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Aluminum matrix composites (AMCs) reinforced with intragranular nano-sized Al2O3 were used as model material to investigate the effects of intragranular nano reinforcement on the mechanical properties at macro- and meso- levels. The results revealed that intragranular Al2O3 effectively facilitates the dislocation multiplication, which in turn enables the grain interior to endure high levels of plastic strain and consequently alleviates stress concentration at the grain boundary. Furthermore, intragranular Al2O3 leads to a collective enhancement in the intrinsic mechanical properties across domains of varying sizes, thereby contributing to the coordinated plastic deformation of heterogeneous grains, and enhancing the creep resistance of composite. [ABSTRACT FROM AUTHOR]

The microstructure design of graphene based reinforcement is an effective route to obtain graphene/aluminum composites with good mechanical properties. In this study, alumina anchored on graphene nanosheets hybrid (Al2O3@GNS) was in situ synthesized by a sodium chloride template-assisted high-temperature calcination strategy. Al2O3@GNS was used as a reinforcement to fabricate aluminum matrix composites (Al2O3@GNS/Al) by flake powder metallurgy (FPM) route. It was found that Al2O3@GNS was homogenously distributed and a relatively obvious synergistic strengthening effect was acquired by employing Al2O3@GNS as reinforcement of the composites. ∼1.0 vol%-Al2O3@GNS/Al composite obtained the maximum tensile strength of 359 MPa, an ∼131.6% improvement superior to pure Al. The strengthening efficiency of Al2O3@GNS is higher than those reinforced by individual GNS, Al2O3 or its simple mixture. An elongation of 11.2% was achieved in the ∼ 1.0 vol%-Al2O3@GNS/Al composite, exhibiting a favorable strength-ductility synergy. The synergistic strengthening effect was attributed to the formation of an interlocked network of Al2O3@GNS, which was beneficial to improve the load transfer efficiency from the matrix to reinforcement in the composites. [ABSTRACT FROM AUTHOR]

As one of the most efficient trace element to improve the mechanical properties of alloys, scandium (Sc) has attracted much attention for aluminum alloys in recent years. In this study, a new kind of Al–Zn–Mg–Cu–Sc–Zr alloy has been designed, and the evolution of microstructure and properties during the processes including homogenization, hot extrusion, solid solution and aging has been investigated. The alloy aged at 120 °C reveals a dual-peak aging phenomenon which is attributed to the overlap of the formation of Guinier–Preston (GP) zones and η′ phases. Consequently, excellent mechanical properties can be obtained (UTS = 747 MPa, YS = 721 MPa and EI = 10.9%) when the alloy is aged at 120 °C for 15 h. The improvement of the mechanical performance is mainly attributed to the grain refinement by the primary Al 3 (Sc, Zr) and the dispersion strengthening of the secondary Al 3 (Sc, Zr). Thus, the combined additions of Sc and Zr play an important role for the strengthening of the alloy. [ABSTRACT FROM AUTHOR]

Al–Mg-oxides composite system exhibits great potential for achieving aluminum matrix composites (AMCs) with exceptional mechanical properties. However, the effects of Mg element on in-situ reaction mechanism and precipitation behavior remains largely unknown. In this work, Al–Mg–ZnO composite was successfully fabricated by using segmented ball milling, reaction sintering and heat treatment, resulting in an ultimate tensile strength of ∼760 MPa and fracture elongation of ∼3.5 %. The Mg content-dependent reaction pathway and precipitation evolution were systematically investigated through thermodynamic analysis and microstructural characterization. The results revealed that the relatively high Mg content promotes the in-situ generation of the hybrid reinforcements composed of MgAl 2 O 4 and MgO. Additionally, the semi-coherent reinforcement-matrix interface facilitates interfacial precipitation by reducing the energy barrier for nucleation. Consequently, solute-rich/vacancy-rich Guinier-Preston (GP) zones are activated to form η′ and T′ precipitates. These high-density nano-sized secondary phases contribute to the considerable strengthening effect of the composite. The present work provides valuable theoretical insight into the effect of Mg content on the microstructure evolution of Al–Mg–ZnO composite system, which offers promising avenues for achieving AMCs with superior mechanical properties. • Al–Mg–ZnO composites were in-situ synthesized using segment ball-milling (SBM) combined with reaction sintering. • Mg content dependence of the in-situ reaction path was systematically investigated by microstructural characterization. • Changes in Mg content cause competition in precipitation mechanisms of the different kinds of Guinier-Preston (GP) zones. • Reinforcement-Al interface and secondary phases account for the exceptional mechanical properties of the Al–Mg–ZnO composite. [ABSTRACT FROM AUTHOR]

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]

The robust interface adhesion between matrix and reinforcement is the guarantee for enhancing mechanical performance of the metal matrix composites (MMCs). Unfortunately, the low strengthening efficiency and drastically reduced elongation have always been the cases for MMCs due to the difficulties for architecting tightly-bonded and effective interface structure. Herein, a new strategy is proposed to construct interfacial interlocking structure in the Al matrix composites reinforced by graphene nanosheets (GNS) decorated with Ni nanoparticles (Ni NPs@GNS), which were in-situ synthesized by using assembled NaCl particles as templates. The hybrid particle of Al 3 Ni and Ni serves as an interface interlocking factor to fasten the bonding of Al and GNS, thus the outstanding load transfer and dislocation accumulation capability are adequately achieved at the interfaces. Besides, experiments and first-principles calculations disclosed that the robust covalent bonding between Ni NPs and GNS with few defects and lower oxygen level synthesized in this work facilitates a tortuous crack propagation path before fracture. Hence, the as-obtained composites exhibited an excellent strengthening efficiency while preserving a good ductility. It is evidenced that the construction of interfacial interlocking structure can pave a promising path to produce strong, tough and lightweight MMCs for wide applications. [Display omitted] [ABSTRACT FROM AUTHOR]

As a kind of ternary diboride ceramic phase, MgAlB 4 can grow into whiskers via in situ reaction in aluminum matrix, which effectively solves the reinforcement dispersion and interface bonding problems in the preparation of the whiskers reinforced aluminum matrix composites. Herein, electronic structures and mechanical properties of the ternary diboride ceramic and its binary analogues (AlB 2 and MgB 2) are comparatively investigated via first-principles calculations. The calculation results show that the Al–B bond in MgAlB 4 is stronger than that in AlB 2 , while the Mg–B bond is weaker than that in MgB 2. The bulk modulus, shear modulus and Young's modulus of the polycrystalline materials follow the order: AlB 2 > MgAlB 4 > MgB 2. The tensile strength in [ 21 3 ‾ 0 ] direction is greater than that in [ 0001 ] direction. AlB 2 has the maximum tensile strength in both directions. The tensile strength of MgAlB 4 in [ 21 3 ‾ 0 ] direction is greater than that of MgB 2 , but in [ 0001 ] direction the trend is opposite. The abrupt change of the atomic spacing caused by the difference of bond strength is the fundamental reason for the difference of tensile strength among the borides. [ABSTRACT FROM AUTHOR]

The difficulty of dispersing high content of graphene nanoplatelets (GNPs) in the metal matrix limits the strengthening efficiency of GNPs reinforcement. Herein, high content GNPs were synthesized on the surface of Cu powders using chemical vapor deposition with solid carbon source incorporating impregnation-reduction route, which made GNPs uniformly dispersed and improved the interfacial bonding between GNPs and Cu matrix. Then, the composites were densified by vacuum hot pressed sintering followed by multi-step hot rolling process, during which the orientation distribution of GNPs was achieved. After a rolling reduction of 70%, the composite materials containing 12 vol% GNPs were increased by 44% in yield strength (256 MPa) compared with that of pure Cu (178 MPa). Furthermore, the in-plane thermal conductivity was increased by 17% (441 W/mK) when the GNPs content is 15 vol%. This work sheds light on designing structural and functional integrated Cu matrix composites. Unlabelled Image • High content graphene nanoplatelets reinforced Cu matrix composites were fabricated. • The graphene nanoplatelets are uniformly dispersed and oriented. • The composites have high thermal conductivity and good mechanical properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • The configurations of bilayer graphene reinforced Cu composites is considered. • The effects of C vacancies on the composites interfacial bonding were studied. • The graphene-copper hybrid could improve the mechanical properties of composites. • The tensile properties and slipping mechanism of the interface were investigated. Graphene/Cu composites have shown great potential in the fields of mechanical engineering, electronic devices and so on. In this study, the impacts of vacancies on the interlayer interaction of bilayer graphene (BLG) and the resultant influence of graphene interlayer bonding on the interfacial bonding, tensile strength, and slipping mechanism of the graphene/Cu composites are comprehensively investigated based on first-principles calculations. It was revealed that clustering of cross-layer vacancies (CV) can initiate the formation of distinct hybrid types (sp 2 hybrid, sp 3 hybrid) of interlayer bonds, resulting in enhanced interlayer bonding of BLG. Unlike the van der Waals interaction between graphene and Cu, vacancies cause the Cu atoms on the surfaces to be embedded in the BLG, forming the graphene-copper hybrid that can improve the combination of Cu and graphene. The notable hybridization between the 2 p orbitals of the unsaturated C atoms neighboring the vacancies and the 4 s , 3 d orbitals of the Cu atoms on the surfaces drives this effect. BLG with interlayer bonds can substantially improve the interfacial bonding and mechanical properties of the composites. This research provides a novel outlook for the interface engineering research and innovative development of graphene/Cu composites by regulating the interlayer bonding of grapheme. [ABSTRACT FROM AUTHOR]

As a promising architecture reinforcement, the three-dimensional (3D) configuration of nanocarbon holds great prospects in achieving a strength-ductility combination for metal matrix composite (MMCs). However, due to the native deficiency of Al in catalyzing the growth of nanocarbon, constructing a nanocarbon network has been the long-term challenge for Al matrix composites (AMCs). Herein, we develop a new strategy for synthesizing AMCs reinforced by three-dimensional nanocarbon (3D-C) via plasma-enhanced chemical vapor deposition (PECVD) integrated with hot pressing (HP) as well as hot extrusion, demonstrating exceptional mechanical properties. The detailed characterization reveals that the in-situ generation of nanocarbon layers on the surface of Al powders is attributed to the initiation of isolated carbon islands, followed by merging and self-assembly, which is governed by the PECVD-assisted catalysis growth-regime. The subsequent welding of nanocarbon layers during the HP promotes the formation of interlocking 3D-C networks in Al matrix, enhancing the sintered densification of the composite. Such unique nanocarbon distribution configuration not only effectively constrains the coarsening and deformation of Al grains, but also notably accumulates dislocation under high stress conditions. Moreover, 3D-C with a strong interfacial bonding contributes to the toughness through the microcracks, bridging cracks as well deflecting cracks, which accounts for the high toughness of the composite. This work provides new insights into the 3D distribution configuration of reinforcements in AMCs to achieve the optimized mechanical performance of composites. • Three-dimensional nanocarbon network in Al matrix was successfully synthesized. • 3D-C network constrains grain deformation and facilitates dislocation accumulation. • High-coherent 'C-Al 2 O 3 -Al' interface contributes to strength-ductility combination. [ABSTRACT FROM AUTHOR]

Easy agglomeration and poor interface are bottlenecks restricting the effective transfer of internal stress in ceramic nanoparticle-reinforced metal matrix composites (MMCs). In this study, nanosized MgO particles coated by in-situ few-layered graphene (MgO@FLG) were synthesized using methane as carbon source by chemical vapor deposition (CVD) method, then incorporated with Al matrix through powder metallurgy routes. It is demonstrated that MgO@FLG particles in composites were endowed with more significant strengthening contributions in comparison with the counterparts without coating. This is critically attributed to the interlayer van der Waals of FLG promoting the particle dispersion, and the chemical interface, which involves Mg-O-C bonding and moderate Al 4 C 3 nanorods, improving the interfacial bonding. The thermal expansion behaviors and coefficient of thermal expansion (CTE) of composites were investigated by testing thermal cycling ranging from 50 to 400 °C. The hysteresis residual strain of MgO@FLG/Al composites is less than that of MgO/Al composites, indicating a robust interface adhesion to adapt to the changing of internal stress. Furthermore, a low experimental CTE value was obtained for the MgO@FLG/Al composite, and its theoretical CTE value falls into a possible prediction region of Kerner's model. This work provides new insights into the reinforcement modification and interface design of particle-reinforced MMCs, facing the application of structural components with the improved thermal stability and high load-bearing capacity. [Display omitted] • A novel strategy is developed to fabricate Al matrix composites reinforced by MgO particles with in-situ few-layered graphene (FLG) coating. • The FLG coating promotes MgO particles finely dispersing and forming robust interfacial bonding with Al matrix. • MgO particles with FLG coating endow the composites with a well-balanced strength and ductility. • A tight interface cohesion bridged by in-situ FLG coating is responsible for a low thermal expansion property of composites. [ABSTRACT FROM AUTHOR]

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]

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]

In this work, Cu matrix composites reinforced with rutile-TiO 2 nanoparticles were fabricated by a facile in-situ method, which involved the in-situ synthesis of TiO 2 -Cu composite powders by molecular-level mixing process and subsequent vacuum hot-pressing sintering of the as-obtained composite powders, leading to dense bulk composites with homogeneously distributed TiO 2 nanoparticles. The influences of in-situ route on the microstructures, TiO 2 distribution and mechanical properties of the composites were investigated. The results showed that the composite with 1.72 vol% TiO 2 not only exhibited a high yield strength of 290 MPa which is about 1.6 times larger than that of pure Cu (110 MPa), but also possessed a high fracture elongation of 32% and an outstanding electrical conductivity of 97% IACS, indicating the as-obtained TiO 2 /Cu composites possessing well-balanced mechanical properties and electron conductivity. Moreover, the strengthening mechanism of TiO 2 nanoparticles for the Cu matrix composites was analyzed based on the experimental results. [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]

The interface doping with rare earth elements is a novel strategy to enhance the weak interface bonding of copper-graphene system (Cu-G). In this work, taking Sc, Y, La as representatives, we investigated the structural, electronic and mechanical properties of clean and doped Cu-G systems using first principles calculations. By the comparison of interface spacing and work of separation with clean system, the significantly improved interface interaction in rare earth elements doped systems has been verified. Besides, difference charge density, Bader charge and density of states were employed to reveal the microscopic modifying mechanism on the atomic scale. Then, the tensile stress-strain curves were obtained using a fitting function related with the element electronegativity, and thus the quantitative relationship between the interface bonding and mechanical properties was determined, which could provide theoretical guidance for the interface modification of Cu-G composites through doping rare earth elements. The introduction of rare earth elements could significantly enhance the interface bonding of copper-graphene system by promoting charge transfer and electron interaction at the interface, which could be demonstrated by the analysis of electronic properties. Then, the rigid stretching was implemented, and a fitting function containing electronegativity was employed to determine the quantitative relationship between interface bonding and tensile properties. [Display omitted] • Rare earth elements doping effects on copper-graphene system are studied. • The structural and electronic characteristic of doped systems are analyzed. • The rigid stretching is used to study the related mechanical properties. • Quantitative relationship between interface binding and mechanical property is explored. [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]

• Al matrix composite reinforced by uniformly dispersed MgAl 2 O 4 particles was successfully synthesized via shift-speed ball-milling (SSBM) combined with reactive sintering. • The produced MgO as a precursor participates the formation of homogeneously dispersed MgAl 2 O 4 that forms robust interfacial bonding with matrix. • Submicron MgAl 2 O 4 particles remarkably contributes to the strength of composite via the coefficient of thermal expansion (CTE) mismatch strengthening and grain refinement. In-situ synthesized Al matrix composites (AMCs) have drawn lots of interest recently relying on the designability of reinforcement configurations and promising mechanical properties. In this work, a new generation of AMCs reinforced by in-situ MgAl 2 O 4 particles was fabricated based on Al-Mg-ZnO system using shift-speed ball-milling (SSBM) combined with reactive sintering method. The detailed microstructural characterization and comprehensive thermodynamic analysis rationalized the in-situ reaction mechanism, in which the substituted MgO was involved in the formation of homogeneously dispersed MgAl 2 O 4 that forms robust interfacial bonding with matrix. In addition, the coefficient of thermal expansion mismatch strengthening and grain refinement acted in concert to render the impressive mechanical properties, achieving the yield stress of 347 MPa and ultimate tensile stress of 505 MPa. This work can be informative for the fabrication of high-performance in-situ MgAl 2 O 4 reinforced AMCs based on Al-Mg-oxides system. [ABSTRACT FROM AUTHOR]

The interface bonding was found to be related with the element electronegativity. And the first-principles tensile experiments including the rigid stretching and the relaxed stretching were implemented to simulate the stretching process, then a fitting function was applied to determine the quantitative relationship between the interface bonding and mechanical properties. [Display omitted] • Transition metal (TM) elements doping effects on Gr/Cu interface binding are studied. • Work of separation of the doped interfaces relates to the TM electronegativity. • The rigid and relaxed stretching are used to study the related mechanical properties. • Quantitative relationship between interface binding and mechanical property is explored. The interface doping with transition metal elements (TM = Ti, Cr, Co, Ni) has been experimentally proved to be an effective pathway to improve the weak interface bonding of graphene/copper (Gr/Cu) composites. In this paper, the microscopic influencing mechanism of TM doping on the interface interaction and mechanical properties of Gr/Cu was investigated by the first-principles calculations. The sandwich model with graphene embedded in Cu matrix was adopted here to simulate the TM-doped interfaces. It is revealed that the introduction of TM doping elements can significantly improve the work of separation, which relates to the electronegativity difference between TM and Cu elements based on the analysis of the interface electronic structure. Then, the mechanical properties of the clean and TM-doped interfaces were studied by the rigid stretching and the relaxed stretching. We found that, in rigid case, the theoretical tensile strengths of different interfaces are positively correlated with the work of separation, and the electronegativity is also a main factor affecting the mechanical properties. Furthermore, a fitting function containing the element electronegativity was applied to get the stress–strain relationship curve, and the quantitative relationship between the interface bonding and mechanical properties determined in this work can be served as a favorable support for the experimental design of Gr/Cu composites. [ABSTRACT FROM AUTHOR]

Simultaneously achieving high strength and ductility is a critical issue for graphene reinforced aluminum matrix composites, which couldn't be resolved by the conventional mechanical milling-powder metallurgy technology due to the following reasons. On one hand, the low addition of graphene in the matrix traceable to its poor dispersibility limits the further strength improvement. On the other hand, the introduced graphene tends to distribute into grain boundaries rather than inside grains, which would result in stress concentrations at grain boundaries and localized strains, leading to the poor ductility of graphene/Al composites. In this work, intragranular nano-sized graphene nanoplates with high-content were dispersed in the matrix uniformly by a modified ball milling strategy, which induces that the strength and uniform elongation of the composites were simultaneously enhanced due to the improved work hardenability. Furthermore, the strengthening and toughening mechanisms were also discussed. This work offers a new insight into the fabrication and design of graphene/Al composites with both high strength and ductility. [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]

From the analysis of interfacial microstructure and electron distribution to reveal the novel strengthening mechanism which affects the tensile properties of metal matrix composites. • It found that tensile properties have no direct connection with the work of adhesion or the interface energy. • The tensile properties were affected by the uniformity of charge density distribution. • The interface intrinsic strengthening mechanism based interfacial microstructure is proposed. • The interface intrinsic strengthening mechanism complements the load transfer mechanism. Interface plays a crucial role to enhance the mechanical properties of metal-matrix composites. Here, we investigated and modulated the intrinsic characteristics of Al 2 O 3 /Al interface through interfacial doping by the first-principles calculations. The Al-terminated Al 2 O 3 (0 0 0 1)/Al (1 1 1) interface with OT stacking was found to be the most stable structure by calculating works of adhesion and interface energies. Then, the first principles tensile experiments were performed on the stable interfacial structure, and the tensile strength and elongation were calculated. It is revealed that there is no direct correlation between tensile properties and the work of adhesion or the interface energy. Systematical analysis on electronic structure indicates that the incorporation of doping elements will redistribute the electrons at the interfaces, and there is the interplay between the uniform electron distribution and the tensile properties, especially the elongation. It is found that Mg-doped and Cu-doped interface systems with more uniform electron distribution show better mechanical properties. Therefore, the interface intrinsic strengthening mechanism caused by the interfacial microstructure has a significant impact on the mechanical properties of the composite materials, and complements the load transfer mechanism in metal matrix composites. [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]