Showing papers on "Metal matrix composite published in 2015"

Graphene-and-Copper Artificial Nacre Fabricated by a Preform Impregnation Process: Bioinspired Strategy for Strengthening-Toughening of Metal Matrix Composite.

Abstract: Metals can be strengthened by adding hard reinforcements, but such strategy usually compromises ductility and toughness. Natural nacre consists of hard and soft phases organized in a regular “brick-and-mortar” structure and exhibits a superior combination of mechanical strength and toughness, which is an attractive model for strengthening and toughening artificial composites, but such bioinspired metal matrix composite has yet to be made. Here we prepared nacre-like reduced graphene oxide (RGrO) reinforced Cu matrix composite based on a preform impregnation process, by which two-dimensional RGrO was used as “brick” and inserted into “□-and-mortar” ordered porous Cu preform (the symbol “□” means the absence of “brick”), followed by compacting. This process realized uniform dispersion and alignment of RGrO in Cu matrix simultaneously. The RGrO-and-Cu artificial nacres exhibited simultaneous enhancement on yield strength and ductility as well as increased modulus, attributed to RGrO strengthening, effective ...

Microstructure, microhardness and corrosion resistance of Stellite-6 coatings reinforced with WC particles using laser cladding

Abstract: The paper presents the method of preparation and study results of metal matrix composite coatings (MMC coating) in the system of Stellite-6 and tungsten carbides. Changes in microstructure, corrosion resistance, microhardness, phase and chemical composition as well as surface conditions were investigated. Stellite-6/WC MMC coatings were prepared by laser cladding technology using a 1 kW continuous wave Yb:YAG disk laser with a powder feeding system. Two different powder mixtures containing 30% and 60% of WC and three different values of laser beam power were used. It was found that increasing WC values caused an increase in microhardness on the cross-section of the produced coating in comparison to the substrate. Depending on the laser beam power, the coatings produced with 30% WC achieved microhardness in the range from about 350 HV0.05 (700 W) to about 680 HV0.05 (550 W). Twice as large amount of WC particles in the powder mixture resulted in increase of microhardness from about 700 HV0.05 (700 W) to about 1500 HV0.05 (550 W). In the coating M7C3, M6C and M23C6 carbides were identified by an X-ray diffraction method. Special attention was given to bondings between carbide particles and metal matrix, which had a characteristic microstructure. A reduction of corrosion resistance with increasing WC content in coating was also discovered.

Investigating the electrical discharge machining (EDM) parameter effects on Al-Mg2Si metal matrix composite (MMC) for high material removal rate (MRR) and less EWR–RSM approach

Abstract: Al-Mg2Si composite is a new group of metal matrix composites (MMCs). Electrical discharge machining (EDM) is a nonconventional machining process for machining electrically conductive materials regardless of hardness, strength and temperature resistance, complex shapes, fine surface finish/textures and accurate dimensions. A copper electrode and oil-based dielectric fluid mixed with aluminum powder were used. The polarity of electrode was positive. Response surface methodology (RSM) was used to analyze EDM of this composite material. This research illustrates the effect of input variables (voltage, current, pulse ON time, and duty factor) on material removal rate (MRR), electrode wear ratio (EWR), and microstructure changes. The results show that voltage, current, two-level interaction of voltage and current, two-level interaction of current and pulse ON time, and the second-order effect of voltage are the most significant factors on MRR. Pulses ON time and second-order effect of pulse ON time are the most significant factors affecting EWR. Microstructure analysis of EDM on Al-Mg2Si samples revealed that voltage, current, and pulse ON time have a significant effect on the profile and microstructure of machined surfaced.

Investigation on microstructural and mechanical properties of B4C–aluminum matrix composites prepared by microwave sintering

Abstract: B 4 C reinforced aluminum composites were fabricated by microwave heating of the mixture of B 4 C (10, 15 and 20 wt%) and aluminum powders at 650, 750, 850 and 950 °C. The effect of different amounts of B 4 C on the microstructure and mechanical properties of aluminum matrix was examined. The maximum bending (238 ± 10 MPa) and compressive strength (330 ± 10 MPa) values were measured for composites sintered at 950 and 750 °C, respectively. The maximum hardness (112 Vickers) was measured for Al–20 wt% B 4 C composite sintered at 850 °C. XRD investigations showed the decomposition of boron carbide and also the formation of Al 3 BC by heating the composites at 850 °C. SEM micrographs showed uniform distribution of reinforcement particles in Al matrix.

Dry Sliding Wear Behaviour of Aluminium Al–Si12Cu/TiB2 Metal Matrix Composite Using Response Surface Methodology

Abstract: An aluminium Al–Si12Cu/TiB2 metal matrix composite was fabricated using the liquid metallurgy route, and its dry sliding wear characteristics were investigated under various sliding parameters. The titanium diboride (TiB2) particles (10 wt%, average size 50–60 µm) were incorporated into the matrix and its microstructural characteristic was examined. A five-level central composite design experiment was developed using response surface methodology; parameters such as load, velocity and sliding distance were varied in the range of 10–50 N, 1–5 m/s and 500–2500 m, respectively. Dry sliding wear tests were performed as per the experimental design using a pin-on-disc tribometer at room temperature. Significance tests, analyses of variance and confirmatory tests were performed to validate the developed model. Study of the microstructural characteristics revealed uniform dispersion of the reinforcement particles throughout the composite. The regression result showed that the developed model performed well in relating the wear process parameters with the response and predicting the wear behaviour of the composite. The surface plot showed that wear rate increased with increasing load at all velocities and distances, and decreased with increasing sliding distance. In the case of velocity, the wear rate decreased initially, increasing after the transition velocity had been reached. Scanning electron microscopy analysis revealed severe wear at a high load due to a higher level of deformation of the composite surface.

Investigation on microstructure and mechanical behavior of Al–ZrB2 composite prepared by microwave and spark plasma sintering

Abstract: In the present work, aluminum-10 wt% ZrB 2 -1 wt% Co composite was prepared by two different sintering methods: microwave and spark plasma, and the relative density of 97±0.3% TD (at 640 °C) and 98±0.3% TD (at 450 °C) was obtained, respectively and XRD analysis revealed Al and ZrB 2 as the only crystalline phases. Mechanical investigations revealed that the bending and compressive strength of SPS samples were 275±10 and 381±16 MPa, respectively, which were higher than those of microwave samples. The microhardness values of SPS and microwave sintered specimens were obtained 160 and 110±12 Vickers, respectively. Microstructural investigations revealed a homogeneous distribution of ZrB 2 particles in the aluminum matrix in both methods.

Consolidation of aluminum-based metal matrix composites via spark plasma sintering

Abstract: Aluminum-based metal matrix composite (MMC) materials containing SiC, AlN, Si3N4 or BN were processed by spark plasma sintering (SPS). Ceramic powder type, size and content were investigated to determine their effect on sinter quality. SiC, AlN and Si3N4 proved to be amenable to this style of processing whereas all systems containing BN were not. Full densification of MMCs that incorporated finer ceramic particles was problematic due to the presence of ceramic clusters and the extent to which aluminum could be forced into these regions. MMCs that incorporated coarser ceramic particles were more easily densified, but their hardness benefits were inferior. Three point bend tests proved to be an effective tool in determining the relative sinter quality of MMC systems. SiC outperformed AlN MMC samples in bend tests. Excellent ductility and bend strength was developed at low temperatures, while equivalent AlN-bearing materials required significantly higher temperatures to achieve comparable properties.

Solid-state additive manufacturing for metallized optical fiber integration

Abstract: The formation of smart, Metal Matrix Composite (MMC) structures through the use of solid-state Ultrasonic Additive Manufacturing (UAM) is currently hindered by the fragility of uncoated optical fibers under the required processing conditions. In this work, optical fibers equipped with metallic coatings were fully integrated into solid Aluminum matrices using processing parameter levels not previously possible. The mechanical performance of the resulting manufactured composite structure, as well as the functionality of the integrated fibers, was tested. Optical microscopy, Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) analysis were used to characterize the interlaminar and fiber/matrix interfaces whilst mechanical peel testing was used to quantify bond strength. Via the integration of metallized optical fibers it was possible to increase the bond density by 20–22%, increase the composite mechanical strength by 12–29% and create a solid state bond between the metal matrix and fiber coating; whilst maintaining full fiber functionality.

Microstructure and mechanical properties of an Al–TiC metal matrix composite obtained by reactive synthesis

Abstract: A metal matrix composite has been obtained by a novel synthesis route, reacting Al 3 Ti and graphite at 1000 °C for about 1 min after ball-milling and compaction. The resulting composite is made of an aluminium matrix reinforced by nanometer sized TiC particles (average diameter 70 nm). The average TiC/Al ratio is 34.6 wt.% (22.3 vol.%). The microstructure consists of an intimate mixture of two domains, an unreinforced domain made of the Al solid solution with a low TiC reinforcement content, and a reinforced domain. This composite exhibits uncommon mechanical properties with regard to previous micrometer sized Al–TiC composites and to its high reinforcement volume fraction, with a Young’s modulus of ∼110 GPa, an ultimate tensile strength of about 500 MPa and a maximum elongation of 6%.

Synthesis, structure, and properties of superhydrophobic nickel–PTFE nanocomposite coatings made by electrodeposition

Abstract: The objective of the current research is to create multifunctional metal matrix composite coatings that are able to provide high strength as well as high water repellency by electrodeposition of nanocrystalline nickel matrix with embedded polytetrafluoroethylene (PTFE) particles. The study of the co-deposition process demonstrated that the amount of PTFE co-deposited is highly dependent on the concentration of PTFE particles in the electroplating bath. A very high fraction of co-deposited PTFE was achieved (69 vol.%) using a concentration of 30 g/L of PTFE particles in the plating bath. The contact angle of the surface greatly increased when the PTFE content increased over 50 vol.%. At 69 vol.% PTFE the coatings had a contact angle of 152°. Saccharin was added to the electroplating bath in an attempt to refine grain size. Using transmission electron microscopy, the average grain size of the nickel matrix without saccharin was determined to be 27 nm for the coating containing 69 vol.% PTFE. However, no nickel grain size reduction was observed when saccharin was added as it was found that the composite samples already had a very fine grain structure likely due to the use of cetyltrimethylammonium bromide (CTAB) as a PTFE particle dispersant. The addition of saccharin provided no additional hardening of the composite while the wetting angle was greatly decreased at concentrations greater than 0.1 g/L.

Modeling machining of particle-reinforced aluminum-based metal matrix composites using cohesive zone elements

Abstract: Finite element modeling for the machining of heterogeneous materials like particle-reinforced metal matrix composites has not been much successful as compared to homogeneous metals due to several issues. The most challenging issue is to deal with severe mesh distortion due to nonuniform deformation inside the workpiece. Other problems are related to the modeling of the interface between reinforcement particles and matrix and tool-reinforcement particle interaction. In this study, different strategies are adopted for finite element models (FEM) to cope with the above issues and comparative analyses have been performed. These 2D FE models are based on plane strain formulations and utilize a coupled temperature displacement method. The workpiece is modeled using reinforcement particle size and volume fraction inside the base matrix. The interface between the reinforcement particles and the matrix is modeled by using two approaches, with and without cohesive zone elements, and the chip separation is modeled with and without using a parting line. This allows models to simulate the local effects such as tool-reinforcement particle interaction and reinforcement particle debonding. In addition, the models can predict cutting forces, chip morphology, stresses, and temperature distributions. The effects of different methodologies on the model development, simulation runs, and predicted results have been discussed. The results are compared with experimental data, and it has been found that the utilization of cohesive zone elements (CZE) with the parting line approach seems to be the best one for the modeling of metal matrix composite (MMC) machining.