Search Results (1,227)

The present study focused on 10 wt.% TiB₂@Ti/AlCoCrFeNi_2.1 eutectic high-entropy alloy matrix composites (EHEAMCs), which were treated with furnace cooling (FC), air cooling (AC), and water cooling (WC) after being held at 1000 °C for 12 h, aiming to investigate the effect of cooling methods on their microstructure and mechanical properties. The results showed that the composites in all states consisted of FCC phase, BCC phase, TiB₂ phase, and Ti phase. The cooling methods did not change the phase types but affected the diffraction peak characteristics. With the increase in cooling rate, the diffraction peaks of FCC and BCC phases gradually separated from overlapping, and the diffraction peak of the FCC (111) crystal plane shifted to a lower angle (due to the increase in lattice constant caused by Ti element diffusion), while the diffraction peak intensity showed a downward trend. In terms of microstructure, all composites under the three cooling conditions were composed of eutectic matrix, solid solution zone, and grain boundary zone. The cooling rate had little effect on the morphology but significantly affected the element distribution. During slow cooling (FC, AC), Ti and B diffused sufficiently from the grain boundary to the matrix, resulting in higher concentrations of Ti and B in the matrix (Ti in FCC phase: 7.4 at.%, B in BCC phase: 8.1 at.% in FC state). During rapid cooling (WC), diffusion was inhibited, leading to lower concentrations in the matrix (Ti in FCC phase: 4.6 at.%, B in BCC phase: 4.3 at.%), but the element distribution was more uniform. Mechanical properties decreased with the increase in cooling rate: the FC state showed the optimal average hardness (627.0 ± 26.1 HV), yield strength (1574 MPa), fracture strength (2824 MPa), and fracture strain (24.2%); the WC state had the lowest performance (hardness: 543.2 ± 35.4 HV and yield strength: 1401 MPa) but was still better than the as-sintered state. Solid solution strengthening was the main mechanism, and slow cooling promoted element diffusion to enhance lattice distortion, achieving the synergistic improvement of strength and plasticity. Full article

The development of lightweight steels with high specific strength is critical for automotive applications and energy savings. This study aimed to develop a high-performance lightweight steel with high specific strength by designing an alloy composition and optimizing thermomechanical processing. A novel Fe-28.6Mn-10.2Al-1.1C-3.2Ni-3.9Cr (wt.%) steel was investigated, focusing on microstructural evolution, mechanical properties, and strengthening mechanisms. The steel was processed through hot-rolling, solution treatment, cold-rolling, and subsequent annealing. Microstructural characterization revealed a dual-phase matrix of austenite and ferrite (6.8 vol.%), with B2 precipitates distributed at the grain boundaries and within the austenite matrix, alongside nanoscale κ-carbides (<10 nm). Short-time annealing resulted in the finer austenite grains (~1.1 μm) and the higher volume fraction (5.0%) of intragranular B2 precipitates with a smaller size (~0.18 μm), while long-time annealing promoted the coarsening of austenite grains (~1.6 μm) and the growth of intergranular B2 particles (~0.9 μm). This steel achieved yield strengths of 1130~1218 MPa and tensile strengths of 1360~1397 MPa through multiple strengthening mechanisms, including solid solution strengthening, grain boundary strengthening, dislocation strengthening, and precipitation strengthening. Full article

The increasing demand for lightweight and high-performance brake rotors has led to the exploration of aluminum–metal matrix composites (Al-MMCs) as alternatives to conventional cast iron rotors. This study evaluated the tribological performance of squeeze-cast Al-MMC brake rotors using an AK Master dynamometer test and compared it with that of conventional gray cast iron (GCI) rotors. The Al-MMC rotors demonstrated stable coefficients of friction (CoFs) with reduced wear rates, compared to the GCI rotors. Surface analysis identified the predominant wear mechanisms, including abrasive and oxidative wear. The Al-MMC rotors exhibited sensitivity to pressure and speed, with a CoF range of 0.35–0.47 that decreased at higher pressures and speeds, whereas the GCI rotors maintained a stable CoF range of 0.38–0.44. At elevated temperatures, the GCI rotors displayed superior thermal stability and fade resistance compared to the Al-MMCs, which experienced a 40–60% loss in CoF. Wear analysis indicated material transfer from brake pads to Al-MMC rotors, resulting in protective tribofilm formation, whereas GCI rotors exhibited conventional abrasive wear. These findings highlight the potential of squeeze-cast Al-MMCs for automotive braking applications, offering advantages in weight reduction and wear resistance, but also suggest the need for further material optimization to enhance high-temperature performance and friction stability. Full article

This research explores the effect of a composite support of SiO₂ and Al₂O₃ with Fe and Co incorporated as catalysts for Fischer–Tropsch synthesis (FTS) using a 3D-printed stainless steel (SS) microchannel microreactor. Two mesoporous catalysts, FeCo/SiO₂Al₂O₃ and Co/SiO₂Al₂O₃, were synthesized via a one-pot (OP) method and extensively characterized using N₂ physisorption, XRD, SEM, TEM, H₂-TPR, TGA-DSC, FTIR, and XPS. H₂-TPR results revealed that the synthesis method significantly affected the reducibility of metal oxides, thereby influencing the formation of active FTS sites. SEM-EDS and TEM further revealed a well-defined hexagonal matrix with a porous surface morphology and uniform metal ion distribution. FTS reactions, carried out in the 200–350 °C temperature range at 20 bar with a H₂/CO molar ratio of 2:1, exhibited the highest activity for FeCo/SiO₂Al₂O₃, with up to 80% CO conversion. Long-term stability was evaluated by monitoring the catalyst performance for 30 h on stream at 320 °C under identical reaction conditions. The catalyst was initially active for the methanation reaction for up to 15 h, after which the selectivity for CH₄ declined. Correspondingly, the C₄⁺ selectivity increased after 15 h of time-on-stream, indicating a shift in the product distribution toward longer-chain hydrocarbons. This trend suggests that the catalyst undergoes gradual activation or restructuring under reaction conditions, which enhances chain growth over time. The increase in C₄⁺ products may be attributed to the stabilization of the active sites and suppression of methane or light hydrocarbon formation. Full article

The mismatch of the coefficient of thermal expansion (CTE) between the reinforcement and the matrix leads to thermal residual stresses and defects upon cooling from the processing temperature to room temperature. The residual stresses and defects have a significant impact on the mechanical properties of metal-matrix composites. To investigate the effect of cooling temperature on the residual stresses’ distribution and mechanical properties of SiC/Al, we investigated the cooling process of SiC/Al from different initial temperatures to room temperature. We found that residual stresses mainly distributed in the interface of SiC/Al composites after cooling, and the higher the initial temperature of cooling, the higher the value of residual stresses and the greater the degree of atomic displacement. During the cooling process, the Shockley partials and stair-rod dislocations were the two dominant dislocation structures. After cooling, the length of Shockley partials was about 80% and the length of stair-rod dislocations was about 18%. The mechanical properties of SiC/Al composites reduced after cooling. These results have filled the gap in understanding the mechanism of defect evolution in SiC/Al composites under cooling conditions, as well as the influence of cooling conditions on the mechanical properties of the material. Full article

This study investigates on Zn-Al alloy microstructural characteristics and mechanical properties of a Zn-Al alloy with calcium (Ca) additions ranging from 0.5 to 1.5 wt.%. The base alloy composition is 94.95 wt.% Zn, 4.0 wt.% Al, 1.0 wt.% Cu, and 0.05 wt.% Mg, and it is utilized in various engineering applications, including domestic and automotive. The alloys were fabricated under controlled atmospheric conditions using the traditional squeeze casting technique. The squeeze-cast Zn-Al alloys with varying Ca content were characterized through chemical analysis, optical microscopy (OM), scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and X-ray diffraction (XRD) analysis. The microstructure of the Zn-Al alloy with Ca reinforcement comprises the intermetallic phase CaZn₁₃, which is distributed within the Zn-Al solid solution. The CaZn₁₃ phase within the Zn matrix exhibited a synergistic effect on grain refinement, resulting in a 96% reduction in grain size, as confirmed by SEM analysis. The mechanical properties of the Zn-Al alloy reinforced with calcium significantly enhanced microhardness and tensile strength. The results indicated that calcium additions up to 1.5 wt.% increased both microhardness and tensile strength, with the 1.0 wt.% calcium addition yielding the highest hardness value of 141 HV0.1 and a tensile strength of 359 MPa compared to the base alloy. These findings suggest that adding calcium enhances the grain refinement and mechanical properties of Zn-Al alloys. Full article

Boron (B) is widely used as a neutron-absorbing nuclide and has significant applications in the nuclear industry. B₄C/Al composites combine the high hardness of B₄C with the ductility of Al, making them commonly used neutron-absorbing materials. Under current preparation methods, the poor wettability and low reactivity of B₄C with molten Al limit its effective incorporation into the matrix, and the addition of B₄C in B₄C/Al composites has reached its threshold limit, making it difficult to achieve breakthrough improvements in neutron absorption performance. However, incorporating additional B elements into the B₄C/Al composite can break this limit, effectively enhancing the material’s neutron absorption performance. Nevertheless, research on the impact of this addition on the mechanical properties of the composite remains unclear. The requirements for B₄C/Al composites as spent fuel storage and transportation devices include high mechanical strength and certain machinability. This study fabricated B₄C/Al composites with varying B contents (5 wt.%, 10 wt.%, and 15 wt.%), and the influence of B addition on the microstructure and mechanical properties of B₄C/Al composites was investigated. The results demonstrate that the composites exhibit a density of approximately 99% with well-established interfacial bonds. Increasing B content leads to a higher quantity of interfacial reaction products Al₃BC and AlB₂, enhancing the Vickers hardness to 370.93 HV. The bending strength and fracture toughness of composites with 5 wt.% and 15 wt.% B addition decreased, whereas those with 10 wt.% B exhibited excellent resistance to crack growth and high-temperature plastic deformation due to a high content of ductile phase. Full article

This study addresses the critical challenges of interfacial stress mismatch, fiber degradation, and unstable clad geometry in manufacturing continuous carbon fiber-reinforced aluminum composites (Cf/Al) via laser cladding, driven by rapid thermal gradients. A dual-ellipsoid heat source-based thermoelastic–plastic finite element model was developed in Abaqus, integrating phase-dependent material properties and latent heat effects to simulate multi-physics interactions during single-track deposition, resolving transient temperature fields peaking at 1265 °C, and residual stresses across uncoated and Ni-coated fiber configurations. The work identifies an optimal parameter window characterized by laser power ranging from 700 to 800 W, scan speed of 2 mm/s, and spot radius of 3 mm that minimizes thermal distortion below 5% through gradient-controlled energy delivery, while quantitatively demonstrating nickel interlayers’ dual protective role in achieving 42% reduction in fiber degradation at 1200 °C compared to uncoated systems and enhancing interfacial load transfer efficiency by 34.7%, thereby reducing matrix tensile stresses to 159 MPa at fiber interfaces. Experimental validation confirms the model’s predictive capability, revealing nickel-coated systems exhibit superior thermal stability with temperature differentials below 12.6 °C across interfaces and mechanical interlocking, achieving interfacial void fractions under 8%. These results establish a process–structure linkage framework, advancing defect-controlled composite fabrication and providing a digital twin methodology for aerospace-grade manufacturing. Full article

Phosphor-in-glass (PiG) composites are promising materials for applications in various fields of material engineering. There are competing methods of preparation of PiGs which result in materials with different structural and performance characteristics. The glass-crystal composites comprising tellurite-zinc-sodium glass (TZN) and perovskite LaAlO₃ doped with Eu³⁺ (LAO:Eu) are prepared using three distinct methods: remelt, direct-doping and co-sintering, in order to evaluate the impact of the preparation method on the structural, optical and luminescence properties of the novel phosphor-in-glass (PiG) composites. The composites prepared by the remelt and direct-doping method suffer from the decomposition of LAO:Eu and Eu³⁺ ion diffusion into the glass matrix. The highest rate of preservation and luminescence intensity of LAO:Eu is achieved in the composites prepared by the co-sintering method. Unfortunately, the loss of transparency is substantial. This article demonstrates the challenges and tradeoffs that are yet to be resolved in preparation of PiG composites. The preservation of the crystalline phase leads to the lower transparency of the final material. Full article

Drilling-induced damage in fiber-reinforced polymer composite materials was measured excavating four laminates, basalt (B₁₄), glass (G₁₄) and their two sandwich type hybrids (B₄G₆B₄, G₄B₆G₄), with 6 mm twist drills at 1520 revolutions per minute and 0.10 mm rev⁻¹ under dry running with an uncoated high-speed steel (HSS-R), grind-coated high-speed steel (HSS-G) or physical vapor deposition-coated (high-speed steel coated with Titanium Nitride (TiN) and Titanium Aluminum Nitride (TiAlN)) drill bits. The hybrid sheets were deliberately incorporated to clarify how alternating basalt–glass architectures redistribute interlaminar stresses during drilling, while the hard, low-friction TiN and TiAlN ceramic coatings enhance cutting performance by forming a heat-resistant tribological barrier that lowers tool–workpiece adhesion, reduces interface temperature, and thereby suppresses thrust-induced delamination. Replacement of an uncoated, grind-coated, high-speed-steel drill (HSS-G) with the latter coats lowered the mechanical and thermal loads substantially: mean thrust fell from 79–94 N to 24–30 N, and peak workpiece temperatures from 112 °C to 74 °C. Accordingly, entry/exit oversize fell from 2.5–4.7% to under 0.6% and, from the surface, the SEM image displayed clean fiber severance rather than pull-out and matrix smear. By analysis of variance (ANOVA), 92.7% of the variance of thrust and 86.6% of that of temperature could be accounted for by the drill-bit factor, thus confirming that the coatings overwhelm the laminate structure and hybrid stacking simply redistribute, but cannot overcome, the former influence. Regression models and an artificial neural network optimized via meta-heuristic optimization foretold thrust, temperature and delamination with an R² value of 0.94 or higher, providing an instant-screening device with which to explore industrial application. The work reveals TiAlN- and TiN-coated drills as financially competitive alternatives with which to achieve ±1% dimensional accuracy and minimum subsurface damage during multi-material composite machining. Full article

A series of studies was conducted on the functional and structural characteristics of polymer composite materials (PCMs) based on silicone polymers modified with multi-walled carbon nanotubes (MWCNTs) and metallic particles (CuAl or Al). The influence of the structural parameters of carbon and metallic inclusions in the polymer matrix on the electrophysical and thermophysical properties of the composites was demonstrated. Various conduction mechanisms dominating in the inverse temperature ranges of 50 K^–1–13 K^–1, 13 K^–1–6 K^–1, and 6 K^–1–2 K^–1 were identified. The operational modes of the polymer composites as active materials for thermoregulating coatings were established. The highest temperature of 32.9 °C in operating mode and the shortest warm-up time of 180 s were observed in the composite modified with 4 wt.% CNTs and 10 wt.% bronze particles at a supply voltage of 10 V. The characteristics of the composites under atomic oxygen (AO) exposure with a fluence of 3 × 10²¹ atoms/cm² was evaluated, confirming their functionality, particularly for potential space applications. The composites demonstrated nearly complete retention of their functional characteristics. The aim of this study was to develop electrically conductive functional composites based on silicone polymers containing MWCNTs and metallic particles inclusions for creating electric heating elements with tailored functional characteristics. Full article

To address the critical challenge of synergistically enhancing both high-temperature mechanical properties and thermal conductivity in neutron-absorbing materials for dry storage of spent nuclear fuel, this study proposes an innovative strategy. This approach involves the controlled distribution, size, and crystalline states of nano-Al₂O₃ within an aluminum matrix. By combining plastic deformation and heat treatment, we aim to achieve a structurally integrated functional design. A systematic investigation was conducted on the microstructural evolution of Al₂O₃/10 wt.% B₄C/Al composites in their forged, extruded, and heat-treated states. We also examined how these states affect high-temperature mechanical properties and thermal conductivity. The results indicate that applying hot extrusion deformation along with optimized heat treatment parameters (500 °C for 24 h) allows for a lamellar dispersion of nano-Al₂O₃ and a crystallographic transition from amorphous to γ-phase. As a result, the composite demonstrates a tensile strength of 144 MPa and an enhanced thermal conductivity of 181 W/(m·K) at 350 °C. These findings provide theoretical insights and technical support for ensuring the high density and long-term safety of spent fuel storage materials. Full article

The dispersion behavior of ceramic particles in aluminum alloys during rapid solidification critically affects the resulting microstructure and mechanical performance. In this study, we investigated the nucleation and growth of Al₃(Sc,Zr) on TiB₂ surfaces in a 2TiB₂/Al–8Ni–0.6Sc–0.1Zr alloy, fabricated via wedge-shaped copper mold casting and laser surface remelting. Thermodynamic calculations were employed to optimize alloy composition, ensuring sufficient nucleation driving force under rapid solidification conditions. The results show that the formation of Al₃(Sc,Zr)/TiB₂ composite interfaces is highly dependent on cooling rate and plays a pivotal role in promoting uniform TiB₂ dispersion. At an optimal cooling rate (~1200 °C/s), Al₃(Sc,Zr) nucleates heterogeneously on TiB₂, forming core–shell structures and enhancing particle engulfment into the α-Al matrix. Orientation relationship analysis reveals a preferred (111)α-Al//(0001)TiB₂ alignment in Sc/Zr-containing samples. A classical nucleation model quantitatively explains the observed trends and reveals the critical cooling-rate window for composite interface formation. This work provides a mechanistic foundation for designing high-performance aluminum-based composites with uniformly dispersed reinforcements for additive manufacturing applications. Full article

A facile and versatile strategy to obtain NPs@ZnAlO nanocomposite materials, comprising controlled-size nanoparticles (NPs) within a ZnAlO matrix is reported. The mono-(Au, Ni) and bimetallic (Ni-Au) NPs serving as an active phase were prepared by the polyol-alkaline method, while the ZnAlO support was obtained via the thermal decomposition of its corresponding layered double hydroxide (LDH) precursors. X-ray diffraction (XRD) patterns confirmed the successful fabrication of the nanocomposites, including the synthesis of the metallic NPs, the formation of LDH-like structure, and the subsequent transformation to ZnO phase upon LDH calcination. The obtained nanostructures confirmed the nanoplate-like morphology inherited from the original LDH precursors, which tended to aggregate after the addition of gold NPs. According to the UV-Vis spectroscopy, loading NPs onto the ZnAlO support enhanced the light absorption and reduced the band gap energy. ATR-DRIFT spectroscopy, H₂-TPR measurements, and XPS analysis provided information about the functional groups, surface composition, and reducibility of the materials. The catalytic performance of the developed nanostructures was evaluated by the photodegradation of bisphenol A (BPA), under simulated solar irradiation. The conversion of BPA over the bimetallic Ni-Au@ZnAlO reached up to 95% after 180 min of irradiation, exceeding the monometallic Ni@ZnAlO and Au@ZnAlO catalysts. Its enhanced activity was correlated with good dispersion of the bimetals, narrower band gap, and efficient charge carrier separation of the photo-induced e⁻/h⁺ pairs. Full article

This paper examines the wettability and interactions between ceramic and composite materials soldered with Bi-based solder containing 11 wt.% of silver and 3 wt.% titanium using indirect electron beam soldering technology. The Bi11Ag3Ti solder, with a melting point of 402 °C, consisted of a bismuth matrix containing silver lamellae. Titanium, acting as an active element, positively influenced the interaction between the solder and the joined materials. SiC and Ni-SiC substrates were soldered at temperatures of 750 °C, 850 °C, and 950 °C. Measurements of wettability angles indicated that the lowest value (20°) was achieved with SiC substrates at 950 °C. A temperature of 750 °C appeared to be the least suitable for both substrates and was entirely unsuitable for Ni-SiC. It was also observed that the Bi11Ag3Ti solder wetted the SiC substrates more effectively than Ni-SiC substrates. The optimal working temperature for this solder was determined to be 950 °C. The shear strength of the joints soldered with the Bi11Ag3Ti alloy was 23.5 MPa for the Al₂O₃/Ni-SiC joint and 9 MPa for the SiC/Ni-SiC joint. Full article