ICAMB - 1014

8/13/2019 ICAMB - 1014

1/4

ICAMB 2012, Jan 9-11, 2012

SMBS, VIT University, Vellore , India 36

Abstract Composites materials are made from two or moreconstituent materials with significantly different physical or chemical

properties which remain separate and distinct at macroscopic or

microscopic scale even after they are made into a single material.

Metal Matrix Composites have been used due to its high strength to

weight ratio and high temperature resistance. In this paper a modest

attempt has been made to develop aluminium based silicon carbide

particulate MMCs with an objective to develop a conventional low

cost method of producing MMCs and to obtain homogenousdispersion of ceramic material. The applications of MMCs like rotor

blades in aerospace and drive shafts, pistons etc in automotive

industries involves manufacturing and utilization of large number of

components, so the cost should be low and the process should be

easy and simple in order to reduce cost and time. To achieve these

objectives stir casting technique has been adopted and subsequent

property analysis has been made. The stirrer used in this process

consists of automatic feeder which is designed for this purpose

disperses the reinforcement particles uniformly into the aluminiummatrix. The feeder is made of steel alloy (height 83mm, major

diameter 70mm, minor diameter 55mm, diameter of holes 3mm,

thickness 1mm). Aluminium (LM6) and SiC (grit 800) has been

chosen as matrix and reinforcement material. Experimental analysis

have been conducted by varying weight fractions of SiC (5%, 10%,15%, 20%, 25%, 30%), by keeping the temperature constant. With

the increase in weight percentage of SiC the increase in tensile and

hardness and impact strength has been observed. The results indicate

that the developed method is quite successful to obtain uniform

distribution of reinforcement into matrix.

KeywordsMetal Matrix Composites MMCs, Silicon CarbideSiC.

I. INTRODUCTIONHE composite materials have got a widely applications in

all cutting-edge ranges of advanced materials as

aeronautics, automotives, boats, sports parts and medical

devices. A composite is a structural material that consists of

two or more combined constituents that are combined at a

F. T.A.Aswathsaravanan (corresponding author), PG Scholar, Department of

Mechatronics Engineering, Kongu Engineering College, Perundurai,

Erode- 638 052. (E-mail: [email protected]).

S. A.Tony Thomas, Asst. Professor, Department of Mechatronics

Engineering, Kongu Engineering College, Perundurai, Erode- 638 052.

(E-mail:[email protected])

T. Dr.R.Parameshwaran , Professor and Head, Department of Mechatronics

Engineering, Kongu Engineering College, Perundurai, Erode- 638 052.

(E-mail: [email protected]).

macroscopic level and are not soluble in each other. One

constituent is called reinforcing phase and one in which it is

embedded is called the matrix. The reinforcing phase material

may be in the form of fibers, particles or flake. The matrix

phase materials are generally continuous. Few examples of the

naturally found composites include wood, where the ligninmatrix is reinforced with cellulose fibers and bones in which

the bone-salt plates made of calcium and phosphate ions

reinforce soft collagen. The roles of matrixes in compositematerials are to give shape to the composite part, protect the

reinforcements to the environment, transfer loads to

reinforcements and toughness of material, together with

reinforcements. The aims of reinforcements in composites are

to get strength, stiffness and other mechanical properties,

dominate other properties as coefficient of thermal extension,

conductivity and thermal transport. Like all composites,

aluminum-matrix composites are not a single material but a

family of materials whose stiffness, strength, density, thermal

and electrical properties can be tailored. The matrix alloy,

reinforcement material, volume and shape of the

reinforcement, location of the reinforcement and fabrication

method can all be varied to achieve required properties. Theaim involved in designing metal matrix composite materials is

to combine the desirable attributes of metals and ceramics. 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.

The most common matrix materials for Polymer matrix

composites (PMC) are polymers. Polyesters and vinyl esters

are the most widely used and least expensive polymer resin.

The main advantages of PMCs are their low maximum workingtemperature, high coefficient of thermal expansion and

sensitivity to radiation and moisture. The strength and stiffness

are low compared with metals and ceramics.

Metal matrix composites (MMC) can be used at higher

temperature than their base metal counterparts. The

reinforcements in these materials may improve specific

strength, abrasion resistance, creep resistance and dimensional

stability. The MMCs are light weight and resist wear and

thermal distortion, so it mainly used in automobile and

aerospace industry.

An investigation on the liquid state processing

of ceramic reinforced aluminium matrix

composites

T.A. Aswathsaravanan, A. Tony Thomas, R. Parameshwaran

T

8/13/2019 ICAMB - 1014

2/4

ICAMB 2012, Jan 9-11, 2012


One of the main objectives in producing Ceramic matrix

composites (CMC) is to increase the toughness. Ceramic

Materials are resistant to oxidation at elevated temperature.

The developments of CMCs has lagged behind mostly for the

reason that most processing routes involve higher temperature

and are only employed with high temperature reinforcements.

A. Processing of Metal Matrix Composites.The selection of the processing route depends on many

factors including type and level of reinforcement loading and

the degree of micro structural integrity desired). Primary

processes for manufacturing of MMCs can be classified into

two main groups such as solid state processing and liquid state

processing. Powder blending followed by consolidation (PM

processing), diffusion bonding and vapor deposition

techniques comes under solid state processing. Liquid state

processes include stir casting or compo casting, infiltration,

spray casting and in situ (reactive) processing.

B. Selection of Processing Method.Liquid state fabrication of Metal Matrix Composites involves

incorporation of dispersed phase into a molten matrix metal,

followed by its Solidification. In order to provide high level of

mechanical properties of the composite, good interfacial

bonding (wetting) between the dispersed phase and the liquid

matrix should be obtained. Wetting improvement may be

achieved by coating the dispersed phase particles (fibers).

Proper coating not only reduces interfacial energy, but also

prevents chemical interaction between the dispersed phase and

the matrix. Stir casting is one of the most economical and

simplest methods available for the fabrication of the MMC.

Very large numbers of components are also fabricated easily

by this technique. The strength of the materials can be

increased by proper mixing of the particles and the matrix.

II. PROBLEM DESCRIPTIONStir casting of metal matrix composites has many defects

like uneven distribution and porosity. The density of the matrix

and the reinforcement particles vary, so there is sedimentation

of the reinforcing particles at the bottom of the crucible. These

defects can be overcome by reducing the particle size of the

ceramic particles and by stirring the molten metal after

spreading the ceramic particles evenly into the matrix. An

automatic feeder is designed and is attached with the stirrer.

The feeder disperses the SiC particles evenly into the

aluminium matrix by the centrifugal force that is created due to

the rotation of the stirrer. The defect like porosity can bedecreased by reducing the particle size of the silicon carbide

particles. The particle size of the reinforcement must be small

for maximum strength.

A. Design of FeederFeeder is used to feed the SiC particles in the molten

aluminium. In existing system the feeder fed the SiC particles

in localized manner. So the mixing of SiC particles in the

molten aluminium only depends on the stirrer performance.

Two things must be fulfilled such as feeding of SiC particles in

uniformly manner and controlling the rate of feeding. The

feeder is designed in funnel shaped in order to achieve the

above tasks. The funnel shaped feeder has holes on its body.

SiC particles fed through the holes. This funnel shaped feeder

is attached in the rod and due to the angular motion of the rod

the particles inside the feeder which is stored already has

centrifugal acceleration and tries to escapes from the feeder.

Holes on the body surface of feeder helps to spray the particles

uniformly.

Feeder Specifications

Material : steel alloy

Height : 83 mm

Major diameter : 70 mm

Minor diameter : 55 mm

Diameter of holes : 3 mm

Thickness : 1 mm

B. Design of StirrerStirrer is used to mix the SiC particles in molten aluminium.

Stirrer in the existing system stirs the SiC particles by

providing minimum amount of stirring force which is

inefficient. So the stirrer is modified to make various flow

patterns to achieve uniform distribution of SiC and dimensions

of the stirrer is modified to increase the stirring force by which

cluster formations can be reduced. The stirrer has two blade

assemblies which are namely upper and lower blade assembly.

These two blades are placed in anti parallel manner. The

complex flow pattern makes the SiC particles to mix uniformly

and reduces the formation of cluster.

Stirrer Specifications

Material : steel

Height : 36 mm

Diameter : 65 mm

Blade width : 18 mmBlade breadth : 25 mm

Overview of Experimental Setup

8/13/2019 ICAMB - 1014

3/4

ICAMB 2012, Jan 9-11, 2012


Experimental setup consists of electric furnace which is used

to melt the aluminium ingots. This electric furnace is fully

covered in order to avoid heat loss by convection.

Temperature of the electric furnace is monitored by a

thermocouple. This thermocouple measurement is input to

controller unit which controls temperature at the set value.

Feeder and stirrer is fitted in a rotating rod which is connected

to the electric motor. The whole set of feeder, stirrer and

electric motor is kept exactly centre of the crucible and abovethe furnace.

III. METHODOLOGYStir Casting is a liquid state method of composite materials

fabrication, in which a dispersed phase (ceramic particles, short

fibers) is mixed with a molten matrix metal by means of

mechanical stirring. Initially the aluminium material is kept in

the crucible allowed to melt. The temperature of the crucible is

set at 900oc. while stirring because of the heat loss the

temperature of molten aluminium will become 800oc. Now the

stirrer is placed in the molten aluminium in such a way that

30% of the molten aluminium is below the stirrer. Feeder isstored by SiC particles and motor is allowed to rotate for ten

minutes and then the stirrer is removed. The liquid composite

material is then cast by conventional casting methods. First of

all stirring system has been developed by coupling motor with

gearbox and a mild steel stirrer. All the melting was carried out

in a graphite crucible in an Electric furnace. The furnace

temperature was first raised above the liquid to melt the alloy

scraps completely and was then cooled down just below the

liquid to keep the slurry in a semi-solid state. At this stage the

Sic particles were added and mixed. In the final mixing

process, the furnace temperature was controlled within 760

1000oC. Pouring of the composite slurry has been carried out

in the sand mould prepared according to the specifications forhardness, tensile and impact test specimens.

IV. RESULTS AND DISCUSSIONSA. Brinell Hardness Test

Comparison of BHN Test

Experiments have been conducted by varying weight

fraction of silicon carbide (5%, 10%, 15%, 20%, 25%, and

30%). Hardness test has been conducted on each specimen

using a load of 187.5 kg and a steel ball of diameter 2.5 mm

as indenter.

The hardness value is higher for the specimen-6 (25%

SiC) and it decreases on further adding the SiC particles.

This happens due to the uneven distribution of the particles

and sedimentation of the particles below the melt. Because

of increasing weight of the SiC, the particles agglomerate at

the bottom of the crucible. This occurs after the addition of

SiC above 25%.

B. Impact strength test

Comparison of Impact Strength Test

The specimen-6 (Al + 25%SiC) has the maximum impact

strength. It can be achieved by mixing the reinforcing particles

and molten metal continuously. The SiC particles must be

distributed uniformly into the matrix. These results are

obtained by mixing the slurry evenly. The value increases

gradually on increasing the weight proportion of the silicon

carbide.

C. Tensile TestSpecimen Preparation

ASTM E8 standard specimen is used to make tensile test on

Aluminium alloys which is shown in Figure. Required

specimen is prepared from work piece.

ASTM E8 Standard Specimen

Tensile test is taken to measure the strength of aluminium

MMC. Tensile test is done by UTM computerized tensile

testing machine. The specimen is loaded in the machine and

the stress value is collected from the system.

8/13/2019 ICAMB - 1014

4/4

ICAMB 2012, Jan 9-11, 2012


162

168

172

178.8181.6

187

165

145

150

155

160

165

170

175

180

185

190

Pure

LM6

Al+5%

SiC

Al+10%

SiC

Al+15%

SiC

Al+20%

SiC

Al+25%

SiC

Al+30%

SiC

Stress(Mpa)

Comparison of Stress values

V. CONCLUSIONThe stir casting process is selected for the fabrication of the

aluminium matrix composites since it is the most simple and

low cost method. The experimental investigations on various

specimens of varying weight proportion of SiC is carried outand it is found that silicon carbide particles does not mix

properly with the matrix beyond 25%. This is because of the

sedimentation of the SiC particles in the bottom of the

crucible. The results of the study suggest that with increase in

composition of SiC there will be an increase in hardness and

impact strength. The best results are obtained at 25% weight

fraction of 800 grit size SiC particles.

REFERENCES

[1] Agarwal V. and Dixit D. (1981) Fabrication of Aluminium BaseComposite by Foundry Technique, Japan, Vol 22 No.8, pp. 521-526.

[2] Balasivanandha S. kaarunamoorthy L . kaithiresan S. and Mohan B.(2006) Influencing of stirring speed and stirring time on distribution ofparticles in cast metal matrix composite , Journal Of Material

Processing Technology, Vol 171, pp 268-273.

[3] Clyne T. and Withers P. (1995) An Introduction to Metal MatrixComposites, Cambridge, pp 1-10.

[4] Dasgupta R. and Meenai H. (2005) SiC Particulate DispersedComposites of an Al-Zn-Mg-Cu Alloy, Property Comparison with

Parent Alloy, Vol. 54, pp 438-445.

[5] Lee I.S. Hsu C.J. Chen C.F. Ho N.J. and Kao P.W. (2011) ParticleReinforced Aluminium Matrix Composites Produced from Powder

mixtures Via Friction Stir Processing, Journal of composites Science

and Technology, pp 693-698.

[6] Manoj Singla. Deepak Dwivedi d and Lakhvir Singh. (2009)Development of Aluminium based SiC Particulate MMC, Journal of

minerals and materials, pp 325-358.

[7] Masounave J and Hamel F.G. (1990)Fabrication of particulatereinforced Metal Composites, Canada, pp 79-86.

[8] Meyers Marc A. Chawla Krishan Kumar (1998) Mechanical Behaviorsof Materials Prentice Hall.

[9] McCoy J.W. Jones C and Warner F.E. (1988)Preparation andProperties of cast Ceramic/Aluminium Composites, Vol.19 No.2, pp

37-50.

[10]Naher S. Brabazon D. and Looney L. (2003), Simulation of the stircasting process, Journal of Materials Processing Technology, Vol. 143-

144, pp. 567-571.

[11] Rajesh Kumar Bhushan and Sudhir Kumar (2010) Influence of SiCparticles Distribution and their weight Percentage on 7075 Al alloy,

Sanfrancisco, pp 165-174.

[12] Rajesh Kumar Bhushan and Sudhir Kumar. Das S (2010)Effect ofMachining Parameters on Surface Roughness and Tool Wear for 7075

Al Alloy SiC Composite, International Journal of Advanced

manufacturing Technology, pp 459-469.

[13] Ralph B. Yuen H.C. and Lee W.B. (1997) The processing of MetalMatrix Composites- an Overview, Journal of Material Process

Technology, Vol.63, pp 339-353.

[14] Seo Y.H. and kang C.G. (1999) Effects of Hot Extrusion through aCurved Die on the Mechanical Properties of SiC/Al Composites

Fabricated by Melt Stirring, Journal of Composite Science and

Technology, Vol.59, pp 643-654.

[15] Sharma P C. (2007) Production Technology-Manufacturing processesS.Chand and Company limited, New Delhi.

[16] Sornakumar T. and Marimuthu Kathiresan. (2010)Machining studiesof Die Cast aluminium alloy Silicon Carbide Composites International

Journal of Minerals, Metallurgy and Minerals, Vol. 17, pp 648-653.

[17] Vijayaram T.R. Sulaiman S. Hamouda A.M.S. and Ahmad M.H.M.(2005) Fabrication of Fiber reinforced Metal Matrix Composites by

Squeeze Casting Technology, Journal of Material Processing

Technology, Vol 178, pp 34-38.

[18] Sharma P C. (2007) Production Technology-Manufacturing processesS.Chand and Company limited, New Delhi.

[19] Wannasin, J. (2005), Fabrication of metal matrix composites by a high-pressure centrifugal infiltration process, Journal of Materials

Processing Technology, Vol. 169, pp.143-149.

Documents

ICAMB - 1014