Abstract: The effect of a pre-nitriding treatment, applied prior to vacuum carburizing, on the carburizing efficiency of 20CrMnTi steel is investigated. The results demonstrate that pre-nitriding significantly enhances the vacuum carburizing efficiency of 20CrMnTi steel, refines the martensitic microstructure of the carburized layer, and promotes carbide precipitation. At the same carburized layer depth, the hardness and carbon content of the pre-nitriding samples are markedly higher than those of the without pre-nitriding samples. Specifically, the effective hardened depth and the surface hardness increase by approximately 0.15 mm and 75 HV500gf, respectively. These improvements are attributed to the formation of loose, porous nano-sized nitride particles on the surface during the pre-nitriding process, which substantially increases the surface roughness and pore volume. This surface morphology facilitates the adsorption and inward diffusion of carbon atoms during carburizing, and the presence of nitrogen in solid solution further enhances carbon diffusion.

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Ti alloys are widely used in several fields, such as aerospace and biomedical, due to their high mechanical properties under severe loading conditions. Recently, the interest in these materials produced by additive manufacturing process has increased, but intensive research should be done to better characterise their properties. This work aims to study and compare the effect of surface properties, internal defects, microstructure, hardness and Hot Isostatic Pressing (HIP) treatment or in-Vacuum Heat Treatment (VHT) on fatigue properties of a Ti6Al4V produced by Selective Laser Melting (SLM) and Electron Beam Melting (EBM) additive manufacturing technologies. The samples were fully characterised using a wide range of techniques, in terms of microstructure (optical microscopy and SEM), mechanical properties (hardness mapping) and surface texture (confocal microscopy). The internal defects were evaluated using an image-based analysis approach. The uniaxial fatigue endurance limit properties were determined by a Dixon-Mood staircase approach and the failed samples near the fatigue limit were characterised by fracture surface and defect area analysis. A study of the applied load on the flaw areas was carried out to unveil the root causes of fatigue failure. The results showed that the fatigue properties of the as-printed samples were mainly determined by the surface roughness, whereas in the machined samples the internal defect dimension ruled the fatigue resistance of the material. The HIP used as a post-printing treatment is effective in substantially reducing the presence of internal pores, although local microstructural changes can take place only in the case of smooth surface. In conclusion, when properly developed in their melted parameters, both EBM and SLM technologies produce similar mechanical performance on comparable roughness levels, thus finding shared fields of application and fully eligible for the production of structural components.

Abstract: Copper-aluminum layered composites offer a promising combination of high conductivity, light weight, and cost-effectiveness, making them attractive for applications in electric vehicles, electronics, and power transmission. However, achieving reliable interfacial bonding while avoiding excessive work hardening and brittle intermetallic formation remains a significant challenge. In this study, a Cu18150/Al1060/Cu18150 trilayer composite was fabricated through a three-stage high-temperature oxygen-free rolling process. Subsequently, the produced composite was subjected to annealing treatments to systematically investigate the effects of rolling passes, annealing temperature/time on interfacial evolution and mechanical behavior. Results indicate that rolling passes primarily influence interfacial topography and defect distribution. Fewer passes lead to wavy, mechanically bonded interfaces, while more passes improve flatness but reduce intermetallic continuity. Annealing temperature critically governs diffusion kinetics; temperatures up to 400 °C promote the formation of a uniform Al2Cu layer, whereas 450 °C accelerates the growth of brittle Al4Cu9, thickening the intermetallic layer to 18 μm and compromising toughness. Annealing duration further modulates diffusion mechanisms, with short-term (0.5 h) treatments favoring defect-assisted diffusion, resulting in a porous, rapidly thickened layer. In contrast, longer annealing (≥1 h) shifts toward lattice diffusion, which densifies the interface but risks excessive brittle phase formation if prolonged. Mechanical performance evolves accordingly; as-rolled strength increases with the number of rolling passes, but at the expense of ductility. Annealing transforms bonding from a mechanical to a metallurgical condition, shifting fracture from delamination to collaborative failure. The identified optimal process, single-pass rolling followed by annealing at 420°C for 1 hour, yields a balanced interfacial structure of Al2Cu, AlCu, and Al4Cu9 phases, achieving a tensile strength of 258.9 MPa and an elongation of 28.2%, thereby satisfying the target performance criteria (≥220 MPa and ≥20%).

Abstract: The growing emphasis on environmental sustainability and the need for advanced manufacturing methods have accelerated progress in materials processing. Aluminum powder metallurgy (APM) is particularly promising due to aluminum’s low density, high strength-to-weight ratio, and the inherent benefits of the powder metallurgy (PM) process. However, the corrosion resistance of sintered aluminum components remains a significant concern. In this study, shot peening (SP) was employed as a surface modification technique to improve the corrosion behavior of Alumix 321 PM alloy. Sampleas of the as-sintered and shot peened Alumix 321 PM alloy, together with the wrought alloy counterpart AA6061, were characterized using non-contact optical profilometry, optical microscopy (OM), and scanning electron microscopy (SEM). Corrosion performance was evaluated in 3.5 wt.% NaCl solution using Tafel extrapolation (TE), cyclic polarization (CP), stair-step polarization (SSP), and electrochemical impedance spectroscopy (EIS). The results revealed that shot peening increased surface roughness and significantly reduced the corrosion rate from 0.079 mmpy to 0.004 mmpy for the unpeened and peened samples, respectively. While pitting was the dominant corrosion mechanism in the wrought alloy, the PM alloy exhibited a combination of pitting, crevice, and intergranular corrosion. These findings highlight the potential of SP in enhancing the durability of aluminum-based PM components, offering valuable insights for industrial applications.

Abstract: To address the challenge of poor separation performance exhibited by conventional magnetic separation equipment when processing coarse-grained, low-grade magnetite ore, this paper proposes a novel ore recognition method that integrates empirical mode decomposition (EMD) with a convolutional neural network (CNN). First, the normalized magnetic induction intensity signals are decomposed using EMD to yield a series of intrinsic mode functions (IMFs). IMFs containing prominent characteristic information are then selected and fused based on their dominant frequency and kurtosis values, resulting in a reconstructed signal with significantly reduced noise. Subsequently, the reconstructed signals undergo inversion, re-normalization, and dimensional transformation into a two-dimensional matrix format to construct the training and testing sample datasets. A convolutional neural network is then designed and optimized to automatically extract discriminative features from these preprocessed samples, enabling accurate classification of magnetite ore grades. Experimental results demonstrate that the proposed EMD-CNN framework achieves effective and stable classification performance across different ore grades. In particular, the application of EMD for noise component removal substantially enhances the CNN’s recognition accuracy for waste rock and medium-grade ore, which are traditionally the most difficult categories to distinguish.

Abstract: Carbon Steel SA 178 grade C is a common material used for boiler tubes. A boiler is a crucial unit in the energy industry, meanwhile its services life can be degraded after long term operation. If it malfunctions, the processing operations must be halted, resulting in financial losses for the company. The aim of this study is to examines the effect of microstructural evolution especially transformation of lamellar pearlite into spheroidized pearlite on the service life degradation of boiler tubes. Understanding these changes is essential for preventing catastrophic system failures. The methodology of this study involves the use of Small-Angle X-ray Scattering (SAXS), supported by metallographic analysis, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), and mechanical testing. The SAXS results indicate that the microstructure of SA-178, initially consisting of lamellar ferrite and pearlite, gradually transforms into spheroidized pearlite. These microstructural changes lead to reductions in tensile strength from 523 MPa for 0% spheroidization to 335 MPa for 100% spheroidization, and hardness from 175HV to 89 HV, ultimately decreasing the service life of the boiler tube.

Abstract: This study presents the first atomistic modeling investigation of Additive Friction Stir Deposition (AFSD), providing detailed insights into thermomechanical and microstructural evolution at the nanoscale. Molecular dynamics simulations using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) were employed to capture the complex interplay of rotation, translation, and frictional heating during aluminum deposition. The aluminum system was modeled using an Embedded Atom Method potential with periodic boundary conditions, enabling realistic representation of material flow and layer formation. Comprehensive atomistic diagnostics revealed that severe plastic deformation is highly localized at the tool-substrate interface, with elevated shear strain concentrated beneath the rotating feedstock. Analysis of atomic coordination numbers demonstrated significant lattice distortion in the interfacial region, while dislocation structure characterization identified defect clustering associated with plastic strain accumulation. Voronoi tessellation-based analyses quantified heterogeneous atomic packing, free-volume generation, and cavity formation, correlating spatially with regions of intense deformation. These results show that AFSD promotes metallurgical bonding through confined interfacial mixing while preserving substrate integrity. The atomistic framework developed here establishes a foundation for understanding deformation mechanisms, optimizing process parameters, and predicting microstructural evolution in solid-state additive manufacturing, offering insights complementary to experimental observations at macroscopic scales.

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In alignment with the European Union’s 2050 carbon neutrality targets, the automotive industry is intensifying efforts to adopt lightweight materials that ensure structural integrity without compromising safety. Press-hardened steels (PHS), offering a combination of ultra-high strength and formability, are at the forefront of these developments. Standard PHS grades rely on Ti-B microalloying; however, further alloying with Nb and V has been proposed to enhance hydrogen embrittlement resistance via microstructural refinement and hydrogen trapping. This study investigates hydrogen transport and mechanical degradation in a Ti-Nb-V microalloyed PHS compared to a conventional Ti-only 22MnB5 grade. Electrochemical permeation, thermal desorption, and mechanical testing were employed to characterize hydrogen diffusivity, solubility, and trapping mechanisms. The Ti-Nb-V variant demonstrated lower hydrogen diffusivity, higher solubility, and improved resistance to delayed fracture, attributable to the presence of fine NbTiV precipitates.

Abstract: Complementing the steady state modeling of an ideal solar evaporation pond, the present study is concerned with the dynamic modeling of the ideal solar evaporation pond for Li extraction from brines. The approach conceptualizes the pond as a sequence of discrete particles of brine of suitable size with continuous feeding and discharging considering water evaporation events over time. The discrete dynamic model produces a dynamic concentration profile over time, which converges to a steady-state concentration profile equal to that predicted by the ideal solar evaporation law. This discrete dynamic particle model allows for variations in feed flow rate, evaporation rate per unit area, feed concentration, and pond area. This approach allows the visualization of concentration perturbations propagating at a finite speed through the system exhibiting a hyperbolic nature. The model was validated using average lithium, boron, and magnesium concentrations obtained from an industrial pond system at the Salar de Atacama, Chile, in the year 2023. Therefore, this discrete dynamic model constitutes a versatile tool for analyzing and optimizing the performance of solar evaporation pond systems under variable operating conditions.

Abstract: The pitting corrosion resistance and the tribological behaviour of a ferritic stainless steel with high Mo content (AISI 436) and a commonly employed austenitic stainless steel (AISI 304) are compared. Special attention was paid to the role of Mo in improving corrosion resistance of ferritic stainless steels. Since the surface condition is an important parameter related to the onset of pitting corrosion in the presence of chlorides, three different surface finishes were tested for both steels. Two commercial finishing grades and laboratory polishing down to 1 µm were compared. Moreover, the influence of surface condition on the tribological properties for both steels was also evaluated. The study demonstrates that surface finishing plays a decisive role in both the electrochemical and mechanical response of stainless steels. A comprehensive microstructural and tribological analysis reveals not only how commercial finishing treatments modify passive film behaviour, but also how they affect friction stability and wear mechanisms. Special emphasis is placed on the synergistic effect between molybdenum content, passive film integrity and manufacturing processes. The obtained results provide valuable insight for industrial applications where durability against chloride exposure and abrasion is critical.

Abstract: Grey cast iron brake discs are widely used in automotive applications due to their excel-lent thermal and mechanical properties. However, stricter environmental regulations such as Euro 7 demand improved surface durability to reduce particulate emissions and corro-sion-related failures. This study evaluates multilayer coatings fabricated by Laser Metal Deposition (LMD) as a potential solution. Two multi-layer systems were investigated: 316L+(316L+WC) and 316L+(430L+TiC), which were primarily reinforced with ceramic additives to increase wear resistance, with their influence on corrosion being critically evaluated. Electrochemical tests in 5 wt.% NaCl solution (DIN 17475) revealed that the 316L+(316L+WC) coating exhibited the lowest corrosion current density and most stable passive behavior, consistent with the inherent passivation of the austenitic 316L matrix. In contrast, the 316L+(430L+TiC) system showed localized corrosion associated with mi-cro-galvanic interactions, despite the chemical stability of TiC particles. Post-corrosion SEM and EDS confirmed chromium depletion and chloride accumulation at corroded sites, while WC particles exhibited partial dissolution. These findings highlight that ce-ramic reinforcements do not inherently improve corrosion resistance and may introduce localized degradation mechanisms. Nevertheless, LMD-fabricated multilayer coatings demonstrate potential for extending brake disc service life, provided that matrix–reinforcement interactions are carefully optimized.

Abstract: Titanium alloys are widely employed for biomedical implants due to their favourable combination of strength, corrosion resistance, and biocompatibility. A drawback, however, is the lack of intrinsic antibacterial functionality. In this study, Ti 6Al 7Nb was modified with varying copper (Cu) contents (1 wt.% – 9 wt.%) via in situ alloying during metal based laser powder bed fusion (PBF-LB/M) to investigate the processing behaviour, microstructural evolution, and mechanical properties. Powder mixtures were processed under systematically varied laser parameters, with densification, surface quality, and microstructure assessed by microscopy and X-ray diffraction, while hardness and tensile properties were characterised through mechanical testing. The results demonstrate that dense samples (> 99.9 %) can be achieved for all investigated copper amounts, although the homogeneity is strongly dependent on the process parameters. An increasing copper content promotes β-phase stabilisation, Ti₂Cu precipitation, and significant grain refinement with a transition from columnar to equiaxed structures. Hardness and yield strength increase nearly linearly with increasing copper content, while the ductility decreases sharply at ≥ 5 wt.% Cu due to intermetallic formation, hot cracking, and brittle fracture mechanisms. These findings highlight both the potential and the limitations of copper additions in Ti 6Al 7Nb processed by PBF LB/M. Overall, moderate additions of 1 wt.% – 3 wt.% Cu appear most promising, offering improved mechanical performance while preserving sufficient ductility and manufacturability for biomedical applications.

Abstract: Enhancing the local mechanical response of low-carbon cast steels remains essential for improving their performance in wear-intensive environments. In this work, a low-carbon cast steel was locally modified through the in situ formation of TiC particles via melt reaction with pressed Ti–Al–C powders. Advanced microstructural characterization (SEM/EDS, EBSD, and TEM) revealed a heterogeneous TiC-reinforced composite microstructure containing ~36 vol.% TiC with particle sizes between 0.73 and 3.88 μm. The reinforced region exhibited a substantial increase in hardness, from 160 ± 5 HV30 in the base steel to 407 ± 78 HV30, resulting from the synergistic contribution of TiC particles, fine κ-carbides, and a martensitic matrix. Nanoindentation revealed a strong mechanical contrast between phases, with TiC achieving 25.70 ± 7.76 GPa compared to 4.68 ± 1.09 GPa for the base metal matrix. Micro-abrasion tests showed a 24% reduction in wear rate, accompanied by shallower grooves and reduced plastic deformation. These findings demonstrate that in situ TiC formation, combined with κ-carbide precipitation, provides an effective strategy for improving local hardness and abrasive wear resistance in low-carbon cast steels. The results highlight the potential of in situ composite formation as an effective microstructural engineering strategy for next-generation wear-resistant cast steels.

Abstract: This study investigates the feasibility of efficiently recovering lead and silver from a lead cake by applying a combined process of chlorination roasting followed by acid leaching. The lead cake is obtained after the sulfuric acid leaching of zinc ferrite residues generated during the hydrometallurgical treatment of zinc calcine. The influence of roasting temperature, the mass ratio between lead cake and NaCl, and the roasting duration on metal extraction was systematically investigated to determine optimal process conditions. The most efficient parameters were identified as roasting at 550 °C for 1.5 hours with a lead cake to NaCl ratio of 1:3, followed by leaching the roasted product in 1 M HCl. Under these conditions, the remaining Pb and Ag contents in the final solid residue were reduced to 0.90 % and 0.0027 %, respectively, indicating nearly complete chlorination and subsequent dissolution of both metals. A comparative evaluation showed that the combined chlorination roasting–leaching approach resulted in higher recovery rates (Pb 98.67 %, Ag 98.09 %) and a smaller final residue mass than direct chloride leaching (Pb 96.79 %, Ag 84.55 %). Therefore, the proposed method is demonstrated to be more effective and environmentally advantageous for recovering valuable metals from industrial waste materials.

Abstract: To address the technical challenges in the resource utilization of hot metal containing high levels of vanadium (V: 2–5%) and chromium (Cr: 1–5%), this paper proposes a novel method based on pyrometallurgical selective oxidation for the simultaneous extraction of vanadium and retention of chromium. Through thermodynamic analysis and high-temperature smelting experiments, the competitive oxidation behaviors of carbon, vanadium, and chromium were revealed, and the synergistic control mechanism of temperature and oxygen partial pressure was clarified. The results indicate that within the temperature range of 1693–1753 K, vanadium preferentially oxidizes over carbon and chromium, while carbon effectively suppresses chromium oxidation. By optimizing the ω(FeO) (10.0–15.7%), achieving a vanadium oxidation efficiency (ηV) of 72.5–82.2% and maintaining the chromium retention efficiency (1–ηCr) exceeding 57.1%. Compared to traditional methods—which rely on high-oxygen blowing (oxygen supply: 43–195 kg/tFe), multi-stage roasting, and hydrometallurgical refining—this approach eliminates roasting and hydrometallurgical steps, shortens the process chain, reduces oxygen consumption (> 80 kg/tFe), and lowers environmental risks (Cr oxidation reduced > 40%). The study establishes a theoretical framework for sustainable V/Cr separation, enhancing resource efficiency and minimizing pollution.

Abstract: The Mg-Y-Zn alloy system is well known for its outstanding combination of high strength and ductility, even at relatively low concentrations of alloying elements. This exceptional performance is primarily at-tributed to its characteristic microstructure, which features Long-Period Stacking Ordered (LPSO) phases and the distinctive Mille-Feuille Structure (MFS). Kink-induced strengthening, developed during thermomechanical processing, has emerged as a promising strategy to simultaneously enhance strength and ductility. In this study, the beneficial effect of pre-deformation aimed at introducing additional kinks into the microstructure prior to extrusion is demonstrated. The subsequent extrusion process promotes dynamic recrystallization (DRX), generating fine DRX grains while preserving kink structures in the non-DRX regions. As a result, the yield strength is enhanced by approximately 80 MPa, accompanied by a slight improvement in ductility.

Abstract: This study develops a sustainable welding approach by incorporating 35–50% blast furnace slag (BFS), a byproduct of the steel industry, into rutile-type electrode coatings. Electrodes were fabricated by dry mixing BFS with fluxes, adding potassium silicate binder to form a paste, pressing at 150 bar onto a 3.25 mm core wire, and heat treatment at 150°C for two hours. Weld quality and performance were evaluated through visual inspections, microstructure and XRD analyses, hardness, tensile, and impact tests. Visual inspections confirmed weld quality comparable to commercial standards, with stable arc and minimal spatter. Microstructure analysis revealed a fer-rite-dominated weld metal with TiO₂ and FeTiO₃ phases in the slag layer, enhancing strength and toughness. Electrodes with 35–40% BFS achieved yield strength of 477–482 MPa, tensile strength of 570–573 MPa, and impact energy of 58–59 J at 0°C, complying with ISO 2560:2020. BFS integration reduced CO₂ emissions by 0.28–0.4 kg per kg of coating and diverted 200–600 kg of slag per ton of steel from landfills. Coating and raw material costs decreased by 33–48% and 15–25%, respectively, aligning with the EU Green Deal’s circular economy goals and enhancing weld quality and sustainability.

Abstract: This study explores the application of lattice structures as internal support architectures in the fabrication of Inconel 718 components via Laser Powder Bed Fusion (L-PBF), building upon previous research on beam-based FCCZ supports. Two representative lattice typologies were investigated: the node and beam-based FCCZ structure and the triply periodic minimal surface (TPMS) Schoen Gyroid cell. The aim was to assess how the transition from a discrete beam-node architecture to a continuous surface topology influences manufacturability, thermal stability, and mechanical performance. Finite Element Method (FEM) simulations in Ansys accurately predicted distortions and residual stresses during the L-PBF process, showing strong agreement with stereomicroscope measurements. After fabrication, the samples underwent solution treatment and double aging according to AMS 2774 and AMS 5662 standards. Microstructural analysis using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed that heat treatment partially homogenized the microstructure but did not achieve complete recrystallization, leaving localized dendritic regions and undissolved Laves phases, particularly near the lattice. The precipitation of γ′ and δ phases enhanced hardness and mechanical uniformity, as confirmed by Vickers microhardness testing. Overall, the Gyroid topology demonstrated superior manufacturability and thermal stability, exhibiting reduced defects and deformation compared to the FCCZ structure. These findings confirm its potential as an efficient and reliable self-supporting architecture for L-PBF Inconel 718 components intended for high-performance and thermally demanding applications.

Abstract: The present study systematically investigates the effect of homogenization treatment on the microstructural evolution, recrystallization behavior, and mechanical response of a hot-rolled Mg-3Al-1Zn-1Ca alloy. Detailed microstructural characterization revealed that Al2Ca precipitates were uniformly distributed along grain boundaries in the as-received (AR) condition, where they contributed to significant pinning of boundary migration. Homogenization treatment (350 °C, furnace cooling) resulted in non-uniform grain coarsening, driven by the interplay of precipitate pinning and differential stored strain energy, while also facilitating particle-stimulated nucleation (PSN) and recrystallization. Electron backscatter diffraction (EBSD) analysis confirmed a substantial increase in the fraction of high-angle grain boundaries and recrystallized grains in the heat-treated (HT) state, with kernel average misorientation (KAM) and grain orientation spread (GOS) analyses indicating pronounced recovery of lattice distortions. Mechanical testing demonstrated a significant decrease in yield strength (263 MPa to 187.4 MPa) and hardness (65.7 to 54.1 HV) due to dislocation annihilation and stress relaxation, while ultimate tensile strength remained nearly unchanged (~338 MPa) and ductility improved markedly (12.6% to 16.4%). These findings highlight the dual role of Al2Ca precipitates in promoting recrystallization through PSN while simultaneously restricting excessive grain growth through Zener pinning.

Abstract:

Ti-6Al-4V is valued for its strength-to-weight ratio in engineering applications. Cryo-rolling at sub-zero temperatures enhances strength and hardness through grain refinement and dislocation build-up. Present study investigates the role of cryo-rolling on the microstructural characteristics and mechanical properties of the alloy, which undergoes various degrees of deformation followed by heating at 900 °C for selected samples. Microstructural analysis reveals grain elongation, sub-grain formation, deformation bands, and dislocation densification with increasing thickness reduction. Twinning dominates deformation at low strain, while dislocation slips take over at high strain because of the decrease in grain size, which makes the formation of new twins progressively more challenging. No metastable phase appears during cryo-rolling or heat treatment, as confirmed by X-ray diffraction. Cryo-rolled samples exhibit about 45% and 28% reduction in grain size and crystallite size, and 152% intensification in dislocation density. This leads to rises of 23%, 19%, and 8% in yield strength, tensile strength, and hardness, respectively, while ductility remains nearly constant across all cryo-rolled conditions. Cryo-rolling inhibits dynamic recovery and recrystallisation, so strengthening mainly results from grain refinement and dislocation accumulation. These findings suggest that cryo-rolling can improve the strength and hardness of Ti-6Al-4V, while maintaining ductility and providing new processing insights.