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STUDY OF WEAR BEHAVIOUR OF ALUMINIUM BASED COMPOSITE FABRICATED BY STIR CASTING TECHNIQUE Amardeep Singh 1 *, Ajay Singh Rana 2 and Niraj Bala 3 *Corresponding Author: Amardeep Singh, [email protected] Aluminium based Matrix Composites (AMCs) possess tremendous potential for number of applications in addition to their present uses in different engineering fields. In the present study, aluminium composite with 5% reinforcement of Al 2 O 3 + fly-ash was prepared using a cost effective stir casting technique. Hardness tests carried on the composite using Rockwell hardness tester showed increase in hardness over the monolithic aluminum metal. Testing of wear behavior was done on pin on disc apparatus at a normal load of 40 N and sliding velocities of 0.8 m/sec and 1 m/sec. The fabricated composites showed improvement in wear resistance over the monolithic aluminum metal. Considering all the factors, it can be concluded that aluminium based composite with 5% Al 2 O 3 + fly-ash reinforcement possess better mechanical and wear resistance properties than rival specimen, i.e., pure aluminium. Keywords: Aluminium composites, Fly-ash, Al 2 O 3 , Stir casting, Wear INTRODUCTION Metal Matrix Composites (MMCs) have been in existence since the 1960s, but their commercial applications have been limited due to their higher cost and lack of proper understanding. The motto to design MMC’s is to combine the Metals and Ceramics, i.e., addition of high strength, high modulus refractory particles to ductile metal matrix [We Energies]. ISSN 2278 – 0149 www.ijmerr.com Vol. 4, No. 1, January 2015 © 2015 IJMERR. All Rights Reserved Int. J. Mech. Eng. & Rob. Res. 2015 1 Research Scholar, Department of Mechanical Engineering, RIMTIET , Mandi Gobindgarh, Punjab, India. 2 Associate Professor, Department of Mechanical Engineering, RIMTIET, Mandi Gobindgarh, Punjab, India. 3 Assistant Professor, Department of Mechanical Engineering, BBSBEC, FGS, Punjab, India. The selection of process of manufacturing of MMCs depends on shape and size, nature of matrix and reinforcements. Most metals have been explored for the matrix including aluminium, beryllium, magnesium, titanium, cobalt and silver. However Aluminium is by far the most preferred (Singh, 2012). For reinforcements, ceramics are mostly used, which provide a very beneficial combination of stiffness, strength and. Research Paper
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Int. J. Mech. Eng. & Rob. Res. 2015 Amardeep Singh et al., 2015

STUDY OF WEAR BEHAVIOUR OF ALUMINIUMBASED COMPOSITE FABRICATED BY STIR

CASTING TECHNIQUE

Amardeep Singh1*, Ajay Singh Rana2 and Niraj Bala3

*Corresponding Author: Amardeep Singh,[email protected]

Aluminium based Matrix Composites (AMCs) possess tremendous potential for number ofapplications in addition to their present uses in different engineering fields. In the present study,aluminium composite with 5% reinforcement of Al2O3 + fly-ash was prepared using a cost effectivestir casting technique. Hardness tests carried on the composite using Rockwell hardness testershowed increase in hardness over the monolithic aluminum metal. Testing of wear behaviorwas done on pin on disc apparatus at a normal load of 40 N and sliding velocities of 0.8 m/secand 1 m/sec. The fabricated composites showed improvement in wear resistance over themonolithic aluminum metal. Considering all the factors, it can be concluded that aluminiumbased composite with 5% Al2O3 + fly-ash reinforcement possess better mechanical and wearresistance properties than rival specimen, i.e., pure aluminium.

Keywords: Aluminium composites, Fly-ash, Al2O3, Stir casting, Wear

INTRODUCTIONMetal Matrix Composites (MMCs) have beenin existence since the 1960s, but theircommercial applications have been limited dueto their higher cost and lack of properunderstanding. The motto to design MMC’s isto combine the Metals and Ceramics, i.e.,addition of high strength, high modulusrefractory particles to ductile metal matrix [WeEnergies].

ISSN 2278 – 0149 www.ijmerr.comVol. 4, No. 1, January 2015

© 2015 IJMERR. All Rights Reserved

Int. J. Mech. Eng. & Rob. Res. 2015

1 Research Scholar, Department of Mechanical Engineering, RIMTIET, Mandi Gobindgarh, Punjab, India.2 Associate Professor, Department of Mechanical Engineering, RIMTIET, Mandi Gobindgarh, Punjab, India.3 Assistant Professor, Department of Mechanical Engineering, BBSBEC, FGS, Punjab, India.

The selection of process of manufacturingof MMCs depends on shape and size, natureof matrix and reinforcements. Most metalshave been explored for the matrix includingaluminium, beryllium, magnesium, titanium,cobalt and silver. However Aluminium is by farthe most preferred (Singh, 2012).

For reinforcements, ceramics are mostlyused, which provide a very beneficialcombination of stiffness, strength and.

Research Paper

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Int. J. Mech. Eng. & Rob. Res. 2015 Amardeep Singh et al., 2015

relatively low density. Some of the otherreinforcement materials include SiC, Al2O3,B4C, TiC, TiB2, graphite and number of otherceramics (Singh, 2012).

Varieties of processes have been and arebeing developed for the manufacture of MMCs.Some of them are Sand casting, Stir casting,Die casting, Powder metallurgy, Centrifugalcasting, Squeeze casting, Investment casting,Spray casting, and Liquid metal Infiltration(Singh, 2012). The stir casting process ispreferred because of its low cost, easyadaptability and also near-net shape formationof the composites (Manchang Gui et al.,2003). Stir Casting is a liquid state method ofcomposite materials fabrication, in which adispersed phase (ceramic particles, shortfibers) is mixed with a molten matrix metal bymeans of mechanical stirring. The liquidcomposite material is then cast byconventional casting methods and may alsobe processed by conventional metal formingtechnologies (www.Substech.com, 2013).During solidification of composite, particle-interface interaction plays a major role in theparticle distribution as reported by variousinvestigators or workers (We Energies,Mortensen, 1991; Mortensten et al., 1992;Asthana et al., 1993; and Michaud et al.,1993). The technology is relatively simple andlow cost (Rohatgi et al., 1986).

Aluminum and magnesium are lightweightmaterials, when compared to iron and steel.However, they do not have the strengthrequirements necessary for severalapplications [We Energies]. So a material likean Aluminium Matrix Composite (AMC) havingthe characteristics of both light materials aswell as strong or tough materials like steel

would be much better than the today’smonolithic materials [We Energies].

Aluminium Matrix Composites (AMCs)refer to the class of light weight highperformance aluminium centric materialsystems. Over the years, AMCs have beentried and used in numerous structural, non-structural and functional applications indifferent engineering sectors (Lloyed et al.,1989). Aluminium alloys are widely used in theautomotive industry because of their highstrength to weight ratio as well as high thermalconductivity (Bahera et al., 2007). It is usedparticularly in automobile engines as cylinderliners as well as other rotating andreciprocating parts, such as the piston, driveshafts, covers, pans, shrouds, casings, pulleys,manifolds, valve covers, brake rotors, andengine blocks in automotive, small engine, theelectromechanical industry sectors and inother applications in automotive andaerospace industries [We Energies]. Themajor reasons for the use of AMCs in thesesectors include economic, performance andenvironmental benefits. The key benefits ofAMCs in transportation sector are lower fuelconsumption, improved productivity, lowermaintenance cost, energy savings, less noiseand lower airborne emissions [We Energies].

One of the major characteristics requiredof these AMCs used in the above mentionedareas is wear resistance, i.e., thesecomposites must be wear resistant which theycan be made by the introduction of betterreinforcements like Al2O3, SiC, Fly-ash, etc.

Aluminium matrix composites are generallyreinforced by ceramic particles like SiC butproduction of such composites is quite costly.The alternative to this can be fly ash since it is

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cheaper than SiC and is readily available.Aluminium matrix composite manufactured bythe dispersion or the reinforcement of coal flyash have the potential of being the costeffective and ultra-light composites withimproved mechanical properties such ashardness and abrasion resistance. Fly ashparticles are potential discontinuousdispersoids used in metal matrix composites;they are low-cost and low-densityreinforcement available in large quantities asa waste by-product in thermal power plants(Rajan et al., 2007). Incorporation of fly ashparticles improves the wear resistance,damping properties, hardness and stiffnessand reduces the density of Al alloys. However,these have a disadvantage also thatincorporation of fly ash reduces ductility of thematerial system. The signif icance ofdeveloping aluminium-fly ash composites canbe fully understood only if we consider theoverall benefit to various industries and to theenvironment [We Energies].

So this work concentrates on the productionof low cost aluminum-fly ash-alumina hybridcomposites with a cost effective production orprocessing method stir casting which can beused for mass production, determining theirproperties like hardness, wear behavior etc.and comparing them with monolithic aluminum.The hybrid composite is studied because flyash can be used a replacement for SiC orAl2O3 but it reduces ductility so addition ofAl2O3 can overcome this problem since Al2O3

increases ductility.

METHODOLOGYThe matrix material used in the experimentinvestigation was commercially pure Al withcomposition as listed in Table 1. Thereinforcement consisted of 5% by weight Flyash + Al2O3. Process used for fabrication ofcomposites was Stir casting and the stircasting apparatus consisted of furnace,crucible, stirrer, mould, tools, etc.

A rectangular furnace was used having aheating range of 0°-1200 °C which waselectrically operated. The size number 5crucible of graphite was used with a capacityof up to 2 Kg of aluminium. The Stirrerconsisted of motor, stand, blade with shaft.Motor used is a single phase AC supply, 230V, 300 W motor with a speed range of 250rpm to 1400 rpm however the speed used inthe current investigation was around 500 rpm.

A mild steel mould made by two 1 inch thickplates of dimensions 25 cm x 17 cm was usedwhich consisted of 6 cylindrical grooves of 2cm diameter each with a depth of 8 cm. Thesegrooves were joined at the bottom with agroove of 2 cm diameter and a gap of 1 cmwas provided between each vertical grooveas shown in Figure 1.

Guiding pins and locking arrangement wasalso provided in the mould along with diamondpaste coating inside the grooves for smoothremoval of casted materials. In addition tothese, some other tools like tongs, gloves,unloading tool, pouring tool, etc., were alsoused.

Aluminium Iron Copper Silicon Manganese Zinc Lead Magnesium Nickel Tin

95.58 1.18 1.05 1.02 0.367 0.268 0.144 0.120 0.036 0.051

Table 1: Composition of Material Selected

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So in this investigation, 550 gm ofaluminium is first heated in the furnace upto atemperature of 800 °C and then is allowed tocool down to a temp of about 600 °C to bringit to a semi solid state. Then the 5% by weightreinforcement of Al2O3 and Fly ash (i.e., 2.5%Al2O3 and 2.5% Fly ash) is added into the semisolid melt and is stirred for about half an hourat a speed of around 500 rpm. The melt withreinforced particulates were poured into thepreheated permanent mild steel mould. Themelt was then allowed to solidify in the mould.Specimens were then finish machined to makepins of 6 mm diameter and 30 mm alonglength.

Hardness testing was done on thespecimen using Rockwell hardness testingapparatus while Wear testing was performedon these specimens on a pin on disk weartester. The unit consists of a pivoted arm towhich the pin is attached, a fixture whichaccommodates disks of a particular diameter,an electronic force gauge for measuring thefriction force. Included with the Falex ISC-200PC is a weight set capable of applyingcontacts stresses up to 2 GPa. The motordriven turntable produces up to 180 rpm. Wearwas quantified by varying the parameters like

wear track radius and dead weight keepingthe machine r.p.m constant for a time intervalof 2 minutes. The amount of material removedwas calculated to get the wear rate. The wearrate of Al+ Fly ash + Al2O3 composite was alsocompared with the wear rate of commerciallypure aluminium metal.

RESULTS AND DISCUSSIONThe addition of reinforcements has resulted inthe increase of hardness in aluminium asshown in Table 2. Also, there are a lot ofvariations in hardness values in case of hybridcomposite. At one point, hardness wasmaximum of all the composites while anotherpoint has shown the lowest hardness. This mayhave happened due to the porosity of thecomposite or the agglomeration of theparticles. This porosity or agglomeration mayhave occurred either due to the entrapment ofgases while casting or improper wetting of theas received fly ash particles. 1% Mg by weightwas used as a wetting agent in all thecomposites but fly ash composites mayrequire higher Mg content for proper wetting.

Figure 1: Mould

S. No. Pure Al (RHN) Al + Fly Ash + Al2O3 (RHN)

1. 42 41

2. 33 56

3. 37 38

4. 35 32

Mean 36.75 41.75

Table 2: Hardness of Specimen

The wear tests were done for a normal loadof 40 N at a two sliding velocities of 0.8 m/secand 1 m/sec. The variation of Cumulative WearRate (CWR) and cumulative wear loss withsliding distance has been discussed in thesubsequent paragraphs for the various casesunder investigation.

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Int. J. Mech. Eng. & Rob. Res. 2015 Amardeep Singh et al., 2015

The variation of the cumulative wear ratewith the sliding distance for the pure Al and Al+ Al2O3 + Fly ash composite at a normal loadof 40 N and sliding velocity of 0.8 m/sec hasbeen plotted in Figure 2 whereas the CWRdata have been shown in Figure 3. It is evidentfrom the plots that CWR is high even duringthe start of the process for pure Al. For firstthree cycles, CWR increases steadily for pureAl but for Al + Al2O3 + Fly ash composite rateof increase was higher for third cycle and after

that CWR increases linearly. In case of pureAl, CWR increases linearly for first three cyclesand rate of increase slightly improves for fourthcycle and slightly decreases for fifth cycle whilefor sixth cycle, CWR again increase sharply.The reason for such behavior is that duringinitial phases of wear, oxide film formed on thesurface of pure Al composite may have causedresistance to wear but after its removal, thesurface gets exposed and results in higherwear thereafter. For Al + Al2O3 + Fly ash

Figure 2: Variation of Cumulative Wear Rate for the Pure Al and Al + Al2O3 + Fly AshComposites Subjected to Wear at Normal Load of 40 N and Sliding Velocity of 0.8 m/sec

Figure 3: Cumulative Wear Rate for the Pure Al and Al + Al2O3 + Fly Ash CompositesSubjected to Wear at Normal Load of 40 N and Sliding Velocity of 0.8 m/sec After a

Sliding Distance of 600 m

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Int. J. Mech. Eng. & Rob. Res. 2015 Amardeep Singh et al., 2015

composite, CWR increases linearly for first twocycle and then suddenly increases sharply butafterwards increases linearly. This type ofbehavior may be attributed to the fact thatinitially the contact surfaces are usually roughhaving hills and valleys which get interlockedwith each other during the initial periods ofwear. However with the passage of slidingdistance, these hills and valleys get smoother,contributing to somewhat lower CWR.

Therefore it can be concluded that wearresistance of Al has got increased after the

introduction of reinforcement in it. This meansAl + Al2O3 + Fly ash composite is better on thebasis of wear resistance than pure Al.

The variation of the cumulative wear ratewith the sliding distance for the pure Al and Al+ Al2O3 + Fly ash composite at a normal loadof 40 N and sliding velocity of 1 m/sec has beenplotted in Figure 4 and the CWR data havebeen shown in Figure 5. It is evident from theplots that CWR is higher for pure Al than Al +Al2O3 + Fly ash composite. For pure Al, CWRincreases linearly in all the cycles but the rate

Figure 4: Variation of Cumulative Wear Rate for the Pure Al and Al + Al2O3 + Fly AshComposites at Normal Load of 40 N and Sliding Velocity of 1 m/sec

Figure 5: Cumulative Wear Rate for the Pure Al and Al + Al2O3 + Fly Ash Composites atNormal Load of 40 N and Sliding Velocity of 1 m/sec After a Sliding Distance of 750 m

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of increase was highest in third cycle. Al +Al2O3 + Fly ash composite behaves such thatCWR increases initially with rate of changebeing higher in third cycle and then this rate ofchange suddenly decreases slightly and in lastcycle again increases. From Figure 5, it canbe concluded that Al + Al2O3 + Fly ashcomposite has performed much better than itscounterpart, i.e., pure Al. So, Al + Al2O3 + Flyash composite is better on the basis of wearresistance at a normal load of 40N and slidingvelocity of 1 m/sec.

The comparison of the cumulative wear ratewith the two sliding velocities of 0.8 m/sec and1 m/sec for the Pure Al and Al + Al2O3 + Flyash composite at a normal load of 40 N hasbeen plotted in Figure 6. There was nosignificant effect of change in sliding velocityon CWR of Pure Al and that of Al + Al2O3 + Flyash composite, CWR decreased considerablywith increase of velocity.

So, it can be evaluated that Al + Al2O3 + Flyash composite showed better wear resistanceat sliding velocity of 0.8 m/sec and normal load

of 40 N than pure Al while at 1 m/sec, Al + Al2O3

+ Fly ash composite showed even better wearresistance while for pure Al, wear resistanceremained almost same at the sameparameters.

CONCLUSION1. Al + Al2O3 + Fly ash composite was

successfully fabricated using cost effectivestir casting technique.

2. Hardness of aluminium was found toincrease significantly with the addition ofreinforcement, i.e., Al2O3 + Fly ash.

3. The wear resistance was also found toincrease significantly with the addition ofreinforcements in aluminium.

4. Wear resistance of Al + Al2O3 + Fly ashcomposite was found to be better at loadof 40 N and both the sliding velocities of0.8 m/sec and 1 m/sec than pure Al.

5. Comparison of wear behavior ofspecimens at normal load of 40 Nrevealed that wear resistance of pure Al

Figure 6: Comparison of Cumulative Wear Rate for Pure Al and Al + Al2O3 + Fly AshComposites Subjected to Wear at Normal Load of 40 N at Two Sliding Velocities

of 0.8 m/sec and 1 m/sec

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and Al + Al2O3 + Fly ash compositeincreased with increase in sliding velocityeven though this increase was marginal forpure Al while for Al + Al2O3 + Fly ashcomposite it was considerable.

REFERENCES1. Asthana R and Tiwari S N (1993),

“Review: The Engulfment of ForeignParticles by a Freezing Interface”, Journalof Material Science, Vol. 28, p. 5414.

2. Bahera R, Chatterjee D and Sutrdhar G(2007), “Effect of Reinforcement Particleson the Fluidity and Solidification Behaviorof the Stir Cast Aluminium Alloy MetalMatrix Composites”, American Journal ofMaterial Science, Vol. 2, No. 3, p. 53.

3. Journals A Mortensen (1991), “InterfacialPhenomena in the Solidif icationProcessing of Metal Matrix Composites”,Material Science Engineering ,Vol. A-135, p. 1.

4. Lloyed D J (1989), “The SolidificationMicrostructure of Particulate ReinforcedAluminium/SiC Composites”,Composites Science and Technology,Vol. 35, p. 159.

5. Manchang Gui, Jianmin Han and PeiyongLi (2003), “Fabrication andCharacterization of Cast MagnesiumMatrix Composites by Vacuum StirCasting Process”, Journal of MaterialsEngineering and Performance, Vol. 12,No. 2, pp. 128-134.

6. Mortensten A and Jin I (1992),“Solidification Processing of Metal MatrixComposites”, International MaterialsReview, Vol. 28, p. 101.

7. Rajan T P D, Pillai R M, Pai B C,Satyanarayana K G and Rohatgi P K(2007), “Fabrication and Characterisationof Al-7Si-0.35 Mg/Fly Ash Metal MatrixComposites Processed by Different StirCasting Routes”, Composites Scienceand Technology, Vol. 67, p. 3369.

8. Rohatgi P K, Asthana R and Das S(1986), “Solidification, Structures andProperties of Cast Metal Ceramic ParticleComposites”, International MetalsReview, Vol. 3, p. 115.

9. Singh C (2012), “Synthesis andTribological Characterization ofAluminium-Silicon Carbide CompositePrepared by Mechanical Alloying”,International Journal of MechanicalEngineering and Material Sciences,Vol. 5, No. 1.

BOOKS AND WEBSITES1. http://www.substech.com/dokuwiki/

doku.php?id=liquid_state_fabrication_of_metal_matrix_com posites&s=liquid%20state%20 fabrication%20composite%20materials, retrieved on February 6,2013.

2. Michaud V J, Suresh S, Mortensten A andNeedleman A (1993), “Fundamentals ofMMCs”, p. 3, Butterworth- Heinmann,Stoneham, MA.

3. We Energies, “Coal CombustionProducts Utilization Handbook”, Chapter8, Fly Ash Metal Matrix Composites.


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