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Magnesium matrix composites are essential lightweight metal matrix composites, following aluminum matrix composites, with outstanding application prospects in automotive, aerospace lightweight and biomedical materials because of their high specific strength, low density and specific stiffness, good casting performance and rich resources. However, the inherent low plasticity and poor fatigue resistance of magnesium hamper its further application to a certain extent. Many researchers have tried many strengthening methods to improve the properties of magnesium alloys, while the relationship between wear resistance and plasticity still needs to be further improved. The nanoparticles added exhibit a good strengthening effect, especially the ceramic nanoparticles. Nanoparticle-reinforced magnesium matrix composites not only exhibit a high impact toughness, but also maintain the high strength and wear resistance of ceramic materials, effectively balancing the restriction between the strength and toughness. Therefore, this work aims to provide a review of the state of the art of research on the matrix, reinforcement, design, properties and potential applications of nano-reinforced phase-reinforced magnesium matrix composites (especially ceramic nanoparticle-reinforced ones). The conventional and potential matrices for the fabrication of magnesium matrix composites are introduced. The classification and influence of ceramic reinforcements are assessed, and the factors influencing interface bonding strength between reinforcements and matrix, regulation and design, performance and application are analyzed. Finally, the scope of future research in this field is discussed. [ABSTRACT FROM AUTHOR]

The Al-Cu-Mg-Si matrix composites reinforced with in situ hybrid-sized TiC x -TiB 2 particles with sizes ranging from 20 nm to 1.3 µm were successfully synthesized using the Al-Ti-B 4 C reaction system via a method that combined the combustion synthesis and the hot press assisted with hot extrusion. The sizes of the fabricated TiC x and TiB 2 particles increased with increasing TiC x -TiB 2 content. The hybrid-sized TiC x -TiB 2 particles improved the elevated-temperature yield strength ( σ .2 ), the tensile strength ( σ UTS ), and the fracture ductility ( ε f ) of the composites at both 493 K and 573 K. The 40 wt% (TiC x -TiB 2 )/Al-Cu-Mg-Si composite exhibited superior σ .2 (141 MPa), σ UTS (164 MPa), and ε f (31.2%) at 573 K, with enhancements of 60.2%, 72.6%, and 22.4% compared to the Al-Cu-Mg-Si matrix alloy (88 MPa, 95 MPa, and 25.5%). The improvement of the elevated-temperature mechanical properties for the in situ (TiC x -TiB 2 )/Al-Cu-Mg-Si composites was attributed primarily to the strengthening effects induced by the hybrid-sized TiC x -TiB 2 particles and the θ′ precipitation strengthening. [ABSTRACT FROM AUTHOR]

The bimodal-sized (micron+nano) TiC p /Al-Cu composites were successfully fabricated by adding the in situ micron-sized and nano-sized TiC p -Al master alloys into the molten Al-Cu alloy. The composites reinforced with bimodal-sized TiC p exhibited finer α-Al grains and smaller θ′ precipitates, and possessed enhanced room- and high-temperature strength and relatively high ductility compared with the Al-Cu matrix alloy and their counterparts reinforced with monomodal-sized TiC p . The improved tensile properties may be attributed to the more significant precipitation strengthening due to the smaller θ′ precipitates, grain refinement and strengthening effects of the nano-sized and micron-sized TiC p . [ABSTRACT FROM AUTHOR]

Adding various amounts of nano-sized TiC p (0.1–0.7 wt%) made a simultaneous improvement in high-temperature strength and ductility of the Al-Cu matrix alloy. The influences of temperature and strain rate on the high-temperature tensile properties and θ′ precipitate sizes in the Al-Cu matrix alloy and the nano-sized TiC p /Al-Cu composites were investigated. Theoretical calculations suggest that the yield strength increment of the composites at 453 K was primarily attributed to the strengthening effect of both the refined θ′ precipitates and TiC p , while at 493 K only the strengthening effect of TiC p was predominant due to the significant coarsening of θ′ precipitates at this temperature. [ABSTRACT FROM AUTHOR]

The in situ nano-TiC x /Al–Zn–Mg–Cu composites with different TiC x content (20, 25 and 30 vol.%) were successfully fabricated by combustion synthesis and hot press consolidation in Al–Ti–C/CNTs systems. The compressive properties and abrasive wear resistance of the composites improved with the increase in the TiC x content. The transformation of carbon source from pure C black to the mixture of C black and CNTs to pure CNTs in Al–Ti–C/CNTs systems leaded to a significant improvement in the compressive properties and wear resistance of the composites as well as a significant decrease in the average size of TiC x particles. The average size of the nano-TiC x particles in 30 vol.% TiC x /Al–Zn–Mg–Cu composite synthesized by the carbon source of CNTs reached 81 nm, moreover, the yield strength ( σ 0.2 ), the ultimate compression strength ( σ UCS ) and the fracture strain ( ɛ f ) of the composite reached 597 MPa, 882 MPa and 21.7%, respectively. [ABSTRACT FROM AUTHOR]

We report a new rolling route combining one pass of hard-plate rolling and two passes of conventional rolling. This route is efficient in achieving near-spherical Mg 17 Al 12 phase (~0.5 µm) and uniform fine-grained structure (~3 µm) featuring a weakened texture in AZ91-0.4Sn plates after a total thickness reduction of ~86.4% via 3 rolling passes. Moreover, the processed alloy exhibited superplasticity-like fracture strain of ~96% at 200 °C, owing to fine α-Mg grains distributed with a high volume fraction of Mg 17 Al 12 . This new route significantly reduces rolling passes and hence has a great potential for industrial production. [ABSTRACT FROM AUTHOR]

Using freeze casting and pressureless infiltration methods, we prepared lamellar Al−Si−Mg/Al 2 O 3 −ZrO 2 composites with initial ceramic loading of 30 vol% and different Al 2 O 3 :ZrO 2 weight ratios (Al 2 O 3 :ZrO 2 =1:9, 3:7, 5:5, 7:3 and 9:1). The resultant composites inherited the lamellar structure of the Al 2 O 3 −ZrO 2 scaffolds, and the thickness of both metal and ceramic layers showed a trend of first increase and then decrease with increasing Al 2 O 3 content. During pressureless infiltration, multiple chemical reactions took place between ZrO 2 and the Al−12Si−10Mg alloy and the main reaction products were (Al 1−m , Si m ) 3 Zr, Al 2 O 3 and ZrSi 2 phases. The degree of the reaction depended on the ZrO 2 content in the ceramic composition. In general, the compressive strength of the composites decreased with increasing Al 2 O 3 content, but three-point bending strength showed a first decrease and then increase. When Al 2 O 3 :ZrO 2 =1:9, the compressive and bending strength of the composites reached about 997±60 MPa and 426±10 MPa, respectively. A simple model was proposed to illustrate the fracture mode and toughening mechanism of the composites. [ABSTRACT FROM AUTHOR]

Inspired by nacre, we designed biomimetic metal–ceramic composites in which hard and ductile phases were alternately arranged. We first prepared lamellar-structured TiC scaffolds with 25, 30 and 35 vol% solid loadings using a unidirectional freeze casting technique and then measured wetting and infiltration dynamics for a commercial Al cast alloy, ZL107, with the main composition of Al–7Si–5Cu on the porous TiC scaffold using a modified sessile drop method at 850 °C. The wetting was affected by liquid spreading at horizontal surface and infiltration in depth, while the latter played a dominant role in the decrease in contact angle. On the basis of the wetting results, the lamellar ZL107/TiC composites were successfully fabricated by pressure infiltration of the molten ZL107 alloy into porous TiC scaffolds and their mechanical properties were evaluated. The compressive strength and elastic modulus increased while bending strength decreased with increasing TiC content, giving maximum values of 1166 ± 20 MPa, 205 ± 2 GPa and 363 ± 5 MPa, respectively. Formation of (Al m ,Si 1 − m ) 3 Ti, Al 3 Ti and Al 4 C 3 phases in the composites was presumed to deteriorate the toughness of the composites, leading to brittle fracture under loading. [ABSTRACT FROM AUTHOR]

• 66 wt% carbon fiber reinforced PEEK composite with strong interface was prepared. • The composite has ultra-high specific strengths exceeding majority of polymer or metal matrix composites. • The wear rate of composite is 1–2 orders of magnitude lower than materials with lubricating particles. • Excellent properties are attributed to high-mass carbon fibers and self-lubricating of composite. • A new idea is provided for the application of high-strength resin-based composite. It remains challenging to incorporate high-content fibers in fiber-reinforced polymer matrix composites to significantly enhance their mechanical properties. This work prepared polyether ether ketone (PEEK) matrix composite reinforced with 66 wt% carbon fibers with 0°/90° prepreg layer by compression molding, with aim to further increase the carbon fibers content in PEEK-based composites to improve the mechanical and wear properties at different temperatures, especially high temperature. The composite exhibits tensile and flexural strength of both exceeding 1000 MPa at room temperature, 810 ± 10 MPa and 521 ± 12 MPa at 200 °C and 458 ± 22 MPa and 290 ± 18 MPa at 300 °C, respectively. Especially at 300 °C, the composite demonstrates specific strength of 290 MPa/(g/cm3), which is superior to many magnesium or aluminum alloys (18–86 MPa/(g/cm3)). Further, the composite has a lower wear rate (5.47–12.80 × 10−7 mm3/Nm) at 200 °C by 1–2 orders of magnitude that of some materials with lubricating particles, and the wear surface is dominated by mild adhesive wear instead of abrasive wear at room temperature. The ultra-high mechanical and friction wear properties are attributed to the high content of staggered 90° carbon fibers, great interface bonding between the fibers and PEEK matrix, and self-lubricating effect of fibers and PEEK particles in the composite. This opens up a new performance level and provides a new idea for high-temperature applications of high-strength fiber-reinforced resin matrix composites. [ABSTRACT FROM AUTHOR]

2014 aluminum matrix composites reinforced with untreated (P-CNTs) and carboxyl-functionalized carbon nanotubes (C-CNTs) were successfully fabricated by the combination of sintering and hot extrusion. It is revealed that the C-CNTs are easier to disperse compared to the P-CNTs. Interfacial analysis indicated that a thin layer of aluminum carbide (Al 4 C 3 ) exists at the interface between the matrix and the P-CNTs. However, no obvious transition layers of Al 4 C 3 were observed at the interface of C-CNTs and 2014Al matrix in composites. Also, no preferred interfacial crystallographic orientation relationship between the C-CNTs and aluminum matrix was observed. Furthermore, C-CNTs have a larger effective interfacial contact with aluminum matrix compared to the untreated CNTs, due to large amount of –COOH group and defects on the surface of the C-CNTs interacting with Al by strong chemical and physical interactions. These aspects in turn affect the mechanical properties of the composites. The ultimate tensile strength of the composites were raised from 530 to 600 and 630 MPa with 0.5 wt.% of P-CNTs and C-CNTs, respectively. It reveals that the C-CNTs are more effective in strengthening the aluminum matrix than the P-CNTs. [ABSTRACT FROM AUTHOR]

The 70 wt.% (TiC x N y –TiB 2 )/Ni composites were fabricated successfully by the combustion synthesis and hot press consolidation of the Ni–Ti–Al–B 4 C–BN powder mixtures. The addition of Al to Ni–Ti–B 4 C–BN system significantly decreased the ignition difficulty of combustion synthesis, and improved the compression properties of (TiC x N y –TiB 2 )/Ni composites. The final products mainly consist of Ni, TiC x N y and TiB 2 , and the ceramic particles distribute uniformly in the composites. With increasing Al content from 0 to 8 wt.%, the average sizes of the TiC x N y and TiB 2 particles decrease a little, while the hardness and the compression strength increase firstly and then decrease, and the fracture strain increases. The composite with optimal 5 wt.% Al possesses the best comprehensive properties: the highest hardness (1794 Hv), the superior compression strength (3.76 GPa), and the fracture strain (4.2%), resulting in an overall increase by ~ 15%, ~ 28%, and ~ 45%, compared with these of the composite without the Al addition, respectively. [ABSTRACT FROM AUTHOR]

The (micron+nano) bimodal sized SiC p /Al2014 composites fabricated by semi-solid stirring exhibited fine α-Al grains, well-dispersed bimodal sized SiC p and well-bonded interface between SiC p and matrix. The yield and ultimate tensile strength of the extruded bimodal sized SiC p /Al2014 composites were significantly enhanced, compared to the extruded single-sized SiC p /Al2014 composites. [ABSTRACT FROM AUTHOR]

Abstract: Many experimental and theoretical studies indicated that the decrease of the size of the reinforcing particles can lead to substantial improvements in the mechanical performance of the composites. However, the investigations on the addition of the nano particles into conventional metal materials are still rare, especially the nano-TiC p into the Al–Cu alloys. In this study, the Ni coated nano-TiC p reinforced Al–Cu matrix composites were successfully fabricated by a casting route. It was found that the nano-TiC p was in the α-Al grains. The α-Al dendrites became finer and more developed. Moreover, the θ′ precipitates in the Al–Cu matrix were finer and uniformly distributed. The tensile strength and elongation of the composites increased simultaneously. After T6 heat treatment, compared with the unreinforced Al–Cu alloy, the tensile strength and elongation of the 0.8wt.% nano-sized TiC p /Al–Cu composite increased from 485MPa and 6.6% to 573MPa and 12.4%, respectively. [Copyright &y& Elsevier]

Abstract: The modification of Mg2Si in Mg–5Si alloys with KBF4 was investigated in detail. With the increase of KBF4 content, the alloys exhibited sub-modified and fully modified microstructures, but no over-modified microstructure was found. In the fully modified alloys, most of the primary Mg2Si particles exhibited the morphology of octahedrons. It is believed that B which came from the decomposition of KBF4 effectively confined the growth of primary Mg2Si to the octahedron morphology. [Copyright &y& Elsevier]

A great challenge in producing TiC reinforced metal matrix composites is encountered to directly add TiC particles into molten steel during casting owing to floating of nano-sized TiC on molten steels and agglomeration. As such, this work proposes a novel strategy using pre-distribution in situ nano-sized TiC/Al master alloy to fabricate 45 steel matrix composites reinforced with trace nano-sized TiC particles while without changing the original casting process; this strategy can effectively avoid the aforementioned challenge. The average grain sizes of as-cast and heat-treated 45 steel with 0.018 wt% nano-sized TiC particles remarkably decrease from 14.75 μm to 9.51 μm respectively to 8.77 μm and 5.46 μm respectively, which is attributed to that the nanoparticles provide effective nucleation sites and inhibit grain growth. Furthermore, adding trace nano-sized TiC particles significantly enhances their strength and toughness. The 45 steel matrix composites reinforced with 0.054 wt% nano-sized TiC particles exhibits the best tensile mechanical properties with yield strength of 624 MPa, ultimate strength of 920 MPa, elongation of 23.8% and impact toughness of 50.21 J/cm2, which are 19%, 13%, 10% and 38% respectively higher than the 45 steel. The strengthening and toughening mechanisms of 45 steel by nano-sized TiC are attributed to grain boundary strengthening, work hardening and dispersion strengthening. The strategy proposed in this work may provide a promising method for enhancing steel performances for industrial productions. • Using pre-distribution TiC/Al master alloy to fabricate 45 steel matrix composites. • Microstructure of 45 steels is significantly refined by trace nano-TiC. • 45 steel matrix composites exhibit significantly improved strength and toughness. • New strategy is fabricated for 45 steel matrix composites reinforced with nano-TiC. [ABSTRACT FROM AUTHOR]