Search Results (1,433)

This study investigates the fabrication of a Cu-Mn-Al alloy coating on 27SiMn steel using Cold Metal Transfer (CMT) technology with an innovative Ar-B(OCH₃)₃ mixed shielding gas, focusing on the effect of the gas flow rate (5–20 L/min). The addition of B(OCH₃)₃ was found to significantly enhance process stability by improving molten pool wettability, resulting in a wider cladding layer (6.565 mm) and smaller wetting angles compared to pure Ar. Macro-morphology analysis identified 10 L/min as the optimal flow rate for achieving a uniform and defect-free coating, while deviations led to oxidation (at low flow) or spatter and turbulence (at high flow). Microstructural characterization revealed that the flow rate critically governs phase evolution, with the primary κI phase transforming from dendritic/granular to petal-like/rod-like morphologies. At higher flow rates (≥15 L/min), increased stirring promoted Fe dilution from the substrate, leading to the formation of Fe-rich intermetallic compounds and distinct spherical Fe phases. Consequently, the cladding layer obtained at 10 L/min exhibited balanced and superior properties, achieving a maximum shear strength of 303.22 MPa and optimal corrosion resistance with a minimum corrosion rate of 0.02935 mm/y. All shear fractures occurred within the cladding layer, demonstrating superior interfacial bonding strength and ductile fracture characteristics. This work provides a systematic guideline for optimizing shielding gas parameters in the CMT cladding of high-performance Cu-Mn-Al alloy coatings. Full article

Phase transformations significantly influence the mechanical properties of Fe-based alloys, making their understanding essential for the design of high-performance alloy materials. This study investigates microstructural evolution and martensitic transformations induced by B2 phase precipitation in an Fe-20Ni-4.5Al-1.0C (wt.%) alloy. The alloy was solution-treated at 1100 °C, followed by isothermal holding between 750 °C and 1000 °C, and water quenching. Microstructural analysis revealed that the as-quenched alloy consisted of a single-phase austenite (γ). Isothermal holding led to the precipitation of a (Ni,Al)-rich B2 phase within the grains and along grain boundaries. An α′-martensitic phase was also observed within γ-grains adjacent to the B2 precipitates in the isothermally held samples. Martensitic transformation is attributed to localized nickel depletion in the matrix surrounding B2, which reduced γ-phase stability and raised the martensite start temperature (Ms), promoting γ-to-α′ transformation during cooling. The co-existence of B2 and α′ phases significantly increased the hardness of the alloy, with a maximum observed at an 850 °C holding temperature. At higher temperatures, coarsening and partial dissolution of B2, as well reduced martensite formation, led to a decline in hardness. These findings highlight the role of B2 precipitation in promoting martensitic transformation and optimizing mechanical properties through controlled heat treatment. Full article

Titanium and, in particular, its alloys are widely used in biomedical applications due to their favorable combination of mechanical properties, such as high strength, low density, low elastic modulus, and excellent biocompatibility. In this study, novel titanium-based alloys were developed using powder metallurgy techniques. The chemical composition of the studied alloys was 93%Ti-7%Fe, 90%Ti-7%Fe-3%Al, and 88%Ti-7%Fe-5%Cr. The metallic powders were processed in a planetary mill, uniaxially compacted, and subsequently sintered at 1300 °C during 2 h under an inert atmosphere. The primary objective was to evaluate the corrosion behavior of these alloys in simulated body fluid solutions, as well as to determine some of the properties, such as the relative density, microhardness, and elastic modulus. The resulting microstructures were homogeneous, with micrometer-scale grain sizes and the formation of intermetallic precipitates generated during sintering. Mechanical tests revealed that the Ti-Fe-Cr alloy exhibited the highest microhardness and Young’s modulus values, followed by Ti-Fe and Ti-Fe-Al. These results confirm a strong correlation between hardness and stiffness, showing that Cr enhances mechanical and elastic properties, while Al reduces them. Corrosion tests demonstrated that the alloys possess high resistance and stability in physiological environments, with a low current density, minimal mass loss, and strong performance even under prolonged exposure to acidic conditions. Full article

A Y-doped AlCoCrFeNi_2.1 eutectic high-entropy alloy was fabricated via powder bed fusion-laser melting/metal (PBF-LB/M), and the effects of the rare-earth element Y on its microstructure and mechanical properties were investigated. The results indicate that Y addition preserves the fine eutectic microstructure inherent to the PBF-LB/M process, while inducing lattice distortion within the face-centered cubic (FCC) matrix and promoting grain refinement. During solidification, Y facilitates heterogeneous nucleation and, due to its strong affinity with Al, increases both the volume fraction of the body-centered cubic (BCC) phase and the proportion of high-angle grain boundaries. X-ray diffraction (XRD) analysis further confirms that Y suppresses the formation of the ordered B2 phase. Tensile testing reveals that Y doping improves the tensile strength from 1383 MPa to 1475 MPa and enhances the elongation from 13.0% to 16.3%. Fractography shows a transition from quasi-cleavage to ductile fracture mode, indicating that Y significantly enhances the strength–ductility synergy of the alloy. Full article

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