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Abstract: The possibility of using aluminum powder as transition metal catalyst carrier for CVD growth of carbon nanotubes (CNTs) has been investigated. The fabrication process of Ni/Al catalyst involved the production of binary colloid (Ni(OH)2/Al) by deposition–precipitation method, followed by calcination in N2 and reduction in H2. The nickel particles obtained were with uniform diameters. After the catalytic synthesis at 600°C a mass of well-graphitized multi-walled CNTs with the diameters in the 10–20nm range have been obtained, as evidenced by HRTEM. The operated catalytic particle encapsulated in CNT was nickel according to EDX analysis. However, when using pure nickel without aluminum as the catalyst, no CNTs have formed due to the agglomeration of Ni particles. Thus we speculated that the aluminum powder was responsible for the formation and the even dispersion of the nano-scale transition metal particles. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes (CNTs) with diverse structures (tubular and herringbone) reinforced Al matrix composites were fabricated by a combination of in situ growth process of CNTs in Al powders and powder metallurgy (PM) process. The enhancement efficiency of CNTs with different structures and the interfacial phenomenon between CNTs and Al matrix were investigated. The results showed that herringbone CNTs with more defects reacted with Al matrix slightly and a thin intermediate layer (Al4C3) of about 1–4nm was formed between herringbone CNTs and Al matrix. Nevertheless, the interface between tubular CNTs and Al matrix was close-knit and no obvious transition layer (new phase) was found. The mechanical performance of the composites indicated that the enhancement efficiency of herringbone CNTs in Al matrix composites was lower than that of tubular CNTs, due to the formation of the brittle intermediate layer of Al4C3, implying that tubular CNTs should be more suitable to reinforce Al matrix composite. [Copyright &y& Elsevier]

Abstract: A mass of carbon nanotubes with straight and short bodies was produced by chemical vapor deposition of methane over Ni/Al2O3. Scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis were used to analyze the synthesized carbon nanotubes. The results showed that they were well-graphitized multi-walled nanotubes and had not tangled together. Their average length was several hundreds of nanometers, suitable for their use as a nanometer-scale material. [Copyright &y& Elsevier]

Abstract: Changes in the thermogravimetrically determined oxidation behaviors of CVD-grown multi-walled carbon nanotubes (MWNTs) over Ni/Al catalyst with different Ni content were examined. Catalyst type was found to have a measurable impact upon nanotube stability, suggesting differing levels of crystalline perfection in the resulting nanotubes. With increasing the Ni content in the Ni/Al catalyst, the CNTs obtained became less stable during heat treatment in air. Furthermore, high-resolution transmission electron microscopy was employed to investigate the defect sites of as-grown MWNTs. The results provide evidence showing that defect sites along the walls and at the ends of the raw MWNTs facilitate the thermal oxidative destruction of the nanotubes. [Copyright &y& Elsevier]

Abstract: Straight carbon nanotubes, carbon onions and two kinds of herringbone carbon nanofibers have been synthesized over nickel supported on aluminum matrix by catalytic decomposition of methane. Nickel precipitated on the aluminum matrix was used as catalyst, which only had 5wt.% nickel. Through varying the production parameters such as the carrier gas, reaction temperature and reaction time, various morphologies of nanocarbons were obtained, which will be employed to reinforce aluminum matrix composites and thus the aluminum matrix composites obtained will have different potential applications. [Copyright &y& Elsevier]

For metal matrix composites (MMCs), the sintering temperature is of vital importance in realizing a dense bulk material with tight interfacial adhesion as well as limited structural damage to reinforcements. In this work, we investigated the influence of the spark plasma sintering (SPS) sintering temperature on the microstructure and mechanical properties of the in-situ synthesized discontinuous three-dimensional graphene-like network (3D GN) reinforced copper matrix composites. It demonstrates that with the rise of the sintering temperature from 600 °C to 700 °C, the GN distribution changes from intergranular type to intragranular type as a result of the significant improvement in interfacial wettability. Furthermore, the overall mechanical performance (both tensile strength and ductility) of the GN/Cu composites presents an unanticipated declining trend at elevated sintering temperatures. Integrated with microstructure characterization and the theoretical analysis, it is verified that the change of the reinforcement size and its distribution are the dominant factors. Their contributions to the mechanical properties of the composites were also studied in detail. [ABSTRACT FROM AUTHOR]

Abstract In this study, in situ synthesis of graphene nanosheets (GNS) coated nickel (Ni@GNS) as reinforcement for aluminum matrix composites (Ni@GNS/Al) was reported. Ni@GNS exhibits a quasi-continuous network-like structure. The addition of Ni could reduce the interfacial thermal expansion and improve the wettability between GNS and Al, resulting in a robust interfacial bonding among GNS, Ni and Al. Due to the unique structure, the composite exhibits a favorable strength-ductility synergy. The yield strength of the composite increases to 237 ± 2 MPa, ~ 80.9% improvement compared to that of the unreinforced Al, combined with an excellent elongation of 19.1 ± 2%. The main strengthening mechanisms are the interfacial thermal mismatch and Orowan dislocation strengthening, with some contributions of grain refinement, load transfer of GNS and precipitated-phase strengthening of Ni. Moreover, the interlocked effect between GNS and Ni could further prolong the deformation failure and improve the plasticity of the composites. [ABSTRACT FROM AUTHOR]

Abstract Traditional laminated metal matrix composites are confined to two-component system of pure metal matrix and its reinforcement. To achieve further improvement of the applied mechanical properties, in this work, the soft phase of laminated composites was enhanced by alloying with Cu. The synergistic effect of Cu on phases of both soft and hard including in-situ catalyzing and precipitation hardening was firstly explored. The laminated graphene nanosheets (GNSs) /AlCu composites of 2 vol% GNSs, were fabricated by ball milling and hot-rolling processes with much higher mechanical properties. The multi-pass hot rolling provided the solution-precipitation process of Cu transforming into Al 2 Cu and significantly increased the dislocation density of the original soft Al matrix. In addition, the fracture mechanism and fracture model of the laminated GNSs/AlCu composites were also investigated. [ABSTRACT FROM AUTHOR]

Abstract Nano-MgAl 2 O 4 particles and Mg x Al (1-x) B 2 whiskers co-reinforced Al matrix composites were prepared through powder metallurgy and hot working processes, involving ball-milling, cold pressing, sintering, repressing, and hot extrusion. The microstructure, tensile strength and hardness of the composites, the phase composition of the particles and the whiskers, and the interface between the whisker and the aluminum matrix were investigated systemically. The results show that during the hot extrusion, the reinforcements are uniformly distributed in the matrix, and the whiskers are arranged in the direction of extrusion. The whiskers are hexagonal prisms with close-packed hexagonal crystal structure and all the inner angles are 120°. Besides, the whisker elongates along the [0001] crystal orientation, and the six planes of the sidewalls belong to the {10 1 ¯ 0} family of crystal planes. As the content of reinforcement increases, the strength and hardness of the composites increase, while the elongation decreases. The composite contained 25.2 wt% reinforcements has a tensile strength of 400 MPa and a hardness of 124 HV. [ABSTRACT FROM AUTHOR]

In this paper, high strain rate dynamic compressive properties of the CNT/Al composite foams reinforced by in-situ grown carbon nanotubes (CNTs) have been investigated. The results show that the compressive strength and energy absorption capacity of the CNT/Al composite foams not only increase with the increment of CNT content but also increase with the strain rate increasing, revealing a typical strain rate sensitivity. For the 3.0 wt%-CNT/Al composite foams, the peak stress at 2130 s −1 is 52.5 MPa, which is ~ 86% higher than that at 0.001 s −1 (28.2 MPa). Besides, the deformation behavior of the pure Al foam can be significantly affected by the CNT addition and the strain rate. The different deformation behavior of the pure Al foam and composite foams is closely associated with the microstructure of pore walls. For the pure Al foam under the quasi-static condition, it can be recognised as firstly forms localized deformation bands, followed by the collapse of multi-layer deformation bands. While the failure of the CNT/Al composite foams mainly belongs to the shear deformation. In addition, as the strain rate increases from 0.001 to 800 s −1 , the deformation way of the pure Al foam transits from the local failure to layers of collapsing. Whereas, the CNT/Al composite foams still manifest as the formation of shear bands. Moreover, the pore fracture, collapsing and friction, as well as the crack propagation during the compressive processes are all beneficial to the energy absorption enhancement of the CNT/Al composite foams. [ABSTRACT FROM AUTHOR]

This work presents an in-situ chemical vapor deposition (CVD) method to synthesis carbon nanotube (CNT) on Al powders in a vertical tube furnace. The carbon nanotube reinforced Al matrix composites (CNT/Al composites) were fabricated by a new powder metallurgy (PM) approach associated with vacuum induction melting technique. It was shown that CNT was homogenously distributed in the Al matrix, and an interfacial transiting layer of Al 4 C 3 was formed between Al matrix and CNT in the bulk material. The tensile test showed that 1.5 vol% CNT/Al composites exhibited the largest tensile strength of 191 MPa as well as an excellent elongation of 32.6%. The strengthening efficiency of the 1.5 vol% CNT/Al composites improved by ~ 80% compared to the unreinforced pure Al. The strengthening mechanisms were mainly attributed to the load transfer of CNT, Al 4 C 3 and dislocation strengthening. The Al 4 C 3 transiting layer was beneficial to increase the interfacial shear strength and prolong the slide deformation of dislocation by forming an orientation relationship of Al 4 C 3 <001> // Al <111> and CNT (002) // Al 4 C 3 (001) according to the transmission electron microscope (TEM) observation. Besides, the thermocycling measurement enriched and deepened the understanding of the effect of Al 4 C 3 on improving the interfacial bonding, degrading the interfacial thermal mismatch between CNT and the Al matrix and increasing the compactness of the CNT/Al composites. [ABSTRACT FROM AUTHOR]

A novel approach is developed for the fabrication of nickel (Ni) matrix composites reinforced by graphene, which involves the synthesis of three-dimensional graphene networks (3D GNs) tightly anchored with Ni nanoparticles (3D Ni@GNs) by an in-situ high-temperature chemical vapor deposition process, subsequent uniform coating of Ni powders around the 3D Ni@GNs by an impregnation-reduction process, and final consolidation of the Ni@GNs/Ni composite powders by spark plasma sintering. Owing to the significant grain refinement and homogeneous dispersion of Ni@GNs in the composites identified through the electron backscattered diffraction, scanning and transmission electron microscopy, the composites exhibited much enhanced mechanical properties; the Ni@GNs/Ni composite with 1.0 vol% GNs was demonstrated a yield strength of 474 MPa and a tensile strength of 546 MPa, ~ 188.4% and ~ 26.0% higher than those of the pure bulk Ni respectively. It was thought that the composites were strengthened by both load transfer from the Ni matrix to the GNs and dispersion strengthening of GNs. Meanwhile, the addition of GNs greatly decreased the grain size of the Ni matrix, leading to a significant grain refinement strengthening for the Ni@GNs/Ni composites. [ABSTRACT FROM AUTHOR]

Graphene nanosheets (GNS) have attracted lots of attention as an ideal reinforcement in Al matrix composites. However, there are still challenges limiting the performance of the composites, such as the homogenous distribution of GNS in Al matrices, the structural integrity of GNS after ball-milling, and the interfacial bonding between GNS and Al matrices. This work presents a new approach to grow GNS on Al powders at 600 °C by in-situ chemical vapor deposition (CVD) process, using methane as the carbon source, and Cu as the catalyst. The GNS coated Cu reinforced Al matrix bulk composites (Cu@GNS/Al) from the composite powders was fabricated by powder metallurgy (PM) technique. It was found that Cu 2+ from CuCl 2 can easily anchor onto the surfaces of Al particles uniformly though a nanoscale-disperse-method in alcohol, enabling the homogenously dispersion of Cu particles in Al matrices after being reduced from Cu 2+ in hydrogen. With the assistance of Cu particles, network-liked GNS was successfully synthesized in-situ and strongly bonded with Al, resulting in a good mechanical performance of the composites. It is indicated that the tensile strength of the composites was improved by ~ 200% compared to the unreinforced pure Al. The strengthening mechanism was mainly ascribed to the load transfer of GNS, precipitation strengthening of Al 2 Cu compounds after 400 °C annealing and dislocation strengthening. [ABSTRACT FROM AUTHOR]

An aluminium matrix composite reinforced by in situ-generated gamma-Al 2 O 3 whiskers was fabricated from a simple Al-H 3 BO 3 system through cold pressing and sintering. The gamma-Al 2 O 3 whiskers with an average diameter of 20 nm and an aspect ratio of 10–15 were synthesized during the sintering process and homogeneously distributed in the Al matrix. As a result of the perfect lattice matching between gamma-Al 2 O 3 and the Al matrix, the gamma-Al 2 O 3 whisker is a desired reinforcement for the Al matrix, improving the ultimate tensile strength and hardness to 217 MPa and 43.5 HV, respectively, with a satisfactory ductility of 11%. Differential scanning calorimetry analysis shows that the growth of the whisker occurred at 550–650 °C, and the ball milling energy has a significant effect on whisker growth. [ABSTRACT FROM AUTHOR]

Graphene has attracted a lot of interest to be used as reinforcement in Aluminum matrix composites (AMCs) on account of its superior mechanical properties. However, the most serious and challenging issues in graphene-reinforced AMCs are that reinforcements are quite difficult to disperse uniformly in metal matrix and ensure intimate interfacial bonding simultaneously. In this work, an ultrafine Ni nanoparticles (NPs)-decorated graphene hybrid (indicated with Ni-NPs@GNP) was firstly synthesized by an in-situ chemical vapor deposition method to improve the wettability between metal and carbon nanophase, then the Ni-NPs@GNP/6061Al composite powders were obtained by dispersing the Ni-NPs@GNP into 6061Al alloy particles via a short time intermittent ball milling process. Finally, the Ni-NPs@GNP/6061Al bulk composites were fabricated through hot-pressing sintering of the composite powders. It was demonstrated that good dispersion of reinforcements was achieved in the Ni-NPs@GNP/6061Al composite coupled with remarkably enhanced interfacial bonding by introducing Ni NPs on the graphene, which resulted in the formation of Al 3 Ni intermetallic at the interface and thus improved the interfacial adhesion between 6061Al and graphene. As a result, the Ni-NPs@GNP/6061Al composite with 0.7 wt% reinforcement exhibited much enhanced mechanical properties, namely, a high yield strength of 140 MPa together with a tensile strength of 213 MPa can be achieved, which were 75% and 30% higher than that of the monolithic 6061Al, respectively. This work provides an inspiring strategy for fabricating 6061Al composites with adjustable mechanical properties as well as controllable interfacial bonding. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) reinforced Al composite foams were successfully fabricated by the combination of an in-situ chemical vapor deposition (CVD), short-time ball-milling and space-holder method. The CNTs are homogeneously dispersed and embedded in the Al foam matrix after 90 min ball-milling while maintaining the structural integrity. Both compressive properties and energy absorption capacity of the composite foams increase with the increment of CNT content but decrease with the temperature rising between 25 and 250 °C. The compressive yield strength and the plateau stress of 3.0 wt%-CNT/Al composite foams maintain 16.8 and 20.2 MPa at 150 °C, respectively, which are much higher than the corresponding yield stress (5.7 MPa) and plateau stress (8.6 MPa) of the pure Al foam. Especially, the energy absorption capacity of the 3.0 wt%-CNT/Al composite foams reaches 19.8 MJ/m 3 at 150 °C, which is ~2.5 times higher than that of pure Al foam. Fracture analysis shows that the failure mode of the Al foam changes from ductile type to brittle type combined with ductile type, as a result of the CNT addition in the matrix. [ABSTRACT FROM AUTHOR]

A systematic study on heterogeneous nucleation, microstructure and mechanical properties of A357-0.033Sr alloys with different Ti/Sc atom ratio was carried out. According to the obtained results, a Ti/Sc atom ratio up to 1:1 did not show much change in the heterogeneous nuclei but at a higher atom ratio level, heterogeneous nuclei have a great change in chemical composition and morphology (from strip Ti-rich phase to the particle-like Ti-rich phase). In addition, compared to the other four alloys studied, the A357-0.033Sr-0.30Sc-0.35Ti alloy with 1:1 atom ratio has the smallest grain size (88 µm), optimum microstructure (morphology, size and distribution of eutectic Si), densest core-shell Al 3 (Sc, Ti), all of which result in the best mechanical properties. Its tensile strength and elongation reach 287 MPa and 3.62% respectively, showing about 11% and 84% increases compared with A357-0.033Sr alloy. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) reinforced Al matrix composites were produced by a modified powder metallurgy route, including in-situ synthesis of CNTs on Al powders by chemical vapor deposition and subsequent ball-milling process. The influence of CNT content (0–4.5 wt%) on the microstructure, mechanical and coefficient of thermal expansion (CTE) performance of CNT/Al composites was systematicly investigated. During the fabrication process, well dispersed CNTs with integrated structure are deeply embedded in Al matrix to form an effective interface bonding. The hardness and tensile strength of CNT/Al composites monotonically increase with the increment of CNT content. The 4.5 wt%-CNT/Al composites exhibit largest hardness and tensile strength, which is 2.3 and 2.4 times higher than that of starting Al, respectively. The CTEs of the composites decrease with the increase of CNT content at the temperature range of 100–300 °C. The CTE of the 4.5 wt%-CNT/Al composites reduces as much as 17% compared with that of starting Al at 100 °C. Thus, we offer a large variety of mechanical and CTE properties which depend on the CNT content in CNT/Al composites, all of them might be good alternatives depending on the application purpose. [ABSTRACT FROM AUTHOR]

Al composite foams reinforced by in-situ generated MgAl 2 O 4 spinel whiskers were fabricated via sintering and dissolution processes, using sodium chloride particles as a space holder material. The MgAl 2 O 4 spinel whiskers with diameters ranging from 50 to 300 nm were uniformly distributed in the composite foams and formed well-bonded interface with the Al matrix. The mean pore sizes and the average thickness of the cell wall are about 450 μm and 20 μm, respectively, while the relative density is 0.3. Compressive tests verified that the plateau stress is in the range of 5.4–18.7 MPa at the pore size of 0.45 mm, while the relative density increases from 0.2 to 0.5. Especially, the composite foams showed superior plateau stress (18.7 MPa) and energy absorption capacity (17.5 MJ/m 3 ) by adding 10 wt% Mg powder in starting materials. [ABSTRACT FROM AUTHOR]

In-situ synthesized carbon nanotubes (CNTs) reinforced aluminum–copper (Al–Cu) composites have been prepared by powder metallurgy. The strengthening effect of CNTs reinforcement and precipitation hardening of Al–Cu matrix has been investigated. CNTs and Cu nanoparticles are homogeneously embedded into Al powders through the process of in-situ preparation and ball milling. XRD results show that Cu elemental phase is converted to Al 2 Cu phase during the procedure of sintering. Raman spectra indicate that CNTs could maintain its structural integrity during powder metallurgy. In T6 heat treatment, the aging time of peak hardness has been reduced from 9 h to 3 h, demonstrating accelerated aging of the composite. Besides, the ultimate tensile strength of CNTs/Al–Cu composites have a 33.9% increase compared with that of Al–Cu alloy, and a further increase could be achieved (20.3%) after T6 heat treatment. The strengthening mechanism of CNTs/Al–Cu composites combines two synergistic factors: CNTs reinforcement and precipitation hardening of Al–Cu alloy. [ABSTRACT FROM AUTHOR]

In-situ generated MgAl 2 O 4 nanowhiskers, with diameters ranging from 30 to 200 nm, reinforced 6061 aluminum alloy composites have been successfully synthesized by reaction hot pressing under a relatively low temperature (600 °C). The effects of temperature and pressure on the morphology of MgAl 2 O 4 whiskers, as well as microstructure, densification and mechanical properties of the composites were investigated in detail. The results indicate that the MgAl 2 O 4 nanowhiskers with aspect ratio about 10–50 are uniformly distributed and firmly bonded with the matrix. Most of the nanowhiskers acting as bridges penetrate into the Al particles to form a framework bearing and transferring extrinsic loads. The high-resolution transmission electron microscope observation reveals that the MgAl 2 O 4 /Al interface is clean, smooth and free from interfacial product, and the whiskers have well-bonded interfaces with matrix. Additionally, the composites, prepared by sintering at 600 °C under the pressure of 50 MPa, exhibit the optimal performance. [ABSTRACT FROM AUTHOR]

The rare earth scandium (Sc) as a microalloying element has attracted an increasing interest in aluminum alloys for achieving excellent mechanical properties. Combining with zirconium, high strength and low price Al–Sc alloys are expected. The effects of Sc and Zr on the grain refinement, recrystallization resistance and precipitation hardening were investigated in new type of Al–Zn–Mg–Sc–Zr alloys by rolling, annealing and aging processes. Scandium addition into the Al–Zn–Mg alloys can efficiently refine the grain size and increase recrystallization resistance, especially together with zirconium addition. The maximum value of the yield-to-tensile strength (627 MPa/667 MPa) was obtained with 0.2Sc/0.4Zr ratio of the alloy after solution-aging treatment. The additional strengthening of the alloys is attributed to the grain refinement and the precipitation-strengthening effect of Al 3 Sc, Al 3 Zr or Al 3 (Sc, Zr) in the proper ratio of Sc/Zr during aging. [ABSTRACT FROM AUTHOR]

6061 aluminum-alloy matrix composites are drawing greater attention due to their low density, excellent mechanical properties and wear resistance. In this study, in-situ generated MgAl2O4 spinel whiskers reinforced 6061Al alloy matrix composites were fabricated and solutionizing and age hardening treatment was performed on the composites in a temperature range of 160–210°C. The microstructure and mechanical properties of the composite were investigated and the influences of in-situ generated whiskers on aging behaviors of the composite were also discussed. The results show that the whiskers exhibit a homogeneous distribution with good interface bonding with the matrix. The hardness and ultimate tensile strength (UTS) increase with increasing content of the whisker, whereas the ductility decreases at the same time. The properties of the composites attained a peak value of 195 HV in hardness and 400MPa in UTS after aging for 30min at 190°C. Compared with the 6061Al alloy, the presence of whiskers could accelerate the aging kinetics of composites due to the high density dislocations formed during the fabrication process. [ABSTRACT FROM AUTHOR]

For ceramic reinforced metal matrix composites, it is a critical issue to improve the limited ductility to achieve a combination of high strength and high toughness. Herein, in-situ synthesized MgAlB 4 whisker reinforced Al (MgAlB 4 w/Al) composites with rational distribution of the reinforcement were successfully prepared by an efficient process combining vacuum pressureless sintering and hot-extrusion. The results demonstrate that the MgAlB 4 whiskers noticeably coarsen with increasing sintering temperature, while the sintering duration has little effect on the size of the whiskers. The as-extruded composite with 15 wt% MgAlB 4 w has excellent comprehensive properties with the ultimate tensile strength of 380 MPa and the fracture elongation of ~9.6%. Fracture analysis reveals that the whiskers bear most loads and fracture firstly to form crack sources with the load increasing during drawing. In addition, the alignment distribution of MgAlB 4 w along extrusion direction is the main reason for the improved ductility of the MgAlB 4 w/Al composite. • Synchronously improving the tensile strength and ductility of MgAlB4w/Al composites. • In-situ XRD was used to characterize the growth of the MgAlB4 whiskers in Al matrix. • MgAlB 4 w distributes along the extrusion direction after hot extrusion. [ABSTRACT FROM AUTHOR]

For nanocarbon reinforced aluminum matrix composites (AMCs), the architecture design of reinforcements is an effective route to obtain superior mechanical performances. In this work, a novel AMC reinforced by CNTs wrapped with γ-Al 2 O 3 (CNTs@Al 2 O 3) reinforcement with balanced strength and toughness was fabricated by powder metallurgy methods. The wrapping structure of γ-Al 2 O 3 was synthesized through the in-situ reactions of Al matrix and boric acid decorated CNTs, thus improving the interface coupling of the composite. The CNTs@Al 2 O 3 /Al composite with the addition of 0.5 wt% CNTs and 10 wt% in-situ Al 2 O 3 exhibited a mean ultimate tensile strength of 404 MPa, which is significantly higher than unreinforced pure Al (183 MPa) and those reinforced by individual CNTs (207 MPa) or Al 2 O 3 (289 MPa). An improvement of ductility was also achieved in CNTs@Al 2 O 3 /Al composites compared with the Al 2 O 3 /Al composites with the same Al 2 O 3 content. The synergistic strengthening and toughening effects are ascribed to the ingenious in-situ CNTs@Al 2 O 3 wrapped structure, which highlights the importance of architecture design of reinforcements in AMCs, and sheds new light on the development of CNT-reinforced AMCs. Image 1 • A CNTs wrapped with in-situ γ-Al 2 O 3 reinforcement structure (CNTs@Al 2 O 3) was achieved. • Synergistic strengthening effect between CNTs and Al 2 O 3 was attributed to the unique wrapped structure. • The enhanced interfacial coupling improves load-transfer capability and hinders crack propagation. • The superior mechanical performance with balanced strength-toughness was obtained. [ABSTRACT FROM AUTHOR]

Poor mechanical interfacial bonding between graphene nanoplatelets (GNPs) and Cu is unfavorable to the comprehensive properties of the GNPs/Cu composites. Molybdenum carbide coating graphene nanoplatelets (Mo 2 C@GNPs) were prepared by impregnation reduction combined with in situ reaction to improve the interfacial bonding of Cu matrix composites. Compared with GNPs/Cu composites, Mo 2 C@GNPs/Cu composites exhibit excellent mechanical properties. It is due to the fact that Mo 2 C not only improves the interface bonding between the GNPs and Cu matrix, but also increases the strength of composites by dislocation strengthening as nanoparticle reinforcing phase. In addition, the conductivity of Mo 2 C@GNPs/Cu composites is higher than that of GNPs/Cu composites due to the improved interfacial bonding. This work sheds light on adding carbides to control the properties of GNPs/Cu composites. [ABSTRACT FROM AUTHOR]

Developing metallic materials with heterogenous nanostructures is one of the most promising strategies for obtaining excellent integrated mechanical properties towards structural applications. To explore the possibility of realizing intentional structural heterogeneities in graphene/metal composites, herein, we demonstrate a novel copper composite reinforced by three-dimensional network-like graphene powders, achieved by hot-pressing, cryo-rolling and low-temperature annealing. It was found that the structure of three-dimensional graphene could be well remained during the processing and thereby resulted in an alternated distribution of lath-like graphene-rich zones and graphene-free zones in the composites. The yield strength (380 ±5 MPa) and tensile strength (412 ± 7 MPa) of 1.5 vol % graphene/copper composite were 74% and 30% higher than that of pure Cu, respectively. Moreover, the ultimate tensile strength and fracture elongation of graphene/copper composite with heterogenous graphene distribution both exceeded those of a composite reinforced by homogeneously-distributed two-dimensional reduced graphene oxide nanosheets. The dominant strengthening mechanisms were verified as the Hall-Patch strengthening thanks to the highly refined matrix grain size of sub-micron level and the load transfer strengthening originated from the formation of 'graphene-rich zones' in the copper matrix. This study highlights the importance of architecture design in graphene reinforced metal matrix composites for actualizing their strengthening potential while retaining a balanced ductility. Image 1 [ABSTRACT FROM AUTHOR]