Advanced Engineering Materials最新文献

Aluminum alloys are widely used in automotive, marine, and aerospace industries due to their excellent weldability and machinability but are prone to microcrack formation during service, leading to structural failure. This article proposes a novel friction stir welding repair strategy that incorporates SiC reinforcement combined with post-weld solution heat treatment to enhance the repair performance of 6061-T6 aluminum alloy. Unipolar and bipolar solution treatments are applied to 3-mm-thick plates. The addition of SiC not only promoted grain boundary strengthening but also significantly enhanced secondary phase strengthening. With 800 mesh SiC, the tensile strength increased to 292.1 MPa, 16.9% higher than the untreated sample. Heat treatment improved element distribution and further enhanced strengthening, with the bipolar solution-treated sample achieving 339.2 MPa, a 35.09% increase. A 3D finite element model of the repaired joint is established to analyze stress distribution, revealing that SiC addition intensified local stress concentration. Therefore, the synergistic use of SiC reinforcement and heat treatment significantly improved the mechanical properties of repaired joints, providing an efficient strategy for the restoration of aluminum alloy components.

The burgeoning field of additive manufacturing has enabled the creation of mechanical metamaterials with unprecedented design freedom. This work presents an integrated experimental–numerical framework for characterizing the hysteretic behavior of a Kelvin-type (truncated octahedron) lattice fabricated via laser powder bed fusion (LPBF) using 316L stainless steel. The objective is to assess its potential as a highly efficient energy-dissipating device for structural applications. The hysteretic response is determined through a proportional incremental cyclic-loading protocol and compared with a finite element-based computational model. The model accurately captured the progressive decrease in effective stiffness and the corresponding increase in effective damping observed experimentally. The Kelvin lattice achieves exceptional damping efficiency, with effective damping values exceeding unity at large deformations. Custom shear fixtures produced via fused filament fabrication using polylactic acid provided precise, low-cost testing supports for the LPBF specimens. The model also correctly identifies the specimen's failure location, confirming its predictive capability for future design optimization. Overall, this study demonstrates the feasibility of LPBF-manufactured Kelvin structures as metallic dampers and establishes a reproducible, cost-effective approach for testing and optimizing architected metamaterials for advanced energy-dissipation applications.

Fast cooling of aluminum alloys from the solutionizing temperature to “room temperature,” during which solute atoms and vacancies evolve rapidly, is the step defining all ensuing age-hardening treatments. Six Al–Mg and Al–Mg–Si alloys are solutionized and air-cooled at a moderate rate, after which cooling is interrupted in various stages by fast quenching and positron lifetime measured at 20 °C. In the ternary alloys, two main processes during cooling are found, continuous vacancy loss followed by solute cluster formation, whereas in the binary alloy, the latter process is absent. The extent of clustering is higher for high solute content, especially Si, while Sn addition to the alloy delays it. Compared to analogous calorimetry and resistivity measurements, positron lifetime measurement shows a unique sensitivity to vacancy evolution and an enhanced sensitivity to solute clustering.

The condensation of 6-ethyl-4-hydroxy-2,5-dioxo-5,6-dihydro-2H-pyrano[3,2-c] quinoline-3-carboxaldehyde with 4-aminoantipyrine affords pyrazolylamino-methylidenepyrano[3,2-c]quinoline (PAMPQ). The compound is characterized using elemental analysis, IR, ¹H NMR, ¹³C NMR, and mass spectrometry. Density functional theory calculations at the B3LYP/6-311++G(d,p) level are employed to explore the optimized structure, vibrational spectra, molecular electrostatic potential (MEP), frontier molecular orbitals (FMOs), and nonlinear optical properties. Drug-likeness is also assessed to evaluate its pharmaceutical potential. X-ray diffraction (XRD) analysis confirms the crystalline nature of the compound, determining its preferred orientations and Miller indices. Williamson–Hall analysis reveals an average crystallite size of 14.5 nm and a lattice strain of 3.7 × 10⁻⁴. Optical absorption studies on PAMPQ thin films exhibit absorption peaks at 2.8, 3.41, and 4.21 eV, corresponding to direct bandgaps of 3.00 and 3.57 eV. A single-oscillator model yields an oscillator energy of 3.88 eV, dispersion energy of 17.44 eV, and high-frequency dielectric constant of 4.55. When coupled with n-Si, PAMPQ thin films show enhanced photovoltaic performance, with improved rectification and measurable open-circuit voltage (V_oc) and short-circuit current (I_sc) under varying illumination. These results highlight the promising potential of PAMPQ thin films for applications in optoelectronic and photovoltaic devices.

Graphene and its derivatives exhibit superior performances matching with Cu matrix compared with other reinforcements, demonstrating excellent functional and mechanical properties. Herein, Y₂O₃-doped graphene oxide (GO)/Cu composites are synthesized through a novel strategy combining the electrodeposition with hydrothermal synthesis. Results indicate that GO@Y₂O₃ reinforcements can be uniformly dispersed within the Cu matrix, representing enhanced mechanical properties and excellent electrical conductivity. Specifically, the Y₂O₃-doped GO/Cu composite achieves a yield strength of 191 ± 9 MPa, which is 105% and 26% higher than that of pure Cu and the GO/Cu composite, respectively. This unique architecture of GO@Y₂O₃ reinforcements plays a bridging role at GO–Cu interfaces. Compared to the GO/Cu composite, the incorporation of Y₂O₃ nanoparticles gives rise to the significant enhancement in grain refinement strengthening, Orowan strengthening, and load-transfer strengthening. Additionally, the Y₂O₃-doped GO/Cu composite also exhibits a high electrical conductivity of 93.76% IACS (international annealed copper standard) while maintaining a good plasticity. This work establishes a feasible strategy for enhancing mechanical and electrical properties of Cu matrix composites through the interface engineering.

Fast cooling of aluminum alloys from the solutionizing temperature to “room temperature,” during which solute atoms and vacancies evolve rapidly, is the step defining all ensuing age-hardening treatments. Six Al–Mg and Al–Mg–Si alloys are solutionized and air-cooled at a moderate rate, after which cooling is interrupted in various stages by fast quenching and positron lifetime measured at 20 °C. In the ternary alloys, two main processes during cooling are found, continuous vacancy loss followed by solute cluster formation, whereas in the binary alloy, the latter process is absent. The extent of clustering is higher for high solute content, especially Si, while Sn addition to the alloy delays it. Compared to analogous calorimetry and resistivity measurements, positron lifetime measurement shows a unique sensitivity to vacancy evolution and an enhanced sensitivity to solute clustering.

This article presents the first comprehensive investigation coupling phase transformation, mechanical properties, and tribological behavior across build height in large scale laser wire directed energy deposition (LW-DED) fabricated NiTi alloy. A 140 × 135 × 10 mm wall is deposited to conduct location specific characterization and tribo-mechanical testing that can reveal the phase and property heterogeneity along the build height. X-ray diffraction quantified B2 austenite decreasing from 23 wt% at the upper region to 0 wt% at the lower region while R-phase peaked at 45 wt% in the middle region of printed NiTi wall. Differential scanning calorimetry showed martensite start temperatures ranging from 30.20 to 34.21 °C along the build height. Tensile testing demonstrated ultimate strength variations from 412 MPa in the lower region to 578 MPa in the upper region, representing ≈40% strength increase. Reciprocating wear tests on sectioned NiTi samples against AISI 52100 counter ball revealed build height dependent wear resistance, with the upper region exhibiting higher wear volume despite similar friction coefficients. The middle region presented a balance between strength and tensile ductility with the highest R-phase content, suggesting the crucial effects of thermal gyration during LW-DED on tribo-mechanical behavior in large scale NiTi components.

Vascular endoprostheses, composed of a metallic stent covered with an impermeable graft, are the gold standard for treating aortic aneurysms by isolating the weakened vessel from blood flow, preventing rupture. Expanded PTFE (ePTFE), the most common graft material, is traditionally produced by paste extrusion and stretching, which is energy-intensive, requires lubricants, and cannot reproduce the aorta's complex morphology. Here, the fabrication of PTFE grafts by 3D printing PTFE latex particles using digital light processing (DLP) is reported. This strategy allows rapid manufacturing of devices with morphologies adapted to patient anatomy. PTFE nanoparticles are embedded in a photocrosslinked dimethacrylated pluronic resin, enabling direct printing in water. Optimized thermal and chemical postprinting treatments transform the composite into a fully formed PTFE device. This two-step process yields materials with distinct mechanical, structural, and biocompatible features. Printed PTFE exhibits flexibility (Young's modulus: 17.8 ± 7 MPa) and high strength (elongation at break 157 ± 98%), while maintaining impermeability (withstanding up to 4 bar) due to an internal generated porosity (27.2 ± 8%). Fibroblast cytotoxicity tests (ISO 10993) confirm biocompatibility. This innovative approach, based on printing of PTFE latex particles via DLP, offers a promising route toward the fast fabrication of patient-specific PTFE vascular grafts.

Plasticizers play a critical role in polymer processing by reducing melt viscosity and improving moldability and flexibility. They achieve this by weakening intermolecular forces between polymer chains. However, the use of conventional phthalate-based plasticizers has raised significant concerns due to their endocrine-disrupting effects, prompting the need for eco-friendly, biobased alternatives. Therefore, this study aims to synthesize a series of isosorbide-based plasticizers with varying alkyl chain lengths and blend them with poly(vinyl chloride) (PVC). The resulting films are fabricated via a solution casting method. A distinct shift in the carbonyl absorption band is observed in the plasticized PVC films, indicating improved molecular interactions and miscibility between PVC and the synthesized plasticizers. As the alkyl chain length increases, the tensile strength and hardness of the films improve, while elongation at break decreases. These changes align with shifts in the glass transition temperature (T_g). Moreover, compared to epoxidized soybean oil, the isosorbide-based plasticizers exhibit significantly lower weight loss during thermal aging, demonstrating superior resistance to migration and enhanced thermal stability. These findings provide experimental evidence supporting the potential of isosorbide diesters as sustainable, high-performance plasticizers for PVC, offering a promising direction for developing safe and effective alternatives to phthalates.