Showing papers on "Metal matrix composite published in 2018"

Investigation of Mechanical Properties of Aluminium 6061-Silicon Carbide, Boron Carbide Metal Matrix Composite

Abstract: High demand on materials to increase the overall performance of automotive and aerospace components has forced the development of composite materials. Among the various composites, Aluminium Metal Matrix Composites (AMMC) are widely used to fulfill the emerging industrial needs. This paper deals with the investigation of mechanical properties of AMMC produced by the stir casting technique for various compositions of boron carbide and silicon carbide reinforced with aluminium alloy 6061. The tensile, flexural, hardness and impact tests were performed and it was found that the hybrid composites had better properties than pure aluminium. The microstructure of the hybrid composites was analysed using Scanning Electron Microscopy (SEM).

Back stress in strain hardening of carbon nanotube/aluminum composites

Abstract: As demonstrated by the loading–unloading tests and the modeling of the grain size effect and the composite effect, mainly owing to the back stress induced by CNTs, carbon nanotube/aluminum (CNT/Al) composites exhibit higher strain hardening capability than the unreinforced ultrafine-grained Al matrix. The back stress induced by CNTs should arise from the interfacial image force and the long-range interaction between statically stored dislocations and geometrically necessary dislocations around the CNT/Al interface. Therefore, this CNT-induced interfacial back stress strengthening mechanism is supposed to provide a novel route to enhancing the strain hardening capability and ductility in CNT/Al composites.

Microstructure and mechanical behavior of AA6082-T6/SiC/B4C-based aluminum hybrid composites

Abstract: The microstructural and mechanical behavior of hybrid metal matrix composite based on aluminum alloy 6082-T6 reinforced with silicon carbide (SiC) and boron carbide (B4C) particles was investigated. For this purpose, the hybrid composites were fabricated using conventional stir casting process by varying weight percentages of 5, 10, 15, and 20 wt% of (SiC + B4C) mixture. Dispersion of the reinforced particles was studied with x-ray diffraction and scanning electron microscopy analyses. Mechanical properties such as micro-hardness, impact strength, ultimate tensile strength, percentage elongation, density, and porosity were investigated on hybrid composites at room temperature. The results revealed that the increase in weight percentage of (SiC + B4C) mixture gives superior hardness and tensile strength with slight decrease in percentage elongation. However, some reduction in both hardness and tensile strength was observed in hybrid composites with 20 wt% of (SiC + B4C) mixture. As compared to the ...

Effects of heat treatment on the microstructure and microplastic deformation behavior of SiC particles reinforced AZ61 magnesium metal matrix composite

Abstract: In this paper, solution and ageing heat treatment processes were used to improve microplastic deformation behaviors of as-cast SiCp/AZ61 magnesium metal matrix composites (Mg MMCs) fabricated by stir casting method. Higher percentages of SiC particle reinforcements showed higher microhardness values. Ageing heat treatment process was seen significant on the 12 h aged 2 wt% SiCp/AZ61 Mg MMC which induced lower microhardness value. At the 12 h ageing of 2 wt% SiCp/AZ61 Mg MMC the formations of particle free regions and discontinuous secondary phases were observed. For a higher ageing time, the secondary phases distribution became continuous and laminar structure. The addition of 5 wt% SiC particles resulted in the formation of Mg2Si phase throughout the whole heat treatment processes. The addition of SiC particles reinforcements increased the phase heterogeneity during ageing heat treatment processes. XRD patterns revealed the presence of nanocrystalline MgSiO3 phase on the 12 h aged 2 wt% SiCp/AZ61 Mg MMC. Using reference intensity ration (RIR) method a 51.6% of MgSiO3 phase was determined which can cause the formation of microplastic deformation behavior. And also, the maximum average crystallite size, compressive microstrain and microcrack-free phase boundaries were observed on the 12 h aged 2 wt% SiCp/AZ61 Mg MMC.

Densification behavior and mechanical properties of nanocrystalline TiC reinforced 316L stainless steel composite parts fabricated by selective laser melting

Abstract: Metal matrix composite parts produced using selective laser melting have superior mechanical properties to those produced using traditional powder metallurgy. In this study, nanocrystalline TiC reinforced 316L stainless steel composite parts were fabricated using selective laser melting, and the effects of the TiC mass fraction, particle size, and processing parameters on the relative density, microhardness, and mechanical properties of the TiC/316L composites were investigated. The results show that the relative density of the fabricated parts is related to the laser power and exposure time, and increases when these parameters are increased. The greater the mass fraction of nano-TiC added, the more severe the degree of spheroidization and the lower the density of the resulting material. The microhardness of the 316L stainless steel parts is enhanced by the nano-TiC particles, and increases with increasing nano-TiC mass fraction. The tensile strength is improved with longer exposure time and with the addition of 2 wt% nano-TiC particles. Compared with pure 316L, the microhardness of the TiC/316L composite parts fabricated with 2 wt% 40 nm TiC enhanced from HV0.3 = 219.1 to 277.6, and the ultimate tensile strength significantly increased from 627.5 to 748.6 MPa. The strengthening mechanism of TiC particles is the refinement of the grain size of the 316L matrix, and the greater amount of TiC particles added, the better the grain refinement of 316L.

Experimental Investigation on Mechanical Properties of an Al6061 Hybrid Metal Matrix Composite

Abstract: The demand for aluminum hybrid metal matrix composites has increased in recent times due to their enhanced mechanical properties for satisfying the requirements of advanced engineering applications. The performance of these materials is greatly influenced by the selection of an appropriate combination of reinforcement materials. The reinforcement materials include carbides, nitrides, and oxides. The ceramic particles, such as silicon carbide and aluminum oxide, are the most widely used reinforcement materials for preparing these composites. In this paper, an attempt has been made to prepare an Al6061 hybrid metal matrix composite (HAMMC) reinforced with particulates with different weight fractions of SiC and Al2O3 and a constant weight fraction (5%) of fly ash by a stir-casting process. The experimental study has been carried out on the prepared composite to investigate the mechanical properties due to the addition of multiple reinforcement materials. The density and mechanical properties, such as ultimate tensile strength, yield strength, impact strength, and the hardness and wear characteristics of the proposed composite, are compared with those of unreinforced Al6061. The experimental investigation is also aimed at observing the variation of properties with a varying weight percentage of the reinforcement materials SiC and Al2O3 simultaneously with the fly ash content maintained constant. The outcome of the experimental investigation revealed that the proposed hybrid composite with 20% of total reinforcement material exhibits high hardness, high yield strength, and low wear rate but no considerable improvement in impact strength.

Room and elevated temperature sliding wear behavior of cold sprayed Ni-WC composite coatings

Abstract: The tribological properties of cold sprayed Ni-WC metal matrix composite (MMC) coatings were investigated under dry sliding conditions from room temperature (RT) up to 400 °C, and during thermal cycling to explore their temperature adaptive friction and wear behavior. Characterization of worn surfaces was conducted using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Raman spectroscopy to determine the chemical and microstructural evolution during friction testing. Data provided insights into tribo-oxide formation mechanisms controlling friction and wear. It was determined that the steady-state coefficient of friction (CoF) decreased from 0.41 at RT to 0.32 at 400 °C, while the wear rate increased from 0.5 × 10−4 mm3/N·m at RT to 3.7 × 10−4 mm3/N·m at 400 °C. The friction reduction is attributed primarily to the tribochemical formation of lubricious NiO on both the wear track and transfer film adhered to the counterface. The increase in wear is due to a combination of thermal softening of the coating and a change in the wear mechanism from adhesive to more abrasive. In addition, the coating exhibited low friction behavior during thermal cycling by restoring the lubricious NiO phase inside the wear track at high temperature intervals. Therefore, cold sprayed Ni-WC coatings are potential candidates for elevated temperature and thermally self-adaptive sliding wear applications.

Characterization & evaluation of Al7075 MMCs reinforced with ceramic particulates and influence of age hardening on their tensile behavior

Abstract: Aluminium has a massive demand in the areas of automobile, aerospace and diverse engineering applications in order to furnish the requirement in those fields But this technological evolution needs something more than aluminium Materialogists are struggling hard to find out a material which owns sound mechanical and thermal properties and also superior than aluminium in each extent Metal matrix composite (MMC) is a solution Generally, metal matrix composites contain a low density material, ie aluminium or magnesium, reinforced with fibers or particulate of a ceramic material, ie silicon carbide or graphite They show greater specific strength, high stiffness, elevated operating temperature, and superior wear resistance, along with the possibility to customize these properties for a specific use In this study, Al 7075 is taken as a base matrix material, whereas ceramic materials like SiC, Al2O3, B4C and TiB2 are used as reinforcements There are different methods available for fabricating metal matrix composite materials and in this work, stir casting technique, which is a liquid state process, is used Four different MMC specimens were produced with 15 % SiC, 15 % Al2O3, 15 % B4C and 15 % TiB2 Mechanical properties ie tensile strength, hardness, and impact strength were studied for the prepared specimens The results were charted and presented graphically to describe these materials characteristics

High temperature characteristics of Al2024/SiC metal matrix composite fabricated by friction stir processing

Abstract: In the present study, friction stir processing (FSP) is used for the synthesis of an aluminum metal matrix composite (MMC) reinforced by SiC particles. MMC specimens with reinforced microstructures exhibited significant improvement in hardness (near 50%). Isothermal uniaxial tensile tests were employed for the as-received, friction stir processed and composite microstructures at ambient and high temperatures under strain rates ranging from 10−2 to 10−4 s−1 to investigate the effect of deformation rate on the mechanical behavior. At ambient temperature, notable improvement of the yield strength was observed reaching about 240% of the as-received samples while the ductility was reduced near to 4%. Elevated temperature flow curves were perceptibly sensitive to strain rate, especially for FSPed and MMC samples. Fracture surface observations hinted at the distribution of second phase particles along with possible damage mechanisms.

Pressure infiltration processes to synthesize metal matrix composites – A review of metal matrix composites, the technology and process simulation

Abstract: Metal matrix composites (MMCs) acquire their improved physical and mechanical properties through the careful reinforcement of their matrices by a variety of light but strong and stable reinforcemen...

Stability of Metal Matrix Composite Pads During High-Speed Braking

Abstract: Metal matrix composites are now commonly used as braking pads for the train running over 250 km/h by virtue of a number of desirable properties. To develop a fundamental understanding of the stability of metallic composites at high-speed braking, four typical composite materials, with different Cu and Fe contents, were subjected to a series of high-speed emergency braking at a simulative running speed of 380 km/h and a braking inertia of 27 kg/m−2 and a normal pressure of 1.27 MPa in this paper. The results showed that the sample with higher Cu content displayed a fade COF and deteriorated wear, but the one with higher Fe content could maintain a stable COF and low wear rate. The tribological behaviour is associated with the relative rate of generation and consumption of the tribo-oxide film. For the sample with higher Cu content, the generation rate of tribo-oxide film was less than the consumption rate, and the COF fading and wear deterioration with the increasing braking times were attributed to the reduction in resistance to deform or to shear the asperities, which was thought to be caused by the degradation of near-surface layer due to the removal of protective tribo-oxide film. In contrast, for the sample with higher Fe content, the generation rate was approximately equal to the consumption rate, and a well-established tribo-oxide film on the surface was responsible for the stable friction level and low wear rates.

A new approach for fabrication of titanium-titanium boride periodic composite via additive manufacturing and pressure-less sintering

Abstract: This study proposes a new additive manufacturing (AM) based methodology to fabricate periodic metal matrix composite architectures, with a focus on titanium (Ti)-titanium boride whisker (TiBw) composites. The manufacturing method includes binder jetting AM of the titanium matrix reinforced periodically by the extrusion of a custom-developed highly loaded resin, containing titanium di-boride (TiB2) particles. A low-temperature pressure-less sintering method was then applied to increase the mechanical strength of green samples produced from the additive manufacturing step. The sintering process also fosters the chemical reaction between the matrix and ceramic, resulting in the growth of titanium boride whisker (TiBw). The ceramic volume fraction and sintering protocol were studied as two main input variables in the design and fabrication steps. Investigating the influence of input parameters on the volume fraction and morphology (whisker formation) of TiB determined that the physical properties of the specimens, such as stiffness, were affected. The data analysis suggested a higher possibility for the formation and growth of TiBw as the temperature elevated in the sintering step (1400 °C). The ranges of 1.6 ± 0.2 GPa–3.7 ± 0.4 GPa and 83.9 ± 18.7 MPa–165 ± 13.2 MPa for the Young's modulus and Yield stress of the specimens were obtained, respectively. The stiffness of the samples was enhanced significantly by increasing the temperature and volume fraction. In particular, those samples sintered up to 1400 °C displayed 6.4%–15.2% improvement in the stiffness, although only a small fraction of the ceramic material was incorporated into the design: 2% and 4%, respectively. The similar trend of the improvement in density of the porous matrix was observed (i.e., 4.5%–19%). The range of mechanical and structural properties of the periodic composite developed in this study demonstrated the relevance of applying this method to the fabrication of biomedical and other lightweight titanium composite structures.

Direct metal laser sintering of TiN reinforced Ti6Al4V alloy based metal matrix composite: Fabrication and characterization

Abstract: In the present research, direct metal laser sintering (DMLS) method was chosen to fabricate titanium nitride (TiN) reinforced Ti6Al4V alloy based metal matrix composites (MMCs) under an argon atmosphere using continuous wave (CW) fiber laser having a capacity of 400 W. Laser sintering process parameters, such as layer thickness (0.4 mm), laser beam spot diameter (0.4 mm), and hatching gap (0.2 mm) were kept constant throughout the experiments. Effects of input variable process parameters, such as laser power (50–65 W), scanning speed (3500–4500 mm/min), and volume % of TiN (5–15% v/v) on density, microhardness, and coefficient of friction of the fabricated MMCs were analyzed. The obtained results show the improvement in the physical properties of the fabricated MMCs and FESEM images evidently confirm the presence of TiN particulates and also revealed the uniform distribution of the TiN reinforcement in Ti6Al4V matrix. It was found that the microhardness measured by Vickers test was improved from 388 to 590 HV0.2 with an increase in the volume percentage of TiN. The results showed the coefficient of friction for fabricated samples were in the range of 0.33–0.42. The density (3.40–4.10 g/cm3) of the MMCs was found to increase with increasing the volume percentage of TiN reinforcement in the powder mixture. X-ray diffraction (XRD) analysis of the fabricated MMC confirmed the presence of different in-situ phases, such as Ti, TiN, TiO2, VN, AlV, Ti3Al2N2, and V6N2.7 as a consequence of a series of a chemical reaction between TiN and different elements of Ti6Al4V in the argon atmosphere.

Studies on Tribological Characteristics of Centrifugally Cast SiCp-Reinforced Functionally Graded A319 Aluminium Matrix Composites

Abstract: The concept of functionally graded materials is effectively applied to design and fabricate engineering components with location-specific wear resistance suited to the particular application. The present study describes the wear behaviour of centrifugally cast A319 aluminium functionally graded metal matrix composites (FGMMC) formed from 20 wt% SiCp-reinforced composite. Liquid stir casting method is used for homogeneous metal matrix composite preparation followed by vertical centrifugal casting for FGMMC rings production. Microstructure analysis of specimen reveals a homogeneous distribution of SiCp reinforcements for the gravity and a gradient particle distribution, in the radial direction forming different zones, for the centrifugal castings. The dry sliding wear behaviour is studied on a DUCOM pin-on-disc tribometer with steel disc and by using FGMMC pins produced from different zones. Wear studies show gradient tribological properties, within a component, with a maximum wear resistance at the particle rich region, lesser in transition zone and the minimum wear resistance at the inner zones. SEM observation confirms abrasive wear predominance by revealing the microgrooves and ploughing on the worn-out surfaces.

Analysis of the influence of cutting parameters on surface roughness and cutting forces in high speed face milling of Al/SiC MMC

Abstract: In recent years, the newly developed composite materials, such as Metal Matrix Composite (MMC), have been widely used. As MMCs have increasing applications, the investigations of their machining properties have become justifiable. Furthermore, high-speed machining processes are utilized to increase the productivity. In this study, the influence of high speed cutting parameters on the surface roughness and cutting forces of machined AL/SiC composite has been investigated. The cutting speed up to 2500 m min−1, CO2 cryogenic coolant and AL/SiC MMC consisting 15% silicon carbide were used. Design of experiment method using 5-level central composite design was also used. Results show that using CO2 cryogenic coolant increases cutting forces 3%–8%, but improves the surface roughness by 19%–23%. The appropriate surface roughness is achieved in the presence of coolant while cutting speed is more than 1800 m min−1, the feed rate is less than particle size per a tooth, and depth of cut is between 1 to 1.1 mm.