JOM最新文献

Aluminum (Al) matrix nanocomposites reinforced with graphene nanoplatelets (GnPs) at varying contents (1, 2, 3, and 5 wt.%) were successfully fabricated through a powder metallurgy (PM) route. The GnPs were derived from natural flake graphite (NFG) by chemical intercalation using H₂SO₄ and H₂O₂, followed by thermal exfoliation at 1000°C and ultrasonication for 20 h. Al–GnP blends were prepared by ultrasonic dispersion in acetone (1 g/50 ml) for 2 h, dried at 100°C, compacted at 550 MPa for 5 min, and sintered at 550°C for 2 h in argon. Microstructural investigations through X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and optical microscopy confirmed a uniform dispersion of GnPs at low contents (1 wt.%), while higher additions led to agglomeration, particularly at grain boundaries. Among all the compositions, Al–1 wt.% GnP exhibited superior performance with a hardness of ~ 454 MPa, relative density of ~ 93.5%, and compressive strength of ~ 760 MPa, nearly 2.8 times higher than pure Al (~ 272 MPa). The improvements were attributed to homogeneous GnP distribution, effective load transfer, and restricted dislocation mobility. Dry sliding wear tests further revealed enhanced resistance for the 1 wt.% composite, evidenced by shallow wear depth and narrow tracks. However, higher GnP concentrations impaired densification and wear behavior due to clustering and inhibited sintering. These results emphasize the need for precise control of GnP loading to optimize both mechanical strength and tribological properties. Moreover, this study uniquely investigates the vibration behavior of Al–GnP nanocomposites, rarely reported in the literature.

This study compiled experimental data from the public literature and employed six machine learning algorithms to predict and compare the tensile strength of 6061-T6 aluminum alloy friction-stir-welded joints under various process parameters. The models evaluated include eXtreme Gradient Boosting (XGBoost), Random Forest (RF), Support Vector Regression (SVR), k-Nearest Neighbors (KNN), Gradient Boosting Decision Tree (GBDT), and Multilayer Perceptron (MLP). Feature selection was optimized using the Pearson correlation coefficient and dimensionality reduction techniques, reducing the number of input features from seven to five. Furthermore, SHapley Additive exPlanations (SHAP) were employed to interpret the relationships between disparate features and the tensile strength of the welded joints. The prediction results show that the RFE + XGBoost model achieved a mean absolute percentage error (MAPE) of 2.98%, a coefficient of determination (R²) of 0.973, a mean absolute error (MSE) of 45.31, and a mean absolute error (MAE) of 5.25, indicating its effectiveness in predicting the mechanical properties of 6061-T6 aluminum alloy welded joints. Further analyses showed that the features affecting the performance of welded joints were ranked in the following order of importance: welding speed (24.84), rotational speed (10.86), plate thickness (7.93), stirring needle length (7.55), and stirring needle shoulder shaft diameter (5.48).

The atomistic-scale mechanisms by which ruthenium (Ru) enhances the mechanical properties of WC-Co cermets have remained unclear, hindering rational material design. This study employs molecular dynamics simulations to decipher the strengthening effects of Ru, explicitly quantifying the contributions of solid-solution versus interfacial segregation. We reveal that grain boundary (GB) segregation is the dominant mechanism, yielding a remarkable 59.35% increase in yield strength at c = 0.03, far outperforming the minor solid solution strengthening from Ru in the Co binder (5.44% at c = 0.04). The interaction between these mechanisms is quantified using a novel degree-of-excess (DOE) parameterization strategy, with optimized strength (29.8 GPa) achieved at c = 0.03 and DOEsolu-seg = 0.25. This signifies a microstructure dominated by potent GB segregation with a secondary solid-solution contribution. Our work provides fundamental mechanistic insights into, and a practical strategy for developing, ultra-strong nanocrystalline cermets through targeted solute distribution control, establishing GB engineering as the key principle for maximizing performance.

This study evaluates the reduction kinetics of limonitic laterite using palm oil empty fruit bunch (EFB) biochar and coal–EFB blends under pelletized static-gas conditions. Reduction roasting was conducted at 600–1000°C with EFB biochar-to-laterite ratios of 1:2–1:4 and coal:EFB:laterite ratios of 1:1:4–1:1:8. Thermogravimetric reduction data were fitted using linearized kinetic models, yielding apparent activation energies of 4.3–22.3 kJ mol⁻¹, which is consistent with diffusion-controlled gas–solid reduction. Qualitative XRD confirmed sequential phase evolution compatible with gravimetric trends, and coal–EFB blends produced intermediate activation energies under identical conditions. These findings indicate that EFB biochar can serve as a potential renewable carbon source to partially substitute fossil reductants in laterite processing; however, this interpretation remains limited to laboratory-scale evidence, and further validation is needed before process-level application.

The construction industry is a major contributor to global carbon dioxide emissions. Portland cement concrete produces high emissions due to energy-intensive processes and calcination. Zero-carbon concrete is emerging as a sustainable alternative that reduces or eliminates these emissions. This review examines recent developments in zero-carbon concrete using the PRISMA approach. It explores low-carbon binders including fly ash, slag, calcined clays, and limestone that replace cement and lower emissions. The use of recycled aggregates and supplementary cementitious materials further improves sustainability. Advanced production methods such as carbon capture, CO₂ curing, 3D printing, self-healing systems, and nanomaterial integration are discussed for their role in enhancing performance and reducing environmental impact. Comparative analysis shows that zero-carbon concrete can match or surpass conventional concrete in compressive and flexural strength, durability, and workability. Lifecycle assessments indicate that material substitution, waste valorization, and circular economy practices are key to lowering the overall carbon footprint. Economic factors including initial costs and long-term benefits are also evaluated. The review highlights challenges such as limited raw material supply, cost, scalability, and the need for standardized design and testing protocols. Future directions include pilot-scale validation, local adaptation strategies, and integration of sustainability metrics into design standards. Collaborative efforts from researchers, industry, and policymakers are essential to accelerate the adoption of zero-carbon concrete. This study confirms that zero-carbon concrete is a viable pathway toward sustainable construction and can play a central role in achieving net-zero goals.

This study presents a systematic optimization of laser powder bed fusion (L-PBF) parameters for fabricating equiatomic CoCrFeMnNi high-entropy alloys (HEAs) with enhanced mechanical properties and reduced defect density. By varying the laser power, scanning speed, and hatch spacing under a constant layer thickness, a stable processing window —250 W laser power, 1400 mm/s scanning speed, and 0.07 mm hatch spacing—was identified. Specimens fabricated under these conditions exhibited an ultimate tensile strength of 579 ± 10 MPa, a yield strength of 510 ± 13 MPa, and a total elongation of 59 ± 3%. Electron backscatter diffraction (EBSD) analysis revealed a bimodal grain structure composed of coarse columnar grains and fine equiaxed grains, which contributed to both high strength and ductility. In-situ tensile testing combined with X-ray computed tomography (XCT) enabled real-time tracking of void nucleation and crack propagation, establishing a clear correlation between damage evolution and local stress states. The findings underscore the importance of precise control over energy input and scan strategy to minimize porosity and enhance structural integrity in L-PBF-processed HEAs. This work highlights the efficacy of process-parameter-driven strategies for tailoring microstructure and improving the mechanical reliability of HEAs in demanding structural applications.

The present study aims to extract and utilize the polyphenols of Camellia sinensis and Mentha spicata as active capping agents for the bio-fabrication of iron oxide nanoparticles (FeO NPs). Different techniques such as UV-Vis spectroscopy, FTIR spectroscopy, XRD analysis, FESEM, EDX analysis, and TGA were performed to determine the surface resonance, functional groups, size, shape, elemental composition, and thermal stability of the polyphenol-mediated FeO NPs. UV-Vis spectrum of C. sinensis and M. spicata polyphenol-mediated FeO NPs revealed significant absorption at 230 and 250 nm, indicating the formation of FeO NPs. The presence of metal oxides in the FeO NPs were verified through FTIR analysis. XRD spectra confirmed the crystalline structure of C. sinensis and M. spicata polyphenol-mediated FeO NPs. The occurrence of iron and oxygen was verified by the EDX spectra of both polyphenol-mediated FeO NPs. TGA analysis established that C. sinensis polyphenol-mediated FeO NPs had higher thermal stability than M. spicata polyphenol-mediated FeO NPs.

Wire and arc additive manufacturing (WAAM) is efficient for producing complex, large-scale metal parts, but the inherent repeated thermal cycling makes it difficult to achieve desired microstructural and mechanical characteristics. The microstructural evolution and mechanical properties of high-strength low-alloy steel during WAAM were investigated using a combined experimental and finite-element simulation approach, which particularly highlights the role of interlayer dwell time. The results demonstrate that reducing the dwell time increases the interpass temperature and intensifies thermal accumulation. Due to the repeated heating and cooling cycles during WAAM, the microstructures vary significantly along the building direction. Proeutectoid ferrite, grain boundary ferrite and bainite were the predominant phases, accompanied by a minor fraction of retained austenite. Anisotropic mechanical properties are observed in WAAM-fabricated steel components. Specimens from the middle region exhibit greater elongation but lower tensile strength than those from the bottom and top regions. Vertical tensile specimens, compared with horizontal ones, exhibit similar strength but reduced elongation, which can be attributed to interlayer structural imperfections. The fractured tensile specimens across all distinct regions exhibited a ductile fracture model. The study offers valuable insights into automating process parameter tuning to regulate the thermal effects during WAAM, thereby allowing accurate control of microstructural and mechanical properties.

Modern technology increasingly requires components to be made from specific high-performance materials. To support complex multi-metal structures, a variety of techniques are required to join dissimilar metal parts with precise shapes. This study evaluates vacuum diffusion bonding as a method for joining titanium and vanadium, focusing on both pure titanium and the common alloy Ti-6Al-4V. We employ modest pressure provided by a weight and simple surface preparation to simulate the most commercially applicable process. We show that Ti-6Al-4V alloy bonds readily to V, forming a continuous, clearly defined interdiffusion layer with predictable kinetics. Conversely, commercially pure Ti forms a crack-prone bond with V that fails to improve at higher bonding temperatures or longer times. We attribute this failure to the concentration of stress caused by the ß-to-α phase transformation in Ti. The contrasting bonding efficacy between pure Ti and the alloy provides insight into the crystallographic interactions that occur at the interface during bonding and cooling. These results provide surprising insight into a new method for bonding Ti alloys to V and possibly other metals that share the body-centered cubic crystal structure.

Coal slurry is a byproduct generated during coal washing, characterized by high moisture content, which limits its widespread application. This study investigated the effectiveness of deep drying coal slurry using the instant controlled pressure drop (DIC) technique combined with conventional thermal drying methods, while also exploring its drying characteristics. Experimental results indicate that, at 200°C, reducing the sample quantity significantly enhances the dehydration rate, while increasing pressure further accelerates the drying process. A modified Page model was applied to fit experimental data from the drying process, and the results demonstrated an excellent model fit, enabling accurate prediction of moisture changes in coal slurry under varying conditions. The study further revealed that increasing temperature and pressure effectively enhance the moisture diffusion coefficient, thereby improving drying efficiency. In summary, integrating DIC technology with coal slurry drying not only enhances drying efficiency but also offers high safety, providing a new technical pathway for efficient coal slurry utilization. This research delivers theoretical foundations and technical support for coal slurry drying, demonstrating significant industrial application potential.