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CHARACTERISTICS AND PROPERTY EVALUATION OF METAL MATRIX COMPOSITES [MMCs] USING STIR CASTING Submitted in partial fulfillment of requirements for the award of degree of



1112840020ANKUSH VERMA




I hereby declare that the work carried out in this project report entitled, CHARACTERISTICS AND PROPERTY EVALUATION OF METAL MATRIX COMPOSITES [MMCs] USING STIR SQUEEZE CASTING, is presented in partial fulfillment of the requirements for the award of degree of Bachelor of Technology in Mechanical Engineering with specialization in production & industrial system engineering, submitted to the Department of Mechanical Engineering, Bharat Institute of Technology, Meerut, under the guidance of Mr.Saurabh Gupta, Assistant Professor,Department of Mechanical and Industrial Engineering.









Place: Meerut

This is to certify that the above statement made by the candidate is correct to the best of my knowledge and belief. (Mr. Saurabh gupta)

Assistant Professor

ACKNOWLEDGEMENT The euphoria and joy, accompanying the successful completion of my task would be incomplete without the special mention of those people whose guidance and encouragement made my effort successful.I am deeply indebted to my guides Mr. Saurabh Gupta, Asst. Professor in the department of MECHANICAL ENGINEERING, Bharat Institute of Technology, Meerut, whose help, stimulating suggestions and encouragement helped me in all the time to make my effort successful.

Especially, I would like to give my special thanks to my parents and my friends, whose support and motivation inspire me to complete the study.ANKIT PATHAK












10Classification of composites


14Constituents of MMCs

16Types of MMCs






Stir Squeeze Casting Set up


Stir Squeeze Casting Procedure






LIST OF FIGURESFig no.Name of figurePage no.

1 Classification of composite8

2(a)Typical microstructure of silicon carbide particle/ aluminum alloy composite18

2(b)Typical microstructure of silicon carbide particle/ aluminum alloy composite18

3Some application of AMCs20

4Stir Casting25

5Diagram of Set up27


Table no.Name of tablePage no.

1Typical reinforcements used in metal matrix composites16

2A comparative evaluation of the different techniques used for MMC fabrication22

3Chemical Composition of A6063 alloy25

4Result & discussion27

ABSTRACT Manufacturing of aluminum alloy based casting composite by stir casting is one of the most economical method of processing MMC. The aluminum based composites are increasingly being used in the transport, aerospace, marine, automobile and mineral processing industries, owing to their improved strength, stiffness and wear resistance properties. The widely used reinforcing materials for these composites are silicon carbide, aluminum oxide and graphite in the form of particles or whiskers. The ceramic particles reinforced aluminum composites are termed as new generation material and these can be tailored and engineered with specific required properties for specific application requirements. Particle reinforced composites have a better plastic forming capability than that of the whisker or fiber reinforced ones, and thus they have emerged as most sought after material with cost advantage and they are also known for excellent heat and wear resistance applications .Given the factors of reinforcement type, form, and quantity, which can be varied, in addition to matrix characteristics, the composites have a huge potential for being tailored for particular applications. One factor that, to date, has restricted the widespread use of MMCs has been their relatively high cost. This is mostly related to the expensive processing techniques used currently to produce high quality composites. The most widely applied methods for the production of composite materials and composite parts are based on casting techniques such as the stir casting of porous ceramic pre - forms with liquid metal alloys and powder metallurgy methods. The cost and the properties of the produced MMC are highly dependent on the method of their processing. INTRODUCTION Aluminum alloys are preferred engineering material for automobile, aerospace and mineral processing industries for various high performing components that are being used for varieties of applications owing to their lower weight, excellent thermal conductivity properties. The composites formed out of aluminum alloys are of wide interest owing to their high strength,fracture toughness, wear resistance and stiffness. Further these composites are of superior in nature for elevated temperature application when reinforced with ceramic particle [1].Alluminium and its alloys are being widely used as matrix for the synthesis of metal matrix composites (MMCs) by researchers, owing to their abundant availability, easy processing, low melting point and easy machining. In the world of polymer matrix composites, and plastics, Al and its alloys maintain their critical importance due to characteristic properties of metals i.e. ductility, strength and, thermal and electrical conductivity [1]. Higher strength to weight ratio, ease in alloying and recycling are added advantages of Al and its alloys. [2]

The addition of high strength, high modulus refractory particles to a ductile metal matrix produce a material whose mechanical properties are intermediate between the matrix alloy and the ceramic reinforcement. Metals have a useful combination of properties such as high strength, ductility and high temperature resistance, but sometimes have low stiffness, whereas ceramics are stiff and strong, though brittle. Aluminium and silicon carbide, for example, have very different mechanical properties: Young's moduli of 70 and 400 GPa, coefficients of thermal expansion of 24 X 10-6 and 4 X 10-6/oC, and yield strengths of 35 and 600 MPa, respectively. By combining these materials, e.g. A6061/SiC/17p (T6 condition), an MMC with a Young's modulus of 96.6 GPa and yield strength of 510 MPa can be produced [3]. By carefully controlling the relative amount and distribution of the ingredients of a composite as well as the processing conditions, these properties can be further improved.COMPOSITE

Composite material are materials made from two or more constituent materials with significantly different physical and chemical properties, that when combined, produce a material with characteristics different from the individual component.[4] Many of common materials (metals, alloys, doped ceramics and polymers mixed with additives) also have a small amount of dispersed phases in their structures, however they are not considered as composite materials since their properties are similar to those of their base constituents (physical property of steel are similar to those of pure iron) . Favorable properties of composites materials are high stiffness and high strength, low density, high temperature stability, high electrical and thermal conductivity, adjustable coefficient of thermal expansion, corrosion resistance, improved wear resistance etc. composite materials are generally used for buildings, bridges and structures such as boat hulls, swimming pool panels, race car bodies, shower stalls, bathtubs, storage tanks, imitation granite and cultured marble sinks and counter tops. the most advanced examples perform routinely on spacecraft and aircraft in demanding environments.Composites as engineering materials normally refer to the material with the following characteristics:

1. These are artificially made (thus, excluding natural material such as wood).

2. These consist of at least two different species with a well defined interface.

3. Their properties are influenced by the volume percentage of ingredients.

4. These have at least one property not possessed by the individual constituents.

Performance of Composite depends on:

1. Properties of matrix and reinforcement,2. Size and distribution of constituents,

3. Shape of constituents,

4. Nature of interface between constituents.

CLASSIFICATION OF COMPOSITESComposite materials are classified

a. On the basis of matrix material,

b. On the basis of filler material.

Fig1: Classification of composites(a) On the basis of Matrix:

1. Metal Matrix Composites (MMC)

Metal Matrix Composites are composed of a metallic matrix (aluminium, magnesium, iron, cobalt, copper) and a dispersed ceramic (oxides, carbides) or metallic (lead, tungsten, molybdenum) phase.

2. Ceramic Matrix Composites (CMC)

Ceramic Matrix Composites are composed of a ceramic matrix and imbedded fibers of other ceramic material (dispersed phase).

3. Polymer Matrix Composites (PMC)

Polymer Matrix Composites are composed of a matrix from thermoset (Unsaturated polyester (UP), Epoxy) or thermoplastic (PVC, Nylon, Polysterene) and embedded glass, carbon, steel or Kevlar fibers (dispersed phase).

(b) On the basis of Material Structure:

1. Particulate Composites

Particulate Composites consist of a matrix reinforced by a dispersed phase in form of particles.

1. Composites with random orientation of particles.

2. Composites with preferred orientation of particles. Dispersed phase of these materials consists of two-dimensional flat platelets (flakes), laid parallel to each other.

2. Fibrous Composites

(a) Short-fiber reinforced composites. Short-fiber reinforced composites consist of a matrix reinforced by a dispersed phase in form of discontinuous fibers (length < 100*diameter).

Composites with random orientation of fibers.

Composites with preferred orientation of fibers.

(b) Long-fiber reinforced composites. Long-fiber reinforced composites consist of a matrix reinforced by a dispersed phase in form of continuous fibers.

Unidirectional orientation of fibers.

Bidirectional orientation of fibers (woven).

Laminate Composites

When a fiber reinforced composite consists of several layers with different fiber orientations, it is called multilayer (angle-ply) composite.3.Laminar Composites

Laminar composites are found in as many combinations as the number of materials. They can be described as materials comprising of layers of materials bonded together. These may be of several layers of two or more metal materials occurring alternately or in a determined order more than once, and in as many numbers as required for a specific purpose.

METAL MATRIX COMPOSITES (MMCs) Metal matrix composites, at present though generating a wide interest in research fraternity, are not as widely in use as their plastic counterparts. High strength, fracture toughness and stiffness are offered by metal matrices than those offered by their polymer counterparts. They can withstand elevated temperature in corrosive environment than polymer composites. Metal Matrix Composites are composed of a metallic matrix (Al, Mg, Fe, Cu etc) and a dispersed ceramic (oxide, carbides) or metallic phase ( Pb, Mo, W etc). Ceramic reinforcement may be silicon carbide, boron, alumina, silicon nitride, boron carbide, boron nitride etc. whereas Metallic Reinforcement may be tungsten, beryllium etc [4]. MMCs are used for Space Shuttle, commercial airliners, electronic substrates, bicycles, automobiles, golf clubs and a variety of other applications. From a material point of view, when compared to polymer matrix composites, the advantages of MMCs lie in their retention of strength and stiffness at elevated temperature, good abrasion and creep resistance properties [4]. Most MMCs are still in the development stage or the early stages of production and are not so widely established as polymer matrix composites. The biggest disadvantages of MMCs are their high costs of fabrication, which has placed limitations on their actual applications [2]. There are also advantages in some of the physical attributes of MMCs such as no significant moisture absorption properties, non-inflammability, low electrical and thermal conductivities and resistance to most radiations [5]. MMCs have existed for the past 30 years and a wide range of MMCs have been studied. Compared to monolithic metals, MMCs have:

Higher strength-to-density ratios

Higher stiffness-to-density ratios

Better fatigue resistance Better elevated temperature properties

Higher strength Lower creep rate Lower coefficients of thermal expansion

Better wear resistance

The advantages of MMCs over polymer matrix composites are:

Higher temperature capability

Fire resistance Higher transverse stiffness and strength

No moisture absorption

Higher electrical and thermal conductivities

Better radiation resistance

No out gassing

Fabric ability of whisker and particulate-reinforced MMCs with conventional metalworking equipment.

Some of the disadvantages of MMCs compared to monolithic metals and polymer matrix composites are:

Higher cost of some material systems

Relatively immature technology

Complex fabrication methods for fiber-reinforced systems (except for casting) Limited service experienceNumerous combinations of matrices and reinforcements have been tried since work on MMC began in the late 1950s. However, MMC technology is still in the early stages of development, and other important systems undoubtedly will emerge. Numerous metals have been used as matrices. The most important have been aluminum, titanium, magnesium, and copper alloys and superalloys.

CONSTITUENTS OF MMC The major constituents of a metal matrix composite material are matrix and reinforcements. Interface between matrix and reinforcement is also considered as one of the constituents as it plays a crucial role in determining the properties of the composite.MATRIX: Metals are essential constituent for fabrication of MMC and choice of matrix

material depends upon strength, temperature of application, density, cost requirement, easy availability and ease of processing .The major function of matrix is to transfer and distribute the load over the reinforcement. The transfer of load depends on the bonding interface between the matrix and the reinforcement, however bonding depends on the type of matrix and the reinforcement along with fabrication technique. Currently the main focus on matrix material for MMC is given to Aluminium alloys because of unique combination of high corrosion resistance, low density and excellent mechanical properties [6].REINFORCEMENT: Second phase materials added to the matrix alloys which normally enhance strength, stiffness, wear and creep resistances of the composites. The choice of reinforcement always depends on the final property requirements of the composite system or the component to be fabricated [6]. SiC has been reported to be the most advantageous reinforcement for matrix of Aluminium alloys . The key properties of Sic are as under:

High strength

Low thermal expansion

High thermal conductivity

High hardness

High elastic modulus

Excellent thermal shock resistance

Superior chemical inertness [7].INTERFACE: It is the region that lies between its constituents i.e. matrix and reinforcement. It plays a crucial role in determining the composite properties. It may contain a simple row of atomic bonds (e.g. the interface between alumina and pure Al), or reaction products between matrix and the reinforcement (e.g. Aluminium carbide between Al and C fibers), or reinforcement coatings (e.g. reinforcement coatings between SiC and titanium matrices). In comparison (i) stiffening and strengthening rely on load transfer across the interface, (ii) toughness is influenced by crack detection/fiber pullout, and (iii) ductility is affected by relaxation of peak stresses near the interface [6].TYPES OF METAL MATRIX COMPOSITES

There are three kinds of metal matrix composites (MMCs):

Particle reinforced MMCs

Short fiber or whisker reinforced MMCs

Continuous fiber or sheet reinforced MMCs

Table provides examples of some important reinforcements used in metal matrix composites and their aspect (length/diameter) ratios and diameters.

TypeAspect RatioDiameter, mExamples

Particle~ 1 41 25SiC, Al2O3, BN, B4C

Short fiber or whisker~ 10 10000.1 25SiC, Al2O3, Al2O3 + SiO2, C

Continuous fiber> 10003 150SiC, Al2O3, C, B, W

Table 1: Typical reinforcements used in metal matrix composites [8]Particle or discontinuously reinforced MMCs have become very important because they are inexpensive with respect to continuous fiber reinforced composites and they have relatively isotropic properties compared to fiber reinforced composites.

Fig 1 (a) Typical microstructure of continuous alumina fiber/magnesium alloy composite (b) Typical microstructure of silicon carbide particle/ aluminum alloy composite [8]INTRODUCTION TO ALUMINIUM MATRIX COMPOSITES Aluminium is the most popular matrix for the metal matrix composites (MMCs). The Al alloys are quite attractive due to their low density, their capability to be strengthened by precipitation, their good corrosion resistance, high thermal and electrical conductivity, and their high damping capacity. Aluminum matrix composites (AMCs) have been widely studied since the 1920s and are now used in sporting goods, electronic packaging, armours and automotive industries. AMC material systems offer superior combination of properties (profile of properties) in such a manner that today no existing monolithic material can rival. Over the years, AMCs have been tried and used in numerous structural, non-structural and functional applications in different engineering sectors. Driving force for the utilisation of AMCs in these sectors include performance, economic and environmental benefits. The key benefits of AMCs in transportation sector are lower fuel consumption, less noise and lower airborne emissions. With increasing stringent environmental regulations and emphasis on improved fuel economy, use of AMCs in transport sector will be inevitable and desirable in the coming years.[25] They are usually reinforced by Al2O3, SiC, C but SiO2, B, BN, B4C, AlN may also be considered. The aluminum matrices are in general Al-Si, Al-Cu, 2xxx or 6xxx alloys as proposed by the American Aluminum Association the AMCs should be designated by their constituents: accepted designation of the matrix/abbreviation of the reinforcements designation / arrangement and volume fraction in % with symbol of type (shape) of reinforcement. For example, an aluminum alloy AA6061 reinforced by particulates of alumina, 22 % volume fraction, is designated as "AA6061/Al2O3/22p". In the 1980s, transportation industries began to develop discontinuously reinforced AMCs. They are very attractive for their isotropic mechanical properties (higher than their unreinforced alloys) and their low costs (cheap processing routes and low prices of some of the discontinuous reinforcement such as SiC particles or Al2O3 short fibers) [9]. Some of the examples are shown in Fig. 2:1. Cast SiCp/Al attachment fittings multi-inlet fitting for a truss node.

2. Brake rotors for German high speed train ICE-1 and ICE-2 developed by Knorr Bremse AG and made from a particulate reinforced aluminum alloy (AlSi7Mg + SiC particulates) supplied by Duralcan. Compared to conventional parts made out of cast iron with 120 kg/piece, the 76 kg of the AMC rotor offers an attractive weight saving potential.

3. The braking systems (discs, drums, calipers or back-plate) of the New Lupo from Volkswagen made from particulate reinforced aluminum alloy supplied by Duralcan.

4. AMC continuous fiber reinforced pushrods produced by 3M for racing engines. These pushrods weigh 40% as much as steel, are stronger and stiffer, and have high vibration damping.

5. AMC wires also developed by 3M for the core of electrical conductors. The unique properties of this type of conductor offer substantial performance benefits when compared to the currently used steel wire reinforced conductors.

PRODUCTION METHODS OF ALUMINIUM MATRIX COMPOSITESMany processes for fabricating aluminium matrix composites are available. For the most part, these processes involve processing in the liquid and solid state. Some processes may involve a variety of disposition technique or an in situ process of incorporating a reinforcement phase.

1. Liquid state processes

a. Stir casting

b. Squeeze infiltration

c. Spray disposition

d. Reactive processing

2. Solid state processes

a. Powder blending and consolidation

b. Diffusion Bonding of foils

3. Physical vapor deposition

Stir casting: This involves incorporation of ceramic particulate into liquid aluminummelt and allowing the mixture to solidify. Here, the crucial thing is to create good wetting

between the particulate reinforcement and the liquid aluminum alloy melt. The simplest and

most commercially used technique is known as vortex technique or stir-casting technique.

The vortex technique involves the introduction of pre-treated ceramic particles into the vortex

of molten alloy created by the rotating plate.Infiltration process: Liquid aluminum alloy is injected/infiltrated into the interstices

of the porous pre-forms of continuous fiber/short fiber or whisker or particle to produce

AMCs. The process is widely used to produce aluminum matrix composites

having particle/whisker/short fiber/continuous fiber as reinforcement.

Spray deposition: Spray deposition techniques fall into two distinct classes, depending

whether the droplet stream is produced from a molten bath (Osprey process) or by continuous

feeding of cold metal into a zone of rapid heat injection (thermal spray process).

The spray process has been extensively explored for the production of AMCs by injecting

ceramic particle/whisker/short fibre into the spray. AMCs produced in this way often exhibit

inhomogeneous distribution of ceramic particles.

In-situ processing (reactive processing): There are several different processes that

would fall under this category including liquid-gas, liquid-solid, liquid-liquid and mixed salt

reactions. In these processes refractory reinforcement are created in the aluminium alloy


Powder blending and consolidation (PM processing): Blending of aluminium alloypowder with ceramic short fibre/whisker particle is versatile technique for the production of

AMCs. Blending can be carried out dry or in liquid suspension. Blending is usually followed

by cold compaction, canning, degassing and high temperature consolidation stage such as

hot isostatic pressing (HIP) or extrusion.Diffusion bonding: Diffusion Bonding of foils (foil fiber foil) is quite oriented towards Titanium and Titanium based matrices. Titanium reinforced with long fibers is commercially produced by the placement of arrays of fibers between thin metallic foils, often involving a filament winding operation, followed by hot pressing. One of the main problems lies in avoiding excessive chemical reaction at the fiber/metal interface. In general, the foil fiber foil route is cumbersome and obtaining high fiber volume fraction and homogeneous fiber distribution is difficult unless special techniques are used. Also the process becomes difficult when the objective is to produce parts of complex shape.

Physical vapour deposition: Physical vapor deposition is a vapor state processing method for MMC. The evaporation process is used for fabrication of Titanium reinforced by monofilaments. It involves passing the fiber through a region having high vapor pressure of the metal to be deposited, where condensation takes place to produce a thick surface coating. The vapor is produced by directing a high power electron beam onto the end of a solid bar feed stock. There is little or no mechanical disturbance of the interfacial region and very uniform distribution of fibers is produced. The fabrication of composite is usually completed by assembling the coated fibers into a bundle and consolidating by HIP. The fiber volume fraction can be accurately controlled via the thickness of the deposited coatings and the fiber distribution is always very homogenous.

Casting, or liquid infiltration, involves infiltration of a fiber bundle by liquid metal. It is not easy to make MMCs by simple liquid phase infiltration, mainly because of difficulties with wetting of ceramic reinforcement by molten metal. Squeeze infiltration involves injection of liquid metal into the interstices of an assembly of short fibers, usually called a preform. Composites fabricated with this method have minimal reaction between the reinforcement and the molten metal because of short dwell time at high temperature and are free from common casting defects such as porosity and shrinkage cavities.MethodRange of shape and sizeMetal yieldRange of volume fractionDamage to reinforcementCost

Stir castingWide range of shapes, larger size; upto 500 kgVery high, >90%Up to 0.3No damageLeast expensive

Squeeze castinglimited to perform shape; upto 2 cm heightLowUp to 0.45Severe damageModerately expensive

Powder MetallurgyWide range; restricted sizeHigh-Reinforcement fractureExpensive

Spray DepositionLimited shape; large sizeMedium0.3 0.7-Expensive

Table 2: A comparative evaluation of the different techniques used for DRMMC fabrication [11]According to Skibo et al. [10], the cost of preparing composites material using a casting method is about one-third to half that of competitive methods, and for high volume production, it is projected that the cost will fall to one-tenth.

Among the variety of manufacturing processes available for discontinuous metal matrix composites, stir casting is generally accepted as a particularly promising route, currently practiced commercially. Its advantages lie in its simplicity, flexibility and applicability to large quantity production. It is also attractive because, in principle, it allows a conventional metal processing route to be used, and hence minimizes the final cost of the product. This liquid metallurgy technique is the most economical of all the available routes for metal matrix composite production, and allows very large sized components to be fabricated. However, there are some common problems associated with production of MMCs by this method such as poor reproducibility, porosity, non uniform distribution of particles in the matrix and rejection of dispersoids by the melt [12]. Moreover, to overcome some of these problems, scientists and people all over the world used SQUEEZE casting. It is proved that proper and controlled stirring followed by squeezing of the material will certainly results in reduction in defects like porosity. [13][18][19]EXPERIMENTAL SET UP AND PROCEDURESTIR SQUEEZE CASTING SET UP:

In this study, Al-SiCp MMC ingots were fabricated through rapid quenching in a stir casting unit. The schematic drawing of the caster is shown in Fig. 3. Al-6063 aluminium alloy in form of rods was used as the matrix metal. The furnaces is open hearth furnace. Graphite crucibles were used and the stirrer rods and the impeller were made of stainless steel. The stirrer is used for better mixing of al 6063 and SiCp. The temperature varies over range of 0 1200oC . The quick quenching unit consisted of a large mild steel vessel for holding water as quenching medium.




The chemical composition of A6063 alloy is given as:COMPONENTWt. %

Si0.2 0.6




Mg0.45 0.9





Table 3: Chemical Composition of A6063 alloySTIR CASTING PROCEDURE:

As mentioned above, two open hearth furnaces were incorporated for the process. Furnace A was fed with 20m silicon carbide particles (15% and 20%) in a graphite crucible and was brought to a temperature of around 1000 1100oC. This was done so that the SiC particles will be at the same temperature when added to the melt and it was also targeted on the removal of any trapped gases inside the SiC particles so as to reduce oxidation. The carbide particles were heated side by side until Al ingots melt. Meanwhile, furnace B was charged with the Al alloy rods (approx. 85% and 80% by weight). The temperature of the furnace was increased gradually above 700oC so that the alloy would come in liquid form.When the alloy is completed melted Mg was added into the melt before the stirring action so as to increase the wettability of the Al particles as Mg is a well known wetting agent [12]. Mg ribbon (3% by weight) were wrapped in Al foil and were introduced inside the melt. After introducing the Mg ribbon wait for a minute. Then put down the graphite crucible from the open hearth furnace. Immediately stirrer rod with impeller is put in and start rotating it. Also drop the heated SiC powder into it continuously with constant speed.The suction created by the nature of the vortex formed will fed the SiC particles inside the melt. The continuous rotation of the impeller will apply a centrifugal force on the carbide particles and they will be pushed towards the wall of the crucible. As the density of the carbide particles is larger than the density of Al particles, they will have a tendency of settling down or agglomerate. But the size of the carbide particles is very small, therefore they will come on the upper surface of the melt due to the surface tension. But again, the stirring action and movement of the material due to vortex formation will fed them inside. This stirring was done for around 1 2 minutes so that the SiC particles were properly distributed into the melt. The composite material then poured into mould cavity. Pattern are made in the form of rod. Now we get the composite material in the form of rod and is ready for turning operation.



Izod and Charpy impact testing is a method of determining the impact resistance of materials. An arm held at a specific height (constant potential energy) is released. The arm hits the sample. The specimen either breaks or the weight rests on the specimen. From the energy absorbed by the sample, its impact energy is determined. A notched sample is generally used to determine impact energy and notch sensitivity.

TENSILE TESTTensile testing, also known as tension testing is a fundamental materials science test in which a sample is subjected to a controlled tension until failure. The results from the test are commonly used to select a material for an application, for quality control and to predict how a material will react under other types of forces. Properties that are directly measured via a tensile test are ultimate tensile strength, maximum elongation and reduction in area. From these measurements the following properties can also be determined: Young's modulus Poisson's ratio, yield strength, and strain-hardening characteristicsFARMULA

Strain Energy

Stress Energy


HARDNESS TEST:- Rockwell Hardness TestingHardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and it is determined by measuring the permanent depth of the indentation. More simply put, when using a fixed force (load) and a given indenter, the smaller the indentation, the harder the material. Indentation hardness value is obtained by measuring the depth or the area of the indentationCONCLUSION:Form the study and the experiment, it has been concluded that: Al 6063 alloy MMC reinforced with 15% & 20% SiC has been successfully produced with the help of a conventional Stir Casting set up. The produced MMC was investigated for turning operation on lathe machine. The stirring speed has considerable effect on distribution of the SiC particles. As some amount of particle clustering and absence of SiC was observed. The increase in stirring speed that provided better homogeneous distribution of SiC particles also increased susceptibility of porosity. The hardness of the matrix aluminium alloy is also improved considerably by addition of SiC particles into it.

The measured weight fraction of SiC particles is very close to its actual value so it can be stated that the intended amount of reinforcement is essentially mixed in the matrix alloy and hence the process can be used to produce MMC with good distribution with optimized parameters specially the stirring speed and the weight fraction of the reinforcement particles.

FUTURE ASPECTSAs per the literature survey and the work done, it has been declared that stir casting is the most accepted and promising method which is incorporated commercially. But there are certain limitations of the process as like particle agglomeration, sedimentation of second phase particles (reinforcement components), and porosity.

Incorporation of Squeezing phenomenon and preheating of the SiC particles helped in the reduction of these defects to such extent particularly porosity but still the agglomeration is there.

These defects or limitations can be somewhat eliminated by providing some ultrasonic vibrations to the melt or electromagnetic stirring the melt or combination of both.

Electromagnetic stirring will help the metal melt to flow throughout the entire volume thereof and thereby, can effectively prevents sedimentation of second phase particles.As in case of stir casting, stirring by some impeller or mechanical stirrer is done which allows the striking of abrasive carbide particles with the blades or fins of the stirrer. This causes particle cracking resulting in reduction in size of the particle thus increasing the chances of agglomeration of the particles on the upper surface.This effect can be minimized or almost omitted by the electromagnetic stirring of the system carrying the particles and molten melt. Electromagnetic effect produced by a 3 AC motor creates the rotating effect which can be used for this stirring purpose. This type of stirring will strike out the particle blade striking from the view and will also help in evenly distributed stirring effect in the molten melt thus helping to retain the properties of the abrasive carbides and enhancing the properties of the final composite material. In fact this system can not only retain but enhance the strength, damping and wear resistance properties of the reinforced material. Also the implication of little bit ultrasonic vibrations to the molten melt adds to the proper distribution of the reinforcement particles in the matrix by improving the wettability characteristics.REFERENCES[1] ASM handbook of Composites, Volume 21.[2] T. W. Clyne, Metal Matrix Composites: Matrices and Processing, A Mortensen (ed.) Elsvier, pp. 1 14, 2001.

[3] S. Skolianos, Mechanical behavior of cast SiCp-reinforced Al-4.5%Cu-1.5%Mg alloy, Mater. Sci. Eng. [1996][4] Wikipedia-composite mateials[4] S. Bandyopadhay, T. Das , and P. R. Munroe , Metal Matrix Composites -The Light Yet Stronger Metals For Tomorrow, A Treatise On Cast materials,

P 17 - 38[5] F. L. Matthews and R. D. Rawlings, Composite Materials: Engineering and Design, Chapman & Hall publication, pp. 78 - 80[6] I. A. Ibrahim, F. A. Mohamed, E. J. Lavernia, Particle Reinforced Metal Matrix Composites A Review, Journal of Materials Science, 26, pp. 1137 1156, 1991[7] T. P. D. Rajan, R. M. Pillai, B. C. Pal, Reinforcements coatings and interfaces in Aluminium Metal Matrix Composites, Journal of Materials Science 33, pp. 3491 3503, 1998

[8] Krishan Kumar Chawla, Composite materials: science and engineering, P. 164 166

[9] Doel T. J. A., Lorretto M. H. and Bowen P., Mechanical Properties of Aluminium based Particulate Metal Matrix Composites, Journal of Composites, Vol. 24, pp. 270 275, 1993

[10] D.M. Skibo, D.M. Schuster, L. Jolla, Process for preparation of composite materials containing nonmetallic particles in a metallic matrix, and composite materials, 1988

[11] J. Hashim, L. Looney, M. S. J. Hashmi, Metal matrix composites: production by the stir casting method, Journal of Materials Processing Technology, pp. 1 7, 1999[12] V. Tirth, Development and Micrography of AA2218 Based Heat Treated 5 Wt% Al2O3(TiO2) Hybrid MMCs, MIT International Journal of Mechanical Engineering, Vol. 1, No. 1, pp. 41 48, Jan 2011[13] Akshay Dvivedi, Pradeep Kumar, Inderdeep Singh, Development of new Stir Caster Design for the production of Metal Matrix Composite, Indian Foundry Journal, 54 (2), pp. 21 27, 2008[14] Fang C. K., Fang R. L., Weng W. P., and Chuang T. H., Applicability of Ultrasonic Testing for the Determination of Volume Fraction of Particulates in Alumina Reinforced Aluminium Matrix Composites, Materials Letters, Vol. 23, PP. 217 266, 1999[15] A. Mortensen, Mechanical and Physical Behavior of Metals and Ceramic Compounds, Riso National Laboratory, Roskilde, Denmark, 1988,

[16] J. W. Kaczmar, K. Pietrzak, W. Wlosinski, The production and application of metal matrix composite materials, Journal of Materials Processing Technology 106, pp. 58 67, 2000[17] Adem Onat, Hatem Akbulut, Fevzi Yilmaz, Production and characterisation of silicon carbide particulate reinforced aluminiumcopper alloy matrix composites by direct squeeze casting method, Journal of Alloys and Compounds 436, pp. 375 382, 2007[18] C. S. Lim, A. J. Clegg, The production and evaluation of metal matrix composite castings produced by a pressure assisted investment casting process, journal of materials processing technology 67, pp. 13 18, 1997[19] S. Naher, D. Brabazon, L. Looney, Simulation of stir casting processes, Jr. of Materials Processing Technology, Vol. 143 144, pp. 567 571, 2003[20] G. S. Haumanth, G. A. Irons, Particle incorporation by melt stirring for the production of metal matrix composites, Journal of Materials Science 28, pp. 2459 2465, 1993

[21] G. Ganesan, K. Raghukandan, R. Karthikeyan, B. C. Pai, Development of processing maps for 6061 Al/15% SiC Composite Material, Materials Science and engineering, A369, pp. 230 235, 2004.

[22] J. U. Ejiofor, R. G. Reddy, Developments in the Processing and Properties of Particulate Al Si Composites, JOM, PP. 31 37, Nov. 1997

[23] D. Brabazon, D. J. Browne, A. J. Carr, Mechanical Stir Casting of Aluminium Alloys from the Mushy State: Process, Microstructure and Mechanical Properties, Materials Science and Engineering, A326, pp. 370 381, 2002

[24] Manoj Singla, D. Deepak Dwivedi, Lakhvir Singh, Vikas Chawla, Development of Aluminium Based Silicon Carbide Particulate Metal Matrix Composite, Journal of Minerals & Materials Characterisation & Engineering, Vol. 8, No. 6, pp. 455 467, 2009

[25] M K SURAPPA, Aluminium matrix composites: Challenges and

Opportunities Sadhana Vol. 28, Parts 1 & 2, February/April 2003, pp. 319334.


Fig. 3 Some Applications of AMCs [9]