Vacancy-solute complexes play a crucial role in the precipitation process of aluminum alloys. however, in-depth investigations of solute-vacancy complexes remain limited. Positron annihilation spectroscopy has unique advantages for probing vacancy-type defects, which can identify vacancy-type defects and characterize the surrounding chemical signatures. In this work, positron annihilation spectroscopy and first-principles calculations are employed to investigate the vacancy-solute complexes in Al-Cu alloys microalloyed by Sc and rolled at different temperatures. We successfully identify multiple V5 (five vacancies)-solute complexes, including V5Cu1, V5Sc1, and V5Cu1Sc1, which act as mediators linking Sc microalloying and rolling temperature to precipitation behaviors. The evolution pathways of V5-solute complexes during artificial aging and the influences of vacancy-solute complexes on precipitation behaviors in Al-Cu alloys are systematically investigated. This work offers new insights for the roles and configurations of vacancy-solute complexes in aluminum alloys.

Atomistic understanding of metallic uranium (U) corrosion remains limited, largely because no reactive interatomic potential has been available to capture the complex bonding events governing oxidation. Here, we develop the first reactive force field (ReaxFF) for the U-O-H system, parameterized against an extensive dataset covering metallic U and its oxides and hydrides. The potential reproduces key thermodynamic and structural properties and captures the temperature-driven alpha-U -> gamma-U transformation. Using this force field, large-scale ReaxFF molecular dynamics simulations were performed to resolve the oxidation kinetics of the alpha-U(001) surfaces in dry and humid O2 atmospheres. The simulations reproduce the experimentally observed regimes, including linear oxidation in dry O2, parabolic oxidation at a water vapor mole fraction of 12.5%, and a linear-to-parabolic transition at 6.25% water vapor. Mechanistic analysis shows that although less than 40% of H2O is consumed, its catalytic dissociation generates *OH species that coordinate strongly with U atoms, promote dispersed U-O cluster formation, and restructure the oxide layer. This restructuring yields a rough, porous oxide layer that sustains parabolic oxidation in humid atmospheres. These results provide atomistic evidence for the humidity-dependent uranium oxidation (where the humidity level refers to the gas-phase water vapor mole fraction, which is not equivalent to experimental relative humidity) and establish a transferable U-O-H reactive force field for corrosion modeling in nuclear materials.

Designing thermoelectric materials that combine high conversion efficiency with mechanical robustness remains challenging-especially in metavalent-bonded chalcogenides, where weak bonds yield intrinsically low lattice thermal conductivity yet compromise mechanical integrity. Here we present an entropy-enabled defect architecture in SnTe-based alloys that steers hierarchical defect evolution-from 0D substitutional clusters to 1D dislocations and 3D coherent nanoprecipitates-enabling multiscale regulation of phonon transport and strengthening mechanisms. Broadband phonon scattering depresses lattice thermal conductivity to 0.26 W·m-1·K-1 at 873 K, while coherent (Cd,Ge)Se nanoprecipitates and dislocation networks establish effective load-transfer and pinning pathways, elevating the yield strength to 220 MPa, an improvement of ∼100 MPa (≈83%) relative to pristine SnTe (120 MPa), while retaining reasonable plasticity. In parallel, modest band-structure optimization through compositionally complex alloying within the entropy-stabilized matrix improves the power factor. Benefiting from these synergies, the optimized composition Sn0.91Cd0.03Sb0.09Te(GeSe)0.25 delivers a peak figure of merit of 1.7 and device efficiencies of 7.2% (single-leg) and 5.7% (multi-leg). This work establishes a generalizable pathway to strong, efficient thermoelectric materials, particularly applicable to metavalent bonding systems.

Polyoxometalates (POMs) are ideal preassembled platforms for constructing transition metal catalysts because they are rich in oxygen and transition metal elements. In contrast to traditional methods for preparing V2O5/MoS2 composite catalysts, the method proposed in this study leverages the selective preference of vanadium for oxygen vs. sulfur. A MoS2-based electrocatalyst composited with a small amount of V2O5 was constructed in situ on a carbon cloth via a one-pot hydrothermal method using a Lindqvist-type POM, i.e., (C16H36N)2 Mo3V3O16(OCH2)3CCH2CH3 (Mo3V3), as a precursor. This catalyst was used for efficient electrocatalytic hydrogen evolution reaction. The experimental results reveal that the introduction of a small amount of V2O5 considerably increases the electrochemically active surface area of the catalyst, effectively enhancing the catalytic performance of the material. This study provides a new design strategy and synthetic pathway for precise construction of high-performance composite electrocatalysts based on POM precursors.

Achieving both large work output and low thermal hysteresis in TiNi-based shape memory actuators remains challenging due to their inherent trade-off: the B2-B19 ' martensitic transformation provides large transformation strain but high thermal hysteresis, while the B2-B19 transformation yields low thermal hysteresis but limited strain. Here, we propose a design strategy to target compositions near the phase crossover between B19 ' and B19 martensites, where both phases can coexist. Combined with machine learning-assisted multi-objective optimization of processing conditions, this approach led to the development of a Ti50Ni41.3Cu8Hf0.3Co0.4 alloy exhibiting a low thermal hysteresis about 10 degrees C and a work output exceeding 30 MJ/m3, outperforming most TiNi-based shape memory alloys. The finely tuned composition improves lattice compatibility to reduce thermal hysteresis, while the B2-B19 ' transformation occurred under actuation stress enables large recoverable strain. Additionally, grain refinement and residual dislocations enhance strength, thereby enabling the alloy to realize its full work output potential. This strategy, which integrates phase diagram insights with data-driven materials design, provides an efficient pathway for discovering new phase-change materials with superior functional performance.

In this study, a self-developed additive manufacturing technique, known as rotary spray deposition, was employed to uniformly deposit twin-rich Ag coatings onto Cu surfaces. The impact of the key deposition parameters, including spray distance, flow rate, and duration, on the surface morphology and thickness of the Ag coatings was meticulously investigated to achieve exceptionally high-quality coatings. These coatings exhibited a low resistivity of 1.711 x 10-8 Q m and a high hardness of 145 HV, which was attributable to the high-density twins and stacking faults (SFs) induced by the rotary spray deposition process. Subsequently, nanolamellar structures were produced on the trilayers under extreme machining conditions of current-carrying friction, aided by the use of lubricating oil (polyalphaolefin). The tribological behavior and wear mechanisms of the Ag coatings were systematically examined to determine the optimal load and current parameters for the effective formation of nanolamellar structures within the optimally worn subsurface microstructures. The primary formation mechanism was identified as sliding-induced dynamic deformation, characterized by high strain rates and strain gradients during the current-carrying friction machining process. Moreover, the nanolamellar structures demonstrated a remarkable ability to absorb the stress and strain arising from the current-carrying friction process, thereby enhancing the wear resistance of the Ag coatings. As a result, this technique is anticipated to pave new pathways for the development of nanolamellar structures and high-strength metallic materials. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

The demand for alloys capable of withstanding extremely high temperatures has grown significantly in the aerospace industry. The alloys need to maintain sufficient strength at ultra-high temperatures, while still having adequate forming ability to manufacture the hot-end components. Refractory alloys, including refractory medium- and high-entropy alloys, have been widely recognized as the promising candidates to operate in extreme environments. This review aims to comprehensively assess the mechanical properties of ductile refractory alloys over a broad temperature range. We first present the fabrication methods available for preparing bulk refractory alloys. Several important topics regarding their mechanical properties are then discussed, such as ductile-to-brittle transition, strength-ductility trade-off at room temperature, and high-temperature tensile strength and creep resistance. We also summarize the toughening and strengthening strategies often used towards strength-ductility synergy in refractory alloys. The catastrophic oxidation at elevated temperatures, another critical issue for limiting their widespread applications, is further discussed briefly. Finally, this overview provides an outlook on the challenges and perspectives in this cutting-edge field.

Low thermal expansion and high thermal conductivity are essential for advanced integrated circuit packaging materials. In this study, an isotropic negative thermal expansion fluoride, Ca0.85Sr0.15SnF6 (CSSF), exhibiting a linear coefficient of thermal expansion, alpha l of -7.3 & times; 10-6/degrees C, is synthesized via a hydrothermal method. TEM results capture the diverse lattice distortion in CSSF, including attractive Moir & eacute; fringe, dislocations, and obvious lattice strain. Subsequently, CSSF is introduced into epoxy resin (EP) to design the unconventional CSSF/EP composites. Compared with the pure epoxy, the composite with 60 wt.% CSSF filler exhibits a significant reduction in alpha l, from 69.5 & times; 10-6/degrees C (glassy region) and 172.0 & times; 10-6/degrees C (rubbery region), down to 35.8 & times; 10-6/degrees C and 87.4 & times; 10-6/degrees C, respectively. Meanwhile, the thermal conductivity increases from 0.19 to 0.48 W & centerdot;m-1 & centerdot;degrees C-1. Moreover, a higher Shore hardness (93.3 HD) is achieved for the CSSF60/Epoxy composite. Furthermore, the composite demonstrates desirable dielectric properties, with a dielectric constant of 9.48 and a dielectric loss of 0.166 at 1 MHz. In particular, fracture surface analysis reveals that CSSF filler achieves strong interfacial adhesion with the epoxy matrix without surface treatment, which can be attributed to its isotropic nature. This unconventional strategy of incorporating NTE fluorides into EP presents a viable approach for advanced electronic packaging applications.

Ta-based refractory alloys offer excellent high-temperature strength, but high W content significantly reduces room-temperature tensile ductility. Here for Ta-14W alloy with fracture strain of similar to 5%, we demonstrate that a minor Hf addition significantly improves its ductility to over 30%. Firstly, Hf induces an asymmetric core structure of screw dislocation and reduces generalized stacking fault energy (GSFE), thereby promoting dislocation mobility and dislocation multiplication during plastic deformation. Secondly, Hf can strengthen grain boundaries (GBs) by preferentially segregating near GBs. Thirdly, Hf binds with O atoms to form HfO2 particles at GBs, lowering the risk of oxygen embrittlement. All these mechanisms offer insightful guide for the development of advanced Ta-W-based refractory alloys. [GRAPHICS]

To overcome the brittleness in high-strength metastable beta titanium alloys, a novel thermomechanical processing route combining hot rolling and dual-step aging was applied to a Ti-4Al-5Mo-5V-5.5Cr-1Nb alloy. By combining hot rolling with a dual-step aging treatment, a high density of sub-grain boundaries and low-angle grain boundaries were introduced, effectively partitioning the prior beta grains. Coupled with the synergistic effects of embryonic omega phase and spinodal decomposition, this approach enabled the uniform precipitation of nanoscale secondary alpha phase (alpha s) both near grain boundaries and within grain interiors. The resulting homogeneous microstructure successfully suppressed strain localization and intergranular fracture. Consequently, the processed alloy achieved an exceptional combination of an ultra-high tensile strength of 1648 MPa and a significantly enhanced ductility of 7.1 % elongation. This work provides a new pathway for designing metastable beta titanium alloys with superior strength-ductility synergy.

Accurate prediction of both the Widmansta & uml;tten start (Ws) temperature and the transformation stasis requires a quantitative description of the energy barrier governing the growth of Widmansta & uml;tten ferrite. In this study, a concise model is developed by explicitly distinguishing the energy barriers associated with lengthening and thickening. The model adopts the lengthening barrier attributed to curvature and strain energies, and further incorporates the thickening barrier caused by strain energy, together with the diffusional dissipation of substitutional solute. The Ws temperature is predicted by the condition under which the energy barriers for both lengthening and thickening can be overcome, while transformation stasis occurs when the thickening barrier becomes insurmountable due to progressive carbon enrichment of untransformed austenite. The new model enables accurate prediction of the Ws temperatures across Fe-xC and Fe-0.1C-xMn/Ni/Si/Cr/Mo systems and the carbon enrichment in austenite at stasis in Fe-C-Mn and Fe-C-Mn-Si alloys.

Ti80 (Ti-6Al-3Nb-2Zr-1Mo) alloy, as one of the most promising titanium alloys in marine engineering, is increasingly being considered for use in critical components. Large-scale structural components fabricated from this alloy typically undergo stress relief annealing during the manufacturing process and are subjected to various dynamic loading conditions in service. In this study, origin of stress-relief annealing-induced embrittlement is systematically investigated in Ti80 alloy with representative equiaxed and bimodal microstructures. Instrumented Charpy impact tests reveal a significant and comparable degradation of impact toughness from similar to 100 J in the solution-treated specimens to similar to 60 J in the annealing specimens, without notable dependence on microstructural morphology. Analysis of the impact load-displacement curve indicates that the reduction in crack propagation energy is the primary contributor to the overall decline in impact absorption energy. Further microstructural characterization shows that the degradation of impact toughness is not associated with changes of primary alpha phase (alpha(p)) and transformed beta matrix (beta(t)) morphologies, but rather results from the dispersed precipitation of nanoscale alpha(2) ordered phase within the alpha(p) particles during annealing. The dense formation of the alpha(2) nanoprecipitates triggers planar slip, intensifies strain localization, and induces premature microvoid nucleation at alpha(p)/beta(t) interfaces, thereby leading to the deterioration of impact toughness. A designed experimental treatment further confirms that the impact toughness can be effectively restored upon dissolution of the alpha(2) nanoprecipitates in the annealing specimens. These findings elucidate the underlying mechanism responsible for the deterioration of impact toughness in post-annealed Ti80 components used in practical applications, and provide microstructure-based guidance for enhancing the impact toughness of near-alpha and alpha+ beta titanium alloys.

The enhancement of mechanical properties is crucial for the development of tungsten (W) alloys as structural materials in critical applications. In this work, boron nitride nanosheets (BNNSs) reinforced W-5 wt% Re alloy with high strength was fabricated by hot-pressing sintering followed by hot rolling. Most of BNNSs were wellretained and WN nanolayer was formed around BNNSs via in-situ reaction partially, resulting in improved interfacial adhesion. In addition, the in-situ nanoscale WB particles uniformly distributed within W grains, exhibiting coherent interfaces with the matrix. The microhardness of BNNSs reinforced W-5 wt% Re alloy is 532.4 HV0.3. At 200 degrees C, the ultimate tensile strength (UTS) of BNNSs reinforced W-5 wt% Re alloy is 1277 MPa (53.9 % higher than W-5 wt% Re alloy), indicating markedly higher strength compared with those reported in particles dispersion-strengthened W alloys, while the total elongation (TE) remains a value of 8.9 %, which is 85.4 % higher than that of W-5 wt% Re alloy. Microstructural characterization and quantitative analysis reveal that the enhanced strength is attributed to synergistic effect from heterogeneous particle strengthening (intergranular submicron BNNSs and intragranular nanoscale WB), coherent strengthening from in-situ formed interfaces and fine-grain strengthening.

Recently, Mg-based shape memory alloys (SMAs) have emerged as the most promising candidate for developing lightweight SMAs. However, challenges such as limited temperature window for superelasticity (SE) persist, prompting the investigation of new lightweight SMAs suitable for application scenarios with significant temperature fluctuations. In this work, a novel Mg-17.8Sc-1.3Gd ternary alloy exhibiting heterogeneous grains from 40 to 710 mu m with random texture were prepared by deformation and cyclic heat treatment (CHT). The polycrystalline alloy showed the maximum superelastic strain (epsilon SE) of 2.6 % obtained at 153 K. Besides, the alloy possessed narrow stress hysteresis (sigma hys) of approximately 80 MPa at 153 K. It is worth noting that the SE over a wide temperature range from 153 K to 323 K coupled with a small superelastic stress variation of 0.34 MPa K- 1 was achieved in the Mg-17.8Sc-1.3Gd alloy. Furthermore, the Mg-17.8Sc-1.3Gd alloy shows excellent cyclic stability of SE, with a stable recoverable strain epsilon R of approximately 3.8 % over 30 loading-unloading cycles at 253 K. Also, a epsilon R of approximately 3.1 % was retained even after 30 cycles at a relatively high temperature of 323 K. Such excellent wide-temperature-range-SE in Mg-17.8Sc-1.3Gd alloy was attributed to the solid-solution strengthening and fine-grained strengthening effects induced by Gd doping. This work may guide further optimization of lightweight Mg-based SMAs with high-performance SE.

Metal-film-based conductors are an important element of flexible electronic devices. However, they typically suffer from fatigue damage and electrical degradation under cyclic deformation, which can limit practical use. Here we report fatigue-resistant metal films with a coherent gradient nanolayered architecture. The architecture consists of alternating stacked layers of silver and aluminium, with silver layers that become progressively thinner and finer grained. Initial crack nucleation is delayed by a combination of heterodeformation-induced strengthening, controlled grain coarsening in the silver layer and mitigation of interface stress concentrations. The moderate interface adhesion between silver and aluminium, and the multiaxial stress state induced by the gradient structure, also promote interface delamination and crack deflection, which suppresses fatigue-crack propagation. Our coherent gradient nanolayered silver/aluminium films exhibit a conductivity of over 107 S m−1 and relatively little conductivity change in both high-cycle, low-stress regimes (107 cycles at 0.7

The persistent coupling between lattice thermal conductivity (κL) and carrier mobility (µ) remains the central bottleneck in thermoelectric optimization: randomly distributed defects that scatter phonons inevitably degrade electron transport. This review establishes the disorder-to-order transition of crystallographic defects as a unifying design principle to overcome this trade-off. We systematically examine three defect families, including substitutional atoms, vacancies, interstitials and antisite defects demonstrate how their spatial reconfiguration from random distributions into ordered architectures fundamentally decouples phonon and electron transport. Representative examples include iso-size alloying and symmetry enhancement in substitutional systems, vacancy-derived dislocation networks and ordered vacancy layers, lattice planarization via targeted vacancy filling, and self-assembled interstitial clusters and climb dislocations. We further extend this paradigm into the mechanical domain, showing that ordered interstitials at twin boundaries simultaneously enhance mechanical strength and thermoelectric performance. A consistent conclusion emerges across all systems: performance gains arise from controlling defect spatial arrangement rather than introducing additional disorder, offering a coherent framework for the next generation of high-performance, mechanically robust thermoelectric materials.

Generative AI provides a powerful route for predicting material behavior in data-scarce regimes, an especially pressing challenge for refractory alloys where extreme processing environments and high melting points hinder large-scale data collection. Here, we introduce a Transformer-based generative framework that models the entire deformation trajectory rather than focusing solely on isolated scalar properties (such as YS, UTS), by synthesizing full stress-strain curves of Nb-W-based refractory alloys. Applied to Nb521-derived systems, the model captures the sequential evolution of tensile deformation and accurately predicts elastic-plastic responses across a wide compositional and processing space. The framework demonstrates utility in three downstream tasks: (i) inverse design of composition and processing, yielding >35% strength improvement without loss of ductility; (ii) interpretable regime analysis via a Mixture-of-Experts (MoE) mechanism, highlighting the beneficial roles of Hf and Ta in ductility, consistent with experimental and DFT validation; and (iii) seamless integration of generated curves into finite element simulations for structural performance assessment. Together, these results establish a coherent generative-analytic-predictive workflow for mechanism-aware, data-efficient design of advanced refractory alloys.

The discovery of novel carbon allotropes with tailored thermal and mechanical properties is critical for advanced thermal management. However, exploring the vast configurational space of carbon using ab initio calculations remains computationally prohibitive. Driven by the rich topological landscape of carbon, where the competition between sp, sp(2), and sp(3 )hybridization states dictates material performance, we establish a closed-loop artificial intelligence (AI) framework to explore this complex configurational space. We introduce a hybridization entropy descriptor to guide the search beyond conventional forms. Here, we establish a closed-loop AI framework that synergizes a Large Language Model (LLM) for structural generation with a Machine Learning Potential (MLP) for accelerated evaluation. Leveraging CrystaLLM to generate candidates and an iteratively refined MLP for high-fidelity validation, we screened thousands of structures to identify several stable allotropes with exotic properties. Specifically, we report "yne-diamond C-12" and "yne-hex-diamond C-8," which exhibit extreme thermal anisotropy and ultralow in-plane shear stiffness arising from their mixed sp- sp(3 )hybridization. Furthermore, we discovered a complex sp- sp(2)- sp(3 )hybridized C(12)phase that combines metallic conductivity with an anomalous negative Poisson's ratio. Notably, we identified a superhard phase (C16_3) possessing a calculated Vickers hardness (103.3 GPa) exceeding that of diamond {96 GPa [R. A. Andrievski, Int. J. Refract. Met. Hard Mater. 19, 447-452 (2001)]}. Microscopic analysis reveals that thermal transport in these materials is governed by the interplay between rigid frameworks and flexible linkers. This work expands the known carbon phase space and demonstrates the efficacy of coupling generative AI with MLPs for the accelerated inverse design of functional materials.

Surface nitriding of metallic uranium is a highly effective strategy for enhancing oxidation resistance, but atomic-scale mechanisms, particularly the role of nitrogen vacancy ordering, have remained elusive. This study addresses this gap by combining first-principles calculations with the cluster expansion method to systematically investigate vacancy-ordered structures in UN1-x and UN2-x (0 ≤ x ≤ 1). We identify eleven thermodynamically stable vacancy-ordered configurations, with high-nitrogen compounds (N/U > 1.5) exhibiting greater stability—confirmed by lower formation enthalpies—than stoichiometric phases. Electronic structure analysis reveals that the centers of the uranium 5f and 6d bands shift away from the Fermi level with increasing nitrogen content, suggesting reduced overall reactivity, while significant density of states fluctuations near the Fermi level in high-N compounds indicate localized reactive sites. In addition, these high-nitrogen UNx phases (e.g., N/U ratios of 1.40, 1.60, and 1.67) demonstrate strong oxygen interactions, with highly negative binding energies that promote oxygen incorporation into interstitial sites and the formation of stable UNxOy compounds. This mechanism, underpinned by strong oxygen binding in interstitial sites and hindered diffusion into the bulk, explains their exceptional oxygen tolerance. These findings provide atomic-level insights into the corrosion resistance of UNx structures, offering a foundation for optimizing surface nitriding technologies.

Softening of the weld zone (WZ) in fusion-welded 2024-T4 high-strength aluminum alloys has been a long-term issue, which significantly reduces mechanical properties of the joints. In this study, a post-weld heat treatment process (PWHT) was proposed and optimized to increase the tensile strength and elongation simultaneously. Experimental results demonstrated that the solution treatment has an important effect on eutectic phases and T-Al20Cu2Mn3 phases. In particular, compared with the single-stage solution treatment, a two-stage solution treatment led to a 11.59% increase in tensile elongation, which is attributed to a comprehensive modification of the T phase, including a similar to 6.0% reduction in size, a 16.0% increase in number density, and an improved uniformity in size distribution. By employing artificial or natural aging after solution processes (S-AA or S-NA), the eutectic phases in the matrix dissolve extensively, resulting in the formation of substantial S-Al2CuMg/theta '-Al2Cu precipitates or GP/GPB zones, respectively. The hardness of the WZ approaches that of the base material, and strain localization phenomena are significantly reduced. Quantitatively, the tensile strength and elongation reach 1.03 and 0.65 (S-AA), or 1.01 and 0.74 (S-NA), those of the base material, respectively. This study shows that the PWHT, with flexible processing technologies, is an effective approach to suppress the softening of weld Al alloys, which could be applied in other weld Al alloys.