Search Results (151)

As a new type of alloy system composed of five or more principal components, high-entropy alloys demonstrate outstanding comprehensive performance in the field of friction and wear through the synergistic effects of the high-entropy effect, lattice distortion effect, hysteresis diffusion effect and cocktail effect. This paper systematically reviews the research progress on the friction and wear properties of high-entropy alloys. The mechanisms of metal elements such as Al, Ti, Cu and Nb through solid solution strengthening, second-phase precipitation and oxide film formation were analyzed emphatically. And non-metallic elements such as C, Si, and B form and strengthen the regulation laws of their tribological properties. The influence of working conditions, such as high temperature, ocean, and hydrogen peroxide on the friction and wear behavior of high-entropy alloys by altering the wear mechanism, was discussed. The influence of test conditions such as load, sliding velocity and friction pair matching on its friction coefficient and wear rate was expounded. It is pointed out that high-entropy alloys have significant application potential in key friction components, providing reference and guidance for the further development and application of high-entropy alloys. Full article

By introducing oxygen doping, the structure of an AlCrNbSiTiN coating was optimized, and its high-temperature oxidation resistance was improved. As the oxygen content incorporated increases, the coating changes from an FCC structure to an amorphous or spinel structure. Meanwhile, stress relaxation occurred, and the hardness of the coating dropped to 12 gpa. Oxygen-doped coatings exhibit excellent oxidation resistance; this is especially the case for oxidized coatings, whose structure remains stable up to 900 °C in an oxidizing environment. Full article

High-entropy alloys (HEAs) represent a breakthrough class of materials characterized by a unique combination of properties derived from their multielement compositions. This review explores the current advancements in both electrochemical and electroless deposition techniques for synthesizing HEA thin films. This paper discusses the crucial plating conditions using aqueous or organic electrolytes and various current/potential modes that influence the formation, quality, and properties of these complex alloy coatings. Particular attention is given to their emerging applications in areas such as catalysis, protective coatings, microelectronics, and liquids’ separation. A comparison of electrochemical versus electroless methods reveals insights into the advantages and limitations of each technique for research and industrial use. This comprehensive review aims to guide further innovation in the development and application of HEA coatings. Full article

Deep learning models have obvious advantages in detecting oil spills, but the training of deep learning models heavily depends on a large number of samples of high quality. However, due to the accidental nature, unpredictability, and urgency of oil spill incidents, it is difficult to obtain a large number of labeled samples in real oil spill monitoring scenarios. Surprisingly, few-shot learning can achieve excellent classification performance with only a small number of labeled samples. In this context, a new cross-domain few-shot SAR oil spill detection network is proposed in this paper. Significantly, the network is embedded with a hybrid attention feature extraction block, which consists of a coordinate attention module to perceive the channel information and spatial location information, as well as a global self-attention transformer module capturing the global dependencies and a multi-scale self-attention module depicting the local detailed features, thereby achieving deep mining and accurate characterization of image features. In addition, to address the problem that it is difficult to distinguish between the suspected oil film in seawater and real oil film using few-shot due to the small difference in features, this paper proposes a double loss function category determination block, which consists of two parts: a well-designed category-perception loss function and a traditional cross-entropy loss function. The category-perception loss function optimizes the spatial distribution of sample features by shortening the distance between similar samples while expanding the distance between different samples. By combining the category-perception loss function with the cross-entropy loss function, the network’s performance in discriminating between real and suspected oil films is thus maximized. The experimental results effectively demonstrate that this study provides an effective solution for high-precision oil spill detection under few-shot conditions, which is conducive to the rapid identification of oil spill accidents. Full article

This study examines the corrosion characteristics of GRX-810, a NiCoCr-based high entropy alloy, in a simulated marine environment represented by 3.5 wt.% NaCl solution. The research employs electrochemical and surface analysis techniques to evaluate the corrosion performance and protective mechanisms of this alloy. Electrochemical characterization was performed using potentiodynamic polarization to determine critical corrosion parameters, including corrosion potential and current density, along with electrochemical impedance spectroscopy to assess the stability and protective qualities of the oxide film. Surface analytical techniques provided detailed microstructural and compositional insights, with scanning electron microscopy revealing the morphology of corrosion products, energy-dispersive X-ray spectroscopy identifying elemental distribution in the passive layer, and X-ray diffraction confirming the chemical composition and crystalline structure of surface oxide. The results demonstrated distinct corrosion resistance behavior between the different processing conditions of the alloy. The laser powder bed fused (LPBF) specimens in the as-built condition exhibited superior corrosion resistance compared to their hot isostatically pressed (HIPed) counterparts, as evidenced by higher corrosion potentials and lower current densities. Microscopic examination revealed the formation of a dense, continuous layer of corrosion products on the alloy surface, indicating effective barrier protection against chloride ion penetration. A compositional analysis of all samples identified oxide film enriched with chromium, nickel, cobalt, aluminum, titanium, and silicon. XRD characterization confirmed the presence of chromium oxide (Cr₂O₃) as the primary protective phase, with additional oxides contributing to the stability of the film. This oxide mixture demonstrated the alloy’s ability to maintain passivity and effective repassivation following film breakdown. Full article

Based on their high mechanical strength, Ti-based high-entropy alloys (HEAs) are of great potential as materials for high-performance reduced-diameter dental implants. Despite previous studies demonstrating their corrosion resistance in various simulated body fluids, their resistance in simulated buccal conditions has yet to be confirmed. In this work, the corrosion behavior of two Ti-based HEAs, TiZrHfNb, and TiZrHfNbTa was evaluated in comparison to CP-Ti and Ti-6Al-4V in artificial saliva (AS) solution and in AS with fluoride ion content (ASF). A set of electrochemical tests (electrochemical impedance spectroscopy, cyclic polarization, and Mott–Schottky) was employed and complemented with surface characterization analyses (scanning electron microscopy and atomic force microscopy) to determine dissolution and passivation mechanisms of the alloys. In general, the HEAs exhibited a far superior corrosion resistance compared to CP-Ti and Ti-6Al-4V alloys in both solutions. In the AS solution, the TiZrHfNb exhibited the highest polarization resistance and pitting potential, indicating a high corrosion resistance due to the formation of a robust passive layer. Whilst in the ASF solution, the TiZrHfNbTa showed a greater corrosion resistance due to the synergistic effect of Nb and Ta oxides that enhanced passive film stability. This finding emphasizes the role of Ta in elevating the corrosion resistance of Ti-based HEAs in the presence of fluoride ions and confirms the importance of chemical composition optimization in the development of next-generation dental alloys. Based on its electrochemical corrosion behavior, TiZrHfNbTa HEAs are promising new materials for high-performance reduced-diameter dental implants. Full article

This paper studies how heat treatments influence the corrosion of an AlCoCrFeNi_2.1 eutectic high-entropy alloy (EHEA) in a 3.5 wt% NaCl solution, by comparing the corrosion behaviors of as-cast, 600 °C heat-treated, and 1000 °C heat-treated samples using microstructure characterization, electrochemical measurements, and surface characterization. The electrochemical results show that the pitting potential rises and the passive current density and passive film resistance are almost changeless with an increasing heat treatment temperature. The enhancement in the pitting corrosion resistance results from the increased amount of the Cr-rich FCC phase and decreased amount of the B2 phase rich in the Al element, which are induced by the heat treatment. On one hand, this microstructure evolution can make the passive film have more Cr₂O₃ and less Al₂O₃, thereby enhancing its protective properties, as confirmed by the X-ray photoelectron spectroscopy analysis. On the other hand, the decreased amount of the Al-rich B2 phase can make the pitting corrosion less prone to initiate since the B2 phase can act as the pit initiation site, which is supported by the observation of corrosion morphologies, due to its higher electrochemical activity. In a summary, the heat treatment is beneficial for improving the pitting corrosion resistance of the AlCoCrFeNi_2.1 EHEA. Full article

(AlTiV)_100−xCr_x high-entropy alloys (HEAs) is expected to solve the problem of poor corrosion-wear resistance of lightweight alloys. To elucidate its corrosion-wear mechanism, three (AlTiV)_100−xCr_x alloys were prepared by vacuum arc melting method by repeating the melting five times at 240 A current.and their microstructures, mechanics, corrosion, wear, and corrosion-wear behaviors were investigated. The results indicate that (AlTiV)_100−xCr_x is a single-phase with BCC structure and the VEC of Cr5, Cr10 and Cr15 were 4.0, 4.1 and 4.2 respectively. Their hardness increase and toughness and corrosion resistance decrease with the increase of Cr content (Cr5:537.5 HV_0.2/6.7%/1.86 × 10⁻⁸ A/cm²; Cr10:572.3 HV_0.2/5.6%/2.09 × 10⁸ A/cm²; Cr15:617.6 HV_0.2/3.8%/2.51 × 10⁻⁸ A/cm²). The wear volume and the corrosion-wear volume of AlTiVCr alloys are mainly caused by the abrasive wear. However, the fatigue wear of AlTiVCr alloys could be exacerbated by a decrease in material’s toughness, corrosion resistance, and an increase in solution corrosivity. Therefore, Cr10 presents the optimal wear resistance in the deionized water, while the optimal corrosion-wear resistance in the 3.5 wt.% NaCl solution is presented by Cr5. Compared to TC4, the wear and corrosion-wear resistance were improved by 56.4% and 65.5%, respectively. Full article

This work studies the fabrication of CoCrFeNiMo high-entropy alloy (HEA) coatings via coaxial powder-fed laser cladding, addressing porosity and impurity issues in conventional methods. The HEA coatings exhibited eutectic/hypereutectic microstructures under all laser power conditions. A systematic investigation of laser power effects (1750–2500 W) reveals that 2250 W optimizes microstructure and performance, yielding a dual-phase structure with FCC matrix and dispersed σ phases (Fe-Cr/Mo-rich). The coating achieves exceptional hardness (738.3 HV_0.2, 3.8× substrate), ultralow wear rate (4.55 × 10⁻⁵ mm³/N·m), and minimized corrosion current (2.31 × 10⁻⁴ A/cm²) in 3.5 wt.% NaCl. The friction mechanism of the CoCrFeNiMo HEA coating is that in high-speed friction and wear, the oxide film is formed on the surface of the coating, and then the rupture of the oxide film leads to adhesive wear and abrasive wear. The corrosion mechanism is the galvanic corrosion caused by the potential difference between the FCC phase and the σ phase. Full article

The gas-liquid sulfonation of α-olefin sulfonate (AOS) in falling film reactors faces significant limitations, primarily due to poor mass transfer efficiency and excessive byproduct formation. To overcome these challenges, a novel cross-shaped microchannel reactor was developed for the continuous gas-liquid sulfonation of α-olefin (AO) with gaseous sulfur trioxide (SO₃). The influence of key process parameters, including gas-phase flow rate, reaction temperature, SO₃/AO molar ratio, and SO₃ volume fraction, on product characteristics and their interactions was systematically investigated using the single-factor experiment and response surface methodology (RSM). A high-precision empirical model (coefficient of determination, R² = 0.9882) to predict product content was successfully constructed. To achieve multi-objective optimization considering product active substance content and energy efficiency, a strategy combining a two-population genetic algorithm with the entropy-weighted TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) method was implemented. Optimal conditions were determined as follows: gas-phase flow rate of 228 mL/min, reaction temperature of 52 °C, SO₃/AO molar ratio of 1.27, and SO₃ volume fraction of 4%. Compared to conditions optimized solely by RSM, this multi-objective approach achieved a significant 10% reduction in energy efficiency, with only a marginal 3.8% decrease in active substance content. This study demonstrates the feasibility and advantages of microreactors for the efficient and green synthesis of AOS. Full article

CoCrFeNiMn high-entropy alloy (HEA) composite coatings with 0, 10, and 20 wt% TiC are synthesized through laser cladding technology, and their corrosion and wear resistance are systematically investigated. The X-ray diffraction (XRD) results show that with the addition of TiC, the phases of TiC and M₂₃C₆ are introduced, and lattice distortion occurs simultaneously (accompanied by the broadening and leftward shift of the main Face-Centered Cubic (FCC) peak). Scanning electron microscopy (SEM) reveals that the incompletely melted TiC particles in the coating (S2) are uniformly distributed in the matrix with 20 wt% TiC, while in the coating (S1) with 10 wt% TiC, due to gravitational sedimentation and decomposition during laser processing, the distribution of the reinforcing phase is insufficient. When rubbed against Si₃N₄, with the addition of TiC, S2 exhibits the lowest friction coefficient of 0.699 and wear volume of 0.0398 mm³. The corrosion resistance of S2 is more prominent in the simulated seawater (3.5 wt% NaCl). S2 shows the best corrosion resistance: it has the largest self-corrosion voltage (−0.425 V vs. SCE), the lowest self-corrosion current density (1.119 × 10⁻⁷ A/cm²), and exhibits stable passivation behavior with a wide passivation region. Electrochemical impedance spectroscopy (EIS) confirms that its passivation film is denser. This study shows that the addition of 20 wt% TiC optimizes the microstructural homogeneity and synergistically enhances the mechanical strengthening and electrochemical stability of the coating, providing a new strategy for the making of HEA-based layers in harsh wear-corrosion coupling environments. Full article

High-entropy silicide (MeSi₂) coating was prepared by the slurry method and silicon infiltration method using Mo, Cr, Ta, Nb, W, and Si elemental powders as raw materials. The coating consisted of four layers, including a porous MeSi₂ layer, a (CrTa)Si layer, a TaSi₂ layer, and a Ta₅Si₃ layer from outside to inside. At 600 °C, Si was preferentially oxidized to form SiO₂ oxide film. The mass gain rate of the coating was 0.2 mg/cm² over a period of 100 h oxidation, eliminating the phenomenon of low-temperature pulverization. At 1200 °C, MeSi₂ coating had a protection time of 20 h. During the oxidation process, the coating generated metal oxides, forming a thin SiO₂ oxide film. TaSi₂ and Ta₅Si₃ gradually transformed into Ta₂O₅, and the coating eventually failed. Full article

In this study, FeCoNiCrAl high-entropy alloy (HEA) coatings were fabricated on Q235 steel surfaces using laser cladding (LC) to enhance corrosion resistance in harsh environments. The laser processing parameters (laser power, defocus distance, and scanning speed) were optimized using response surface methodology (RSM), establishing a mathematical model to guide the process. The optimized coatings demonstrated strong metallurgical bonding to the substrate, with a microstructure comprising Al-Ni-rich B2 phases and Cr-Fe-rich BCC phases. Elemental segregation was effectively mitigated as energy density decreased, leading to significant improvements in corrosion resistance. Electrochemical tests in 3.5 wt.% NaCl and 0.5 mol/L H₂SO₄ solutions showed that the optimized coating (laser power: 800 W, scanning speed: 450 mm/min, defocus: −15 mm) exhibited exceptionally low corrosion current densities of 1.78 × 10⁻⁷ A/cm² and 1.07 × 10⁻⁵ A/cm², respectively. The passive film on the optimized coating surface consisted of stable oxides, with low oxygen vacancy densities of 1.937 × 10²³ cm⁻³ in NaCl and 4.967 × 10²¹ cm⁻³ in H₂SO₄, significantly enhancing its resistance to localized and uniform corrosion. These results demonstrate the effectiveness of RSM-based optimization in producing HEA coatings with superior corrosion resistance suitable for applications in highly corrosive environments. Full article

This study examines the microstructure and corrosion resistance of FeCrNiAl_0.7Cu_0.3Si_x (x = 0, 0.1, 0.3, and 0.5) high-entropy alloys (HEAs) in a 3.5% NaCl solution. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electrochemical testing were employed to systematically analyze the alloys’ microstructures and corrosion behavior. The XRD results indicate that the addition of Si affects the phase structure of the alloy. At Si = 0, the alloy exhibits a single BCC phase. By increasing the Si content to 0.1 and 0.3, a BCC₂ phase appears. At Si = 0.5, Si-containing intermetallic compounds form. SEM observations reveal that as the Si content increases, the alloy develops a distinct dendritic structure. Polarization tests in the 3.5% NaCl solution show that the corrosion current density first decreases and then increases with increasing Si content. At Si contents of 0.1, 0.3, and 0.5, the corrosion current densities are 4.275 × 10⁻⁶ A·cm⁻², 4.841 × 10⁻⁷ A·cm⁻², and 2.137 × 10⁻⁶ A·cm⁻², respectively. FeCrNiAl_0.7Cu_0.3S_0.3 HEA exhibits the lowest corrosion current density, indicating a lower corrosion rate. Electrochemical impedance spectroscopy (EIS) tests show that at Si = 0.3, the alloy has the largest capacitive arc radius. The charge-transfer resistance (RCT) for the alloys with the Si contents of 0.1, 0.3, and 0.5 are 2.532 × 10⁵ Ω·cm², 4.088 × 10⁵ Ω·cm², 4.484 × 10⁵ Ω·cm², and 2.083 × 10⁵ Ω·cm², respectively. FeCrNiAl_0.7Cu_0.3Si_0.3 HEA has the highest RCT, which indicates a more stable passivation film and better resistance to chloride ion intrusion. The corrosion morphology observed after polarization testing shows that all alloys exhibit intergranular corrosion characteristics. The Si content alters the distribution of passivation film-forming elements, Cr and Ni. Compared to other alloys, the corrosion morphology of FeCrNiAl_0.7Cu_0.3Si_0.3 HEA is more complete. Combining the polarization, EIS, and corrosion morphology results, it can be concluded that FeCrNiAl_0.7Cu_0.3Si_0.3 HEA exhibits the best corrosion resistance in the 3.5% NaCl solution. Full article

The corrosion characteristics and passive behavior of as-cast Ni₄₀Fe₃₀Co₂₀Al₁₀ medium-entropy alloy (MEA) fabricated by the vacuum arc melting technique were investigated in 3.5 wt.% NaCl, 0.5 M HCl, and 0.5 M H₂SO₄ solutions. Although the impact of different solutions on the corrosion current density was not pronounced, the corrosion potential values of MEAs in H₂SO₄, HCl and NaCl solutions were −0.37, −0.58 and −1.16 V, respectively, indicating that the resistance to general corrosion in acidic solutions becomes strengthened. Through electrochemical passive region tests, surface morphology analysis and ICP testing, it was found that, due to the high-entropy effect and uniform single-phase structure, an optimized and stable passive film formed specifically in the Cl⁻-containing solution. The ion concentrations in the passive region of MEA in NaCl solution were an order of magnitude lower than those of other two samples, suggesting that its passive film formed exhibits a more prominent capacity to inhibit metal dissolution. Compared with electrochemical reactions in H₂SO₄ and HCl solutions, MEA shows enhanced pitting resistance in NaCl solution, which could be attributed to the presence of abundant unoxidized metal atoms (51.9 at.%). Al is identified as the primary component in the formation of the passive film, which plays a protective role for the Co-rich interior of the MEA. Although MEA has a relatively high passivation current in the H₂SO₄ solution, it has the widest passivation zone (1.87 V), indicating the optimized stability of the formed passive film. Moreover, it displays a high level of resistance to pitting corrosion in the solution containing only H⁺- and free of Cl⁻. Both the MEAs show significant grain-boundary corrosion in H₂SO₄ and HCl solutions. Among them, the MEA in HCl experiences more severe intragranular corrosion. Notably, MEA withstands the erosion of a single Cl⁻- or H⁺-containing solution, but it is unable to resist the synergistic effect of a solution containing both H⁺ and Cl⁻. Full article