Publikační činnost Katedry metalurgických technologií / Publications of Department of Metallurgical Technologies (652)

Permanent URI for this collectionhttp://hdl.handle.net/10084/146153

Kolekce obsahuje bibliografické záznamy publikační činnosti akademických pracovníků Katedry metalurgických technologií (652) 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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Now showing 1 - 20 out of 43 results

Design and optimization of a castability test for copper alloys applied to plaster moulds
(Elsevier, 2024) Radkovský, Filip; Zlámal, František; Vasková, Iveta; Bašistová, Martina; Lichý, Petr; Kielar, Šimon; Socha, Ladislav
The paper deals with the design and execution of the test of the castability into preheated plaster moulds. Castability is an important parameter for the evaluation of foundry alloys. When the metal does not run, it usually causes an irreparable defect in the casting. Therefore, it is necessary to verify this technological property correctly for different types of moulds. The castability test for plaster moulds and bronze is not defined, therefore The Vertical Bar Test was adopted, subsequently modified, and applied to plaster moulds. The models are made of wax and the plaster moulds are made according to the manufacturer's prescription and heated to a predetermined temperature. Copper alloy specifically CuSn10 was selected as the alloy to be investigated. The aim of the experiment is to correctly set up and observe the parameters and the method of performing the castability test using gravity casting technology in plaster moulds. It is assumed, as the casting temperature increases, the run-in length of the metal alloy will increase. An important goal is to obtain relevant results, as many variables affect the progress of the test and so there is a risk of error. Due to the time-consuming nature of producing a real disposable model and mould, any failure to succeed would have an economic impact on the foundry, affecting the price of castings. The new method for evaluating castability in plaster moulds can be applied to other types of alloys when temperature changes occur.
High strain rate induced shear banding within additively manufactured AISI 316L
(Elsevier, 2024) Kunčická, Lenka; Kocich, Radim
The effects of post-processing via cold/hot rotary swaging, combined with high strain rate deformation, on formation of shear bands and deformation induced martensite within AISI 316L steel prepared by Selective Laser Melting are investigated. The as-built sample exhibited randomly oriented grains and residual porosity, which was reduced/eliminated by rotary swaging and subsequent high strain rate deformation. Hand in hand with significant changes in grain morphology after swaging (grain elongation and refinement, especially under cold conditions) and high strain rate processing (formation of shear bands and deformation induced martensite), the combined deformation imparted substantial hardening and resulted in microhardness increase by more than 20 %, primarily due to the occurring martensitic transformation. The structure changes were observed especially for the cold processed sample, due to aggravated plastic flow and hindered movement of generated partial dislocations.
Influence of imposed strain on weldability of Dievar alloy
(MDPI, 2024) Izák, Josef; Benč, Marek; Kunčická, Lenka; Opěla, Petr; Kocich, Radim
The presented work is focused on the influence of imposed strain on the weldability of Dievar alloy. Two mechanisms affecting the microstructure and thus imparting changes in the mechanical properties were applied-heat treatment (hardening and tempering), and rotary swaging. The processed workpieces were further subjected to welding with various welding currents. In order to characterize the effects of welding on the microstructure, especially in the heat-affected zone, and determine material stability under elevated temperatures, samples for uniaxial hot compression testing at temperatures from 600 to 900 degrees C, optical and scanning electron microscopy, and microhardness testing were taken. The testing revealed that, although the rotary swaged and heat-treated samples featured comparable microhardness, the strength of the swaged material was approximately twice as high as that of the heat-treated one-specifically 1350 MPa. Furthermore, it was found that the rotary swaged sample exhibited favorable welding behavior when compared to the heat-treated one, when the higher welding current was applied.
Coke substitution with anthracite in sintering production
(MDPI, 2024) Pustějovská, Pavlína; Sikora, Michal; Jursová, Simona; Pustějovská, Kristýna; Kardas, Edyta
This article summarises the possibility of replacing the coke breeze sintering fuel with an economically and ecologically more suitable fuel, anthracite. The main focus is on the possibility of replacing coke breeze with anthracite, during which, the replacement process is accelerated and the other properties are also affected. The analyses performed showed that the replacement of coke breeze with different amounts of anthracite does not have a negative effect if the initial permeability of the sintering bed is the same.
Corrosion behavior of selective laser melting-manufactured bio-applicable 316L stainless steel in ionized simulated body fluid
(AccScience Publishing, 2024) Kocich, Radim; Kunčická, Lenka; Benč, Marek; Weiser, Adam; Németh, Gergely
Additive manufacturing (AM) is gaining increasing popularity in various fields, including biomedical engineering. Although AM enables fabrication of tailored components with complex geometries, the manufactured parts typically feature several internal issues, such as unpredictable distribution of residual stress and printing defects. However, these issues can be reduced or eliminated by post -processing via thermomechanical treatment. The study investigated the effects of combinations of AM and post-processing by the intensive plastic deformation method of rotary swaging (variable swaging ratios) on microstructures, residual stress, and corrosion behaviors of AISI 316L stainless steel workpieces; the corrosion tests were performed in an ionized simulated body fluid. The results showed that the gradual swaging process favorably refined the grains and homogenized the grain size. The imposed swaging ratio also directly influenced the development of substructure and dislocations density. A high density of dislocations positively affected the corrosion resistance, whereas annihilation of dislocations and formation of subgrains had a negative effect on the corrosion behavior. The first few swaging passes homogenized the distribution of residual stress within the workpiece and acted toward imparting a predominantly compressive stress state, which also favorably influenced the corrosion behavior. Lastly, the presence of the {111}||swaging direction texture fiber (of a high intensity) increased the resistance to pitting corrosion. Overall, the most favorable corrosion behavior was acquired for the AM sample subjected to the swaging ratio of 0.8, exhibiting a strong fiber texture and a high density of dislocations.
Correlation between the changes in microstructure and chemical composition of the surface layer of nickel superalloy after laser shock processing
(Elsevier, 2024) Rozmus-Górnikowska, Magdalena; Kusiński, Jan; Cieniek, Łukasz; Morgiel, Jerzy; Lichý, Petr; Bašistová, Martina
The aim of this work was to investigate the correlation between the changes in microstructure and chemical composition of the surface layer of nickel superalloy after Laser Shock Processing. It has been shown that overlapping of subsequent laser shots causing the surface roughness, which values are much smaller in the direction of overlapping of subsequent shots than in the direction perpendicular to. After the LSP process we can distinct in the surface layer following zones: melted, recrystallized, highly deformed and partially deformed zone. Due to the thermomechanical deformation, there are significant changes in the microstructure and elements distribution in the subsurface areas. The distribution of chemical elements in the melted and recrystallized zones is more homogeneous than in deformed and partially deformed ones, which is due to the disappearing, distortion and refinement of the regular gamma/gamma ' cell structure.
Applications of tungsten pseudo-alloys in the energy sector
(MDPI, 2024) Macháčková, Adéla; Bárta, Otakar; Brožová, Silvie
New energy generation methods are currently being discussed with a view towards the transition from traditional primary sources to more environmentally friendly options, particularly renewables. Energy storage is also closely related to this transition. Battery storage currently dominates this area. However, flywheel energy storage system technology offers an alternative that transforms stored kinetic energy into mechanical and electrical energy using a motor generator. The flywheel energy storage system technology is thus flexible and can be applied in different industrial applications. The management of the technology of recycling tungsten multi-metallic composites (W-MMC) waste material from other products and the subsequent trial production of high-strength W-MMC material with a density of more than 17,500 kg/m3 from recycled powders allowed us to test the limits of the so-called "heavy" flywheels used in rotor production. The results achieved lead to the conclusion that the developed recycled materials of the W-MMC type with a density >= 17,500 kg/m3, with a yield strength of 1200-1700 MPa depending on the production method, can be used as a substitute for the structural steels used today without an enforced reduction in the maximum allowed rotor speed due to exceeding the maximum allowed stress.
Variability in the distinctive features of silica sands in Central Europe
(MDPI, 2024) Bašistová, Martina; Vontorová, Jiřina; Zlá, Simona; Kawuloková, Monika; Lichý, Petr; Dvorský, Tomáš
Quality quartz sand is globally utilized in construction due to its availability and economic factors, especially in the production of composite cements. Despite its positive properties, quartz sand also has several disadvantages. The dilation of quartz sand can be technologically significant for certain high-temperature applications. This dilation has a non-continuous character with sharp volume change caused by the phase transformation from beta to alpha SiO2 at temperatures around 573 degrees C. The extent of dilation depends on various factors such as compaction, grain size, the quantity of sand, as well as the shape and character of the grain and chemical purity, particularly the SiO2 content. In this study, six types of quartz sand from different locations in Central Europe were examined, and the influence of chemical composition and grain shape was correlated with the final dilation of these samples. Evaluation methods included X-ray fluorescence spectroscopy (XRFS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), differential thermal analysis (DTA), and linear thermal expansion analysis. It was found that angular grains, despite their chemical purity, may exhibit minimal dilation. Conversely, the least suitable combination in terms of dilation appears to be a high SiO2 content and high roundness of grains with a smooth surface.
Determining hot deformation behavior and rheology laws of selected austenitic stainless steels
(MDPI, 2023) Němec, Josef; Kunčická, Lenka; Opěla, Petr; Dvořák, Karel
Due to their versatile properties, austenitic stainless steels have a wide application potential, including in specific fields, such as the nuclear power industry. ChN35VT steel is a chromium–nickel– tungsten type of steel stabilized by titanium, and it is suitable for parts subjected to considerable mechanical stress at elevated temperatures. However, the available data on its deformation behavior at elevated/high temperatures is scarce. The core of the presented research was thus the experimental characterization of the deformation behavior of the ChN35VT steel under hot conditions via the determination of flow stress curves, and their correlation with microstructure development. The obtained data was further compared with data acquired for 08Ch18N10T steel, which is also known for its applicability in the nuclear power industry. The experimental results were subsequently used to determine the Hensel-Spittel rheology laws for both the steels. The ChN35VT steel exhibited notably higher flow stress values in comparison with the 08Ch18N10T steel. This difference was more significant the lower the temperature and the higher the strain rate. Considering the peak stress values, the lowest difference was ~8 MPa (1250 ◦C and 0.01 s−1 ), and the highest was ~150 MPa (850 ◦C and 10 s−1 ). These findings also corresponded to the microstructure developments—the higher the deformation temperature, the more negligible the observed differences as regards the grain size and morphology.
Technology of production of mold filling material for specific purposes in the field of metallic foam casting
(Polska Akademia Nauk, Instytut Metalurgii i Inżynierii Materiałowej, 2023) Kroupová, Ivana; Bašistová, Martina; Lichý, Petr; Merta, Václav; Radkovský, Filip; Jezierski, Jan
This paper describes the technology for the production of precursors (space holder material) used to form the complex internal structure of cast metal foam. The precursor material must exhibit sufficient refractoriness, resist contact with liquid metal and at the same time should exhibit good collapsibility after casting. With regard to the greening of foundry production, the focus of this paper was on materials that could exhibit the above properties and at the same time do not have a negative impact on the environment. In this paper, the technology for the production of spherical precursors from a self-hardening mixture with a geopolymer-based binder system is described and verified. The motivation for the choice of material and all the sub-steps of the process – molding into the core box, tumbling, including the necessary accompanying tests of the mechanical properties of the core mixture being verified – are described.
Physical experiments and numerical simulations of the influence of turbulence inhibitors and the position of ladle shroud on the steel flow in an asymmetric five-strand tundish
(MDPI, 2023) Walek, Josef; Tkadlečková, Markéta; Velička, Marek; Machů, Mario; Cupek, Jiří; Huczala, Tomáš; Cibulka, Jiří; Růžička, Jan; Michalek, Karel
The submitted article deals with the use of physical and numerical modelling to study the process of the steel flow in an asymmetric five-strand tundish that continuously casts steel. For the purposes of physical modelling, a 1:4-scale plexiglass model was used as the operating tundish, and for numerical modelling, the geometry of the operating tundish was created on a 1:1 scale. A model liquid (water) was used in the physical modelling of the melt flow process, while liquid steel was used as the standard flowing medium in the numerical modelling. We assessed the relevant operating parameters influencing the characteristics of the flow of the bath in the tundish—the shape of the turbulence inhibitor, the position of the ladle shroud in relation to the turbulence inhibitor and the distance between the ladle shroud orifice and the bottom of the turbulence inhibitor. The preliminary results show that optimal steel flow characteristic results are achieved by using the TI3-C configuration. The results from both modelling methods achieved the same characteristics, therefore verifying the results of each other and demonstrating that when taken together, the results of physical and numerical modelling can be considered sufficiently informative.
Development of microstructure and properties within oxide dispersion strengthened steel directly consolidated by hot rotary swaging
(Elsevier, 2023) Kocich, Radim; Kunčická, Lenka; Benč, Marek
Steels strengthened with fine oxides maintain favourable mechanical properties at high temperatures. This unique study evaluates the effects of direct consolidation of mechanically alloyed powders of ferritic steel and Y2O3 nanooxides by hot rotary swaging (multiple swaging ratios) on microstrutcures and mechancial properties of final rods. Direct consolidation of the steel powder by the proposed method was successful at the swaging ratio 1.0. However, the quality of consolidation improved with increasing the swaging ratio to 1.4, and finally to 1.8 (no visible pores). The microstructure of the rod processed with swaging ratio 1.8 exhibited homogeneous dispersion of oxide particles and featured ultra-fine (UF) grains, its average Vickers microhardness exceeded 700 HV1.
Effect of stacking sequence on mechanical properties and microstructural features within Al/Cu laminates
(MDPI, 2023) Kunčická, Lenka; Kocich, Radim
The study presents a method to prepare Al/Cu laminated conductors featuring two different stacking sequences using rotary swaging, a method of intensive plastic deformation. The primary focus of the work was to perform detailed characterization of the effects of room temperature swaging on the development of microstructures, including the Al/Cu interfaces, and internal misorientations pointed to the presence of residual stress within the laminates. The results revealed that both the Al and Cu components of the final laminates with 5 mm in diameter featured fine, more or less equiaxed, grains with no dominating preferential texture orientations (the maximum observed texture intensity was 2.3 × random for the Cu components of both the laminates). This fact points to the development of dynamic restoration processes during swaging. The analyses of misorientations within the grains showed that residual stress was locally present primarily in the Cu components. The Al components did not feature a substantial presence of misorientations, which confirms the dynamic recrystallization. Tensile testing revealed that the laminates with both the designed stacking sequences exhibited comparable UTS (ultimate tensile strength) of almost 280 MPa. However, notable differences were observed with regard to the plasticity (~3.5% compared to less than 1%). The laminate consisting of Al sheath and Cu wires exhibited very low plasticity as a result of significant work hardening of Al; this hypothesis was also confirmed with microhardness measurements. Observations of the interfaces confirmed satisfactory bonding of both the metallic components.
Evaluation of mixing efficiency and how it affects the properties of the new green sand mixtures
(Polska akademia nauk. Oddział PAN w Katowicach, 2023) Kielar, Šimon; Bašistová, Martina; Lichý, Petr
The current trend in the preparation of green sand mixtures emphasizes the acceleration of the mixing process while maintaining the quality of the mixture. This requirement results in the necessity of determining the optimal conditions for mixing the mixture with a given mixer. This work aims to determine the optimal mixing conditions for the newly introduced eddy mixer LM-3e from the company Multiserw-Morek in the sand laboratory at the Department of Metallurgical Technologies, Faculty of Materials and Technology, VSB Technical University of Ostrava. The main monitored properties of mixtures will be green compressive strength and moisture of the mixture. The measured properties of the mixture mixed on the eddy mixer will be compared with the properties of the mixture mixed on the existing LM-2e wheel mixer. The result of the experiment confirmed that the eddy mixer is suitable for the preparation of a mixture of the same quality as the wheel mixer but with a significantly reduced mixing time.
In situ synchrotron X-ray diffraction analysis of two-way shape memory effect in Nitinol
(Elsevier, 2023) Wang, Zifan; Zhang, Yunlan; Liogas, Konstantinos; Chen, Jingwei; Vaughan, Gavin B. M.; Kocich, Radim; Kunčická, Lenka; Uzun, Fatih; You, Zhong; Korsunsky, Alexander M.
Despite the fact that the Two-Way Shape Memory Effect (TWSME) has been demonstrated in most Shape Memory Alloys, the effective application of this unique functional behaviour is hindered by the lack of a proper training methodology and understanding of its mechanisms. In this study, a novel training routine has been established together with a home-designed device, enabling TWSME of customised spline curvature to be produced. An in situ high energy synchrotron X-ray diffraction experiment has been performed on Nitinol, followed by comprehensive analysis to reveal the micromechanics of TWSME. Multiple mainstream hypotheses have been examined. The important findings are: (1) The training process has negligible influence on the texture of parent phase; (2) The preferred variant of the B19’ phase exhibits tension/compression asymmetry in TWSME; (3) (100) compound twin is the preferred deformation mode for compression TWSME; (4) The mesoscale residual strain field is the dominant factor that induces TWSME; (5) Lattice defects (dislocations) are spatially rearranged after training; (6) Compression TWSME training retards the B2 to B19’ transformation, whilst tension has the opposite effect. The implications of these findings are further discussed.
Decomposition of γ-Fe in 0.4C–1.8Si-2.8Mn-0.5Al steel during a continuous cooling process: A comparative study using in-situ HT-LSCM, DSC and dilatometry
(Elsevier, 2023) Liu, Man; Bernhard, Michael; Kawuloková, Monika; Walek, Josef; Kern, Maximilian; Zlá, Simona; Presoly, Peter; Smetana, Bedřich; Tkadlečková, Markéta; Xu, Guang; Kang, Youn-Bae; Bernhard, Christian
Continuous cooling transformation (CCT) diagrams represent roadmaps for producing all heat-treatable steels. CCT curves provide valuable information on the solid-state phase transformation sequence, depending on the defined cooling strategies, the alloying concept of the steel and previous processing steps. The experimental characterization of CCT diagrams is usually done on a laboratory scale applying thermal analysis of dilatometry. In current research studies, however, also other in-situ methods such as high-temperature laser scanning confocal microscopy (HT-LSCM) or differential scanning calorimetry (DSC) are frequently used to investigate phase transformations during thermal cycling. In the present study, HT-LSCM observations and DSC analysis are critically compared with dilatometry results by investigating the CCT diagram of a 0.4%C-1.8%Si-2.8%Mn-0.5%Al (in mass pct.) advanced steel grade. Furthermore, classical examinations by optical microscopy and hardness measurements were performed to support the analysis. In general, very good consistencies between all experimental techniques were identified in determining the transformation start temperature for pearlite, bainite and martensite. The optical microscopy confirmed the observed phase transformations and the results correlated with the measured hardness response. Based on the results, coupling of HT-LSCM and DSC is considered as a valuable novel approach to plot CCT diagrams in future research.
Influence of structure development on performance of copper composites processed via intensive plastic deformation
(MDPI, 2023) Kocich, Radim; Opěla, Petr; Marek, Martin
Designing a composite, possibly strengthened by a dispersion of (fine) oxides, is a favorable way to improve the mechanical characteristics of Cu while maintaining its advantageous electric conductivity. The aim of this study was to perform mechanical alloying of a Cu powder with a powder of Al2O3 oxide, seal the powder mixture into evacuated Cu tubular containers, i.e., cans, and apply gradual direct consolidation via rotary swaging at elevated temperatures, as well as at room temperature (final passes) to find the most convenient way to produce the designed Al2O3 particle-strengthened Cu composite. The composites swaged with the total swaging degree of 1.83 to consolidated rods with a diameter of 10 mm were subjected to measurements of electroconductivity, investigations of mechanical behavior via compression testing, and detailed microstructure observa tions. The results revealed that the applied swaging degree was sufficient to fully consolidate the canned powders, even at moderate and ambient temperatures. In other words, the final structures, featuring ultra-fine grains, did not exhibit voids or remnants of unconsolidated powder particles. The swaged composites featured favorable plasticity regardless of the selected processing route. The flow stress curves exhibited the establishment of steady states with increasing strain, regardless of the applied strain rate. The electroconductivity of the composite swaged at elevated temperatures, featuring homogeneous distribution of strengthening oxide particles and the average grain size of 1.8 µm2, reaching 80% IACS (International Annealed Copper Standard).
The influence of silica sand granulometry and sorting level on thermal expansion
(Polska akademia nauk. Oddział PAN w Katowicach, 2023) Bašistová, Martina; Lichý, Petr
The quality of the castings depends, among other influences, on the quality of the moulding mixture used. The silica sands used are characterized by high thermal expansion compared to other sands. The tendency to dilatation of the moulding mixture can be influenced by the choice of the granulometric composition of the basic sand and the grain size. The aim of this work is to present the influence of grain distribution of foundry silica sand BG 21 from Biala Góra (Poland) and the degree of sorting (unsorted, monofraction, polyfraction) on the degree of thermal dilatation of the sand and thus on the resulting quality of the casting and susceptibility to foundry defects. For the purpose of measuring thermal dilatation, clay wash analysis was performed, sieve analysis of the sand was carried out, and individual sand fractions were carefully sorted. The measurements confirmed a higher thermal expansion in the case of monofractional sand grading, up to 51.8 %. Therefore, a higher risk of foundry stress-strain defects, such as veining, can be assumed.
Computational fluid dynamics (CFD) analysis of medium flow and removal of inclusions in a two-strand tundish
(Hrvatsko Metalurško Društvo, 2023) Cupek, Jiří; Tkadlečková, Markéta; Merder, Tomasz; Walek, Josef; Saternus, Mariola; Pieprzyca, Jacek
The article presents the results of the CFD simulation of the method of medium flow and mixing, as well as the movement and removal of solid particles in the model of two-strand tundish as a result of installed internal arrange ment. Two variants including turbulence inhibitor and impact pad with a ball cutting area were modeled for the tests. CFD simulations are a continuation of previous tests with the use of the physical water model of the continu ous steel casting (CSC) device
High cycle fatigue behaviour of 316L stainless steel produced via Selective Laser Melting method and post processed by hot rotary swaging
(MDPI, 2023) Opěla, Petr; Benč, Marek; Kolomý, Štěpán; Jakůbek, Zdeněk; Beranová, Denisa
This paper deals with a study of additively manufactured (by the Selective Laser Melting, SLM, method) and conventionally produced AISI 316L stainless steel and their comparison. With the intention to enhance the performance of the workpieces, each material was post-processed via hot rotary swaging under a temperature of 900 ◦C. The samples of each particular material were analysed regarding porosity, microhardness, high cycle fatigue, and microstructure. The obtained data has shown a significant reduction in the residual porosity and the microhardness increase to 310 HV in the sample after the hot rotary swaging. Based on the acquired data, the sample produced via SLM and post-processed by hot rotary swaging featured higher fatigue resistance compared to conventionally produced samples where the stress was set to 540 MPa. The structure of the printed samples changed from the characteristic melting pools to a structure with a lower average grain size accompanied by a decrease of a high fraction of high-angle grain boundaries and higher geometrically necessary dislocation density. Specifically, the grain size decreased from the average diameters of more than 20 µm to 3.9 µm and 4.1 µm for the SLM and conventionally prepared samples, respectively. In addition, the presented research has brought in the material constants of the Hensel-Spittel formula adapted to predict the hot flow stress evolution of the studied steel with respect to its 3D printed state.

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