Low fracture toughness is one of the factors limiting the widespread applications of magnesium and its alloys. Mg17Al12 is a common precipitation phase in magnesium-aluminum-based alloys, and it favours crack nucleation in the experiment. While its effects on brittle and ductile crack-tip behaviours in magnesium are still lacking. This work examines the effect of Mg17Al12 phase on brittle and ductile crack extension behaviours in magnesium via atomic-scale 'K-field' loads simulation. The results show that the Mg17Al12 phase changes the brittle and ductile crack tip behaviours by affecting the distribution of the crack tip stress field. Under model I loading, the stress along the crack extension direction mainly concentrates at the interface of the Mg17Al12 phase and the matrix, which leads to a significant blunting of the crack tip geometry powered by the crack opening stress. For a ductile crack tip, the concentrated interfacial stress is mainly dissipated by dislocation nucleation, slip, void nucleation and growth. For a brittle crack tip, the concentrated interfacial stress is mainly dissipated by twin nucleation and void nucleation, growth, and cleavage along the matrix. This work presents the atomic-scale mechanisms of the effects of the Mg17Al12 phase on brittle and ductile crack tip activities in magnesium, which offer references for crack-tip activity analysis in magnesium-aluminum-based alloys.

In this study, by adjusting the homogenization process, numerous lamellar-shaped gamma' phases are generated and uniformly distributed throughout the grain interior within as-extruded Mg-9Gd-4Y-1Zn-0.5Zr (wt.%) alloy, leading to a remarkable increase enhancement in both tensile strength and fracture toughness. Notably, as compared to the alloy containing block-shaped long-period stacking-ordered (LPSO) phase, when the lamellar-shaped gamma' phase is introduced within the alpha-Mg matrix, the fracture toughness of 29.7 MPa center dot m1/2 can be achieved with a 27 % improvement. This superior fracture resistance is mainly attributed to the delamination toughening derived from the intensive micro-cracks occurring along gamma' phase interfaces oriented perpendicular to the primary fracture surface. Owing to the presence of lamellar-shaped gamma' phase, the fracture morphology can be significantly changed and characterized with deep dimples and pronounced deflection of main crack, which collectively contribute to the enhanced plastic energy dissipation and fracture toughness. The characteristics of deformed microstructure near the fracture surface demonstrate the activation of kinking and the inhibition of twin propagation due to the interactions with lamellar gamma' phase. Such deformation behavior can effectively impede the crack propagation and contribute to the superior fracture resistance. Besides, the X-ray computed tomography analysis of the fractured alloy exhibits the distribution and size of voids, indicating that the prolate voids preferentially nucleate and propagate parallel to the lamellar gamma' phase. Accordingly, the deformation mechanisms under a triaxial stress state involve the intricate interplay between lamellar gamma' phase-induced delamination, crack deflection as well as void formation. Through the application of tailored pre-treatment heat treatment processes, the control of phase constituents within the microstructure can be achieved to improve the mechanical properties of Mg alloys. It is anticipated to provide a comprehensive understanding of the fracture behavior of Mg-Gd-Y-Zn-Zr, with particular emphasis on the synergistic effects of lamellar gamma' phase and LPSO phase in the optimization of overall mechanical performance. (c) 2026 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/)

Die forging inevitably induces metal flow toward both the die cavity and flash, leading to the formation of a flow boundary between these two regions. However, the influence of such a flow boundary on the final microstructure and properties of forgings remains unclear. To address this gap, this study investigates the effects of flow boundaries on the microstructure and mechanical properties of disk-shaped 7075 aluminum alloy casing forgings via a combination of finite element (FE) simulations and experimental characterizations. Results show that two distinct flow boundaries form at different locations during disk forging, and their formation mechanisms and evolutionary characteristics were systematically clarified. Electron Backscatter Diffraction (EBSD) analysis revealed significant microstructural inhomogeneities at different locations of the forging: regions adjacent to flow boundaries (Locations 2 and 3) exhibit coarse grain structures with an average grain size of 54.02 µm and 32.70 µm, and low recrystallization fractions of 22.7% and 31.9%, which are only half of those in non-boundary regions (48.8%–51.9%). Tensile tests demonstrated that the yield strength of flow boundary regions in the radial direction is 362 MPa–371 MPa, which is 40 MPa–50 MPa lower than that of non-boundary regions (400 MPa–413 MPa). Although flow boundaries have a significant impact on grain morphology and texture development, they exert only a minor effect on phase distribution and texture intensity. These quantitative findings offer critical theoretical support for optimizing the forging processes of high-performance aluminum alloy components and improving the uniformity of forging properties.

Understanding wavelength-dependent electron excitation and energy deposition is essential for clarifying the early stage surface electronic response of 3C-SiC during femtosecond laser processing, but remains poorly understood. In this work, time-dependent density functional theory (TDDFT) is used to study 3C-SiC with femtosecond laser pulses at 13.5, 400, and 1030 nm over a wide intensity range, clarifying how ultrafast electronic excitation may influence the early stage surface electronic response of 3C-SiC. Under 13.5 nm irradiation, the response is dominated by direct high energy interband excitation, causing smooth current evolution and harmonic spectra dominated by the fundamental component. Under 400 and 1030 nm irradiation, increasing intensity induces strong current modulation and spectral broadening, indicating a transition from weak to strong field nonlinear response. Excited electrons and absorbed energies increase with intensity, with weak field scaling reflecting distinct excitation pathways. At 1 & times; 10(13) W/cm(2), 400 and 1030 nm pulses induce pronounced charge redistribution and drive the excited electron density to similar to 10(21) cm(-3), whereas 13.5 nm requires 1 & times; 10(14) W/cm(2). These findings show that medium- and long-wavelength femtosecond lasers more readily drive 3C-SiC toward a high density nonequilibrium electronic regime, suggesting favorable electronic precursor conditions for subsequent transient surface destabilization and electron-lattice energy transfer.

Achieving isotropic damage tolerance in thick plates of high-strength aluminum alloys remains a critical challenge. This study investigates the strength and toughness of a rolled thick plate of an Al-Zn-Mg-Cu alloy. The results show that while yield strength (similar to 600 MPa) is isotropic due to homogeneous nanoscale eta' precipitates, fracture toughness varies significantly across six orientations from 30.4 to 42.5 MPa center dot m(1/2). Multiscale characterization reveals that fracture behavior is governed by directional mesoscale weak interfaces, including pancake grain boundaries decorated with precipitate-free zones and rolling-direction particle stringers. A geometric accessibility index is introduced to quantify the relationship between crack orientation and the likelihood of accessing low-resistance pathways. These findings demonstrate that mitigating toughness anisotropy requires disrupting mesoscale connectivity, a strategy distinct from the nanoscale precipitation engineering typically employed to enhance strength.

The presence of the brittle β/B2 phase in TiAl alloys often deteriorates their mechanical properties, posing a significant challenge for manufacturing large-sized, high-performance sheets. To address this issue, this study systematically investigates the synergistic effect of pack rolling and subsequent heat treatment on the microstructure evolution and mechanical properties of a Ti-44Al-4Nb-1.5Mo-0.1B-0.1Y alloy. Sheets with two different deformation levels (R7: 69.8% and R11: 83.0% reduction) were prepared via pack rolling. This was followed by a series of heat treatments at different temperatures (1150–1350 °C) and cyclic heat treatments at 1250 °C (3, 6, and 9 cycles). The results demonstrate that the higher deformation level (R11) promoted extensive dynamic recrystallization, resulting in a uniform microstructure of equiaxed γ, α2, and β phases, while the lower deformation (R7) retained a significant fraction of deformed γ/α2 lamellae. Heat treatment at 1250 °C was identified as optimal for transforming the microstructure into fine lamellar colonies while effectively reducing the β/B2 phase. Cyclic heat treatment at this temperature further decreased the β-phase content to 4.1% after 9 cycles. The elimination mechanism was determined to follow the β→ α → γ + α2 phase transformation sequence, driven by the combined effect of rolling-induced defects and cyclic thermal stress. Cyclic heat treatment at this temperature was particularly effective in generating a high density of nucleation sites within the lamellar colonies, leading to significant refinement of the lamellar structure. Consequently, the R11 sheet subjected to 9 cycles of heat treatment exhibited a 15.5% increase in tensile strength and an 8.3% improvement in elongation compared to the hot-isostatically pressed state. This enhancement is primarily attributed to the significant refinement of lamellar colonies and the reduction in interlamellar spacing. This work presents an effective integrated processing strategy for fabricating high-performance TiAl alloy sheets with superior strength and toughness.

Serrated grain boundaries (SGBs) are conventionally viewed as barriers to dislocation motion. However, this study finds that in forged magnesium alloy AZ80A, the SGB segment, as a strain accommodator, generally sustains lower local flow stress than flat grain boundaries. Crystal plasticity finite element simulations, validated by experiments, reveal that the tortuous SGB morphology promotes activation of pyramidal (a) and (c + a) slip, thereby enhancing strain accommodation. A strain-accommodation factor, as a weighted measure of non-basal shear, is defined. Two simple models are established to depict that the strain-accommodation factor increases linearly with grain boundary tortuosity, while the local flow stress decays exponentially with this factor. They quantitatively describe the transition of SGBs from passive dislocation barriers to active strain accommodators. The resulting framework links grain boundary geometry to micromechanical response and provides insights for grain boundary engineering in Mg and other HCP alloys.

Hot compression experiments and microstructure observation investigations are utilized to analyze the hot deformation behavior and flow characterization of 18Ni(250) maraging steel. Arrhenius model, Strain Compensated Arrhenius-type (SCA) model, Johnson-Cook (JC) model, Zerilli-Armstrong (ZA) model and ANN model were developed for forecasting the flow characteristics, the prediction of each constitutive model was quantitatively assessed using statistical parameters. To determine the ideal deformation settings, twodimensional and three-dimensional hot deformation activation energy maps were created, and the affect deformation parameters on the development of the microstructure was demonstrated. The result shows that the ANN model's coefficient of determination (R2) is 99.679 % and average relative error (ARE) is 2.43 %, indicating that it has a greater prediction accuracy than other constitutive models. The dynamic recovery and flow localization in various deformation areas are examined in conjunction with the activation energy maps, and the optimal hot processing window were achieved. Embed the ANN constitutive model into the expert system develop the "Forging Forming Force Prediction Module". This module can calculate the stress and forging forming force in real time according to different deformation conditions, providing a theoretical basis for the selection of forging equipment and the verification of the effectiveness of the process scheme, and improving the intelligent manufacturing level of maraging steel forgings.

The hot deformation behavior of the duplex structured Mg-9Li-5Al-2Sn-1.5Y alloy is investigated via hot compression tests in the temperature range of 200–350 °C and strain rate range of 0.001–1 s−1. The flow behavior of the Mg-9Li-5Al-2Sn-1.5Y alloy is defined by hyperbolic constitutive equation. The Zener–Hollomon parameter Z is used in the hyperbolic-sine-type equation to express the relationships between the peak stress, deformation temperature, and strain rate. Dynamic recovery and dynamic recrystallization are the main characteristics that affect deformation behaviors. The activation energy Q is calculated as 127.89 kJ/mol. Based on the dynamic materials model, the processing maps at strains of 0.6 and 0.8 are constructed, and the optimum processing parameters are determined as the temperature range of 320–350 °C and strain rate range of 0.001–0.007 s−1.

As cast whisker-reinforced Al matrix composites are prone to cracking in subsequent forming processes due to numerous micro defects and poor formability, which limits their application. This work investigates the healing effects of current-assisted rolling and upsetting on cracks and micropore defects in a 6061Al composite reinforced with a total of 20 vol

This study investigates the effects of high-pressure torsion (HPT) with varying turns (1/2, 1, 5, and 10) on the microstructure and mechanical properties of as-extruded Mg-0.8Mn (wt%) alloy at ambient temperature. HPT process can reduce the grain size from 3 mu m to 0.4 mu m and induce a texture evolution from a basal fiber orientation to a basal plate configuration with increasing strain. Notably, Mn particles are fragmented and dissolved into the alpha-Mg matrix, indicating enhanced solid solubility of Mn due to HPT deformation. The alloy processed with five HPT turns exhibits remarkable room-temperature ductility, achieving 166 % elongation at a uniaxial tensile strain rate of 1 x 10(- 3) s(- 1). This exceptional ductility is primarily attributed to the activation of grain boundary sliding (GBS) and the non-basal dislocations. During tensile deformation, the fraction of low-angle grain boundaries (LAGBs) decreases, and the average grain size increases from 0.4 mu m to 1 mu m, accompanied by recrystallization growth. This phenomenon can alleviate the stress concentration, and thereby the ductility is improved. These findings underscore the critical roles of GBS and recrystallization growth in enabling a superplastic response during tensile deformation.

Stress-induced grain boundary (GB) migration plays a crucial role in plastic deformation, influencing the microstructure and mechanical properties of polycrystalline materials. While twinning and grain rotation are important deformation modes, their impact on the GB migration of Mg alloys remains unclear. This work builds the internal relationship between deformation twins, grain rotation, and stress-induced GB migration in a deformed Mg alloy by experiments and simulations. During the uniaxial compression experiment, the GB migration mainly occurs during the {1012}tension twin thickening. Atomic simulations reveal that twin thickening results from the slip of interface dislocations along the basal plane (0001) under shear stress. When interface dislocations of twins are hindered by the GB, local stress concentrations lead to GB migration. A new factor I, derived from experimental results, serves as a criterion to differentiate migrated from non-migrated regions during twin thickening at the mesoscale. Grain rotation accompanied by GB migration occurs under mesoscale observations. The scalar disclinations density increases at the GB junctions due to rotation and the disclinations move with the GB migration. Local rotation associated with the formation of low-angle GBs accelerates local migration and contributes to GB serration. Crystal plasticity finite element simulations show that the additional shear stress caused by grain rotation promotes GB migration. Our findings help to understand the GB migration mechanisms of Mg alloys related to the application of Mg alloys through GB engineering.

In this study, a grain boundary (GB) migration model based on crystal plasticity (CP) and phase field (PF) was constructed for recrystallization of magnesium alloys. The model introduced the stored energy field obtained by CP into the PF simulations, aiming to analyze the effect of the inhomogeneous stored energy generated under the plastic deformation on the GB migration. It was found that the curvature plays a more significant role in the inhomogeneous stored energy field than in the uniform deformation field. Although grains with hard orientation have a lower deformation storage energy, they are still partially swallowed due to mutual influence between GBs near the triple junction. The high energies in the original GBs increase the migration rate at the triple junctions locally for a short period of time, but it is not enough to make a significant difference over extended periods at mesoscopic scales. The simulation results in this study are helpful in explaining the previous experimental observations.

In this study, a phase-field model for simulating the grain growth of polycrystalline microstructures was developed. Based on the strain-induced grain boundary migration theory, the stored energy field is introduced into the model in a novel form. This approach aims to simultaneously account for the inhomogeneity of deformation-stored energy both within and between grains, and it no longer requires the artificial setting of the grain boundary migration direction. The model is then applied to simulate grain growth under varying stored energy fields and triple junction dragging effect. It was observed that, due to the different directions of local and long-range energy minimization, grain boundaries may migrate in opposing directions sequentially. When compared to a uniform stored energy field, the competition between stored energy minimization and grain boundary free energy minimization is more pronounced in a non-uniform stored energy field, and it is more likely to lead to the combination of triple junctions and the dissociation of quadruple junctions.

During deformation, dislocation movements at grain boundaries (GBs) directly affect GB plastic behaviors, thus affecting the mechanical properties of metal materials. As common defects in deformed Mg alloys, the specific role of and dislocations on room-temperature GB migration is still unclear. This work systematically investigates and answers this scientific question via experimental observations and atomic simulations. High-density serrated GBs of the AZ80 Mg alloy are achieved by multi-axial compression at room temperature. At the atomic scale, the overall slip of interfacial dislocations leads to GB migration, while the GB can remain flat. Different local migration rates caused by slip and interlock of adjacent and dislocations result in GB steps, thus forming the serrated GB as the deformation proceeds. The basal-pyramidal lock at the GB prevents the continuous migration of the local GB. A new basal pyramidal lock model at the GB is established to give a criterion for stable interlock of partial and dislocations. The experimental results and the atomic simulations show good agreement at the atomic scale and atomic simulations can explain the GB structure changes observed in the experiments. This work contributes to understanding the GB migration mechanisms of Mg alloys, which helps design deformed Mg alloys through GB engineering.

In this study, 15-5 PH stainless steel were fabricated by laser powder bed fusion (LPBF) at different construction angles (0 degrees , 30 degrees , 45 degrees , 60 degrees , and 90 degrees ). Effects of construction angles on the microstructure, mechanical properties, electrochemical properties and surface characterization of 15-5 PH stainless steel were investigated. The LPBFfabricated 15-5 PH stainless steel exhibited a " track-track " overlap trajectory on the horizontal plane, and the vertical plane displayed the " layer -layer " overlap of the melt pool. All samples were composed of martensitic and austenite phases. Irregular grains and random grain orientation were found in each sample. In fact, the construction angle has an important role in the microstructure. The 0 degrees sample has the lowest martensite content (75.8%), since fewer deposited layers correspond to less number of thermal cycles. Due to the largest amount of martensite (90.1%), the 45 degrees sample exhibits the highest hardness of 308.9HV 0.2 . The similar tensile strength and yield strength are achieved for samples fabricated at different forming angles. Layer by layer melt pool boundary (MPBs) contributes to the ductile deformation, whereas track by track MPBs is favorable for brittle deformation. Samples with a larger construction angle have more layer by layer MPBs, resulting in the increased elongation. Therefore, the 0 degrees sample shows a minimum elongation of 20.1%, but the 90 degrees sample reaches a maximum elongation of 23.9%. The construction angle affects the corrosion resistance of the 15-5 PH SS by influencing the martensite content. As a result, the 0 degrees sample, with the highest austenite content (24.2%), shows the best corrosion resistance and lowest roughness.

This paper introduces ‘SkeletonCLIP++’, an extension of our prior work in human action recognition, emphasizing the use of semantic information beyond traditional label-based methods. The innovation, ‘Weighted Frame Integration’ (WFI), shifts video feature computation from averaging to a weighted frame approach, enabling a more nuanced representation of human movements in line with semantic relevance. Another key development, ‘Contrastive Sample Identification’ (CSI), introduces a novel discriminative task within the model. This task involves identifying the most similar negative sample among positive ones, enhancing the model’s ability to distinguish between closely related actions. Incorporating the ‘BERT Text Encoder Integration’ (BTEI) leverages the pre-trained BERT model as our text encoder to refine the model’s performance. Empirical evaluations on HMDB-51, UCF-101, and NTU RGB+D 60 datasets illustrate positive improvements, especially in smaller datasets. ‘SkeletonCLIP++’ thus offers a refined approach to human action recognition, ensuring semantic integrity and detailed differentiation in video data analysis.

Structural properties and reliability of materials can be improved by increasing fracture toughness. At the atomic scale, the fracture is a material separation process, and the fracture toughness of materials is associated with the atomic-scale crack-tip behaviors/mechanisms. The crack-tip behaviors are relevant to the energy state of atoms in the system. Atomic thermal oscillation increases with increasing temperature, which may affect/alter the crack tip behaviors. This work is the first to investigate the temperature-dependent crack-tip cleavage/dislocation emitting competition in magnesium (Mg) using anisotropic linear elastic fracture mechanics theory, Density Functional Theory (DFT), and atomic simulation. Crack-tip behaviors are examined using a specially designed 'K-field' loads model. DFT calculations show that a single crystal system with lower entropy and higher Gibbs free energy implies stronger interatomic bonding that favors a higher KIc. Changes in the stress distribution initiate a brittle-ductile transition in crack-tip behavior. The ductile crack tip can be blunted by continuous crack-tip dislocations nucleation/ slip, and the evolution of the ductile crack-tip geometry from sharp to semicircular structure significantly decreases the stress concentration at the crack tip. A new criterion of the crack-tip force vector is established, which reasonably explains the geometrical evolution of ductile crack tip where the angle theta between the crack plane and the slip plane is 0 degrees < theta < 90 degrees and theta = 90 degrees. This work expands the atomic-scale brittle/ductile crack-tip behaviors/mechanisms of Mg, which provides a reference for crack-tip behavior analysis in engineering research.

The engine main shaft forgings have high requirements for product consistency and reliability, which are difficult to be guaranteed by traditional manual free forging. On the basis of the already-in-place machinery, technical optimization was done in order to realize intelligent forging of the engine main shaft forgings. A rail trailer, holding robot, inspection robot, and expert system were installed as well as other hardware and software. Additionally, the procedure and specifications for robot intelligent free forging were revised. Based on the artificial neural network (ANN) model, an optimization model and a prediction model were created, and the process parameters can be controlled during forging. The verification result shows that the intelligent free forging production line can achieve real-time control of the shaft forging process, and obtain the forgings whose shape, size, microstructure, performance and consistency meet the requirements. With the help of this production line, free forging can be produced more quickly and efficiently, which is crucial for realizing the automation, digitization, and intelligence of shaft forging free forging.