Seznam abstraktů 2024: SEKCE E - NEŽELEZNÉ KOVY A SLITINY

Aluminium alloys are popular among automotive heat exchangers designers due to their high thermal conductivity, good corrosion resistance and excellent strength-to-weight ratio. Aluminium alloy EN AW-3003 and its modifications are commonly used in this field. This work investigates the importance that the grain refinement has in changing the microstructure of the enhanced EN AW-3003 alloy with content of Zr and Zn when producing the alloy by Twin-Roll Casting. The work compares the grain refining efficiency of the two most commonly used master alloys, Al-5 wt. % Ti-1 wt. % B (TiBAl) and Al-3 wt. % Ti-0,15 wt. % C (TiCAl), using cooling curves analysis, metallographic samples analysis and tensile tests. The results show higher nucleation effectiveness of Al-5 wt. % Ti-1 wt. % B master alloy when compared to its Al-3 wt. % Ti-0,15 wt. % C counterpart. In addition, the use of Al-5 wt. % Ti-1 wt. % B master alloy leads to final product with slightly higher mechanical properties and more uniform microstructure. However, the grain refinement of enhanced EN AW-3003 aluminium alloy is a more complex problem involving other aspects (technological, economic, etc.). This is an important point for future study.

Wear resistance is vital for parts that require sliding contact. Different surface treatments have existed in industry and anodizing is the one of techniques for forming a protective oxide coating to improve hardness and abrasion resistance. Due to its good mechanical properties after precipitation hardening, the 6061-T6 aluminum alloy is extensively chosen in the aircraft industry. Its major alloying elements are magnesium and silicon. Thus, anodic coatings of good quality can be easily applied to this alloy. In this study, the effect of anodizing time on the tribological properties of 6061-T6 aluminum samples was evaluated. The aluminum samples were anodized in two different electrolytes sulfuric and chromic acid to specify the effects of anodizing solution type on the tribological properties of the anodic coatings. The anodized specimens were tested using a ball-on-disc tribometer and tribological properties such as friction coefficient and specific wear rate were characterized. At the end of the work, optimum anodizing time was identified for best wear properties.

Hot tearing is one of the most critical casting defects that affect the castability of an alloy and the final integrity of a component. Despite being extensively studied over the past 70 years, multiple theories persist regarding the mechanism that control the crack development and the key influencing phenomena. Most of the theories concur that the susceptibility is influenced by factors such as the chemical composition of the alloy, the cooling rate, and the microstructure of the alloy. This work aims to investigate the hot tearing susceptibility of wrought 6005 al alloys. Using the Kou criterion based on thermodynamic calculations, the influence of different levels of alloying elements and impurities, such as Mg, Si, Fe, and Mn on the alloy hot tearing susceptibility has been investigated.
Thermodynamic simulation results have shown that variations in th chemical composition of the alloy lead to discrete changes in the hot tearing susceptibility index. Specifically, lower tendency to hot cracking were observed when the concentration of the elements simultaneously reached the minimum level. Furthermore, the obtained results emphasized the critical role of selecting the solid fraction range, identified as the most vulnerable region for hot cracking formation. This selection proves key role in obtaining results that are reflected in industrial practices. These findings offer insight into the castability of wrought alloys and present a method for optimizing industrial process design.

Cryogenic cooling-controlled FSP (cryo-FSP) is emerged as one of the effective methods for developing ultrafine grained structure of aluminium alloy and its nanocomposite due to a higher cooling rate, resulting in improved mechanical strength. In this study, the microstructural evolution and mechanical behavior of AA5083-2%SiC nanocomposite produced by stir casting followed by cryo-FSP was investigated. The specimens were processed under optimized parameters (1400 rpm and 40 mm/min traverse speed) using a specially designed cryo-FSP setup, where a mixture of liquid nitrogen and methanol at ˗30ºC was circulated to cool the Cu-made backing plate during FSP. This Cryo-FSP process effectively disrupts the casting defects (such as voids, porosity, and dendritic structure) and exhibited excellent mechanical properties due to the evolution of a fine equiaxed grained microstructure (~2µm) as compared to the room temperature air cooled FSPed sample (~4 µm). The microstructural evolution and mechanical properties enhancement are attributed to grain boundary and dispersion strengthening. SEM-EBSD and TEM confirmed the fine-grain recrystallization and n-SiC particles redistribution within the Al matrix. Coarsening of secondary intermetallic particles was also restrained due to extraction of deformation heat effectively in the cryo-FSP process. Dominant mechanisms for microstructural evolution by recrystallization phenomena included CDRX and PSN, alongside DRV.

In this work, six AlFeCoNiCux (x=0.6-3.0) high entropy alloys were prepared by arc melting of high purity Al, Fe, Co, Ni and Cu lumps in argon. The as-cast alloys were composed of solid solutions with body-centered (BCC) and face-centered cubic (FCC) structure. The proportion of FCC was increasing with increasing Cu atomic fraction in the alloy. The oxidation resistance was studied by thermogravimetry. The isothermal annealing of AlFeCoNiCux alloys was carried out in flowing synthetic air at 1000 °C. The specific mass gain of the alloys was found to follow a parabolic rate law. A preferential formation of passive Al2O3 layer has been found. The parabolic rate constants were increasing with increasing Cu proportion in the alloys. A scale spallation has been observed on the alloys with higher Cu concentration due to thermal coefficient mismatch between substrate and oxide. The spallation facilitated oxygen diffusion through the Al2O3 layer and led to the formation of CuAl2O4 and CuO. The mechanism of high temperature corrosion is discussed and compared with previously studied high entropy alloys.
Acknowledgements: This work was funded by the Slovak Research and Development Agency (project no. APVV-20-0124), and the Scientific Grant Agency of the Ministry of Education, Science, Research and Sports of the Slovak Republic (project no. 1/0692/22).

AlCoCrFeNi2.1 alloy belongs to a group of materials called eutectic high-entropy alloys (EHEAs). These have gained attention due to the fact that there is no so-called "strength ductility trade-off". At the same time, the material properties are stable over a wide temperature range due to the high entropy state of the eutectic structure. The generally good castability of eutectic alloys, which prevents segregation of the major chemical elements and precipitation of new phases, also extends the possibilities for future applications. Based on the above, AlCoCrFeNi2.1 alloy could be applied in critical structural locations subjected to severe conditions in terms of elevated temperatures and mechanical stresses. Alloy could replace, for example, austenitic steels with high ductility but lower tensile strength values. In order to make full use of a given material, its behaviour must be verified in bonding technologies with commercially used materials. Therefore, the following research deals with heterogeneous weld joints of AlCoCrFeNi2.1 with austenitic steel EN 1.4571 formed by electron beam welding. The evaluation of the weld consisted of observation of the resulting microstructure, determination of the chemical concentration of the elements in the fusion zone, phase analysis followed by mechanical properties testing in the form of Vickers hardness test and tensile test.

The quality of the High Pressure Die Casting (HPDC) product strongly depends on the casting machine work. Today, numerical and experimental research is used to obtain casting parameters that ensure high and repeatable quality of the castings. In this work, authors investigate the impact of second phase piston velocity and intensification pressure on the porosity and microstructure. These results are most important for the tensile strength. The mass produced cover casting, made of EN AC-46000 aluminium alloy was analysed, which was possible to analyse experimentally and having different wall thicknesses in the whole volume, which range between 3 to 8 mm. Numerical simulation was performed with the use of MAGMASOFT 6.0 for selected machine settings. The simulation results were generated using the user results of the MAGMASOFT and external software. To validate numerical results experimental tests were performed. Real castings were first examined with X-ray, then those were cut in characteristic regions, and metallography specimens were prepared. The samples were then ground, and polish and microstructural analysis was performed that reviled the casting microstructure. Existing metallurgical phases were identified, and the SEM analysis was performed to confirm their type and composition. The conclusions given on the experimental and numerical results show that selected HPDC work parameters have an impact on the presence of porosity and microstructural component size and morphology.

Acknowledgements:
This research was supported by Polish Ministry of Science and Higher Education within AGH University of Krakow project no. 16.16.170.7998

Superalloy 625 has shown unique combination of good strength, ductility, and corrosion resistance even at elevated temperatures. Currently in India, an indigenous equivalent of Inconel 625, known as superni 625, is developed for high-temperature applications. This study focuses on understanding the influence of deformation and heat treatment on microstructural transformation and mechanical properties of cast alloy superni 625. For this purpose, homogenized cast alloy (both with and without prior deformation of 10% cold rolling) was subjected to ageing treatment at 700oC for different time intervals up to 1000h. Further, selected aged sampled samples were tested under uniaxial tensile load. Subsequently, SEM and TEM analyses were performed on aged samples to comprehend phase transformation micromechanisms such as (i) nucleation and growth kinetics of γʹʹ phase and (ii) transformation of primary carbides and (iii) evolution of grain boundary phase(s). Two completely different pathways were found for transformation of MC-based primary carbides to M23C6 secondary carbides: (I) MC+ γ→ M23C6 + δ & (II) MC+ γ→M23C6 + γʺ. Cold working before ageing promoted the first transformation reaction, hence formation of δ phase was increased drastically with pre-deformation. Owing to γʺ phase formation, the hardness and yield strength values were improved with ageing while ductility was lowered due to the precipitation of continuous carbide (M23C6) chain at grain boundary (gb), which facilitates easy crack propagation along gb. Interestingly, pre-deformation reduced deterioration of ductility due to the formation of more δ plates at gb, which hinders crack propagation during plastic deformation.

Metal-matrix composites (MMCs) consist usually of a soft matrix and hard particulates of various shapes. This combination is advantageous for numerous practical applications. From the viewpoint of understanding some detailed mechanisms, it is also interesting to study MMCs containing the soft matrix as well as the soft particulates. In this contribution, we refer to the plastic deformation of Cu-Ag MMCs produced by spark plasma sintering the Cu@Ag core-shell powders. Plastic deformation of such MMCs possesses a similar true stress-true strain dependence. This dependence can be phenomenologically described by the logarithmic dependence of the modified Ramsberg-Osgood law but surprisingly, also by quadratic functions. The parameters of these dependences are specified, quantified, and discussed concerning those of pure Ag and Cu as well as the values of a cast Cu-Ag alloy of comparable composition. Besides, the plastic deformation results in the prolongation of the particulates relative to the straining of the MMC, i.e., in the direction of tensile deformation and perpendicularly to the direction of compression. The aspect ratio of the particulates is related to the value of the strain, and it is shown that these values fit with a proposed model of sphere deformation.

This work was financially supported by the Czech Science Foundation under the grant No. 23-05139S. One of the authors (AS) acknowledges the grant of the Czech Academy of Sciences under No. L100102403.

This paper concerns the characteristics of the material considered as one of the potentially applicable ones under the research topic "Sustainable lead-free fittings for drinking water and gas installations - machinability and connection possibilities", which is an extension of the research results conducted as part of the project "Development and implementation of innovative fittings made of lead-free copper alloys for drinking, sanitary and technical water installations with reduced flow resistance for connections in installations based on PE pipes. One of the main assumptions of the project were eliminating the recrystallization annealing process because of the use of controlled cooling after forging. The test material was lead-free brass CuZn21Si3P.
The subject of the research is the thermoplastic forming process, which allows determining the relationship between the influence of the deformation amount, the temperature at the beginning and end of forging, and the cooling rate on the formation of an acicular structure.
The tests were carried out on a mechanical press after heating the samples to temperatures of 700°C, 770°C and 820°C. Strain values of 50% and 70% were used. After the process, the samples were cooled using a laboratory tunnel or in air.
Then, the quality of the forging was classified based on surface observations. This work discusses the deformation conditions that cause the formation of a relief on the surface of the tested samples, which indicates the overheating of the material and the presence of an acicular structure in it.

Work financed by the Ministry of Science and Higher Education as part of the 6th edition of the "Implementation Doctorate" program.
Work co-financed under the Smart Growth Operational Program 2014-2020.

This paper is prepared as a part of research and development activities carried out within the framework of the project of the Technology Agency of the Czech Republic reg. no. FW06010136. The aim is to design technological procedures for the production of biocompatible alloys, to verify these procedures for the content of undesirable gases and inclusions. Piece semi-finished products in the state of: Ti in the G1 grade from a tubular sputter target, Nb in the form of sheared from a sputter target, Ta in the form of evaporative springs, Sn is in the form of reworked blanks. The processing procedure was designed on modern metallurgical technology using plasma melting in a cold crucible. This reprocessed medical grade TiNbTaSn alloy was subsequently reworked into a semi-finished product by suitable ultrasonic atomization on a titanium core platform. The powder thus produced in the 10 to 100 μm fraction was submitted to further downstream experiments. The possibilities of 3D print of the prepared powder were tested.

Additive manufacturing of titanium and its alloys relies heavily on powder bed fusion techniques. However, these methods consume a significant amount of energy, and optimizing processing parameters can be time and resource consuming. Vat photopolymerization additive manufacturing offers design freedom like powder bed fusion techniques. It relies on selectively polymerizing a photosensitive resin by projecting light in the desired cross-section. Although commonly used for polymers and, to a lesser extent ceramics, its application to produce metallic objects has been limited because metals scatter light hindering resin polymerization. This study utilizes vat photopolymerization to create polymeric porous templates for titanium scaffold fabrication. The polymeric template is impregnated with a titanium powder slurry, followed by thermal removal of the template and sintering to consolidate the titanium structure. By employing this method, titanium scaffolds accurately replicate the structure of the polymeric template, demonstrating the feasibility of using vat photopolymerization for intricate titanium structure manufacturing. Nevertheless, the dimensions of the titanium scaffolds after sintering decreased by 50%, and X-ray diffraction patterns revealed traces of titanium carbides. In conclusion, optimizing the solid fraction of titanium in the slurry and refining the debinding process are necessary to reduce shrinkage and prevent chemical contamination during sintering. This work was supported by the Czech Science Foundation (GACR 23-07879S).

Ti nanoparticles were deposited on a glass substrate by a gas aggregation source and coated with a Ni layer under different deposition conditions. The resulting composite consists of partially core-shell Ti-Ni nanoparticles embedded in the Ni matrix. The thermal stability of the composite was studied during in-situ heating in the transmission electron microscope. Corresponding changes in the morphology of nanoparticles and the phase composition of the material were analyzed by energy dispersive X-ray analysis, selected area electron diffraction, and scanning (transmission) electron microscopy. The influence of the heating rate during the quasi-isochronal heating regime was tested.

Motivated by a decades-long controversy related to the crystal structure of Pb-supersaturated solid solutions of Pb in Sn, we have performed a quantum-mechanical study of these materials. In particular, we focused on three different allotropes of Pb-supersaturated Sn-rich Pb-Sn alloys with the α-Sn, β-Sn and a simple hexagonal γ-Sn structure. Structure-property relations were analyzed in the case of the lattice parameters, thermodynamic stability, elastic properties and mechanical stability as well as electronic-structure density of states. Compositional trends in structural, thermodynamic and electronic-structure properties were found nearly linear. Importantly, we suggest that the experimental difficulties in synthesizing the β-phase and γ-phase solid solutions are due to the high formation energy of these phases. For details see Friák et al., Metallurgical and Materials Transactions A (2024) accepted for publication, DOI:10.1007/s11661-024-07362-3. A financial support received under the Project No. 22-05801S from the Czech Science Foundation is gratefully acknowledged. Computational resources were provided by the e-INFRA CZ project (ID:90254), supported by the Ministry of Education, Youth and Sports of the Czech Republic. These resources were utilized through IT4Innovations National Supercomputing Center, MetaCentrum as well as CERIT Scientific Cloud.

Sn-based alloys have been investigated in order to replace the traditional Sn-Pb solder alloy. One of the potential candidates is the SAC305 alloy with Ni addition as it has the potential to refine the microstructure, lower the undercooling and improve the tensile strength solders and solder joints. The aim of this work is to analyze the phase composition, microstructure, and thermal behavior of Sn-3.0Ag-0.5Cu solders with (0.1, 0.4, 1, 4) mass% Ni addition using experimental techniques (scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, differential scanning calorimetry) and computational thermodynamics (Thermo-Calc). The results show that the microstructure of all samples consisted of β-Sn dendrites in eutectic matrix (β-Sn + Ag3Sn) and elongated particles of Cu6Sn5 intermetallic phase. Ni is dissolved in Cu6Sn5 phase, with increasing amount of Ni the Ni3Sn4 phase starts to form, at the expense of Cu6Sn5. With increasing Ni addition, the microstructure becomes coarser, mainly Cu6Sn5 and Ni3Sn4 phases with cracks observed mainly in the later phase. The low values of undercooling (3.6  14.4) °C of samples were determined, compared to the reported value for SAC305 solder. It was observed that the higher amount of Ni led to a higher undercooling. The results show a very good agreement between experimental results - phase composition, eutectic temperature, enthalpy of phase transformation (eutectic transformation + melting of β-Sn dendrites) and results achieved using thermodynamic computations in Thermo-Calc software. Furthermore, some predictions related to the occurrence of Ni3Sn4 phase and stabilization of the hexagonal high-temperature Cu6Sn5 phase are discussed.

The influence of Zn presence on degradation mechanism of Sn-based alloys was studied on model materials and naturally aged historical material. Special attention was payed to low temperature phase transformation of Sn also known as tin pest. The Zn addition to Sn-based alloys may be used in soldering materials to improve mechanical properties of the join. By means of optical and scanning electron microscopy and XRD, we have proven that it also accelerates the phase transformation. Even a low content of Pb (0.1 wt. %) suppress the phase transformation of Sn. The effect of addition of both Pb and Zn was also described.

During ferromanganese production, the manganese ores transit in different zones before reaching the coke bed zone called prereduction and reduction zone. The transition higher to lower oxides manganese oxides occurs reaching MnO. The reduction of MnO liquid by carbon producing Mn liquid was considered to be at equilibrium while empirical data and Katnelson were used to determine activity of Mn in the alloys considered saturated with carbon. The MnO activities calculated based on the manganese recovery using FactSage and the calculated MnO activity using HSC (Rea 9) were stacked up against the calculated values using FactSage. It was found that the calculated values using using HSC (Rea 9) and the FactSage were not close. The temperatures considered were 1400°C , 1450°C and 1475°C

The so-called tin pest is a phase transformation of white tin (alfa(Sn)) into grey tin (beta(Sn)), where the disintegration of tin materials occurs due to different thermodynamic stability of the phases with a transition at 13.2 °C. In trying to understand it, one can trace sources both on modern materials, where soldering material for electronic parts or solar cells installed at high altitudes i.e., at low temperatures is in the crosshairs, and on historical materials, especially organ pipes placed in unheated churches. Both types of sources always describe the issue only partially and even contradict each other on some points.
The pink salt (NH4)2SnCl6 was synthesized and once used as an accelerator in the inoculation of beta(Sn) with alfa(Sn) particles, thus accelerating the tin pest process to facilitate research. As a panichiite mineral, (NH4)2SnCl6 was discovered in nature in 2009 in the volcanic dust of some volcanoes. This knowledge carries the risk of contact with monumental and industrial objects through windblown dusting, not only near volcanoes, but as volcanic fallout has also been detected in the Czech Republic. Therefore, we investigated the yet unclear effect of pink salt on tin that is not inoculated by alpha particles, under different conditions simulating both weathering and material maintenance.

The paper deals with the evaluation of the surface texture of parts produced by material extrusion based 3D printing technology (FDM/FFF). Samples from PETG material were used for evaluation. The surface texture was evaluated after printing and after the ironing process of the last printed layer. Ironing was carried out using ironing at an angle of 45° with different line spacing parameters. The parameters selected to evaluate the surface texture were the height parameter Ra (arithmetic mean height), Rz (maximum height), Rpt (maximum peak height), Rvt (maximum pit depth), the hybrid parameter Rdl (developed length) and the parameter based on profile elements Rpc (peak count parameter). The selected surface texture parameters lead to the characterization of surface texture changes that occur after the ironing process (reduction of protrusion height, filling of depressions, reduction of surface roughness) and that affect its functional properties (reflectivity, adhesion). This paper presents one possible approach to evaluate stratified surfaces produced by 3D printing and subsequent post-processing, which leads to a significant change in surface texture.

Acknowledgment:
The research outlined in this paper received support from two specific research projects: “SV23-216” and “SV24-216” at the Department of Mechanical Engineering, University of Defence, Brno, and from the Project for the Development of the Organization “VAROPS (DZRO VAROPS) Military autonomous and robotic assets” by the Ministry of Defence of the Czech Republic.

Hybrid materials are increasingly used in lightweight construction. The combination of metallic materials with fiber-reinforced plastics (FRP) can reduce weight and improve the mechanical properties of a component. FRP are known for their lightweight and corrosion resistance, while metals show high strengths and stiffnesses. In order to combine the advantages of both materials, it is possible to reinforce highly stressed segments of a metallic component with FRP. This paper presents a novel method for manufacturing such hybrid metal-FRP composite structures using a multidirectional forming process. Therefore, a glass mat reinforced thermoplastic (GMT) consisting of a polypropylene matrix with 40% glass fiber reinforcement is compression moulded on local segments of a metallic component by a controllable multidirectional die to adjust the geometry. To achieve this efficiently, an appropriate application-oriented forming process must be designed using finite element (FE) simulations. In order to conduct a precise numerical study, a characterization of the GMT is necessary for the realistic modelling of the material flow during forming. Therefore, isothermal compression tests were conducted using a parallel-plate rheometer at different temperatures ranging from 160°C to 220°C and varying squeeze rates from 0.05 mm/s to 2 mm/s. The experimental data is used to fit a material model for the FE-simulations. To validate the material model for further simulations in the project, the forming process is simulated in ABAQUS using a Coupled Eulerian-Lagrange approach and the results are compared with the experimental data.

In this study, the comparative experimental research was performed to quantify the effect of distilled water absorption on the mechanical characteristics of composite samples. The composite samples were reinforced with para aramid fabric Twaron CT 747. The experimental part involved the fabrication of composites using three different methods: vacuum assisted resin transfer method (VARTM), autoclave technology and hot pressing technology. The fabricated samples were immersed in distilled water according to EN ISO 62. The highest water absorption was obtained for the samples produced by the hot pressing method and this value was 12.1%. Subsequently, mechanical tests were performed, specifically the tensile test according to EN ISO 527-1 and the three-point bending test according to EN ISO 178. The main objective was to compare the tensile and flexural properties of the unexposed and exposed samples. The highest tensile and flexural strengths were obtained for the samples produced by the VARTM method. For these samples, the decrease in tensile strength after immersion was 8.3%. The flexural strength of these samples decreased by 11.4% compared to the unexposed samples. The experimental results showed degradation in the mechanical properties of the samples that were immersed in distilled water. The extent of this degradation depended on the applied manufacturing technology.

Superconducting tapes made from Rare-Earth Barium Copper Oxide (REBCO), a type of High-Temperature Superconductor (HTS), are valuable due to their high capacity for carrying electrical current and their robust resistance to strong magnetic fields. They have significant potential for use in high-field magnet applications such as pulse magnets and particle accelerators. However, when subjected to transient or alternating magnetic fields, they exhibit high magnetization losses. To mitigate this, it is essential to narrow down the width of HTS tapes, which can be achieve through the striation of superconducting layer. During the process of striation, the superconductor is exposed at the edges of the grooves to ambient, potentially leading to its degradation. Hence, it is crucial to provide additional protection to these exposed areas. In order to boost the performance of REBCO tapes, the striated HTS tapes can be coated with protective multilayer materials. These coatings, typically applied using techniques like magnetron sputtering, serve various functions: shielding the superconductor from environmental damage, enhancing its mechanical resilience, and offering tailored thermal stabilization. In this study, we explore a range of materials to determine the most effective coating option. Adhesion test and measurement of electrical resistance was conducted on small samples featuring different coating systems, primary based on AlN and CuO. The selected materials were sputtered onto striated REBCO tapes, and their quality was evaluated using SEM and EDX analysis. Additionally, the samples underwent electrical measurements to comprehensively evaluate their performance.

The numerical process simulation has become a key tool to design the geometry of a metal casting and to optimise the casting process parameters. The integration of computer process simulation is replacing the traditional casting approaches, which are still nowadays based on trial-and-error method, allowing greater integrity of the final components. This work studied the fluid flow during the filling phase of a gas control valve produced by high pressure die casting. A commercial simulation software was used to simulate the process. The accuracy of the numerical filling process was assessed by conducting experimental interrupted filling tests. Computed x-ray tomography was used to evaluate the amount and distribution of casting defects throughout the component, and the results were compared with the quality criteria integrated into the numerical simulation software. The numerical method was then adopted to simulate the thermal distribution of the die halves, while the experimental surface temperatures were monitored by an infrared camera. The numerical simulation results showed a good agreement with the experimental data so evidencing the economic benefits traditionally linked with the exploitation of the numerical simulation tools.

An energy and environmental assessment of the processing of secondary raw materials during hydrometallurgical zinc production using the waelz process was made. The exergy method of thermodynamic analysis was used as a research method. A real operating installation at KCM SA - Plovdiv, Bulgaria serves as a model flowchart.
The research aims to carry out a precise assessment of the internal energy resources of the processes, suitable for carrying out work under the given environmental conditions. This fact allows to determine the thermodynamic improvement of the processes, as well as to evaluate the internal (irreversible) and external (effluent) losses of available energy. The data obtained from the study were used in the assessment of the anthropogenic load on the environment, influenced by the real production processes of processing of secondary raw materials.
The assessment was made by varying the amount of input secondary raw materials, as well as using different fuel (fuel oil and natural gas).
Residual anthropogenic emissions in the environment, namely heat emissions, gas emissions and solid waste, deserve serious attention.
The process of processing a larger amount of secondary raw materials using natural gas as fuel is characterized by higher energy efficiency and lower environmental impact.
This study is financed by the European Union-NextGeneration EU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project № BG-RRP-2.004-0001-C01"?

Major mines confront a gold deposit crisis, as what remains underground is becoming more and more challenging to process. These metals from the ore are not readily recoverable by standard extraction methods which proved ineffective Recently, greener solvents, such as deep eutectic solvents (DES) emerged for alternative leaching. The application of DES belongs to an emerging subfield of extractive metallurgy called solvometallurgy. This process resembles the hydrometallurgical method, but instead of using an aqueous solution, it employs a non-aqueous one. Using DESs like ethaline, a mixture of choline chloride (ChCl) and ethylene glycol (EG), are one of the more well-known options that shows less volatility and corrosivity. This paper aims to investigate the response of the gold metal leaching Deep Eutectic Solvent (DES) with the refractory ore at varying pH and molar ratios at 72-hour agitation time. Effects on oxidation-reduction potential (ORP) and temperature were also observed throughout the process. Statistical analyses were performed to investigate the dependency and effects of alkaline and acidic environment on the DES and gold dissolution. It was found that the 1:1 molar ratio yielded higher gold dissolution. Meanwhile, unique interactions were observed under acidic, neutral and basic settings affecting the gold dissolution process. The composition of redox species was a key factor that influenced ethaline's overall reduction potential. DES has complied with the standards for industrial applications for further optimization but nonetheless has shown promising results toward mitigation of environmental concerns.

Distinguished by its wealth in refractory gold deposits, Davao de Oro in the Philippines has historically relied on cyanidation for gold extraction. This method, while prevalent, employs toxic cyanide, leading to significant environmental and biological hazards. The urgency to develop less detrimental and more effective methods of extraction is evident. Hypochlorite has emerged as a viable reagent in the dissolution of refractory gold ores, presenting as an environmentally sustainable and safer alternative to the traditional cyanide-based processes in terms of production, utilization, and disposal. This study investigates the effects of various pH levels and hypochlorite concentrations on ore dissolution. Notably in the preliminary experimental runs, the specific ratios of sodium chloride (NaCl) to calcium hypochlorite (Ca(OCl)₂), particularly in the ratio of 15:15 and 20:10, demonstrated efficacy in solution environments maintaining a pH level of 6. The research aims to make a substantial contribution to the advancement of gold recovery methods, thereby providing a more environmentally conscious approach compared to the conventional cyanidation process.