Advanced Engineering Materials最新文献

In the present study, cold metal transfer welding is conducted to join laser powder bed fusion (L-PBF) AlSi10Mg alloys with conventional Al–Mg alloys and Er and Zr modified Al–Mg (Al–Mg–Er–Zr) alloys, respectively. The porosity, microstructural evolution, and mechanical properties of dissimilar AlSi10Mg/Al–Mg and AlSi10Mg/Al–Mg–Er–Zr joints are investigated. The results show that the AlSi10Mg/Al–Mg–Er–Zr joint exhibits reduced porosity in the weld metal (WM), decreasing from 2.4% to 2.1%, compared to the AlSi10Mg/Al–Mg joint. The AlSi10Mg/Al–Mg–Er–Zr joint exhibits significant microstructural improvements in the WM, including grain refinement, a lower Schmid factor, and a higher geometrically necessary dislocation density. The ultimate tensile strength (UTS) values of the AlSi10Mg/Al–Mg and AlSi10Mg/Al–Mg–Er–Zr joints are 187.6 and 203.3 MPa, respectively. This demonstrates that the AlSi10Mg/Al–Mg–Er–Zr joint achieves a significantly higher UTS, which can be primarily attributed to the reduced porosity, grain refinement, and enhanced solid solution strengthening in the WM.

The microstructure and mechanical properties of Mg₉₇Gd_1.5Er_0.5Ni₁, Mg₉₇Gd₁Er₁Ni₁, and Mg₉₇Gd_0.5Er_1.5Ni₁ (at.%) alloys with long-period stacking ordered (LPSO) phases are investigated. In the as-cast condition, all alloys consist of an α-Mg matrix and the 18R LPSO phase, with its volume fraction increasing notably as Er substitutes for Gd. Solution treatment induces a partial transformation of the 18R LPSO phase to the 14H LPSO phase in the Mg₉₇Gd_1.5Er_0.5Ni₁ alloy, accompanied by the precipitation of nanoscale (Gd,Er)Mg₂Ni₉ particles. In contrast, the Er-rich Mg₉₇Gd_0.5Er_1.5Ni₁ alloy retains the 18R structure, demonstrating the stabilizing role of Er on the 18R LPSO phase. Tensile tests reveal that both the yield strength (YS) and ultimate tensile strength (UTS) of the as-cast alloys increase with Er content, peaking at 122 ± 4 MPa (YS) and 220 ± 6 MPa (UTS) for the Mg₉₇Gd_0.5Er_1.5Ni₁ alloy. After solution treatment, the Mg₉₇Gd₁Er₁Ni₁ and Mg₉₇Gd_0.5Er_1.5Ni₁ alloys exhibit moderate improvements in both strength and ductility, whereas the Mg₉₇Gd_1.5Er_0.5Ni₁ alloy shows enhanced strength but reduced ductility due to the precipitation of (Gd,Er)Mg₂Ni₉ phases.

In this study, hybrid polymer composites based on polypropylene (PP) are developed using aluminum nitride (AlN) and super thermal conductive graphite (Gr) as fillers to improve mechanical, structural, thermal, and electrical properties. A series of composites containing varying ratios of AlN and Gr are fabricated via melt mixing and hot-press molding techniques. The synergistic effects of ceramic and carbon-based fillers are systematically investigated through mechanical testing, SEM analysis, DSC/TGA thermal characterization, and electrical resistivity measurements. Results show that low filler concentrations led to improved dispersion, mechanical integrity, and enhanced thermal properties. The Gr addition act as an efficient nucleating agent and significantly increases crystallinity and thermal conductivity, while AlN contributes to mechanical reinforcement. In comparison with neat PP, the 10A20G composite exhibits ≈63% (≈1.6-fold) higher thermal conductivity and about 10⁴ times lower electrical resistivity, confirming its suitability for thermal interface applications. The findings suggest that the hybrid use of AlN and Gr can lead to high-performance PP-based composites for electronic packaging and thermal management applications.

Higher stiffness of commercially available femoral implants compared to the surrounding bone results in loosening of the femoral implant, which requires revision hip replacement surgery. To address this issue, 3D-printed porous femoral implants have been explored to avoid early implant failure. These implants can minimize stress-shielding effects by reducing the overall implant stiffness and facilitating bone ingrowth through interconnected pores, resulting in a high surface-area-to-volume ratio. However, reducing stiffness often compromises the yield and fatigue strength of the implant. This article uses the design of experiments method for optimization of lattice structures, with analysis of variance to validate the results. Influence of design parameters, such as pore size, strut diameter, and lattice type, that is, octet and face body centered cubic (FBCCZ), is analyzed to achieve a high yield-strength-to-stiffness ratio. The optimal configuration is identified as an octet lattice with a 0.4 mm strut diameter and 0.9 mm pore size, producing mechanical properties comparable to the surrounding bone. Optimized Ti6Al4V lattice structures are fabricated using selective laser melting and tested under quasistatic compression. The fatigue analysis is performed using finite element simulations, according to ISO 7204-6, and the factor of safety as per Soderberg criterion is evaluated as 2.37, corresponding to 50 million cycles.

Currently, with the rapid development of electronic technology, electronic products are becoming increasingly used in both military and civilian fields. Technology is a double-edged sword. While it brings convenience to people, it also brings risks. The use of electronic products brings electromagnetic radiation. Therefore, studying the absorption of electromagnetic waves by microwave absorption materials is of great research significance. At present, common carbon-based microwave absorption materials include carbon fiber, graphene, carbon nanotubes, carbon black, etc. However, the complex preparation process and high cost limit its use. In contrast, biomass-derived materials are receiving widespread attention due to their green and environmentally friendly characteristics as well as abundant carbon sources. This review highlights the preparation approaches of biomass-derived carbon and systematically analyzes recent progress in composite biomass carbon-based microwave absorption materials. These composite materials are typically prepared by combining biomass as a carbon source with magnetic materials, conductive polymers, and transition metal oxides. In the future, biomass materials will have good application scenarios in the field of electromagnetic absorption.

Herein, the tensile and creep properties of a weldable Ni-based wrought superalloy specifically engineered to endure service temperatures surpassing 800 °C have been investigated. The alloy overcomes the dilemma of conflicting welding and mechanical properties, showcasing remarkable weldability alongside sustained superior mechanical performance. At ambient temperature, the alloy boasts a tensile strength of 1390 MPa, while maintaining a commendable strength of 850 MPa at 800 °C. The creep response under 800 °C/200 MPa conditions unfolds in three stages, marked by an extended period of steady-state stage spanning over 210 h. Notably, both the minimum steady-state creep rate and creep rupture strength surpass those of other conventional wrought, weldable superalloys, such as Haynes 282. The superior creep resistance is likely due to the synergistic effect of the Orowan looping and the shearing of stacking faults. The electron backscattered diffraction analysis shows that during the creep process of the alloy, the proportion of high Schmid factors increases, allowing more grains to meet the conditions for dislocation slip and leading to the acceleration of plastic deformation. After creep, the proportion of twin boundaries decreases, and the obstacle effect of the alloy on dislocations is significantly weakened.

Aluminum-fly ash cenosphere (Al-FAC) syntactic foams with magnesium (Mg) additions are fabricated via vacuum-assisted infiltration, and their compressive behaviors and energy absorption capacity are investigated over the temperature ranged from room temperature to 650 °C. Compared to Mg-free Al-FAC foam, modified foams exhibit pronounced stress drops attributed to brittle phase fracture and shear band formation. In addition, the compressive strength and energy absorption are up to 148.0 MPa and 54.6 J cm⁻³, corresponding to significant enhancements of 99.2% and 45.6%, respectively, for modified foams. Syntactic foams exhibit higher yield stress than the matrix at 300 °C despite progressive strength degradation at elevated temperatures, accompanied by increasing critical strain for stress drops. Above 300 °C, matrix softening induces a brittle-to-ductile transition that reduces stress fluctuations, while hollow spheres retain brittle fracture and interfacial coatings suppress debonding to preserve structural integrity. At 600 °C, the compressive strength and energy absorption are retained at 24.7 MPa and 8.0 J·cm⁻³. A modified Johnson–Cook model captures the exponential decay of yield stress with temperature. Concurrently, energy absorption efficiency rises with temperature due to delayed densification and plateau stress stabilization. Microstructural and fracture characterization confirms the integrity of interfacial coatings at high temperatures, effectively suppressing hollow spheres debonding.

Conventional fabrication of Ti-6Al-4V/Ni-Ti bimetallic structures is both costly and impractical for complex geometries. In this study, to resolve these difficulties, multi-wire arc additive manufacturing (M-WAAM) with in situ alloying is used. The results show that NiTi₂ phase reduces ductility and induces stress concentration due to lattice mismatch with the NiTi phase, further accelerating crack formation. The as-built wall consists of NiTi₂ and NiTi layers, formed through element diffusion, with the interface evolving from a basket-weave microstructure to a eutectic α-Ti + NiTi₂ phase and ultimately a planar NiTi₂ structure. Besides, as-built wall exhibits a peak microhardness of 692.2 HV, a compressive strength of 1137.5 ± 31 MPa, and a fracture strain of 6.7% ± 2%. This study presents an efficient strategy for fabricating complex bimetallic structures, providing insights into integrated manufacturing of dissimilar metals for aerospace and related applications.

TiN coatings deposited via high power impulse magnetron sputtering technology exhibit a dense microstructure, high hardness, and adhesion strength, enhancing the longevity of engineering components. This study systematically investigates the influence of N₂ flow rate on the microstructure and mechanical properties of TiN coatings while maintaining a fixed Ar flow rate of 60 sccm and a substrate bias of −120 V. Results indicate that as the N₂ flow rate increases, the surface morphology transitions from irregular shapes to pyramidal and eventually to tetrahedral shapes, while the cross-sectional structure remains dense. The preferred orientation shifts from TiN (111) to TiN (200) with N₂ flow rate increasing. Notably, the coatings achieve peak hardness (about 28.2 GPa) and elastic modulus (about 269.8 GPa) at an N₂ flow rate of 25 sccm, alongside maximum compressive residual stress (about 5.09 GPa). Adhesion strength ranges from 47.6 to 61.2 N, demonstrating superior adhesion to the substrate. This research provides a theoretical for future investigations into the application of TiN coatings in various industrial contexts, highlighting their exceptional mechanical properties and potential for improved performance.

Lattice structures can enhance mechanical properties while minimizing mass, but often face challenges from inefficient material distribution and stress concentrations. Here, a generative design method is used to create freeform lattices that resemble biological structures. This approach is found to provide less constrained material redistribution, allowing the reduction of stress concentrations embedded in conventional designs. Three lattice types are optimized and compared: the bending-dominated body-centered cubic (BCC) lattice, the stretching-dominated simple cubic lattice, and a directional, water-lily-inspired lattice. Compression testing reveals improvements in stiffness, strength, and energy absorption in all three lattice types at sufficiently high relative density. Interestingly, all optimized structures display a marked reduction in anisotropy, with an optimized BCC lattice exhibiting isotropic elasticity. This study shows how generative design can emulate the organic forms of nature to create lattices with superior properties, offering new pathways for lightweight, high-performance structures.