Showing papers on "Metal matrix composite published in 2007"

Novel Nanoparticle‐Reinforced Metal Matrix Composites with Enhanced Mechanical Properties

Abstract: This paper summarizes and reviews the state-of-the-art processing methods, structures and mechanical properties of the metal matrix composites reinforced with ceramic nanoparticles. The metal matrices of nanocomposites involved include aluminum and magnesium. The processing approaches for nanocomposites can be classified into ex-situ and in-situ synthesis routes. The ex-situ ceramic nanoparticles are prone to cluster during composite processing and the properties of materials are lower than the theoretical values. Despite the fact of clustering, ex-situ nanocomposites reinforced with very low loading levels of nanoparticles exhibit higher yield strength and creep resistance than their microcomposite counterparts filled with much higher particulate content. Better dispersion of ceramic nanoparticles in metal matrix can be achieved by using appropriate processing techniques. Consequently, improvements in both the mechanical strength and ductility can be obtained readily in aluminum or magnesium by adding ceramic nanoparticles. Similar beneficial enhancements in mechanical properties are observed for the nanocomposites reinforced with in-situ nanoparticles.

Processing and properties of carbon nanotubes reinforced aluminum composites

Abstract: Carbon nanotubes reinforced aluminum matrix composites were fabricated by isostatic pressing followed hot extrusion techniques. Differential scanning calorimetric, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy has been carried out to examine the reaction condition of nanotubes and aluminum, and to analyze the composites structure. The effects of nanotubes content on mechanical properties of composites were investigated. Experimental results showed that nanotubes are homogeneously distributed in the composites. Some nanotubes act as bridges across cracks, others are pulled-out on fracture surfaces of composites. However, nanotubes react with aluminum and form Al4C3 phases when the temperature is above 656.3 °C. The nanotubes content affects significantly mechanical properties of composites. Meanwhile, the 1.0 wt.% nanotube/2024Al composite is found to exhibit the highest tensile strength and Young's modulus. The maximal increments of tensile strength and Young's modulus of the composite, compared with the 2024Al matrix, are 35.7% and 41.3%, respectively.

Processing and mechanical properties of SiC reinforced cast magnesium matrix composites by stir casting process

Abstract: Elemental Mg and Mg-alloy (AZ91D) based composites reinforced with 15 vol.% silicon carbide (SiC) particulates (average particle size 15 μm and 150 μm) were synthesised by stir casting technique. Particle distribution, particle–matrix interfacial reaction, hardness and mechanical properties in the as cast as well as T4 heat-treated conditions were investigated. The composite materials show uniform distribution of SiC particulates. The average grain size decreases with the presence of SiC particulates and the grain size further decreases as the particle size decreases. The AZ91D alloy composite shows an increase in hardness and elastic modulus compared to monolithic alloys. The improvement in elastic modulus of composite containing 15 μm size SiC particles is significantly higher than the composite with 150 μm size particles. The ultimate tensile strength and ductility of composite materials were reduced compared to unreinforced alloy.

An FEM investigation into the behavior of metal matrix composites: tool-particle interaction during orthogonal cutting

Abstract: An analytical or experimental method is often unable to explore the behavior of a metal matrix composite (MMC) during machining due to the complex deformation and interactions among particles, tool and matrix. This paper investigates the matrix deformation and tool–particle interactions during machining using the finite element method. Based on the geometrical orientations, the interaction between tool and particle reinforcements was categorized into three scenarios: particles along, above and below the cutting path. The development of stress and strain fields in the MMC was analyzed and physical phenomena such as tool wear, particle debonding, displacements and inhomogeneous deformation of matrix material were explored. It was found that tool–particle interaction and stress/strain distributions in the particles/matrix are responsible for particle debonding, surface damage and tool wear during machining of MMC.

Hardness and wear resistance of carbon nanotube reinforced Cu matrix nanocomposites

Abstract: Carbon nanotube (CNT) reinforced Cu matrix (CNT/Cu) nanocomposites are fabricated by a novel fabrication process, named as molecular level process, which involves suspending CNTs in solvent by surface functionalization, mixing Cu ions with CNT suspension, drying, calcination and reduction. The molecular level process produces CNT/Cu nanocomposite powders, in which the CNTs are homogeneously implanted within Cu powders. The nanocomposite powders are consolidated into CNT/Cu nanocomposites by spark plasma sintering. The hardness and sliding wear resistance of CNT/Cu nanocomposite are enhanced by two and three times, respectively, compared to those of Cu matrix. The enhancement of hardness is due to the effect of homogeneous distribution of CNTs in Cu matrix, good bonding at CNT/Cu interfaces and high relative density of nanocomposites. The dispersed CNTs in Cu-matrix nanocomposite gives significantly enhanced wear resistance by retarding the peeling of Cu grains during sliding wear process.

Effects of silicon carbide reinforcement on microstructure and properties of cast Al–Si–Fe/SiC particulate composites

Abstract: The effects of silicon carbide (SiC) particles on the as-cast microstructure and properties of Al–Si–Fe alloy composites produced by double stir-casting method have been studied. A total of 5–25 wt% silicon carbide particles were added. The microstructure of the alloy particulate composites produced was examined, the physical and mechanical properties measured include: densities, porosity, ultimate tensile strength, yield strength, hardness values and impact energy. The results revealed that, addition of silicon carbide reinforcement, increased the hardness values and apparent porosity by 75 and 39%, respectively, and decreased the density and impact energy by 1.08 and 15%, respectively, as the weight percent of silicon carbide increases in the alloy. The yield strength and ultimate tensile strength increased by 26.25 and 25% up to a maximum of 20% silicon carbide addition, respectively. These increases in strength and hardness values are attributed to the distribution of hard and brittle ceramic phases in the ductile metal matrix. The microstructure obtained reveals a dark ceramic and white metal phases, which resulted into increase in the dislocation density at the particles–matrix interfaces. These results show that better properties is achievable by addition of silicon carbide to Al–Si–Fe alloy.

Experimental and numerical studies of the effect of particle size on the deformation behavior of the metal matrix composites

Abstract: By incorporating the Taylor-based nonlocal theory of plasticity, the finite element method (FEM) is applied to investigate the effect of particle size on the deformation behavior of the metal matrix composites. The contributions of various strengthening mechanisms to overall composite strengthening, and the impact of particle size on each mechanism were explicitly evaluated. Both numerical and experimental results indicate that, at a constant particle volume fraction, there is a close relationship between the particle size and the deformation behavior of the composites. The yield strength and plastic work hardening rate of the composites increase with decreasing particle size. The predicted stress–strain behaviors of the composites are qualitative agreement with the experimental results. It is also found that the particle size has a significantly effect on the dislocation strengthening mechanism, but little on the load transfer strengthening mechanism.

Interfacial design of Cu/SiC composites prepared by powder metallurgy for heat sink applications

Abstract: In order to dissipate the heat generated in electronic packages, suitable materials must be developed as heat spreaders or heat sinks. Metal matrix composites (MMCs) offer the possibility to tailor the properties of a metal (Cu) by adding an appropriate reinforcement phase (SiC) to meet the demands for high thermal conductivities in thermal management applications. Copper/SiC composites have been produced by powder metallurgy. Silicon carbide is not stable in copper at the temperature needed for the fabrication of Cu/SiC. The major challenge in development of Cu/SiC is the suppression of this reaction between copper and SiC. Improvements in bonding strength and thermo-physical properties of the composites have been achieved by a vapour deposited molybdenum coating on SiC powders to control the detrimental interfacial reactions.

Strengthening in a WE54 magnesium alloy containing SiC particles

Abstract: The microstructure and the mechanical properties of the WE54 magnesium alloy reinforced by 13 vol.% of silicon carbide particulates were studied. The composite material was prepared using a powder-metallurgical technique. Compressive deformation properties of the composite were investigated in the temperature range from room temperature up to 300 °C. Transmission electron microscopy revealed cuboidal precipitates in the matrix. Various strengthening mechanisms originating from the matrix and the reinforcing particles are discussed.

Ultrasonic Cavitation-Based Nanomanufacturing of Bulk Aluminum Matrix Nanocomposites

Abstract: Lightweight metal–matrix nanocomposites (MMNCs) (metal matrix with nanosized ceramic particles) can be of significance for automobile, aerospace, and numerous other applications It would be advantageous to develop effective nanomanufacturing methods for fabrication of bulk components of aluminum based MMNCs through solidification processing However, it is extremely difficult to disperse nanosized ceramic particles uniformly in molten aluminum In this paper, a high power ultrasonic probe is used to disperse nanosized SiC particles into molten aluminum alloy A356 Experimental results show that the ultrasonic cavitation based dispersion of nanoparticles in molten aluminum alloy is effective The uniform nanoparticle dispersion in the Al alloy matrix resulted in significantly improved mechanical properties To enhance the nanomanufacturing efficiency, various nanoparticle feeding techniques were explored and experimental results are presented

Microstructure and wear studies of laser clad Al-Si/SiC(p) composite coatings

Abstract: Coatings of a composite material consisting of an Al-Si matrix reinforced with SiC particles were produced by laser cladding on UNS A03560 cast Al-alloy substrates from mixtures of powders of Al-12 wt.% Si alloy and SiC. The influence of the processing parameters on the microstructure and abrasive wear resistance of the coatings was studied. For an interaction time of 0.08 s and a power density of 330 MW/m(2), corresponding to a specific energy of 26 MJ/m(2), the interaction between SiC and liquid Al is limited and the reinforcement particles remain essentially undissolved. The coating's microstructure is formed of SiC particles dispersed in a matrix consisting of primary alpha-Al dendrites and interdendritic (alpha-Al+Si eutectic. For interaction times of 0.3 and 0.45 s and a power density of 193 MW/m(2), corresponding to specific energies of 58 and 87 MJ/m(2), SiC reacts with molten Al and partially dissolves. The resulting microstructure consists of undissolved SiC particles, found mainly at the bottom of the clad tracks, where the maximum temperature reached during processing is lower, and Al4SiC4 and Si particles dispersed in a matrix of alpha-Al+Si eutectic. The coatings prepared with higher specific energy (58 MJ/m(2)) present a hardness of 250 V and an abrasive wear rate in three-body abrasion tests with SiC as abrasive of 1.7 x 10(-4) mm(3)/m, while those produced with 26 MJ/m(2) present a hardness of 120 V and a wear rate of 0.43 x 10(-4) mm(3)/m. These results show that Al4SiC4 and Si increase the hardness of the material by dispersion hardening but do not contribute to its abrasive wear resistance, because they are softer than the abrasive particles, and confirm that the parameters used to prepare Al-Si-SiC composite coatings by laser cladding must be selected so that only minimal reactions occur between SiC and molten Al. (c) 2007 Elsevier B.V. All rights reserved.

Effect of hot extrusion on the microstructure of a particulate reinforced magnesium matrix composite

Abstract: A particulate reinforced magnesium matrix composite fabricated by stir casting was extruded at 250 °C with an extrusion ratio of 12:1 and constant RAM speed of 15 mm/s. Extrusion of the composite causes large scale dynamic recrystallization resulting in a fine matrix microstructure. The reinforcing particles stimulate dynamic recrystallization, and dynamic recrystallization in the composite is sensitive to the particle content on a local scale. The particle distribution of the composite before and after extrusion was studied using a window technique. It is found that the segregation of particles in the as-cast composite is largely eliminated by extrusion and the particle distribution is significantly improved. Extrusion-induced damage to the reinforcement is observed in the extruded composites, and the particle fracture induced by extrusion is also sensitive to the particle content on a local scale.

An experimental determination of optimum processing parameters for Al/SiC metal matrix composites made using ultrasonic consolidation

Abstract: Ultrasonic consolidation, an emerging additive manufacturing technology, is one of the most recent technologies considered for fabrication of metal matrix composites (MMCs). This study was performed to identify the optimum combination of processing parameters, including oscillation amplitude, welding speed, normal force, operating temperature, and fiber orientation, for manufacture of long-fiber-reinforced MMCs. A design of experiments approach (Taguchi L25 orthogonal array) was adopted to statistically determine the influences of individual process parameters. SiC fibers of 0.1 mm diameter were successfully embedded into an Al 3003 metal matrix. Push-out testing was employed to evaluate the bond strength between the fiber and the matrix. Data from push-out tests and microstructural studies were analyzed and an optimum combination of parameters was achieved. The effects of process parameters on bond formation and fiber/matrix bond strength are discussed.

Interfacial reaction during the fabrication of Ni60Nb40 metallic glass particles-reinforced Al based MMCs

Abstract: Ni60Nb40 metallic glass powders were prepared by mechanical alloying and subsequently combined with Al to form an Al–30 wt.% Ni60Nb40 metal matrix composite (MMC). The crystallization of the Ni60Nb40 metallic glass reinforcements and their reaction with the Al matrix during preparation of the MMC were investigated in a differential scanning calorimeter (DSC) upon isothermal annealing. The comparison of the DSC curves of the Ni60Nb40 metallic glass and of the Al–30 wt.% Ni60Nb40 composite shows that the amorphous Ni60Nb40 particles have a very strong resistance against reaction with Al but reaction occurs after crystallization of the metallic glass. The analysis of the isothermal annealing DSC curves gives an activation energy of crystallization of the Ni60Nb40 metallic glass of 724 kJ/mol. The interfacial reaction between Al and the Ni60Nb40 reinforcements is mainly controlled by diffusion. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results indicate that during the interfacial reaction, Ni diffuses from the Ni60Nb40 particles to react with Al and form Al3Ni. At the same time, Al diffuses into the reinforcement particles to react with remaining Nb and form Al3Nb.

Microstructure and dry-sliding wear properties of TiC-reinforced composite coating prepared by plasma-transferred arc weld-surfacing process

Abstract: A wear resistant TiC titanium carbide-reinforced composite coating was fabricated on 1Cr18Ni9Ti austenitic stainless steel substrate by plasma-transferred arc (PTA) weld-surfacing process using Fe–Ti–C powder blends. The microstructure, microhardness and dry-sliding wear behavior of the composite coating were investigated using optical microscopy (OM), X-ray diffraction (XRD), scanning electron micrograph (SEM), energy-dispersive X-ray analysis (EDS), microhardness tester and ring-on-ring wear tester. The formation mechanism of the composite coating has been discussed. Results show that the composite coating consists of primary TiC carbide as the reinforcing phase and TiC/γ-Fe eutectics as the matrix. The composite coating is metallurgically bonded to the 1Cr18Ni9Ti austenitic stainless steel substrate. The TiC/γ-Fe composite coating has high hardness and excellent wear resistance under dry-sliding wear test condition.

Effect of temperature on the tensile properties of an as-cast aluminum alloy A319

Abstract: The tensile properties of an as-cast A319 alloy were investigated as a function of temperature. It was found that the A319-Al alloy remained inherently brittle in the temperature range of −90 °C T T > 270 °C the mode of failure shifts to being essentially ductile by the development of numerous dimples. Under these conditions the development of critical stresses at matrix/particle interfaces needed for brittle fracture no longer occurs. Apparently, at these temperatures thermally activated processes lead to significant relaxation of stress incompatibilities at particle/matrix interfaces and results in appreciable plastic deformation within the matrix.

Experimental Study on Tensile Behavior of Carbon Fiber and Carbon Fiber Reinforced Aluminum at Different Strain Rate

Abstract: In this study, dynamic and quasi-static tensile behaviors of carbon fiber and unidirectional carbon fiber reinforced aluminum composite have been investigated. The complete stress–strain curves of fiber bundles and the composite at different strain rates were obtained. The experimental results show that carbon fiber is a strain rate insensitive material, but the tensile strength and critical strain of the Cf/Al composite increased with increasing of strain rate because of the strain rate strengthening effect of aluminum matrix. Based on experimental results, a fiber bundles model has been combined with Weibull strength distribution function to establish a one-dimensional damage constitutive equation for the Cf/Al composite.

Effect of Graphite and/or Silicon Carbide Particles Addition on the Hardness and Surface Roughness of Al-4 wt% Mg Alloy

Abstract: In this study, the fabrication of A1-4wt% Mg-graphite and/or silicon carbide (SiC) particulate composites is described. Composites of A1-4 wt% Mg alloy with different volume percentage values of graphite and/or SiC particles are prepared using the compocasting technique. In this technique, graphite particles and/or SiC particles are added into a semi-solid slurry during the stirring of the melt. A pitched blade stirrer is used to stir the reinforcement particles in the slurry. The slurry is then poured in a metallic mold to obtain the cast composites. The effect of the addition of graphite and/or SiC particles and porosity content on the Rockwell hardness and machinability is studied in the present work. The results show that the porosities increase with increase in particles content while Rockwell hardness decreases with increase of graphite particles. But SiC particles are found to increase the hardness of composites. Surface roughness improves with graphite content in the cast composite, and poor surface finish is obtained when SiC particles are added.

Compressive behavior and damping property of ZA22/SiCp composite foams

Abstract: The ZA22 alloy composite foams reinforced by 10 vol.% SiC particles (ZA22/SiC p composite foams) were fabricated with the melt foaming route using CaCO 3 blowing agent in this paper. The compressive behavior and damping property of the composite foams were investigated. The results show that SiC particles dispersing in cell walls can alter the deformation mechanism of ZA22 foams. The plateau stress of the composite foams, therefore, fluctuated continually. The damping properties of ZA22/SiC p composite foams are obviously higher than those of ZA22 alloy and ZA22 foams. The addition of SiC particles can improve the damping capacity of ZA22 foams because SiC particles introduce multifarious interfaces and high-density dislocations in composite foams.

Fabrication and Thermal Properties of Carbon Nanotube/Nickel Composite by Spark Plasma Sintering Method

Abstract: Multiwall carbon nanotube (MWNT) materials are attractive because they possess excellent thermal conductivity and mechanical properties. However, few reports exist that focus on improving the thermal conductivity of MWNT by combining it with a metal matrix. Thus to improve the thermal conductivity, a nickel-matrix composite with MWNT was prepared by slurry mixing process using ethanol as a solvent. Using spark plasma sintering (SPS), MWNT/Nickel nanocomposites were fabricated and the fabrication conditions were investigated. The sintered relative densities of the composites containing up to 5 vol% of MWNT were above 99%. The thermal and electrical behaviors of the MWNT/Nickel composites were determined using the laser flash and van der Pauw methods, respectively, and were found to be anisotropic. The thermal conductivity was found to increase by 10% for the composition with 3 vol% MWNT.

New Generation Metal Matrix Composites

Abstract: Metal matrix composite (MMC) materials have attracted considerable attention due to their ability to offer unusual combinations of stiffness, strength to weight ratio, high temperature performance, and hardness. Extensive research work in this area has led to the development of novel in situ processing techniques that are now being used to new generation metal matrix composites that can be used in wide ranging applications in diverse fields. The development and processing of these new generation metal matrix composites are highlighted in this report.