Hardness Of Metal Matrix Composites Research Articles

Influence of Graphite Particles on the Mechanical and Wear Characterization of Al6082 Alloy Composites.

In the current study, a two-stage stir cast process was used to produce Al6082 reinforced with sized graphite particulates, and the material's mechanical and tribological properties were analyzed. The graphite content in the Al6082 alloy was increased from 2 to 6% in steps of 2 wt %. The impact of graphite addition to Al6082 was evaluated using microstructural micrographs, hardness test, tensile test, and wear test outcomes. The matrix alloy's microstructure and particle distribution were analyzed using scanning electron microscopy and energy-dispersive spectroscopy. The microstructure of Al6082 shows that the reinforcement particles are evenly distributed throughout the matrix. Although the hardness of metal-matrix composites was slightly reduced when graphite was added at concentrations of up to 6 wt %, the material's tensile strength and wear resistance were significantly improved. Micrographs taken by a microscope were used to examine the fractured surfaces of tensile test specimens. Wear experiments were performed using a conventional pin-on-disc tribometer to examine the tribological properties of both unreinforced matrix and graphite composites. With the addition of 2, 4, and 6 wt % of graphite particles, the composites' wear resistance was significantly improved. Wear of alloys and their composites was analyzed to determine how load and sliding speed impacted wear loss.

Duplex strengthening via SiC addition and in-situ precipitation in additively manufactured composite materials

Additive manufacturing (AM) is flexible to in-situ alloying multi-type powders, which highlights the potential in developing high-performance composite materials with complex geometry. Unlike existing AM-processed metal matrix composites (MMCs) in literature, which are mainly strengthened by the ceramic particles, this work investigates the AM of SiC-reinforced precipitation hardening steel to trigger in-situ precipitation and promote duplex strengthening (ceramic particles + precipitates) in the metal matrix. The effects of SiC content on the densification , microstructure evolution , precipitation kinetics, and mechanical properties are investigated. The relative density of MMCs with 3–12 vol% SiC is higher than 99.4%, and further increasing SiC content deteriorates laser formability and increases defects content dramatically. The microstructure alters from cellular to columnar and then to dendritic structures with increasing SiC addition. Massive nanoprecipitates (e.g., Fe 2 Mo and η-Ni 3 Ti) are observed in as-fabricated MMCs without heat-treatment, which could have in-situ formed by heterogeneous nucleation at the SiC particles and dislocations. The precipitation kinetics suggests SiC addition increased the nucleation rate of precipitates. Additionally, the hardness of MMCs are enhanced, and the highest yield strength and tensile strength reached about 1.2 GPa and 1.6 GPa in MMCs, respectively. The underlying strengthening mechanisms are the precipitates and SiC particles duplex second-phase strengthening, as well as dislocation strengthening. • SiC addition affects the precipitation kinetics and accelerates precipitation behaviour. • In-situ precipitation promotes duplex strengthening (ceramic particles + precipitates). • The achieved tensile strength is at the highest level among a wide range of MMCs.

Spark Plasma Sintering of Copper Matrix Composites Reinforced with TiB2 Particles.

The aim of this study is to fabricate a Cu-0.5wt%TiB2 composite by mechanical alloying (MA) and spark plasma sintering (SPS). Increasing the milling time, the powders are subjected firstly to a severe flattening process and then to intense welding, which promotes the refinement of TiB2 particles, their uniform dispersion in the metal matrix, and the adhesion between the two constituents. Sintered metal matrix composites (MMC) exhibit density values between 99 and 96%, which are generally decreased by increasing milling time in view of the stronger strain hardening. On the other side, the hardness increases with milling time due to the refinement of TiB2 particles and their improved distribution. The hardness of MMC is three times higher (225 HV0.05) than the starting hardness of atomized copper (90 HV0.05). Tensile tests show a loss of ductility, but ultimate tensile strength has been increased from 276 MPa of atomized copper to 489 MPa of MMC milled for 240 min. The thermal conductivity of MMC is comparable to that of atomized copper (300 W/mK), i.e., much higher than that of the commercial Cu-Be alloy (Uddeholm Moldmax HH, 106 W/mK) typically used for tooling applications.

Morphological and Mechanical Characteristics of Hybrid Aluminium Matrix Composites

In emerging trend day by day the world facing lot of new invention in automobiles and aerospace industries. They need new smart materials lighter in weight, tensile strength and hardness with good thermal shock resistance compared to available conventional metals. Especially the aluminium based Metal Matrix Composite (MMC) materials can provide these properties. In this research article an attempt is made to find the mechanical properties and morphological of the aluminium alloys of Al 356 mixed with silicon carbide particles (SiCp) and Mica. All these three different MMCs were fabricated in stir casting method. Their tensile strengths are studied and compared with the help of Vickers micro hardness tester and tensile testing machine. The morphological characteristics are tested and compared with the Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDAX) optical microscopy. The tensile strength and hardness of MMCs were comparatively increased than the aluminium alloys.

Effect of amorphous silica by rice husk ash on physical properties and microstructures of recycled aluminium chip AA7075

AbstractHigh strength to weight ratio of aluminium reinforced as metal matrix composites is a well known material used in automotive application. The effects of recycled aluminium chips AA7075 with amorphous silica by rice husk ash on the physical properties and microstructure were investigated. Recycled aluminium chip AA7075 was reinforced with agro waste of amorphous silica rice husk ash i. e., 2.5 %, 5 %, 7.5 %, 10 % and 12.5 %. Samples of these metal matrix composites were prepared by cold compaction method due to the lower energies consumption and operating cost compared to conventional recycling by casting. Physical testing of density, apparent porosity, water absorption and hardness tests of the metal matrix composites samples were examined in the current study. The density of metal matrix composites was increased up to 5 % of amorphous silica, and then decreased with increasing mass fraction of amorphous silica. Porosity and water absorption of metal matrix composites were significantly consistent at increasing mass fraction of amorphous silica, while the hardness of metal matrix composites was increased at increasing amorphous silica. Consequently, the microstructures of metal matrix composites were observed via optical microscope to analyze the dispersion of the reinforced composites. The microstructures of metal matrix composites were found non‐homogeneous and random distribution of amorphous silica and aluminium chip AA7075 compared to 100 % recycled aluminium chip AA7075. Based on investigation to aluminium reinforced rice husk ash composites, it has good potential to improve the material behavior of metal matrix composites by appropriate composition amorphous silica to composite.

A method to calculate the bulk hardness of metal matrix composite using Hadfield steel reinforced with niobium carbide particles as an example

A conceptual model is proposed in this paper to calculate the bulk hardness of particle-reinforced metal matrix composites. Hadfield steel with niobium carbide particles is taken as an example to show the feasibility of this proposed method. A micro-scale concept called representative equivalent volume is used to investigate the heterogeneous microstructure and the impact of water quenching on the equivalent mechanical properties of the metal matrix composite. Furthermore, the continuum-scale indentation process used in laboratory hardness testing is simulated by the finite element method based on the stress-strain curves obtained from the micro-scale modeling. The simulated hardness is compared with laboratory measurements and a good agreement is observed confirming the model.

Analysis of Wear Resistance, Cracks and Hardness of Metal Matrix Composites with SiC Additives and Al2O3 as Reinforcement

Objective: In modern manufacturing technology, now a day’s metal matrix composites are being increasingly identified as new wear resistant material. The main purpose of this article is to investigate the wear down and depth of indentation of the composite material of Al-6061 alloy strengthened with silicon carbide particulate and supported with alumina particulate constructed by stir casting method. Method/Analysis: The wear down rate and frictional properties of the composite were learned by using the dry sliding wear test with a pin on disk wear tester. The investigation was carried out with 1750 meters of sliding distance and 1.55m/s of stable sliding velocity over different loads by 10N and 20N for aluminium metal matrix composite. Findings: The testing result indicated that the wear resistance increases when there is increase in the load as well as in the sliding distance. Additionally an effort was made by keeping 7% of Al2O3 constant along with increase in 10, 15 and 20% of SiC. It was observed that, the strengthened aluminium metal matrix in addition of SiC and Al2O3 decreases the range of wear rate. Also found that the coefficient of friction increased by means of raising the load and quantum of reinforcement. Application/Improvements: By using scanning electron microscope the wear surfaces were examined and it was observed that the micro and transverse cracks, mild and severe wear occurred in the composite worn surfaces and wear structure of the composite.

Tensile Properties, Hardness and Micro Structural Analysis of Al 6061 – SiCP Metal Matrix Composites Fabricated by Ultrasonic Cavitation Approach

The combined use of ultrasonic cavitation and mechanical stirring to disperse the silicon carbide particles (SiCp) in molten aluminum alloys has been studied. Composite materials with various weight percentage of Al 6061 alloy (matrix) and SiCp (reinforcement, average particle size 10 micrometers) were fabricated. The microstructure of the composites was investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The micro structural analysis validates the good dispersion of SiCp in the metal matrix. The tension test results reveal that the tensile strength of the as-cast metal matrix composites (MMCs) have been improved significantly for the 5 and 10 weight percentage of SiCp and then decreases. The hardness of MMCs increases and the ductility decreases as the particle percentage increases. The ultrasonic cavitation based fabrication is a novel route for producing wide range of MMCs.

Microstructural characterization of PM-Al and PM-Al/Si composites reinforced with lignite fly ash

In the present paper, two Class C, lignite fly ashes (FAs) were utilized for the fabrication of Al/fly ash metal matrix composites (MMCs) using the powder metallurgy (PM) technique. Aluminum–fly ash and aluminum/silicon alloy (Al–12% Si)–fly ash mixtures, containing 5, 10 and 15wt.% of – both pozzolanic and hydraulic – FAs were prepared and compacted. The green products were tested for their thermal behavior in order for the sintering temperature to be determined. Then, they were sintered for 2 and 6h. The density of composites was decreasing with the increase of the percentage participation of fly ash particles into them. Apart from that, although FA clusters had been developing in the metal matrix, there was a significant enhancement in the hardness of MMCs when increasing FA content, which is mainly attributed to the intense calcareous nature of the reinforcement material. Volume and mass changes throughout calcination were also estimated as a function of increasing FA weight percent and it seems that CaO (%) of FAs plays a crucial role regarding the post-sintering raise in the mass and volume of composites. Microscopic studies of green and sintered compacts clearly indicated the effectiveness of the sintering process. Additionally, the composites were characterized in terms of their chemical composition and mineralogical structure. The rise of Ca–Si- and Si-mineral phases is intense, particularly for the composites with the highest percentage presence of CaO in FAs (15wt.%) and does not differentiate as a function of the sintering time.

The Strength and Hardness of Metal Matrix Composites by Binder Additives

20 vol.% aluminum borate whisker (Al18B4O33w) reinforced AC4CH alloy composite was fabricated by squeeze casting method. The matrix is controlled its impurities, which make metal alloys, especially AC4CH alloy that is made by restraining 0.2% Iron and aluminum to make a matrix material. The perform of composite materials was made from Al18B4O33w with 5% regulated three kinds of inorganic binders, SiO2, Al2O3 and TiO2 sol, respectively and then sintered at 1373K. The composites were obtained by squeeze cast infiltration of the molten alloy to the perform. Then it was squeeze casting into the matrix. The status of adhesions of whisker perform was Observed by SEM. Micro-Vickers hardness and tensile properties at the room temperature were estimated. Al18B4O33w/ AC4CH composites containing TiO2 sol has excellent properties on tensile properties and microvickers hardness compared with the other composites without inorganic binder, containing SiO2 and Al2O3 sol inorganic binder.

The effect of die shape on the hot extrudability and mechanical properties of 6061 Al/Al 2O 3 composites

Metal matrix composites (MMCs) fabricated by the compocasting process show a homogeneous distribution of the reinforcing fiber in the matrix. Microstructural observation of hot extruded MMCs reveals that as the extrusion ratio increases, the fiber alignment becomes improved, but fiber fracture occurs more severely. The mechanical properties of hot extruded MMCs are better than those of the matrix metal, with the exception of the elongation at failure, and are not influenced significantly by the extrusion temperature. The tensile strength and hardness of MMCs are improved to a greater degree by hot extrusion using a constant-strain-rate die. Also, there exists a critical extrusion ratio that gives maximum strength, which is 5.44 in this study. Additionally, fractograph of the tensile specimen of extruded MMC indicates the ductile fracture behavior of the matrix.