Metal Matrix Vomposites – From Science to Technological Significance

ArticleinComposites Science and Technology 65(15-16):2526-2540 · December 2005with 1,129 Reads 
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Abstract
Over the past two decades – a period coinciding with publication of Composites Science and Technology – metal matrix composites (MMCs) have been transformed from a topic of scientific and intellectual interest to a material of broad technological and commercial significance. The worldwide MMC markets in 1999 accounted for 2500 metric tons valued at over $100M. Important MMC applications in the ground transportation (auto and rail), thermal management, aerospace, industrial, recreational and infrastructure industries have been enabled by functional properties that include high structural efficiency, excellent wear resistance, and attractive thermal and electrical characteristics. A suite of challenging technical issues has been overcome, including affordable primary and secondary processing, material design and development methodologies, and characterization and control of interfacial properties. This article describes the technological features that characterize the MMC industry. Matrix/reinforcement systems and primary and secondary processes of commercial significance will be broadly described. Several metrics that underscore the growing maturity of the MMC industry will be discussed, including the emergence of a second tier support industry and the growth of standardized materials and methods. MMC applications in the major markets of ground transportation, thermal management, aerospace, industrial, recreational and infrastructure will be described. Successful commercialization strategies will be discussed and insights for achieving expanded MMC applications will be given. A forward look at candidate approaches for the next generation of MMCs will be provided, including projections of new MMC paradigms.

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  • ... the size, shape, and volume fraction of the ceramic reinforcements [1-10]. Recently, considerable technological advances in the manufacture of MMCs have enabled the use of these composites not only in high-tech industries such as aerospace, recreation, and infrastructures but also in everyday life [1,2,[10][11][12][13][14][15]. ...
    ... Among several commercial MMCs, the aluminum matrix composites (AMCs) occupy approximately 70% of the global market. A variety of AMC manufacturing processes have been developed over the decades, with representative commercial processes including stir casting, infiltration, and powder metallurgy [1,12,15]. Generally, the ceramic reinforcement should be embedded and dispersed in the aluminum matrix to produce the AMC. However, poor wettability between the aluminum and the ceramic reinforcement makes this difficult. ...
    ... However, poor wettability between the aluminum and the ceramic reinforcement makes this difficult. Efforts have therefore been made to overcome this inherent issue by high-energy stir casting, high-pressure infiltration of molten aluminum into a preform, or consolidation of a mixture of aluminum and reinforcement powders (powder metallurgy) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. However, these commercial methods require complicated multi-step processes along with additional equipment or catalysts, which increase both the processing time and cost of the final products. ...
    Article
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    This paper investigates the effect of the size and volume fraction of SiC, along with that of the processing temperature, upon the nitridation behavior of aluminum powder during the nitridation-induced self-formed aluminum composite (NISFAC) process. In this new composite manufacturing process, aluminum powder and ceramic reinforcement mixtures are heated in nitrogen gas, thus allowing the exothermic nitridation reaction to partially melt the aluminum powder in order to assist the composite densification and improve the wetting between the aluminum and the ceramic. The formation of a sufficient amount of molten aluminum is key to producing sound, pore-free aluminum matrix composites (AMCs); hence, the degree of nitridation is a key factor. It was demonstrated that the degree of nitridation increases with decreasing SiC particle size and increasing SiC volume fraction, thus suggesting that the SiC surface may act as an effective pathway for nitrogen gas diffusion. Furthermore, it was found that effective nitridation occurs only at an optimal processing temperature. When the degree of nitridation is insufficient, molten Al is unable to fill the voids in the powder bed, leading to the formation of low-quality composites with high porosities. However, excessive nitridation is found to rapidly consume the nitrogen gas, leading to a rapid drop in the pressure in the crucible and exposing the remaining aluminum powder in the upper part of the powder bed. The nitridation behavior is not affected by these variables acting independently; therefore, a systematic study is needed in order to examine the concerted effect of these variables so as to determine the optimal conditions to produce AMCs with desirable properties for target applications.
  • ... They are used under extreme operating conditions such as high load, elevated temperature, and extensive wear operations [2,25,29,30]. MMCs have gained wide popularity in the aerospace, biomedical, electronics, and various engineering applications [2,[31][32][33][34][35]. They are difficult to process by conventional machining techniques due to high hardness and melting point [2,[36][37][38]. ...
    ... Another unique feature of the LMD is "cladding", i.e., coating of a surface with a layer of metal or MMCs. This process is usually carried out on the surfaces of bulk (new/worn-out) materials with the emphasis on enhancing the surface characteristics or obtaining the desired biological, frictional, or chemical characteristics for a given material [2,[31][32][33][34][35]. ...
    ... Materials 2020, 13, x FOR PEER REVIEW 3 of 27 emphasis on enhancing the surface characteristics or obtaining the desired biological, frictional, or chemical characteristics for a given material [2,[31][32][33][34][35]. ...
    Article
    Full-text available
    Metal matrix composites (MMCs) present extraordinary characteristics, including high wear resistance, excellent operational properties at elevated temperature, and better chemical inertness as compared to traditional alloys. These properties make them prospective candidates in the fields of aerospace, automotive, heavy goods vehicles, electrical, and biomedical industries. MMCs are challenging to process via traditional manufacturing techniques, requiring high cost and energy. The laser-melting deposition (LMD) has recently been used to manufacture MMCs via rapid prototyping, thus, solving these drawbacks. Besides the benefits mentioned above, the issues such as lower ultimate tensile strength, yield strength, weak bonding between matrix and reinforcements, and cracking are still prevalent in parts produced by LMD. In this article, a detailed analysis is made on the MMCs manufactured via LMD. An illustration is presented on the LMD working principle, its classification, and dependent and independent process parameters. Moreover, a brief comparison between the wire and powder-based LMDs has been summarized. Ex- and in-situ MMCs and their preparation techniques are discussed. Besides this, various matrices available for MMCs manufacturing, properties of MMCs after printing, possible complications and future research directions are reviewed and summarized.
  • ... The production technology and thermomechanical processing will partially determine the feasibility of using the MMC in a finished product. Research activities and industrial applications of Al-, Ti-, and Mg-based MMCs has significantly evolved over the past 25 years, as documented by Clyne (1993) [5], Miracle (2005) [6], and Srivatsan et al. (2018) [7]. Nowadays, laboratory-scale research aims to test different concepts ex situ and in situ to increase applications of MMCs [8]. ...
    ... The production technology and thermomechanical processing will partially determine the feasibility of using the MMC in a finished product. Research activities and industrial applications of Al-, Ti-, and Mg-based MMCs has significantly evolved over the past 25 years, as documented by Clyne (1993) [5], Miracle (2005) [6], and Srivatsan et al. (2018) [7]. Nowadays, laboratory-scale research aims to test different concepts ex situ and in situ to increase applications of MMCs [8]. ...
    Article
    This study uses the stir-casting technique to combine a semi-solid AA2024 alloy directly with finely-sized β-SiCp embedded as a powder or with mechanically alloyed granules as a delivery agent. Liquid-state primary fabrication tends to form agglomerates of reinforcement particles, whereas rolling better distributes the composite constituents. Sub-micron reinforcements of low volume fractions do not significantly increase the hardness of the composite materials. Uniaxial tensile testing at elevated temperatures over a wide range of strain rates showed simultaneous increases in the ductility and crack resistance of AA2024 + SiCp granules embedded as a powder when compared to the non-reinforced control material at lower strain rates, with the same toughness as the control material. The maximum engineering strain of 252.7 ± 19.2% was observed in AA2024/SiCp at a strain rate of 10⁻⁴ s⁻¹. This improvement in properties is attributed to grain refinement in the MMCs, leading to pinning events during the straining and ductility increases. The resultant impediments to grain growth and crack propagation allow the fine-sized reinforcements to control dynamic microstructural changes during fatigue. Cube {001}<100> is a dominant texture component in AA2024, whereas the Goss {011}<100> and S {123}<634> components mainly represent the texture of the discontinuously reinforced aluminum matrix.
  • ... Cast aluminum alloys and composites are attractive as engineering materials due to their low density and good corrosion resistance in a variety of industrial environments [1][2][3][4][5][6][7]. Especially due to their excellent castability and weldability, Al-Si-based composites are most widely utilized in various applications [1,2,[7][8][9]. ...
    ... Cast aluminum alloys and composites are attractive as engineering materials due to their low density and good corrosion resistance in a variety of industrial environments [1][2][3][4][5][6][7]. Especially due to their excellent castability and weldability, Al-Si-based composites are most widely utilized in various applications [1,2,[7][8][9]. The mechanical properties of Al-Si-based composites can be improved by Mg addition through the precipitation of Mg 2 Si [1,2]. However, the achievable improvement of the mechanical properties through precipitation hardening degenerates at elevated temperatures because of the high diffusivity of Mg inducing coarsening of the precipitates at high-temperatures and the dissolution of Si [10][11][12][13]. ...
  • ... These materials are described as possessing a blend of properties that are characterized by very good and suitable mechanical properties and at the same time a significant meting point, which can reach up to 3000 °C and even exceed this value [13,21]. Metallic composites are manufactured by reinforcing various types of metal matrices, such as titanium, aluminum, copper, magnesium, etc. [19]. Typical blends for metal composites are ceramic particle or fiber in particular, but carbon fiber or metallic fiber can also be used. ...
    ... Metallic composites are manufactured by reinforcing various types of metal matrices, such as titanium, aluminum, copper, magnesium, etc. [19]. Typical blends for metal composites are ceramic particle or fiber in particular, but carbon fiber or metallic fiber can also be used. ...
    Article
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    This paper is focused on the basic properties of ceramic composite materials used as thermal barrier coatings in the aerospace industry like SiC, ZrC, ZrB2 etc., and summarizes some principal properties for thermal barrier coatings. Although the aerospace industry is mainly based on metallic materials, a more attractive approach is represented by ceramic materials that are often more resistant to corrosion, oxidation and wear having at the same time suitable thermal properties. It is known that the space environment presents extreme conditions that challenge aerospace scientists, but simultaneously, presents opportunities to produce materials that behave almost ideally in this environment. Used even today, metal-matrix composites (MMCs) have been developed since the beginning of the space era due to their high specific stiffness and low thermal expansion coefficient [1]. These types of composites possess properties such as high-temperature resistance and high strength, and those potential benefits led to the use of MMCs for supreme space system requirements in the late 1980s. Electron beam physical vapor deposition (EB-PVD) is the technology that helps to obtain the composite materials that ultimately have optimal properties for the space environment, and ceramics that broadly meet the requirements for the space industry can be silicon carbide that has been developed as a standard material very quickly, possessing many advantages. One of the most promising ceramics for ultrahigh temperature applications could be zirconium carbide (ZrC) because of its remarkable properties and the competence to form unwilling oxide scales at high temperatures, but at the same time it is known that no material can have all the ideal properties [2]. Another promising material in coating for components used for ultra-high temperature applications as thermal protection systems is zirconium diboride (ZrB2), due to its high melting point, high thermal conductivities, and relatively low density [3]. Some composite ceramic materials like carbon-carbon fiber reinforced SiC, SiC-SiC, ZrC-SiC, ZrB2-SiC, etc., possessing low thermal conductivities have been used as thermal barrier coating (TBC) materials to increase turbine inlet temperatures since the 1960s. With increasing engine efficiency, they can reduce metal surface temperatures and prolong the lifetime of the hot sections of aero-engines and land-based turbines.
  • ... Composite materials which are generated by combining the reinforcement phase with matrix help to obtain higher quality materials. [1][2][3] According to the physical and chemical properties of matrix structure, they can be divided into three groups. These are metal, plastic, and ceramic matrix composites. ...
    ... 6,7 Today, MMCs have substituted monolithic and traditional alloys in many engineering applications in the automotive, aerospace, electrical, and defense industries. 2,3 Aluminum which is the most common matrix used in MMC has many advantages like low density, solid solution strengthening, high corrosion resistance, high heat and electrical conductivity, formability, and ease of obtaining. Such advantages make them preferable in many complex industrial applications. ...
    Article
    Full-text available
    Aluminum matrix composite materials being used in different sectors including automobile, aerospace, defense, and medical and are currently displacing unreinforced materials with their superior mechanical properties. The metal removal process of drilling is widely used in many structural applications. This study experimentally investigates the drilling characteristics of silicon carbide (SiC p )-reinforced Al 7075 composites produced by stir casting method. Also, two different drill materials with high-speed steel (HSS) and titanium nitride (TiN)-coated HSS carry out in drilling operation. The effect of operational parameters such as cutting speed and feed rate and materials parameters such as weight fraction of reinforcement and cutting tools on the surface roughness of drilled holes were evaluated in the drilling operations. The results of the drilling test indicate that the feed rate and cutting speed have a very strong effect on the surface roughness of matrix alloy and composite materials. The surface roughness ( R a ) values increased with increasing the feed rate and decreased with increasing the cutting speed. Under 0.10 mm/rev and 20 m/min drilling conditions and using HSS drill, surface roughness values for matrix, 5% SiC-, 10% SiC-, and 15% SiC-reinforced composites, were obtained 2.57, 2.59, 2.61, and 2.64 µm, respectively; besides, using TiN-coated HSS drill, surface roughness values were obtained 1.60, 1.63, 1.64, and 1.66 µm, respectively. An increase in the weight fraction of the abrasive SiC particle resulted in a very crucial deterioration quality of the drilled hole. TiN-coated HSS drills better performance exhibits than uncoated HSS drills for all the drilling operations about surface roughness properties. Short chip formations observed both the matrix alloy and the composite materials for two different drills in the drilling operations.
  • ... Today there are more than ten known methods and technologies in additive manufacturing of parts, and new ones appear every year. The most widely used AT for manufacturing of 3D parts is the selective laser melting (SLM) [1][2][3]. ...
    ... The alloy separation during solidification was found for the first time, i.e., the formation of three zones with clear boundaries inside each layer applied (see Fig. 5). Previously, during study of the singlelayer coatings of surface strengthening with the use of the В 4 С + Тi or TiB, or TiC powder mixtures, the formation of such zones was not observed [1,2,[4][5][6][7][10][11][12]. The important feature of these zones is the difference in the morphology; each zone has its own set of phases. ...
    Article
    Full-text available
    Increasing performance requirements of advanced products demands new, versatile fabrication techniques. Additive technology represents one of the most prospective fields of future production. B4C-based composites were fabricated on titanium substrate by selective laser melting (SLM) using titanium (Ti-6Al-4V) and boron carbide (B4C) powder mixture at different weight ratio (Ti:B4C = 1:0, 9:1, 8:2, and 7:3). It was shown that the use of a powder mixture В4С + Ti-6Al-4V with ceramic concentration of more than 10% of weight led to formation of cracks. The microstructure of composites was studied by optical and electron microscopy. It was shown that a heterogeneous structure was formed with regular allocation of zones inside each layer. It was established that new chemical compounds (TiB, TiB2, TiC) absent in the initial powder mixture were formed in the new structure. A significant change in microhardness is shown (for sample without ceramics—372 HV0.3, for sample 10% В4С + 90% Ti-6Al-4V—from 548 to 4214 HV0.3). It was shown that the wear loss of B4C-free sample is approximately 4.2 times higher than that of the sample with 10 wt% В4С.
  • ... MMCs are composites which use metals as matrix materials. According to [63], the most commonly used matrix materials are aluminium and magnesium alloys. However, more recently, ferrous-based matrix materials have attracted considerable attention in industry and research due to their low cost and good mechanical properties with higher strength compared to aluminium and magnesium [64]. ...
    ... These composites are used in wide range of industrial operations such as cutting, rolling, stamping, piercing, warm metalworking, drawing, forming and punching. Components include hammers, impact dies, canning tools, crimp rollers, check valves, extruder nipples, bending dies, extrusion dies, and hot forging die inserts [63]. ...
    Article
    Full-text available
    The contribution at hand presents the implementation of a non-linear constitutive model for rate-dependent inelasticity into the scaled boundary finite element method (SBFEM). To increase the numerical efficiency and simplify the formulation, the stress update algorithm is only performed at the scaling centre of the polytope elements. The presented SBFEM framework is ideally suited for the image-based analysis of composites since many matrix materials exhibit rate-dependent inelasticity, particularly at high temperatures. Thereby, meshes are generated based on images of the complex microstructures by employing an efficient quadtree-decomposition. The main advantage of this approach lies in its high degree of automation requiring only minimal intervention by the user. Various benchmark examples are presented to verify the formulation. Furthermore, the influence of jagged boundaries, resulting from the quadtree decomposition, on the accuracy and convergence of results is discussed in detail. The paper concludes with the study of a metal-matrix composite, whereby rate-dependent inelasticity is taken into account to model the mechanical behaviour of the matrix.
  • ... As a structural material, aluminium (Al) and its alloys have been widely used in automotive, defence and aerospace manufacturing industries since they offer reduced weight, high strength, ductility and stiffness, better fatigue and wear resistance, anti-corrosion property and high thermal stability as well as electrical conductivity [1][2][3][4]. However, the relatively poor seizure resistance, inferior structural efficiency, poor meting point, insufficient tribological behaviour have restricted their uses in these above mentioned applications [5][6][7][8]. These properties can further be improved by the dispersion of suitable particulates or fibres into Al matrix. ...
    Article
    In this paper, the effect of sintering techniques (conventional, CS and electric resistance, ERS) and SiC content (1, 3 and 5 wt. %) on the microstructural, mechanical and tribological properties were investigated. Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were performed for microstructural investigation. Density, porosity and hardness were evaluated at different weight fractions of SiC for comparative study. Tribological behaviour was evaluated in terms of wear loss and coefficient of friction (COF). Worn-out surfaces and formed debris were also studied using SEM for understanding the wear mechanism. Results indicated that addition of SiC improved the hardness, wear resistance and COF. With addition of 5 wt. % SiC the hardness improved by 32 % for CS and 30% for ERS, wear resistance improved by 37 % for CS and 40% for ERS while COF improved by 3 % for CS (3 wt.% SiC) and 6 % for ERS (5 wt.% SiC) compared to neat Al. ERS processed composites resulted in better densification, improved hardness (12-14%) and tribological behaviour (wear resistance 36-39 % and COF 7-15 %) for 1-5 wt. % SiC compared to CS processed ones. Abrasion, adhesion and delamination were the controlling wear mechanism for Al-SiC composites with lesser adhesion wear in ERS composites.
  • ... Composite materials have become a need in the modern decade to obtain numerous properties which were not achieved by monolithic materials. It caters the increasing demand for enhanced mechanical and tribological properties in aerospace, marine, defence and automotive applications [1][2][3]40]. The commonly used techniques in fabrication of hybrid metal matrix composites (HMMC) are stir casting and powder metallurgy technique. ...
    Article
    Full-text available
    Aluminium hybrid metal matrix composites comprises of Al alloy embedded with multiple hard particulates to improve the wear characteristics. In this study Al 7075/Al 2 O 3 /B 4 C hybrid composite was fabricated with 5 wt.% B 4 C particles addition and 2, 4, 6, 8 and 10 wt.% of Al 2 O 3 by liquid metallurgy route. The dry sliding wear behaviour of hybrid composites was investigated under various sliding parameters using a pin on disc tribometer. Numerical models were developed to predict the frictional and wear characteristics of the composites. Analysis of variance method and confirmation experiments were employed to validate the adequacy of the developed model. The composites with high particle content exhibits better wear resistance at various sliding conditions. Detailed metallurgical investigations were carried out on the on worn surface. The wear rate was severe at higher loads due to the crater formation and in addition to abrasive wear. The wear rate and coefficient of friction were optimized using desirability based multi criteria optimization technique.
  • ... Material research coupled with developments in profitable manufacturing methods led the MMC industry to support demanding markets in different sectors. 4,5 Different liquid state fabrication routes are identified for Al nanocomposites such as stir casting (SC), ultrasonic SC, compocasting/rheoforming, squeeze casting, spray forming, in situ analysis, and liquid metal infiltration. Whereas popular solid state methods are conventional powder metallurgy (PM), high-energy ball milling/mechanical alloying (MA), diffusion bonding, friction stir processing (FSP), and so on. ...
    Article
    Full-text available
    Aluminum (Al)-based composites are on increasing usage in sectors like ground transportation, aerospace, sports, and infrastructure because of the improved properties such as high strength to weight ratio, corrosion, fatigue, and wear resistance. Several applications involving dynamic contact stresses require excellent wear and frictional performance for improved life. Nanocomposites are found to perform exceedingly better than microcomposites and alloys in several lab scale tribological investigations carried out so far in the last decade. In this article, an attempt is made to review those published reports about dry sliding tribological behavior of particulate-reinforced Al nanocomposites. Wear and friction being system properties are found to get influenced by intrinsic factors such as reinforcement, fabrication method, microstructure; extrinsic parameters like load, speed, contact conditions and the system generated in situ tribolayer all being interrelated.
  • ... Particle-reinforced metal matrix composites exhibit the properties of both the ductile metal matrix and the functional ceramic particles incorporated within the matrix. Hence, they are suitable for use in a range of applications, owing to their higher stiffness, improved strength, which is accompanied by a marginal loss in ductility, and greater wear resistance as compared with those of the unreinforced metal [17][18][19]. In particular, composites based on high-energy-absorbing transformation-induced plasticity (TRIP)/twinning-induced plasticity steels and transformable zirconia (ZrO 2 ) particles show great potential [20][21][22][23]. ...
    Article
    Full-text available
    The ability to fabricate complex graded structures would be a significant step towards the manufacturing of material systems with properties tailored to individual applications. While powder metallurgy has had some success in this regard, it requires that the semi-finished products be exactly similar to the final component. However, it is significantly cheaper to produce simple, semi-finished products and then join them to form complex components with the desired graded structure through powder forging and simultaneous compaction. It is also essential that the graded structure of the semi-finished products is retained during the forming process. In this study, pre-sintered cylindrical semi-finished products consisting of identical homogeneous layers as well as graded components consisting of non-identical homogeneous layers were joined using powder forging at 1100 °C. The microstructures and densities as well as the mechanical properties of the final components were investigated. It was observed that, upon compaction, the components formed solid structures, in which the reinforcing ZrO2 particles were completely integrated within the transformation-induced plasticity steel matrix. Finally, it was confirmed that the graded structure of the semi-finished products was retained in the final components.
  • ... These processes are characterized by high productivity and ideal for making parts close to the complex geometry of a range of materials, increasing the use of materials, and minimizing or eliminating secondary processes such as machining. Common secondary processes of components made by liquid metal processing may lead to additional manufacturing steps that have significant cost and waste impacts [24]. However, powder metallurgy processing has obtained more attention with the advantages offered by comparison with casting and forging. ...
  • ... The interest in metal matrix composite (MMCs) has been growing in recent years due to their improved mechanical properties at less budget. That is the reason why MMCs are attracting more attention in several applications in the fields, including sports, automotive and aerospace [1,2]. The RM material is a reinforcement material that is extracted from the bauxite by Bayer's process in the making of alumina. ...
    Article
    Full-text available
    TG and DSC analyses were performed to study thermal stability and specific heat capacity of red mud (RM) particle reinforced Al5083 alloy matrix composites. Metal matrix composites of different weight percentages of RM were blended by stir casting. The composites were processed by equi-channel angular extrusion using a die with an angle of 105° between channels and 30° at the outer curvature. The structural and mechanical behaviors of composites processed by ECAE were evaluated by SEM and hardness studies. Thermal analysis of composites before and after ECAP was performed by using DSC and TG–DTA. From the TG analysis, it was observed that the mass loss of the composites reduced with an increase in RM fraction. Thermal stability before ECAP was observed high up to a temperature of 250 °C and after ECAP high thermal stability retained up to a temperature of 350 °C. It was also observed that at higher fractions of RM, enthalpy and specific heat capacity of composites significantly reduced due to the reduction in the enrichment of RM particles with a matrix material of the composite.
  • ... For instance, silicon carbide (SiC) particle-reinforced aluminum (Al) matrix (SiCp/Al) composites are advanced light-weight materials, in which light aluminum alloys are reinforced by dispersed hard SiC particles. SiCp/Al composites have been widely used in fields of aerospace, automotive, optical instruments and electronic engineering, due to their high strength, high wear resistance, high stiffness and high weight savings [1][2][3][4][5]. While flaws such as voids and particle agglomeration are inevitably generated in the powder metallurgy processes and following mechanical shaping processes, pre-existing surface and internal flaws have a strong impact on the performance of SiCp/Al-based components. ...
    Article
    Full-text available
    While particulate-reinforced metal matrix composites are composed of two phase materials with dramatically different physical and mechanical properties, sound wave-particle interactions play an important role in their ultrasonic inspection tests. In the present work, we investigate the sound wave-particle interactions in silicon carbide (SiC) particle reinforced aluminum (Al) matrix composites under pulse-echo mode ultrasonic inspection by means of finite element simulations. Be consistent with experimentally observed real microstructures, simulated SiC particles have polygon shapes and are randomly dispersed in the Al matrix. In particular, the sound wave-particle interactions are revealed, and their correlations with the A-scan signals are investigated. Furthermore, the effects of extrinsic pulse frequency and intrinsic SiC particle size on the ultrasonic inspection of the composites are addressed. Simulation results indicate that the interference of sound waves with heterogeneous SiC particles leads to more pronounced deflection, scattering and conversion of sound waves than the pure Al matrix, which in turn result in higher attenuation of sound waves in SiCp/Al composites. It is also found that the sound wave-particle interactions have a strong dependence on both pulse frequency and particle size.
  • ... 1 Developments in the field of high-performance materials are of increasing importance. 2 Aluminum matrix composites (AMCs) containing lighter reinforcements are amongst the established and proven composites for use in specialized applications. 3 Among emerging lightweight nanoreinforcements, graphene is leading the race due to its exceptional properties in terms of stiffness and high thermal and electrical conductivity. ...
    Article
    Full-text available
    Aluminium matrix composites with high specific strength are attracting attention for use in automobile and aerospace applications. Graphene nano-platelets (GNPs) were added in 0.1, 0.5, and 1 weight fractions to an Al6061 matrix. Spark plasma sintering was used with a combination of solution sonication and ball milling to disperse the GNPs in the Al6061 matrix. The evolution of the microstructure was studied using optical and scanning electron microscopy. The uniformity of the GNP distribution is discussed in light of selected ball milling parameters. Electron backscattered diffraction analysis was used to measure the grain size and misorientation. X-ray diffraction analysis and transmission electron microscopy revealed neat and clean interfaces between the matrix and GNPs. Hardness and tensile testing revealed a considerable increment in the strength of the final composite after addition of GNPs. Traces of GNP clusters were found in the 1 wt.% composite as well as premature failure at lower strain due to the insufficient load transfer capability of the Al6061-T6 matrix. An illustrative two-dimensional model was developed to explain the load transfer behavior and the deterioration of the mechanical properties.
  • ... Composites with these potential for extensive application leads to large economy savings, also reducing the environmental pollution [1]. Conventionally used monolithic materials always faced the challenge to achieve desirable combinations of properties like strength, stiffness and density [2]. Design and development of Metal Matrix Composites (MMCs) through proper processing methods, reinforcements, machining, testing and analysis leads to enhanced hardness, wear performance, and corrosion resistance compared to pure metal or alloy [3]. ...
    Article
    Full-text available
    The functional grade composite Cu-11Ni-4Si/10wt.%TiC along with Cu11Ni-4Si alloy was stir cast, followed by horizontal-centrifuge cast technique. Cast sample was prepared at a dimension Φout100 x Φin85 x 100 mm. A comparative analysis for non-lubricated slide tribology at inner wall zone (1-5 mm), middle wall zone (5-10 mm) and outer wall zone (10- 14 mm) of composites and alloy, was performed utilizing pin-on-disc tribometer. Observed a proportional raise in wear and friction with rise in applied loads and slid distances. For alloy and composite, a slight decline in wear was seen at medium velocity; showing a gradual deduction in friction with rise in slid velocity, while alloy wear showed a linear growth. Rate of increase in wear response with respect to change in distance was less prominent, compared to its response with load. Worn surfaces analysis of composite using Scanning Electron Microscope showed the presence of Mechanically Mixed Layers, which reduced friction at higher slid velocities resulting in lower wear. The phase formations and presence of oxides were confirmed by X-ray diffraction (XRD) and Energy dispersive spectrometers (EDS) results respectively
  • ... In addition, with careful composition control, they can also exhibit high thermal conductivity, high electric conductivity, good dimensional stability, high damping capacity, and excellent wear resistance [2]. To note that extensive research conducted on MMCs in past four decades has enabled to overcome some challenging technical issues such as cost-effective processing, material design, characterization and matrix-reinforcement interfacial control [3,4]. Therefore, MMCs are being more frequently used in military, ground transportation, aerospace, electronics and even some recreational and infrastructure industries. ...
    Article
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    Hybrid metal matrix composites (MMCs) exhibit superior overall mechanical and functional response when compared to their conventional counterparts and as a result have greater potential to be widely used for structural engineering and functional device applications. This review focuses on the recent developments in the fabrication techniques and properties characterization of Al, Mg, Ti, Cu, Fe/steel and Ni matrix composites containing hybrid reinforcements. The hybrid reinforcements are classified according to different types, shapes and sizes. Novel processing techniques proposed for achieving homogeneous distribution of hybrid reinforcements and forming special structures are critically reviewed. The mechanical properties of various matrix systems are summarized and analyzed, while the strengthening mechanisms triggered by hybrid reinforcements are discussed. Meanwhile, a prediction model for yield strength of hybrid MMCs is also proposed. The effects of hybrid reinforcements and fabrication conditions on functional properties, including tribological, thermal, and electrical properties, of the hybrid composites are also described systematically. Finally, future work for promoting further development of this field is also addressed.
  • ... Crystalline materials, such as metallic crystals and atomic crystals, can have a broad niche of applications for their distinctive properties. For example, aluminum (Al) is a typical and important metallic crystal that is often used as the base material in many essential parts in spacecraft [1][2][3][4], automobiles, and electronics such as batteries and triboelectric nanogenerators [5,6]. This can be attributed to the high performance, good utility, and relatively low cost of aluminum. ...
    Article
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    Friction behavior at fretting interfaces is of fundamental interest in tribology and is important in material applications. However, friction has contact intervals, which can accurately determine the friction characteristics of a material; however, this has not been thoroughly investigated. Moreover, the fretting process with regard to different interfacial configurations have also not been systematically evaluated. To bridge these research gaps, molecular dynamics (MD) simulations on Al-Al, diamond-diamond, and diamond-silicon fretting interfaces were performed while considering bidirectional forces. This paper also proposes new energy theories, bonding principles, nanoscale friction laws, and wear rate analyses. With these models, semi-quantitative analyses of coefficient of friction (CoF) were made and simulation outcomes were examined. The results show that the differences in the hardness, stiffness modulus, and the material configuration have a considerable influence on the fretting process. This can potentially lead to the force generated during friction contact intervals along with changes in the CoF. The effect of surface separation can be of great significance in predicting the fretting process, selecting the material, and for optimization.
  • ... Metal matrix composites (MMCs) are an important engineering material required in this current scenario for many industrial applications such as structural, marine, aerospace, and automobile. The consideration and preference given to MMCs are becoming increased owing to their higher mechanical properties, namely strength-to-weight ratio at both room temperature and high temperature, fatigue resistance and tribological properties (Rosso, 2006;Miracle, 2005;Kaczmar et al., 2000). Particulates, whiskers, and fibers are the various categories of reinforcements used to improve the properties of MMCs. ...
    Chapter
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    Accumulative roll bonding (ARB) is a popular severe plastic deformation method which was used to produce ultrafine grain materials and bimetallic composite strips. ARB was discoved to produce metal matrix composites a decade ago by incorporating reinforcement particles between the sheets prior to roll bonding. The severe deformation and the plasticized material flow effectively mix the reinforcement particles and produce a homogenous dispersion in the metallic matrix. Since the temperature during ARB is insufficient to melt the matrix material, all solidification related issues such as segregation, cluster formation, decomposition of reinforcement particle and net work of pores are completely avoided. ARB is a sound method to produce high strength MMCs compared to all conventionally adopted casting routes. The process provides excellent interfacial bonding between the metallic matrix and the reinforcement without any kind of diffusion or reaction.ARB is not affected by the physical or chemical properties of reinforcement particles. This chapter presents the development of various metallic based MMCs using ARB since its inception. The influence of process parameters such as rolling speed, temperature and number of passes on the misstructure and the mechanical properties are discussed. The strengthening mechanisms of MMCs produced by ARBs are explored.
  • ... Ceramic-reinforced metal matrix composites (MMCs) consist of a ductile metal matrix and a reinforcing ceramic phase, offering a combination of beneficial properties from both phases. The result is often a high specific strength/stiffness, low co-efficient of thermal expansion, improved wear resistance over the unreinforced metal matrix and good fatigue/fracture properties [1,2]. The ability of the reinforcing phase to improve the properties of the metal matrix is highly dependent on its composition, distribution, morphology and volume fraction. ...
    Article
    Ceramic-reinforced metal matrix composites (MMCs) display beneficial properties owing to their combination of ceramic and metal phases. However, the properties are highly dependent on the reinforcing phase composition, volume fraction and morphology. Continuous fiber or network reinforcement morphologies are difficult and expensive to manufacture, and the often-used discontinuous particle or whisker reinforcement morphologies result in less effective properties. Here, we demonstrate the formation of a co-continuous ceramic-reinforced metal matrix composite using solid-state processing. Binder jet additive manufacturing (BJAM) was used to print a nickel superalloy part followed by post-processing via reactive sintering to form a continuous carbide reinforcing phase at the particle boundaries. The kinetics of reinforcement formation are investigated in order to develop a relationship between reactive sintering time, temperature and powder composition on the reinforcing phase thickness and volume fraction. To evaluate performance, the wear resistance of the reinforced BJAM alloy 625 MMC was compared to unreinforced BJAM alloy 625, demonstrating a 64% decrease in the specific wear rate under abrasive wear conditions.
  • ... Therefore, MMCs are most sought after in several industries to substitute components produced using conventional monolithic alloys. MMCs help to improve the performance of industrial components without invoking additional weight into the system (Miracle, 2005;Sidhu et al., 2016;Lloyd, 1994;Kaczmar et al., 2000). ...
    Chapter
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    The widely accepted casting routes to produce metal matrix composites (MMCs) presented lot of challenges and defects which include inhomogeneous dispersion, interfacial reaction, porosity and poor wettablily. Friction stir processing (FSP) has become a popular method to produce bulk and surface MMCs. FSP was developed based on the working principles of friction stir welding. FSP overcomes the setbacks of casting routes. The physical and chemical properties of the reinforcement particles do not have significant effect on the process and the final dispersion in the matrix. FSP relies on severe plastic deformation and mechanical stirring action of the rotating tool to produce MMCs. It is possible to obtain homogenously dispersed particles with superior interfacial bonding between the matrix and the reinforcement at optimized processing conditions. The solid-state nature of the process avoids solidification related issues and alleviates possible interfacial reaction. This chapter presents an overview of producing MMCs having different metallic matrix and reinforcement using FSP. The role of process parameters and tool design on the microstructure and mechanical properties are surveyed.
  • ... Metal matrix composites (MMCs) are applied widely in aero craft [1], automotive [2], aviation [3], infrastructure industries [4], electronic packing [5], thermal management equipments [6] and many more due to their high strength-to-weight ratio, elastic modulus, specific stiffness, thermal conductivity, electrical conductivity, etc. With ample applications, it is important to study the properties of metal matrix composites. ...
    Article
    Full-text available
    Particulate reinforced metal matrix composites (PRMMC) are the most promising alternative for applications where the combination of high strength, elastic modulus, specific stiffness, strength-to-weight ratio and ductility is essential. Experimental investigation does not provide insightful information about microstructural aspects affecting the mechanical behavior of PRMMC, while the micromechanical methods can describe effectively. This paper presents the review on various analytical and computational micromechanical methods to evaluate the mechanical properties of particulate reinforced metal matrix composites. The effects of particle size, shape and orientation and interface strength on the mechanical behavior are presented. Stress–strain relationships, damage evolution, elastic and plastic deformations are also described. Computational micromechanical methods were found to provide better estimate of properties than analytical micromechanical methods. The order of preference among computational micromechanical methods is serial sectioning method, statistical synthetic method, multi-cell method, 2D real microstructure method and unit-cell method. However, serial sectioning method is highly expensive and demands lot of experimental and computational resources while the statistical synthetic method is economical and doesn’t require many resources. Therefore, statistical synthetic method can be a better choice for computational micromechanics of particulate reinforced metal matrix composites to evaluate the mechanical behavior without experimentation.
  • ... Aluminum (Al) and its alloys have long been the preferred choice in weight critical applications in the defense, automotive, sports, and aerospace sectors owing to their exceptional physical, mechanical, and thermal properties such as lightweight, low cost, high specific strength, high specific modulus, and low coefficient of thermal expansion [1]. Particle reinforced aluminum metal matrix composites (AMMCs) have been extensively researched in the past two decades in view of replacing monolithic aluminum alloys to realize enhanced durability [2][3][4][5][6][7][8]. Ceramic materials such as SiC, Al 2 O 3 , BN, and TiC amongst others are often used as the reinforcement phases for developing Al-based composites [9][10][11][12]. ...
    Article
    Full-text available
    In the present study, Ni50Ti50 (NiTi) particle reinforced aluminum nanocomposites were fabricated using microwave sintering and subsequently hot extrusion. The effect of NiTi (0, 0.5, 1.0, and 1.5 vol %) content on the microstructural, mechanical, thermal, and damping properties of the extruded Al-NiTi nanocomposites was studied. Compared to the unreinforced aluminum, hardness, ultimate compression/tensile strength and yield strength increased by 105%, 46%, 45%, and 41% while elongation and coefficient of thermal expansion (CTE) decreased by 49% and 22%, respectively. The fabricated Al-1.5 NiTi nanocomposite exhibited significantly higher damping capacity (3.23 × 10−4) and elastic modulus (78.48 ± 0.008 GPa) when compared to pure Al.
  • ... The application of metal matrix composites (MMCs) is common in industry [1][2][3][4]. Composites based on light metal alloys (aluminum, magnesium) are used in automotive and aerospace industries owing to their low density and simple manufacturing methods [5][6][7]. Composites based on nickel characterized by high-temperature creep and corrosion resistance are broadly used in space technology and aviation [8,9]. ...
    Article
    Full-text available
    Silver, silver alloys, and composites with silver matrix are used mainly as electric contacts, circuit-breakers, and slide bearings. Contacts working conditions require as high as possible thermal and electrical conductivity, wear resistance during electric arc work, low susceptibility to tacking, and chemical stability. Unreinforced silver alloys do not meet those expectations, hence increasing interest in metal matrix composites. Reinforcing with ceramic particles improves tribological wear resistance and minimizes formability of silver alloys. At the same time, introduction of ceramic particles decreases thermal and electrical conductivity. In this paper, manufacturing method of silver-based composites reinforced with particles Al2O3, SiC, and glassy carbon was described. Composites were subjected to differential thermal analysis. Furthermore, thermal diffusivity measurements using laser flash method, as well as measurements of linear thermal expansion coefficient using dilatometric method were performed in order to determine heat conductivity of the prepared composites.
  • ... Aluminium is the most commonly used matrix for the metal matrix composites (MMCs) as a result of several beneficial physical and mechanical properties [1][2][3][4]. The alloys are quite appealing due to their low density, their capability to be strengthened by precipitation, high thermal and electrical conductivity, their good corrosion resistance and their high damping Nanotechnology Applications in Africa: Opportunities and Constraints IOP Conf. ...
  • ... Metal-ceramic composites have been widely applied in industries, like aerospace, automotive, and in many others [1]. In [2], this is explained by their high ratio of strength to mass and specific stiffness as well as excellent thermal conductivity and excellent wear resistance. ...
    Article
    Full-text available
    Copper–alumina composites of the interpenetrating networks type are interesting materials for many applications because of their properties. On the base of preliminary investigations and practical works, in order to obtain a material with high resistance to friction wear as well as good dissipation of heat generated during work, it was decided that a developed material would be prepared on the base of the Cu–Al2O3 composite, with a graded composition. In this paper, we present the developed method of manufacturing dense copper–alumina FGMs, using ceramic preform with a graded porosity infiltrated with molten copper. The article also presents the full characterization of the obtained materials and mainly the impact of microstructure on the useful properties. The produced gradient material of a Cu–Al2O3 brake disk underwent tribological tests under conditions resembling real conditions. These disks also went through a series of abrasive wear trials at different operation stages. In comparison with the reference material (i.e., grey cast iron), the obtained gradient materials are characterized by a lower degree of wear when retaining a similar coefficient of friction value due to the ceramic phase addition. Additionally, it was found that using the copper-based gradient material guarantees faster heat dissipation from the contact area.
  • ... Particle-reinforced metal matrix composites exhibit the properties of both the ductile metal matrix and the functional ceramic particles incorporated within the matrix. Hence, they are suitable for use in a range of applications, owing to their higher stiffness, improved strength, which is accompanied by a marginal loss in ductility, and greater wear resistance as compared with those of the unreinforced metal [17][18][19]. In particular, composites based on high-energy-absorbing transformation-induced plasticity (TRIP)/twinning-induced plasticity steels and transformable zirconia (ZrO 2 ) particles show great potential [20][21][22][23]. ...
    Article
    Full-text available
    The ability to fabricate complex graded structures would be a significant step towards the manufacturing of material systems with properties tailored to individual applications. While powder metallurgy has had some success in this regard, it requires that the semi-finished products be exactly similar to the final component. However, it is significantly cheaper to produce simple, semi-finished products and then join them to form complex components with the desired graded structure through powder forging and simultaneous compaction. It is also essential that the graded structure of the semi-finished products is retained during the forming process. In this study, pre-sintered cylindrical semi-finished products consisting of identical homogeneous layers as well as graded components consisting of non-identical homogeneous layers were joined using powder forging at 1100 �C. The microstructures and densities as well as the mechanical properties of the final components were investigated. It was observed that, upon compaction, the components formed solid structures, in which the reinforcing ZrO2 particles were completely integrated within the transformation-induced plasticity steel matrix. Finally, it was confirmed that the graded structure of the semi-finished products was retained in the final components.
  • ... AMMCs have become the major part of current era materials and are considered to be an excellent light-weight alternative in the automobile, aerospace and marine components. The high specific strength, excellent machinability, high stiffness and superior surface properties are some of the factors responsible for the widespread use of aluminium composites [1][2]. However, the economical fabrication of aluminium composite with the desired properties has always been a major challenge for the industrial sector. ...
  • ... Aerospace 2020, 7, 77 2 of 38 carbides (e.g., WC, SiC, B4C, and TiC), oxides (e.g., Fe3O4, ZrO2, and Al2O3), nitrides (e.g., ZrN, Si3N4, TiN), borides (e.g., TiB, ZrB2, TiB2, WB) and different forms of carbon (e.g., graphite, carbon nanotubes (CNTs), graphene) [3][4][5][6][7][8] have been employed in the literature to fabricate MMCs. Given the higher specific strength (strength-to-weight ratio) and desired intrinsic properties, aluminum matrix composites (AMCs) and titanium matrix composites (TMCs) are considered as superseded candidates for the automotive and aerospace industries to fill the present technological gaps [9]. ...
    Article
    Full-text available
    Selective laser melting (SLM) is a near-net-shape time- and cost-effective manufacturing technique, which can create strong and efficient components with potential applications in the aerospace industry. To meet the requirements of the growing aerospace industrial demands, lighter materials with enhanced mechanical properties are of the utmost need. Metal matrix composites (MMCs) are extraordinary engineering materials with tailorable properties, bilaterally benefiting from the desired properties of reinforcement and matrix constituents. Among a wide range of MMCs currently available, aluminum matrix composites (AMCs) and titanium matrix composites (TMCs) are highly potential candidates for aerospace applications owing to their outstanding strength-to-weight ratio. However, the feasibility of SLM-fabricated composites utilization in aerospace applications is still challenging. This review addresses the SLM of AMCs/TMCs by considering the processability (densification level) and microstructural evolutions as the most significant factors determining the mechanical properties of the final part. The mechanical properties of fabricated MMCs are assessed in terms of hardness, tensile/compressive strength, ductility, and wear resistance, and are compared to their monolithic states. The knowledge gained from process–microstructure–mechanical properties relationship investigations can pave the way to make the existing materials better and invent new materials compatible with growing aerospace industrial demands.
  • Article
    Almost fully dense nickel‐titanium carbide composite coatings with varied titanium carbide content were deposited on 45 carbon steel by laser cladding. High content of titanium carbide particles up to 50 wt.% with bimodal microstructure could be homogeneously distributed in the nickel based matrix. Due to the presence of the harder nickel‐titanium carbide composite coating on the 45 carbon steel, the surface hardness and wear properties were significantly improved. The Vickers hardness (HV 3) increased from about 260 HV 3 for the 45 carbon steel to 300 HV 3 – 360 HV 3 for nickel based composite coating containing 30 wt.% titanium carbide and 550 HV 3 – 680 HV 3 for nickel based composite coating containing 50 wt.% titanium carbide composite coating, respectively. The coefficient of friction and volume wear rate was reduced down to 0.41×10⁻⁶ mm³ N⁻¹ m⁻¹ and 9.3×10⁻⁶ mm³ N⁻¹ ⋅ m⁻¹ when a nickel based composite coating containing 50 wt.% titanium carbide was coated on the 45 carbon steel, respectively. The enhanced wear performance of the composite coating was due to presence of harder nickel‐titanium carbide composite coating and formation of varied soft and lubricant metal oxides consisting of mainly titanium oxides and minor iron and nickel oxides.
  • Article
    In this work, two copper metal matrix composites (MMCs) reinforced with 20 wt.% of Ti(C,N) or Ti2AlN particles were studied. The reinforcement particles were synthesized by flash sintering under 2 bar nitrogen atmosphere causing an SHS reaction ignited by electrical current. This reaction led to produce TiC0.7N0.3 solid solution for the MMC1 reinforcement and Ti2AlN, TiN, and Ti3Al titanium aluminide for the MMC2 reinforcement. Both MMCs were densified by liquid phase sintering. The structural characterization was performed by XRD analysis while the morphology and chemical element distribution of both MMCs were analyzed by SEM and EDS. The structure of the two MMCs was relatively dense and showed good wettability. The mechanical and tribological behavior of MMCs evaluated by nanoindentation and wear testing reveals that the addition of 20 wt.% of reinforcement considerably improves the properties of copper matrix. Indeed, the MMC1 proved to be 3 times harder and 10 times more wear-resistant than the MMC2 composite.
  • Article
    Numerous research studies have been done on ultra-fine grained (UFG) aluminum and aluminum-based composites materials due to their higher tensile strength in comparison with coarse-grained (CG) bulks. However, the relationship between the mechanical behavior and dry sliding wear performance of ultra-fine grained Al5083-based boron carbide-reinforced trimodal composite bulks at room and high temperatures have been neglected. Furthermore, the effect of temperature rise on these properties seems critical since these materials have been used in several working and operating conditions. In the present paper, it is intended to study the impact of temperature rise on the mechanical behavior and wear resistance of ultra-fine grained Al5083-5wt%B4C trimodal composite bulks. Results revealed that increasing the temperature to 200 °C, did not have any significant effect on the hardness and strength of the Al5083-5wt%B4C bulk. However, significant changes occurred in the hardness and wear resistance of the composite samples by adding Al5083 coarse grains. In this case, severe plastic deformation and surface damage occurred in the Al5083-5wt%B4C-50%CG sample and the wear rate reached 9.7 × 10–7(mm3/m–N).
  • Article
    Metal matrix composite is made of non-metallic reinforcements (usually ceramic) in metal matrices that are widely used in various industries, including aerospace and automotive. Two main components of metal matrix composite are the matrix (base metal) and the reinforcing particles that tend to increase the hardness of the workpart. The production and machining of such materials are hard and costly. However, due to their excellent mechanical properties such as high strength to weight ratio, high hardness and rigidity, corrosion resistance, abrasion resistance, and low thermal coefficient, their applications are still growing in various aspects. One major division of metal matrix composite is aluminum metal matrix composite with ceramics particulate reinforcement such as silicon carbide and alumina. According to review of literature, a low volume of information was found in terms of machinability of specific grades of aluminum composite (A356-10% silicon carbide) under various lubrication modes. Therefore, in the course of this study, several blocks of aluminum metal matrix composite (A356) reinforced with 10% silicon carbide elements were used under dry, minimum quantity lubrication and wet milling operation. The maximum flank wear, tool wear modes, as well as the average surface roughness were recorded and were subsequently studied as the machining performance attributes. The use of lubricants in both minimum quantity lubrication and wet modes led to reduced tool wear as compared with readings made under dry mode. However, under similar experimental conditions, no significant improvement was observed on the average surface roughness values.
  • Chapter
    Full-text available
    The effect of various input EDM parameters on the volume and dimensional features of channels produced on AA6061-4%B4C composites was studied. The composite material specimens were prepared by liquid melt stirring process. The sinker EDM was used to machine the channels on these composites. Taguchi L-9 (Design of Experiments) was used to plan the EDM experimentation. The ‘I’ (discharge current), ‘T-on’ (pulse-on time), and ‘T-off’ (pulse-off time) were considered as input conditions. Each of these input parameters was varied at three levels. The volume of the channel obtained after EDM was estimated by developing the CAD-based geometric model. In addition to volume, various geometrical features such as taper, overcut, and the difference in depth at the entrance and exit of each channel were considered as output responses. The regression analysis and the ANOVA were performed for all responses. A set of optimum EDM input parameter levels were identified for a maximum of volume and minimum of taper, overcut, and the difference in depth values. Results showed that the volume was found to be maximum at higher ‘I’ and lower ‘T-on’ conditions. It was observed that there is a considerable difference in the taper and overcut values in the entrance and exit portions for the same channel. Both the ‘I’ and the ‘T-on’ were found to be the influencing parameters with decreasing order of their percentage contribution affecting all the output responses. The reasons were discussed in detail for all the conclusions arrived in the present work.
  • Article
    This manuscript investigates the Fabrication and Microstructure of Automotive Brake Rotor Made of AlSi-SiC Composites. This work is oriented toward fabrication of automotive brake rotors from Al-9Si and Al-12Si reinforced with 10 and 20% SiC particles using stir-casting method. The brake rotors were subjected to heat treatment. Aging behavior showed that hardness increased with the addition of SiC reinforcements by 104%, comparing to solution treatment condition. Also, the addition of SiC particles accelerates formation of precipitates. Microstructure of brake rotors made of composite revealed uniform distribution of SiC particles, primary phase (⍺-Al) and modified eutectic Si. EDX analysis showed the presence of Al, Mg and O at the interface between matrix and SiC particles.
  • Article
    Full-text available
    Al–7Si, Al–7Si–4Zn, Al–7Si–4Zn–3Cu alloys were produced by permanent mold casting method to investigate the effects of copper and zinc additions on the machinability properties of Al–7Si alloy. The structural and mechanical properties of the produced alloys were investigated with conventional methods. Machinability properties of these alloys were determined by turning, and they were associated with structural and mechanical properties of the alloys. Machinability experiments were carried out in CNC vertical machining center under dry cutting conditions using uncoated carbide drill and constant cutting speed (120 m/min), feed (0.15 mm/rev) and depth of cut (15 mm) values. The microstructure of Al–7Si binary alloy was observed to be composed of aluminum-rich α phase, primary silicon crystals and eutectic Al–Si phase. The addition of 4% Zn to the Al–7Si alloy did not form a different phase in the microstructure. However, Al2Cu intermetallic phase was formed by addition of 3% Cu. While the hardness and tensile strength of the alloy increased, elongation to fracture significantly reduced. As a result of machinability experiments, it was observed that the minimum thrust force and surface roughness occurred in Al–7Si–4Zn–3Cu alloy, while the maximum built-up edge was observed during drilling of Al–7Si and Al–7Si–4Zn alloys. Microhardness value of machined surface in Al–7Si alloy was found to be the minimum while the maximum Al–7Si–4Zn–3Cu alloy was observed.
  • Chapter
    In this work, pure aluminium and NiTi is used as matrix and reinforcement to fabricate a smart composite. To get an improved mechanical property, primarily the powder metallurgy process parameters are optimized, and the best processing parameters are used for the fabrication of composites materials and subsequently the composite is used for machining studies. Abrasive Water Jet Machining (AWJM) process is used to study the machinability characteristics of the Al- NiTi smart composites. To study the effect of AWJM parameters on Al-NiTi composites, the following control variables identified are Transverse Speed (TS), Applied Pressure (AP), Standoff Distance (SoD), % Wt. of reinforcements (wt%), Abrasive Size (AS). The output indices are Surface Roughness (Ra) and Kerf Angle (Ka). The experiments are designed and conducted based on the design of experiment. Further, it describes the effectiveness of the hybrid algorithm in predicting and optimizing the Abrasive Water Jet Machining (AWJM) parameters. Grey Relational Analysis (GRA) is used as a feature selection and optimizing tool. The result of feature selection by GRA–Entropy, reveals that the most influencing control variables are ranked in the order as AS, AP, TS, wt% and SoD. Modelling of AWJM process is done by Support Vector Machine algorithm (SVM), and the performance of the model is compared with SVM hybrid models. A hybrid model is developed with the concept of Differential Evolutionary algorithm (DE) and Entropy. Hybrid SVM–Entropy model displayed increased prediction performance by 37.8% compared to the SVM model. GRA–SVM–Entropy hybrid model is compared with the SVM model, it is found that the prediction performance of the GRA–SVM–Entropy hybrid model increased by 49.1%. It is found from the GRA–Entropy method; the optimal conditions are A2, B1, C1, D3, and E1.
  • Article
    A simple yet innovative approach has been made through a powder metallurgy route for the synthesis of aluminum–graphene (Al–Gr) composite materials for commercially viable solar thermal collectors. The Al–Gr composite (with 1 wt. % of graphene filler content) recorded an enhanced thermal conductivity of ∼280 W/mK, which is higher than that of pristine Al (∼124 W/mK), at room temperature. It has also been found that the prepared composite has a lower coefficient of thermal expansion. The structures and morphologies of the composites have been investigated in detail with the help of X-ray diffraction technique, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, etc. Furthermore, the density measurements showed that the composites retain ∼97.5% of the density of pristine aluminum even after the sintering treatment. X-ray micro-computed tomography revealed the structural integrity and non-porous nature of the samples, free from any defects and deformations. The thermal fusing of Al-based composite materials at 630 °C is found to be satisfactory with the required strength, and the composites showed at least ∼125% increase in the thermal conductivity than that of pristine Al. These results suggest that the Al–Gr composites can be deployed as solar thermal collectors and heat sink materials for thermal dissipation.
  • Article
    The aim of the present study is to investigate the structural, wear and thermal behaviour of Cu–Al 2 O 3 –graphite hybrid metal matrix composites. Copper matrix composites with Al 2 O 3 –graphite reinforcement (0.5-0.5, 1.0-1.0, 1.5-1.5 and 2.0-2.0 wt%) were prepared by stir casting process. Phase, microstructure, density, hardness, wear, compressive strength and specific heat of prepared samples have been investigated. X-ray diffraction revealed that there is no intermediate phase formation between matrix and reinforcement phase as a result of interfacial bonding between them. Microstructure study shows the uniform distribution of Al 2 O 3 –graphite particles in the Cu-matrix. Density and hardness were found to decrease with increase in reinforcements percentage whereas the compressive strength was found to increase as the amount of reinforcements was increased. Composite containing 2.0 wt% reinforcements showed the maximum resistance to wear. Specific heat was found to increase with addition of reinforcements; however, this increase was very marginal. Structural, wear and thermal properties of these Cu matrix-based hybrid metal matrix composites were found to be dependent on the reinforcements concentration. It is expected that the present composite will be useful for heat exchanger and heat sink applications.
  • Article
    Aiming at the problem of poor corrosion resistance of aluminum alloy drill pipe materials in an alkaline environment, an innovative short basalt fiber/aluminum composite is prepared by vacuum hot‐press sintering technique. Also, the corrosion behavior of the composites is investigated by hydrogen evolution and electrochemical tests. The results show that the corrosion resistance of 7075 aluminum alloy is significantly improved after adding 1.0 wt% short basalt fiber. According to the results of scanning electron microscopy and electrochemical impedance spectroscopy, the main component of basalt fiber, SiO2, reacts with the aluminum matrix to produce a large amount of Al2O3. Meanwhile, Si atoms diffuse into the metal melt. This reaction improves the strength and density of the oxide film of the composite material, thereby improving its corrosion resistance.
  • Article
    Friction stir Processing is an important surface modifying technique to produce composite surface layer. This paper evaluates the effect of tool rotational speed, traverse speed and shoulder diameter on hardness and wear behavior of Al-B4C surface nano composite produced by FSP method. A Five level rotatable central composite design is used to predict the optimum input process parameters to fabricate the sound composite layer. Response surface methodology (RSM) Technique was used for analyzing the relationship between responses and process parameters. The results revealed that the shoulder diameter has more influence on achieving maximum hardness and wear resistance. To study the wear mechanisms, the selected wear worn out samples are analyzed through SEM studies
  • Article
    The microstructure, mechanical properties and tribological behaviors of aluminum matrix composites with different contents of AlFeNiCrCoTi high-entropy alloy (HEA) (4.0, 5.0 and 6.0 wt%) were investigated. The as-cast specimens were analyzed by the scanning electron microscopy and electron probe micro-analysis. The results indicated that flake-like and blocky intermetallic compounds precipitated distributing in α-Al matrix in the solidification when the concentration of HEA was more than 4.0 wt% in pure aluminum. Moreover, as the content of HEA increased, the number of the intermetallic compounds increased. Meanwhile, a new phase formed and it distributed inter-dendrite of α-Al in the solidification, which morphology was rod-shaped and the diameter was less than 200 nm. The area fraction of the nano-phases increased, and the diameter decreased with increasing the addition of HEA in pure aluminum. The tensile test illustrated that the ultimate tensile strength increased firstly and then decreased with the increase of HEA content. When the addition concentration of HEA was 4.0 wt%, the ultimate tensile strength enhanced from 58 to 142 MPa. When 5.0 wt% HEA was added into pure aluminum, the ultimate tensile strength further improved from 142 to 170 MPa. In addition, the elongation decreased from 40.6 to 22.7%. However, when 6.0 wt% HEA was added into pure aluminum, the ultimate tensile strength and elongation reduced to 157 MPa and 18.2%, respectively. The tribological behaviors of aluminum matrix composites were investigated under the condition of seawater. The friction coefficient and wear rate of aluminum matrix composites significantly decreased with the increase of HEA content. Moreover, when the addition level was up to 6.0 wt%, the friction coefficient of aluminum matrix composites decreased by 71.1% from 0.83 to 0.24, and wear rate decreased by 90.8% from 2.48 × 10−9 m3 N−1 m−1 to 2.27 × 10−10 m3 N−1 m−1.
  • Article
    Full-text available
    Additively manufactured copper matrix composites: Heterogeneous microstructures and combined strengthening effects - Heng Ouyang, Ge Wang, Zan Li, Qiang Guo
  • Chapter
    Aluminium matrix composites (AMCs) of 3, 6 and 9% fly ash as reinforcement and aluminium cast alloy (356) as matrix were fabricated using stir casting technique. The effects of wire EDM process parameters on machining of AMCs were investigated using Grey relational analysis. In this study, the input machining parameters such as gap voltage, pulse on time, pulse off time, wire feed and reinforcement percentage are optimized with considerations of multiple performance characteristics of the output parameters of MRR and SR. Optimal process parameters were selected based on Grey relational grades and confirmation experiments were conducted. ANOVA was used to find the contribution of each machining parameter. The results show that pulse on time has the most significant effect for achieving maximum GRG and is followed by gap voltage, wire feed, pulse off time and reinforcement in that order. The WEDM process was improved through this approach.
  • Article
    Corrugated struts as part of lattice structures can lead to novel mechanical behavior by a combination of material and geometrical hardening. The unfolding behavior of such struts offers a potential of large macroscopic straining. However, their ability to be unfolded is impacted by the surface characteristics inherited from the additive manufacturing process. Herein, the unfolding sensitivity to these surface characteristics is evaluated. Corrugated struts with varying surface roughness are produced using a combination of electron beam powder‐bed fusion to produce corrugated samples with different nominal diameters and chemical etching assisted by micro‐computed tomography (CT) to achieve a given final diameter. In situ micro‐CT tensile tests are conducted to track the evolution of the struts morphology under loading. Surface defects play a significant role in the unfolding ability of such struts. They are characterized either by a global roughness or by a local notch depth. A quite broad unfolding dispersion remains for samples with the same level of roughness. A finer description of notch depth and location within the gauge length allows a more accurate prediction of the unfolding ability. A model for predicting the probability of failure during unfolding is presented.
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  • Intermetallic NiAl-based composites with dramatically higher energy absorption capability and damage tolerance have been demonstrated. The approach consisted of incorporating continuous tubular 304 stainless steel toughening regions throughout the majority phase NiAl matrix. To compensate for the increase in density resulting from the 304 stainless steel, B4C particulate was added to the NiAl so that the overall composite density was within 5 pct of the value for monolithic NiAl. The notched Charpy impact energy absorption of the B4C/NiAl/304 stainless steel composites was in the range of 15 to 90 J/cm2, compared to a value of 0.8 J/cm2 for NiAl. The higher energies were measured on samples that deflected the crack front more extensively during failure. A model has been developed that is consistent with the energy absorption values measured during notched impact testing of the composites. Finally, significant room-temperature tensile strains (20 to 35 pct) were achieved due to constrained yielding of the 304 stainless steel, which prevented composite failure after the NiAl regions had cracked.
  • Article
    Understanding materials, their properties and behavior is fundamental to engineering design, and a key application of materials science. Written for all students of engineering, materials science and design, this book describes the procedures for material selection in mechanical design in order to ensure that the most suitable materials for a given application are identified from the full range of materials and section shapes available. Extensively revised for this fourth edition, Materials Selection in Mechanical Design is recognized as one of the leading materials selection texts, and provides a unique and genuinely innovative resource. Features new to this edition. Material property charts now in full color throughout. Significant revisions of chapters on engineering materials, processes and process selection, and selection of material and shape while retaining the book's hallmark structure and subject content. Fully revised chapters on hybrid materials and materials and the environment. Appendix on data and information for engineering materials fully updated. Revised and expanded end-of-chapter exercises and additional worked examplesMaterials are introduced through their properties; materials selection charts (also available on line) capture the important features of all materials, allowing rapid retrieval of information and application of selection techniques. Merit indices, combined with charts, allow optimization of the materials selection process. Sources of material property data are reviewed and approaches to their use are given. Material processing and its influence on the design are discussed. New chapters on environmental issues, industrial engineering and materials design are included, as are new worked examples, exercise materials and a separate, online Instructor's Manual. New case studies have been developed to further illustrate procedures and to add to the practical implementation of the text.
  • Article
    This book has the stated aim of covering the physical and mechanical metallurgy, interfacial physics and mechanics, and processing of metal matrix composites (MMCs). The term metal matrix composites covers particle, short-fiber, and continuous-fiber reinforced metals. The book covers most of the important topics relevant to the mechanical characteristics of MMCs such as load transfer from the matrix to the fiber, plastic deformation of the metal matrix, effect of thermal mismatch between the fiber and the matrix, and microstructural changes in the matrix caused by the presence of reinforcements. Fracture, transport properties, environmental properties, and tribological characteristics of MMCs are dealt with. Analytical treatments of various topics are provided in a very able manner. The last two chapters include practical information on special techniques such as MMC specimen preparation for transmission electron microscopy, etc. and commercial applications of MMCs. What is surprising is that among the applications of MMCs, no mention is made of filamentary superconductors, conventional or high [Tc] ceramic oxide superconductors. This book is a welcome addition to the literature on metal matrix composites. It is suitable for scientists, engineers, and practicing engineers who deal with metal matrix composites. There is a wealth of line diagrams, micrographs, andmore » references to the literature, and there are subject and author indexes.« less
  • Article
    In order to introduce different levels of microstructural heterogeneity into an experimental DRA material, three 6061/SiC/25p DRA extrusions were produced, using established P/M techniques. Each contained F-600 grade SiC particles (median diameter, d50 = 13.4 μm) however, the median matrix particle size was varied in a controlled manner, by careful screening of the 6061-Al powder stock. The range of matrix particle sizes that were chosen (26.4 μm, 42.0 μm and 108.6 μm) introduced increasing levels of spatial heterogeneity into the DRA microstructures, as quantified using the Multi-Scalar Analysis of Area Fractions (MSAAF) technique. The DRA materials were further processed, using FSP, in order to ascertain the effect of FSP on the homogeneity of the as-extruded microstructures. It was found that FSP introduces a significant amount of solid-state mixing which reduces the amount of microstructural spatial heterogeneity, even in the worst DRA specimens. In addition, minitensile tests were carried out on the as-extruded and as-processed DRA materials, and these results are presented in the context of the effects of microstructural heterogeneity on tensile mechanical properties.
  • Article
    Silicon carbide particulate-reinforced aluminum matrix composites with dramatically higher energy absorption capability and damage tolerance have been demonstrated. The approach, referred to as microstructurally toughened composites, consists of segregating the composite into particulate-reinforced regions and continuous ductile toughening regions. Composites consisting of silicon carbide particulate-reinforced 6061 Al (SiCp/6061) with monolithic 6061 and commercially pure (CP) titanium toughening regions were fabricated. As much as an order of magnitude increase in notched Charpy impact energy absorption capability was demonstrated relative to conventional SiCp/6061 composites, with the higher values being associated with those samples that deflected the crack front more extensively during failure. The longitudinal tensile strength of the composites was shown to be independent of the scale of the microstructure or the magnitude of the toughening/reinforced region's interfacial strength. The high impact energy 6061 toughened composites displayed low transverse tensile strength values, while the CP titanium toughened composites simultaneously displayed high energy absorption and high transverse tensile strength. A model was also developed to predict the minimum and maximum energy absorption capability of the composites, as well as provide a quantitative estimate of the composite energy absorption based on the measured crack front deflection length in the failed impact samples.
  • Article
    A novel materials-selection procedure has been developed and implemented in software. The procedure makes use of Materials Selection Charts: a new way of displaying material property data; and performance indices: combinations of material properties which govern performance. Optimisation methods are employed for simultaneous selection of both material and shape.
  • Article
    Ductile phase containing bulk metallic glass composites are prepared via an in situ method by rapid quenching of a homogenous Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 melt. The microstructure of the resulting two phase material is investigated by SEM, X-ray diffraction, and microprobe analysis. The composite material, as well as single phase materials with the corresponding matrix and second phase compositions, are tested in uniaxial tension and compression. Young's Modulus, shear modulus and Poisson ratios are analyzed by ultrasonic sound velocity measurements. The composite material demonstrates strongly improved Charpy impact toughness (by a factor of 2.5 compared to Vitreloy 1) and ductility (average fracture strain up to 8.3% in compression and 5.5% in tension). These remarkable improvements are explained by the effect of the mechanically soft and ductile second phase, which acts stabilizing against shear localization and critical crack propagation.
  • Article
    uent. The major composite classes include or- ganic-matrix composites (OMCs), metal-matrix composites (MMCs), and ceramic-matrix com- posites (CMCs). The term "organic-matrix com- posite" is generally assumed to include two classes of composites: polymer-matrix compos- ites (PMCs) and carbon-matrix composites (commonly referred to as carbon-carbon com- posites). Carbon-matrix composites are typically formed from PMCs by including the extra steps of carbonizing and densifying the original poly- mer matrix. In the research and development community, intermetallic-matrix composites (IMCs) are sometimes listed as a classification that is distinct from MMCs. However, significant commercial applications of IMCs do not yet ex- ist, and in a practical sense these materials do not provide a radically different set of properties relative to MMCs. In each of these systems, the matrix is typically a continuous phase through- out the component.
  • Article
    The creep behavior of dual scale particle strengthened (DSPS) metals containing particles of two different size scales, namely nanometer size dispersoids and reinforcements with typical dimensions in the micrometer to millimeter range, is analyzed theoretically. Based on the concept of thermally activated dislocation detachment from dispersoid particles as rate-controlling mechanism in dispersion hardened matrices, a new creep equation for this advanced material class is developed. Analysis of the model leads to the prediction that creep strength levels far superior to today's best dispersion or reinforcement strengthened high temperature materials can be achieved by using dispersion and reinforcement hardening in combination and following certain design guidelines, related to the selected particle parameters. In particular, it is shown that a volume fraction mix of about 3/4 reinforcements with about 1/4 dispersoids is ideal in many cases provided reinforcements with sufficient aspect ratio and size are selected.
  • Article
    Particle shape effects on the fracture and ductility of a spherical and an angular particulate-reinforced 6061-Al composite containing 20 pct vol Al2O3 were studied using scanning electron microscopy (SEM) fractography and modeled using the finite element method (FEM). The spherical particulate composite exhibited a slightly lower yield strength and work hardening rate but a considerably higher ductility than the angular counterpart. The SEM fractographic examination showed that during tensile deformation, the spherical composite failed through void nucleation and linking in the matrix near the reinforcement/matrix interface, whereas the angular composite failed through particle fracture and matrix ligament rupture. The FEM results indicate that the distinction between the failure modes for these two composites can be attributed to the differences in the development of internal stresses and strains within the composites due to particle shape.
  • Article
    Applications for metal matrix composites (MMCs) have not emerged at the rate needed to justify the development costs. A reason for this may be that material developments have not been adequately linked to identified commercial needs. It is certainly true that some of the expectations raised about the potential offered by MMCs have been misguided. As the MMC business contracts, there is an ever greater need for a systematic method of linking material properties to the needs of engineering designers. This paper presents a methodology for evaluating materials in design, with the aim of linking MMCs to applications. The methodology has two main components: first, the use of performance indices and materials selection charts for specific design goals, to compare existing MMCs with competing materials; and secondly, the conceptual design of new MMC systems guided by those design goals. A selection of case studies illustrates that in mechanical applications the gains in using MMCs are frequently marginal, whereas in design for thermal management and vibration control, the materials can show very substantial improvements in performance. The methodology is general, and could be applied to other material systems. MST/3094
  • Article
    A bulk metallic glass-forming Ti–Cu–Ni–Sn alloy with in situ formed composite microstructure prepared by both centrifugal and injection casting presents more than 6% plastic strain under compressive stress at room temperature. The in situ formed composite contains dendritic hexagonal-close-packed-Ti solid solution precipitates and a few Ti3Sn, β –(Cu, Sn) grains dispersed in a glassy matrix. The composite microstructure can avoid the development of the highly localized shear bands typical for the room-temperature deformation of monolithic glasses. Instead, highly developed shear bands with evident protuberance are observed, resulting in significant yielding and homogeneous plastic deformation over the entire sample.
  • Article
    In order to study the effect of particle morphology on the tensile response of discontinuously-reinforced aluminum (DRA), two P/M 6061/SiC/25p materials were fabricated using established powder blending, compaction and extrusion techniques. One of the materials contained abrasive-grade SiC (F-600) whilst the second material was fabricated using a less angular SiC particulate with a lower aspect ratio, selected to give an overall higher bulk density (HBD) in the as-blended form. Care was taken to ensure that each material contained the same size and volume fraction of SiC particles, and that each material experienced an identical processing route. Mechanical testing was completed at ambient temperature, to measure the effect of particle morphology (F-600 vs. HBD) on both the elastic and plastic tensile response of the DRA. Specimens were tested in as-extruded (F), peak-aged (T6) and over-aged heat treatment (OA) conditions. The DRA produced with the HBD reinforcement consistently showed improved tensile elongation over the DRA containing the F-600 reinforcement, with the most significant effect being observed in the as-extruded (F) condition. The Considère criterion was used to show that different damage mechanisms may be operating in each material. Extensive microstructural and fractographic analyses were also carried out on the as-processed and as-tested specimens, using optical and electron microscopy. The dominant damage and failure mechanisms in each material are discussed in the light of these results.
  • Article
    The effect of SiC volume fraction and particle size on the fatigue behavior of 2080 Al was investigated. Matrix microstructure in the composite and the unreinforced alloy was held relatively constant by the introduction of a deformation stage prior to aging. It was found that increasing volume fraction and decreasing particle size resulted in an increase in fatigue resistance. Mechanisms responsible for this behavior are described in terms of load transfer from the matrix to the high stiffness reinforcement, increasing obstacles for dislocation motion in the form of S’ precipitates, and the decrease in strain localization with decreasing reinforcement interparticle spacing as a result of reduced particle size. Microplasticity was also observed in the composite, in the form of stress-strain hysteresis loops, and is related to stress concentrations at the poles of the reinforcement. Finally, intermetallic inclusions in the matrix acted as fatigue crack initiation sites. The effect of inclusion size and location on fatigue life of the composites is discussed.
  • Article
    A variety of new advanced composite materials are now available that provide great advantages over conventional materials for electronic packaging thermal control, including extremely high thermal conductivities (more than twice that of copper); low tailorable coefficients of thermal expansion; weight savings up to 80 percent; extremely high strength and stiffness; low-cost, net-shape fabrication processes; and cost reductions as high as 65 percent. In addition, composites are in a state of continual development that will provide even greater benefits. This article provides an overview of advanced composites used in thermal management, including properties, applications, and future trends. The focus is on materials having thermal conductivities at least as high as those of aluminum alloys. Future trends and the potential for composites in other aspects of the electronics industry, such as high-speed assembly machine materials of construction, are also examined.
  • Article
    Full-text available
    From the onset of the space era, both organic-matrix and metal-matrix composites (MMCs), with high specific stiffness and near-zero coefficient of thermal expansion (CTE), have been developed for space applications. Of the organic-matrix composites, graphite/epoxy (Gr/Ep) has been used in space for truss elements, bus panels, antennas, wave guides, and parabolic reflectors in the past 30 years. MMCs possess high-temperature capability, high thermal conductivity, low CTE, and high specific stiffness and strength. Those potential benefits generated optimism for MMCs for critical space system applications in the late 1980s.1,2 The purpose of this article is to detail the history, status, and opportunities of MMCs for space applications.
  • Article
    The advancement of metal-matrix composites in the automotive market is still hampered by the low-volume usage of these materials, which is caused by their high cost in comparison with aluminum alloys and, in some cases, by the lack of theoretically predicted properties. Many significant challenges must be met as these materials reach maturity and the technology is scaled-up for automotive-component fabrication. The successful commercialization of metal-matrix composites will ultimately depend on their cost effectiveness for different applications. This requires optimum methods of processing, machining, and recycling, including some very new and advanced forming routes.
  • Article
    This paper presents the results of a study on the effects of matrix microstructure and particle distribution on the fracture of an aluminum alloy metal matrix composite containing 20% by volume SiC particulate. The matrix microstructure was systematically varied by heat treating to either an under- or over-aged condition of equivalent strength, and was characterized using a combination of techniques. Quantitative metallographic techniques were utilized to characterize the material with respect to size, size distribution, and particle clustering, while transmission electron microscopy was utilized to characterize the details of the matrix microstructure in addition to the effects of aging on the character of the particle/matrix interfaces. Fracture experiments were conducted on smooth tensile, notched bend, shortrod toughness, and on specimens designed to permit controlled crack propagation, in an attempt to determine the effects of matrix microstructure and clustered regions on the details of damage accumulation. Large effects of microstructure on the notched properties were obtained with little effect of microstructure on tensile ductility. It is shown that the micromechanisms of fracture are significantly affected by the details of the matrix microstructure, interface character, and degree of clustering in the material. Fracture of the SiC was predominant in the underaged materials, with a preference for failure in the matrix and near the interface in the overaged material. Metallographic and fractographic analyses revealed that clustered regions were preferred sites for damage initiation in both the aging conditions tested, while preliminary results additionally indicate that damage accumulation ahead of a propagating crack also tended to occur in clustered regions.
  • Article
    Thermal stability of nanostructured Al93Fe3Ti2Cr2 alloys prepared via mechanical alloying (MA) starting from elemental powders was investigated using a variety of analytical techniques including modulated differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy coupled with energy dispersive spectrometry and microdiffraction. The results showed that the MA-processed Al93Fe3Ti2Cr2 alloy in the as-milled condition was composed of an Al-based supersaturated solid solution with high internal strains. Release of internal strains, intermetallic precipitation and grain growth occurred upon heating of the MA-processed Al alloy. Nevertheless, grain growth in the MA-processed Al alloy was very limited and fcc-Al grains with sizes in the range of 20 nm were still present in the alloys after exposure to 450 °C (0.77 Tm).
  • Article
    Metal matrix composites made by a powder metallurgy route often exhibit clustering of the reinforcements due to geometrical reasons. The clustering tendency was studied in 2124 Al/30 v/o SiCp composites as a function of relative particle size ratio between the matrix and reinforcement particles. Dry blended composite powders, with different RPS ratios, were vacuum hot-pressed and microstructures were examined to assess the uniformity of the microstructure by measuring the local area fraction of the constituents. It was found that a decrease in RPS ratio resulted in an increase in strength as well as ductility, as a result of improved distribution of the SiCp. The improved response to the homogenisation treatment, observed in the composite with lower RPS ratio, is attributed to the smaller diffusion path length for the alloying element.
  • Article
    Full-text available
    The mechanical properties of composites consisting of an aluminum matrix with 34 and 37 vol.% sub-micron Al2O3 particles were studied in compression for two reinforcement architectures: interconnected and discontinuous. Both the elastic and plastic behaviors of these composites are successfully modeled using a self-consistent approach: the classical self-consistent and the three-phase self-consistent models for the interconnected and discontinuous architectures, respectively. At ambient temperature, an interconnected architecture offers only a modest increase in stiffness and strength over a discontinuous architecture of equal volume fraction. At elevated temperatures (250, 500 and 600 °C), the interconnected reinforcement becomes increasingly more effective at strengthening the composites. However, the relative increase in strength due to interconnectivity can only be exploited at small strains (1–5%) due to the early development of compressive flow instabilities in the interconnected composites. While microstructural damage controls the instability strain of the interconnected composites at ambient temperature, their low strain-hardening coefficient is the main contribution to flow instabilities at elevated temperature.
  • Article
    The tensile behaviour of composites produced by infiltrating ceramic particle beds with high purity (99.99%) At is studied as a function of reinforcement size and chemistry (Al2O3 and B4C). The yield stress is higher in composites containing B4C particles, increasing with decreasing interparticle distance in both composite systems. The flow stress of the composites, when corrected for damage, displays the same dependence on interparticle distance as the yield stress. The overall strain hardening exponent, however, is independent of the microstructural scale. These observations are rationalized based on the theory of geometrically necessary dislocations. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
  • Article
    Particle reinforced composites are produced by infiltrating Al2O3 particle beds with high purity Al (99.99%). These materials feature 40–60 vol. pct reinforcement homogeneously distributed in a pore-free matrix. Their tensile behaviour is studied as a function of reinforcement size and shape. Internal damage, in the form of particle fracture and matrix voiding, occurs from the onset of plastic straining. Its evolution with strain is monitored through changes in (i) stiffness and (ii) peak stress after incremental plastic straining and annealing. The influence of damage on the flow curves of the composites can be accounted for using basic postulates of continuum damage mechanics. Failure strains vary between 2 and 4%, and are a function of the rate of damage accumulation. An expression is derived to predict elongation to failure of damaging materials that fail by tensile instability, which gives good agreement with the experimental observations.
  • Article
    Full-text available
    Results are presented for a ductile metal reinforced bulk metallic glass matrix composite based on glass forming compositions in the Zr-Ti-Cu-Ni-Be system. Primary dendrite growth and solute partitioning in the molten state yields a microstructure consisting of a ductile crystalline Ti-Zr-Nb beta phase, with bcc structure, in a Zr-Ti-Nb-Cu-Ni-Be bulk metallic glass matrix. Under unconstrained mechanical loading organized shear band patterns develop throughout the sample. This results in a dramatic increase in the plastic strain to failure, impact resistance, and toughness of the metallic glass.
  • Article
    Full-text available
    Nanocrystalline metals--with grain sizes of less than 100 nm--have strengths exceeding those of coarse-grained and even alloyed metals, and are thus expected to have many applications. For example, pure nanocrystalline Cu (refs 1-7) has a yield strength in excess of 400 MPa, which is six times higher than that of coarse-grained Cu. But nanocrystalline materials often exhibit low tensile ductility at room temperature, which limits their practical utility. The elongation to failure is typically less than a few per cent; the regime of uniform deformation is even smaller. Here we describe a thermomechanical treatment of Cu that results in a bimodal grain size distribution, with micrometre-sized grains embedded inside a matrix of nanocrystalline and ultrafine (<300 nm) grains. The matrix grains impart high strength, as expected from an extrapolation of the Hall-Petch relationship. Meanwhile, the inhomogeneous microstructure induces strain hardening mechanisms that stabilize the tensile deformation, leading to a high tensile ductility--65% elongation to failure, and 30% uniform elongation. We expect that these results will have implications in the development of tough nanostructured metals for forming operations and high-performance structural applications including microelectromechanical and biomedical systems.