Search Results (1,429)

High-entropy alloys (HEAs) are highly concentrated, multicomponent alloys that have received significant attention due to their superior properties compared to conventional alloys. The mechanical properties and hardness are interrelated, and it is widely known that the hardness of HEAs depends on the principal alloying elements and their composition. Therefore, the desired hardness prediction to develop new HEAs is more interesting. However, the relationship of these compositions with the HEA hardness is very complex and nonlinear. In this study, we develop an artificial neural network (ANN) model using experimental data sets (535). The compositional elements—Al, Co, Cr, Cu, Mn, Ni, Fe, W, Mo, and Ti—are considered input parameters, and hardness is considered as an output parameter. The developed model shows excellent correlation coefficients (Adj R2) of 99.84% and 99.3% for training and testing data sets, respectively. We developed a user-friendly graphical interface for the model. The developed model was used to understand the effect of alloying elements on hardness. It was identified that the Al, Cr, and Mn were found to significantly enhance hardness by promoting the formation and stabilization of BCC and B2 phases, which are inherently harder due to limited active slip systems. In contrast, elements such as Co, Cu, Fe, and Ni led to a reduction in hardness, primarily due to their role in stabilizing the ductile FCC phase. The addition of W markedly increased the hardness by inducing severe lattice distortion and promoting the formation of hard intermetallic compounds. Full article

To address the synergistic degradation mechanisms in engineering service environments, we propose a boron microalloying strategy to enhance the multifunctional surface performance of AlCoCrFeNiMo-based high-entropy alloys. AlCoCrFeNiMoTiBx coatings (x = 0, 0.5, 1, and 1.5) were fabricated on Q235 steel substrates using laser cladding. The microstructure of the coatings was characterized using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), while their wear and corrosion resistance were evaluated through tribological and electrochemical tests. The key findings indicate that boron addition preserves the original body-centered cubic (BCC) and σ phases in the coating while promoting the in situ formation of TiB₂, leading to lattice distortion. With increasing B content, the BCC phase becomes refined, and both the fraction and size of TiB₂ particles increase. Boron incorporation improves the coating’s microhardness and wear resistance, with the highest wear resistance achieved at x = 1, where abrasive and oxidative wear predominate. At lower content (x = 0.5), B enhances the stability of the passive film and thereby improves corrosion resistance. In contrast, excessive formation of large TiB₂ particles introduces defects into the passive film, accelerating its degradation. Full article

This study investigates the production of chromium–manganese ligature by a metallothermic process using complex silicon–aluminum reducing agents. Low-grade chromium and iron–manganese ores from the Kempirsai and Kerege-Tas deposits in Kazakhstan were used as raw materials, while the reducing agents included alumosilicomanganese alloy (AlSiMn) and ferrosilicoaluminum (FeSiAl). Thermodynamic calculations were performed with HSC Chemistry 10 at 1400–1800 °C and reducing agent dosages of 10–100 kg per 100 kg of ore charge. Crucible smelting experiments were then carried out in a Tamman furnace, followed by large-scale laboratory trials in a 100 kVA refining electric furnace to verify reproducibility, with a total of 14 runs. The chemical composition of the ligatures varied depending on the reductant: with AlSiMn the alloy contained Fe—23.14%, Cr—53.74%, Mn—20.03%, and Si—3.06%; with FeSiAl, it contained Fe—42.01%, Cr—25.74%, Mn—27.15%, and Si—5.05%; and with FeSiCr dust, it contained Fe—34.45%, Cr—21.45%, Mn—39.82%, and Si—4.24%. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the presence of α-(Fe,Cr,Mn), FeSi, and Cr₅Si₃ phases. The results demonstrate the efficiency of complex silicon–aluminum reducing agents and the ability to regulate the composition of chromium–manganese ligatures by the selected reductant. Full article

This study focuses on optimizing the machinability of Al-Fe-Cu (8000 series) alloys by developing new compositions with varying Fe and Cu contents and evaluating their mechanical, microstructural, and energy performance. For this purpose, 6061 Al alloy was melted in an induction furnace and cast into molds, and samples containing 2.5% and 5% Fe were produced. Microstructural features were analyzed using Python-based image processing, while Specific Energy Consumption (SEC) theory was applied to assess machining efficiency. An alloy with 2.5% Fe and 2.64% Cu showed superior mechanical properties and the lowest energy consumption. Increasing cutting speed and depth of cut notably decreased SEC. Machine learning (ML) analysis confirmed strong predictive capability, with R² values above 0.80 for all models. Decision Tree (DT) achieved the highest accuracy for SEC prediction (R² = 0.98634, MAE = 0.02209, MSE = 0.00104), whereas XGBoost (XGB) performed best for SCEC (R² = 0.96533, MAE = 0.25578, MSE = 0.10178). Response Surface Methodology (RSM) optimization further validated the significant influence of machining parameters on SEC and specific cutting energy consumption (SCEC). Overall, the integration of machine learning (ML), response surface methodology (RSM), and energy equations provides a comprehensive approach to improve the machinability and energy efficiency of 8000 series alloys, offering practical insights for industrial applications. Full article

Concentrated Solar Power (CSP) technology is advancing toward higher operating temperatures and lower costs: current systems operate at 565 °C, while next-generation systems are targeted to reach 800 °C to overcome efficiency limitations. In this context, low-cost, adaptable molten chloride salts have emerged as ideal heat transfer and thermal energy storage media. Metallic materials are susceptible to performance degradation under such conditions, which not only shortens equipment service life but also entails potential safety hazards. Thus, the development of alloy protection technologies resistant to molten salt corrosion has become an urgent priority for the deployment of next-generation CSP plants. Research has indicated that high-aluminum stainless steel is a promising candidate due to its unique advantages: it can form a stable Al₂O₃ protective film in oxygen-containing anionic environments, effectively inhibiting the dissolution of Cr, Fe, and other elements, and preventing the penetration of corrosive species. Additionally, the incorporation of magnesium-based corrosion inhibitors into MgCl₂-NaCl-KCl ternary molten salt systems has been proven to be an economically viable and efficient corrosion mitigation strategy. This study focused on high-aluminum 310S heat-resistant steel, with its performance validated through targeted experiments: samples subjected to pre-oxidation at 800 °C for 2 h were immersed in a specific ternary molten salt mixture (20.4 wt.% KCl, 55.1 wt.% MgCl₂, 24.5 wt.% NaCl) containing magnesium corrosion inhibitors, followed by a 600 h static corrosion test at 800 °C. The results revealed that the addition of magnesium significantly enhanced the corrosion resistance of high-aluminum 310S. These findings demonstrate that this material holds application potential in the storage tank and pipeline systems of next-generation CSP plants. Full article

Recent literature reports have shown that individual HEAs, especially those of the AlCoCrFeNi composition system alloyed with appropriately selected elements, exhibit excellent mechanical properties and corrosion resistance, making them promising candidates for replacing conventional materials such as austenitic steels in corrosive environments. Therefore, in the present study, the high-entropy alloy AlCoCrFeNiMo_0.25 was examined and compared with AISI 304L steel and the reference alloy AlCoCrFeNi. The HEA was produced by arc melting in vacuum. The effect of molybdenum addition (5% at.) on the structure, mechanical properties, and corrosion resistance was evaluated. Potentiodynamic polarization and electrochemical impedance spectroscopy tests were carried out in a 3.5% NaCl solution in a three-electrode electrochemical system. The addition of molybdenum to AlCoCrFeNiMo_x alloy additionally caused, along with the BCC phase, the formation of σ phase and FCC phase (less than 1%), as well as changes in the microstructure, leading to the fragmentation of grains and the formation of a mosaic structure. On the basis of nanoindentation tests, it was established that the addition of Mo increases hardness and elastic modulus and improves nanoindentation coefficients H/E and H³/E², as well as an increase in the elastic recovery index while decreasing plasticity index (vs. the reference equiatomic HEA). This indicates the improvement of anti-wear properties with impact loading resistance. In turn, electrochemical tests have shown that the addition of Mo improves corrosion resistance. Corrosion pitting develops in Al- and Ni-rich areas of HEA alloys, as a result of galvanic microcorrosion related to Cr chemical segregation. In general, the addition of 5% Mo results in a fine-grained mosaic structure, which primarily translates into favorable nanoindentation and corrosion properties of the AlCoCrFeNiMo_0.25 alloy. Full article

Three variants of high-entropy alloys (HEAs) from the AlCoCuFeNi group, containing different amounts of Al and Cu, were developed and produced via induction melting and casting into ceramic moulds. The ingots were homogenized at 1000 °C for 10 h. Analyses revealed that variations in Al and Cu concentrations led to significant changes in the material’s microstructure, hardness, strength, and impact strength. In the equiatomic variant, differential scanning calorimetry revealed a peak associated with the phase transformation, indicating that this alloy’s microstructure consists of two distinct phases. In contrast, when the concentrations of Al and Cu are reduced, a single-phase microstructure is observed. The equiatomic variant (used as a reference) is characterized by its hardness and brittleness, exhibiting slight ductility, with a tensile strength of 80 MPa, a hardness of 400 HV5, and an impact strength of 1.9 J/cm². However, with adjusted Al contents of 1/2 and Cu contents of 1/4, the alloy displays exceptional strength combined with good plasticity, achieving a tensile strength of up to 450 MPa with 60% elongation, and an impact strength of 215 J/cm². The non-equiatomic variants exhibit a comparatively more straightforward microstructure and enhanced ductility, which may facilitate easier processing of these alloys. Fractography investigation revealed a ductile mode of fracture in the samples. Full article

The novel fibrous composites of Al₆₁Cu₂₇Fe₁₂ alloy with a single-crystalline matrix and quasi-crystal phase fraction obtained in situ by directional solidification by the Bridgman method were studied to characterize the voids and their role in composites cracking. The voids were analyzed using light-optical and scanning electron microscopy to study their nature before and after uniaxial tensile tests. Tension tests were performed on plate-like samples up to rupture. The tensile fracture surfaces were also observed and analyzed. The single-crystallinity and crystalographic parameters of composites were studied using the X-ray Laue diffraction method. It was stated that such new type of composite is characterized by a relatively high void content with a ratio of approximately 2.6%. The composite’s cracking is initiated at voids and progress through the voids and stair steps in the matrix and the reinforcing fibers. Full article

Despite intense interest in the catalytic potential of transition metal oxide heterostructures, originating from their large surface area and tunable chemistry, the fabrication of well-defined multicomponent oxide coatings with controlled architectures remains challenging. Here, we demonstrate a simple and effective swelling-assisted sequential infiltration synthesis (SIS) strategy to fabricate hierarchically porous multicomponent metal-oxide electrocatalysts with tunable bimetallic composition. A combination of solution-based infiltration (SBI) of transition metals, iron (Fe), nickel (Ni), and cobalt (Co), into a block copolymer (PS73-b-P4VP28) template, followed by vapor-phase infiltration of alumina using sequential infiltration synthesis (SIS), was employed to synthesize porous, robust, conformal and transparent multicomponent metal-oxide coatings like Fe/AlO_x, Fe+Ni/AlO_x, and Fe+Co/AlO_x. Electrochemical assessments for the oxygen evolution reaction (OER) in a 0.1 M KOH electrolyte demonstrated that the Fe+Ni/AlO_x composite exhibited markedly superior catalytic activity, achieving an impressive onset potential of 1.41 V and a peak current density of 3.29 mA/cm². This superior activity reflects the well-known synergistic effect of alloying transition metals with a trace of Fe, which facilitates OER kinetics. Overall, our approach offers a versatile and scalable path towards the design of stable and efficient catalysts with tunable nanostructures, opening new possibilities for a wide range of electrochemical energy applications. Full article

Aircraft engine turbine discs operate under extreme conditions that limit their service life. Laser cladding of AlCoCrFeNi HEA coatings presents a viable solution to enhance their durability. This study optimizes the laser cladding process parameters—specifically, laser power, scanning speed, and powder feed rate—using the Taguchi method in conjunction with grey relational analysis. The optimal parameter set (1450 W, 480 mm/min, 4 r/min) resulted in a coating with a width of 2.93 mm, a height of 1.20 mm, a dilution rate of 22.6%, and a hardness of 532 HV. The optimized process significantly improved hardness by approximately 15% while reducing dilution and elemental segregation in comparison to the initial parameters. This research illustrates the effectiveness of multi-objective optimization in enhancing coating performance, providing a practical approach for the surface strengthening of critical components, such as turbine discs in aircraft engines, under extreme conditions. Full article

The increasing adoption of High-Pressure Die Casting (HPDC) technology in the production of automotive body structure components is driven by its potential for efficiency and performance. This technology, however, involves complex physical phenomena with numerous parameters that significantly influence casting quality. In this study, three key die casting parameters—plunger or shot speed, vacuum application, and intensification pressure (IP)—have been evaluated following a Design of Experiment (DoE) approach. The results demonstrate that IP application is instrumental in reducing porosity within the cast specimens, thereby enhancing their mechanical strength and elongation. Furthermore, the combined application of vacuum and IP yields further improvements in elongation by minimizing porosity. These findings are particularly relevant for silicon-free alloys, which eliminate the need for post-casting heat treatments to achieve the required mechanical properties. By optimizing HPDC processes, manufacturers can reduce rejection rates, lower production costs, and improve the overall efficiency of their operations, contributing to the production of high-quality and cost-effective components for the automotive industry. Full article

The increase in electrification and desire for greater electrical motor efficiency under a range of operating conditions for different products (e.g., household appliances, automotive and aerospace) is driving innovative motor designs and demands for higher performing electrical steels. Improvements in the magnetic, electrical and/or mechanical properties of electrical steels are required for high-volume electric motors and recent advances include steels with increased silicon (Si) content (from <3.5 wt% Si up to 6.5 wt%). Whilst the 6.5 wt% Si steels provide increased motor performance at high frequencies, the formation of a brittle BCC B2/D03 phase means that they cannot be cold-rolled, and therefore the production route involves siliconization after the required thickness strip is produced. The advances in computationally driven alloy design, coupled with physical metallurgical understanding, allow for more adventurous alloy design for electrical steels, outside the traditional predominantly Fe-Si compositional space. Two alloys representing a new alloy family called HiPPES (High-Performing and Processable Electrical Steel), based on low cost commonly used steel alloying elements, have been developed, cast, rolled, heat-treated, and both magnetically and mechanically tested. These alloys (with nominal compositions of Fe-3.2Mn-3.61Si-0.63Ni-0.75Cr-0.15Al-0.4Mo and Fe-2Mn-4.5Si-0.4Ni-0.75Cr-0.09Al) offer improvements compared to current ≈3 wt% Si grades: in magnetic performance (>25% magnetic loss reduction at >1 kHz), and in tensile strength (>33% increase in tensile strength with similar elongation value). Most importantly, they are maintaining processability to allow for full-scale commercial production using traditional continuous casting, hot and cold rolling, and annealing. The new alloys also showed improved resilience to grain size, with the HiPPES materials showing a <5% variance in loss at frequencies greater than 400 Hz for grain sizes between 55 and 180 µm. Comparatively, a commercial M250-35A material showed a 40% increase in loss for the same range. The paper reports on the alloy design approach used, the microstructures, and the mechanical, electrical and magnetic properties of the developed novel electrical steels compared to conventional ≈3 wt% Si and 6.5 wt% Si material. Full article

High-pressure die casting (HPDC) is a highly efficient method for producing aluminum parts that require high dimensional accuracy and complex shapes. However, the quality of the resulting castings, specifically their porosity and microstructure, is critically dependent on the setting of process parameters. Any deficiencies in these aspects can lead to a significant reduction in the mechanical properties of the components. This article deals with the influence of plunger speed during high-pressure die casting on microstructure homogeneity and the occurrence of porosity in critical areas of AlSi9Cu3(Fe) alloy castings. Numerical simulations and experimental evaluation demonstrated that with increasing plunger speed, there is a transition from a transitional to a laminar flow regime to a fully turbulent regime, which affects the homogeneity of the alloy and its solidification. Turbulent flow minimizes shrinkage porosity in castings but increases the risk of gas porosity and oxide inclusions due to reoxidation processes, leading to the entrainment of air and oxide layers. Microporosity analysis showed that the lowest occurrence of shrinkage-type pores was found at a plunger speed of 4 m/s due to rapid filling and shorter solidification time. The optimal plunger speed range is between 3 and 3.6 m/s, ensuring a compromise between microstructure stability and minimization of porosity in critical areas. Full article

The (AlFeCoNi)C high-entropy alloy carbide films (HECFs) with tunable carbon contents were fabricated by magnetron sputtering to investigate the carbon-driven structural evolution and its coupling effects on mechanical and chemical properties. With increasing carbon incorporation (0–47.6 at.%), the HECFs formed a composite structure of amorphous phase and BCC nanocrystalline phase, as evidenced by XRD and TEM. Atom probe tomography (APT) reveals Al segregation in the film. Remarkably, the wear rate decreases exponentially from 4.8 × 10⁻⁵ to 6.7 × 10⁻⁶ mm³/N·m, attributed to the amorphous carbon phase acting as solid lubricant. Simultaneously, the corrosion current density reduces by two orders of magnitude (7.2 × 10⁻⁸ A/cm² in 3.5% NaCl), benefiting from the amorphous network inhibiting ion diffusion pathways. This work establishes a carbon-content–property correlation paradigm for designing multifunctional HEA films in extreme environments. Full article

In this study, the newly developed Ti35421 (Ti3Al5Mo4Cr2Zr1Fe wt.%) alloy was prepared by laser directed energy deposition (L-DED) because it contains several major elements that can refine grains, which is expected to enable the transformation from columnar to equiaxed grains. The results show that the L-DED Ti35421 alloy is predominantly composed of equiaxed grains and features various α-phase morphologies, including grain boundary α, lath α, and acicular α′ structures. These microstructural features are attributed to the rapid cooling conditions during processing. Such a microstructure enhances the alloy’s tensile strength (1446 MPa) while leading to limited ductility (1.7%). Following the solution and aging treatment, the grain boundary α phase undergoes coarsening, while the matrix β phase transforms into numerous fine lamellar α phases. This leads to a reduction in strength but an improvement in ductility. Therefore, the optimal heat treatment process for the L-DED Ti35421 alloy is determined to be a two-stage procedure: first, heating at 780 °C for 2 h followed by air cooling, and subsequently heating at 575 °C for 8 h with air cooling. Under this treatment, the alloy exhibits excellent mechanical properties, including a tensile strength of 1196 MPa, a yield strength of 1162 MPa, an elongation of 6.8%, and a reduction in area of 16.7%. Since there are no continuous grain boundaries in α, the rolled Ti35421 alloy exhibits better ductility than the L-DED Ti35421 alloy. This article is a revised and expanded version of a poster presentation entitled “Microstructure and mechanical properties of Ti-3Al-5Mo-4Cr-2Zr-1Fe alloy fabricated by laser deposition manufacturing”, which was accepted and presented at the 15th World Conference on Titanium (Ti-2023), Edinburgh, UK, 12–16 June 2023. Full article