Advanced Engineering Materials最新文献

In the integrated casting and forging process, the casting-forging interval has a significant impact on the quality of the casting. It controls the microstructure of the casting, including grain morphology and defect quantity, by regulating the solid-phase fraction, thereby affecting the performance of the casting. In this study, experiments are conducted on a Gleeble 3500 thermal simulator using a custom-modified. Through the real-time data acquisition system, curves of temperature and stroke versus time during the alloy solidification-forging process are obtained. The macroscopic defects and microstructures of the alloy under different solid-phase fractions during forging are investigated. The alloy microstructure is characterized using optical microscopy, scanning electron microscopy, electron backscatter diffraction, and three-dimensional computed tomography. As the casting-forging interval increases, the number of defects in the alloy samples decreases, and the grain morphology evolves from dendritic to equiaxed. At a casting-forging interval of 16 s, the alloy exhibits deformed structures and a low number of porosity defects.

Graphene oxide (GO) has attracted huge interest due its exceptional properties, being widely applied in many applications such as: flexible sensors, biomaterials, coatings, and energy storage. However, the direct application of these materials in their pure form is challenging due to their tendency to agglomerate and hard processability. To overcome these limitations, GO is often combined with other materials, giving rise to composites, hybrid mixtures, conductive inks, and structured films, expanding their application possibilities in different technologies. Thus, properties such as piezoresistivity can be explored allowing their use in the development of deformation and impact sensors, structural monitoring devices, and intelligent detection systems. In this study, the piezoresistivity of GO ink on different surfaces is investigated, analyzing how the combination of GO with ethylcellulose and terpineol influences its electrical and mechanical properties. A complete characterization is carried out to understand the polymeric interactions of the ink. A gauge factor of up to 30, in polyetherimide substract, is observed with a strain of 2% and low hysteresis.

This study investigates the high-strain-rate response and microstructural evolution of additively manufactured A286 steel lattice structures with body-centered cubic (BCC), honeycomb, and gyroid architectures. The lattices, produced via powder bed fusion–laser melting, are characterized through quasistatic compression, split Hopkinson pressure bar (SHPB) testing, and advanced material analyses including thermogravimetric-differential thermal analysis, Fourier transform infrared, X-ray diffraction (XRD), scanning electron microscopy (SEM), and residual stress evaluation. Under quasistatic compression, the honeycomb lattice exhibits the highest peak stress (≈3200 MPa), exceeding the BCC (≈2100 MPa) and gyroid (≈1500 MPa) configurations. SHPB tests reveal that the honeycomb maintains lower strain rates (≈1200 s⁻¹ at 6 bar) and minimal deformation, confirming superior dynamic stability. Despite its lower energy absorption (≈4.95 J), it demonstrates enhanced impact resistance due to retained compressive residual stress (−628 MPa) and improved stress redistribution. Finite element simulations corroborate experimental results, validating stress evolution and deformation trends. SEM and XRD analyses confirm that the honeycomb lattice resists fracture and maintains phase stability under high-strain-rate loading. These findings identify the honeycomb lattice as an optimal design for underbody blast protection in armored fighting vehicles, combining stiffness, resilience, and superior structural integrity.

The rapid progress of wireless technologies and telecommunications requires the development of microwave-absorbing materials (also known as radio-absorbing materials or radar-absorbing materials), since electromagnetic radiation threatens human health and interferes with the operation of electronic devices. Microwave-absorbing materials are also used to conceal “sensitive” targets, in particular, specific military equipment. This review considers the current state of composite microwave-absorbing materials engineering, focusing on the materials containing magnetic components. The mechanisms of magnetic absorption and methods for measuring complex permittivity and permeability are described. Two types of ferrites (spinels, hexaferrites) having different natural ferromagnetic resonance frequencies are analyzed. It is pointed out that in the hexagonal structure, cationic substitutions substantially influence the magnitude of crystallographic anisotropy field and may both increase and decrease the ferromagnetic resonance frequency. Such ferrites can be used for microwave-absorbing materials operating at frequencies up to tens and even 100 GHz. A review describes methods for ferromagnetic nanoparticles synthesis and shows their influence on the microwave absorption through the size and shape of nanoparticles. Examples of various microwave-absorbing materials are presented, their characteristics are given. From the analysis of literature publications, the directions for future research are formulated, and ways for improving the properties of microwave-absorbing materials are outlined.

To address the limitations of high-temperature diffusion bonding in zirconium alloys, the effect of controlled hydrogenation is investigated on bonding behavior, microstructure evolution, and joint performance. Zirconium alloy with 0, 200, and 2000 ppm hydrogen are prepared for diffusion bonding at 700–800 °C under 15 MPa for 30–120 min. At 200 ppm hydrogen, hydrides decomposed during bonding and reprecipitated along the interface upon cooling, eliminating interfacial voids and preserving finely dispersed second-phase particles around equiaxed α-Zr grains with minimal coarsening. At 2000 ppm hydrogen, incomplete hydride decomposition resulted in residual hydrides, while β-Zr at grain boundaries softened the interfacial grains without extensive recrystallization, maintaining grain sizes below 7 μm. Hydrogenation lowered the required bonding temperature, where joints bonded at 700 °C with 200 ppm hydrogen achieved shear strengths of 220 MPa, comparable to un-hydrogenated joints bonded at 750 °C. Similarly, 2000 ppm hydrogen enabled comparable strength at 720 °C to that of un-hydrogenated joints bonded at 780 °C. Molecular dynamics simulations confirmed that hydrogen-induced hydrogen-vacancy clusters enhanced atomic diffusion, while finite-element modeling demonstrated that hydrogen-induced softening lowered local stress concentrations and promoted void closure during bonding. These multiscale insights clarify the mechanisms where hydrogen enhances diffusion bonding efficiency and joint properties in zirconium alloys.

Grid-stiffened sandwich structures are widely employed in engineering applications owing to their superior mechanical properties. Nevertheless, their low-frequency sound-insulation performance is constrained by the surface mass density of the structure. In this study, a grid-stiffened sandwich structure incorporating local resonators is proposed by integrating traditional grid-stiffened sandwich designs and small-scale resonators. An analytical model is established based on the space harmonic expansion method, and the sound transmission loss (STL) of the proposed structure is evaluated through both theoretical analysis and finite element modeling. The low-frequency sound-insulation mechanism is explained by analyzing the average normal displacement and energy flow power. The results show that the average normal displacement reaches a minimum value at frequencies close to the STL peak, and the energy flux power through the grid wall and air field is reduced by more than tenfold. The impacts of the material parameters, structural parameters, and sound wave incidence angle on the low-frequency sound-insulation performance are analyzed. Finally, the accuracy of the finite element modeling is verified via impedance tube sound-insulation experiments. Consequently, this work provides a trigger for the design of multifunctional low-frequency sound-insulation structures.

The research on rare-earth-free magnetic materials has increased significantly in recent years, driven by supply chain issues, environmental and social concerns, and the growing demand for permanent magnets for green energy technologies. Current research efforts are focused on developing feasible processing methods to produce these alternative magnetic materials on a large scale. This review examines the latest advances in bulk processing methods for rare-earth-free magnetic materials, highlighting the key materials (α-MnBi, τ-MnAl, L1₀-FeNi, α″-Fe₁₆N₂, FeTa, Fe₂P), processing techniques, advanced multiscale simulations and associated challenges.

Cyclic plasma electrolytic polishing (C-PEP) processes are performed on additively manufactured (AM) Ti–6Al–4V coupons produced by laser powder bed fusion (LPBF) to address the effects of buildup angles and post-LPBF heat treatment. The varied buildup angles result in distinct morphological and microstructural features and structural defects, particularly on the down-skin surface due to the termination of melt pools on the coupon surface as well as the nonfully-melted feedstock particles. These variations influence the post-LPBF heat treatment and the polishing efficiency. Typically, lower buildup angles result in higher surface roughness and, particularly, higher down-skin roughness than that of the up-skin, which exhibits a correlation with the current density and electrolyte temperature during the C-PEP Process. An extrinsic phase, γ₁, is detected by X-ray diffraction after the post-LPBF heat treatment, and the phase composition increase with the buildup angles. Strikingly, the C-PEP process induces another extrinsic phase, γ₂, alongside γ₁, on the heat-treated coupons rather than on the as-built ones. The γ₂ phase compositions also increase with the buildup angles. Both the γ₁ and γ₂ phases can be completely removed by chemical etching. A mechanism is proposed, combining the post-LPBF heat treatment and C-PEP, to understand and interpret the observed phenomena.

Aerosol-deposited films display a reduced electromechanical response due to a grain size below 100 nm, deposition-induced residual stresses, and conductivity due to local defects. Although heat treatment can facilitate grain growth, residual stress relaxation, and defect recombination, it limits the possible applications of aerosol deposition, especially for temperature-sensitive substrates. Flash lamp annealing is utilized to selectively heat treat aerosol-deposited barium titanate films with different thicknesses from 2 to 16 μm. Simulations and X-ray diffraction indicate increasing temperature difference between the film surface and the substrate-film interface up to 170 °C for the 16 μm-thick film. While the relative permittivity can be improved by flash lamp annealing from 90 to 150 at 1 kHz and a 6 μm thickness, it still lags behind samples conventionally annealed at 500 °C, as the introduced thermal gradient can lead to surface cracks due to thermal stresses. Preannealing is proposed to reduce surface crack opening displacement compared to flash lamp annealed films. This supports the impact of remanent shrinkage during the first annealing cycle. While apparent challenges associated with the selective annealing of aerosol-deposited films are discussed, flash lamp annealing remains a promising method for reducing annealing time and utilizing temperature-sensitive substrates.

The as-cast Al–Ce–Mg alloy exhibits decent room-temperature strength and medium-temperature thermal stability, attributed to the load-transfer effect of coarsening-resistant Al₁₁Ce₃ eutectic phases and Mg-induced solid-solution strengthening, but its strengthening potential is limited by inherently coarse cast microstructure. To address this, this study refines Al₁₁Ce₃ via simple hot extrusion and further enhances strength by incorporating Sc/Zr—elements forming L1₂-structured Al₃(Sc,Zr) coherent nanophases—with extrusion fragmenting coarse Al₁₁Ce₃, inducing a heterogeneous fine/coarse-grain lamellar structure and retaining the Al₃(Sc,Zr)-driven refinement of primary α-Al and eutectic lamellae postprocessing. Performance wise, as-cast Al–Ce–Mg(-Sc–Zr) has 150 MPa strength; extruded Al–Ce–Mg reaches 246 MPa (room temp) and 112 MPa (250 °C); aged-extruded Al–Ce–Mg–Sc–Zr excels with 400 MPa (room temp), 215 MPa (250 °C), and ductile fracture. Quantitatively, extrusion boosts Al–Ce–Mg's room-temperature strength by ≈66%, while Sc/Zr microalloying adds 60% more and nearly doubles high-temperature strength, with the alloy integrating grain-refinement, solid-solution, Al₁₁Ce₃ particle, and precipitation strengthening—supported by hot extrusion for low-cost, large-scale industrial production.