thermodynamic modelling was used for prediction of stable minor phases and solvus temperature of the modified Z-phase. Kinetics of precipitation of the (Nb,V)CrN phase in the AISI 316LN+Nb+V steel was experimentally investigated in the temperature interval of 550–1250 ◦C. The kinetics of precipitation of the modified Z-phase in austenitic matrix was fast. Results of diffraction studies on particles of the modified Z-phase confirmed the existence of the tetragonal unit cell already after short-term annealing. The solvus temperature of the modified Z-phase in austenitic steels was determined to be lower than that for the NbCrN phase. The decrease in the solvus temperature is dependent on the vanadium content in austenitic steels. Both thermodynamic calculations and experimental results proved that the thermodynamical stability of the modified Z-phase in austenite was high. More data are needed for evaluation of long-term dimensional stability of the (Nb,V)CrN phase in austenitic steels at temperatures for their engineering applications.
Rheological characteristics of Fe–C–Cr(Ni) alloys
(MDPI, 2023) Rosypalová, Silvie; Řeháčková, Lenka; Novák, Vlastimil; Kawuloková, Monika; Váňová, Petra; Konečná, Kateřina; Ďuricová, Barbora
The principal objective of this project was to investigate the rheological properties of Fe–C– Cr and Fe–C–Ni-based low-alloy steels using an Anton Paar high-temperature rotational viscometer up to 1550 ◦C. The emphasis was placed on determining the liquidus temperatures and evaluating the flow and viscosity curves and the temperature dependence of dynamic viscosity. All were studied depending on the change in the content of chromium (0.010–4.863 wt%), nickel (0.001–4.495 wt%), and carbon (0.043–1.563 wt%). It was shown that the dynamic viscosity decreases with increasing nickel content and increases with increasing carbon and chromium content. The experimental data of the flow curves were fitted using the Herschel–Bulkley model with a good agreement between the measured and calculated values. Characterization of the internal structure was performed by SEM and EDX analyses, confirming non-significant changes in the microstructure of the original and remelted samples. The phase composition of the selected samples was also determined using JMatPro 12.0 simulation software (Sente Software Ltd., Guildford, UK).
Broadband Mueller ellipsometer as an all-in-one tool for spectral and temporal analysis of mutarotation kinetics
(Royal Society of Chemistry, 2023) Vala, Daniel; Mičica, Martin; Cvejn, Daniel; Postava, Kamil
Spectroscopic Mueller matrix ellipsometry is becoming increasingly routine across physical branches of science, even outside optics. The highly sensitive tracking of the polarization-related physical properties offers a reliable and non-destructive analysis of virtually any sample at hand. If coupled with a physical model, it is impeccable in performance and irreplaceable in versatility. Nonetheless, this method is rarely adopted interdisciplinarily, and when it is, it often plays a supporting role, which does not take benefit of its full potential. To bridge this gap, we present Mueller matrix ellipsometry in the context of chiroptical spectroscopy. In this work, we utilize a commercial broadband Mueller ellipsometer to analyze the optical activity of a saccharides solution. We verify the correctness of the method in the first place by studying the well-known rotatory power of glucose, fructose, and sucrose. By employing a physically meaningful dispersion model, we obtain 2π-unwrapped absolute specific rotations. Besides that, we demonstrate the capability of tracing the glucose mutarotation kinetics from just one set of measurements. Coupling the Mueller matrix ellipsometry with the proposed dispersion model ultimately leads to the precisely determined mutarotation rate constants and spectrally and temporally resolved gyration tensor of individual glucose anomers. In this view, Mueller matrix ellipsometry may stand as an offbeat yet equal technique to those considered classical chiroptical spectroscopy techniques, which may help open new opportunities for broader polarimetric applications in biomedicine and chemistry.
Microstructure evolution in a GOES thin strip
(MDPI, 2023) Volodarskaja, Anastasia; Hradečný, Kryštof; Palupčíková, Renáta; Váňová, Petra; Vodárek, Vlastimil
This paper focuses on the evolution of the microstructure in a grain-oriented electrical steel (GOES) thin strip after casting. After solidification, the microstructure consisted of delta-ferrite. A small fraction of austenite was formed during the cooling of the thin strip in the two-phase region (gamma+delta). Fine Cr2CuS4 particles precipitated in the ferrite and along the delta/gamma interfaces. Laths of primary Widmanstätten austenite (WA) nucleated directly on the high-angle delta-ferrite grain boundaries. The formation of WA laths in both adjacent ferritic grains resulted in a zig-zag shape of delta-ferrite grain boundaries due to their local rotation during austenite nucleation. Based on the EBSD results, a mechanism of the formation of the zig-zag grain boundaries has been proposed. Besides the Widmanstätten morphology, austenite also formed as films along the delta ferrite grain boundaries. Sulfide precipitation along the delta/gamma interfaces made it possible to prove that austenite decomposition upon a drop in temperature was initiated by the formation of epitaxial ferrite. Further cooling brought the decay of austenite to either pearlite or a mixture of plate martensite and some retained austenite.
Electrochemical, biological, and technological properties of anodized titanium for color coded implants
(MDPI, 2023) Hlinka, Josef; Dostálová, Kamila; Čabanová, Kristina; Madeja, Roman; Frydrýšek, Karel; Koutecký, Jan; Rybková, Zuzana; Malachová, Kateřina; Umezawa, Osamu
Anodization coloring of titanium tools or implants is one of the common methods for the differentiation of each application by its size or type. Commercial purity titanium grade 4 plates (50 × 20 × 0.1 mm) were tested to obtain their electrochemical and other technological properties. The coloring process was done using the potential of 15, 30, 45, 60, and 75 Volts for 5 s in 1 wt. % citric acid in demineralized water solution. Organic acids solutions generally produce better surface quality compared to inorganic acids. The contact angle of colored surfaces was measured by the sessile drop method. Electrochemical impedance spectroscopy and potentiodynamic polarization were used for the determination of selected electrochemical and corrosion parameters of the tested surfaces. It was found that the anodization process decreases corrosion potential significantly. It was also confirmed that a higher potential used for anodization results in higher polarization resistance but also a decrease in corrosion potential. The anodization process at 75 V produces surfaces with the lowest corrosion rate under 1 nm/year and the noblest corrosion potential. It was confirmed that the anodization process in citric acid does not affect titanium cytotoxicity.
Acoustic emission signal characterisation of failure mechanisms in CFRP composites using dual-sensor approach and spectral clustering technique
(MDPI, 2023) Šofer, Michal; Šofer, Pavel; Pagáč, Marek; Volodarskaja, Anastasia; Babiuch, Marek; Gruň, Filip
The characterisation of failure mechanisms in carbon fibre-reinforced polymer (CFRP) materials using the acoustic emission (AE) technique has been the topic of a number of publications. However, it is often challenging to obtain comprehensive and reliable information about individual failure mechanisms. This situation was the impetus for elaborating a comprehensive overview that covers all failure mechanisms within the framework of CFRP materials. Thus, we performed tensile and compact tension tests on specimens with various stacking sequences to induce specific failure modes and mechanisms. The AE activity was monitored using two different wideband AE sensors and further analysed using a hybrid AE hit detection process. The datasets received from both sensors were separately subjected to clustering analysis using the spectral clustering technique, which incorporated an unsupervised k-means clustering algorithm. The failure mechanism analysis also included a proposed filtering process based on the power distribution across the considered frequency range, with which it was possible to distinguish between the fibre pull-out and fibre breakage mechanisms. This functionality was particularly useful in cases where it was evident that the above-mentioned damage mechanisms exhibited very similar parametric characteristics. The results of the clustering analysis were compared to those of the scanning electron microscopy analysis, which confirmed the conclusions of the AE data analysis.
Processing of metal waste-sludge from the galvanizing plants
(MDPI, 2022) Drápala, Jaromír; Rigoulet, Hana; Brožová, Silvie; Malcharcziková, Jitka; Langová, Šárka; Vontorová, Jiřina; Nétek, Václav; Kubáč, Jaroslav; Janáček, Dominik
This paper deals with the possibility of obtaining zinc from waste galvanic sludge, which is formed during galvanic plating. The aim of the experimental and practical part was to obtain zinc after the leaching of galvanic sludge. Leaching was performed in sulfuric acid, nitric acid and hydrochloric acid at different temperatures and time intervals with the addition of oxidizing agents as hydrogen peroxide or ozone. A separation of the leach and filtrate using filtration followed. The leach was further processed by a precipitation of iron and other metals using various agents. After a further filtration, the electrolysis was performed in order to obtain pure zinc on the cathode at the electrical voltage of approximately 3.5 V. Leaching using a solution of sodium hydroxide or potassium hydroxide was also performed when the prior dissolving of a major part of zinc into the leach occurred, while iron and non-ferrous metals remained in the leaching residue. After the filtration of the leach, the electrolysis with a high zinc yield of a purity of more than 99% followed. This way seems to be an optimal one for building a semi-industrial line for galvanic sludge recycling. All the partial products, i.e., the leach, the leaching residue, the filtrate, the solid precipitate and the separated metal on the cathode were subjected to chemical analyses. The analyses results are presented in tables and graphs.
Final surface modification for better wear resistance of ceramic coating on cast AlSi10Mg alloy
(Elsevier, 2022) Gabor, Roman; Prymus, Tomáš; Cvrček, Ladislav; Nehasil, Václav; Hlinka, Josef; Buřil, Matěj; Tokarčíková, Michaela; Seidlerová, Jana
Using the design of experiment (DOE) method and the micro-arc oxidation (MAO) technique, ceramic layers on AlSi10Mg alloy were systematically prepared to design optimal process conditions for achieving the best tribological properties of the ceramic layers. The lowest concentrations of the applied 6 g/l NaOH and 12 g/l Na2SiO3 resulted in the preparation of uniform MAO layers with the lowest rated parameters Ra, Rz and thickness achieved under micro-arc discharge conditions at 500 V and 60 min. With the increasing thickness of the coatings, there was an increase of Si in the MAO coating. Full factorial DOE was used to optimize the tribological properties in a polyalphaolefin (PAO) environment at 80 degrees C. The most significant influence for the preparation of abrasion-resistant layers for the investigated factors was identified on the AlSi10Mg alloy by the NaOH content in the electrolyte. The friction coefficients of MAO coatings reached an average value of 0.15. Aero-lap polishing technology was applied for increased wear resistance requirements to eliminate the deficiencies of MAO coat-ings, leading to decrease wear track by almost double compared to polished silumin. Removal of the outer MAO layer by polishing led to a reduction in the high corrosion resistance of the MAO coating, demonstrating the influence of the outer layer not only on the tribological properties but also on the corrosion resistance of MAO coatings.
Hybrid coatings for orthopaedic implants formed by physical vapour deposition and microarc oxidation
(Elsevier, 2022) Gabor, Roman; Cvrček, Ladislav; Doubková, Martina; Nehasil, Václav; Hlinka, Josef; Unucka, Petr; Buřil, Matěj; Podepřelová, Adéla; Seidlerová, Jana; Bačáková, Lucie
This study is focused on the preparation of new hybrid layers intended for surface modification of Ti-6Al-4V alloys for potential orthopaedic and dental applications. Combination of the technology of physical vapour deposition (PVD) and subsequent micro-arc oxidation (MAO) was utilized for the deposition of Ti and ZrTi to form hybrid oxide layers. The oxide layers were prepared using an alkaline electrolyte with glycerol as an additive under micro-arc discharge conditions with different Si content on their surfaces. The hybrid ZrTi coatings with a Zr/Si structure achieved the best tribological properties described by a low friction coefficient of 0.3 and high abrasion resistance. There was also an increase in corrosion potential and polarization resistance of hybrid ZrTi coatings. Although the proliferation of human bone marrow mesenchymal stem cells was slower on these hydrophilic Ti and ZrTi coatings than both on uncoated Ti-6Al-4V and the reference tissue culture polystyrene dishes, both types of hybrid coating promoted greater osteogenic differentiation of these cells, indicated by approx. twice as high activity of alkaline phosphatase. The hybrid oxide layers newly developed in this study - especially the layers with Zr - are therefore promising for coating metallic bone implants.
The effect of long-term ageing at 475 degrees C on microstructure and properties of a precipitation hardening martensitic stainless steel
(MDPI, 2022) Vodárek, Vlastimil; Rožnovská, Gabriela; Kuboň, Zdeněk; Volodarskaja, Anastasia; Palupčíková, Renáta
The effect of long-term ageing (1000, 2000, and 3000 h) at 475 degrees C on mechanical properties, microstructure, and substructure of CUSTOM 465 (R) maraging stainless steel was studied. The additional precipitation of nanometric particles of eta-Ni3Ti phase in partly recovered lath martensite and decomposition of the BCC solid solution accompanied by the formation of nanometric Cr-rich alpha'particles were identified. The fraction of reverted austenite in the final microstructure gradually increased with time of ageing at 475 degrees C. Ageing resulted in a gradual slight decline (up to 10%) in yield strength, ultimate tensile strength, and hardness. On the other hand, for all ageing, dwells ductility and impact energy values remained almost unchanged. The reason for this phenomenon lies in the gradual increase in the fraction of reverted austenite during long-term ageing at 475 degrees C and at the same time in the sluggish kinetics of microstructural changes in lath martensite. No susceptibility to 475 degrees C embrittlement was proved.
Effect of artificial aging on the strength, hardness, and residual stress of SLM AlSi10Mg parts prepared from the recycled powder
(Elsevier, 2022) Měsíček, Jakub; Čegan, Tomáš; Ma, Quoc-Phu; Halama, Radim; Skotnicová, Kateřina; Hajnyš, Jiří; Juřica, Jan; Krpec, Pavel; Pagáč, Marek
This study investigated the effect of artificial aging on the hardness, strength, and residual stress of SLM (Selective Laser Melting) AlSi10Mg parts prepared from recycled powder used for 30 SLM printing cycles. First, an analysis was conducted for a comparison of recycled and virgin powders; it revealed that the powders have the same shape and phase and chemical composition. The only significant differences were the slightly increased average particle size and higher oxygen content in the recycled powder, especially on the powder surface. Typical molten pools were found in the microstructure, and a fine cellular type of structure was observed. The peripheral areas of the molten pools contained coarser cells with an average size of 0.6 mu m(2), and the middle part of the molten pools contained finer cells with an average size of 0.17 mu m(2). Fine Si precipitates with an average size of 25 nm were observed inside the cells. In terms of microstructure, no significant differences were observed when compared to the published data relating to SLM using virgin powders. This suggests that recycled powder after 30 printing cycles can be utilized for SLM component preparation to achieve cost-effectiveness. However, comparison of products with the use of virgin and recycled powders showed that the use of recycled powder affects the submicron characteristics (precipitate size increase), density and the resulting mechanical properties. Artificial aging of samples from the recycled powder at 170 ? caused an increase in hardness, Young's modulus and strength, while ductility remained essentially the same after aging. Peak values of hardness and strength were determined after 6 h of artificial aging. The increase in strength of the prepared samples can be explained by the precipitation of fine Si particles and their coarsening inside the cells. However, after longer aging times, the precipitates continued to coarsen, coalesced and displayed a plate-like shape, which led to the reduction in strength. The residual stress measured by the bridge curvature method (BCM) showed a significant decrease with increasing artificial aging time. The lowest residual stress was determined for an aging time of 100 h; however, the difference between residual stress for 6-7 h and 100 h was not significant. In order to obtain higher strengths and remove internal stresses after SLM during one heat treatment, the most suitable time for artificial aging at 170 ? seems to be 6 h.
Biomechanical assessment of cannulated nails for the treatment of proximal femur fractures
(MDPI, 2022) Frydrýšek, Karel; Halo, Tomáš; Čepica, Daniel; Machalla, Vojtěch; Šimečková, Kateřina; Skoupý, Ondřej; Madeja, Roman; Havlíček, Miroslav; Dostálová, Kamila; Trefil, Antonín; Pleva, Leopold; Murčinková, Zuzana; Krpec, Pavel; Hlinka, Josef
This article focuses on a type of surgical implant used in orthopaedics and traumatology-cannulated femoral nails. Femoral nails are used in medical treatment for purposes of osteosynthesis, i.e., when treating various types of complicated fractures, in this case fractures of the femur. The article investigates cases in which a nail has been implanted in the proximal part of the femur for a short time (with the fracture still not healed), compared with cases in which the bone has already healed. According to AO classification, examined fractures are described as AO 31B3 AO 32A3. The main focus is on strength-deformation analysis using the finite element method (FEM), which makes it possible to determine the behaviour of the femur-implant system. FEM analysis was used to compare 1.4441 steel nails made by two manufacturers, Medin (Czech Republic) and Tantum (Germany). Boundary conditions including external loading, prescribed supports and elastic foundation are defined. There were solved FEM analyses for five cases of healed femur and five cases of broken femur both including implants with prescribed collo-diaphyseal angles. The results of the analysis were used to assess stress-deformation states from the perspective of appropriateness for clinical treatment, biomechanical reliability and safety. All examined femoral nails are compared, safe and suitable for patient treatment.
Study of wettability and solderability of SiC ceramics with Ni by use of Sn-Sb-Ti solder by heating with electron beam in vacuum
(MDPI, 2022) Koleňák, Roman; Kostolný, Igor; Drápala, Jaromír; Urminský, Ján; Pluhár, Alexej; Babincová, Paulína; Dřímal, Daniel
The aim of this research was to study the wettability and solderability of SiC ceramics by the use of an active solder of the type Sn5Sb3Ti in a vacuum by electron beam heating. This solder exerts a narrow melting interval, and only one thermal effect, a peritectic reaction, was observed. The liquidus temperature of the solder is approximately 243 degrees C. The solder consists of a tin matrix where the Ti-6(Sb,Sn)(5) and TiSbSn phases are precipitated. The solder wettability on a SiC substrate decreases with decreasing soldering temperature. The best wetting angle of 33 degrees was obtained in a vacuum at the temperature of 950 degrees C. The bond between the SiC ceramics and the solder was formed due to the interaction of Ti and Ni with silicon contained in the SiC ceramics. The formation of new TiSi2 and Ti3Ni5Si6 phases, which form the reaction layer and thus ensure the bond formation, was observed. The bond with Ni is formed due to the solubility of Ni in the tin solder. Two phases, namely the Ni3Sn2 and Ni3Sn phases, were identified in the transition zone of the Ni/Sn5Sb3Ti joint. The highest shear strength, around 40 MPa, was attained at the soldering temperature of 850 degrees C.
Processing and microstructure of as-cast Ti-45Al-2W-xC alloys
(MDPI, 2022) Čegan, Tomáš; Kamyshnykova, Kateryna; Lapin, Juraj; Szurman, Ivo; Juřica, Jan; Klimantová, Vendula
The metallurgical preparation and microstructure of as-cast Ti-45Al-2W-xC (in at.%) alloys were investigated. Five alloys with carbon content ranging from 0.38 to 1.96 at.% were prepared by vacuum induction melting (VIM) in graphite crucibles, followed by centrifugal casting into graphite moulds. A master 15W-85Al (at.%) alloy with a relatively low melting point and TiC powder were used to facilitate fast dissolution of W during VIM and to achieve the designed content of C in the as-cast alloys, respectively. The increase in the content of C affects the solidification path of the studied alloys. Differential thermal analysis (DTA) and microstructural observations show that the alloys with carbon content up to 0.75 at.% solidify with beta primary phase and their dendritic as-cast microstructure consists of the alpha(2)(Ti3Al) + gamma(TiAl) lamellar regions, retained B2 phase enriched by W and single gamma phase formed in the interdendritic region. The increase in the content of C above 0.75 at.% leads to the formation of primary lathe-shaped Ti2AlC carbides, which act as effective heterogeneous nucleation sites of beta dendrites during the solidification and grain refinement of the alloys with 1.15 and 1.96 at.% C. The increase in the content of C leads to an increase in Vickers hardness and elastic modulus in the alloys containing 1.96 at.% C.

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