Medium manganese (Mn) steel stands out as an exemplary representative of the latest generation of advanced high-strength steels intended for for automotive applications, attracting considerable interest due to its well-optimized microstructure and superior mechanical properties. Nonetheless, its pronounced vulnerability to hydrogen embrittlement (HE) poses a significant challenge. This research meticulously explores the hydrogen-induced delayed cracking behavior of thermomechanically processed medium Mn steel by conducting in situ hydrogen-charging slow strain rate tensile (SSRT) experiments, supported by post-mortem characterization methods such as scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and first-principles calculations. Findings from the SSRT tests reveal that medium-Mn steel exhibiting a complex multi-component heterogeneous structure, with variations in its structure, phases, and composition, demonstrates reduced susceptibility to HE. The regions of brittle fracture in the hydrogen-exposed specimens predominantly display cleavage or quasi-cleavage characteristics. Additionally, first-principles calculations indicate that the Mn partitioning-induced compositional heterogeneity significantly influences hydrogen trapping behavior, even in the absence of tensile strain. Within body-centered cubic (BCC) structures, ’Mn-lean’ areas exhibit a lower hydrogen binding energy. Moreover, cracks caused by hydrogen in medium-Mn steel commence at the interface between martensite (not surrounded by austenite) and ferrite, propagating transgranularly along the pathways of transformed martensite.

WC/W2C particle reinforced stainless steel composites were fabricated via laser powder bed fusion (LPBF) and subsequently heat-treated under two schemes: direct tempering (200-600 degrees C) and solution annealing at 1050 degrees C followed by tempering. The effects of these heat treatments on the microstructure, wear performance, corrosion behaviour, and mechanical properties were systematically investigated. While low-temperature tempering (<= 400 degrees C) promoted carbon redistribution and increased retained austenite from 17.6 % to 61.7 %, tempering at 600 degrees C-as well as the solution-annealed and tempered condition-suppressed austenite (approximate to 0 %) and triggered extensive precipitation of Cr-rich carbides. Solution annealing homogenized the matrix, eliminated austenite, and thickened the in-situ reaction layers to similar to 5 mu m. Intergranular corrosion susceptibility correlated directly with carbide-induced Cr-depleted zones, with the highest degree of sensitization (DOS > 220) occurring after the 600 degrees C and 1050 degrees C + 600 degrees C treatments, significantly exceeding that of other conditions (DOS < 150). Wear resistance was governed primarily by matrix hardness; wear volume loss increased markedly from 2 x 10(4) mu m(3) to 5 x 10(5) mu m(3), attributed to abrasive carbide debris and thermal softening. Compression tests demonstrated high deformability (> 60 %) after heat treatment; however, the as-built composite exhibited the highest compressive strength (similar to 4500 MPa) but underwent premature failure, owing to residual stress.

WC/W2C particle reinforced 420 stainless steel composites were fabricated via laser powder bed fusion. Their excellent wear resistance is offset by poor pitting corrosion resistance. This study investigates how post-processing heat treatments influence microstructure and corrosion behaviour. Heat treatment significantly altered phase composition and particle-matrix interfacial characteristics. Low-temperature tempering at 400 °C promoted austenite reversion, achieving the highest austenite fraction (∼62%). This microstructure yielded the highest critical pitting potential (Epit = 0.42 VSCE) and the lowest corrosion volume loss; however, the deepest and largest pits were also observed under this condition. In contrast, solution annealing reduced pit initiation near particles but decreased overall resistance due to austenite elimination. Tempering at 600 °C caused extensive precipitation of Cr-rich carbides, leading to Cr depletion and severely degraded corrosion resistance. The findings indicate that austenite stabilization through low-temperature tempering is crucial for enhancing pitting resistance, whereas annealing treatments are ultimately detrimental.

Antiferromagnets (AFMs) hold significant potential for spintronic devices owing to their insensitivity to external magnetic fields and the absence of stray fields. Beyond these inherent advantages, an AFM can manipulate the magnetic dynamics of a ferromagnet (FM) layer in AFM/FM bilayers, whereas the mechanism of such manipulation remains controversial. Here, we investigate the magnetic dynamics of AFM/FM Mn2Au/CoFeB bilayers via ferromagnetic resonance (FMR). It is found that the N & eacute;el temperature of 2-nm-thick Mn2Au is as low as 40 K, in sharp contrast to that of bulk Mn2Au, which exceeds 1000 K. In the Mn2Au(2 nm)/CoFeB(4 nm) bilayer, the magnetic damping alpha of the CoFeB layer increases from 0.013 to 0.047 as temperature decreases from 160 to 10 K, accompanied by a synchronous increase in the exchange coupling field H-rot. Such an increase in alpha is attributed to the enhanced spin angular momentum transfer from CoFeB to Mn2Au, mediated through AFM-FM exchange coupling between Mn2Au and CoFeB, which is enhanced by the Mn2Au antiferromagnetic ordering as the temperature decreases. Our study provides deeper insights into AFM/FM dynamics and spintronic storage technology.

Grain boundaries (GBs) naturally form in and dominate the physical properties of polycrystals. However, the associated atomic reconstruction and magnetism have been scarcely studied in vdW magnets. Here, we systematically investigate the thermodynamically stable GBs in magnetically frustrated Ni-dihalides, where the reconstructed atomic configurations not only give rise to dangling bounds that suppress the local magnetic moment at the GBs but also induce strongly antiferromagnetic coupled four-coordinate Ni atoms, leading to two segmented helical domains that are antiferromagnetically aligned. Moreover, the defective energy can stabilize ultrasmall metastable skyrmions/antiskyrmions (∼1.4 nm) in NiCl2 and NiBr2. They are pinned at the GB and remain stable even when Bz > 18 T. Additionally, lower magnetic fields can also nucleate nanometer-sized skyrmions/antiskyrmions within the domain regions, which can move along the GB direction under a spin-transfer-torque effective field. These results provide a detailed description of magnetism in vdW GBs and provide a new strategy to eliminate the skyrmion Hall effect.

Conventional trial-and-error methods for developing high-performance catalysts are typically time-consuming and inefficient. In this work, we proposed a rapid discovery strategy for graphene-supported single-atom catalysts for nitrate reduction to ammonia by integrating machine learning techniques with first-principles calculations. Three machine learning models based on Gradient Boosting Regression were trained for multi-target property prediction using 704 data points from theoretical simulations. This enabled the identification of 30 promising single-atom catalysts from 431 candidates, among which VN3B1 exhibited particularly outstanding performance with a limiting potential of −0.28 V. The catalytic descriptors constructed via symbolic regression algorithm identify the key physicochemical features, as well as the joint roles of the metal active site and its coordination environment, thereby enabling direct prediction of catalyst performance with high accuracy and strong generalizability. This study not only provided a set of promising catalysts and structural descriptors for nitrate reduction but also introduced a practical methodological framework for accelerating the screening process of advanced electrocatalysts in complex multi-step reactions.

A symmetry principle for understanding key elementary reaction steps in catalytic reactions is proposed in this study by employing the pseudo-Jahn-Teller effect (PJTE) vibronic coupling theory. The reactivity of elementary reaction steps can be correlated with fractional charge transfer between the catalyst and reactant, which promotes PJTE instability and the symmetry breaking of the adsorbed molecule. Beyond the commonly used adsorption energy, the degree of symmetry deformation of the reactant can serve as an intuitive and important indicator for evaluating the elementary reaction characteristics. Using the adsorption-induced structural activation of reactants in representative elementary steps of the carbon dioxide reduction reaction (CO2RR) and nitrate reduction reaction (NO3RR) as examples, combined with experimental and theoretical evidence, we reveal the intrinsic relationship among fractional charge transfer, reactant distortion, and elementary reaction thermodynamics and activation barriers. This work provides a new physical picture for understanding reactant reactivity and developing new activity descriptors in catalysis.

The tribocorrosion behavior of 904L super austenitic stainless steel (SASS) was investigated and compared with that of 316L austenitic stainless steel (ASS). Tribocorrosion tests were conducted in 3.5 wt% NaCl solution under different applied potentials, followed by comprehensive characterization of surface morphology, subsurface microstructure, and local chemical composition. The results demonstrate that, while 904L SASS exhibits tribocorrosion resistance comparable to 316L ASS at low applied potentials, their behaviors diverge significantly at high potentials. The tribocorrosion resistance of 316L ASS deteriorates continuously with increasing potential, whereas 904L SASS displays a distinct recovery at higher potentials, with material loss at 800 mVvs.Ag/AgCl even lower than that at 0 mVvs.Ag/AgCl. This divergence arises from fundamentally different degradation mechanisms. For 316L ASS, the onset of pitting corrosion at elevated potentials triggers a self-accelerating wear-corrosion synergy. In contrast, 904L SASS remains free from pitting corrosion, enabling rapid repassivation at high potentials that effectively suppresses dissolution and reduces friction. The superior performance of 904L SASS originates from its optimized chemical composition. The higher Cr content ensures that, even after repeated depassivation-repassivation cycles, the Cr-depleted layer remains above the critical passivation threshold (13 at. %), preserving repassivation capability. Additionally, the substantial Ni content, which suppresses strain-induced martensitic transformation, thereby avoiding increased electrochemical activity, and the higher Mo content helps maintain pitting resistance under tribocorrosion conditions.

Due to its excellent strength and ductility, medium-Mn steel has gained increasing application in the automotive industry in recent years. However, as strength improves, hydrogen embrittlement (HE) has become a critical challenge that restricts the safe service of high-strength steels. This study aims to enhance the HE resistance of medium-Mn steel (Fe-0.2C-12Mn) through the addition of Al, a common lightweight alloying element. Two steels with 0Al and 2Al contents were produced via warm rolling and cold rolling processes. The mechanical properties and HE sensitivity of these steels were evaluated using slow strain rate tensile (SSRT) tests. Detailed microstructural characterization was conducted using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) to elucidate the effects of Al addition on the mechanical properties and HE resistance of medium-Mn steel. The results indicate that the annealed and tempered steel sheets exhibit similar tensile strength, but the tempered sample shows a significantly higher yield strength. In addition, the annealed steel demonstrates considerably greater elongation. With the addition of 2 wt% Al, the strength of the steel decreases, while the elongation and toughness improve. Notably, the incorporation of Al simultaneously enhances both the product of strength and elongation (PSE) and the HE resistance. These findings provide valuable insights for the development of high-strength steels with superior comprehensive properties.

The tribocorrosion resistance of CrFeCoNi high-entropy alloys (HEAs) was systematically studied through controlled addition of cerium (Ce) in 0.9 wt

Inspired by natural phenomena, biomimetic raindrop-shaped surface textures (hemispherical crown-wedge triangle composites) were designed and fabricated on Ti6Al4V via selective laser melting, followed by micro-arc oxidation (MAO). Tribological behavior was evaluated, and surface morphology, phase composition, and elemental distribution were characterized using SEM, XRD, and EDS. Results show that all textured specimens exhibit improved friction-reducing and anti-wear performance. The combination of raindrop textures and MAO treatment further enhances tribological properties compared to untreated counterparts, with an optimal texture area density 24.93% yielding the best performance. Computational fluid dynamics (CFD) simulations reveal that raindrop textures reduce oil film stiffness loss and improve bearing area, load-carrying capacity, and hydrodynamic lubrication compared to conventional textures. Overall, the integration of biomimetic raindrop textures and MAO surface modification provides an effective approach to enhance the tribological performance of Ti6Al4V alloys.

This study systematically investigated the effects of TiC addition on the microstructure and hydrogen embrittlement (HE) behavior of laser powder bed fusion (LPBF) 15-5 PH stainless steel. The addition of TiC refined the microstructure, transforming lath martensite into fine equiaxed grains and reducing the average grain size from 3.32 μm to 1.25 μm. Meanwhile, the retained austenite content increased by approximately 9.5%, accompanied by a reduction in kernel average misorientation (KAM). Transmission electron microscopy (TEM) analysis further revealed the formation of incoherent TiC/matrix interfaces and nanotwins. After TiC addition, the hydrogen content decreased from 3.12 ppm to 1.97 ppm, and the hydrogen embrittlement sensitivity, evaluated by the loss of elongation, decreased by approximately 75%. Fractography and electron backscatter diffraction (EBSD)-based crack propagation analysis demonstrated that large blocky retained austenite regions effectively deflected and hindered crack propagation. The improved HE resistance was interpreted as being associated with the synergistic effects of reduced local strain concentration, possible hydrogen trapping at incoherent TiC/matrix interfaces, and crack arrest by retained austenite.

This study examines how TiC reinforcement and aging at 480 °C (1–10 h) modulate the pitting corrosion resistance of laser powder bed fusion (LPBF) 15-5 PH stainless steel. TiC addition refined martensitic laths into ∼1 μm equiaxed grains, increased retained austenite to 13%, and raised the critical pitting potential from 0.33 to 0.36 VSCE through grain refinement and austenite stabilization. During aging, austenite content in the TiC reinforced LPBF stainless steel composite increased continuously, reaching maximum at 48.8%, while MnS-type inclusions formed in the LPBF 15-5 PH stainless steel. Prolonged aging triggered a competition between beneficial austenite enrichment and detrimental carbide precipitation, governing the final corrosion performance. The results clarify the synergistic mechanisms by which TiC and post heat treatment tailor microstructure to enhance pitting corrosion resistance.

Hydrogen embrittlement (HE) remains a critical limitation for the structural application of Ni-based alloys in hydrogen-enriched environments. In this study, the synergistic effects of microstructural defects and heat treatment on hydrogen diffusion/trapping and embrittlement behavior in Laser Powder Bed Fusion (LPBF) Inconel 718 were systematically investigated in comparison with conventionally manufactured (CM) 718. Multi-scale characterization methods: X-ray micro-computed tomography (μCT), electron backscatter diffraction (EBSD), thermal desorption spectroscopy (TDS), glow discharge optical emission spectroscopy (GDOES), and three-dimensional Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) were employed to quantify defect structures and hydrogen distribution.Results show that microstructures of AM 718 exhibit hierarchical defect networks, including lack-of-fusion pores and high densities of geometrically necessary dislocations (GNDs), which act as stress concentration area and hydrogen trapping sites. Heat treatment and hot isostatic pressing (HIP) significantly reduce dislocation density and partially mitigate porosity, leading to decreased hydrogen uptake; however, residual defects and lattice distortions persist. ToF-SIMS and TEM mapping demonstrates notable hydrogen segregation at melt-pool boundaries and interfaces of layer. Mechanical testing coupled with in-situ Digital Image Correlation (DIC) / EBSD show that hydrogen promotes severe strain localization and premature failure in AM samples. Despite post thermal processing, AM alloys retain higher HE susceptibility than CM materials due to persistent defect-assisted hydrogen trapping. This work establishes a direct link between AM-induced hierarchical defects, spatial hydrogen distribution, and localized deformation, providing critical insight for designing hydrogen-resistant AM alloys.

Combining experiments with first‑principles calculations, this study investigates the electrochemical corrosion behavior of the VNbTaW refractory high‑entropy alloy (RHEA) in 3.5wt.% (weight percent) NaCl solution. The RHEA exhibits lower self‑corrosion and passive current densities than pure Ti, which is attributed to its higher surface work function and the formation of a dense, stable passive film enriched in Nb₂O₅ and Ta₂O₅ on its surface. First-principles calculations reveal that Nb₂O₅ and Ta₂O₅ possess higher oxygen-vacancy formation energies than V₂O₅ and WO₃, effectively suppressing Cl⁻ attack, while stronger O–Nb and O–Ta bonds further enhance passive film stability. Consequently, the excellent corrosion resistance of RHEA originates from the stable high-valence oxides formed on its surface, highlighting its great potential for applications in harsh and corrosive environment.

Hydrogen embrittlement (HE) is a critical issue that constrains the service reliability of structural alloys in hydrogen-rich environments. For the CoCrNi medium-entropy alloy (MEA), the interplay between deformation twins (DTs) and HE remains controversial, and the mechanism by which pre-strain-induced twin boundaries (TBs) influence hydrogen migration pathways and fracture behavior still requires further elucidation. To address this, the present study employed multiple complementary techniques, including slow strain rate tensile (SSRT) testing, electron backscatter diffraction (EBSD) analysis, direct hydrogen visualization via hydrogen microprinting (HMP), and microhardness measurements, to comparatively investigate the hydrogen-induced cracking behavior of the alloy subjected to pre-strain levels of 0%, 30%, and 50%. Experimental results reveal that dense nanoscale TBs can serve as both effective hydrogen trapping sites and diffusion barriers, substantially modifying the hydrogen distribution pattern and preventing substantial hydrogen enrichment at grain boundaries (GBs). This twin-dominated regulatory mechanism significantly suppresses hydrogen-induced intergranular fracture, endowing the material with outstanding HE resistance. These findings elucidate the intrinsic anti-HE mechanism governed by twin structures and provide a microstructural design basis for the development of high-performance hydrogen-resistant multi-principal element alloys (MPEAs).

The cooling condition after austenitization plays a critical role in determining the corrosion performance of additively manufactured martensitic stainless steel composites. In this work, the effect of cooling rate on the pitting corrosion behavior of WC/W2C reinforced laser powder bed fusion (LPBF) 420 stainless steel composites was systematically investigated using electrochemical measurements, microstructural characterization, and surface analysis techniques. The results reveal a cooling-rate-dependent transition in the dominant pitting initiation mechanism. Under furnace cooling, extensive diffusion of W and C promotes the formation of a continuous W-rich precipitates phase along grain boundaries, which act as preferential pit initiation sites. When the cooling rate increases, grain-boundary precipitation is largely suppressed. Consequently, the pit initiation sites adjacent to WC/W2C particles, where micro-galvanic coupling between the particles and the surrounding matrix drives interfacial pit formation. With further increases in cooling rate (oil and water cooling), the particle-matrix interface remains the primary pit initiation site; however, the stability of the passive film is significantly enhanced. In particular, water cooling produces a WO3 enriched passive film with a higher O2-/OHratio, resulting in improved resistance to chloride-induced breakdown. Consequently, the critical pitting potential increases monotonically with cooling rate, reflecting a mechanistic transition from precipitationcontrolled to passive-film-stabilized galvanic pitting.

Purpose-The purpose of this paper is to develop extreme marine corrosion-resistant coatings and to fabricate TiZrNbTaMoW refractory high-entropy alloy thin films and clarify the effect of sputtering power. Design/methodology/approach-TiZrNbTaMoW refractory high-entropy alloy thin films were fabricated by DC magnetron sputtering. The influence of sputtering power (80/100/120 W) on their microstructure and corrosion properties was investigated. Findings-Sputtering power dominates film density, crystal orientation and composition uniformity. Uniform composition (deviation < 5%) and optimal corrosion resistance are both achieved at 100 W. Research limitations/implications-This study only focuses on sputtering power without considering other magnetron sputtering parameters. Corrosion tests are only carried out in 3.5 Wt.% NaCl solution. Practical implications-This work clarifies the sputtering power-microstructure-corrosion property relationship, offering new material and technical support for marine engineering protection. Originality/value-The regulation mechanism of sputtering power on the films was systematically investigated for the first time, providing a new research basis for refractory high-entropy alloy coatings used in marine environments.

The TC4 ELI titanium alloy stress joints used in offshore riser system were welded by inertia friction welding with different rotational speeds (600-750 r/min), then the temperature field, stress field, axial shortening amount, microstructure and mechanical properties of joints were studied using a combination of experimental and simulation methods. Moreover, the simulation results indicated that the peak temperature, equivalent stress, and axial shortening amount all increased with increasing rotational speed, which is attributed to greater plastic deformation at the WZ induced by higher rotational speed. Furthermore, as the rotational speed increased from 600 to 750 r/min, the tensile strength of joints exhibited minimal variation, reaching 97.4%-97.9% (room temperature) and 101.2%-104.6% (350 degrees C) of the base metal, respectively. In contrast, the elongation first increased and then decreased. At 700 r/min, the tensile strengths reaches 97.9% (room temperature) and 104.6% (350 degrees C) of the base metal, respectively, which is attributed to the synergistic strengthening effect of brittle acicular alpha ' martensite and dislocation pinning within the joint; and the elongation reaches 100.6% (room temperature) and 99.5% (350 degrees C) of the base metal, which is attributed to the lower geometrically necessary dislocations density, refined grains, and a high proportion of high-angle grain boundaries.