Article

Elena Bruce, Rossana Sepúlveda

Mathematical modeling of columnar leaching is a useful tool for predicting and evaluating the kinetics of copper extraction. One commonly used model for this process is the shrinking core model (SCM). In this study, the aim was to develop a model for column leaching of oxidized copper ore based on the SCM, which incorporates the ore sulfation stage before leaching. In sulfation and leaching laboratory-scale tests, we studied the effect of acid dosage (at 22.8, 34.2, and 45.6 kg/t), humidity (at 90%, 100%, and 110% of the saturation humidity of the mineral), ore granulometry (−3/4′′ and −3/8′′), and rest time (at 24, 48, 72, and 96 h) on sulfation. We found that the highest sulfation reached 49.7% for both granulometries in studies. In the column tests, the effects of acid dosage (at 34.2, 45.6 kg/t), ore granulometry (−3/4′′, −3/8′′), and rest time (at 24, 48 h) were studied. When the SCM was applied to these tests, we obtained fit qualities within 63.4% and 74.9%. By incorporating the sulfation factor into the SCM predictions, we observed an average increase in adjustment between 24% and 28%. This method is effective for minerals and operating cond.

Alpha Chi Him Tsang, Jing Ji

With the popularization of electric vehicles, lithium-ion batteries (LIBs) have begun to be used in large quantities, and the scale of the waste batteries is large and growing rapidly. So, the environmental pressure faced and the economic benefits contained in waste batteries are rapidly increasing every year. The valuable metals (e.g., Ni, Co and Mn) in the cathodes of LIBs are important non-renewable resources with high recovery value. So, the recovery and reuse of valuable metals in waste LIBs have constituted an important issue of concern. This review focuses on the hydrometallurgy of spent-LIB cathode, the extraction of valuable metals (solvent extraction and filtration), and co-precipitation methods. A perspective and outlook associated with the challenges and limitations of current hydrometallurgy research is proposed for breakthrough development of such technology for future industrialization.

Yevhen Synehin, Volodymyr Ruban

This study investigates the process that forms centerline porosity in the axial zone of a continuously cast steel billet during its hardening. The task addressed relates to the need to establish rational parameters for the temperature-speed mode of casting to minimize axial porosity, which is critical for increasing the density of the metal and the quality of rolled products. A comprehensive methodology for physical modeling of the hardening process using stearin as a model substance has been devised. Based on the analysis of similarity numbers (Biot, Fourier, Kosovych), the exact scales of modeling were established: by time – 1.854, by linear dimensions – 0.1778, by heat transfer coefficient – 0.04639. It was determined that for an adequate simulation of the formation of the bloom blank, the closing angle of the liquid core varies within 2.3–6°. Quantitative parameters of the experiment on the model were established: overheating of the melt in the range of 1.8–4.2°C, which corresponds to 15–35°C for steel. The resulting data are explained by the laws of convection heat transfer and phase transition. The angle of inclination of the crystallization front and the intensity of heat removal determine the moment of formation of 'bridges' and interceptions in the thermal center, which directly defines the morphology and volume of shrinkage pores.

Öznur KILIÇ, Kerem Altuğ GÜLER

In this study, different melting and refining strategies were applied to G17CrMo5-5 cast steel in order to evaluate their influence on inclusion evolution and microstructural cleanliness. The objective was to determine how variations in the Argon Oxygen Decarburization (AOD) process can affect the morphological characteristics of inclusions within the steel matrix, which is critical for enhancing mechanical properties and performance. A systematic methodology was developed, involving the comparison of metallurgical outcomes from several experimental batches subjected to distinct refining techniques. The results indicate that the refining conditions significantly influenced the size, distribution, and composition of inclusions, as well as the overall microstructural integrity of the cast steel. Notably, improvements in cleanliness were observed, leading to a more favorable microstructure that enhances the material's mechanical properties. These findings contribute valuable insights to the field of materials engineering and have practical implications for the processing of high-performance cast steels. The study underscores the importance of optimizing refining processes to achieve desired material characteristics.

Daria Togobitska, Allа Bielkova

This work presents a systematic approach to describing the physicochemical processes occurring in the metal-slag system during steel refining in a ladle furnace. The aim of the study was to develop methods for predicting the distribution of main and impurity elements based on a comprehensive analysis of the initial and final melts of metal and slag. Industrial data on the chemical composition of SAE1006 grade steel and the corresponding slag were used as the input. Based on the methodological framework of the Directed Chemical Bonding Concept (DCBC) and mathematical processing of multivariate data, the applicability of interatomic interaction parameters and technological regime indicators as model parameters was substantiated. Complex indicators for the metal-slag and metal-additive systems were constructed using Harrington’s desirability function, which enables integration of multidimensional parameters into a single generalized index. Analytical dependencies were developed for calculating the distribution coefficients of sulphur (S), silicon (Si), manganese (Mn), and aluminium (Al), considering both the composition of metallurgical phases and the smelting conditions. The proposed approach provides a quantitative assessment of the distribution coefficients of elements as variable quantities, which fundamentally distinguishes it from traditional methods. The results obtained form the basis for developing algorithms to predict the chemical composition of the final melt and for creating practical recommendations on the selection of optimal additives and slag-forming mixtures aimed at improving steel quality and reducing production costs.

Fuhai LIU, Tantong SHI

The study explores the application of the CO2 bottom-blowing method in the 120t LF (Ladle Furnace) refining process to improve metallurgical outcomes. The objective was to evaluate the effectiveness of CO2 over traditional argon methods in achieving inclusion removal and quality enhancement in molten steel. Utilizing both experimental setups and numerical modeling, various bottom-blowing rates and gas types were analyzed to determine their impact on metallurgical properties during the refining process. Results indicated that the CO2 method significantly influences the total inclusion removal rate and size distribution of inclusions, outperforming the argon method in certain conditions. Key findings include improved removal rates of non-metallic inclusions and favorable changes in chemical composition, such as carbon and sulfur levels, leading to enhanced steel quality. Additionally, operational parameters such as temperature variations and refining time were assessed, confirming the potential of CO2 as an effective agent in steel refining applications. This research provides valuable insights into optimizing refining processes using innovative methods, ultimately contributing to advancements in metallurgical engineering and carbon neutrality efforts in steel production.

Erhan SELÇUK, Kerim Emre ÖKSÜZ

This study investigates the effect of the vibratory assisted severe surface plastic deformation (VA–SPD) method on the mechanical properties of Ti6Al4V alloy. The primary objective was to assess the enhancements in mechanical characterization resulting from this innovative surface modification technique. A systematic approach involving experimental procedures was adopted to analyze the material's response to the VA–SPD method. Various mechanical tests were conducted, including hardness and tensile strength assessments, to quantify the changes in the alloy's properties. The results demonstrated significant improvements in strength and hardness, attributed to the refined microstructure and increased dislocation density induced by the VA–SPD process. Furthermore, the study highlighted the potential of VA–SPD as a viable alternative for enhancing the performance and durability of Ti6Al4V alloy in various industrial applications, particularly in aerospace and biomedical fields. Overall, the findings provide crucial insights into the mechanical characterization of titanium alloys subjected to advanced surface deformation techniques.

M. Bronovets, P. Bukovskiy

Rolling bearings are among the most common components, used in virtually all branches of industry—from bicycles to space stations, including industrial and machinery equipment, automobiles, aircraft, rockets, and household appliances. Residual stresses and surface quality play a significant role in enhancing the tribological characteristics of friction pairs. Laser shock peening (LSP) is a promising method for residual stresses design, allowing for their magnitude and depth to be varied over a wide range. This study involved the LSP of friction pairs made from high-chromium bearing steel grade AISI 440-С (95 Х18Ш in Russia). The results demonstrate significant improvements in tribological characteristics under both dry and boundary friction conditions. LSP led to a change in the wear mechanism, which in turn reduces wear.

Wei Xu, Gaojian You

The surface properties of aviation titanium alloy directly affect its service safety and reliability, and high-performance coating are essential for its practical application. However, existing studies lack clear guidance on laser power parameters for preparing high-quality TiAl coating on titanium alloy substrates, leaving a research gap in optimizing coating quality and performance. To fill this gap, this work used selective laser melting (SLM) to fabricate TiAl coating on titanium alloy substrates, focusing on the influence of laser power (350–380 W) on coating microstructure, phase composition, elemental distribution and microhardness. SEM, XRD and EDS characterizations were used for systematic analysis. The results show that laser power is the key factor determining coating quality. Severe longitudinal cracks appeared at 350 W and improved microhardness and coating uniformity were observed at higher laser powers.

Zhiyuan Sun, Renjie Su

Bearing steel, as the core material of key transmission and support components, has its surface performance directly determining the reliability, stability, and service life of the bearing system. To address this, research has established four major surface modification technology systems: surface mechanical strengthening, surface heat treatment strengthening, surface coating strengthening, and hybrid strengthening. This review systematically summarizes the progress of these four systems, focusing on their strengthening mechanisms, microstructural evolution, and effects on the service performance of bearings. Surface mechanical strengthening improves the surface layer’s resistance to crack initiation and propagation through grain refinement induced by existing methodologies. Furthermore, surface heat treatment enhances durability by altering the microstructure, while surface coatings provide an additional layer of protection against wear and corrosion. The advancements in hybrid strengthening also show promising results by combining multiple technologies for superior performance. These developments not only extend the lifespan of bearing steels but also enhance their application in demanding environments.

Erika van Tonder

This thesis investigates the effect of ore blends on milling and flotation performance. Anglo Platinum’s Waterval UG2 concentrator in Rustenburg processes ore from various shafts. The thesis was initiated to gain a better understanding of the type of interactions between the ores that consequently affect metal accounting at the concentrator. Four ores were sourced from the following shafts: Salene ore (x1), Waterval UG2 ore (x2), Paardekraal ore (x3) and Townlands ore (x4). The literature review indicates various experimental mixture designs that could possibly be used. The mixture designs that are most evident in the literature are the simplex centroid design, the simplex lattice design and the axial (augmented) design. The simplex lattice design was selected for this research as it is commonly used in, for example, the pharmaceutical industry, chemical industry and the food industry. None of these mixture designs has ever previously been applied to the field of mineral processing and the thesis aimed to establish the experimental mixture design as a foundation for a methodology to evaluate and interpret the effect of ore blends. The thesis involved the characterization of four pure ores. Laboratory milling and flotation tests were conducted in order to standardize a milling time and quantify the uncertainty around the test work.

Kaiyu Zhou, Somasekhara Goud Sontti

The massive volume of oil sands tailings has been one of the most challenging environmental issues. In this work, we experimentally explore a simple and effective approach to bitumen residue separation from a highly concentrated slurry flow of the artificial oil sands tailings. By utilizing microbubbles from in-situ catalytic decomposition of hydrogen peroxide (H2O2) at low concentrations, bitumen aggregation is enhanced on the top part of the hydrotransport pipeline. The microscopic image analysis revealed the in-situ formation of microbubbles and confirmed that magnetic particles present in the slurries contributed to the fast release of the gas products and bubble formation from H2O2 decomposition. A high-speed camera was applied to capture images of the tailings flow in the pipeline through a transparent view window. A large number of tiny bubbles were identified post to the injection of H2O2 to the slurry flow. More than 70% bitumen could be recovered from a lab-scale pipeline loop within 30 mins after H2O2 injection. The bitumen recovery efficiency from the collected froth was quantitatively compared under seven conditions with varied dosages, the concentration of H2O2, and the amount of magnetic solids in the slurries. Our results confirmed that the total dosage of H2O2 is the dominant factor in in-situ microbubble formation for enhanced bitumen aggregation in the flow. Importantly, microbubbles were generated rapidly in the real mature fine tailings. The results from our study provide insights into the preferential distribution of oil residue in the flow during hydrotransport without the requirement for an additional device. Removal of oily residues from concentrated slurries may bring economical and environmental advantages.

Paulina Quintanilla, Daniel Navia

We present the implementation of a novel economic model predictive control (E-MPC) strategy for froth flotation, the largest tonnage mineral separation process. A previously calibrated and validated dynamic model incorporating froth physics was used, which overcomes the limitations of previous simplified models reported in the literature. The E-MPC’s optimal control problem was solved using full discretization with orthogonal collocation over finite elements, employing automatic differentiation via CasADi. This approach was applied in a 30-litre laboratory-scale flotation cell, significantly improving mineral recovery from 9% to 29% under feed flowrate disturbances while maintaining a minimum concentrate grade of 20%.

Franziska Strube, Thomas Wilhelm

The demand for lithium, as well as other critical resources, needed for electrochemical energy storage is expected to grow significantly in the future. Slags obtained from pyrometallurgical recycling represent a promising resource of valuable materials, among them lithium and rare earth elements found in artificial minerals particulate phases. This study investigates the flotation separation of engineered artificial minerals (EnAMs) in slags, such as lithium aluminate and gehlenite as valuable and gangue phases, respectively. Flotation experiments are carried out in a Partridge-Smith cell using oleic acid (OA) as a benchmark surfactant. Particle characterization is performed using SEM-based Mineral Liberation Analysis (MLA), which provides particle discrete information. From this information, bivariate Tromp functions based on non-parametric kernel density estimation are computed to characterize the separation behavior with respect to particle descriptors. This approach enables investigating the influence of particle size and shape on separation behavior of EnAMs. Furthermore, these results allow for the optimization of flotation experiments for enriching Li-bearing EnAMs.

J. M. Kazumba

Dans les procédés hydrométallurgiques, la maîtrise des performances des échangeurs de chaleur à plaques est essentielle à la stabilité thermique et à l’efficacité énergétique des installations. Dans cette étude, nous avons proposé une approche hybride pour modéliser les performances de l’échangeur industriel a plaques 60HX002 de MMG Kinsevere, à Lubumbashi (RD Congo), soumis à des conditions d’exploitation variables et à des comportements non linéaires et rechercher des conditions opératoires associées à un performance thermique cible. La méthodologie combine un modèle flou de Takagi –Sugeno généré par clustering soustractif, un système d’inférence neuro-flou adaptatif (ANFIS) et une simulation Monte -Carlo. Sur 2367 observations industrielles, le modèle ANFIS a atteint R2=0,894, une RMSE de 429 W/m²K et une MAE de 160 W/m²K. La validation croisée à cinq plis a confirmé sa stabilité prédictive avec R 2=0,892±0,020. Une première simulation Monte-Carlo a mis en évidence les limites d’un échantillonnage indépendant des variables opératoires, tandis qu’une simulation inverse contrainte de 50000 scénarios a identifié 334 solutions (0,67 %) compatibles avec U=4000±500 W/m²K et Tes=40±3 °C. La solution la plus proche de la cible correspond à Bs=162 m³/h, Tes=40,1 °C et ΔP=0,399 bar, pour U=3999 W/m²K. Ces résultats montrent l’intérêt de l’approche que nous avons proposée pour la prédiction du coefficient global de transfert thermique U, l’identification des régimes de fonctionnement et la recherche de zones opératoire s cibles, sous réserve d’une validation expérimentale avant son utilisation pour.

Bobur Gayratov, Bekhzod Gayratov

Copper smelter slag represents a significant secondary resource of critical metals, while flotation tailings serve as an abundant sulfur-bearing waste stream. This study investigated a waste-on-waste sulfation roasting approach for the selective recovery of Cu, Ni, and Co from fayalite copper smelter slag using flotation tailings as an in situ sulfur source and sodium metabisulfite (SMBS, Na2S2O5) as a sulfation promoter. The effects of roasting temperature, roasting time, slag-to-tailings ratio, SMBS dosage, and water-leaching conditions were systematically evaluated. Under the optimum conditions of a slag-to-tailings ratio of 1:1, roasting at 600 ◦C for 4 h with 30 wt% SMBS addition, followed by water leaching at 25 ◦C for 2 h, extraction efficiencies of 85.5% Cu, 81.6% Ni, and 87.1% Co were achieved, while Fe dissolution remained below 5%, demonstrating high selectivity. Phase and microstructural analyses by XRD, FTIR, SEM, and TG–DTA revealed that pyrite oxidation generated sulfur oxides required for metal sulfation, whereas SMBS promoted sulfur release and sulfate stabilization, enhancing sulfation efficiency. Thermodynamic analysis further confirmed the feasibility of sulfide oxidation and sulfate formation within the investigated temperature range. The results demonstrate that the synergistic use of tailings and SMBS enables efficient low-temperature sulfation.

Regita Bendikiene, Antanas Ciuplys

The influence of the austempering temperatures on the microstructure and mechanical properties of austempered ductile cast iron (ADI) was investigated. ADI is nodular graphite cast iron, which owing to higher strength and elongation, exceeds mechanical properties of conventional spheroidal graphite cast iron. Such a combination of properties is achieved by the heat treatment through austenitization, followed by austempering at different temperatures.

Kun Wang, Feng Hu

The tensile properties and work-hardening behavior of austempered bainitic steels below martensite start temperature (Ms) were investigated and compared with those of bainitic steel austempered above Ms. The results show that the tensile strength and yield strength increased from 1096 MPa and 734 MPa to 1203 MPa and 951 MPa, respectively, when the austempering temperature was decreased from 400 ◦C to 300 ◦C. However, the total elongation decreased from 23% to 16%. The martensite-retained austenite blocks and bainitic ferrite laths are significantly refined. With a decrease in the austempering temperature, the volume fraction of retained austenite decreased from 15.4 vol% to 6.2 vol%. The carbon content in retained austenite increased from 1.12 wt% to 1.69 wt%. All tensile specimens exhibited three stages of deformation in the differential Crussard−Jaoul (C−J) models. The difference in ductility is mainly attributed to the transformation of the retained austenite blocks into strain-induced martensite during deformation.

Wei Jiang, Dong Wu

Martensitic stainless steels (MSSs) have been widely used in the manufacture of turbine blades, surgical instruments, and cutting tools because of their hardness and corrosion resistance. The MSSs are usually tempered at a temperature no higher than 250 ◦C after quenching to avoid the decline in the hardness, strength, and corrosion resistance of the steels. However, some short-time thermal shocks are inevitable in processes like welding, water grinding, laser marking, etc., in the manufacturing of kitchen knives, all of which may have negative effects on the mechanical properties and corrosion resistance. The effects of these short-time thermal shocks have rarely been studied. In this paper, the martensitic stainless steel 5Cr15MoV (X50CrMoV15 is European Standards) was selected to be tempered at the sensitization temperatures (480 to 600 ◦C) for a series of times (0.5 to 128 min) after quenching, and the microstructures, hardness, and corrosion resistance of the steel after tempering were investigated. It was shown that the variation in hardness and corrosion resistance of the 5Cr15MoV steel could be divided into four stages over time during tempering at the sensitization temperatures. The hardness of steel was found to increase at first and then decrease with time; accordingly, good corrosion resistance was retained in the initial few minutes.

Adam Grajcar, Mateusz Morawiec

This paper presents the results of martensite tempering resistance in 4% Mn steel. The material was quenched and tempered at 350 ◦C for 15, 30, and 60 min. The analysis of the quenching and tempering was carried out using dilatometric and microstructural approaches. The phase composition was assessed using X-ray diffraction. The M s temperature and tempering progress were simulated using JMatPro software. The dilatometric analysis revealed a small decrease in the relative change in length (RCL) during tempering. This decrease was connected to the precipitation kinetics of cementite within the martensite laths. The microstructure investigation using a scanning electron microscope showed a very small amount of carbides, even for the longest tempering time. This showed the high tempering resistance of the martensite in medium-Mn steels. The hardness results showed an insignificant decrease in the hardness depending on the tempering time, which confirmed the high tempering resistance of martensite.

Muhammad Mohsin, Stefano Rovetta

The rapid advancement of technology has led to a substantial increase in Waste Electrical and Electronic Equipment (WEEE), which poses significant environmental threats and increases pressure on the planet’s limited natural resources. In response, Artificial Intelligence (AI) has emerged as a key enabler of the Circular Economy (CE), particularly in improving the speed and precision of waste sorting through machine learning and computer vision techniques. Despite this progress, to our knowledge, no comprehensive, systematic review has focused specifically on the role of AI in disassembling and recycling Waste-Printed Circuit Boards (WPCBs). This paper addresses this gap by systematically reviewing recent advancements in AI-driven disassembly and sorting approaches with a focus on machine learning and vision-based methodologies. The review is structured around three areas: (1) the availability and use of datasets for AI-based WPCB recycling; (2) state-of-the-art techniques for selective disassembly and component recognition to enable fast WPCB recycling; and (3) key challenges and possible solutions aimed at enhancing the recovery of critical raw materials (CRMs) from WPCBs.

Md Kaviul Islam, Anirudha Karati

The printed circuit board (PCB), a central component of most electronic devices, represents a significant fraction of the electronic product waste stream. The complex composition of PCBs, consisting of metals, polymers, and fiberglass, requires specialized recovery steps to reclaim valuable and critical materials and the safe disposal of brominated compounds. In this review paper, we describe the current state of critical material recovery and traditional recycling technologies and identify key obstacles to large-scale implementation. Metals present at high concentrations, such as copper, lead, and iron, are conventionally recovered from PCBs using hydrometallurgical, pyrometallurgical, or electrometallurgical processes. Hydrometallurgical methods achieve high selectivity through chemical leaching but pose significant challenges for effluent and reagent recovery. Pyrometallurgical methods facilitate rapid metal separation through smelting but require substantial energy and may release harmful gases. Electrometallurgical techniques produce high-purity metals but are constrained by pretreatment requirements and the consumption of energy. The non-metallic fraction of PCB waste is recycled using thermochemical conversion, microwave-aided heating, and direct recycling of epoxy–fiberglass composites, enabling material or energy recovery. The recovered polymer from direct recycling may have reduced mechanical strength and poor compatibility with new polymer matrices, and the resulting products from the thermal conversion suffer from incomplete conversion, degradation of quality, and residual contamination, as compared to synthetic polymers. Recent process developments have focused on extracting rare earth and supply-critical materials present at lower concentrations.

Muhammad R. R. Fatih, Hou-Jen Chen

Martensitic stainless steel (MSS) is widely used in several parts of automobiles where high strength, hardness, and corrosion resistance are required. However, the metastability of retained austenite can transform into martensite under severe deformation, adversely affecting material properties. Cryogenic treatments (CTs) have been extensively employed in iron-based alloys for fastener application due to their advantageous effect. This study explores the heat treatment processes applied to 13Cr-2Ni-2Mo martensitic stainless steel (MSS), including austenitizing, cryogenic treatment, and tempering cycles. Cryogenic treatment at (−150 ◦C) for varying durations, followed by tempering at 200 ◦C for 2 h, and the impact of post-cryogenic tempering at 200 ◦C for different tempering duration on the microstructure and mechanical properties were evaluated. Experimental results indicate that the sample quenched at 1040 ◦C for 2 h (CHT) contains lath martensite, retained austenite, δ-ferrite, and undissolved carbide precipitation. Compared to as-quenched samples, hardness decreased by 5.04%, 7.24%, and 7.32% after tempering for 2 h, 5 h, and 10 h, respectively. Extending cryogenic durations to 2 h, 12 h, and 20 h promoted nucleation of a mixture of M3C and M23C6 small globular carbides (SGCs) and grain refinement but resulted in hardness reductions.

Hao Chen, Linlin Zhao

With the background of emission peaks and carbon neutrality, light weight has become an irreversible trend in the development of the automobile industry. It is an inevitable choice to use a large amount of ultra-high-strength steels to realize light weight and safety of automobiles. Ultra-high-strength martensitic steels can be divided into hot-formed steels and cold-formed steels according to the forming process. In recent years, ultra-high-strength martensitic steels have been rapidly developed in automotive battery pack frameworks, door guard beams, bumpers, A-pillars, etc., depending on their good plasticity and advanced forming technology. In this paper, the recent progress of ultra-high-strength martensitic steels for automobiles is systematically reviewed, the mechanisms of alloying, strengthening, and toughening are emphatically expounded, and the hydrogen embrittlement problems in application are summarized. Finally, the prospects of manufacture and application of ultra-high-strength martensitic steels for automobiles in the future are forecasted.

Koh-ichi Sugimoto

This article introduces the microstructural and mechanical properties of low and medium-carbon advanced martensitic steels (AMSs) subjected to heat-treatment, hot- and warm-working, and/or case-hardening processes. The AMSs developed for sheet and wire rod products have a tensile strength higher than 1.5 GPa, good cold-formability, superior toughness and fatigue strength, and delayed fracture strength due to a mixture of martensite and retained austenite, compared with the conventional martensitic steels. In addition, the hot- and warm-stamping and forging contribute to enhance the mechanical properties of the AMSs due to grain refining and the improvement of retained austenite characteristics. The case-hardening process (fine particle peening and vacuum carburization) is effective to further increase the fatigue strength.

Shidan Yuan, Ye Ma

Color metallographic samples of H59 brass alloy have been prepared by aqua regia etching. In this paper, combined with XRD (X-ray diffraction), traditional metallographic analysis, FE-SEM (field emission scanning electron microscopy), and EBSD (electron backscattering diffraction), the effect of the color metallographic method on the microstructure characterization of the H59 brass alloy was analyzed. The experimental results showed that α phases and β phases could be distinguished clearly, and the phase morphology, distribution, and content could be expressed accurately with an average error value of 5.25% for the α phase and 4.71% for the β phase. The average error rate of the phase content characterization was 4.98% (less than 5%) with the color metallographic method. In addition, it was also found in the study that the brightness and darkness of the β phase would be related to the grain orientation, and the bright grains would correspond to the low-index surface, and the dark grains to the high-index surface. As a low-cost, fast, and efficient characterization technique, the experimental results show that color metallography (CM) could replace electron backscattering diffraction (EBSD) for the analysis of the phase composition, phase distribution, phase content, and grain orientation of brass alloys, which would provide an experimental basis for optimizing alloy properties and expanding applications.

Xabier Sarrionandia, Javier Nieves

Metallographic analyses of nodular iron casting methods are based on visual comparisons according to measuring standards. Specifically, the microstructure is analyzed in a subjective manner by comparing the extracted image from the microscope to pre-defined image templates. The achieved classifications can be confused, due to the fact that the features extracted by a human being could be interpreted differently depending on many variables, such as the conditions of the observer. In particular, this kind of problem represents an uncertainty when classifying metallic properties, which can influence the integrity of castings that play critical roles in safety devices or structures. Although there are existing solutions working with extracted images and applying some computer vision techniques to manage the measurements of the microstructure, those results are not too accurate. In fact, they are not able to characterize all specific features of the image and, they cannot be adapted to several characterization methods depending on the specific regulation or customer. Hence, in order to solve this problem, we propose a framework to improve and automatize the evaluations by combining classical machine vision techniques for feature extraction and deep learning technologies, to objectively.

Rana Ahmed, Stefan Steinlechner

In this paper, an investigation of the selective chlorination of targeted elements from goethite residues is performed. Goethite is an iron precipitated residue which results from the zinc industry, it contains many valuable elements as well as heavy elements. The recycling of these elements is economically and environmentally beneficial. The aims of this investigation are to recover the targeted valuable elements from the goethite, and to explain the fundamentals of the chlorination process. The effects of using different chlorination agents, such as aluminium chloride hexahydrate and magnesium chloride hexahydrate, as well as the influences of using various stoichiometric amounts of these agents, are studied with regard to how effectively the targeted elements are extracted. It was found that the targeted elements can be extracted more effectively using magnesium chloride hexahydrate.

Teodor Machedon-Pisu, Mihai Machedon-Pisu

In many areas such as the automotive, aircraft, and building industries, the high-strength aluminum alloy Al 7075 is frequently used due to its appropriate properties as a lightweight structural material. However, due to modest weldability, it is challenging to obtain high-quality welds with suitable mechanical properties, as cracks are generated while welding. Moreover, in order to avoid post-welding heat treatments and the use of complex welding equipment, in this paper the Al 7075 alloy is welded with MIG under longitudinal vibrations by using the Al 4043 alloy as filler material. As a consequence of strengthening the HAZ through precipitation, the mechanical and structural properties of the welded joints can be improved. These are investigated both under longitudinal forced vibrations at 50 Hz and without such vibrations. The results reveal improvements in terms of reducing the risk of hot cracking, obtaining a band structure free of porosity of the welds, improving the hardness of the welds under vibrations by 8.7% to 12.5%, and improving the tensile strength of the plates welded under vibrations by 12 to 15.5% in comparison to no vibrations. In relation to other welding procedures, the proposed procedure is more cost-effective and the weld quality is improved during the welding process.

Yu Lu, Dafeng Wang

Laser-MIG hybrid welding and MIG welding were carried out on 7B52 aluminum alloy, and the microstructure and mechanical properties of the joints were compared and analyzed. The results show that the average grain sizes of laser-MIG hybrid welding, MIG welding, and the laser weld zone are 18.38 µm, 24.16 µm, and 15.96 µm, respectively. The width of the HAZ of the laser zone is lower than that of the laser-MIG hybrid welding zone and MIG welding zone. The hardness is higher than that of the hybrid welding zone and MIG welding zone. The tensile strength of each laser-MIG hybrid welding joint zone is better than that of the MIG welding zone. The tensile strength of the laser zone is the worst. When stress ratio R = 0.1 and fatigue cycle Nf = 106, the fatigue strength of the laminated zone of the laser-MIG hybrid welding joint is better than that of the MIG welding joint, and the welding defect is the leading cause of fatigue cracks.

Kamel Touileb, Sahbi Boubaker

Tungsten Inert Gas (TIG) welding is a widespread welding process used in the industry for high-quality joints. However, this welding process suffers from lower productivity. Activated Tungsten Inert Gas (ATIG) is a variant of the TIG that aims to increase the depth penetration capability of conventional TIG welding. This is achieved by applying a thin coating of activating flux material onto the workpiece surface before welding. This work investigates the effect of the thermophysical properties of individual metallic oxide fluxes on 316L stainless steel weld morphology. Four levels of current intensity (120, 150, 180, 200 A) are considered. The weld speed up to 15 cm/min and arc length of 2 mm are maintained constant. Thirteen oxides were tested under various levels of current intensity in addition to multiple thermophysical properties combinations, and the depth penetration (D) and the aspect ratio (R) were recorded. This process has provided 52 combinations (13 oxides * 4 currents). Based on the numerical observations, linear and nonlinear models for describing the effect of the thermophysical parameters on the weld characteristics were tuned using a particle swarm optimization algorithm. While the linear model provided good prediction accuracy, the nonlinear exponential model outperformed the linear one for efficiency based on algorithmization of the planning process.

Wanghui Xu, Xiaoyu Cai

To enhance the performance of Ti6Al4V titanium alloy joints, ultrasonic frequency pulsed TIG welding was employed. The microstructure and mechanical properties of the joints were systematically investigated. Results show that the weld microstructure is predominantly composed of acicular α phase, lath α phase, and a minor amount of β phase. Compared with conventional TIG welding, the application of ultrasonic frequency pulse current effectively refined the grains, achieving an average grain size of 0.54 µm. Concurrently, the proportion of high-angle grain boundaries increased from 96.1% to 97.6%. The average hardness of the fusion zone exceeded that of the base metal and was significantly increased by the ultrasonic frequency pulse current, reaching 350 HV compared to 330 HV for conventional welds. Furthermore, the ultrasonic frequency pulsed TIG joints exhibited higher yield strength and elongation than their conventional welds. These findings demonstrate that introducing ultrasonic frequency current during TIG welding effectively improves the properties of Ti6Al4V welded joints.

Anatoliy Ranskiy, Olga Gordienko

Currently, less attention is paid to zinc–carbon batteries, although they are still widely used and are among the major types of batteries collected and recycled. The recycling technologies currently in use do not allow the complete recovery of resources, are not self-sufficient and require additional financing. Therefore, this paper aims to study the possibility of complete recycling of waste zinc–carbon batteries and to suggest the practical use of the final products generated in the recycling process. The possibility of complex processing of spent zinc–carbon batteries using mechanical separation and processing of the battery’s components (steel case, zinc electrode, graphite electrode, polypropylene and paper insulators) is justified. The separation of spent electrolytes from other components of batteries with hydrochloric acid was studied. It was shown that the extraction of Zn2+ and NH4+ cations takes place following the addition of an equivalent amount of Na3PO4 solution and water-insoluble NH4ZnPO4 salt sedimentation. Waste agglomerate (mixture of MnO2, MnO(OH), and graphite) was regenerated to its initial composition (MnO2, graphite) at a temperature of 300–325 ◦C; manganese (III) hydroxide was oxidized to manganese (IV) dioxide. Thermal destruction of polypropylene and paper insulators with additional introduction of polyethylene into the primary mixture produced pyrolysis liquid, pyrocarbon and pyrolysis gas as products. The practical use of the products.

Linye Li, Yuzhang Li

The recycling of used lithium-ion batteries has become a growing concern. As a large number of rare metal elements are present in waste lithium-ion batteries, recycling them can significantly improve resource utilization and reduce the material cost of battery production. The process of recycling used lithium-ion batteries involves three main technology parts: pretreatment, material recovery, and cathode material recycling. Pretreatment includes discharge treatment, uniform crushing, and removing impurities. Material-recovery technology mainly involves traditional pyrometallurgical and hydrometallurgical technologies, as well as the developing biometallurgy technology. Analysis of existing data shows that pretreatment technology is crucial for the recycling of used lithium-ion batteries. Hydrometallurgical technology and pyro-hydrometallurgical technology are expected to be the most suitable industrialization technology paths in the future, with biometallurgical technology and direct recycling technology providing a low-pollution development direction. This article summarizes the different pretreatment techniques and valuable metal-recovery pathways. The advantages and disadvantages of each method were evaluated. The economic costs, environmental benefits, and degree of industrialization of each method were assessed. The possible development directions of various methods are summarized to provide reference for future research.

Daniele Marchese, Chiara Giosuè

Lithium-ion batteries (LIBs) can play a crucial role in the decarbonization process that is being tackled worldwide; millions of electric vehicles are already provided with or are directly powered by LIBs, and a large number of them will flood the markets within the next 8–10 years. Proper disposal strategies are required, and sustainable and environmental impacts need to be addressed. This paper provides a comprehensive overview of the various sustainable recycling processes used for LIBs, highlighting the technological advancements and methodologies employed in the recovery of valuable materials. Through an in-depth literature review, we examine existing recycling techniques, their efficiency, and potential environmental benefits. The results indicate that while multiple methods are available, the optimization of processes for increased recovery rates and decreased ecological footprints is essential for the future of battery recycling. The study emphasizes the importance of developing more effective recycling technologies that can handle the forthcoming surge in used LIBs, thereby contributing to a circular economy. By synthesizing current knowledge and identifying gaps in research, this work aims to inform future innovations and policy directions in the field of battery recycling.

Alessandra Zanoletti, Eleonora Carena

Lithium-ion batteries (LIBs) are a widely used energy storage technology as they possess high energy density and are characterized by the reversible intercalation/deintercalation of Li ions between electrodes. The rapid development of LIBs has led to increased production efficiency and lower costs for manufacturers, resulting in a growing demand for batteries and their application across various industries, particularly in different types of vehicles. In order to meet the demand for LIBs while minimizing climate-impacting emissions, the reuse, recycling, and repurposing of LIBs is a critical step toward achieving a sustainable battery economy. This paper provides a comprehensive review of lithium-ion battery recycling, covering topics such as current recycling technologies, technological advancements, policy gaps, design strategies, funding for pilot projects, and a comprehensive strategy for battery recycling. Additionally, this paper emphasizes the challenges associated with developing LIB recycling and the opportunities arising from these challenges, such as the potential for innovation and the creation of a more sustainable and circular economy. The environmental implications of LIB recycling are also explored.

Qi Zhou, Jian Pan

Jarosite residue (JR), a hazardous solid waste generated in non-ferrous metallurgy, poses significant environmental challenges due to its large volume and poor storage stability. However, its high content of valuable metals (such as iron, zinc, gallium, indium, silver) makes its efficient recovery and comprehensive utilization highly significant. This study investigates the “oxidative roasting–reductive smelting” process for JR treatment. The reduction thermodynamics of JR-R (roasted JR) were analyzed, and the effects of smelting temperature, time, and slag basicity on the reduction and smelting process were examined. The results indicate that increasing slag basicity and temperature generally decreases slag viscosity. Thermodynamic calculations demonstrate that reductive smelting effectively enriches valuable metals (>1039 ◦C). The optimal conditions for reductive smelting of JR were determined to be as follows: smelting temperature of 1550◦C, smelting time of 60 min, and slag basicity of 0.9. Under these conditions, the process achieved an Fe grade of 92.87% in pig iron with a recovery rate of 90.66%, a Ga grade of 377 g/t with a recovery rate of 94.91%, and Zn and In volatilization rates.

Ali Asimi, Khodakaram Gharibi

Jarosite precipitation process (JPP) is the most frequently used procedure for iron removal in the hydrometallurgical zinc extraction process. However, there is a gap in the knowledge of the relationship between operational parameters and the low contaminant JPP on the industrial scale. This study will address these issues by investigating the behavior of zinc calcine (ZC) as a neutralizing agent, exploring the source of zinc and iron through leaching experiments, and simulating the Jarosite process of the Bafgh Zinc Smelting Company (BZSC). The results showed that the zinc dissolution efficiency was 90.3% at 90 ◦C, and 73% of the iron present in the calcine can be solubilized. The main outcome was the iron removal of about 85% by alkaline ions present in ZC without the addition of any precipitating agent. The second target was to evaluate the effect of operational parameters on jarosite precipitation. Results revealed that increasing the temperature to 90 ◦C and the stirring rate to 500 RPM as well as adjusting the ZC’s pH during the jarosite precipitation remarkably improved iron removal. Considering all these factors in the plant could improve Fe precipitation to around 80% on average.

Katarzyna Klejnowska, Mateusz Sydow

The utilization of end-of-life batteries (including Zn-C and alkaline batteries) is one of the areas that need to be perfected in order to provide environmental and human safety as well as to contribute to closing the material loop, as described in the EU Green Deal. The presented study shows the environmental impacts of the two selected pyrometallurgical technologies (processing of the black mass from waste Zn-C and alkaline batteries as an additive to an existing process of the recycling of steelmaking dust and treatment of the black mass as the primary waste material, both processes performed in a Waelz kiln). The presented LCA-based study of the recycling of end-of-life Zn-C and alkaline batteries focused on terrestrial ecotoxicity can be a useful tool in the process of the development of a circular economy in Europe, as it provides a multi-disciplinary overview of the most important environmental loads associated with the described recycling technologies. Therefore, the goal of the presented study was to compare the environmental performance (utilizing LCA) of two different metallurgical processes of black mass utilization.

Pavel Grudinsky, Anfisa Yurtaeva

The Waelz slag generated during electric arc furnace dust processing is an iron-rich product with significant amounts of iron, zinc and copper. About 600–800 kg of the Waelz slag is generated per ton of the dust processed. The Waelz slag samples from two different plants were thoroughly characterized using inductively coupled plasma optical emission spectroscopy (ICP-AES), X-ray diffraction analysis (XRD), chemical phase analysis, Mössbauer spectroscopy and other supporting methods. The phase distribution of iron, zinc and copper was determined in the Waelz slag samples. Low-intensity wet magnetic separation was tested for the iron recovery from the Waelz slag samples. It was found that the Waelz slag samples contain valuable metals, which can be recovered through the magnetic separation process, indicating a potential for resource recovery and recycling within metallurgical practices.

Jie Li, Jianxin He

Rotary kiln shell temperature monitoring is essential for metallic shell protection and refractory lining maintenance in high-temperature industrial processes, while smoke, dust, thermal diffusion and non-kiln heat sources make valid shell temperature extraction difficult. This study develops a multi-scale cascaded network with low-resolution space-to-depth downsampling (MSC-LSTD) for infrared kiln shell segmentation and temperature recognition. Global infrared thermal images and local laser temperature measurements are used to construct a calibrated rotary kiln infrared dataset, and predicted kiln shell masks are mapped to temperature matrices for valid shell temperature analysis. MSC-LSTD achieves 99.82% aAcc, 99.14% mAcc and 97.03% mIoU on the rotary kiln infrared dataset, showing robust segmentation performance under complex thermal interference. The proposed framework provides a practical image-based solution for kiln shell overheating warning and refractory lining degradation assessment.

Markus Vogelbacher, Sina Keller

The recycling of zinc in the Waelz process is an important part of the efficient use of resources in the steel processing cycle. The pyro-metallurgical processing of zinc-containing wastes takes place in a Waelz rotary kiln. Various measured variables are available to monitor the process. The temperature of the kiln-shell is analyzed by an infrared kiln-shell-scanner. In this paper, methods are presented which eliminate external weather-related disturbances on the temperature measured by the kiln-shell-scanner using a weather model and which extend the monitoring of the regularly necessary melting process to remove accretions. For this purpose, an adapted sigmoid estimation is introduced for the melting process, which provides new information about the current process status and a forecast of the further development of the melting process. As an assistance system for the plant operator, this enables an efficient execution of the melting process.

Patricia M. C. Faria, Raj K. Rajamani

Important advances have been made in the last 60 years or so in the modeling of ball mills using mathematical formulas and models. One approach that has gained popularity is the population balance model, in particular, when coupled to the specific breakage rate function. The paper demonstrates the application of this methodology to optimize solids concentration in ball milling of an iron ore from Brazil. The wet grinding experiments were conducted in bench (0.25 m diameter) and pilot-scale mills (0.42 m diameter), and surveys in a full-scale industrial (5.2 m diameter) mill. It is first demonstrated that the successful application of the model required recognizing the non-normalizable nature of the breakage function of the particular ore. It is then demonstrated how the model can be used to predict results of pilot-scale grinding tests under different conditions (overflow/grate discharge) based on data from batch grinding tests. Finally, the model is used to predict the effect of changing solids concentration inside the industrial mill, with good correspondence between the pilot plant and full-scale results, which demonstrated the benefit of reducing solids concentration to values between 76 and 80% in weight for the ore of interest from the 83% that was originally used in the operation.

Zixin Yin, Daoming Ma

The liner is a wear-prone component in ball mills, subject to continuous impacts, squeezing, and abrasion from the grinding media during operation. Its service performance directly affects the working efficiency of the ball mill. The service life of mining ball mill liners is about 8 months, and frequent downtimes occur due to liner wear and loss of effectiveness, with liner replacement accounting for about 6% of the total cost, resulting in huge economic losses. This paper focuses on a Φ305 mm × 150 mm experimental ball mill, using the discrete element software Rocky Discrete Element Method (DEM) for simulation modeling analysis. With Φ10 mm and Φ20 mm mono-size particle simulations serving as reference groups, this study investigates the motion states and liner abrasion patterns under different liner heights for both sizes of grinding media in Equilibrium Quality Manufacturer (EQM) and Original Equipment Manufacturer (OEM) gradations. The results indicate that the impact of liner height on the wear of the ball mill liners is related to the size and gradation of the grinding media. The degree of liner wear from highest to lowest is as follows: EQM > Φ20 mm > OEM > Φ10 mm. Due to the effect of the cylinder end cap, the wear at the axial center of the ball mill liner is more severe than at both ends.

Manuel Saldaña, Edelmira Gálvez

Considering the continuous increase in production costs and resource optimization, more than a strategic objective has become imperative in the copper mining industry. In the search to improve the efficiency in the use of resources, the present work develops models of a semi-autogenous grinding (SAG) mill using statistical analysis and machine learning (ML) techniques (regression, decision trees, and artificial neural networks). The hypotheses studied aim to improve the process’s productive indicators, such as production and energy consumption. The simulation of the digital model captures an increase in production of 4.42% as a function of mineral fragmentation, while there is potential to increase production by decreasing the mill rotational speed, which has a decrease in energy consumption of 7.62% for all linear age configurations. Considering the performance of machine learning in the adjustment of complex models such as SAG mills, the findings demonstrate significant improvements in the operational efficiency of copper mining processes.

Daniel Dobslaw, Oliver Ortlinghaus

International contracts to restrict emissions of climate-relevant gases, and thus global warming, also require a critical reconsideration of technologies for treating municipal, commercial, industrial, and agricultural waste gas emissions. A change from energy- and resource-intensive technologies, such as thermal post-combustion and adsorption, as well to low-emission technologies with high energy and resource efficiency, becomes mandatory. Biological processes already meet these requirements, but show restrictions in case of treatment of complex volatile organic compound (VOC) mixtures and space demand. Innovative approaches combining advanced oxidation and biofiltration processes seem to be a solution. In this review, biological processes, both as stand-alone technology and in combination with advanced oxidation processes, were critically evaluated in regard to technical, economical, and climate policy aspects, as well as present limitations and corresponding solutions to overcome these restrictions.

Haouari Khadra, Rahmani Kouider

Industrial applications need to use different systems for the problem of gas cleaning. A lot of processes have been developed, such as the use of a venturi for gas cleaning and pollution reduction. Additionally, several studies have been developed especially in terms of pressure drop because it is one of the main parameters to determine its efficiency. While the phenomenon of mass transfer in a venturi scrubber has not found much attention, in the present study, a mass transfer two-dimensional simulation is developed for gasification gas cleaning through a venturi scrubber with boundary conditions represented in air inlet velocities of 10, 15, and 20 m/s and water inlet mass flow of 0.02, 0.04 and 0.06 kg/s. In this work, Navier–Stokes equations are solved numerically and the mass transfer technique is treated by the volume of fluid (VOF) model, using CFD software. The obtained results were analyzed.

Linfeng Liang, Yuer Lan

During industrial production, a significant amount of oil mist is generated, posing health risks because it is a fine particulate matter that is easily inhaled by the human body. Electrostatic collection has been widely applied in machining workshops as an effective method for capturing oil mist. While existing research has made substantial progress in improving the collection efficiency of electrostatic methods, the challenge of achieving high-efficiency oil mist collection remains unresolved. The inherent physical properties of oil mist contribute to difficulties in its efficient collection. Additionally, the deposition characteristics of oil mist, as well as the structure and operational parameters of the electrostatic precipitator (ESP), directly affect collection efficiency. This paper reviews the literature from the past decade, introduces the mechanisms of oil mist generation, and presents oil mist monitoring technologies. Based on the deposition characteristics of oil mist, it explores high-efficiency collection strategies and suggests future directions for research.

Alireza Afshari, Lars Ekberg

Many people spend most of their time in an indoor environment. There is a positive relationship between indoor environmental quality and the health, wellbeing, and productivity of occupants in buildings. The indoor environment is affected by pollutants, such as gases and particles. Pollutants can be removed from the indoor environment in various ways. Air cleaning devices are commonly marketed as benefiting the removal of air pollutants and consequently, improving indoor air quality.

Edgar Sokolovskij, Artūras Kilikevičius

The removal of particulate matter (PM) from air streams is essential for advancing environmental technologies and safeguarding public health. This study explores the performance of an electrostatic precipitator (ESP) in eliminating fine and ultra-fine PM under varied experimental conditions. It uniquely examines the influence of PM size and feed rate on ESP removal efficiency. The system’s use of low voltages enhances energy sustainability, while its innovative design improves corona discharge, leading to significant reductions in fine and ultra-fine PM emissions. Plants using electrical devices are increasingly being incorporated into material processing lines to reduce pollution in the surrounding work area, as well as to collect particle emissions in the atmosphere. It is also possible to recycle some raw materials in this way with low energy consumption. This cleaning technology increases the added value.

Mohamed Badran, Abdallah Mahmoud Mansour

Utilizing electrostatic precipitators (ESPs) is an efficient particle removal method that sees a wide usage in industrial environments. This is mainly because of the low drop of the pressure flow, while retaining high collection efficiency, alongside being cost-effective. This paper reviewed previous works concerning optimizing the performance of single- and multi-stage ESPs by changing several design parameters and evaluating the effects on different performance indices, such as the corona power ratio, current-voltage characteristics, and overall collection efficiency. The review then goes through several modelling methodologies, showcasing their shortcomings and developments, as well as the relationship between the electrohydrodynamic (EHD) flow and the precipitation performance. The performance effects of using different electrode configurations and designs in terms of the number of electrodes, relative dimensions, spacings, channel lengths, and overall design were also reviewed.

Xiaomin Zhou, Liqi Li

In the production process of strip tandem cold rolling mills, the flatness control system is important for improving the flatness quality. The control efficiency of actuators is a pivotal factor affecting the flatness control accuracy. At present, data-driven methods to intelligently identify the flatness control efficiency have become a research hotspot. In this paper, a wavelet transform longitudinal denoising method, combined with a genetic algorithm (GA-WT), is proposed to handle the big noise of the measured data from each signal channel of the flatness meter, and Legendre orthogonal polynomial fitting is employed to extract the effective flatness features. Based on the preprocessed actual production data, the adaptive moment estimation (Adam) optimization algorithm is applied to intelligently identify the flatness control efficiency. This paper takes the actual production data of a 1420 mm tandem cold mill as an example to verify the performance of the new method. Compared with the control efficiency determined by the empirical method, the flatness residual MSE 0.035 is 5.4% lower. The test results indicate that the GA-WT-Legendre-Adam method can effectively reduce the noise, extract the flatness features, and achieve the intelligent determination of the flatness control efficiency.

Youzhao Sun, Jingdong Li

Focusing on the problem of strip shape quality control in the finishing process of hot rolling, a shape model based on metal flow and stress release with the application of varying contact rolling parameters is introduced. Combined with digital twin technology, the digital twin framework of the shape model is proposed, which realizes the deep integration between physical time–space and virtual time–space. With the utilization of the historical data, the parameters are optimized iteratively to complete the digital twin of the shape model. According to the schedule, the raw material information is taken as the input to obtain the simulation of the strip shape, which shows a variety of export shape conditions. The prediction absolute error of the crown and flatness are less than 5 µm and 5 I-unit, respectively. The results prove that the proposed shape simulation model with strong prediction performance can be effectively applied to hot rolling production. In addition, the proposed model provides operators with a reference for the parameter settings for actual production and promotes the intelligent application of a shape control strategy.

Yu-Chan Huang, Chao-Chung Peng

The looper-tension control is a crucial aspect of a hot strip finishing mill. It involves a highly nonlinear system with strong states coupling and uncertainty, and the performance directly impacts the thickness deviation, which is the most critical product index. From the system dynamics, it is known that tension is highly sensitive to the strip velocity variation, which is typically unmeasurable. Instead, it needs to be calculated through work roll speed and strip slip which contains uncertainties, negatively affecting tension control performance. First, a feedback linearization-based proportional–integral (PI) controller design approach is proposed for the hot rolling looper-tension system. Second, to reduce the impact of speed uncertainties and enhance thickness response, an adaptive PI controller is introduced. Validation was conducted by numerical simulations; the result indicates that an adaptive PI controller reduces the magnitude of thickness variation and shortens the duration of its impact, verifying the consistency between theoretical derivation. The proposed control method effectively addresses the impact of uncertainties encountered in real-world applications. Additionally, it simplifies control parameter adjustment in practical use, reduces testing time, and improves product quality.

Zhiwen Lu, Duolong Zhou

The impact of rolling mill vibration extends beyond product quality to equipment health, making vibration control crucial. This study addresses the issue of frequent abnormal vibration in hot strip finishing mills by employing a combination of theory, simulation, and experimentation to analyze the dynamic behavior of the mill and apply findings to on-site vibration suppression. Initially, a torsional-vertical-horizontal coupled dynamic model for the rolling mill has been developed, taking into account the rolling process. The accuracy of this model is established through both finite element simulations and actual experiments. Subsequently, the vibration characteristics of the rolling mill system are investigated under typical process parameters utilizing the established dynamic model. The results reveal that the vibration amplitude notably escalates with the increase of rolling reduction rate and rolling speed, and the difference in front and rear tension has little impact on the mill’s vibration. Furthermore, an increase in the temperature of the rolled piece reduces the overall vibration amplitude, and harder material results in greater overall mill vibration. Lastly, abnormal vibration in the F2 finishing mill at a hot rolling plant is effectively mitigated by reducing rolling structural gap and dynamic rolling force.

Bin Wang, Jianjun Gao

Chromium slag, a chromium-bearing solid waste characterized by substantial environmental hazards yet with appreciable resource potential, has become a focal topic in solid-waste pollution control and the circular economy. Centered on the overarching logic of 'evidence chain–system boundary–scalable and verifiable acceptance,' this review systematically synthesizes recovery technologies, industrial-scale utilization pathways, and the key challenges associated with the detoxification and resource utilization of chromium slag. From the perspective of recovery technologies, we examine pyrometallurgical and hydrometallurgical routes, solidification/stabilization (S/S), and bioelectrochemical coupling approaches, elucidating their fundamental principles, applicability boundaries, and critical nodes where environmental burdens may be transferred across media. We emphasize that process design should concurrently consider detoxification efficiency, resource recovery performance, and whole-process pollution control. Regarding utilization pathways, this review highlights three major routes with strong scale-up relevance—metallurgical process co-treatment (CAP–sintering–blast furnace), bulk utilization in construction materials, and high-value utilization—and analyzes their industrial potential and engineering constraints. Particular attention is given to the lack of long-term leaching and durability evidence, which represents a central bottleneck limit.

Jiarui Gu, Zinuo Tian

Steel slag (SS), a major industrial solid waste generated during steelmaking, has considerable cementitious potential and high hardness for use in low-carbon construction materials. However, its widespread utilization is limited by poor volume stability arising from the delayed hydration and expansion of free CaO (f-CaO) and free MgO (f-MgO). This review systematically examines the formation mechanisms of these expansive phases and evaluates four stabilization technologies, including surface modification, high-temperature modification, acid treatment, and carbonation, with respect to their reaction mechanisms, technical advantages, limitations, and engineering applicability. The performance of stabilized SS in cementitious matrices and as construction aggregates is also assessed, together with the corresponding application scenarios. Carbonation is a promising route because it can simultaneously reduce reactive expansive phases and mineralize CO2.

Marek Laciak, Ján Kaˇ cur

Scrap charge selection has a significant influence on the thermal balance of the basic oxygen furnace (BOF) process and consequently on the final melt temperature. This paper presents a hybrid deterministic, regression, and machine learning framework for endpoint temperature prediction and steel scrap charge optimization in BOF steelmaking. The proposed methodology combines an existing deterministic BOF simulation model with regression analysis, machine learning surrogate models, and constrained nonlinear optimization. The dataset was constructed from operational records of 180 industrial BOF heats. The masses of seven scrap categories and the target endpoint temperature were obtained from these operational records, whereas the endpoint temperature used as the output for training the machine learning surrogate models was generated by the existing deterministic BOF process model. Three machine learning approaches, namely Support Vector Regression (SVR), Random Forest Regression (RF), and Gaussian Process Regression (GPR), were implemented and evaluated for endpoint temperature prediction using the masses of seven scrap categories and the target endpoint temperature as model inputs. Among the investigated surrogate models, Gaussian Process Regression achieved the best approximation performance, with a test MAE of 10.47◦C, RMSE of 16.38 ◦C, and R2 = 0.870, and was subsequently used in the optimization framework. In addition, the deterministic BOF simulation model was incorporated into a model-based optimization procedure using the same optimization objective. Both approaches were formulated as constrained optimization problems minimizing the deviation between the predicted and target endpoint temperature.

Jiazhe An, Yuxin Tan

Accurate endpoint control in basic oxygen furnace (BOF) steelmaking is essential for reducing production costs and improving steel quality. To overcome the limited mechanism support and poor transparency of purely data-driven models, this study proposes a physics-aware and interpretable framework for cumulative decarburization prediction based on real industrial data. Historical multi-heat data from the same converter were integrated, and an averaged full-spectrum cross-correlation method was used to estimate and correct the transport delay of off-gas signals, thereby constructing a heat-wise large-sample dataset. Key elemental features with clear physical significance were then extracted from high-dimensional flame spectra by incorporating their underlying radiation mechanisms. On this basis, a Stacking-based ensemble model was developed for cumulative decarburization prediction, and SHAP was introduced to interpret the model decision logic. Results show that the proposed framework outperforms conventional single models and purely data-driven dimensionality reduction methods. SHAP analysis further indicates that model decisions are mainly dominated by four core elemental spectral features, namely Fe, C, O, and Mn. Overall, the proposed method combines predictive performance, physical constraints, and interpretability, and provides a new solution for auxiliary soft sensing and decision support in BOF endpoint control.

Yichao Hu, Yinxuan Qiu

Introducing CO2 electrochemical conversion technology to the iron-making blast furnace not only reduces CO2 emissions, but also produces H2 as a byproduct that can be used as an auxiliary reductant to further decrease carbon consumption and emissions. With adequate H2 supply to the blast furnace, the injection of H2 is limited because of the disadvantageous thermodynamic characteristics of the H2 reduction reaction in the blast furnace. This paper presents thermodynamic analysis of H2 behaviour at different stages with the thermal requirement consideration of an iron-making blast furnace. The effect of injecting CO2 lean top gas and CO2 conversion products H2–CO gas through the raceway and/or shaft tuyeres are investigated under different operating conditions. H2 utilisation efficiency is analyzed alongside the overall performance, providing insights into optimizing the process for enhanced sustainability in iron production.

Alfredo Alan Flores Saldívar, Rodrigo Juárez Martínez

The design of an aluminium melting furnace has faced two challenges: mathematical modelling and simulative optimization. This paper first uses fluid dynamics to model the aluminium process mathematically. Then, the model is utilized to simulate a round shaped reverberatory furnace for melting aluminium alloys. In order to achieve the highest thermal efficiency of the furnace, modelling and simulation are performed to predict complex flow patterns, geometries, temperature profiles of the mixture-gas air through the main chamber, as well as the melting tower attached to the furnace. The results led to the establishment of optimal position an.

Shereen Abouelazayem, Ivan Glavinić

The flow structure in the mold of a continuous steel caster has a significant impact on the quality of the final product. Conventional sensors used in industry are limited to measuring single variables such as the mold level, providing very indirect information about the flow structure. This paper presents a solution by applying non-invasive sensors, specifically ultrasound Doppler velocimetry (UDV), to visualize the flow structure in the opaque liquid metal, allowing for a better understanding of the mold dynamics. The study details the preprocessing of UDV data and the feature extraction techniques employed. The extracted flow features serve as the foundation for real-time feedback control using model predictive control (MPC) techniques. The results demonstrate the effectiveness of the controller in achieving optimum flow structures within the mold, utilizing two main actuators: the electromagnetic brake and the stopper rod. Experimental results were obtained from a laboratory model of a continuous caster located at the Helmholtz-Zentrum Dresden Rossendorf (HZDR), showcasing the viability of this approach to enhance process control in steel production.

Jian Yang, Zhenping Ji

A digital-twin-model-based optimal control system is presented for the steel continuous casting process. The system is designed for the coordinated optimization and dynamic control of secondary cooling and final electromagnetic stirring (FEMS), and involves three related parts. Firstly, a three-dimensional real-time heat transfer model is established as the digital twin of the heat transfer process of continuous casting; for high accuracy, it is calibrated offline and calibrated online using measurements of the surface temperatures and shell thicknesses (only offline). Secondly, according to metallurgical rules, cooling and stirring are optimized coordinatively, based on the established digital-twin model and chaos particle swarm optimization algorithm. Thirdly, cooling and stirring are further dynamically controlled for quality stability. Finally, the system is applied in a bloom caster with model errors ≤±10 ◦C and control errors ≤±4 ◦C, which reduces the macro-segregation over grade 1.5 from 11% to 3.3%.

Silvia Cecchel, Giovanna Cornacchia

The automotive industry is undergoing a rapid evolution to meet today’s challenges; therefore, continuous innovation and product development are needed. Validation tests on prototypes play a crucial role in moving new components into industrial production. There is also a pressing need for faster prototyping processes. In this context, rapid sand casting (RSC), based on additive manufacturing technology, offers a promising solution for a quick production of sand molds. While this technology is already employed in the industry, the need to deepen the general understanding of its impact on the casting properties is still a relevant item. In this study, different geometries of automotive prototypes made of aluminum EN AC 42100-T6 alloy were experimentally analyzed. Microstructural examinations, tensile tests, and fractography and porosity analyses were conducted. The findings demonstrate the considerable potential of RSC, giving, in general, high mechanical properties. A comparative analysis with prototypes produced through traditional sand casting revealed similar results, with RSC exhibiting superior yield strength and stress at brake. However, both technologies revealed a reduced elongation percentage, as expected. Future efforts will focus on standardizing the RSC process to enhance ductility levels.

Mateusz Czepiel, Magdalena Ba ńkosz

Injection molding is a method commonly used to manufacture plastic products. This technology makes it possible to obtain products of specially designed shape and size. In addition, the developed mold allows for repeated and repeatable production of selected plastic parts. Over the years, this technology grew in importance, and nowadays, products produced by injection molding are used in almost every field of industry. This paper is a review and provides information on recent research reports in the field of modern injection molding techniques. Selected plastics most commonly processed by this technique are discussed. Next, the chosen types of this technique are presented, along with a discussion of the parameters that affect performance and process flow. Depending on the proposed method, the influence of various factors on the quality and yield of the obtained products was analyzed. Nowadays, the link between these two properties is extremely important. The work presented in the article refers to research aimed at modifying injection molding methods enabling high product quality with high productivity at the same time. An important role is also played by lowering production costs and reducing the negative impact on the environment. The review discusses modern injection molding technologies, the development of which is constantly progressing. Finally, the impact of the technology on the ecological environment is discussed and the perspectives of the process were presented.

Zhenwei Xie, Liexing Zhou

Enhancing the strength and toughness of aluminum alloys using microstructure optimization remains a key challenge. In this study, an AA2024 aluminum alloy with a double-layer multi-gradient structure was fabricated using 50% constrained deformation and single-stage peak aging at 150 ◦C. Microstructural and compositional analysis was performed using SEM, XRD, and TEM to investigate grain structures, dislocation density, and the distribution of precipitated phases. The results revealed a heterogeneous microstructure with variations in grain size, dislocation gradient, and precipitation phases between the constrained and deformation layers. Mechanical testing demonstrated a 30.9% increase in yield strength, a 16.4% increase in tensile strength, and a 13.9% improvement in uniform elongation compared to the T6 temper. Corrosion tests showed enhanced resistance, with a shallower intergranular corrosion depth and higher self-corrosion potential. The improved.

Qilun Li, Xiaobo Zhang

Hot extrusion forming is one of the best cost-effective processing methods to obtain high-strength aluminum alloys. In order to obtain high performance 2024 aluminum alloy for the aero and automobile industries, this research comprehensively uses heat treatment and reverse isothermal extrusion technology to prepare 2024 alloy. The effects of homogenization, extrusion and post-extrusion annealing treatment on the microstructure and mechanical properties of 2024 aluminum alloy were discussed in detail. The results indicate that the grain refinement of the extruded alloy material is significant. The coarse eutectic microstructure at the grain boundaries was refined, and these grains tended to be uniformly distributed after the annealing treatment. Extruded 2024 aluminum alloy material mainly has S (Al2CuMg) and Al7Cu2Fe second phases. The appearance of a large number of S phases led to a significant improvement in the properties of the alloy with an increase in tensile strength and elongation of 176% and 547%, respectively. In addition, EBSD analysis showed a significant meritocratic growth in the extrusion direction with the appearance of Copper {112} <111> rolling weaving, which led to process hardening and the strength improvement of the alloy.

Carmen Mª Abreu, Iria Feijoo

The influence of annealing treatment on the microstructure and the corrosion behaviour of a complex bronze Al-Ni alloy was analysed. The microstructural characterization after thermic treatment shows that the retained β-phase disappears and the KII-phase undergoes a spheroidization process. Moreover, there is an augmentation of K-phase precipitates within the α-phase, particularly KIV and KV, which homogenizes the distribution of alloying elements between the phases. The corrosion behaviour was investigated by means of selective corrosion tests, potentiodynamic measurements, and electrochemical impedance spectroscopy. All of the experiments showed that thermic treatment greatly improves the corrosion resistance of the alloy. As such, annealing treatment influences a microstructure to be more dealloying resistant, which allows the development of a more protective air-formed passive film. On the other hand, the lower current registered after anodic peaks and Electrochemical Impedance Spectroscopy data seem to be correlated with a more protective layer formed on annealed material. As such, this protective character is due to a greater incorporation of Al3+, Ni2+ and Cu2+ in the passive film, as revealed by X-ray Photoelectron Spectroscopy results.

Zhiqiang Song, Ojiyed Tegus

Chloride ions play an important role in the corrosion of bronze through their active reactivity to copper alloys. The corrosion behavior of bronze alloys in NaCl solution was investigated by using X-ray diffraction (XRD), a scanning electron microscope (SEM), and electrochemical tests, with a special emphasis on the corrosion resistance of the α and δ phases in Cu-20 wt%Sn bronze alloys. The experimental results show that the corrosion current density of Cu-20 wt%Sn bronze alloys increases from 1.1 ×10−7 A/cm2 to 2.7 ×10−6 A/cm2 with the increase in the chloride ion concentration from 10−3 mol/L to 1 mol/L. After a soaking duration of 30 days, the matrix corrosion depth reaches 50 µm. The α phase of the alloys is easily corroded in NaCl solution, while the δ phase with high Sn content has strong corrosion resistance. This study provides relevant data for the analysis and protection of ancient bronze alloys.

Constantin Dulucheanu, Traian Lucian Severin

In recent years, to reduce car costs, research has been conducted on dual-phase steels with low manganese content (below 1.0%). This study investigated the influence of technological parameters of heat treatment (heating temperature and cooling medium) on such steels’ structures and mechanical properties. The ferrite-martensitic structures, specific for dual-phase steels, were obtained by intercritical quenching: heating of samples (made of alloys with 0.511% Mn, respectively 0.529% Mn) to temperatures located between critical points Ac1 and Ac3, followed by cooling in water without mechanical agitation and in water activated with ultrasounds at the frequency of 59 kHz. Through metallographic analyses and tensile tests, it was possible to determine the volume fraction of martensite, the ferrite microhardness, the ultimate tensile strength, the total elongation, and with the obtained data, their variations with the heating temperature and the cooling medium were established. Raising the heating temperature (between 760 ◦C and 820 ◦C) and using ultrasounds at cooling increased the volume fraction of martensite and the ferrite microhardness.

Farzad Badkoobeh, Hossein Mostaan

Ferritic–martensitic dual-phase (DP) steels are prominent and advanced high-strength steels (AHSS) broadly employed in automotive industries. Hence, extensive study is conducted regarding the relationship between the microstructure and mechanical properties of DP steels due to the high importance of DP steels in these industries. In this respect, this paper was aimed at reviewing the microstructural characteristics and strengthening mechanisms of DP steels. This review article represents that the main microstructural characteristics of DP steels include the ferrite grain size (FGS), martensite volume fraction (MVF), and martensite morphology (MM), which play a significant role in enhancing the mechanical performance of these materials. The analysis of these factors allows for a deeper understanding of the material behavior under stress and contributes to optimizing the design and application of DP steels in various industrial contexts. By consolidating the findings from numerous studies, the review provides valuable insights into future research directions and technological advancements needed for the further improvement of these advanced steels.

Rui Zhao, Han Su

This paper presents an integrated multi-attribute decision-making (MADM) approach to aid selection of commercially available materials in the context of sustainable design. The MADM couples grey relational analysis (GRA) with an analytic hierarchy process (AHP) to rank alternative materials in terms of their economic, environmental, and social performance. AHP is used to determine the corresponding weighting values for the selected indicators. In addition, a case example is used to verify the proposed MADM method and demonstrate its practical application. Three alternative polymer materials, i.e., poly(vinyl chloride) (PVC), polypropylene (PP), and polyethylene (PE), are examined to determine their sustainability for plastic pipe design. The associated MADM result and the limitations of the approach are discussed to lay the foundation for further improvement.

Mattia Italia, Flavia Papile

Design can play a fundamental role in addressing the climate crisis and preserving the planet’s finite resources. Through design, it is possible to reduce the environmental impact of products and services right from the concept stage. The elements that concur within a project are diverse and often have an impact on each other. The material is one of them, being able to influence the product, but also the business model and company relations. To help the designer keep all these aspects under control, various methodologies and tools have been developed, among them design strategies and guidelines. To date, several authors have dealt with the topic, offering different perspectives and generating a critical mass of information, which differs in the level of depth and operability of the suggestions, often differing only in terminology rather than content. This inhomogeneity can confuse both professionals and students. This study proposes an ordered taxonomy of the different levels of detail and a unified terminology of the strategies and guidelines in the literature. To test taxonomy and systematisation, this article focuses on guidelines for material choice, resulting in a.

Renan Felinto de Farias Aires, Luciano Ferreira

Sustainable material selection is a crucial problem given the new demands of society and novel production strategies that consider the concepts of sustainability. Multi-criteria decision-making methods have been extensively used to help decision-makers select alternatives in different fields of knowledge. Nonetheless, these methods have been criticized due to the rank reversal problem, where the independence of the irrelevant alternative principle is violated after the initial decision problem is changed. Over the course of this study, we observed that the solutions that are proposed for this problem, in the context of sustainable material selection, are insufficient. Thus, we present a new material selection approach that is based on the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method, which is immune to rank reversal. We also demonstrate the causes of rank reversal in the TOPSIS method, how the R-TOPSIS method was designed to solve them, and how it can be applied to sustainable material selection.

Lorenzo Vaiani, Antonio Boccaccio

A growing interest in creating advanced biomaterials with specific physical and chemical properties is currently being observed. These high-standard materials must be capable to integrate into biological environments such as the oral cavity or other anatomical regions in the human body. Given these requirements, ceramic biomaterials offer a feasible solution in terms of mechanical strength, biological functionality, and biocompatibility. In this review, the fundamental physical, chemical, and mechanical properties of the main ceramic biomaterials and ceramic nanocomposites are drawn, along with some primary related applications in biomedical fields.

Kristin S. Ødegaard, Jan Torgersen

Biomaterials are in high demand due to the increasing geriatric population and a high prevalence of cardiovascular and orthopedic disorders. The combination of additive manufacturing (AM) and biomaterials is promising, especially towards patient-specific applications. With AM, unique and complex structures can be manufactured. Furthermore, the direct link to computer-aided design and digital scans allows for a direct replicable product. However, the appropriate selection of biomaterials and corresponding AM methods can be challenging but is a key factor for success. This article provides a concise material selection guide for the AM biomedical field. After providing a general description of biomaterial classes—biotolerant, bioinert, bioactive, and biodegradable—we give an overview of common ceramic, polymeric, and metallic biomaterials that can be produced by AM and review their biomedical and mechanical properties. As the field of load-bearing metallic implants experiences rapid growth, we dedicate a large portion of this review to this field and portray interesting future research directions. This article provides a general overview of the field, but it also provides possibilities for deepening the knowledge in specific aspects as it comprises comprehensive tables including materials, applications, AM techniques, and references.

Omar Sarwar Chaudhary, Mouloud Denaï

Silicon (Si)-based semiconductor devices have long dominated the power electronics industry and are used in almost every application involving power conversion. Examples of these include metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), gate turn-off (GTO), thyristors, and bipolar junction transistors (BJTs). However, for many applications, power device requirements such as higher blocking voltage capability, higher switching frequencies, lower switching losses, higher temperature withstand, higher power density in power converters, and enhanced efficiency and reliability have reached a stage where the present Si-based power devices cannot cope with the growing demand and would usually require large, costly cooling systems and output filters to meet the requirements of the application. Wide bandgap (WBG) power semiconductor materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond (Dia) have recently emerged in the commercial market, with superior material properties that promise substantial performance improvements and are expected to gradually replace the traditional Si-based devices in various power electronics applications. WBG power devices can significantly improve the efficiency and reliability of power electronics systems in diverse applications.

Weiwang Wang, Jiaqi Fan

Amorphous and nanocrystalline alloys, as novel soft magnetic materials, can enable high efficiency in a wide range of power conversion techniques. Their wide application requires a thorough understanding of the fundamental material mechanisms, typical characteristics, device design, and applications. The first part of this review briefly overviews the development of amorphous and nanocrystalline alloys, including the structures of soft magnetic composites (SMCs), the key performance, and the underlying property-structure correction mechanisms. The second part discusses three kinds of high-power conversion applications of amorphous and nanocrystalline alloys, such as power electronics transformers (PETs), high-power inductors, and high-power electric motors. Further detailed analysis of these materials and applications are reviewed. Finally, some critical issues and future challenges for material tailoring, device design, and power conversion application are also highlighted.

Pietro Anzini, Daniele Redoglio

Light scattering and turbidimetry techniques are classical tools for characterizing the dynamics and structure of single nanoparticles or nanostructured networks. They work by analyzing, as a function of time (Dynamic Light Scattering, DLS) or angles (Static Light Scattering, SLS), the light scattered by a sample, or measuring, as a function of the wavelength, the intensity scattered over the entire solid angle when the sample is illuminated with white light (Multi Wavelength Turbidimetry, MWT). Light scattering methods probe different length scales, in the ranges of ∼5–500 nm (DLS), or ∼0.1–5 µm (Wide Angle SLS), or ∼1–100 µm (Low Angle SLS), and some of them can be operated in a time-resolved mode, with the possibility of characterizing not only stationary, but also aggregating, polymerizing, or self-assembling samples. Thus, the combined use of these techniques represents a powerful approach for studying systems characterized by very different length scales. In this work, we will review some typical applications of these methods, ranging from the field of colloidal.

Yousaf Khan, Haleema Sadia

Nanoparticles typically have dimensions of less than 100 nm. Scientists around the globe have shown immense interest in the classification, synthesis, and characterization of nanoparticles due to their unique properties and vast applications in various fields, including medicine, electronics, and environmental remediation. This review aims to provide comprehensive insights into different methodologies employed for synthesizing and characterizing nanoparticles, alongside their practical applications. A systematic literature review was conducted, integrating various sources to compile current knowledge on the topic. The review highlights key classification techniques and synthetic approaches such as chemical reduction, sol-gel, and biological methods, and explores the characterization techniques, including electron microscopy and spectroscopy. The findings indicate a growing trend in using green synthesis methods due to their environmental friendliness and cost-effectiveness. Additionally, the review summarizes the significant applications of nanoparticles in fields such as drug delivery systems, catalysts, and energy storage solutions. The collective information presented serves as a valuable resource for researchers and practitioners, shedding light on future directions in the field of nanotechnology.

Zhe Chen, Xin He

The friction and wear behavior of materials are not intrinsic properties, but extrinsic properties; in other words, they can drastically vary depending on test and environmental conditions. In ambient air, humidity is one such extrinsic parameter. This paper reviews the effects of humidity on macro- and nano-scale friction and wear of various types of materials. The materials included in this review are graphite and graphene, diamond-like carbon (DLC) films, ultrananocrystalline diamond (UNCD), transition metal dichalcogenides (TMDs), hexagonal boron nitride (h-BN), boric acid, silicon, silicon oxide, silicates, advanced ceramics, and metals. Details of underlying mechanisms governing friction and wear behaviors vary depending on materials and humidity; nonetheless, a comparison of various material cases revealed an overarching trend. Tribochemical reactions between the tribo-materials and the adsorbed water molecules play significant roles; such reactions can occur at defect sites in the case of two-dimensionally layered materials and carbon-based materials, or even on low energy surfaces in the case of metals and oxide materials. It is extremely important to consider the effects of adsorbed water layer thickness and structure for a full understanding of tribological properties of materials in ambient air.

Enrico Ciulli

Tribology is related to all studies on friction, wear, and lubrication. One of the main aims of these studies is a reduction in friction and wear. Tribology is extremely vast, being also multidisciplinary and interdisciplinary. Therefore, it is very difficult to organize the several tribology subjects in a unique way and different classifications have been proposed by different authors. In this work, several subjects treated by tribology are reviewed and organized in six branches: Fundamental Tribology, Tribology of Materials and Lubricants, Micro and Nanotribology, Industrial Tribology, Biotribology, and New Frontiers of Tribology. The main subjects treated by the six branches are briefly reviewed in this paper in order to highlight the vastness of tribology and its important contribution to sustainability. Particularly, friction and wear reductions are strictly related to greater efficiency and material saving, which means less energy losses and material wastes, less pollution and therefore a more sustainable life according to the sustainable development goals. The connections among the latter and the several different tribological subjects are discussed.

Ana Pavlovic, Carlo Santulli

Polymer–metal hybrid composites (PMHCs) represent an emerging class of materials that combine the lightweight processability of polymers with the structural and functional advantages of metals. Recent advances in material design and manufacturing have shifted attention from traditional particulate or fibrous reinforcement toward metallic architectures—continuous, architected, or topologically optimized metallic networks intentionally embedded within polymer matrices. These metallic architectures play a key role in defining the composite’s global performance, influencing stiffness, energy absorption, failure mechanisms, and multifunctional properties such as electrical or thermal conductivity. This review examines how the geometry, connectivity, and topology of metallic reinforcements govern mechanical behavior and functional responses in PMHCs. Emphasis is placed on the interplay between architecture and interface design, including surface modification strategies and mechanical interlocking phenomena. Furthermore, the paper discusses the contribution of additive manufacturing technologies in enabling complex metallic architectures and hybrid processing routes. By integrating structural, interfacial, and manufacturing perspectives, this review develops a coherent framework for understanding how metallic architecture drives the evolution of PMHCs toward multifunctional and design-driven engineering applications. The analysis of the literature consistently indicates that architectural configuration—rather than material selection alone—represents the primary factor governing multifunctional performance.

Mihail Kolev

Metal matrix composites (MMCs) are engineered multiphase materials composed of a continuous metallic matrix that contains deliberately introduced reinforcing phases, aimed at enhancing various properties such as strength, stiffness, and wear resistance. The objective of this paper is to explore the characteristics, advantages, and applications of MMCs derived from different metal bases including aluminum, magnesium, and titanium. A comprehensive review of the processing methods and their impacts on the structural and functional performance of MMCs is presented, along with insights on interfacial bonding and the role of reinforcement distribution. The methodology includes an in-depth analysis of current research trends, the historical development of MMC concepts, and the collaborative effects of matrix and reinforcement phases on material properties. Results indicate that properties of MMCs are influenced not solely by the volume fraction of reinforcement but also by factors such as processing techniques, interfacial bonding quality, and the spatial architecture of the composite. This research provides valuable insights into the practical applications of MMCs in various industries, highlighting their potential to overcome limitations in conventional material performance. The findings aim to facilitate advancements in the design and application of MMCs in cutting-edge engineering fields.

Sebastian Sado, Ilona Jastrz˛ ebska

Nowadays, digitalization and automation in both industrial and research activities are driving forces of innovations. In recent years, machine learning (ML) techniques have been widely applied in these areas. A paramount direction in the application of ML models is the prediction of the material service time in heating devices. The results of ML algorithms are easy to interpret and can significantly shorten the time required for research and decision-making, substituting the trial-and-error approach and allowing for more sustainable processes. This work presents the state of the art in the application of machine learning for the investigation of MgO-C refractories, which are materials mainly consumed by the steel industry. Firstly, ML algorithms are presented, with an emphasis on the most commonly used ones in refractories engineering. Then, we reveal the application of ML in laboratory and industrial-scale investigations of MgO-C refractories. The first group reveals the implementation of ML techniques in the prediction of the most critical properties of MgO-C, including oxidation resistance, optimization of the C content, corrosion resistance, and thermomechanical properties.

Ivan Veselov, Georgiy Shakhgildyan

Glass-ceramics are inorganic, non-metallic materials obtained by controlled crystallization of glasses through different processing routes; they contain at least one functional crystalline phase together with a residual glass, and the crystallized fraction may range from trace levels to nearly complete crystallization. Transparent glass-ceramics (TGCs) constitute the optically transparent subset of this class and combine a controlled crystalline microstructure with a residual amorphous matrix. Their transparency distinguishes them from conventional opaque glass-ceramics and is achieved by minimizing light scattering through careful control of crystallite size, volume fraction, spatial distribution, and refractive-index mismatch between the crystalline and glassy phases. Unlike conventional sintered ceramics, TGCs retain many of the processing advantages of glass while incorporating crystalline phases that can enhance mechanical, thermal, optical, or functional properties. Depending on their composition and microstructure, TGCs may exhibit improved hardness, fracture toughness, thermal stability, chemical durability, luminescence, nonlinear optical response, or ion-exchange strengthening capability. These features make TGCs attractive for applications requiring both optical clarity and advanced performance, including protective cover glass, transparent armour, precision optical substrates, laser and photonic components, optical sensors, and multifunctional host materials for rare-earth ions and nanoparticles.

Wenxin Tan, Ran Fu

Zirconia-toughened alumina (ZTA) ceramics are promising for load-bearing biomedical applications because they combine the hardness, chemical stability, wear resistance, and biocompatibility of alumina with the transformation-toughening capability of zirconia. Grinding is indispensable for achieving dimensional accuracy and surface quality, yet it inevitably introduces surface and subsurface cracks, residual stresses, and a local tetragonal-to-monoclinic transformation of zirconia. These changes can degrade fracture toughness, increase reliability scatter, and reduce long-term service stability. Annealing is therefore often considered a post-grinding recovery strategy because it can relax residual stresses, blunt crack tips, and partially restore the zirconia phase state. However, the extent of recovery depends strongly on the initial damage state, ZTA microstructure, and thermal schedule. This review systematically summarizes the current understanding of grinding-induced damage and annealing-assisted recovery in ZTA ceramics, with particular emphasis on the coupled relationships among subsurface damage, residual-stress evolution, phase transformation, and fracture toughness. Particular attention is given to distinguishing direct ZTA-specific evidence from mechanistic interpretations inferred from related zirconia-containing ceramic systems.

Subin Antony Jose, John Crosby

Ceramics are widely evaluated for their extreme hardness, high-temperature stability, and corrosion resistance, which enable applications in harsh service environments. However, these same properties, high melting points, brittleness, and low thermal shock resistance, make conventional manufacturing of complex ceramic components difficult and expensive. Traditional processes often require costly diamond tooling or energy-intensive sintering and tend to produce only simple geometries, with significant waste material and risk of defects. Additive manufacturing (AM) has recently emerged as a promising route to fabricate intricate, near-net-shape ceramic parts without these drawbacks. By building components layer by layer, AM reduces the need for extensive machining and enables the fabrication of geometrically complex, near-net-shape ceramic structures with reduced material waste, although challenges such as porosity, interlayer defects, and cracking during post-processing remain. Nonetheless, ceramic AM technologies lag behind their metal and polymer counterparts, and significant challenges remain in achieving fully dense parts with reliable mechanical properties. This review provides an in-depth overview of the state of the art in ceramics and ceramic composite additive manufacturing. We detail the most widely used AM processes (stereolithography, binder jetting, material extrusion, powder bed fusion, inkjet printing, and direct energy deposition) and typical feedstock formulations for each technique. We examine the resulting mechanical properties (strength, toughness, hardness, wear resistance) and functional properties (thermal stability, dielectric behavior, biocompatibility) of additively manufactured ceramics, and discuss their current and future potential.

Marina León-Calero, Sara Catherine Reyburn Valés

Additive manufacturing (AM) is a disruptive technology that enables one to manufacture complex structures reducing both time and manufacturing cost. Among the materials commonly used for AM, thermoplastic elastomers (TPE) are of high interest due to their energy absorption capacity, energy efficiency, cushion factor or damping capacity. Previous investigations have exclusively focused on the optimization of the printing parameters of commercial TPE filaments and the structures to analyse the mechanical properties of the 3D printed parts. In the present paper, the chemical, thermal and mechanical properties for a wide range of commercial thermoplastic polyurethanes (TPU) filaments were investigated. For this p.

Damián Peti, Jozef Dobránsky

Plastics, particularly synthetic organic polymers, have become indispensable in modern life, yet their large-scale production has led to significant environmental challenges due to persistent waste. Traditional mechanical recycling methods have proven insufficient in addressing these issues. This review explores recent advancements in polymer recycling, focusing on chemical and biological processes, such as pyrolysis, depolymerization, and enzyme-based degradation, which offer more efficient and sustainable alternatives. Within the framework of a circular economy, the review also examines strategies like closed-loop and circular plastic economies. These developments represent critical steps toward creating more sustainable plastic recycling practices. The final chapter includes the Quarterly Report 2024 on recycling plastics, providing an up-to-date overview of the current state of plastic recycling and its recent trends.

Leire Sangroniz, Mercedes Fernández

The contribution of Spanish scientists to the rheology involved in polymer processing during the last 25 years is investigated. It is shown that the performed research covers, at different levels, all industrial polymeric materials: thermoplastics, thermosets, adhesives, biopolymers, composites and nanocomposites, and polymer modified bitumen. Therefore, the rheological behaviour of these materials in processing methods such as extrusion, injection moulding, additive manufacturing, and others is discussed, based on the literature results. A detailed view of the most outstanding achievements, based on the rheological criteria of the authors, is offered.

Alexey E. Svirid, Vladimir G. Pushin

Using the methods of electron microscopy and X-ray analysis in combination with measurements of the electrical resistance and magnetic susceptibility, the authors have obtained data on the peculiar features of pre-martensitic states and martensitic transformations, as well as subsequent decomposition, in the alloys with shape memory effect of Cu–14wt%Al–3wt%Ni and Cu–13.5wt%Al–3.5wt%Ni. For the first time, we established the microstructure, phase composition, mechanical properties, and microhardness of the alloys obtained in the nanocrystalline state as a result of severe plastic deformation under high pressure torsion and subsequent annealing. A crystallographic model of the martensite nucleation and the rearrangements β1→β1′and β1→γ1′are proposed based on the analysis of the observed tweed contrast and diffuse scattering in the austenite and the internal defects in the substructure of the martensite.

Vladimir G. Pushin, Nataliya N. Kuranova

An overview is presented on the structural and phase transformations and physical and mechanical properties of those multicomponent copper-based shape memory alloys which demonstrate attractive commercial potential due to their low cost, good shape memory characteristics, ease of fabrication, and excellent heat and electrical conductivity. However, their applications are very limited due to brittleness, reduced thermal stability, and mechanical strength—properties which are closely related to the microstructural features of these alloys. The efforts of the authors of this article were aimed at obtaining a favorable microstructure of alloys using new alternative methods of thermal and thermomechanical treatments. For the first time, the cyclic martensitic transformations during repeated quenching, methods of uniaxial megaplastic compression, or torsion under high pressure were successfully applied for radical size refinement of the grain structure of polycrystalline Cu-Al-Ni-based alloys with shape memory.

David Blanco, Eva María Rubio

The reduction of consumption and pollutant emissions is a top priority for the transport sector. One working line is the substitution of conventional structural materials with lightweight materials such as metallic alloys of aluminium, titanium, and/or magnesium. For this reason, and considering that the number of related articles is lower than the existing number of other structural lightweight materials, it is considered very convenient and helpful to carry out a systematic analysis of their latest trends through Open Access literature. A methodology adapted from the PRISMA statement is applied, in order to guarantee unbiasedness and quality in selecting literature and research. The final selection is made up of the 40 most cited research papers from 2015–2020, with an average of 20.6 citations per article. Turning and drilling are the most trending techniques in the context of these materials.

Peter Jurˇ ci, Ivo Dlouhý

Conventional heat treatment is not capable of converting a sufficient amount of retained austenite into martensite in high-carbon or high-carbon and high-alloyed iron alloys. Cryogenic treatment induces the following alterations in the microstructures: (i) a considerable reduction in the retained austenite amount, (ii) formation of refined martensite coupled with an increased number of lattice defects, such as dislocations and twins, (iii) changes in the precipitation kinetics of nano-sized transient carbides during tempering, and (iv) an increase in the number of small globular carbides. These microstructural alterations are reflected in mechanical property improvements and better dimensional stability. A common consequence of cryogenic treatment is a significant increase in the wear resistance of steels. The current review deals with all of the mentioned microstructural changes as well as the variations in strength, toughness, wear performance, and corrosion resistance for a variety of iron alloys, such as carburising steels, hot work tool steels, bearing and eutectoid steels, and high-carbon and high-alloyed ledeburitic cold work tool steels.

Druce Dunne

Martensite and martensitic transformations in metals and alloys have been intensively studied for more than a century and many comprehensive and informative reviews have been published. The current review differs insofar as the analysis is performed largely through the prism of detailed studies of the changes in the martensitic transformation in Fe 3Pt alloy as a result of austenite ordering. This important alloy is the first ferrous alloy identified as exhibiting thermoelastic transformation and shape memory. The effect of parent phase order on the martensitic transformation offers significant insights into general understanding of the nature of martensitic transformation, particularly the factors contributing to reversible and irreversible transformation. It is concluded that for crystallographically reversible transformation to occur both strain limiting and strain accommodating factors must be present and that these factors collectively constitute the sufficient condition for reversible martensitic transformation. Although the crystallography of individual plates formed in a given alloy can change with their temperature of formation, this intrinsic variability has not been considered in analyses using phenomenological theory. Significantly, variability can exist in measured quantities such as habit plane normals and orientation relationships used to test theoretical predictions. Measured lattice parameters, essential data for theoretical calculations, can also differ from the actual parameters existing at the temperature of plate formation.

Halina Krawiec, Janusz Lelito

The influence of heat treatment parameters such as the annealing time and austempering temperature on the microstructure, tribological properties and corrosion resistance of ductile iron have been investigated. It has been revealed that the scratch depth of cast iron samples increases with the extension of the isothermal annealing time (from 30 to 120 min) and the austempering temperature (from 280 ◦C to 430 ◦C), while the hardness value decreases. A low value of the scratch depth and a high hardness at low values of the austempering temperature and short isothermal annealing time is related to the presence of martensite. Moreover, the presence of a martensite phase has a beneficial influence on the corrosion resistance of austempered ductile iron.

Ojo Jeremiah Akinribide, Olasupo Daniel Ogundare

The isothermal heat treatment process has been identified as a unique process of fabricating exceptional graphite cast iron due to its remarkable mechanical properties, such as excellent machinability, toughness, and high level of ultimate tensile strength. Austempered ductile iron (ADI), ductile iron (DI), and gray cast iron (GCI), known as spheroidal cast irons, are viable alternative materials compared to traditional steel casting, as well as aluminum casting. The graphite nodules from the microstructures of DI, ADI, and GCI are consistently encompassed by acicular ferrite and carbon-saturated austenite in the matrix, forming a distinctive ausferritic structure. All these materials are extensively used in the fabrication of engine sleeves, engine blocks, valves, gears, and camshafts in the automobile sector. With relative motion and outward loads, these components are regular.

Rui Pereira, Nuno Peixinho

This paper presents a review on the formability evaluation of advanced high-strength steels (AHSS), focusing on enhancing the limitations of necking-based failure criteria. It discusses complementary fracture and damage constitutive modeling approaches specifically tailored for formability evaluation, validated through both numerical and experimental methods. AHSS are increasingly used in sheet metal forming processes due to their lightweight, high-strength, and ductility properties; however, their multi-phase microstructure poses significant forming challenges. The research highlights the necessity for improvements in modeling forming behavior, particularly regarding necking-based failure criteria and direct fracture models. The conventional forming limit diagram/curve (FLD/FLC) is shown to have limitations in estimating direct fracture scenarios, including surface, edge, and shear cracks, especially under non-linear strain paths. Therefore, substantial research efforts are underway to develop advanced fracture constitutive models capable of predicting fracture scenarios that do not involve necking, which are increasingly prevalent in the context of AHSS. The scientific community is exploring various directions to enhance the accuracy of forming and fracture behavior predictions for components manufactured using AHSS.

Roger Francis, Glenn Byrne

Duplex stainless steels were first manufactured early in the 20th century, but it was the introduction in the 1970s of the argon-oxygen decarburisation (AOD) steel making process and the addition of nitrogen to these steels, that made the alloys stronger, more weldable and more corrosion resistant. Today, duplex stainless steels can be categorised into four main groups, i.e., "lean", "standard", "super", and "hyper" duplex types. These groups cover a range of compositions and properties, but they all have in common a microstructure consisting of roughly equal proportions of austenite and ferrite, high strength, good toughness and good corrosion resistance, especially to stress corrosion cracking (SCC) compared with similar austenitic stainless steels. Moreover, the development of a duplex stainless-steel microstructure requires lower levels of nickel in the composition than for a corresponding austenitic stainless steel with comparable pitting and crevice corrosion resistance, hence they cost less. This makes duplex stainless steels a very versatile and attractive group of alloys both commercially and technically. There are applications where duplex grades can be used as lower cost through-life options, in preference to coated carbon steels, a range of other stainless steels, and in some cases nickel alloys. This cost benefit is further emphasised if the design engineer can use the higher strength.