Advanced Engineering Materials最新文献

Achieving the stability of pore structure and the enhancement of mechanical properties is the prominent target for aluminum (Al) foam design. In this work, the effects of manganese (Mn) content on the pore structure, mechanical properties, and deformation behavior of AlMn foams are investigated. The results show that the appropriate addition of Mn (1.5 wt%) achieves a remarkable balance between energy absorption capacity (4.37 MJ m⁻³) and pore uniformity (standard deviation of 0.95 mm in average pore size), representing substantial enhancements of 193.28% in yield strength and 385.56% in energy absorption capacity compared to pure Al foams. These enhancements are attributed to a refined pore architecture, finely dispersed Al₆Mn precipitates, and a sequential collapse mechanism, which collectively enable progressive energy dissipation. The application of the entropy weight method is pioneered in this study to establish a predictive framework for multiobjective design, demonstrating that energy absorption and pore uniformity are crucial factors for the matrix design of Al foams. These findings offer a potential strategy for future engineering applications of metal foam design.

Chemical interdiffusion at interfaces is inevitable and often detrimental in devices subjected to temperature gradients or electrical currents with Joule heating. Identifying diffusion barriers that ensure mechanical durability, stable electrical conduction, and resistance to intermetallic formation remains a key challenge. Here, the medium-entropy alloys (MEAs) guided by thermodynamic engineering as robust alternatives to conventional Ni layers are exploited. By experimentally establishing phase equilibria at 1273 K, a single-phase β-Ti region within the Ti₇₀-Al–Cr–V system is identified. Microstructural and mechanical assessments further delineates an optimal compositional window for Ti-rich alloys suitable as diffusion barriers. Selected Ti₇₀AlCrV alloys exhibit low density and moderate hardness an advantageous balance that minimizes weight while ensuring mechanical integrity. To evaluate functionality, Ni and Ti-rich MEA thin films are deposited on n-type PbTe substrates and integrate into single-leg thermoelectric devices. Remarkably, Ti-rich MEA barriers impart superior thermal stability, sustaining conversion efficiencies above 1.91% under a 200 K temperature gradient. Significantly, the single-phase Ti-rich MEA thin film effectively suppresses interfacial intermetallic growth, attributed to their ability to curb diffusion-driven reactions. This work advances the design of MEAs and highlights their promise as diffusion barriers for scalable thermoelectric technologies.

Multimodal Solidification Characterization

In their Research Article (10.1002/adem.202501408), Nikhilesh Chawla and co-workers demonstrate the first simultaneous, time-resolved 4D X-ray microtomography and energy-dispersive diffraction analysis of Sn-Bi solder alloy solidification. The multimodal approach captures the nucleation and faceted growth of primary Bi crystals, the formation of Sn dendrites, and eutectic microstructures, while correlating diffraction peak intensities with phase volume fractions. These insights enable a deeper, quantitative understanding of microstructural evolution and strain development during alloy solidification.

Owing to their efficient multifunctional responses, multiferroics have secured a notable position for use in sensors, memory, and spintronic devices. Herein, highly crystalline forms of BiFeO₃, PbZr_0.58Ti_0.42O₃, and MnFe₂O₄ are obtained through hydrothermal, solid-state, and sol–gel autocombustion methods, respectively. A triphasic composite series with the formula 0.9[(1–x)BiFeO₃ + xPbZr_0.58Ti_0.42O₃ + 0.1MnFe₂O₄ (x = 0.0–0.3, interval 0.1) is then prepared using the solid-state route. X-ray diffraction confirms the coexistence of rhombohedral-distorted perovskite phases (BiFeO₃ and PbZr_0.58Ti_0.42O₃) alongside the cubic spinel phase (MnFe₂O₄). Field-emission scanning electron microscopy reveals porous surfaces with spherical and irregular grain morphologies. Ferroelectric analysis demonstrates a maximum polarization of 3.736 × 10⁻³ μC cm⁻², with the highest energy-storage efficiency of 70.76% and minimal energy loss density (0.1498 μJ cm⁻³) for the x = 0.2 composition, making it suitable for energy storage and memory applications. Positive-up negative-down analysis confirms significant variations in switching charge density across all composites. Meanwhile, magnetic hysteresis studies demonstrate soft ferromagnetic behavior dominated by the MnFe₂O₄ phase, with optimal response in x = 0.3 sample with M_max ≈ 0.38 emu g⁻¹, M_r = 0.019 emu g⁻¹, and H_c = 160 Oe. By harnessing these parameters, the x = 0.2 composition emerges as optimal for energy storage, while the x = 0.3 composition stands out for magnetic device applications.

Schwarzites are 3D carbon allotropes with negative Gaussian curvatures. Herein, the ballistic impact resistance and structures experimentally and energy-absorption capabilities of schwarzites from the gyroid and primitive families are investigated. Atomic and their corresponding 3D-printed structural models are investigated. In the schwarzite family, Ω₂ and Ψ₂ have sustained the impact with minimal damage. The tested structures are further scanned using computer tomography to reveal and investigate their internal damage features. Molecular dynamics simulation results are in good agreement with the impact tests of the 3D-printed structures, suggesting that the mechanical properties are determined mainly by the topological features and are scale-independent. The results point out that the performance of schwarzites structures is related to their local curvature, i.e., their flatness due to their ratio of hexagons to octagons. In general, the lower the ratio of hexagons to octagons, the stiffer the structure. Controlled mechanical response is possible by designing hierarchical schwarzite structures, making these structures good candidates for applications requiring lightweight materials with high resistance to ballistic impacts.

Although porous aluminum (Al) possesses pore damping characteristics, its damping performance is still unsatisfactory, which limits its further application in vibration reduction and noise reduction. To address this issue, this study utilizes powder metallurgy technology to incorporate graphite (Gr) into porous aluminum. The porous Gr/Al composite prepared by this method has the characteristics of both lightweight and high damping. In porous Gr/Al composites, there exist not only a large number of closed-cell type pores but also numerous Alp/Alp and Gr/Alp interfaces. The yield strength of the porous Gr/Al composites gradually decreases with increasing ammonium bicarbonate (NH₄HCO₃) and graphite content. Damping tests indicate that both the internal friction (IF) values and the equivalent IF values of the porous Gr/Al composites increase as the ammonium bicarbonate and graphite content rise. At room temperature, the IF value of the Al–10Gr–10N sample is 72% superior to that of the Al–0Gr–10 N sample. At 250 °C, the IF value of the Al–10Gr–10N sample is 99.1% superior to that of the Al–0Gr–10 N sample. The synergistic enhancement effects of the high intrinsic damping characteristics of graphite, pore damping, and interface damping enable the porous Gr/Al composites to have favorable damping performance.

In the aerospace, nuclear, and machining industries, alloys require high hardness and excellent wear rate. Most high-performance alloys rely on cobalt for high-temperature properties, despite its political, ethical, and health concerns. High-entropy alloys (HEAs), enabled by structural hardening, lattice distortion, and sluggish diffusion, offer pathways to eliminate this critical element. This study examines cobalt substitution in HEAs to optimize hardness and wear rate. New alloys based on the Cantor system (CoCrFeMnNi) are produced by individually replacing cobalt with copper, aluminum, vanadium, or molybdenum. Four equiatomic HEAs (AlCrFeMnNi, CrFeMnNiV, CrCuFeMnNi, and CrFeMnMoNi) are compared with two literature alloys (Al_0.2Co_1.5CrFeNi_1.5Ti and CoCrFeMnNi) and with the pure substituent elements, all evaluated in the same metallurgical state. All synthesized HEAs except CoCrFeMnNi are multiphased and do not mimic the structure of their corresponding pure element; CrCuFeMnNi also departs from valence electron concentration predictions. Pure cobalt shows the lowest wear rate, while the Cantor alloy exhibits a higher one. Aluminum, vanadium, and molybdenum strengthen HEAs despite limited performance in their pure state. Ultimately, pure cobalt, CrFeMnMoNi, and AlCrFeMnNi display similar and superior wear rate compared with the optimized reference alloy Al_0.2Co_1.5CrFeNi_1.5Ti.

In the aerospace, nuclear, and machining industries, alloys require high hardness and excellent wear rate. Most high-performance alloys rely on cobalt for high-temperature properties, despite its political, ethical, and health concerns. High-entropy alloys (HEAs), enabled by structural hardening, lattice distortion, and sluggish diffusion, offer pathways to eliminate this critical element. This study examines cobalt substitution in HEAs to optimize hardness and wear rate. New alloys based on the Cantor system (CoCrFeMnNi) are produced by individually replacing cobalt with copper, aluminum, vanadium, or molybdenum. Four equiatomic HEAs (AlCrFeMnNi, CrFeMnNiV, CrCuFeMnNi, and CrFeMnMoNi) are compared with two literature alloys (Al_0.2Co_1.5CrFeNi_1.5Ti and CoCrFeMnNi) and with the pure substituent elements, all evaluated in the same metallurgical state. All synthesized HEAs except CoCrFeMnNi are multiphased and do not mimic the structure of their corresponding pure element; CrCuFeMnNi also departs from valence electron concentration predictions. Pure cobalt shows the lowest wear rate, while the Cantor alloy exhibits a higher one. Aluminum, vanadium, and molybdenum strengthen HEAs despite limited performance in their pure state. Ultimately, pure cobalt, CrFeMnMoNi, and AlCrFeMnNi display similar and superior wear rate compared with the optimized reference alloy Al_0.2Co_1.5CrFeNi_1.5Ti.

Reduced graphene oxide (rGO) reinforced copper (Cu) matrix composites were produced using arc induction melting (AIM) to investigate the microstructural, mechanical, tribological, and electrical responses of the system. rGO additions of 0.5 and 1.0 wt% were introduced to clarify interfacial strengthening and functional synergies within the Cu matrix. Characterization through X-ray Diffraction, Scanning Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, Atomic Force Microscopy, and Lateral Force Microscopy confirmed homogeneous rGO dispersion, refined grain structure, and the absence of undesirable secondary phases. Incorporating rGO led to a significant increase in hardness, rising from 65 ± 4HV30 for pure Cu to 225 ± 3HV30 for the composite containing 1 wt% rGO. This improvement is associated with Hall–Petch strengthening, Orowan looping, and effective interfacial load transfer. Tribological evaluations demonstrated up to 78% reduction in wear rate and more than 60% decrease in friction coefficient, linked to the formation of a stable, self-lubricating carbonaceous tribofilm. SEM/EDX analyses of worn surfaces confirmed the presence of a continuous protective carbon layer. Electrical conductivity showed a slight improvement, maintaining the structural integrity of the Cu–rGO interface. Overall, AIM proved to be a scalable and energy-efficient approach for fabricating dense and multifunctional Cu–rGO nanocomposites suitable for electromechanical and thermal management applications.