Advances in Metal Matrix Composites: Structure, Properties and Applications

An overview of the effect of stirrer design on the mechanical properties of Aluminium Alloy Matrix Composites fabricated by stir casting

Laser Powder Deposition (LPD) is an additive layered manufacturing process that can deposit nearnet shape parts directly from metal powder. Metal Matrix Composites (MMCs) combine the merits of ductile metal matrix and hard ceramic reinforcement, providing enhanced properties including hardness and wear resistance. MMCs can be easily implemented in LPD process via blending the powders during deposition of coatings and 3-D parts. However, cracks induced by thermal stress and material embrittlement limit the application of MMCs in direct LPD processes. This study experimentally investigated the mechanical properties of MMCs deposited via LPD. Hardfacing alloy Stellite 6 and ductile alloy Inconel 718 were chosen as the matrix material, respectively, with spherical Tungsten carbide (WC) particles as the reinforcement. According to the experiment results, Inconel 718 was found to be a better choice for matrix material as it presented better compatibility with WC particles with acceptable wear resistance. Influence of direct age heat treatment of Inconel 718 matrix on mechanical properties was also investigated. Tensile tests showed that addition of WC particles in the matrix reduces both the ultimate strength and elongation. Microstructural observation of the tensile specimens indicated that WC particles are the preferable crack initiation sites, which significantly reduces the load-carrying capacity and ductility of the composite. Dissolution of WC into the matrix, which embrittles the matrix and further reduces the ductility of the composite, was proven by micro-hardness test and elemental analysis. Last, drying sliding test is conducted to evaluate the wear resistance of the MMCs. It was found that a small addition of WC particles can significantly increase the wear resistance.Laser Powder Deposition (LPD) is an additive layered manufacturing process that can deposit nearnet shape parts directly from metal powder. Metal Matrix Composites (MMCs) combine the merits of ductile metal matrix and hard ceramic reinforcement, providing enhanced properties including hardness and wear resistance. MMCs can be easily implemented in LPD process via blending the powders during deposition of coatings and 3-D parts. However, cracks induced by thermal stress and material embrittlement limit the application of MMCs in direct LPD processes. This study experimentally investigated the mechanical properties of MMCs deposited via LPD. Hardfacing alloy Stellite 6 and ductile alloy Inconel 718 were chosen as the matrix material, respectively, with spherical Tungsten carbide (WC) particles as the reinforcement. According to the experiment results, Inconel 718 was found to be a better choice for matrix material as it presented better compatibility with WC particles with acceptable wear resistance. Influe...

SECTION 1: INDUSTRIAL PERSPECTIVE Introduction Metal matrix composites for aeroengines Metal matrix composites in high performance internal combustion engines High modulus steel composites for automobiles Metal matrix composites for aerospace structures Ceramic matrix composites for industrial gas turbines Composite superconductors SECTION 2: MANUFACTURING AND PROCESSING Introduction Fabrication and recycling of aluminium metal matrix composites Aluminium metal matrix composites by reactive and semi-solid squeeze casting Deformation processing of particle reinforced metal matrix composites Processing of titanium-silicon carbide fibre composites Manufacture of ceramic fibre-metal matrix composites SECTION 3: MECHANICAL BEHAVIOUR Introduction Deformation and damage in metal matrix composites Fatigue of discontinuous metal matrix composites Mechanical behaviour of intermetallics and intermetallic matrix composites Fracture of titanium aluminide-silicon carbide fibre composites Structure-property relationships in ceramic matrix composites Microstructure and performance limits of ceramic matrix composites SECTION 4: NEW FIBRES AND COMPOSITES Introduction Silicon carbide based and oxide fibre reinforcements High-strength high-conductivity copper composites Porous particle composites Active composites Ceramic nanocomposites Oxide eutectic ceramic matrix composites

Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

Carbon nanotube reinforced metal matrix nanocomposite can be fabricated by using several processes: namely powder metallurgy, molecular-level-mixing, electrodeposition, melt stirring, etc. In this work, carbon nanotube reinforced copper matrix nanocomposites were fabricated by employing the simple powder metallurgy method. Prepared nanocomposites have been characterized by using various characterisation techniques: namely compression test, hardness and density measurement. Morphology and microstructure of composite samples were characterised by using SEM. Properties of the metal matrix nanocomposites were correlated with the microstructure. Experimental results revealed that the density and the specific wear rate of the nanocomposites samples are slightly decreased with the increment of carbon nanotube reinforcement in the metal matrix. Compressive strength of the nanocomposite samples are dramatically increased (155% improvement) with carbon nanotube reinforcement in the copper matrix, while Rockwell hardness number of the samples are slightly increased (22.5% improvement) with an increment of carbon nanotube reinforcement in the matrix material.

Abrasive waterjet machining (AWJM) is one of the non-traditional machining processes used for machining hard and difficult materials including metal matrix composites (MMCs) and ceramic matrix composites (CMCs). MMCs and CMCs are widely used in the industries such as automobile, aerospace, defense, etc. In AWJM, the material is removed by a narrow stream of high pressure water along with abrasive particles. This work, reviews the research work carried out on the machining aspects of MMCs and CMCs using AJWM. Most of the research work in MMCs is carried out on aluminum based matrix reinforced with ceramics such as silicon carbide (SiC) and aluminum oxide (Al2O3) in various proportions. In the case of CMCs, the research work mostly are carried out on alumina (Al2O3) based work specimen. Generally, it is observed that the reinforcement particles in the MMCs and CMCs greatly influence the output process parameters like depth of the cut, material removal rate (MRR), surface roughness (Ra), kerf width, etc. From the literature review, it is observed that the increase in volume percentage of reinforced abrasive particles results in decreased MRR, decreased in the depth of cut and increase in the Ra. This work also covers the future research work in the machining aspects of MMCs and CMCs.

Composites have tremendous applicability due to their excellent capabilities. The performance of composites mainly depends on the reinforcing material applied. Graphene is successful as an efficient reinforcing material due to its versatile as well as superior properties. Even at very low content, graphene can dramatically improve the properties of polymer and metal matrix composites. This article reviews the fabrication followed by mechanical and tribological properties of metal and polymer matrix composites filled with different kinds of graphene, including single-layer, multilayer, and functionalized graphene. Results reported to date in literature indicate that functionalized graphene or graphene oxide-polymer composites are promising materials offering significantly improved strength and frictional properties. A similar trend of improved properties has been observed in case of graphene-metal matrix composites. However, achieving higher graphene loading with uniform dispersion in metal matrix composites remains a challenge. Although graphene-reinforced composites face some challenges, such as understanding the graphene-matrix interaction or fabrication techniques, graphene-reinforced polymer and metal matrix composites have great potential for application in various fields due to their outstanding properties.

In many todays engineering application, hybrid composites with two or more reinforcement of high strength are more demanding. In hybrid composites, the composite properties easily controlled for possible extent by the selection of fibers and matrix by adjusting fabric layers arrangement. In this work, we report the development of carbon-Kevlar/Epoxy hybrid composites in hand layup using vacuum bagging approach followed with post curing and investigate its characteristics of inter-laminar shear strength for the various sequences, so that the scope of use of newly developed composites might be proven. Short beam tests were conducted on the hybrid composites of different arrangements of Carbon and Kevlar reinforcements in epoxy matrix. Property considered for studying the composites are Inter-laminar shear strength. The experimental data and study revealed that Carbon-Kevlar/Epoxy hybrid composite with carbon reinforcements as a face sheets have significant effect on the Inter-laminar shear strength when compared to the other arrangements.In many todays engineering application, hybrid composites with two or more reinforcement of high strength are more demanding. In hybrid composites, the composite properties easily controlled for possible extent by the selection of fibers and matrix by adjusting fabric layers arrangement. In this work, we report the development of carbon-Kevlar/Epoxy hybrid composites in hand layup using vacuum bagging approach followed with post curing and investigate its characteristics of inter-laminar shear strength for the various sequences, so that the scope of use of newly developed composites might be proven. Short beam tests were conducted on the hybrid composites of different arrangements of Carbon and Kevlar reinforcements in epoxy matrix. Property considered for studying the composites are Inter-laminar shear strength. The experimental data and study revealed that Carbon-Kevlar/Epoxy hybrid composite with carbon reinforcements as a face sheets have significant effect on the Inter-laminar shear strength when com...

Metal matrix composites (MMCs) are composed of a metal matrix and a reinforcement, which confers excellent thermally conductive and mechanical performance. High thermal conductivity MMCs have special advantages for particular electronic packaging and thermal management applications because of their combination of excellent thermal conductivity, relatively low density, and tailorable coefficient of thermal expansion (CTE) to match the CTE of semiconductor materials such as silicon, gallium arsenide, or alumina. The optimal design of MMC components is based on appropriate selection of matrix materials, reinforcements, and layer orientations to tailor the properties of a component to meet the needs of a specific design. The specific factors that influence the characteristics of MMCs include reinforcement properties, shape of the dispersed phase inclusions (particles, flakes, fibers, laminates), and orientation arrangement of the dispersed phase inclusions, such as random or preferred; reinforcement volume fraction; matrix properties, including effects of porosity; reinforcement-matrix interface properties; residual stresses arising from the thermal and mechanical history of the composite; and possible degradation of the reinforcement resulting from chemical reactions at high temperatures, and mechanical damage from processing, impact, etc. In the absence of ductility to reduce stress concentrations, joint design becomes a critical design consideration. Numerous methods of joining MMCs have been developed, including metallurgical and polymeric bonding and mechanical fasteners. This chapter will give a brief review about the processing of these composites and their performance and applications in the thermal management of electronic packaging. The contents will include typical processing methods for MMCs, the principal high conductivity for MMCs such as aluminum, copper, and their alloy-based MMCs, and to a lesser extent, other MMCs based on beryllium and silver, etc., as well as low CTE composite solders and advanced multifunctional laminates.

Carbon-based nanomaterials mainly including carbon nanotubes (CNTs), graphene, and graphene oxide (GO) have superior properties of low density, outstanding strength, and high hardness. Compared with ceramic reinforcements, small amount of carbon-based nanomaterials can significantly improve the mechanical properties of metal matrix composites (MMCs) and ceramic matrix composites (CMCs). However, CNTs and graphite always aggregate or degrade during the fabrication with a high temperature, especially in MMCs. GO has the advantages of easier to be dispersed in other materials and better high-temperature stability. Laser-directed energy deposition (DED) has been used to fabricate GO-MMCs and GO-CMCs due to the unique capabilities of coating, remanufacturing, and producing functionally graded materials. Laser DED, as a fusion manufacturing process, could fully melt the material powders, which could refine the microstructure and increase the density and mechanical properties. However, GO could react with matrix materials at high temperatures. The survival, degradation, and reactions of GO in laser DED fabricated GO-MMCs and GO-CMCs are still unknown. There is also no investigation on the reinforcement mechanisms of GO in metal matrix materials and ceramic matrix materials in the laser DED process. In this study, GO-reinforced Ti (GO-Ti) and GO-reinforced zirconia toughened alumina (GO-ZTA) parts were fabricated by laser DED process. Raman spectrum, XRD analysis, and EDS analysis have been applied to investigate the forms of GO in both DED fabricated GO-MMCs and GO-CMCs. The reinforcement mechanisms of GO on microhardness and compressive properties of MMCs and CMCs have been analyzed.

Titanium based metal matrix composites (MMCs) with continuous fibers first gained prominence as enabling structural materials for the National Aerospace Plane (NASP). Some of the peculiar deformation and damage characteristics of MMCs were identified, explained, and modeled as part of the NASP program activities in the early 1990s. Much was discovered and learned regarding the behavior of MMCs under a variety of thermal and mechanical load combinations. Analytical and numerical models of deformation and damage were developed and validated. Significant progress was achieved in proper viscoplastic characterization of the matrix materials and micromechanics based deformation and damage modeling of MMCs. These research activities, which actually outlasted the NASP program, resulted in major advances in understanding, characterization, and modeling of MMCs. However, virtually all-modeling activity remained focused on unidirectional loading of MMCs. To some extent, virtually all aircraft propulsion system and structural components are subjected to multiaxial stresses. Therefore, while the understanding and the modeling techniques developed under the NASP program represented a major step forward, additional steps were needed to reach a level where models could be used in the design and life prediction of actual components. Overlapping NASP related activities, efforts were underway by the major jet engine manufacturers under the Integrated High Performance Turbine Engine Technology (IHPTET) program to design and test propulsion system components involving the use of MMCs. These activities were mainly focused on fabricating and testing metallic rotors with unidirectional MMC inserts. The inserts were toroids of various cross-sections, with fibers along the circumferential direction. Initial sub-component and component level testing of rings and rotors indicated that the existing design and stress analysis methods were inadequate in predicting the deformation and damage behavior of MMCs under biaxial (hoop and radial) stresses. Instigated by IHPTET needs, a project was initiated with the following objectives: (a) develop a theory for predicting MMC damage and deformation response under multiaxial stress states caused by general time dependent thermomechanical loading, (b) validate the theory by comparing predictions with laboratory test measurements, and (c) incorporate the theory in a stress analysis procedure that can be used by design engineers. The project was focused on unidirectional titanium based matrix composites with silicon carbide fibers. The paper will consist of a summary of progress that has been achieved in the above project. Specifically, outline of a theory for predicting deformation and damage of MMCs under multiaxial stress states will be presented. The theory includes consideration of dominant damage mechanisms associated with titanium matrix composites, processing induced residual stresses, and time, temperature, and strain rate dependent inelastic deformation. This will be followed by a description of how the theory is implemented in a nonlinear finite element analysis procedure. Finally, examples of comparison between theoretical predictions and experimental measurements will be presented.

The effective properties of metal matrix composites (MMCs) depend on matrix material and reinforcement property specifications as well as bonding at interphase. The use of numerical methods such as finite element (FE) and mean field homogenization (MFH) can assist in predicting MMC properties thus reducing time and cost of optimizing composite properties through experiments. In the present work, a multiscale representative volume element (RVE) of the microstructure of reduced graphene oxide (rGO) reinforced Aluminium (Al) matrix composite (rGO/Al) is created in MSC DigiMat and analysed using Abaqus software. The effect of porosity and rGO reinforcement on thermal conductivity and strength of the rGO/Al composites is studied. The variation in thermal conductivity between FE-RVE and experimental data is a maximum of 2.2% and a minimum of 0.07% for rGO reinforcement of 1 wt.% and 3 wt.% respectively. The results show good agreement between FE-RVE simulation, MFH and experimental data. This approach can provide an efficient technique for selecting matrix and reinforcement phase properties for MMC fabrication. Keywords: Al/rGO composite, Multiscale finite element-representative volume, Thermal and mechanical properties

Effect of Nanoparticle Reinforcement in Metal Matrix for Structural Applications

This review focuses on the known theoretical and experimental results in the field of obtaining metal matrix composite materials by processing the melts using physical methods in the conditions of casting and metallurgical processes. The possibilities, advantages and disadvantages of various physical impact methods are considered from the standpoint of their effect on the structural and morphological characteristics, physicomechanical and operational properties of cast composite materials based on aluminum and its alloys. The paper provides a classification and a detailed description of physical methods used for melt processing when obtaining metal matrix composites depending on the melt state during processing (melting, pouring and crystallization) and according to the physical principle of the effects applied (thermal, electromagnetic, cavitation, mechanical, etc). The paper describes a contemporary view of the laws and mechanisms of the effect exerted by melt processing using physical methods on the structure and phase formation processes of as-cast metal matrix composites. The currently known effects of the impact on their structure are described from a qualitative and quantitative point of view, in particular, effects associated with a change in the wettability of particles, their distribution, dispersion and morphology, as well as with a change in the structural state of the matrix material. The paper systematizes the data on the properties of metal matrix composites obtained using physical impacts on the melt during melting and crystallization. The research shows the prospects for the development and practical application of physical impact methods for melts in the production of metal matrix composites based on various matrix materials and reinforcement systems including endogenously, exogenously and integrally reinforced composite materials. Priority areas of theoretical research and experimental development are discussed highlighting discussion areas and issues in the field of obtaining metal matrix composites using physical impacts on melts during melting and crystallization. Areas for future research in this field are proposed based on the systematic analysis of key problems limiting the widespread industrial use of physical methods for melt processing.

Metal matrix composites (MMCs) are frequently employed in various advanced industries due to their high modulus and strength, favorable wear and corrosion resistance, and other good properties at elevated temperatures. In recent decades, additive manufacturing (AM) technology has garnered attention as a potential way for fabricating MMCs. This article provides a comprehensive review of recent endeavors and progress in AM of MMCs, encompassing available AM technologies, types of reinforcements, feedstock preparation, synthesis principles during the AM process, typical AM-produced MMCs, strengthening mechanisms, challenges, and future interests. Compared to conventionally manufactured MMCs, AM-produced MMCs exhibit more uniformly distributed reinforcements and refined microstructure, resulting in comparable or even better mechanical properties. In addition, AM technology can produce bulk MMCs with significantly low porosity and fabricate geometrically complex MMC components and MMC lattice structures. As reviewed, many AM-produced MMCs, such as Al matrix composites, Ti matrix composites, nickel matrix composites, Fe matrix composites, etc, have been successfully produced. The types and contents of reinforcements strongly influence the properties of AM-produced MMCs, the choice of AM technology, and the applied processing parameters. In these MMCs, four primary strengthening mechanisms have been identified: Hall–Petch strengthening, dislocation strengthening, load transfer strengthening, and Orowan strengthening. AM technologies offer advantages that enhance the properties of MMCs when compared with traditional fabrication methods. Despite the advantages above, further challenges of AM-produced MMCs are still faced, such as new methods and new technologies for investigating AM-produced MMCs, the intrinsic nature of MMCs coupled with AM technologies, and challenges in the AM processes. Therefore, the article concludes by discussing the challenges and future interests of AM of MMCs.