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The reliable connection between ceramics and metals achieved through brazing is a crucial method to promote their application. In this study, the FeCoCrNi high entropy alloys was adopted as the filler to connect SiC and Mo through vacuum brazing. The microstructure evolution and mechanical properties of the SiC/FeCoCrNi/Mo brazed joint at different brazing temperature and holding time were systematically investigated. With the increase of the brazing temperature or the extension of the holding time, the reaction layer gradually thickened with the increasing precipitation of the soft FCC phase. Notably, the FCC solid solution phase with good plastic deformation ability and the brittle Cr 0.46 Mo 0.4 Si 0.14 phase have good interface bonding (lattice mismatch degree ∼ 3.12 %). The dispersive and staggered distribution of FCC phase and Cr 0.46 Mo 0.4 Si 0.14 phase can effectively alleviate the joint stress and hinder crack propagation. This work is expected to provide theoretical guidance for the connection of ceramics and metals through high-entropy alloys. [ABSTRACT FROM AUTHOR]

One-step (F100) and three-step (F30-60-40) hot forging of Al0.35CoCrFeNi alloy was investigated to achieve a uniform equiaxed grain structure. In the as-cast and forged state, only a single-phase face-centered cubic structure was observed. The formation of twins, recrystallized and partially recrystallized grains in the volume of the samples was observed depending on used forging process. To predict uniform grain-size formation numerical simulation of the hot-forging process was used. The numerical model was calibrated and validated by means of measured compression experimental data of as-cast Al0.35CoCrFeNi alloy before forging. Thermal analysis using finite element analysis was used to simulate cooling of sample during the relocation from the furnace on the lower die. Simulations were run under different thermo-mechanical conditions and the regions for the formation of dynamically recrystallized grains were predicted. Room temperature mechanical properties were evaluated after F100 and F30-60-40 hot-forging process. The F30-60-40 hot forging optimized the grain size, which was evident in the very small dispersion of the room temperature mechanical properties in tension. Elongation after F30-60-40 hot forging increased by 17%. The correlation between temperature, equivalent stress, equivalent plastic strain, microstructure, tensile properties, and strain-hardening behavior is discussed. [ABSTRACT FROM AUTHOR]

Constructing bioinspired architectures in metallic materials is an effective way to overcome the inherent strength and plasticity trade-off dilemma. However, conventional processing approaches are difficult to finely tailor the microstructures and mechanical properties of bioinspired architectures. Here, using laser remelting technology, we finely and controllably fabricate three sophisticated bioinspired architectures in a high-entropy alloy (HEA). The bioinspired HEA with brick-and-mortar architecture shows an excellent yield strength of ∼520 MPa with a large uniform elongation of ∼35%. Such enhanced strength-plasticity synergy is mainly attributed to the hetero-deformation between the hard and soft regions of bioinspired architectures. [ABSTRACT FROM AUTHOR]

Developing efficient oxygen electrocatalysts with low cost, high catalytic activity, and robust stability remains a formidable challenge for rechargeable zinc–air batteries (ZABs). Herein, highly dispersed ultrasmall PtPdFeCoNi high‐entropy alloy nanoparticles with a size of ≈ 2 nm and randomly distributed multimetallic single atoms spatially immobilized on the 3D hierarchically ordered porous nitrogen‐doped carbon skeleton (denoted as PtPdFeCoNi/HOPNC) are successfully synthesized via ultra‐rapid Joule heating process. The spatial immobilization on 3D HOPNC skeleton is the key to the high dispersion of multi‐active sites of oxygen electrocatalysts, and the formed hierarchical pore structure is conducive to the successful construction of the rapid mass transfer channel. As a result, the as‐prepared PtPdFeCoNi/HOPNC exhibits a positive half‐wave potential of 0.866 V versus RHE for oxygen reduction reaction (ORR), a low overpotential of 310 mV at 10 mA cm−2 for oxygen evolution reaction (OER), and low Tafel slopes for both ORR and OER. Furthermore, ZAB using PtPdFeCoNi/HOPNC as bifunctional oxygen catalysts exhibits excellent rate performances and superior cycling stability, surpassing that of a commercial Pt/C‐RuO2 mixture. The spatial immobilization strategy of HOPNC provides a new idea for the design and synthesis of efficient catalysts for various applications. [ABSTRACT FROM AUTHOR]

Developing cost-efficient catalysts with high efficiency for water splitting has been considered as large challenge. Herein, the bulk high entropy alloys (HEAs) are fabricated through the vacuum induction melting, which could be beneficial to solving the above issues. At the same time, it also enhances the electrocatalysts activity and stability. The alloy composition is discovered to be crucial in the both hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) activity enhancements with the CoCrFeNiAlMo bulk HEA catalyst combination providing the exceptional catalytic activities. Forming the CoCrFeNiAlMo bulk HEA catalyst also significantly promotes the electrocatalytic cycling stabilities. Hence, the CoCrFeNiAlMo bulk HEA catalyst displays a small overpotential (261 mV @ 50 mA cm−2) and a corresponding Tafel slope (48.66 mV dec−1) for the OER in a 1.0 M KOH electrolyte. For HER, CoCrFeNiAlMo bulk HEA catalyst also possess a relatively small overpotential. Furthermore, it exhibits a relatively small cell voltage of 1.83 V at 50 mA cm−2 and superior durable for 14 h. This study presents a universal pathway for preparing sustainable high efficiency electrocatalysts, it demonstrates that the bulk HEAs have the potential to be effective catalysts in alkaline environments. [Display omitted] • Cost-effective bulk HEAs electrocatalysts are fabricated. • CoCrFeNiAlMo catalyst shows a low overpotential for OER. • Multicomponent property of the HEAs promotes catalytic activities. [ABSTRACT FROM AUTHOR]

A novel Ti35Zr15Nb25Mo15Ta10 high‐entropy alloy has been designed, fabricated, and characterized as a viable substitute for the conventional Ti‐6Al‐4V alloy in biomaterial applications. Alloy design is conducted based on various parameters including mixing enthalpy (ΔHmix), omega parameter (Ω), delta parameter (δ), valence electron concentration (VEC), and biocompatibility aspects of its constituent elements with CALPHAD approach. The fabricated Ti35Zr15Nb25Mo15Ta10 alloy demonstrated a body‐centered‐cubic (BCC) solid solution phase with no evidence of intermetallics. Nanoindentation investigations exhibited high hardness of ≈5.1 GPa and a young modulus of ≈140 GPa. The alloy proposed better surface properties and tribological behaviour in comparison with the Ti‐6Al‐4V alloy in dry and wet (under PBS solution) conditions. Furthermore, the newly designed alloy revealed promising behaviour after investigation of in‐vitro biocompatibility compared to the Ti‐6Al‐4V alloy. These initial benefits of the Ti35Zr15Nb25Mo15Ta10 alloy concerning mechanical properties and wear resistance over the conventional Ti‐6Al‐4V alloy present an avenue for exploring novel orthopedic implant alloys. [ABSTRACT FROM AUTHOR]

The combined effects of high‐temperature and long‐term exposure to oxidation environment on an AlCoCrFeNi‐based high entropy alloy (HEA) are investigated. The alloy has a composition of Al10Co20Cr20Fe20Ni30 (at%) and is oxidized in lab air at 1000 °C for 1000 h to emulate working conditions and long operation cycles of gas turbines. The microstructure and oxide formation of the HEA are characterized using scanning electron microscopy, energy‐dispersive spectroscopy, and X‐ray diffraction. The performance of the HEA is compared to that of Inconel 625 and Hastelloy X and shows slower oxidation kinetics than Inconel 625 until 750 h. The HEA has the thinnest oxide layer of the three alloys and exhibits a triplex structure with a continuous Cr2O3 outer scale, a semi‐continuous Al2O3 subscale, and deep AlN precipitates. The matrix shows signs of Cr and Al depletion after 1000 h, leading to its inability to replace the degraded oxide scales that evaporated or spalled, and decreases its long‐term oxidation resistance. Overall, the HEA shows good oxidation resistance until 750 h, but may benefit from a higher Al content on the surface to form a longer‐lasting Al2O3 subscale that would remain protective beyond 750 h. [ABSTRACT FROM AUTHOR]

The synthesis of high‐entropy alloys (HEAs) with ultra‐small particle sizes has long been a challenging task. The complex and time‐consuming synthesis process hinders their practical application and widespread adoption. This study presents the novel synthesis of TiO2 nanoparticles loaded with a quinary high‐entropy alloy through flame spray pyrolysis (FSP) for the first time. The extremely fast heating rate of flame combustion makes the precursor fast pyrolysis gasification, high temperature in the flame field promotes the metal vapor mixing uniformly, and the fast quenching process can reduce the particle aggregation sintering, the ultra‐small particle size of HEA firmly attached to the TiO2 surface. The catalysts prepared via this gas‐to‐particle pathway exhibit excellent performance in CO2 hydrogenation, achieving a conversion rate of 62% at 450 °C, and maintaining their activity for over 220 h without significant particle agglomeration. This finding provides valuable insights for the future design of catalytically active materials with enhanced activity and long‐term stability. [ABSTRACT FROM AUTHOR]

Water electrolysis is considered the cleanest method for hydrogen production. However, the widespread popularization of water splitting is limited by the high cost and scarce resources of efficient platinum group metals. Hence, it is imperative to develop an economical and high‐performance electrocatalyst to improve the efficiency of hydrogen evolution reaction (HER). In this study, a hierarchical porous sandwich structure is fabricated through dealloying FeCoNiCuAl2Mn high‐entropy alloy (HEA). This free‐standing electrocatalyst shows outstanding HER performance with a very small overpotential of 9.7 mV at 10 mA cm−2 and a low Tafel slope of 56.9 mV dec−1 in 1 M KOH solution, outperforming commercial Pt/C. Furthermore, this electrocatalytic system recorded excellent reaction stability over 100 h with a constant current density of 100 mA cm−2. The enhanced electrochemical activity in high‐entropy alloys results from the cocktail effect, which is detected by density functional theory (DFT) calculation. Additionally, micron‐ and nano‐sized pores formed during etching boost mass transfer, ensuring sustained electrocatalyst performance even at high current densities. This work provides a new insight for development in the commercial electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

A novel Cu35Ni35Cr10Fe10Sn10 high‐entropy alloy (HEA) filler with a relatively low melting point (935°C) was designed for brazing diamonds, and its technical advantages over conventional NiCr‐based fillers, that is, favorable wettability, high bonding strength, low thermal damage, and high mechanical performance, were convincingly demonstrated. The newly developed HEA filler had a contact angle of only 11° on the graphite (energetically close to diamond) surface and it could braze diamonds at 1000°C, much lower than the brazing temperature of conventional NiCr‐based fillers. Consequently, the brazed diamond exhibited greatly decreased surface thermal damage, higher fracture strength, and better wear performance. The solidified microstructure of the HEA filler contained three solid solution phases, that is, FeCrNi‐rich, CuNi‐rich, and CuSnNi‐rich phases that were formed through the liquid phase separation process, plus a minor phase of nanosized FeCr‐rich precipitates. The reaction products at the HEA filler/diamond interface were simply an inner Cr3C2 layer and an outer Cr7C3 layer, without other complex brittle compounds that are commonly seen in NiCr‐based fillers after diamond brazing. Apparently, the HEA filler reacted more sufficiently with diamonds, which contributed to improve the bonding strength and wear resistance of the brazed diamond. This work provided a new application scenario for HEAs as promising filler materials for brazing diamonds. [ABSTRACT FROM AUTHOR]

A MOF-derived low Ru-loaded high entropy alloy self-supporting electrode is proposed for ZABs. This work provides a good guide for improving catalytic performance. [Display omitted] Exploiting the high-entropy alloy (HEA) electrocatalysts with the synergistic effect of multi-metal components is an effective approach to address the slow kinetics and undesirable stability of the oxygen evolution reaction (OER) in Zn-air batteries (ZABs), but still faces many challenges. In this study, a multimetallic Metal-organic framework (MOF)-derived HEA catalyst was successfully fabricated on carbon fiber as a flexible self-supporting electrode (denoted as CC@FeCoNiMoRu-HEA/C) for high-performance liquid/flexible ZABs using a facile and cost-effective strategy. The three-dimensional (3D) highly open network framework and hierarchical porous structure accelerate the mass transport of OH−/O 2 and charge transfer. The electronic structure adjustment, lattice defects and high entropy effects enable the CC@FeCoNiMoRu-HEA/C catalysts to perform high OER catalytic activity and strong durability while reducing the Ru content and lowering the economic cost. In situ Raman spectra and XPS results reveal the generation of metal-OOH intermediates on the HEA surface during the OER process. In a practical demonstration, the liquid ZAB assembled with CC@FeCoNiMoRu-HEA/C + Pt/C as the air electrode offers stable open-circuit voltage, large power density, excellent specific capacity and satisfactory cycle life, outperforming the commercial RuO 2 + Pt/C-based reference ZAB. More attractively, the flexible solid-state ZAB also achieves fast dynamic response, high peak power density, robust cycling stability as well as favorable mechanical flexibility, indicating a promising application prospect in future flexible electronics and wearable devices. This work provides a viable pathway to develop low precious metal-loaded HEAs as advanced OER self-supporting electrocatalysts and realize high-performance flexible energy storage devices. [ABSTRACT FROM AUTHOR]

The selective laser melting (SLM) technique applied to high-entropy alloys (HEAs) has attracted considerable attention in recent years. However, its practical application has been restricted by poor surface quality. In this study, the capability of laser polishing on the rough surface of a Co-free HEA fabricated using SLM was examined. Results show that the initial SLM-manufactured (as-SLMed) surface of the Co-free HEA, with a roughness exceeding 3.0 µm, could be refined to less than 0.5 µm by laser polishing. Moreover, the microstructure, microhardness, and wear resistance of the laser-polished (LP-ed) zone were investigated. Results indicate that compared with the microhardness and wear resistance of the as-SLMed layer, those of the LP-ed layer decreased by 4% and 11%, respectively, because of the increase in grain size and reduction of the BCC phase. This study shows that laser polishing has an excellent application prospect in surface improvement of HEAs manufactured by SLM. [ABSTRACT FROM AUTHOR]

In this work, the influence of laser power (LP), scanning speed (SS), and powder feeding speed (PF) on the porosity, dilution, and microhardness of lightweight refractory high-entropy alloy (RHEA) coatings produced via laser cladding (LC) was investigated. Variance analysis (ANOVA) was deployed to ascertain the effect of LP, SS, and PF on performance metrics such as porosity, dilution, and microhardness. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) was then applied to optimize these processing parameters to minimize porosity, achieve suitable dilution, and maximize microhardness, enhancing the mechanical properties of RHEA coatings. Finally, machine learning models—Random Forest (RF), Gradient Boosting Decision Tree (GBDT), and Genetic Algorithm-enhanced GBDT (GA-GBDT)—were developed using orthogonal experimental data, with GA-GBDT demonstrating superior predictive accuracy. The proposed approach integrates statistical analysis and advanced ML techniques, providing a better understanding into optimizing LP, SS, and PF for improved RHEA coatings performance in industrial applications, thereby advancing laser cladding technology. [ABSTRACT FROM AUTHOR]

To enhance high-temperature wear resistance of H13 steel, laser cladding was used to prepare a high-entropy alloy + carbide composite coating. The microstructure and high-temperature wear resistance of the composite coating were systematically analyzed. The results indicate that the FeCoCrNiAl + WC composite coating had a phase structure of BCC + FCC solid solutions, with a small amount of CFe15.1. The microstructure of the composite coating consisted of columnar and equiaxed grains. The microhardness of the FeCoCrNiAl + WC composite coatings was approximately 3.0–3.4 times that of H13. At wear temperatures of 823 K, compared with H13 steel, the wear volumes of composite coatings with different WC contents were reduced by 73.4%–80.2%. Among these, the FeCoCrNiAl + 10% WC composite coating showed the lowest wear volume. Furthermore, when wear temperatures increased from 623 K to 823 K, compared with H13 steel (108.37%), the increase in the wear volume of the FeCoCrNiAl + 10% WC coating was reduced to 90.82%, which indicates the FeCoCrNiAl + 10% WC coating had better high-temperature wear resistance. The wear mechanisms of the composite coating were abrasive and oxidative wear, while H13 steel exhibited abrasive wear, oxidative wear and fatigue wear. [ABSTRACT FROM AUTHOR]

CoCrFeMnNi-XZrO2 (X is a mass percentage, X = 1, 3, 5, and 10) high-entropy alloy composite coatings were successfully prepared on 0Cr13Ni5Mo martensitic stainless steel substrates using laser cladding technology. The phase composition, microstructure, mechanical properties, and cavitation erosion behavior of the composite coatings under different contents of ZrO2 were studied. The mechanism of ZrO2 particle-reinforced cavitation corrosion resistance was studied using ABAQUS2023 finite element software. The results show that the phase structure of the composite coating organization is composed of FCC phase reinforced by ZrO2 phase. The addition of ZrO2 causes lattice distortion. The coatings have typical branch crystals and an equiaxed crystal microstructure. With the increase in ZrO2 content, the microhardness of the composite coatings gradually increases. When X = 10%, the coating's microhardness reached 348 HV, which was 95.53% higher than the high-entropy alloys without ZrO2 added. Adding ZrO2 can prolong the incubation period of high-entropy alloys; the high-entropy alloy composite coating with 5 wt.% ZrO2 exhibited the best cavitation resistance, with a cumulative volume loss rate of only 15.74% of the substrate after 10 h of ultrasonic cavitation erosion. The simulation results indicate that ZrO2 can withstand higher stress and deformation in cavitation erosion, reduce the degree of substrate damage, and generate higher compressive stress on the coating surface to cope with cavitation erosion. [ABSTRACT FROM AUTHOR]

The microstructure and soft magnetic properties under direct current (DC) mode and alternating current (AC) mode of FeCoNiAl1−xSix (x = 0.2, 0.4, 0.6) high-entropy alloys (HEAs) are investigated. All the studied HEAs show body-centered cubic (BCC) structures, and the [100] texture is formed in the x = 0.4 HEA. The iron (Fe) segregation at the grain boundaries is helpful in increasing the soft magnetic properties under DC. The FeCoNiAl0.6Si0.4 (x = 0.4) HEA exhibits optimal DC and AC soft magnetic properties, primarily due to the formation of the texture along the easy magnetization axis. The x = 0.4 HEA shows the highest permeability (μi = 344 and μm = 1334) and the smallest coercivity (Hc = 51 A/m), remanence (Br = 132 mT), and hysteresis loss (Pu = 205 J/m3). In comparison to the x = 0.2 HEA and x = 0.6 HEA, the total loss (AC Ps) at 50 Hz of the x = 0.4 HEA is decreased by 15% and 18%, and it is reduced at 950 Hz by 13% and 7%. Our findings can provide a useful approach for developing novel HEAs with increased soft magnetic properties by tuning ferromagnetic elemental segregation and forming the texture along the easy magnetization axis. [ABSTRACT FROM AUTHOR]

A family of TiHfZrNb high-entropy alloys has been considered novel biomaterials for high-performance, small-sized implants. The present work evaluates the role of niobium on passivation kinetics and electrochemical characteristics of passive film on TiHfZrNb alloys formed in Hanks' simulated body fluid by analyzing electrochemical data with three analytical models. Results confirm that higher niobium content in the alloys reinforces the compactness of the passive film by favoring the dominance of film formation and thickening mechanism over the dissolution mechanism. Higher niobium content enhances the passivation kinetics to rapidly form the first layer, and total surface coverage reinforces the capacitive-resistant behavior of the film by enrichment with niobium oxides and reduces the point defect density and their mobility across the film, lowering pitting initiation susceptibility. With the high resistance to dissolution and rapid repassivation ability in the aggressive Hanks' simulated body fluid, the TiHfZrNb alloys confirm their great potential as new materials for biomedical implants and warrant further biocompatibility testing. [ABSTRACT FROM AUTHOR]

This paper investigated the FeCoCrNiAl high-entropy alloy on H13 steel, prepared using laser cladding, to improve the elevated-temperature wear resistance of the alloy. The results revealed that FCC and BCC phases, in terms of the coating, produced a large dislocation density. The coating exhibited a columnar and equiaxed crystal microstructure. With the comprehensive effects of fine-grain strengthening, solid solution strengthening, and dislocation strengthening, the average hardness of the coating (500 HV0.1) was improved by 150% compared with that of H13 steel (200 HV0.1). The wear experiments were conducted at 623 K, 723 K, and 823 K. Compared with H13 steel, the wear volume of the coating decreased by 59.20%, 70.79%, and 78.20% under different temperatures. The wear forms impacting the coating were mainly abrasive wear and oxidation wear. However, H13 steel presented adhesive wear and fatigue wear, in addition to abrasive wear and oxidation wear. [ABSTRACT FROM AUTHOR]

High-entropy alloys(HEAs)have attracted considerable attention from the research community as a pioneering alloy design paradigm over the past two decades. They have fundamentally challenged traditional design paradigms and exhibited exceptional mechanical properties and functional characteristics, thereby positioning themselves as promising candidates for significant engineering applications in the future. Recent advancements have unveiled several alloy systems that demonstrate exceptional performance across diverse metrics, including low-temperature fracture toughness, high-temperature strength, impact resistance, radiation tolerance, and fatigue resistance. These qualities render HEAs highly attractive materials for research with substantial application potential in critical domains such as deep space exploration, deep-sea investigations, low-temperature superconductivity, and advanced nuclear energy technologies. This paper will briefly introduce the concept and classification of HEAs, and review the experimental progress of HEAs under various extreme conditions such as extremely low temperatures, high-speed impacts, and high nuclear radiation. We also summarize the strategies for enhancing the strength and toughness of HEAs, and extract the deformation mechanisms and physical and chemical properties of HEAs under different extreme loads. It is foreseeable that the main development direction of HEAs will be to form microscopic fluctuations in chemical composition and construct multi-scalestructural ordering efficiently through fine adjustment of the selection and proportion of alloying elements and optimization of heat treatment processes. For comprehensive studies on HEAs subjected to extreme loads, it is essential to explore their microscopic deformation mechanisms further while proposing innovative strategies designed to address inherent trade-offs between strength and toughness. The integration of state-of-the-art simulation techniques combined with advanced characterization methods will be crucial for improving research efficiency while providing insights into microstructural behavior. Additionally, tailored optimization approaches should be implemented for distinct advantageous systems and phase structures, particularly those capable of activating dislocation movements, twinning, phase transformations and incorporating novel processing methodologies such as additive manufacturing. Finally, conducting more realistic simulation experiments that closely replicate extreme environments along with generating relevant engineering data are vital steps toward accelerating the practical application of HEAs in challenging settings. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The pronounced brittleness of hard Laves phase intermetallics is detrimental to their tribological properties at room temperature. In this study, we utilized a heterogeneous structure to engineer an ultrastrong dual-phase (Laves + B2) AlCoFeNiNb high-entropy alloy that exhibits a low wear rate (3.82×10−6 mm3/(N·m)) at room temperature. This wear resistance in the ball-on-disc sliding friction test with the counterpart of Al2O3 balls stems from the activated deformation ability in the ultrafine Laves lamellae under heterogeneous interface constraints. Furthermore, as tribological stress intensifies, the surface deformation mechanism transitions from dislocation slip on the basal and pyramidal planes to a unique combination of local shear and grain rotation within the Laves phase. Our study illuminates fresh perspectives for mitigating the embrittling effect of Laves phase intermetallics under tribological loading and for the development of wear-resistant materials. [ABSTRACT FROM AUTHOR]

This study delves into effects of deep cryogenic treatment (DCT) on enhancing the hydrogen embrittlement resistance of CoCrFeMnNi high-entropy alloy fabricated via laser powder-bed-fusion (L-PBF). Comparatively assessing as-print, conventional heat treatment, and DCT, we uncover how nanotwin formation within matrix serves as a critical mechanism to combat adverse effects of hydrogen embrittlement. This work reveals that DCT not only mitigates inherent residual stresses from L-PBF, thereby fostering dislocation redistribution and microstructural stabilization, but also synergizes with high-density dislocation cells. Our findings articulate a nuanced understanding of microstructural evolution in response to post-treatments and consequential enhancement of hydrogen embrittlement resistance. Laser-based additively manufactured CoCrFeMnNi undergoes post heat treatment and deep cryogenic treatment to tailor dislocations and residual stress. The inherent residual stress acts as the driving force for the redistribution of dislocations, leading to the development of a stable microstructure after deep cryogenic treatment. High-density dislocation cells and hydrogen collaborate to lower the local stacking fault energy, triggering gradient nanotwins. Nanotwin-ability effects by deep cryogenic treatment (77 K × 36 h) on the hydrogen embrittlement resistance of CoCrFeMnNi with interior defects are verified. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations were utilized to investigate the mechanical properties of the Al–Co–Cr–Fe–Ni high-entropy alloy and observe atomic microstructure and internal dislocation line changes under different parameter conditions. The findings demonstrate that the mechanical properties of the AlCoCrFeNi3 high-entropy alloy are significantly superior to those of conventional alloys in ambient temperature. During the tensile process, the face-centered structure undergoes interconversion with other structure types, while the internal dislocation lines gradually increase. The presence of grain boundaries impedes dislocation movement, resulting in lower deformation capacity and tensile strength in polycrystals compared to single crystals. Enhancing Ni content, increasing strain rate, and decreasing temperature during tensile process contributes to the enhancement of the mechanical properties of material. Among these factors, the Ni content exerts the most significant influence on the mechanical properties of the material. [ABSTRACT FROM AUTHOR]

While the influence of size on nanomaterial uptake has been extensively explored, it remains elusive how cells simultaneously respond to multiple, size‐varying particles due to the lack of a proper quantitative assay. In this study, a strategy named "metal‐doping engineering" is developed, and constructed a library of multi‐elemental alloys (MEAs) features precisely controlled size and dopant dosage for quantification with mass spectra. Next a comprehensive study of cellular uptake behaviors is conducted when treated with dual‐, triple‐, and quadra‐, size‐differing nanoparticles. Specifically, the exposure to triple‐, and quadra‐, size‐differing MEAs resulted in an unprecedented, enhanced uptake of counterpart in the middle size as 10/20 nm. Further efforts including RNA‐sequencing and photo‐affinity labeling‐assisted proteomics are devoted to uncovering the underlying mechanism, wherein the role of nonconical endocytic pathways in fast‐endophilin‐mediated endocytosis is uncovered. Given the capacity of MEAs as chaperones to facilitate the uptake of one featuring a predetermined size promoted to propose a straightforward, "bystander nanomaterials"‐assisted drug delivery strategy, whose superior dosage‐reduced radio‐sensitization performance and anti‐tumoral outcome are confirmed in vivo. [ABSTRACT FROM AUTHOR]

We study the effects of the chemical short-range order (SRO) on the thermal conductivity of the refractory high-entropy alloy HfNbTaTiZr using atomistic simulation. Samples with different degrees of chemical SRO are prepared by a Monte Carlo scheme. With increasing SRO, a tendency of forming HfTi and TiZr clusters is found. The phonon density of states is determined from the velocity auto-correlation function and chemical SRO modifies the high-frequency part of the phonon density of states. Lattice heat conductivity is calculated by non-equilibrium molecular dynamics simulations. The heat conductivity of the random alloy is lower than that of the segregated binary alloys. Phonon scattering by SRO precipitates might be expected to reduce scattering times and, therefore, decrease thermal conductivity. We find that, in contrast, due to the increase of the conductivity alongside SRO cluster percolation pathways, SRO increases the lattice heat conductivity by around 12 %. This is expected to be a general result, extending to other HEAs. [ABSTRACT FROM AUTHOR]

The effects of different Mn concentrations on the generalized stacking fault energies (GSFE) and elastic properties of MnxCoCrFeNi high-entropy alloys (HEAs) have been studied via first-principles, which are based on density functional theory. The relationship of different Mn concentrations with the chemical bond and surface activity of MnxCoCrFeNi HEAs are discussed from the perspectives of electronic structure and work function. The results show that the plastic deformation of MnxCoCrFeNi HEAs can be controlled via dislocation-mediated slip. But with the increase in Mn concentration, mechanical micro twinning can still be formed. The deformation resistance, shear resistance, and stiffness of MnxCoCrFeNi HEAs increase with the enhancement of Mn content. Accordingly, in the case of increased Mn concentration, the weakening of atomic bonds in MnxCoCrFeNi HEAs leads to the increase in alloy instability, which improves the possibility of dislocation. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) have drawn significant attention due to their unique design and superior mechanical properties. Comprising 5–35 at% of five or more elements with similar atomic radii, HEAs exhibit high configurational entropy, resulting in single-phase solid solutions rather than intermetallic compounds. Additive manufacturing (AM), particularly direct energy deposition (DED), is effective for producing HEAs due to its rapid cooling rates, which ensure uniform microstructures and minimize defects. These alloys typically form face-centered cubic (FCC) or body-centered cubic (BCC) structures, contributing to their exceptional strength, hardness, and mechanical performance across various temperatures. However, FCC-structured HEAs often have low yield strengths, posing a challenge for structural applications. In this study, a Ni-Co-Fe-Cr-Al-Ti HEA was manufactured using the DED method. This study proposes that the addition of aluminum and titanium creates a γ + γ′ phase structure within a multicomponent FCC-HEA matrix, enhancing the thermal stability and coarsening the resistance and strength. The γ′ phase with an ordered FCC structure significantly improves the mechanical properties. Analysis confirmed the presence of the γ + γ′ structure and demonstrated the alloy's high tensile strength and microhardness. This approach underscores the potential of AM techniques in advancing HEA production for high-performance applications. [ABSTRACT FROM AUTHOR]

Shaped charge liner (SCL) has been extensively applied in oil recovery and defense industries. Achieving superior penetration capability through optimizing SCL structures presents a substantial challenge due to intricate rate-dependent processes involving detonation-driven liner collapse, high-speed jet stretching, and penetration. This study introduces an innovative optimization strategy for SCL structures that employs jet penetration efficiency as the primary objective function. The strategy combines experimentally validated finite element method with machine learning (FEM-ML). We propose a novel jet penetration efficiency index derived from enhanced cutoff velocity and shape characteristics of the jet via machine learning. This index effectively evaluates the jet penetration performance. Furthermore, a multi-model fusion based on a machine learning optimization method, called XGBOOST-MFO, is put forward to optimize SCL structure over a large input space. The strategy's feasibility is demonstrated through the optimization of copper SCL implemented via the FEM-ML strategy. Finally, this strategy is extended to optimize the structure of the recently emerging CrMnFeCoNi high-entropy alloy conical liners and hemispherical copper liners. Therefore, the strategy can provide helpful guidance for the engineering design of SCL. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, thermodynamic quantities were investigated using cluster expansion and the variational method for high-entropy and medium-entropy alloys (HEAs and MEAs, respectively). In the alloy systems combined with elements that tend to form HEAs, the absolute enthalpy value was small, and the entropy term was close to the value of an ideal solution. The tendency of ordering and the accompanying change in mean square atomic displacement (MSAD) were investigated in detail for four MEAs; namely, the FeCoNi, MnFeNi, MnCoNi, and CrCoNi systems. For these alloys, the ordering tendency and the phase-separation tendency in the low-temperature region were investigated. In addition, the presence of short-range order (SRO) in the high-temperature range was confirmed from the analysis using the Warren--Cowley order parameter. Thermal equilibrium structures were used to evaluate the MSADs at various temperatures. Long-range ordering developing at low temperature tended to reduce MSAD, although in the high temperature range the effect on MSAD from the SRO was very small. [ABSTRACT FROM AUTHOR]

This study explores the influence of oxygen and nitrogen flow ratios on the microstructure and mechanical properties of AlCrTaTiZr high-entropy oxynitride films. Oxygen flow rates (0%–0.75%) were adjusted while maintaining a fixed nitrogen flow ratio (RN = 15%) to fabricate films with similar compositions. The results show that increasing oxygen flow enhanced hardness through solid solution strengthening and grain refinement, though excessive oxygen caused an amorphous structure and reduced hardness. After annealing at 900 °C, the hardness of all films was further increased. The film with a nitrogen flow ratio 40 times higher than oxygen exhibited the highest hardness of 21.8 GPa, along with superior mechanical performance. These findings highlight the potential of high-entropy oxynitride films for applications requiring high wear resistance and adhesion. [ABSTRACT FROM AUTHOR]

Fatigue property is an important index for novel high-entropy alloys (HEAs) before their engineering applications. Here we engineer a Al0·3CoCrFeNi HEA with hierarchically heterogeneous microstructure by cold rolling and annealing treatment, which includes heterogeneous grains, annealing and deformation twins, residual dislocations and B2 precipitates with different morphologies, sizes and distributions. Stress-life (S–N) tests and characterization techniques including scanning electron microscope (SEM) and transmission electron microscope (TEM) were carried out to investigate fatigue properties as well as corresponding mechanisms. It is found that this HEA possesses good strength-ductility combination (i.e., yield strength of ∼870 MPa, ultimate tensile strength of ∼1060 MPa and ductility of ∼26 %) and fatigue resistance with fatigue ratio of ∼0.46 under stress ratio of −1. This fatigue ratio exceeds those of most reported HEAs. High strength renders the fatigue deformation mainly occurs in deformation twin regions decorated with B2 precipitates. Surface damage morphologies indicate that fatigue cracks initiate from persistent slip band-like shear bands. In addition, microstructural hierarchy results in the deflected fatigue crack propagation path, which is beneficial for the enhancement of fatigue resistance. Present results offer the guidance on future design for high fatigue-resistant HEAs by manipulating heterogeneous microstructure.

To meet the service conditions and strength requirements of turbine stator blades and the inner and outer rings of aero engine casings, CoFeNiCrMn high-entropy alloy filler was used to braze SiCf/SiC/GH536 joints. This study investigated the effects of holding time on the joints' microstructure and mechanical properties. Key phases identified in the welded joints include MoNiSi, FCC, and Cr23C6 near the composites, with brittle Ni3Si and Fe2Si intermetallic compounds forming due to filler diffusion. Optimal brazing parameters were found to be 1220 °C for 30 min with a shear strength of 64.28 MPa. The study also highlighted that increased holding time at the same temperature enhances diffusion at the joint, increasing brittle intermetallic compounds, initially improving shear strength, which then declines. Microstructural and fracture morphology analyses revealed that insufficient insulation time leads to poor welding and stress concentration at pores, causing cracks. Excessive insulation time results in joint fractures due to the brittleness of Ni3Si and Fe2Si intermetallic. Thus, joint shear strength correlates with welding quality and intermetallic compound distribution.

Constructing bioinspired architectures in metallic materials is an effective way to overcome the inherent strength and plasticity trade-off dilemma. However, conventional processing approaches are difficult to finely tailor the microstructures and mechanical properties of bioinspired architectures. Here, using laser remelting technology, we finely and controllably fabricate three sophisticated bioinspired architectures in a high-entropy alloy (HEA). The bioinspired HEA with brick-and-mortar architecture shows an excellent yield strength of ∼520 MPa with a large uniform elongation of ∼35%. Such enhanced strength-plasticity synergy is mainly attributed to the hetero-deformation between the hard and soft regions of bioinspired architectures.

This study delves into effects of deep cryogenic treatment (DCT) on enhancing the hydrogen embrittlement resistance of CoCrFeMnNi high-entropy alloy fabricated via laser powder-bed-fusion (L-PBF). Comparatively assessing as-print, conventional heat treatment, and DCT, we uncover how nanotwin formation within matrix serves as a critical mechanism to combat adverse effects of hydrogen embrittlement. This work reveals that DCT not only mitigates inherent residual stresses from L-PBF, thereby fostering dislocation redistribution and microstructural stabilization, but also synergizes with high-density dislocation cells. Our findings articulate a nuanced understanding of microstructural evolution in response to post-treatments and consequential enhancement of hydrogen embrittlement resistance.Highlights Laser-based additively manufactured CoCrFeMnNi undergoes post heat treatment and deep cryogenic treatment to tailor dislocations and residual stress.The inherent residual stress acts as the driving force for the redistribution of dislocations, leading to the development of a stable microstructure after deep cryogenic treatment.High-density dislocation cells and hydrogen collaborate to lower the local stacking fault energy, triggering gradient nanotwins.Nanotwin-ability effects by deep cryogenic treatment (77 K × 36 h) on the hydrogen embrittlement resistance of CoCrFeMnNi with interior defects are verified.

FeCoNiCrCu high-entropy alloy (HEA) and Cu foils were utilized as the intermediate layer to conduct laser welding of TC4 titanium alloy and Q345 steel. Welding is performed by adding single HEA and Cu/HEA double foils as interlayer respectively. We conducted in-depth studies on the microstructure and mechanical properties of the joint by stereomicroscopy, metallographic microscope, scanning electron microscope (SEM), micro-area X-ray diffraction (XRD), nanoindentation, electron backscatter diffraction (EBSD), and tensile testing. The results indicate that the position of the copper foil significantly affects the microstructure and performance of the joint. When the copper foil is on the TC4 side, its lower melting point causes a deeper keyhole, resulting in a narrower weld bead and then reduced content of Fe and Ti in the weld. Simultaneously, the increased proportion of Cu in the weld significantly enhances the content of Cu-rich phases. In the weld zone, we observed freely distributed Cu-rich phases and Ti-rich phases generated along the interface. Under tensile loads, cracks primarily initiate and propagate along the Cu-rich phases, leading to typical delamination on the fracture surface. With the copper foil on the TC4 side, due to the increased copper content in the microstructure, the hardness of the interface between the titanium alloy and the weld decreases, while the joint exhibits the highest tensile strength, reaching a maximum of 417 MPa.

Abstract We study the effects of the chemical short-range order (SRO) on the thermal conductivity of the refractory high-entropy alloy HfNbTaTiZr using atomistic simulation. Samples with different degrees of chemical SRO are prepared by a Monte Carlo scheme. With increasing SRO, a tendency of forming HfTi and TiZr clusters is found. The phonon density of states is determined from the velocity auto-correlation function and chemical SRO modifies the high-frequency part of the phonon density of states. Lattice heat conductivity is calculated by non-equilibrium molecular dynamics simulations. The heat conductivity of the random alloy is lower than that of the segregated binary alloys. Phonon scattering by SRO precipitates might be expected to reduce scattering times and, therefore, decrease thermal conductivity. We find that, in contrast, due to the increase of the conductivity alongside SRO cluster percolation pathways, SRO increases the lattice heat conductivity by around 12 %. This is expected to be a general result, extending to other HEAs.

This study explores the use of silicon carbide to strengthen CoCrFeNi high-entropy alloys (HEAs) with face-centered cubic structure. CoCrFeNi(SiC)x (x = 0, 0.1, 0.2, and 0.3) HEAs were prepared through laser metal deposition. The effects of different contents of SiC particles on the microstructure and mechanical properties of CoCrFeNi HEA were investigated. The results indicate that the addition of SiC particles led to the formation of the Cr7C3 phase, which refined the grain size and shifted the grain orientation from to . With the further addition of SiC, the amount of Cr7C3 phase increased, and β-SiC particles appeared. The Cr7C3 phase increased the average hardness of specimens from 191.71 HV to 403.86 HV. Tensile tests showed that the 10 at.% SiC specimens exhibited a yield strength of 534.00 MPa, an ultimate tensile strength of 799.67 MPa, and an elongation of 8.17%, hence optimizing the combination of ultimate tensile strength and elongation. The improvement in mechanical properties is mainly attributed to the refinement of grain boundaries and enhancement of dislocation density.

This study investigates the advantages of combining Spark Plasma Sintering (SPS) with Laser Cladding (LC) technology in the production of AlCoCrFeNi high-entropy alloy (HEA). By comprehensively applying SPS and LC composite processing techniques, we achieve rapid preparation of high-performance AlCoCrFeNi HEA. SPS technology enables rapid sintering under high-temperature conditions, while LC technology allows precise control of microstructure generation on the workpiece surface. Experimental results show that AlCoCrFeNi HEA prepared by single SPS technology exhibits a body-centered cubic (BCC) solid solution structure, while AlCoCrFeNi HEA processed with a combination of SPS and LC techniques demonstrates a complex microstructure consisting of equiaxed BCC phase, uniformly distributed granular face-centered cubic (FCC) solid solution, and α-Al2O3 ceramic phase. Composite processing also eliminates voids and pores caused by single SPS processing, resulting in AlCoCrFeNi HEA with low porosity. Furthermore, the maximum hardness of AlCoCrFeNi HEA produced by composite processing technology is approximately 644.1HV, significantly higher than that of AlCoCrFeNi HEA processed solely by SPS (approximately 328.7HV). Wear test results show that AlCoCrFeNi HEA processed by composite machining exhibits significant advantages in wear resistance, with the width and depth of wear tracks significantly reduced compared to AlCoCrFeNi HEA processed solely by SPS technology, with a 33.17% higher wear rate. In conclusion, composite processing using SPS combined with LC technology enables rapid preparation of AlCoCrFeNi HEA with low porosity, high hardness, and high wear resistance.

The erosion-corrosion mechanism in rotary flowing seawater is hugely complicated due to the multiscale coupling processes of particle-surface impact, ion mass transfer, and interface electrochemistry. Therefore, developing erosion-corrosion resistant material and exploring the synergistic mechanism between sand erosion and electrochemical corrosion is vital. This study conducted the erosion-corrosion test on Ni2FeCrMo0.2 high-entropy alloy under the particle-seawater flow. Based on a coupled analysis of multi-component weight loss, electrochemical behavior, and microscopic damage morphology, the multiscale coupling processes of sand transportation, particle-surface impact, ion mass transfer, and interface electrochemistry were revealed. The present study found that with the increase of sand size, the energy carried by the particles promoted impact erosion. Additionally, particle movement enhanced ion mass transfer through turbulent effects, and the impact behavior disrupted the passivation film to promote electrochemical processes by reducing the thickness of the passivation film, leading to an increase in the erosion-corrosion rate. However, when the particle size continued to increase to a certain extent, the impact frequency decreased, reducing the erosion-corrosion rate. As the sand size grew, the dominant damage mechanism transitioned from pure corrosion (100 μm) to synergistic effects (200 μm, 400 μm) and then to pure erosion (800 μm). This study provides an in-depth understanding of the erosion-corrosion mechanism in seawater from the perspective of particle-ion-fluid-surface interaction by multi-element characterization.

An in-depth understanding of the bimodal scale particle reinforced composites, including the particle content and size, phase constitution and distribution, and their effects on mechanical properties and deformation mechanisms, is essential to advance the study of high performance high entropy alloys (HEAs). In this study, the bimodal-sized (nano + micron)(N + M)-Al2O3P/CoCrFeMnNi reinforced composites and monomadal-sized micron(M)-Al2O3P/CoCrFeMnNi reinforced composites were successfully fabricated using a two-step ball milling process in conjunction with spark plasma sintering (SPS) technology. Results showed that the Al2O3P/CoCrFeMnNi composites primarily consisted of fcc structure, with Al2O3 and MnAl2O4 as secondary phases. The M-Al2O3P reinforced composites contained obvious heterogeneous structure while (N + M)-Al2O3P reinforced composites exhibited a multi-scale grain structure comprising of double-sized reinforcement and multiple-sized matrix grains. The yield strength (YS) of bimodal-size particle reinforced composites was higher than that of monomadal particle reinforced composites. For example, the YS of (N-5)/(M − 5) and (N-5)/(M − 10) composites was 117% and 133% higher than that of HEA, respectively. Intriguingly, (N + M)-Al2O3P reinforced composites effectively addressed the issue of reduced material strength caused by a high concentration of particles with a monomadal size. Moreover, the composites of (N-5)/(M − 5) and (N-5)/(M − 10) with a high content of lightweight Al2O3P effectively contributed to the reduction in density of HEA, exhibiting a decrease by 11% and 17% compared to pure HEA, respectively.

The Pt-based catalysts are quite promising for ethylene glycol oxidation reaction (EGOR) due to their superior catalytic activity and their high cost, low reserves and poor stability of precious metals greatly limit the further large-scale application. Developing low-Pt and high-performance anode electrocatalysts is urgent to direct ethylene glycol fuel cells. At present, a high-entropy alloy (HEA) of PtPdNiCoBi/C has been developed for EGOR, and its catalytic performance has been verified by electrochemical and physical methods. Notably, the EGOR peak current density on PtPdNiCoBi/C (0.782 A mg−1PtPd) reaches 3.54 times of Pt/C (0.221 A mg−1Pt), and the residual current on PtPdNiCoBi/C (0.092 A mg−1PtPd) is superior to that of Pt/C (0.076 A mg−1Pt) after 3000 s. Moreover, the current density retention (84.0%) of it after 500 cycles, is also superior to that of the Pt/C (78.8%). This work would support the future practical use of HEA catalyst for fuel cells. [ABSTRACT FROM AUTHOR]

CrMnFeCoNi high-entropy alloy (HEA) manufactured by laser powder bed fusion has been demonstrated to possess a superior trade-off of tensile strength and ductility due to unique microstructures during the printed process. However, the improvement of mechanical properties of 3D printed-CrMnFeCoNi HEA through the addition of nano-scaled ceramic particles instead of in-situ precipitated particles is poorly studied. In this work, the effects of WC additions on the microstructure evolution and strengthening mechanism of additive-manufactured HEA samples at both room temperature (298 K) and cryogenic temperature (77 K) were systematically investigated. Except for the representative hierarchical microstructure characteristics of 3D printed- HEA samples, WC particles are dissolved completely in the CrMnFeCoNi matrix without obvious element segregation. The mechanical tests at room temperature (RT) revealed an excellent comprehensive mechanical property (tensile strength of 925 MPa and ductility of 38%) of the HEA sample with 5 wt% WC addition, which is mainly attributed to the solid solution strengthening induced by WC dissolution. In addition, the strength and ductility of the HEA sample synchronously increase when the testing temperature decreases from 298 K to 77 K, due to the reaction between dislocation and high-density deformation twins (DTs). The tensile strength (∼1420 MPa) of HEA-5 wt% WC sample at 77 K is higher than that of traditional CrMnFeCoNi HEA, because of contribution to strengthening from dislocation pile-up, entanglement and wavy dislocation slide.

AlCoCrFeMo0.05Ni2 high-entropy alloy (HEA) has great potential for high-temperature applications. However, its FCC matrix will decompose during annealing, which seriously limits its high-temperature applications. Here, the lattice distortion, Gibbs free energy change, phonon spectra, density of states, and bond length distribution of the FCC matrix were calculated by first-principles calculations. The findings indicate that the primary barrier to the formation of a single homogeneous solid solution in the alloy is more closely associated with Gibbs free energy rather than the degree of lattice distortion. The vibration frequency of Al is not in sync with the overall structure, making it prone to desolvation at elevated temperatures. Furthermore, an analysis of bond lengths reveals that the Al–Ni bond length is significantly shorter than the theoretical value, facilitating the formation of a (Ni, Al)-rich phase. In contrast, the longer bond lengths of Al–Cr and Al–Mo facilitate the detachment of Cr and Mo from the (Ni, Al)-rich phase, resulting in the formation of (Cr, Mo)-rich phase. This in-depth investigation sheds light on the phase decomposition mechanism of high-entropy alloys, offering valuable insights for future research in this field.

The Co–Cr–Cu–Fe–Ni–Zn compositional library was studied on a combinatorial high-entropy alloy thin film processed on a silicon substrate by magnetron sputtering technique. The thickness of the coating was between 2 and 3 μm while the lateral dimension was 10 cm. The chemical composition in the layer depended on the location and for each constituent element the concentration varied between 5 and 42 at.%. The phase composition and the microstructure were mapped using synchrotron X-ray diffraction, and the crystallite size as well as the density of lattice defects (dislocations and twin faults) were determined by diffraction line profile profile analysis. In addition, selected locations were studied by transmission electron microscopy. The influence of the chemical composition on the microstructure and the mechanical behavior was revealed. The mechanical performance was characterized by nanoindentation mapping which determined the hardness and the elastic modulus versus the element concentrations. It was found that the coating contains single phase face-centered cubic (FCC) and body-centered cubic (BCC) regions as well as an intermediate two-phase area. In the whole combinatorial sample, the microstructure consisted of nanocrystalline columns growing perpendicular to the coating surface and having pores between them. Due to the porosity, the hardness and the elastic modulus were relatively low despite the nanostructure and the very high defect density. The highest hardness (3.4 GPa) and elastic modulus (119 GPa) were measured in the BCC region with the chemical composition of 10%Co–38%Cr–13%Cu–27%Fe–5%Ni–7%Zn (at.%).

ABSTRACTThe Hall-Petch strengthening coefficient of face-centered cubic alloys has the potential to increase. Herein, we experimentally determined an unconventionally large Hall-Petch coefficient equal to 1100 MPa·µm1/2 and a large lattice friction stress for novel Co0.95Cr0.8Fe0.25Ni1.8Mo0.475 high-entropy alloys (Mo0.475 HEAs). Detailed microstructural characterizations showed Mo segregation at grain boundaries (GBs) and no apparent nano-clustering in the matrix. With the increased Mo content, Mo segregating at GBs is an unexpected outcome. The unconventionally large Hall-Petch coefficient is ascribed to the newly generated effect due to Mo segregation at GBs, besides the factors in the grain interior, e.g. the increased solid-solution strengthening. This study is dedicated to enriching the diversity of Hall-Petch strengthening mechanisms for the development of high-strength materials.

Damping alloys can dissipate vibration energy into thermal energy through defective motion with high mechanical properties and functional characteristics， which have a great significance in the development and research of aerospace and military fields. There are differences in microstucture between different alloy systems. The types of defects that play a dominant role in damping are different， and the properties of structureal defect （type， density， and movability） are the key factors affecting the damping performance of alloys. The types and characteristics of damping source for different damping alloys systems were summarized from the perspective of defects （plane defects， line defects， and point defects）. The relationship between damping capacity， mechanical properties， and functional properties （corrosion resistance， casting performance， etc.） was reviewed， the development status of various damping alloys was summarized， and then the development laws and differences of damping alloys were concluded. Finally， the research direction of damping alloys is prospected. The single type of damping source will seriously limit the improvement of the material damping capacity. While the design concepts of composite materials and high-entropy alloys allow for the coexistence of multiple damping sources， which produces the coupling effect of multiple damping mechanisms that can realize the two-dimensional expansion of damping capacity， and improve mechanical properties and functionalities. The design concepts will play a significant guide to enhance comprehensive performance of damping alloys.

Directly electrochemical conversion of nitrate (NO3−) is an efficient and environmentally friendly technology for ammonia (NH3) production but is challenged by highly selective electrocatalysts. High‐entropy alloys (HEAs) with unique properties are attractive materials in catalysis, particularly for multi‐step reactions. Herein, we first reported the application of HEA (FeCoNiAlTi) for electrocatalytic NO3− reduction to NH3 (NRA). The bulk HEA is active for NRA but limited by the unsatisfied NH3 yield of 0.36 mg h−1 cm−2 and Faradaic efficiency (FE) of 82.66 %. Through an effective phase engineering strategy, uniform intermetallic nanoparticles are introduced on the bulk HEA to increase electrochemical active surface area and charge transfer efficiency. The resulting nanostructured HEA (n‐HEA) delivers enhanced electrochemical NRA performance in terms of NH3 yield (0.52 mg h−1 cm−2) and FE (95.23 %). Further experimental and theoretical investigations reveal that the multi‐active sites (Fe, Co, and Ni) dominated electrocatalysis for NRA over the n‐HEA. Notably, the typical Co sites exhibit the lowest energy barrier for NRA with *NH2 to *NH3as the rate‐determining step. [ABSTRACT FROM AUTHOR]

Laser bending forming, as a flexible and die-less forming approach, facilitates the three-dimensional shaping of sheets through the generation of thermal stress via laser-material interaction. In this study, the bending forming characteristics of CoCrFeMnNi high-entropy alloy sheets induced by nanosecond pulse laser irradiation were systematically investigated. The effects of parameters including laser power, scanning speed, number of scans, scanning interval, and sheet size on the bending angle, cross-sectional morphology, and hardness were studied in detail under both the laser single-line and multi-line scanning modes. The experimental results confirmed the effectiveness of nanosecond pulse laser irradiation for achieving accurate formation of CoCrFeMnNi sheets, with the successful fabrication of J, L, and U-shaped metal components. Apart from the forming ability, the cross-sectional hardness was significantly increased due to the grain refinement effect of nanosecond pulse laser irradiation. Furthermore, employing the laser single-line scanning mode enabled the effective rectification of overbending parts, showcasing complete recovery for small-angle overbending, and a remarkable 91% recovery for larger-angle overbending. This study provides an important basis for the bendability of CoCrFeMnNi sheets by laser forming and elucidates the evolution of the microstructure and mechanical properties in the bending region. [ABSTRACT FROM AUTHOR]

A multicomponent bulk nanostructured Al20Ti20Fe20Mn20Ni20 high-entropy alloy (HEA) was prepared by the powder metallurgy method. The process involved mechanical alloying of the elemental powders of equal wt% followed by cold compaction and conventional sintering in an inert atmosphere at different temperatures. The structural evaluation and morphological studies of the milled powders were carried out by HRTEM and XRD analysis. The crystal size and d-spacing of the milled powder significantly reduced with the milling duration. The effects of sintering temperatures on the microstructure, wear resistance, and the hardness of Al20Ti20Fe20Mn20Ni20 were investigated. The microstructural analysis showed that the prepared HEAs had a multiphase microstructure consisting of BCC and intermetallic compounds. As the sintering temperature grew, the microhardness and wear resistance increased, demonstrating that the properties of the current HEA were improved by using high sintering temperatures. The increase in density with sintering temperatures and the intermetallic phase contents acted as reinforcement might have enhanced the hardness of the HEA. The best hardness value and the least amount of wear were found in the sample sintered at 900 °C. [ABSTRACT FROM AUTHOR]