Search Results (1,026)

High-entropy alloys (HEAs) offer attractive combinations of mechanical performance, thermal stability, and compositional flexibility, making them promising candidates for advanced structural applications. Laser-based additive manufacturing, particularly laser powder bed fusion (LPBF) and laser-directed energy deposition (LDED), enables the fabrication of geometrically complex HEA components with non-equilibrium microstructures. However, the distinct thermal histories of LPBF and LDED, with typical cooling rates of approximately 10⁵–10⁷ K s⁻¹ and 10²–10⁴ K s⁻¹, respectively, strongly govern solidification behavior, elemental segregation, residual stress development, defect formation, and mechanical properties. Although previous reviews have discussed additively manufactured HEAs, an integrated framework linking composition design, printability, LPBF/LDED processing, microstructural evolution, post-processing, and industrial qualification remains limited. Therefore, this review establishes a unified composition–process–structure–property framework for laser additively manufactured HEAs. Fundamental HEA concepts, LPBF/LDED process characteristics, solidification behavior, phase formation, defect evolution, and mechanical performance from ambient to elevated temperatures are systematically discussed across representative FCC, refractory, and dual-phase HEA systems. This review emphasizes that printability should be considered during alloy design by correlating composition-dependent solidification characteristics, cracking susceptibility, phase stability, and defect formation with mechanical performance. Post-processing treatments are shown to modify residual stress, microsegregation, precipitation behavior, porosity, and deformation mechanisms, although their benefits must be balanced against thermal softening or brittle phase formation. Finally, CALPHAD, integrated computational materials engineering (ICME), machine learning (ML), and in situ monitoring are identified as promising tools for accelerating alloy and process optimization, while reproducible process windows, defect-control criteria, databases, and qualification protocols remain essential for industrial implementation. Full article

In-situ alloying during laser powder bed fusion (LPBF) offers great compositional flexibility but is prone to process-induced defects. To address this problem, we developed a machine learning framework to predict and minimize major defects such as porosity (inclusive of lack of fusion, gas pores, and keyhole-induced porosity) and unmelted Nb particles (partially and completely unmelted particles) in LPBF-fabricated in-situ alloyed Ti–45Nb alloy. For this purpose, two independent least-squares boosting (LSBoost) ensemble regressors were trained using five process parameters (part shape, laser power, scan speed, hatch spacing, and scan rotation), along with their polynomial and interaction terms, to capture nonlinear relationships. Under a restricted 4-fold cross-validation, these models achieved pooled out-of-fold R² values of 0.672 for porosity and 0.702 for unmelted Nb, despite being trained on a small dataset. The grouped permutation importance analysis revealed that porosity is primarily governed by hatch spacing and laser power, whereas unmelted Nb particles are primarily governed by laser power and scan speed. The models were implemented in two graphical interfaces: a forward predictor for real-time defect estimation and an inverse optimizer for identifying low-defect parameter sets. Together, they establish a unified, data-driven approach for defect-aware process detection, prediction, and optimization in in-situ alloyed systems, offering a pathway towards reproducible, low-defect additive manufacturing. Full article

Constructing core–shell structured carbon-coated alloy nanoparticles represents an effective strategy to enhance the electrocatalytic performance. In this work, CoFe-based Prussian blue analogs (PBAs) with hollow structures are firstly coated with phenolic resin via the in situ polymerization method. A subsequent carbonization treatment yields N-doped carbon-encapsulated CoFe alloy nanocubes (denoted as CoFe-NC@C). The carbon shell suppresses the structural collapse and particle aggregation of CoFe nanocubes while enhancing the electrical conductivity, thereby facilitating fast reaction kinetics. Meanwhile, the etching-induced hierarchical pore structure increases the specific surface area with a Brunauer–Emmett–Teller (BET) value of 57 m² g⁻¹, which exposes more accessible active sites and facilitates mass transport. Owing to the synergistic effect between the two components, the CoFe-NC@C catalyst exhibits an outstanding oxygen evolution reaction (OER) performance in an alkaline electrolyte, achieving a low overpotential of 278 mV (vs. RHE) at a current density of 10 mA cm⁻² along with superb durability. This work demonstrates that the OER performance of PBA-derived alloys can be boosted through an integrated strategy of etching and carbon coating. Full article

The anisotropic permeability tensor governs interdendritic fluid flow and solute transport during the directional solidification of metallic alloys, fundamentally influencing crystal growth kinetics and microstructural evolution. Traditional scalar models, notably the Kozeny–Carman equation, are fundamentally limited by isotropic assumptions that contradict the inherent anisotropy of dendritic microstructures and preclude description of microstructure–transport coupling. Recent advances in multiscale computational crystal growth modeling, integrating phase-field simulations of dendritic morphology, lattice Boltzmann calculations of interdendritic flow, and synchrotron X-ray tomography for in situ microstructural characterization, have enabled tensor-resolved quantification of permeability evolution, yet the dynamic feedback between solid skeleton deformation and permeability remains poorly understood. This work establishes a critically assessed mechanistic framework coupling dendritic microstructure evolution, anisotropic permeability tensor dynamics, and solidification transport phenomena. By explicitly addressing the hitherto unresolved dynamic feedback between solid skeleton deformation and permeability, this review provides a theoretical foundation and a conceptual framework for future predictive modeling for solidification microstructure control, offering fundamental insights into the physics of crystal growth and interdendritic transport in metallic systems. Full article

Lunar in situ resource utilization requires solar concentrating systems that can be launched in a compact configuration and deployed reliably on the lunar surface. This paper presents a multi-link coupled deployable support mechanism for a reflector-Fresnel concentrating system. The mechanism adopts a shape-memory-alloy rigid release for the stowed state and passive spring hinges for autonomous deployment, aiming to reduce drive complexity while maintaining a high deployment ratio. To avoid interference caused by coupled link motion, a motion-envelope model is established for joint trajectory planning. The deployment process is then analyzed through vector-based kinematic modeling, D’Alembert force analysis, and Lagrange dynamic equations. The analytical predictions are corroborated through high-fidelity multibody dynamic simulations: the predicted driving torque of Link 3 is 0–0.68 N⋅m, close to the simulated range of 0–0.70 N⋅m, with a relative peak-value error of 2.8%; the maximum angular acceleration is 0.08 rad/s². Finite-element modal analysis gives a first locked-state natural frequency of 54.969 Hz. NSGA-II optimization further reduces the maximum driving torque by 10.9%, reduces torque fluctuation by 9.7%, and increases the maximum deployment ratio from 5.6 to 7.2. The results provide a quantified design and simulation basis for passive deployable concentrating mechanisms intended for lunar surface concentrating systems. Full article

The degradation of organic pollutants through photocatalysis is currently a major research focus. Core–shell heterostructures of metal semiconductors have been widely recognized as an effective strategy for enhancing photocatalytic performance, particularly when alloy nanoparticles are incorporated due to their unique electronic and catalytic properties. However, conventional synthetic approaches typically rely on high-temperature and high-pressure conditions, which often induce undesirable particle overgrowth and aggregation. Herein, AuPt bimetallic alloy nanoparticles were successfully fabricated via two successive in situ redox processes under room-temperature and ambient-pressure conditions, which were in situ integrated with Cu₂O to form multilevel core–shell composite particles. Structurally, an octahedral Cu₂O crystal serves as the inner core (denoted as Cu₂O_(O)), sequentially coated with a Cu₂O nanoparticle (denoted as Cu₂O_(P)) interlayer and a AuPt alloy nanoparticle shell. Functionally, the enhanced photocatalytic activity of Cu₂O_(O)@Cu₂O_(P)@AuPt was proven to be attributed to a dual function of AuPt, which includes an adsorption-induced polarized interface and an efficient charge-transfer mediator with the ohmic contact. This work demonstrates a mild and versatile synthetic strategy for constructing semiconductor–alloy heterostructures, offering valuable insights into the rational design of highly efficient and stable photocatalysts. Full article

The thermal stability and devitrification pathway of melt-spun high-entropy Cr₁₆Mn₁₆Fe₁₆Co₁₆Ni₁₆P₂₀ metallic glass were investigated using transmission electron microscopy/selected-area electron diffraction (TEM/SAED), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and ⁵⁷Fe Mössbauer spectroscopy. TEM/SAED confirmed an amorphous ribbon structure, with diffuse rings and radial maxima at k₁ = 0.84799 nm⁻¹ and k₂ = 1.44459 nm⁻¹. Non-isothermal DSC revealed two exothermic events, Peak I at ~716–752 K and Peak II at ~881–930 K, both shifting to higher temperatures with increasing heating rate. Kissinger analysis yielded apparent activation energies of Ea₁ = 359.2 kJ/mol for Peak I and Ea₂ = 414.9 kJ/mol for Peak II. Specimens heated in the DSC under argon at 20 K/min to selected target temperatures were examined ex situ. The XRD patterns are consistent with the onset of crystallization during Peak I, with reflections tentatively attributed to an Fe₃P-type phase and an FCC solid solution. Peak II is associated with further phase evolution, including the development of reflections compatible with MnNi-type and Co₂P-type phases. Because of peak overlap in this multicomponent alloy, the proposed phase sequence should be regarded as a plausible interpretation based on combined DSC, XRD, and Mössbauer evidence rather than as a uniquely resolved quantitative phase analysis. Mössbauer spectra reveal three paramagnetic Fe environments. With increasing DSC target temperature, the high-QS Fe3 component, representing a highly distorted Fe environment, decreases systematically, whereas the low-QS Fe1 component, associated with a more symmetric, nearly cubic Fe environment, becomes dominant. The high apparent activation energies indicate a larger effective kinetic barrier than in many simpler transition-metal–phosphorus amorphous alloys. Full article

The macroscopic mechanical properties of near-β titanium alloys depend inherently on their complex microstructural morphologies and phase transformation kinetics. This study investigates the deformation behavior of a lamellar Ti-55531 alloy during isothermal compression and in situ tensile testing. Pronounced strain rate sensitivity dictates the deformation of the lamellar microstructure. Low strain rate deformation (0.001 s⁻¹) induces dynamic recovery and recrystallization, which in turn drive α-lamellae fragmentation and the nucleation of new α phase during compression. The α precipitation is governed by a strict Burgers orientation relationship (BOR), but extensive plastic deformation may lead to the breakdown of the BOR. During tension, continuous slip transfer between adjacent phases is critically restricted by α/β interfacial thickness. As plastic strain accumulates, lath-like, V-shaped, and acicular α phases precipitate concurrently within β grains, creating a complex α microstructure. Full article

ZIF-8-modified micro-arc oxidation (MAO) coatings have attracted considerable attention for improving the corrosion resistance of aluminum alloys, owing to their combined barrier and chemical protection effects. In this work, ZIF-8/MAO composite coatings were fabricated via in situ solvothermal growth, and the effects of solvothermal temperature and time on coating evolution and corrosion performance were systematically investigated. The coatings were characterized by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The results show that increasing the solvothermal temperature promotes ZIF-8 formation, which may be related to enhanced coordination reactions and particle growth. Prolonging the solvothermal time induces a transition from ZnO-dominated coatings at 8 h to ZIF-8-dominated structures at 16–24 h, whereas unconverted ZnO is still detected after prolonged growth. The in situ-grown ZIF-8 particles cover the MAO surface and contribute to the sealing of surface micropores and cracks, forming a more compact composite barrier structure. The reduced coating performance at 220 °C or after 32 h may be associated with excessive particle refinement, local structural imperfections, or reduced coating integrity under prolonged or high-temperature solvothermal conditions. Electrochemical impedance spectroscopy (EIS) results reveal that the composite coating exhibits a charge transfer resistance more than one order of magnitude higher than that of the bare MAO coating, indicating significantly enhanced barrier protection. These findings demonstrate that in situ-grown ZIF-8 is an effective strategy for improving the corrosion resistance of MAO coatings on aluminum alloys. Full article

Smart manufacturing requires real-time monitoring of multidimensional forces at the interface between the tool and workpiece in computer numerical control (CNC) machining. In this study, an innovative iKIT wireless extrasensory toolholder is introduced that is capable of high-fidelity, in situ, high-frequency sensing and monitoring of the cutting force, torque, and two-way bending moments. The hardware design of the system is outlined, highlighting a high-bandwidth miniature wireless transmission method and noncontact power supply and energy storage solution suitable for rotating machining environments. To assess the system performance, comprehensive milling tests were performed on aluminum alloy materials, and the relationship between the process parameters and changes in multidimensional mechanical loads was thoroughly examined. The experimental findings demonstrate that the smart toolholder detects precisely how parameter variations affect the loads. Multidimensional mechanical signals (torque and two-way bending moments) show a strong positive correlation with the feed rate and axial depth of cut, confirming the impact of the material removal rate on the system loads. Conversely, these signals are negatively correlated with spindle speed, accurately reflecting the effects of thermal softening and a reduced friction coefficient in aluminum alloys during high-speed cutting. This study not only offers a dependable hardware framework for integrating miniaturized sensors into toolholders, but also delivers accurate data to support digital twin models and adaptive control in machining processes. Full article

This study investigates the influence of cold-working deformation on the electromotive force (EMF) calibration characteristics, hysteresis behavior, and long-term stability of the Type-K mineral-insulated metal-sheathed (MIMS) thermocouples used in Combination Fixed In-Core Detector Assemblies for pressurized water reactor nuclear power plants. Reduction ratios of 12%, 28%, and 38% were investigated, and samples were subjected to heating–cooling calibration and in situ aging tests. The results show that increased cold-working deformation leads to greater negative EMF deviation and larger heating–cooling hysteresis, mainly affected by the degradation of the positive KP thermoelement. Cold-working lowers the atomic diffusion activation energy and accelerates element migration, resulting in pronounced EMF drift during isothermal aging at 350 °C for 720 h. After aging below the order–disorder transition temperature, stable ordered structures form in the thermoelement alloys and hysteresis is significantly reduced. However, within the range investigated in this study, deformation above 28% imparts irreversible effects. The EMFs of 28% and 38% deformed samples remained lower than that of the undeformed state even after isothermal aging at 700 °C for 500 h. These findings reveal that excessive cold-working deformation severely impairs the measurement accuracy and long-term stability of the thermocouples, highlighting the necessity of the strict control of drawing deformation to ensure the reliability of nuclear-grade thermocouples under both normal and abnormal reactor operating conditions. Full article

CoCrFeNi/WC-Nb high-entropy alloy (HEA) composite coating was prepared on the surface of Q235 steel by LC (laser cladding) technology, and the effects of WC and in situ NbC reinforcement on the coating were studied. The phase composition, phase characteristics, microhardness, and wear resistance of the cladding coatings were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), friction and wear tester, and X-ray photoelectron spectroscopy (XPS), and the corrosion resistance was tested by a three-electrode electrochemical workstation. The results show that the CoCrFeNi/WC-Nb HEA coating consists of FCC, WC, NbC, and Laves phases, and the reinforcing phase causes grain refinement and lattice distortion. The microhardness reached (418.29 ± 16.72) HV, which was about 2.64-times higher than that of the CoCrFeNi HEA coating. The wear rate decreased to (1.150 ± 0.11) × 10⁻⁴ mm³N⁻¹m⁻¹, which was about 0.25 times that of the CoCrFeNi HEA coating, and the wear of the coating changed from abrasive wear to adhesive wear. The corrosion current density and corrosion voltage of the CoCrFeNi/WC-Nb HEA coating are (3.3820 ± 0.2103) × 10⁻⁶ A/cm² and −(0.7650 ± 0.0850) V, respectively. Full article

Sodium (Na) metal anodes suffer from poor processability, severe volume fluctuation, unstable interfacial chemistry, and uncontrolled dendrite growth during cycling, which significantly hinder their practical application. Herein, a Na/Na₂In composite foil is fabricated through an in situ spontaneous alloying reaction enabled by a simple rolling–folding process using Na and indium (In) foils as precursors. Structural characterizations confirm the complete conversion of metallic In into the Na₂In alloy phase, forming a continuous architecture with uniformly distributed Na₂In networks embedded within the Na matrix. Owing to the sodiophilic and mechanically robust Na₂In framework, the Na/Na₂In composite anode effectively regulates Na plating/stripping behavior and suppresses dendritic growth, thereby maintaining a dense and stable electrode morphology during repeated charge/discharge processes. As a result, the Na/Na₂In symmetric cell exhibits stable cycling for over 900 h at 0.5 mA cm⁻² and 1 mAh cm⁻² with low polarization hysteresis, whereas the pure Na counterpart fails after only 143 h. Moreover, full cells paired with NaFe_1/3Ni_1/3Mn_1/3O₂ cathodes deliver enhanced cycling stability, retaining 87% of the initial capacity after 100 cycles at 0.5 C, together with improved rate capability. This work demonstrates a scalable mechanical fabrication strategy for high-stability Na metal composite anodes and provides new insights into the practical development of high-energy-density Na metal batteries. Full article

xAl₃Zr/Al-5Cu-0.6Mn-0.15Ti composites were fabricated via an in situ reaction method, and the influence of Al₃Zr content on the microstructure and mechanical properties in both as-cast and T6-treated conditions was systematically investigated. The results reveal that the D0₂₃-Al₃Zr content increases in proportion to the K₂ZrF₆ addition level. Following T6 heat treatment, finely dispersed θ′-Al₂Cu precipitates were formed within the matrix, and the α-Al + θ-Al₂Cu eutectic network dissolved. The blocky Al₃Zr particles underwent spheroidization and could continuously exert a grain boundary pinning effect to suppress grain coarsening. After T6 heat treatment, the 4.5 wt.% Al₃Zr composite exhibited average ultimate tensile strengths of 324.44 MPa at room temperature and 123.38 MPa at 350 °C, corresponding to improvements of 8.56% and 23.31%, respectively, relative to the unreinforced base alloy. Following thermal exposure at 350 °C for 24 h, the composite exhibited less pronounced coarsening of the θ′-Al₂Cu precipitates compared with the base alloy, while the Al₃Zr particles retained their morphological and dimensional stability. Consequently, the reductions in both tensile strength and hardness were smaller than those observed for the base alloy. Analysis indicates that Al₃Zr particles significantly refine the α-Al grains and enhance the alloy’s thermal stability. The superior property retention is attributed primarily to the high thermal stability of the Al₃Zr particles, which preserve their dispersion-strengthening contribution at 350 °C, with the reduced θ′ coarsening as a contributing factor. The overall strengthening of the composite arises from the combined and largely independent contributions of Al₃Zr particle strengthening and θ′-Al₂Cu precipitation strengthening. Full article

Plasma electrolytic oxidation (PEO) has emerged as a leading surface engineering technology for improving the tribological and corrosion performance of lightweight structural alloys, including aluminum, magnesium, titanium, and zirconium. Unlike conventional anodizing or line-of-sight deposition processes, PEO forms thick, multiphase ceramic oxide coatings metallurgically bonded to the substrate through plasma-assisted in situ oxidation, enabling treatment of complex and internal geometries that competing technologies cannot reach. The tribological performance of PEO coatings is governed by coupled interactions among electrolyte chemistry, electrical discharge behavior, phase evolution, porosity development, and residual stress state. This review critically evaluates the friction, wear, and tribo-corrosion behavior of PEO coatings under dry sliding, lubricated, high-temperature, marine, and vacuum environments, and systematically examines the influence of processing parameters, microstructural evolution, transfer layer formation, and counterface interactions on coating performance. Hybrid and duplex systems incorporating solid lubricants, polymer impregnation, sol–gel sealing, and multilayer architectures are discussed as strategies to overcome limitations associated with brittleness and surface porosity. Current research challenges, including fatigue degradation, coating defect control, limited cross-study standardization, and incomplete mechanistic understanding of process–microstructure, tribological relationships, are critically assessed. Emerging directions encompassing self-lubricating adaptive coatings, AI-guided process optimization, and multifunctional hybrid architectures are highlighted as pathways toward next-generation surface systems. This review provides a mechanism-based framework for understanding tribological behavior in PEO coatings and identifies critical opportunities for future industrial implementation in aerospace, automotive, marine, biomedical, and energy applications. Full article