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Studies On Microstructure And Mechanical Properties Of Flyash Reinforced Al2024 Composites Sathisha N 1, Tejas G2, Praveen kumar R A 3, Manjunath Vajjaramatti4, Avinash L5 UG student, Department of Mechanical Engineering, NMIT Bengaluru, Karnataka, India1, 2, 3, 4 Assistant professor, Department of Mechanical Engineering, NMIT, Bengaluru, Karnataka, India 5
Abstract: The aim is to study the mechanical property and Tribological behavior of Al2024/flyash composite with various weight fractions (3%, 6%, 9%) were prepared by squeeze casting method. The average particle size of flyash is 45-50 Îźm. In addition, Al2024 alloys were cast for comparison purposes. Microstructure, hardness and tensile properties of these composites were evaluated and compared with as-cast alloy and the composites. In addition, tribological properties of these composites were evaluated using a Pin-on-Disc apparatus with different parameters of varying loads of 10N and 50N and(with constant parameters such as time of 10 minutes, sliding velocity of 3 m/s, track diameter of 150mm).The microstructure of the composites shows homogenous distribution of flyash particles in the Al matrix composite. The wear and mechanical properties of composites improve with increasing the weight fraction of flyash. The aim of present study is to evaluate the effect of microstructure, mechanical and tribological properties of aluminium alloy Al2024/flyash metal matrix composites Keywords: Al2024 alloy, Flyash, microstructure, Hardness, Wear.
1. INTRODUCTION Conventional monolithic materials have limitations in achieving good combination of strength, stiffness, toughness and density. To overcome these shortcomings and to meet the ever increasing demand of modern day technology, composites are most promising materials of recent interest. Metal matrix IDL - International Digital Library
composites (MMCs) possess significantly improved properties including high specific strength; specific modulus, damping capacity and good wear resistance compared to unreinforced alloys. There has been an increasing interest in composites containing low density and low cost reinforcements. Among various discontinuous dispersoids used, fly ash is one of the most inexpensive and low density reinforcement available in large quantities as solid waste by-product during combustion of coal in thermal power plants. Hence, composites with fly ash as reinforcement are likely to overcome the cost barrier for wide spread applications in automotive and small engine applications. It is therefore expected that the incorporation of fly ash particles in aluminium alloy will promote yet another use of this low-cost waste byproduct and, at the same time, has the potential for conserving energy intensive aluminium and thereby, reducing the cost of aluminium products [1-3]. Now a days the particulate reinforced aluminium matrix composite are gaining importance because of their low cost with advantages like isotropic properties and the possibility of secondary processing facilitating fabrication of secondary components. Cast aluminium matrix particle reinforced composites have higher specific strength, specific modulus and good wear resistance as compared to unreinforced alloys [46].While investigating the opportunity of using fly-ash as reinforcing element in the aluminium melt, R.Q.Guo and P.K.Rohatagi [7-8] observed that the high electrical resistivity, low thermal conductivity and low density of fly-ash may be helpful for making a light weight insulating composites. The particulate 1|P a g e
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International e-Journal For Technology And Research-2017 composite can be prepared by injecting the reinforcing particles into liquid matrix through liquid metallurgy route by casting [9-10]. Casting route is preferred as it is less expensive and amenable to mass production. Among the entire liquid state production routes, stir casting is the simplest and cheapest one. The only problem associated with this process is the non uniform distribution of the particulate due to poor wet ability and gravity regulated segregation. Mechanical properties of composites are affected by the size, shape and volume fraction of the reinforcement, matrix material and reaction at the interface. These aspects have been discussed by many researchers. Rohatgi [1] reports that with the increase in volume percentages of fly ash, hardness value increases in Al– fly ash (precipitator type) composites. He also reports that the tensile elastic modulus of the ash alloy increases with increase in volume percent (3–10) of fly ash. Aghajanian et al. [11] have studied the Al2O3 particle reinforced Al MMCs, with varying particulate volume percentages (25, 36, 46, 52 and 56) and report improvement in elastic modulus, tensile strength, compressive strength and fracture properties with an increase in the reinforcement content. The interface between the matrix and reinforcement plays a critical role in determining the properties of MMCs. Stiffening and strengthening rely on load transfer across the interface. Toughness is influenced by the crack deflection at the interface and ductility is affected by the relaxation of peak stress near the interface [12-14]. Extensive studies on the tribological characteristics of Al MMCs containing reinforcements such as SiC and Al2O3 is available in the literatures [15-18]. However, reports on friction and wear characteristics of fly ash reinforced AMCs are very limited. Rohatgi has reported that the addition of fly ash particles to the aluminium alloy significantly increases its abrasive wear resistance. He attributed the improvement in wear resistance to the hard aluminosilicate constituent present in fly ash particles. In the present work, fly-ash which mainly consists of refractory oxides like silica, alumina, and iron oxides is used as reinforcing phase. Composite was produced with 10% fly-ash as reinforcing phase. Commercially
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pure aluminium was also melted and casted. Then particle size and chemical composition analysis for fly-ash was done. Mechanical, physical and wear properties of the composite were evaluated and compared with the commercially pure aluminium. Moreover, the composite was characterized with the help optical microscope, hardness test and tensile tester.
2. OBJECTIVES The need of a systematic study of various mechanical properties of fly ash reinforced Al2024 composites. This study can lead one to explore the possibility of identifying the use of these composites as tribomaterials especially for automobile applications. Therefore the work taken up had the following objectives: 1. Fabrication of Al2024/ fly ash composites by Liquid metallurgy route. 2. Microstructure characterization of the composites using optical microscopes. 3. Evaluation of mechanical properties of the composites. 4. Comparing the results of mechanical properties of as-cast alloy with composites. 5. Validating the experimental results with Design of Experiments 6. Drawing Conclusion based on the obtained result. The present study is thus aimed at producing MMCs with Al2024 as the matrix material with fly ash as reinforcement processed by stir casting route of these composites in order to obtain mechanical properties suitable for a wide range of engineering applications.
3. METHODOLOGY
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Figure(a),(b),(c),(d)shows the micro photographs of both the matrix alloy Al2024 and its composites Fig. Flow Chart of Experimental Work
4. IMPLEMENTATION 2024 is typically used in: 1. Architectural applications 2. Extrusions 3. Window frames 4. Doors 5. Shop fittings 6. Irrigation tubing 7. In balustrading the rails and posts are normally in the T6 temper and formed elbows and bends are T4. T4 temper 2024 aluminium is also finding applications in hydro formed tube for chassis.
system. Figure (b). (c), (d) revealed that presence of fly ash particles in Al2024 alloy matrix and further confirms that there was a uniform distribution of fly ash particles in the base matrix of Al2024 alloy .The images clearly shows that there were no voids and discontinuities in the composite and also there was a good interfacial bonding between the fly ash particles and matrix materials. Hardness Test Result:
5. OUTCOMES 1. 2. 3. 4.
It is widely used in aircraft structures. The material is susceptible to thermal shock. Good improvement in mechanical properties. High strength to weight ratio.

Optical Microstructural Characterization
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IDL - International Digital Library Of Technology & Research Volume 1, Issue 3, Mar 2017
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Fig: UTS values of Al2024 alloy and its Composites
Fig: Hardness values of Al2024 alloy and its composites From above Figure it is found that hardness increase with increasing Flyash content in the material. As compared to as-cast (AL2024 alloy), 3% Flyash addition shows an increase of 5.56 BHN (11.44%). In contrast 6% and 9% Flyash addition shows an increase of 17.35 BHN (35.72%) and 26.32 BHN
From above Figure it is found that Ultimate tensile strength increase with increasing Flyash content in the material. As compared to as-cast (AL2024 alloy), 3% Flyash addition shows an increase of 30.16 MPa (24.45%). In contrast 6% and 9% Flyash addition shows an increase of 39.32 MPa (31.88%) and 45.95 MPa (37.25%) respectively. The improvement in strength in casted composites may be ascribed to uniform distribution of reinforcement (Flyash) in the matrix material. The fly ash particles help in strengthening the matrix, acting as barriers to the dislocations when taking up the load applied.
(54.20%) respectively. The improvement in hardness Table : YTS of Al2024 alloy and its Composites
in casted composites may be ascribed to uniform distribution of reinforcement (Flyash) in the matrix material
TENSILE TEST RESULTS: UTS of Al2024 alloy and its Composites Fig: YTS values of Al2024 alloy and its Composites From Figure it is found that Yield tensile strength increase with increasing Flyash content in the material. As compared to as-cast (AL2024 alloy), 3% Flyash addition shows an increase of 30.16 MPa (28.34%). In contrast 6% and 9% Flyash addition IDL - International Digital Library
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International e-Journal For Technology And Research-2017 shows an increase of 39.32 MPa (35.31%) and 45.95
Dry sliding wear tests were conducted as per
MPa (39.24%) respectively. The improvement in
ASTM-G99 norms. The wear rate was based on the
strength in casted composites may be ascribed to
average value of 3 tests. Two loads of 10N and 50N at
uniform distribution of reinforcement (Flyash) in the
a sliding velocity of 3.0m/sec and sliding distance of
matrix material. The fly ash particles help in
1800m. During the test the following specifications
strengthening the matrix, acting as barriers to the
were used:
dislocations when taking up the load applied. Table : Specifications used in wear studies Table : Ductility of Al2024 alloy and its Composites
CALCULATIONS:
1. SlidingVelocity(V)=
……..(i)
3.= Fig: Ductility values of Al2024 alloy and its Composites The results of the ductility test carried out on all the MMCs taken up for investigations are shown in Table
Where, D is track diameter in mm, N is speed in rpm From Equation (i) N=382 rpm 2. SlidingDistance(S)
The percentage decrease in ductility with
=
=
……..(ii)
different weight fractions of reinforcements is also given. Figure shows the effect of the weight fraction of
Where, T is time in minutes.
fly ash on the ductility of Al2024 alloy matrix by
From Equation (ii) S=1800meters
reinforcements. Figure shows that the ductility of the composite decreased with the increase in weight fraction of the fly ash. This may be due to the hardness of the fly ash particles or clustering of the particles.
WEAR STUDIES
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International e-Journal For Technology And Research-2017 Table: Wear behavior of Al2024 alloy and its Composites
Fig(c): Effect of load on wear (µm) of the Al2024 alloy and its Flyash composites (Sliding Velocity : 3.0m/s, Sliding distance: 1800m, load: 10 and 50N) From the above figs it can be see that as the load increases the wear rate increases. Maximum wear rate can be observed in Al2024 alloy and least wear rate is observed in As-cast alloy with 9% alumina. The decrease in wear rate may be attributed to the Flyash particles which act as load bearing in the Al2024 matrix and resist wear. Due to the absence of Flyash particle as reinforcement in as-cast alloy it has a maximum wear rate. The wear rate in composites is less due to the fact that ploughing of the fly ash becomes difficult as the particle size increases.
CONCLUSION Fig(a): Wear graphs of Al2024 alloy and its AL2024 alloy +3% Flyash Composites respectively at 10N and 50N respectively
From the test conducted I order to determine the mechanical properties of flyash reinforced Al2024 composites of different weight fractions of the reinforcement, it was found that i. flyash particles as reinforcements helped in increase of UTS of Al2024 from 110.02 MPa as per the following
3%flyash141.20MPa(46% increases)
Fig(b): Wear graphs of Al2024 alloy +6% Flyash and AL2024 alloy +9% Flyash Composites respectively at 10N and 50N respectively
6% flyash-148.87MPa(46% increases)
9% flyash-153.20MPa(46% increases)
It can be noted that UTS of the composite increased with increase in weight fraction of flyash ii. flyash particles as reinforcement helped in the increasing the hardness of Al2024 from 48.6BHN as per the following
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3%flyash54.12BHN (21% increase).
6%flyash65.91BHN (34% increase).
9%flyash74.88BHN (52% increase).
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International e-Journal For Technology And Research-2017 iii.
The increase in weight fraction of the flyash reinforcement had a significant increase in hardness and wear resistance further.
From the tribological tests carried out on Al2024 and its composites, it was observed that: i. Flyash particles as a reinforcement helped in decreasing the wear rate of Al2024 ii. he percentage of reinforcement of flyash was increased, wear rate was found to reduce and hence wear resistance of specimen improved. From the optical micrographs of polished specimen, the following was observed: i. The distribution of reinforcement particles (flyash) is found to be uniform ii. The flyash particles are not trapped in the grain boundaries iii. The majority of the Flyash particles are located inside the matrix itself which indicates that it has wetted better due to the addition of Mg as a wetting agent.
[5] Basavarajappa, S., Chandramohan, G., Subramanian, R., Chandrashekhar, A. (2006). “Dry sliding wear behaviour of Al2024/ SiC metal matrix composites.” Materials Science, Poland, 24, (2/1), 357-366. [6] J.W. Kaczmar, K. Naplocha (2008) “Wear behavior of composite materials based on 2024 AlF alloy reinforced with alumina fibers”, an Institute of Production Engineering and Automation, Wroclaw University of Technology, Poland t [7] Mahendra, K.V., Radhakrishna, K. (2007). “Castable composites and their application in automobiles”, Proceedings I Mech E 221(Part D): J. Automobile Engineering, 135-140. [8] A.P. Sannino and H.J. Rack, “Dry Sliding Wear of Discontinuously Reinforced Aluminium Composites: Review and Discussion”, Wear, Vol.189, Pp.1-19, T 1995. [9] R.K. Uyyuru, M.K. Surappa and S. Brusethang, T “Effect of reinforcement volume fraction and size distribution on the tribological behavior of Al – T Composite”, Wear, Vol.206, Pp.1248 – 1255, 2006. [10] C.S. Ramesh, S.K. Sheshadri and K.J.L. Iyer, “A survey of aspects of wear of metals”, Indian Journal of Technology, Vol.29, Pp. 179 – 185, 1991.
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[11] Energy distribution in Glare and 2024-T3 Aluminium during low-velocity impact (International Congress
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International e-Journal For Technology And Research-2017 1684,p-ISSN: 2320-334X, Volume 12, Issue 5 Ver. IV, PP 108-122 [14] Inampudi Narasimha Murthy, Nallabelli Arun Babu, Jinugu Babu Rao (2014) “Comparative Studies on Microstructure and Mechanical Properties of Granulated Blast Furnace Slag and Fly Ash Reinforced AA 2024 Composites” Journal of Minerals and Materials Characterization and Engineering, , 2, 319-333 [15] Cun-Zhu Nie, Jia-Jun Gu, Jun-Liang Liu, Di Zhang,(2007) “Production of Boron Carbide Reinforced 2024 Aluminum Matrix Composites by Mechanical Alloying” Materials Transactions, Vol. 48, No. 5 , pp. 990 to 995
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