Abstract: To enhance the surface protection of exposed moving parts made from magnesium alloys, this study focuses on developing high-performance micro-arc composite (MCC) coatings on AZ80 wrought magnesium alloy substrate. AZ80 alloys were fabricated through forging at different temperatures (250℃, 350℃, and 450℃) to investigate the influence of thermal deformation on substrate properties. Subsequently, micro-arc oxidation (MAO) coatings and MCC coatings were applied to the forged alloys. Comprehensive analyses—including microstructural characterization, salt spray corrosion tests, and stress corrosion cracking (SCC) evaluations—were conducted under both static and stress conditions. Among the forging temperatures, 250℃ produced substrates with refined grains and a favorable distribution of β-Mg17Al12 precipitates, resulting in improved baseline corrosion resistance. MAO coatings offered moderate protection, primarily delaying corrosion initiation and crack propagation under stress environments. Building upon this foundation, MCC coatings—fabricated by electrostatic spraying to form an inner-embedded and outer-wrapped structure over the MAO layer—demonstrated significantly superior protective performance. Under both static and stress corrosion scenarios, the MCC coatings effectively suppressed SCC initiation and progression, highlighting their potential for robust surface protection in demanding service environments.

Abstract: The rising demand for lithium-ion batteries (LIBs), driven by the growing consumption of electronic devices and the expansion of electric vehicles, is leading to a concerning depletion of primary metal resources and a significant accumulation of electronic waste. This urgent challenge highlights the need for sustainable recovery methods to extract valuable metals from spent LIBs, aligning with circular economy principles. In this study, the preparation of spent batteries for the bioleaching process was achieved with minimal manipulation. This included a preliminary discharge to ensure safety in subsequent processes and a brief crushing to facilitate the access of leaching agents to valuable metals. Unlike most studies that grind batteries to obtain powders between 70 and 200 microns, our approach works with particles sized around 5mm. Additionally, our preparation process avoids any thermal or chemical treatments. This straightforward pre-treatment process marks a significant advancement by reducing the complexity and cost of processing. A systematic study was conducted on various fractions of the large particle sizes, using Fe (III) produced through biooxidation by A. ferrooxidans and biogenically obtained H2SO4 from A. thiooxidans. The highest metal extraction rates were achieved using the unsorted fraction, directly obtained from the black mass after the grinding process, without additional particle separation. When treated with bio-oxidized Fe (III), this fraction achieved a 95% recovery of Cu, Ni, and Al within 20 minutes, and over 90% recovery of Co, Mn, and Li within approximately 30 minutes. These recovery rates are attributed to the combined reducing power of Al and Cu already present in the black mass and the Fe(II) generated during the oxidation reactions of metallic Cu and Al. These elements actively facilitate the reduction of transition metal oxides into their more soluble, lower-valence states, enhancing the overall metal solubilization process. The extraction was carried out at room temperature in an acidic medium with a pH no lower than 1.5. These results demonstrate significant potential for efficient metal recovery from spent batteries with minimal pretreatment, minimizing environmental impact. Additionally, the simplified residue preparation process can be easily integrated into existing waste management facilities without the need for additional equipment.

Abstract: In this study, the CrCuFeNiTiAl1 equiatomic alloy was used as a base, which was modified by adding graphite in proportions of 0.5, 1.0, 2.5, and 5.0 mol%. The samples were obtained by powder metallurgy and sintering at 1,200°C for 2 h in a furnace with a protective argon atmosphere. The structural characterization was performed by XRD. Microstructural evaluation was determined by SEM. The best mechanical microhardness and compressive strength results were obtained in the samples with the lowest amount of graphite (238 mHV and 1000 MPa, respectively). Density values showed that samples with low amounts of graphite have better densification, lower porosity, and finer structural characteristics than those with graphite percentages higher than 1 mol%. The XRD studies determined the formation of a mixture of crystalline structures composed of FCC due to the presence of Cu, Ni, and Al metals, BCC due to Fe and Cr metals, and HCP due to Ti, and the formation of Cr7C3 compound. SEM analysis showed the formation of cracks and porosity due to the formation of carbides.

Abstract: This research focuses on finding an environmentally friendly method to extract gold from a sulfide flotation concentrate. In this study, an ammonia-copper-thiosulfate leaching system was utilized for the extraction of gold. The flotation concentrate sample contains about 190 ppm of gold, 160 ppm of silver, and 6.89 % of copper. To achieve an optimized gold extraction, various, parameters such as thiosulfate, ammonia and copper concentrations, pulp density, pH, stirring rate, temperature, and time were investigated. About 88 % of gold was leached under the following conditions: 0.5 M S2O32-, 1.0 M NH3, 0.1M Cu2+, 350 rpm, pH 12, 10 % solids, 25 ˚C, and 2 hours. Additionally, to improve the economic effectiveness of the leaching system, thiosulfate consumption was investigated by utilizing different additives such as diethylenetriamine (DETA), glycerol, and ammonium dihydrogen phosphate (ADP). The results showed that with the use of ADP, gold extraction increased from 88 % to 91 % while reducing copper dissolution. Additionally, the thiosulfate consumption also decreased from 0.37 M to 0.3 M. The inclusion of ADP was particularly effective, enhancing gold extraction efficiency and reducing reagent consumption, thereby making the process more sustainable. Considering the high economic value of gold, the optimization of recovery efficiency is prioritized over reagent costs in this study. Overall, the study indicates the optimized ammonia-copper-thiosulfate leaching system with ADP additive is a promising environmentally friendly method for the extraction of gold.

Abstract: High-entropy alloys (HEAs) offer a platform for designing microstructures suited to extreme conditions. Dual-phase HEAs show promising strength-ductility combinations at high temperatures, but maintaining phase stability above 800°C remains challenging. This study introduces a novel dual-phase HEA (FCC + BCC) with microstructural evolution driven by spinodal decomposition and intermetallic stabilization. The alloy transitions from initial FCC to mixed FCC-BCC laths, with spinodal nanophases in the BCC matrix. Coarse σ (FeCr-type) and NiZr-rich intermetallics form at phase boundaries, enhancing stability. Post-solidification analysis shows σ phase consuming spinodal BCC at high temperatures, while retained nanoscale BCC spinodal contributes to strain incompatibility and HDI hardening. This interplay balances phase stability and mechanical performance. Compressive tests at 800-1000°C (strain rate 1/s) reveal phase stability and deformation mechanisms. Behavior is governed by lamellar morphology and σ/α-Cr ↔ B2 interactions. Retained GNDs and enhanced twinning sustain work hardening up to 900°C. At 1000°C, FCC-dominated strain localization triggers rapid softening via dynamic recrystallization. These findings deepen understanding of high-temperature deformation in dual-phase HEAs, offering pathways for optimizing alloy design in extreme environments.

Abstract: The principles of the friction welding (FW) process of the two different non-ferrous metals, aluminum and copper, are presented in this paper. Considering that the bimetallic Al-Cu joints find applications in electrical engineering, as well as in other industrial fields, the basic characteristics and compatibility of these metals are discussed, along with the influence of various parameters on the properties of their friction welded joint. The experimental study involved determining and analyzing the effects of process parameters on the occurrence, shape, and level of plastic deformation resulting from changes in the physical model during the rotational friction welding process (RFW). The specificity of the joining process is in the occurrence of various phenomena in the weld zone, which are significantly affecting the physical, structural, and mechanical properties of the base materials, thus influencing the joint quality. The friction welding process itself is complex, and the task is further complicated by the use of different base materials.

Abstract: Despite their excellent mechanical properties, martensitic stainless steels present significant welding challenges due to their susceptibility to cracking and forming brittle microstructures during thermal cycles. While electron beam welding offers advantages through its high energy density and precise control over conventional welding methods, the induced residual stresses remain a critical concern. This study aims to determine surface residual stresses in electron beam welded AISI 410 martensitic stainless steel using a self-developed C-scan mode Magnetic Barkhausen Noise (MBN) measurement system. A novel calibration and measurement methodology was developed to establish a quantitative relationship between MBN signals and residual stress state. The residual stresses in the welded specimens were analyzed systematically using MBN and X-ray diffraction (XRD) measurements and microstructural characterization. The results revealed a strong correlation between MBN parameters and residual stress states, showing notable variations across the weld zones, i.e., approximately +350 MPa in the heat-affected zone and -50 MPa in the base metal. The experimental findings were also validated through finite element simulations. The correlation between experimental and numerical results confirms the reliability of the proposed MBN-based methodology and system. These findings provide valuable insights for industrial applications, offering a rapid and reliable non-destructive method for residual stress assessment in critical welded components.

Abstract: The HVOF (High Velocity Oxy-Fuel) thermal spraying method is widely used in surface engineering to produce coatings with high hardness, low porosity and high crack resistance. Composite coatings with particles of chromium carbide (Cr₃C₂) in a nickel-chromium alloy (NiCr) matrix are used in demanding operating conditions, such as the energy and transport sectors. The study aims to compare the microstructure, micro-mechanical and tribological properties and corrosion resistance of two types of coatings: Cr₃C₂-25(Ni20Cr)-10(Ni) and Cr₃C₂-25(Ni20Cr), deposited by the HVOF method on a ductile cast iron substrate. Particular attention is paid to the influence of nickel (Ni) particles on the microstructure, mechanical properties, wear resistance and corrosion in the context of improving the service life of coatings. The study included microstructure analysis using light microscopy (LM) and scanning electron microscopy (SEM), as well as chemical and phase composition analysis in micro-areas using EDS and XRD techniques. The results show that the Cr₃C₂-25(Ni20Cr) coating enriched with Ni particles was characterised by a compact structure with low porosity and high hardness. Its microstructure consists of large, partially melted Ni particles and fine carbide particles (Cr₃C₂ and Cr₇C₃) embedded in the NiCr matrix, some of which reach submicron sizes. Performance tests, including indentation tests (HIT, EIT, KIC) as well as scratch and corrosion resistance tests, confirmed that the presence of Ni particles increases the coating's resistance to cracking, wear and corrosion. As a result, these coatings are characterised by higher operational durability, making them more effective in difficult working conditions.

Abstract:

Recent advances in artificial intelligence have intensified efforts to improve quality management in the steel manufacturing. In this paper we will present the development and results of a system that aims to learn from the decisions made by experts to anticipate the problems that affect the final quality of the product in the steel rolling process. The system integrates a series of modules including event filtering, automatic expert knowledge extraction, and decision-making neural networks developed in a phased approach. Experimental results show that our system anticipates quality issues with an accuracy of approximately 80%, enabling proactive defect prevention and reduction in production losses. This approach demonstrates the potential for industrial AI applications for predictive quality assurance, highlighting its technical foundations and potential for industrial application.

Abstract:

For the extraction of cobalt from cobalt-rich alloy slag, ammonia was considered a lixiviant with limited environmental impact compared to acid lixiviant. However, problems such as large ammonia volatilization loss, toxic vapor emissions, and suboptimal process control were encountered during ammonia leaching. To address these issues, a new method was proposed for recovering cobalt via selective complexing leaching, where an alkaline histidine solution was utilized instead of ammonia. A high cobalt leaching rate of 99% was achieved under the following conditions: a leaching temperature of 35℃, a histidine/cobalt molar ratio of 1.5, a pH range of 6–11, a leaching duration of 6 hours, and a stirring speed of 300 rpm. In the verification test for the leaching of Cu-Co alloy slag with histidine, cobalt was almost entirely leached, while iron, lead, and copper were observed to be difficult to leach. The kinetic analysis of the cobalt leaching process revealed that electrons were donated to Co²⁺ by the amino and COO⁻ groups in histidine during the coordination reaction. This confirmed that a soluble complex, Co(C₆H₉N₃O₂)₂, was formed through coordination between histidine and Co²⁺.

Abstract: In this study, the high-temperature thermal deformation behavior of TA4 alloy was investigated through thermal compression experiments. The effects of deformation temperature and strain rate on rheological stress were analyzed by examining the variations in stress-strain curves under different conditions and establishing a constitutive equation based on the dynamic material theory model. The prediction accuracy of the developed constitutive model was evaluated, yielding a correlation coefficient of 0.9612 between predicted and experimental values, an average absolute percentage error of 8.7210%, and an average root mean square error of 11.0635 MPa. Thermal processing diagrams were established and plotted to analyze the optimal processing zone and the destabilization zone under different strains. The optimal processing zones at different strains are obtained from the thermal processing diagrams, which are 1040~1133K, 0.01~0.7s-1 at a strain of 0.9, 940~1000K, 0.01~0.04 s-1 at a strain of 0.6, 940~1000K, 0.01~0.08s-1 at a strain of 0.3, 940~1000K, 0.01~0.08s-1 at a strain of 0.3. Additionally, the thermal deformation mechanisms of TA4 alloy under varying deformation parameters were analyzed using EBSD characterization. The results indicate that the primary deformation softening mechanisms include dynamic recovery (DRV) at low temperatures and high strain rates, dynamic recrystallization (DRX) at high temperatures and high strain rates, and DRX at low strain rates.

Abstract:

316L steel is widely used in various industries and is also one of the metallic materials for biomedical applications because of its excellent mechanical properties, corrosion resistance, and biocompatibility. This article reports a comprehensive study on the effects of equal channel angular pressing (ECAP) and subsequent recovery treatment on the microstructure, mechanical, tribiological, and corrosion properties of 316L. The process includes initial annealing at 1050℃ for 2 hours to get homogenous microstructure, ECAP at room temperature with 120° inner angle, and subsequent recovery treatment at 340℃ for 1 hour. Microstructure was investigated with an optical microscope and transmission electron microscope. The mechanical properties were evaluated with hardness and compression tests. Corrosion behavior was analyzed with polarization dynamic tests. The wear test was performed using a scratching tester, and the volume loss was measured with a profilometer. Results of the study show that the ECAP-recovery sample exhibits improved properties than the annealed sample and ECAP sample. The corrosion tests show that the ECAP sample has a corrosion resistance higher than that of the annealed but lower than that of the ECAP-recovery sample. ECAP-recovery sample shows the highest wear resistance and corrosive wear resistance among the three samples.

Abstract:

This article discusses a new method for estimating the amount of dust released from a converter bath during the oxygen purging of phosphorous cast iron. This method allows us to determine how technological solutions and blast modes affect the environmental performance of the process.This study identified the causes of increased dust generation and developed solutions to improve environmental performance. Dust and gas emissions in the converter shop can be divided into two categories: organized and unorganized. Organized emissions are captured when exiting the converter neck, and draining unorganized emissions occur periodically during the casting of iron, loading scrap, and other processes. These emissions contain dust, heat, carbon monoxide, nitrogen and sulfur oxides, as well as fluorides.Resource-saving technology using inactive slag reduces the release of dust and gases by using active foam slag at the initial stage of purging and reducing lime consumption. Matching the volume of gases to the throughput of the path reduces dust removal by 30–40% and unorganized emissions by 83%. The reduction in carbon monoxide emissions is achieved by increasing the rate of increase in the CO concentration to the ignition limits, followed by afterburning on a "candle" and the organization of melting with a shortened first period. Reducing the phosphorus content in cast iron to 0.3% reduces lime consumption from 143 to 77 kg/ton of steel, reduces the duration of purging and smelting by 10-16%, reduces lime production and increases converter productivity.An integrated approach to reducing dust and gas emissions includes process optimization, the introduction of new materials and technologies, and monitoring and analysis of indicators. This improves the environment and increases production efficiency.

Abstract: Kinetic parameters that describe phase transformation and precipitation rates include the activation energy. In Al based alloys, volume fractions of precipitates, the melting temperature of specific phases and the activation energy of reactions can, in most cases, be determined by the differential scanning calorimetry (DSC) technique. In this investigation, DSC measurments were performed on a SETARAM SETSYS Evolution-1200 thermal analyzer on recycled aluminium alloy 2017A in the range of temperature from room ~25 to 700°C and different scan rates of heating at 5,10,15, 20 and 25°C min-1. The peak temperatures of the clusters, GP zones and hardening phases ’"and  Q from each heating rate were collected to calculate the activation energy associated with precipitation reactions in aluminium alloy 2017A using various mathematical models: the Kissinger, Ozawa and Boswell. The results (XRD, LM, TEM, DSC) show that both the θ and Q phases are strengthening phases, but the strengthening effect of the ",  phases is dominant. The strengthening phases, mainly ", ' increase the hardness during natural aging. The maximum hardness value 128HB was obtained after ~25h of natural ageing. The activation energy of precipitation of strengthening phase θ” in 2017A aluminum alloy determined by Kissinger, Ozawa and Boswell models are: 89.94  kJ· mol−1, 98.7  kJ· mol−1 and 94.33  kJ· mol−1 respectively and for θ’: 72.5  kJ· mol−1, 81.9  kJ· mol−1 and 77.2  kJ· mol−1 .

Abstract:

The production of automotive steel sheets achieved by the compact steel production (CSP) process has become an ongoing research topic in industry due to the global demand for decarbonization. Identifying the hot deformation behaviors, especially the metadynamic softening mechanism between passes is critical to drawing the picture of processability under the character of the CSP process. In this study, the metadynamic softening behavior of CP800 steel which is prepared for the application CSP process was investigated through the isothermal double compression tests which were carried out at the deformation temperatures of 1173, 1273, and 1373 K, and strain rates of 0.1,1, and 5.0 s⁻¹, and the interpass times of 1, 10, and 20 s. The softening behavior was discussed through the deformation flow stress-strain curves under different conditions. The kinetic equation of metadynamic recrystallization is proposed and examined with experimental results. The effect of 42 μm and 92 μm two different sizes of initial austenite grains on metadynamic recrystallization were analyzed. The obtained findings of this study are highly recommended for the design and optimization of the application of the CSP process when producing CP800 steel.

Abstract: Understanding the constituent phases and their corresponding phase transformations are crucial for the determination of the performance and application characteristics of the alloy systems. The methodology in the Fe-0.8 C-8.3 Mn-16.9 Al (at.%) alloy included the annealing at and air cooling from 1100°C. This study investigates the minor Widmanstätten side-plate precipitates (ppts) distributed uniformly in the major body-centered cubic (BCC) matrix. During air-cooling, a face centered cubic (FCC) phase precipitated in the BCC matrix in the form of the Widmanstätten side-plates through a precipitation transformation. Upon further cooling, the high-temperature FCC phase underwent the spinodal decomposition and decomposed into two low-temperature FCC phases, that is, solute-lean FCC′ and solute-enriched FCC′′. The FCCꞌꞌ phase in the form of nanosized particles precipitated homogeneously in the FCCꞌ matrix. For the alloy after further cooling, an ordering reaction occurred, and the solute-enriched FCC′′ phase transformed into the L12 phase. Therefore, The Widmanstätten side-plate ppt consists of duplex FCC and L12 phases. The nanosized L12 particles precipitated homogeneously in the FCC matrix. The insights gained from this study contribute to deeper understandings of phase stability and transformation mechanisms in Fe-Mn-Al alloys, which can inform their future design.

Abstract: In the mining industry the most energy/demanding activity is particle size reduction, i.e. comminution. Blasting is the first stage of comminution. It has been experimentally and by field observation demonstrated that blasting produces two effects on rock: i) it produces macroscopic fracturing, fragmentation; ii) it generates microscopic fracturing, a series of microfractures that weaken the rock, reducing the specific Work Index, therefore making it less resistant to crushing and milling. The present work is aimed to verify the following hypothesis: do smaller particles, having been macroscopically more affected by blasting, also possess a higher degree of microfractures, therefore being less resistant to grinding? To verify this hypothesis we analyzed blasted rock under three test dominions: macroscopic testing via point loading, laboratory grinding testing via Bond’s mill to determine the blasted Work Index and microscopic optical observation of microfractures. The results show that macroscopic testing cannot appreciate microscopic weakening (no correlation between point load results and particle size). On the other hand, laboratory ball mill and microscopic optical observation results show a direct correlation between particle size and internal weakening of particles. The results are evidence, albeit very preliminary, that the Work Index might not be a constant within a given volume of blasted rock, and it could be a function of particle size distribution.

Abstract:

A drainless energy-saving technology for processing highly moist iron-containing sludge from metallurgical production has been developed. The patterns of the combined process of chemical dewatering of highly moist iron-containing sludge with pulverized lime and dolomite wastes, hardening and caking by pressing in a single technological cycle at the developed experimental facility are investigated. In the course of laboratory studies, the temperature of the mass, rate of dehydration, chemical composition of the mixtures, appearance of the resulting briquettes, weight loss during caking, moisture content of the mixtures, and mechanical strength of the briquettes were monitored. New patterns have been established that have made it possible to develop an annealing-free method for producing iron-containing materials and self-healing briquettes. The essence of this method, which is one of the main provisions of scientific novelty, combines the processes of dehydration self-curing of the mixture with the process of forming by applying external pressure to the hardening mixture in molds to obtain a lumped material in the form of briquettes in a single technological cycle. The proposed technology does not require drying and firing, and a set of strength properties occurs as the material cools in the air during the day. A new energy-efficient and waste-free method for the production of iron-containing briquettes has been developed, combining the processes of chemical dehydration and condensation in one technological cycle. The proposed project and technology will make it possible to organize production for the processing of highly moist iron-containing sludge and the production of complex iron-containing material as a secondary metal-containing raw material for metallurgical plants for the production of steel and rolled metal. This technology will make it possible to fully utilize not only iron-containing sludge but also finely ground limestone and dolomite roasting waste (limestone and dolomite dust of dry gas purification) as dehydrating and binders, as well as screening coke and coal as reducing agents. The proposed technology also solves the problems of environmental pollution and the allocation of land for the storage of industrial waste.

Abstract: The removal of prosthetic implants, although normally necessary following the recovery of patients, inevitably has disadvantages in terms of costs, further pains and possible post-operative infections. A promising alternative is represented using bioresorbable implant structures. The magnesium alloy-based devices could be ideal candidate due to their poor corrosion resistance and high biocompatibility, but their degradation rate is dissimilar to that of hosting tissues healing. Therefore, a growing interest is addressed to design new magnesium alloys with a slow degradation process or to modify the surface of known magnesium alloys. This paper aims to investigate the enhancement of corrosion resistance of a protective system applied on the AZ31 magnesium alloy composed of three different superimposed layers: a) magnesium-based oxide, b) polydopamine and c) polylactic acid. Morphological and chemical analysis were performed. Roughness and microhardness measurements were carried out. Electrochemical behavior was studied in the Hanks’ solution at 37 °C. As expected, the findings showed that the magnesium oxide layer is able to reduce the degradation rate, in contrast to the polydopamine layer, that negatively affected the barrier protection of the only anodization. However, the presence of polydopamine together with the polylactic acid film improved the corrosion resistance of the alloy. Thus, the multilayers should represent a protective system to control the degradation process.

Abstract: The microstructure evolution, polarization curve and impedance of cold-rolled 0.2%C–3%Al–6/8.5%Mn–Fe steel under heat treatment temperatures of 600–800 ℃ holding 10 minutes were tested. The results show that the cold-rolled texture of the steel does not completely disappear at 600 ℃ and 650 ℃, exhibiting high charge transfer resistance Rc and corresponding corrosion potential Ecorr. When the heat treatment temperature rises to 700 ℃, the texture begins to eliminate, the Rc begins to decrease, indicating a decrease in corrosion resistance. When the heat treatment temperature rises to 750 ℃ and 800 ℃, it can be found that the proportion of austenite begins to increase and the number of grain boundaries decrease, resulting in an increase in Rc and an improvement in the corrosion resistance of the steel. Compared to 6.5Mn steel, the higher Mn content in 8.5Mn steel results in better corrosion resistance after high-temperature heat treatment.