Search Results (34)

This study investigates the fabrication and residual stress behavior of a 0.5 wt.% graphene-reinforced AA2195 aluminum matrix composite, developed for advanced aerospace structural applications. The composite was synthesized via squeeze casting, followed by a multi-pass hot rolling process and subsequent T8 heat treatment. The evolution of residual stress was systematically examined after each rolling pass and during thermal treatments. The successful incorporation of graphene into the matrix was confirmed through Energy-Dispersive Spectroscopy (EDS) analysis. Residual stress measurements after each pass revealed a progressive increase in compressive stress, reaching a maximum of −68 MPa after the fourth hot rolling pass. Prior to the fifth pass, a solution treatment at 530 °C was performed to dissolve coarse precipitates and relieve internal stresses. Cold rolling during the fifth pass reduced the compressive residual stress to −40 MPa, and subsequent artificial aging at 180 °C for 48 h further decreased it to −23 MPa due to recovery and stress relaxation mechanisms. Compared to the unreinforced AA2195 alloy in the T8 condition, which exhibited a tensile residual stress of +29 MPa, the graphene-reinforced composite in the same condition retained a compressive residual stress of −23 MPa. This represents a net improvement of 52 MPa, highlighting the composite’s superior capability to retain compressive residual stress. The presence of graphene significantly influenced the stress distribution by introducing thermal expansion mismatch and acting as a barrier to dislocation motion. Overall, the composite demonstrated enhanced residual stress characteristics, making it a promising candidate for lightweight, fatigue-resistant aerospace components. Full article

This study examined machinability aspects in terms of the main cutting force and surface roughness in dry CNC turning of graphene-reinforced composite aluminum with 0.5 wt%. The cutting speed, feed rate and depth of cut influence were investigated in regard to the responses of main cutting force Fz and surface roughness Ra when turning high-purity aluminum (Al 96.83%) and graphene-reinforced aluminum with 0.5% graphene nanoplatelets for comparative analysis. A customized central composite design of the experiments with nine runs was established, and the results were assessed through analysis of variance and response surface regression. Full quadratic prediction models were generated based on the experimental results and they were examined for their validity and efficiency in predicting the response of the main cutting force and surface roughness of the machined graphene-reinforced composite aluminum. The NSGA-II algorithm was finally applied for simultaneously minimizing the main cutting force and surface roughness by providing a well-spread Pareto front of non-dominated solutions. The results indicated that the feed rate was the dominant parameter affecting both objectives, namely the main cutting force and surface roughness, while the NSGA-II algorithm was capable of delivering advantageous solutions for enhancing machinability with less than 10% error predictions when comparing simulated and actual machining results. Full article

Al₃BC, with its remarkably high modulus of elasticity (326 GPa) and hardness (14 GPa), coupled with a low density (2.83 g/cc), stands out as a promising reinforcement material for Al matrix composite. To study feasibility of solid-solid reaction (SSR) by forming an in situ Al₃BC reinforcing phase within the matrix, this study developed an Al₃BC/Al composite via mechanical alloying, followed by sintering at 1000 °C/1 h, and subsequent hot pressing at 400 °C/40 MPa. The reaction kinetics and corresponding electron microscopy images suggest that the aluminum (Al)-boron (B) reacts with graphene nanoplates (GNPs) to form both clusters and a heterogeneous multi-structured Al₃BC reinforcements network dispersed within the fine-grain (FG) Al matrix. The heterostructure contributes to a good balance between strength (~284 MPa) and ductility (~17%) and stiffness (~212 GPa). Superior strain hardening ability (n = 0.3515) endorses remarkable load-bearing capacity (σ_c = 1.63) and thereby promotes excellent strength-ductility synergy in the composite. The fracture morphology reveals that reasonable ductility primarily relies on the crack deflection by the FG-Al matrix, playing a critical role in delaying fracture. The potential importance of the matrix microstructure in the overall fracture resistance of the composite has been highlighted. Full article

This research study aims to evaluate the wear and corrosive behaviour of aluminum 6061 alloy hybrid metal matrix composites after reinforcing them with graphene (0.5, 1 wt.%) and boron carbide (6 wt.%) at varying weight percentages. The hybrid composites were processed through ball milling and powder compaction, followed by a microwave sintering process, and T6 temper heat treatment was carried out to improve the properties. The properties were evaluated and analyzed using FE-SEM, Pin-on-Disc tribometer, surface roughness, salt spray test, and electrochemical tests. The results were evaluated prior to and subsequent to the T6 heat-treatment conditions. The T6 tempered sample S1 (Al6061-0.5% Gr-6% B₄C) exhibits a wear rate of 0.00107 mm³/Nm at 10 N and 0.00127 mm³/Nm at 20 N for 0.5 m/s sliding velocity. When the sliding velocity is 1 m/s, the wear rate is 0.00137 mm³/Nm at 10 N and 0.00187 mm³/Nm at 20 N load conditions. From the Tafel polarization results, the as-fabricated (F) condition demonstrates an Ecorr of −0.789 and an Icorr of 3.592 µA/cm² and a corrosion rate of 0.039 mm/year. Transitioning to the T6 condition further decreases Icorr to 2.514 µA/cm², Ecorr value of −0.814, and the corrosion rate to 0.027 mm/year. The results show that an increase in the addition of graphene wt.% from 0.5 to 1 to the Al 6061 alloy matrix deteriorated the wear and corrosive properties of the hybrid matrix composites. Full article

This study investigates the influence of nano-sized reinforcements on aluminum matrix composites’ mechanical and tribological properties. Microstructural analysis revealed that introducing nanoparticles led to grain refinement, reducing the grain size from 129.7 μm to 41.3 μm with 2 wt.% TiO₂ addition. Furthermore, ultrasonic-assisted squeeze casting of AA6061 composites reinforced with TiO₂ and Al₂O₃ resulted in a 52% decrease in grain size, demonstrating nano-reinforcements’ effectiveness in refining the matrix structure. Despite these advantages, the high surface energy of nanoparticles causes agglomeration, which can undermine composite performance. However, ultrasonic-assisted stir casting reduced agglomeration by approximately 80% compared to conventional stir casting, and cold isostatic pressing improved dispersion uniformity by 27%. The incorporation of nano-reinforcements such as SiC, Al₂O₃, and TiC significantly enhanced the material properties, with hardness increasing by ~30% and ultimate tensile strength improving by ~80% compared to pure Al. The hardness of nano-reinforced composites substantially rose from 83 HV (pure Al) to 117 HV with 1.0 vol.% CNT reinforcement. Additionally, TiC-reinforced AA7075 composites improved hardness from 94.41 HB to 277.55 HB after 10 h of milling, indicating a nearly threefold increase. The wear resistance of Al-Si alloys was notably improved, with wear rates reduced by up to 52%, while the coefficient of friction decreased by 20–40% with the incorporation of graphene and CNT reinforcements. These findings highlight the potential of nano-reinforcements in significantly improving the mechanical and tribological performance of n-AMCs, making them suitable for high-performance applications in aerospace, automotive, and structural industries. Full article

Graphene nanoplatelets (GNPs) have significant potential as reinforcement agents in metallic materials. Understanding the interfacial structure between GNPs and an aluminum matrix (AlM) is crucial for this composite (GNPs/AlMC) design and application. Studies on the effects of heat treatment on the interfacial character and its influence on mechanical properties at the atomic scale are, therefore, of high importance. This study presents molecular dynamics simulations investigating the effects of heat treatment on the interfacial structural evolution between GNPs and AlM and how such behavior tunes mechanical performance. The results show that the number of interfacial bonds increases significantly when the heat treatment temperature reaches 900 K, below which it stays at low level. Compared with the heat treatment temperature, the pressure has less effect on the interfacial bonds of GNPs/AlMCs. Moreover, defective GNPs with pores at certain heat treatment temperatures promote the formation of Al-C bonds at the interface and improve the mechanical properties of GNPs/AlMCs. These findings underscore the potential for utilizing heat treatment and defect engineering to improve interfacial bonding and achieve improved mechanical performance in GNPs/AlMCs. Full article

Nanocarbon 2024 aluminum composites with 0.5 vol. % and 1 vol. % of graphene nanoplatelets and 1 vol. % and 2 vol. % of activated nanocarbon were manufactured through induction casting. The effect of the reinforcements and heat treatment on the performance of the composites was examined. Analysis of the microstructure of the composites before heat treatment suggested the homogeneous dispersion of reinforcements and the absence of secondary carbide or oxide phases. The presence of carbon nanoparticles had a significant impact on the microstructural characteristics of the matrix. This behavior was further enhanced after the heat treatment. The mechanical and damping properties were evaluated with the uniaxial compression test, micro Vickers hardness test, and dynamic mechanical analysis. The yield strength and ultimate strength were improved up to 28% (1 vol. % of graphene nanoplatelets) and 45% (0.5 vol. % of graphene nanoplatelets), respectively, compared to the as-cast 2024 aluminum. Similarly, compared to the heat-treated 2024 aluminum, the composites increased up to 56% (0.5 vol. % of graphene nanoplatelets) and 57% (0.5 vol. % of graphene nanoplatelets) in yield strength and ultimate strength, respectively. Likewise, the hardness of the samples was up to 33% (1 vol. % of graphene nanoplatelets) higher than that of the as-cast 2024 aluminum, and up to 31% (2 vol. % of activated nanocarbon) with respect to the heat-treated 2024 aluminum. The damping properties of the nanocarbon–aluminum composites were determined at variable temperatures and strain amplitudes. The results indicate that damping properties improved for the composites without heat treatment. As a result, it is demonstrated that using small volume fractions of nanocarbon allotropes enhanced the mechanical properties for both with- and without-heat treatment with a limited loss of plastic deformation before failure for the 2024 aluminum matrix. Full article

Graphene has been considered an ideal reinforcement in aluminum alloys with its high Young’s modulus and fracture strength, which greatly expands the application range of aluminum alloys. However, the dispersion of graphene and the interfacial reaction between graphene and the aluminum matrix limit its application due to elevated temperature. Friction stirring processing (FSP) is regarded as a promising technique to prepare metal matrix composites at lower temperatures. In this paper, FSP was used to prepare graphene-nanoplates-reinforced aluminum composites (GNPs/Al). The corresponding effects of the process parameters and graphene content on GNPs/Al were thoroughly studied. The results showed that plastic strain, heat input, and graphene content were the key influencing factors. Large degrees of plastic strain can enhance the dispersion of graphene by increasing the number of stirring passes and the ratio of stirring to welding velocity, thereby improving the strength of GNPs/Al. Low heat input restricts the plastic flow of graphene in the matrix, whereas excessive heat input can promote interfacial reactions and lead to the formation of a more brittle phase, Al₄C₃. This is primarily associated with the stirring velocity and welding velocity. High graphene content levels can improve the material strength by refining the grain size, improving the load transfer ability, and acting as a precipitate to prevent dislocation movement. These findings make a contribution to the development of advanced aluminum alloys with graphene reinforcement, offering broader application potential in industries. Full article

Aluminum alloy–graphene metal matrix composite is largely used for structural applications in the aerospace and space exploration sector. In this work, the preprocessed powder particles (AA 2014 and graphene) were used as a reinforcement material in a squeeze casting process. The powder mixture contained aluminum alloy powder 2014 with an average particle size of 25 μm and 0.5 wt% graphene nano powder (Grnp) with 10 nm (average) particle size. The powder mixture was mixed using the high-energy planetary ball milling (HEPBM) technique. The experimental results indicated that the novel mixture (AA 2014 and graphene powder) acted as a transporting agent of graphene particles, allowing them to disperse homogeneously in the stir pool in the final cast, resulting in the production of an isotropic composite material that could be considered for launch vehicle structural applications. Homogeneous dispersion of the graphene nanoparticles enhanced the interfacial bonding of 2014 matrix material, which resulted in particulate strengthening and the formation of a fine-grained microstructure in the casted composite plate. The mechanical properties of 0.5 wt% graphene-reinforced, hot-rolled composite plate was strengthened by the T6 condition. When compared to the values of unreinforced parent alloy, the ultimate tensile strength and the hardness value of the composite plate were found to be 420 MPa and 123 HRB, respectively. Full article

The distribution of reinforcements and interfacial bonding state with the metal matrix are crucial factors in achieving excellent comprehensive mechanical properties for aluminum (Al) matrix composites. Normally, after heat treatment, graphene nanosheets (GNSs)/Al composites experience a significant loss of strength. Here, better performance of GNS/Al was explored with a hybrid strategy by introducing 0.9 vol.% silicon carbide nanoparticles (SiCnp) into the composite. Pre-ball milling of Al powders and 0.9 vol.% SiCnp gained Al flakes that provided a large dispersion area for 3.0 vol.% GNS during the shift speed ball milling process, leading to uniformly dispersed GNS for both as-sintered and as-extruded (0.9 vol.% SiCnp + 3.0 vol.% GNS)/Al. High-temperature heat treatment at 600 °C for 60 min was performed on the as-extruded composite, giving rise to intragranular distribution of SiCnp due to recrystallization and grain growth of the Al matrix. Meanwhile, nanoscale Al₄C₃, which can act as an additional reinforcing nanoparticle, was generated because of an appropriate interfacial reaction between GNS and Al. The intragranular distribution of both nanoparticles improves the Al matrix continuity of composites and plays a key role in ensuring the plasticity of composites. As a result, the work hardening ability of the heat-treated hybrid (0.9 vol.% SiCnp + 3.0 vol.% GNS)/Al composite was well improved, and the tensile elongation increased by 42.7% with little loss of the strength. The present work provides a new strategy in achieving coordination on strength–plasticity of Al matrix composites. Full article

Enhancing the mechanical properties of conventional ceramic particles-reinforced aluminum (Al 1060) metal matrix composites (AMCs) with lower detrimental phases is difficult. In this research work, AMCs are reinforced with graphene nanosheet (GNS) and hybrid reinforcement (GNS combined with 20% SiC, synthesized by shift-speed ball milling (SSBM), and further fabricated by two-pass friction stir processing (FSP). The effect of GNS content and the addition of SiC on the microstructure and mechanical properties of AMCs are studied. The microstructure, elemental, and phase composition of the developed composite are examined using SEM, EDS, and XRD techniques, respectively. Mechanical properties such as hardness, wear, and tensile strength are analyzed. The experimental results show that the GNS and the SiC are fairly distributed in the Al matrix via SSBM, which is beneficial for the mechanical properties of the composites. The maximum tensile strength of the composites is approximately 171.3 MPa in AMCs reinforced by hybrid reinforcements. The tensile strength of the GNS/Al composites increases when the GNS content increases from 0 to 1%, but then reduces with the further increase in GNS content. The hardness increases by 2.3%, 24.9%, 28.9%, and 41.8% when the Al 1060 is reinforced with 0.5, 1, 2% GNS, and a hybrid of SiC and GNS, respectively. The SiC provides further enhancement of the hardness of AMCs reinforced by GNS. The coefficient of friction decreases by about 7%, 13%, and 17% with the reinforcement of 0.5, 1, and 2% GNS, respectively. Hybrid reinforcement has the lowest friction coefficient (0.41). The decreasing friction coefficient contributes to the self-lubrication of GNSs, the reduction in the contact area with the substrate, and the load-bearing ability of ceramic particles. According to this study, the strengthening mechanisms of the composites may be due to thermal mismatch, grain refinement, and Orowan looping. In summary, such hybrid reinforcements effectively improve the mechanical and tribological properties of the composites. Full article

6061 aluminum composites with 0.5 and 1 vol. % graphene nanoplatelets as well as 1 and 2 vol. % activated nanocarbon were manufactured by a powder metallurgy method. Scanning electron microscopy and Raman spectroscopy were used to study the morphology, structure, and distribution of nanocarbon reinforcements in the composite samples. Density Functional Theory (DFT) calculations were performed to understand the aluminum-carbon bonding and the effects of hybridized networks of carbon atoms on nanocarbon aluminum matrix composites. Scanning electron microscopy showed the good distribution and low agglomeration tendencies of nanoparticles in the composites. The formation of secondary phases at the materials interface was not detected in the hot-pressed composites. Raman spectroscopy showed structural changes in the reinforced composites after the manufacturing process. The results from Density Functional Theory calculations suggest that it is thermodynamically possible to form carbon rings in the aluminum matrix, which may be responsible for the improved mechanical strength. Our results also suggest that these carbon networks are graphene-like, which also agrees with the Raman spectroscopy data. Micro-Vickers hardness and compressive tests were used to determine the mechanical properties of the samples. Composites presented enhanced hardness, yield and ultimate strength compared to the 6061 aluminum alloy with no nanocarbon reinforcement. Ductility was also affected, as shown by the reduction in elongation and by the number of dimples in the fractured surfaces of the materials. Full article

The nanocomposites of 2024 Al reinforced with CeO₂@GNPs (graphene) nanoparticles were fabricated using the hot-press sintering method. With the addition of 0.5 wt% CeO₂@GNPs, the YS and UTS of the fabricated nanocomposites increased by 21.1% and 24.7%, respectively. The load transfer effect and optimization of the interfacial bonding were the main factors to improve the mechanical properties of the composites. The effect of the surface modification of GNPs on the corrosion resistance of the composites was investigated, demonstrating that the addition of GNPs weakened the corrosion resistance of the fabricated nanocomposites. Meanwhile, the corrosion current density (2.776 × 10⁻³ A·cm⁻²) and polarization resistance (13,971.37 Ω cm²) of the prepared composites with CeO₂ nanoparticle-layered GNPs exhibited a significant decreasing trend compared with the composites without a CeO₂ nanoparticle layer (3.540 × 10⁻³ A·cm⁻², 10,199.72 Ω cm²). Optimizing the dispersion of GNPs and their interfacial bonding with the aluminum matrix promoted the reduction in the corrosion area and the possibility of micro-couple formation, leading to an effective enhancement of the corrosion resistance of the nanocomposites. Full article

The high heat dissipation of high-power electronic equipment has become a major cause of damage, especially the central processing units (CPUs) of computers and other electronic devices. Accordingly, this research aims to improve the thermal conductivity as well as the mechanical properties of aluminum (Al) by mono and hybrid reinforcements of silver (Ag) and graphene (G) so that they can be used for heat dissipation. The structures of the prepared powders were investigated using the X-ray diffraction (XRD) technique. Furthermore, the sintered composites’ microstructure, density, thermal conductivity, mechanical properties, and electrical conductivity were investigated. The results showed that adding Ag percentages led to forming the Ag₂Al phase while adding graphene decreased the crystallite of the milled powder. The SEM results showed that the samples had high densification, which was slightly reduced with increasing percentages of reinforcements. Importantly, Al’s thermal conductivity and mechanical properties were significantly improved due to the addition of Ag and G reinforcements with a slight decrease in electrical conductivity. The highest thermal conductivity was observed a 278.86 W/mK in the sample containing 5 vol.% of Ag and 2.5 vol.% of G, which was improved by about 20.6%. In contrast, the highest microhardness and Young’s modulus were 39.19 HV and 71.67 GPa, which resulted in an improvement of about 30.7 and 17.8% for the sample containing 2.5 vol.% of Ag and 5 vol.% of G when compared to the Al matrix. Based on these promising findings, it is possible to infer that the objective of this study was effectively attained and that the created composites are appropriate for such applications. Full article

Graphene has become an ideal reinforcement for reinforced metal matrix composites due to its excellent mechanical properties. However, the theory of graphene reinforcement in graphene/aluminum matrix composites is not yet well developed. In this paper, the effect of different temperatures on the mechanical properties of the metal matrix is investigated using a classical molecular dynamics approach, and the effects of the configuration and distribution of graphene in the metal matrix on the mechanical properties of the composites are also described in detail. It is shown that in the case of a monolayer graphene-reinforced aluminum matrix, the simulated stretching process does not break the graphene as the strain increases, but rather, the graphene and the aluminum matrix have a shearing behavior, and thus, the graphene “pulls out" from the aluminum matrix. In the parallel stretching direction, the tensile stress tends to increase with the increase of the graphene area ratio. In the vertical stretching direction, the tensile stress tends to decrease as the percentage of graphene area increases. In the parallel stretching direction, the tensile stress of the system tends to decrease as the angle between graphene and the stretching direction increases. It is important to investigate the effect of a different graphene distribution in the aluminum matrix on the mechanical properties of the composites for the design of high-strength graphene/metal matrix composites. Full article