While structural heterogeneity in additively manufactured metals is well-documented, solidification dynamics and mechanical variations at the melt pool (MP) scale remain insufficiently understood. This study investigates an Al-6.4Ni-1.4Fe eutectic alloy produced by laser powder bed fusion using single-track melting experiments, multi-physics simulations, advanced characterization, and multi-scale mechanical testing. Three processing regimes are defined by the MP depth-to-width ratio: keyhole mode susceptible to vapor-depression and bubble entrapment, stable conduction mode for defect-free parts, and balling mode caused by inadequate fusion. Optimized parameters yielded a 99.9% relative density, with a room-temperature ultimate tensile strength (UTS) of 550.6 MPa and 6.5% elongation. Spatial variations in thermal gradients and cyclic reheating partition the MP into three distinct morphological zones: dispersed Al3Ni and Al9FeNi particles at MP boundaries, lamellar eutectics in transition zones, and interconnected rod-like precipitates in MP interiors. Accordingly, nanoindentation reveals peak hardness (3.0 GPa) at fine-structured MP boundaries, whereas micropillar compression identifies a higher yield strength (860 MPa) in the MP interior where continuous eutectic pathways facilitate load-bearing. Thermal exposure at 400 °C follows two-stage coarsening kinetics, moving from rapid supersaturation depletion to diffusion-limited ripening, allowing the alloy to retain a UTS of 162 MPa at 350 °C. Rather than viewing MP heterogeneity as a flaw, this work demonstrates how solidification gradients drive localized deformation, offering a blueprint for utilizing intrinsic AM heterogeneity in heat-resistant Al alloy design.

Two-dimensional (2D) materials with unique mechanical properties hold significant promise for applications in nano electronics, optics, and electromechanics. Herein, we investigate the nonlinear mechanical response and anisotropic failure mechanisms of the 2D MoSi2N4 family using density functional theory and a continuum constitutive model. MoSi2N4 and WSi2N4 exhibit excellent stability and mechanical properties, with maximum strains up to 17

Modelling fracture behavior of the shape memory alloy (SMA) that interacts with martensitic transformation and the associated elastocaloric effect (eCE) still remains challenging. Herein, a thermo-mechanically coupled phase-filed fracture model considering elastocaloric effect of SMA is proposed to simulate the cracking process coupled with the non-isothermal martensitic transformation and the associated eCE. In the phase-field model, both the thermal strain induced by eCE and the eigen strain induced by the phase transition are considered. An empirical degradation function is adopted to describe the thermal conductivity decreasing with the fracture order parameter. The model is validated with the finite element method and tensile fracture properties of Mn-Cu SMA are simulated. It is found that the martensite variant nucleates at the stress concentration where the crack initiates, and commonly spreads with an angle of 45 degree. The thermal expansion strain caused by the eCE could strengthen the critical load capacity. A large kinetic parameter for phase transition and the large orientation angle could enhance the strength and temperature change of eCE while the deformation capacity is reduced. The phase-field model demonstrates its ability in the thermal-mechanically coupled toughening of SMA. It also provides a possible fracture-resistance strategy by the utilization of eCE for elastocaloric devices.

The starvation of OH-reactants around the anode surface caused by rapid consumption during the alkaline oxygen evolution reaction (OER) is a critical problem limiting the development of anion exchange membrane water electrolyzers (AEMWEs). Here, we present a high-valence Lewis acid incorporation strategy to enrich OH-adsorption for optimizing alkaline OER performance and for the first time demonstrate direct participation of surface hydroxyl in the alkaline OER. In particular, the optimized Sr2CoMoO6 (SCMO) with the strongest surface hydroxylation exhibits excellent alkaline OER activity and AEMWE device performance when adopted as a noble-metal-free anode electrocatalyst, achieving an industrial current density of 1 A cm-2 at a low voltage of 1.83 V and steadily operating for 100 h. Combined experimental and theoretical investigations verify that the surface hydroxyls in SCMO participate in the OER via an unusual hydrogen-bond-assisted surface hydroxyl participation mechanism. These findings offer new insights into hydroxyl electrocatalysis for AEMWE applications.

Pore defects and their evolution critically affect fatigue and fracture behaviors in porous solids. However, explicitly resolving discrete individual pores remains computationally challenging because of their geometric complexity and the difficulty in capturing pore growth and coalescence. Here, we develop a defect-function based phase-field model (dfPFM) that couples a continuous representation of discrete pore defects and their evolution with a diffusive crack description in porous solids. Discrete pores are represented using a sigmoid-gated generalized Gaussian function that encodes their size, shape, orientation, and spatial distribution without requiring explicit geometric reconstruction. To describe pore evolution, a Gurson-Tvergaard-Needleman model-informed and a damage-informed defect evolution model are proposed for monotonic and cyclic loading, respectively. The evolving defect field is further coupled to the dfPFM through degrading the local elastic stiffness and fracture toughness. The dfPFM is benchmarked through the fracture simulations of single-pore, multi-pore, asymmetric three-point bending, and random-defect samples, showing good agreement with explicitly real pores in terms of crack-initiation sites, crack paths, and stress-strain responses. Phase-field results show that defect evolution accelerates damage accumulation, weakens inter-pore matrix ligament, and promotes pore coalescence, thereby leading to earlier softening and crack penetration. Fatigue simulations of additively manufactured TC4 with random defects indicate that defect evolution notably reduces fatigue life, with a 38%–68% life reduction as compared to the case without defect evolution, particularly in the high-cycle regime. Fatigue life scatter and crack path are corporately governed by the applied load and spatial distribution, clustering, and evolution of pores. The proposed dfPFM provides a continuum model for pore-defect sensitivity analysis, fatigue life prediction, and damage-tolerant design of porous metals.

Two-dimensional (2D) ferroelectrics and flexoelectric materials have garnered significant interest for their potential in next-generation nanoelectronics. Herein, we thoroughly investigate the flexoelectric response of monolayer FeSe under two distinct strain gradient modes (i.e., intrinsic constant strain gradient and phenomenological wrinkling-induced non-uniform strain gradient) by using first-principles calculations. Our results unveil a significant out-of-plane flexoelectricity under an intrinsic shear strain gradient eta 311, with a flexoelectric coefficient f (3311) = - 0.11 nC/m, rivaling that of typical Janus monolayers. This notable flexoelectric response is uniquely attributed to eta( 311), as the out-of-plane polarization remains insensitive to other strain and strain gradient components. Further analysis indicates that the flexoelectricity stems from the breaking of inversion symmetry due to asymmetric Fe-Se bond variation, which promotes directional charge transfer and leads to the formation of dipole moments. For the case of experimentally feasible wrinkling deformation in sinusoidal and parabolic modes, the strain gradient is non-uniform, and thus, the intrinsic flexoelectric coefficient cannot be determined, but a notable nonlinear flexoelectric response can be achieved with an out-of-plane polarization up to 10 mC/m( 2). The nonlinear increase in polarization magnitude stems from the cell-rotation-induced deviation of the polarization vector from the x( 3 )direction. This study highlights the strong flexoelectric potential of monolayer FeSe and demonstrates its versatile responses to distinct strain gradient modes. These findings provide fundamental guidance and key parameters for the design of future flexoelectric devices.

High-fidelity phase-field model (PFM) for molten pool dynamics in metal additive manufacturing (MAM) is highly required, which fully takes into account the coupled multi-physics problems of molten pool flows. Herein, we present a thermodynamically consistent non-isothermal PFM for incompressible multiphase flows with thermocapillary effects and phase change. The model is derived from a thermodynamic framework of incompressible two-phase flows, invoking the microforce theory and Coleman-Noll procedure. Features of molten pool flows, such as the large liquid-gas density ratio and temperature gradient, are fully taken into account. The model is further extended to the complicated thermo-solid-liquid-gas flows with laser-induced phase change (melting, solidification, and evaporation). Within the phase-field framework, we derive the smooth function for describing surface tension and recoil pressure acting on the molten pool and establish the thermodynamics of mass and energy losses due to evaporation. Several numerical benchmarks, such as flat gas-liquid interface, single bubble and droplet, and molten plate and particle, are introduced to validate the developed non-isothermal phase-field model. Simulation results show that the area of solidified single track is approximatively linear with the linear energy density. The non-isothermal PFM shows its ability to investigate the molten pool dynamics and pore defect formation during MAM process.

The fatigue performance of additively manufactured (AM) Inconel 718 is intrinsically governed by its grain morphology, necessitating a predictive understanding of the underlying plasticitydominated mechanisms. To address this challenge, this study applies an integrated multilevel computational framework that explicitly bridges the process-structure-property-performance chain by coupling finite-element and cellular-automata (FE-CA) simulations of grain growth during laser powder bed fusion (LPBF), a deep neural network (DNN) for efficient material parameter calibration, and a strain-gradient crystal plasticity finite element (CPFE) model for fatigue life prediction. This unified framework enables, for the first time, a rigorous like-for-like comparison of three characteristic AM microstructures-equiaxed, columnar, and mixed grains-under a consistent computational and experimental calibration protocol, and thereby reveals new micromechanical insights into potential fatigue damage initiation from the plasticity perspective. Our simulations indicate that fatigue resistance is predominantly controlled by grain morphology and further modulated by morphology-induced anisotropy. Among them, equiaxed grains exhibit superior fatigue resistance to columnar and mixed grain morphologies, which is attributed to the activation of multiple slip systems and the resulting homogeneous deformation. In contrast, the strong texture in columnar grains gives rise to a pronounced "channeling effect", leading to highly localized slip and a mismatch between regions of elevated plastic strain and actual damage accumulation. In terms of loading direction, the fatigue resistance under loading along the building direction (BD) is higher than that under loading along the transverse direction (TD). Crack initiation is predominantly predicted at high-angle grain boundaries and triple junctions, with the specific patterns highly sensitive to both grain morphology and loading direction. A key finding is the identification of a critical fatigue indicator parameter (FIP) threshold, beyond which fatigue life scatter intensifies significantly. While the CPFE model provides accurate predictions at intermediate strain amplitudes, its efficacy diminishes at higher strains due to

Laser shock peening (LSP) technology has been demonstrated to enhance the resistance to crack growth in metallic components. To understand the mechanisms of short crack behavior considering the LSP induced gradient microstructure and residual stress, we present a comprehensive modeling and computational framework, integrating a finite-deformation crystal-plasticity constitutive model with a phase-field fracture model. This coupled model facilitates the investigation of interplay among the residual stress, plasticity and short crack behavior in gradient polycrystalline with a full consideration of LSP induced microstructure features. To avoid nonphysical elastic deformation in the damage region, a damage-dependent flow rule is introduced. The coupled crystal-plastic phase-field fracture model (CPPFFM) is validated against experimental results from notched tension tests. The model is then employed to simulate the short crack behavior in LSPed Ti6Al4V alloy. Modeling results reproduce the crystallographic crack growth in single crystal, both intergranular and transgranular crack growth in low-ductility scenarios, and transgranular crack growth in high-ductility scenarios. Furthermore, the grain boundaries lead to the jumping crack propagation. LSP induced residual stress is shown to influence the crack initiation sites and reduce crack growth rates by retarding the damage accumulation. The results highlight the significance of residual stress in determining the short crack behavior of LSPed Ti6Al4V alloy. Our simulation results demonstrate the capability of CPPFFM in capturing the intricate interplay between residual stress and short crack propagation in gradient microstructure of LSPed materials.

Phonons are desirable for current-free energy-efficient spin manipulation and harnessing their chirality to achieve ultrafast magnetization switching remains actively pursued. Here we demonstrate that terahertz-driven chiral phonons enable faster magnetization switching than linear phonons through the purely magnetoelastic coupling that transfers both energy and angular momentum. Only one phonon handedness efficiently transfers angular momentum to the spin system, which we explain by a large fictitious kinematic Barnett-like field at THz frequencies that destabilizes spin precession for the opposite chirality. Considering different regions of the spinwave spectrum, we find that switching conditions can be realized near the Γ-point where strong energy transfer and spinwave excitation dominate, and near the P-point which offers minimal energy loss. Our results establish phonon chirality as a decisive and previously overlooked parameter in spin-lattice dynamics within the magnetoelastic coupling mechanism, offering a promising avenue for ultrafast low-energy spintronic devices.

Ferroelectric materials, integral to modern sensors, actuators, and transducers, exhibit complex fracture behavior under coupled electromechanical loading due to the intrinsic interplay between cracks, domain structures, and microstructural features. Linear piezoelectric fracture mechanics provides a foundational framework but fails to capture nonlinearities induced by domain switching and microstructure. This review synthesizes advances in computational modeling of ferroelectric fracture, with a focus on the unifying capabilities of the phase-field method (PFM). We first establish the fundamentals, including fracture toughness anisotropy and the crack-tip flexoelectric effect. We then critically assess traditional approaches like cohesive zone models and the extended finite element method, highlighting their limitations in handling arbitrary crack paths and complex microstructure evolution. The core of the review details how PFM has emerged as a transformative paradigm, enabling the simulation of diffuse crack propagation seamlessly coupled with ferroelectric domain dynamics within a single variational framework. We systematically examine recent progress in applying this framework to model fracture coupled with explicit microstructure (e.g., grains and domain walls), dielectric breakdown, fatigue under cyclic loading, and the integration of machine learning for model acceleration and inverse design. The review concludes by identifying persistent challenges, such as reconciling crack-face boundary conditions and bridging atomic-scale mechanisms with polycrystal-scale failure, and outlines future research directions toward predictive, multiscale, and experimentally validated models for designing reliable next-generation ferroelectric devices.

Laser additive manufacturing (LAM) is increasingly employed as an in-situ repair technique for restoring the structural integrity and fatigue performance of metallic components. The fatigue and fracture behavior of LAM repaired components are significantly affected by defects introduced during the repair process, which poses challenges for predicting fatigue properties after LAM repair. Herein, we demonstrate the fatigue strength enhancement and fatigue crack growth (FCG) mechanisms in LAM repaired titanium-alloy blades by integrating vibration-based bending fatigue experiments with phase-field modeling (PFM). It is found that LAM repair of the notched TC17 forged blade could improve the fatigue strength by 94%. Fatigue cracks are revealed to initiate at internal defects within the LAM repair and propagate along transgranular paths influenced by defect clusters, deviating from the surface-initiated cracks in the forged counterparts. X-ray computed tomography reveals that the defect is dominated by small pores, with over 80% exhibiting an equivalent diameter below 60 mu m. Furthermore, a macroscopic PFM incorporating fatigue life model that considers repair-induced pore defects is applied to predict the fatigue performance after LAM repair. Phase-field simulation results are shown to agree well with the experimental ones in terms of fatigue strength (error < 6%), critical crack length (error < 8%), and fracture surface morphology. Impact of defect features, material and model parameters on fatigue properties are investigated using our PFM, and the repair-induced pore size is shown to govern fatigue crack initiation and growth behavior of LAM repaired blade. Our work highlights the governing role of LAM repair-induced pore defects in high-cycle fatigue performance and enables a predictive PFM framework applicable to the fatigue evaluation of LAM repaired metallic components.

The persistent erosion caused by high-flux atomic oxygen in low Earth orbit environments is one of the key threats limiting the long-term operational reliability of spacecraft. To meet the demands of long-duration, highreliability space missions, traditional macro-scale protective coatings face challenges in weight reduction, stability, and functional integration. Micro- and nanoscale composite materials and structural design offer new approaches to protection. This paper provides a systematic review of research progress in micro- and nanoscale composite materials resistant to atomic oxygen erosion, focusing on protective mechanisms, material systems, and structural design. First, starting from the microscopic processes of atomic oxygen interacting with materials, this study summarizes and elaborates on the characteristics of typical protective mechanisms, including the physical barrier effect, synergistic barrier effect of multilayer structures, in situ nanopassivation, and chemical inertness protection. Furthermore, the protective systems of zero-dimensional, one-dimensional, and twodimensional nanomaterials are reviewed based on material dimensions. The analysis focuses on the unique advantages of two-dimensional layered nanomaterials such as graphene and hexagonal boron nitride in constructing dense protective interfaces, extending diffusion pathways, and enhancing service stability. Furthermore, this paper emphasizes the importance of integrating experiments with simulations for the rational design of composite protective materials. Finally, this paper summarizes the key scientific and engineering challenges currently facing micronano materials for anti-atomic oxygen protection. It also outlines future directions, including multi-scale synergistic protection, intelligent composite material design, and validation of adaptability in real space environments, aiming to provide guidance for the development and application of highperformance anti-atomic oxygen materials.

To address the critical challenges where traditional materials in aerospace and high-end advanced equipment are approaching their physical limits and struggling to meet the stringent SWaP(size,weight and power)requirements,the frontier of 2D(two-dimensional)materials is the primary focus.This paper systematically elucidated their application potential,derived from their atomic-level thickness and quantum confinement effects.By comprehensively reviewing the latest advancements in five core areas—stealth and electromagnetic shielding(survivability),high-performance sensing and detection(perception),lightweight protection and anti-corrosion(defense),high-efficiency energy and power(logistics/support),and quantum technology and information security(computing)—it revealed the intrinsic correlations and mechanisms connecting microscopic properties to macroscopic performance.Furthermore,the key bottlenecks restricting the engineering implementation of 2D materials were analyzed,including wafer-scale high-quality fabrication,long-term stability in extreme environments,and the standardization of testing and evaluation.Based on this analysis,and incorporating emerging technologies such as AI(artificial intelligence)-assisted design and heterostructure stacking,an outlook was presented for achieving multi-functional integration and intelligent systems based on 2D materials towards the development of next-generation smart equipment.This review aims to provide theoretical support and forward-looking insights for securing a strategic technological edge in the future.

Additively manufactured (AM) austenitic stainless steel (ASS, e.g., 316LSS) potentially exhibits excellent strength-ductility synergy in which the deformation-induced martensitic transformation (DIMT) is decisive. However, the DIMT mechanism is still elusive for AM 316LSS. Here we decipher the role of twin boundary (TB) and grain boundary (GB) in governing the DIMT behavior as well as the associated atomic-scale mechanism by characterization-informed atomistic simulations. Experimental characterizations of DIMT in AM 316LSS show martensite distributed near TBs under quasi-static (QS) tension, but closely related to GBs under high strain rate (HSR) tension. Informed by characterizations, atomistic models covering grain sizes, GB angles and TBs are then constructed to reveal the effect of GBs and TBs on DIMT behavior. It is found that the low-angle GB (LAGB) and small grain size in AM 316LSS suppress DIMT, whereas the synergistic effect of high-angle GB (HAGB) and large grain size (e.g., in wrought 316LSS) results in large-area DIMT. When TBs exist in the 316LSS grains, TBs can promote intragranular DIMT to make DIMT independent of GB angle and grain size, agreeing with DIMT observed in both wrought and AM 316LSS under QS tension. This is ascribed to the TBs-nearby heavy strain concentration that easily results in DIMT behavior and the TBs-nearby atoms that satisfy the Nishiyama-Wasserman relationship for triggering DIMT nucleation within the grain. In contrast, HAGBs dominate DIMT behavior in models without TBs owing to the GBs-nearby local lattice distortion that satisfies the Kurdjumov-Sachs relationship for allowing phase transformation. There are almost no HAGBs and thus an ignorable DIMT in AM 316LSS, agreeing with the experimental HSR tension results. These findings should shed light on the DIMT mechanism in AM 316LSS and help the design of AM 316LSS with improved mechanical performance.

The topological properties of metallic grain boundaries are crucial in determining their me-chanical,electrical,and chemical behaviors,making them a major focus of grain boundary engineering.This study systematically reviews recent advancements in understanding the topological characteristics of metallic grain boundary structures at various scales,including atomic-scale topological configurations and mesoscale grain boundary network topology.It begins by summarizing current research on the topol-ogy of grain boundary atomic structures,including the coincidence site lattice model,displacement shift complete lattice theory,topological characterisation of grain boundary dislocation networks,and analysis of topological defects.It then introduces characterisation methods for mesoscale grain boundary net-works,emphasising a research framework based on discrete cell complexes and systematically examin-ing the topological properties of these networks.Finally,potential applications of grain boundary topology research in materials design are discussed.

Welded components are widely used in advanced industries, but the complex non-uniform microstructure of welded joints poses challenges to accurately elucidate fatigue failure mechanisms and predict the fatigue crack initiation life of welded structures. Herein, we explore the fatigue short crack growth behavior in the fusion zone of nickel-based superalloy welded joints at 600 degrees C using an in-situ fatigue testing device. The microstructure-sensitive life of welded joints is predicted by dislocation-based crystal plasticity modeling that explicitly incorporates the experimentally characterized secondary phases. It is found that the short crack path is surrounded by multiple distinct activated slip plane traces (predominantly along {111} slip planes) and non-octahedral {110} slip planes are notably activated under high-temperature conditions. This pronounced multi-slip activity makes the crack growth deviate from the directions of a specific set of activated slip plane traces, leading to a complex zigzag-like cracking morphology. Geometric compatibility factor analysis reveals that local crack deflection at grain boundaries is strongly governed by the crystallographic orientation of neighboring grains. Furthermore, based on the crystallographic information and precipitate phase distribution from microstructure characterizations, we predict fatigue crack initiation life of the welded joint by dislocation-based crystal plasticity finite element model (CPFEM) that integrates Tanaka-Mura model. The predicted life is in good agreement with the experimental ones, falling into a two-fold scatter band. Our study could favor the analysis of fatigue failure mechanism and the prediction of fatigue crack initiation life of welded joints to provide guidance for improving service life of welded structures.

Carbon-based materials, with their lightweight, high-strength, high-temperature resistance, and corrosion resistance properties, are gradually replacing traditional metallic materials and becoming indispensable key materials in the aerospace field. This paper provides a systematic review of the latest research advancements in typical carbon-based materials such as carbon fibers, carbon nanotubes (CNTs), graphene, carbon/carbon (C/C) composites, and carbon aerogels for aerospace applications, with a focus on their application performance in critical scenarios such as thermal protection systems, resistance to atomic oxygen corrosion, and electromagnetic shielding. Through various performance optimization strategies such as interface control, nano-enhancement, and doping modification, the mechanical properties, thermal stability, and multifunctional integration capabilities of the carbon-based materials could be significantly improved. At the same time, this paper conducts an in-depth analysis of the current technical bottlenecks in terms of high-temperature oxidation resistance, manufacturability, and cost control, and then proposes future research directions such as multi-scale collaborative design, structure-property relationship modeling, and green manufacturing. This review aims to provide theoretical guidance and technical references for the design, optimization, and engineering application of high-performance carbon-based materials, promoting the development of aerospace equipment toward lightweight, high reliability, and multifunctionality.