An Assessment of Mechanical and Tribological Property of Hybrid Aluminium Metal Matrix Composite

Mechanics, Materials Science & Engineering, May 2017

ISSN 2412-5954

An Assessment of Mechanical and Tribological Property of Hybrid Aluminium Metal Matrix Composite17 R. Santosh Kumar1, R. Nishanth1, V. Seenivasan1 , S. Sarath Sanmugam1, S. Johny James1, a 1

Department of Mechanical Engineering, Kingston Engineering College, Vellore, 632059, India

a

johnyjames2002@yahoo.com DOI 10.2412/mmse.30.1.536 provided by Seo4U.link

Keywords: composition of reinforcement, EDM, metal matrix.

ABSTRACT. Composite materials has huge requirement in the area of automobile, aerospace, and wear resistant applications. This study presents the synthesis of composite reinforced with SiC and Al 2O3 using gravity stir casting. Stir casting is the manufacturing process that is incorporated to produce the composite material because of its extreme bonding capacity with base material. The composition of reinforcement with 6061 aluminium matrix is SiC -7.5% and Al2O3 2.5% respectively. The average size of reinforcement particle is 30-40 microns. The synthesised composite casting is machined using EDM to prepare specimens for various tests. Microstructure study was carried and the microstructure images prove the existence and dispersion of reinforcement particles in the metal matrix. There is no visible porosity is observed. The hardness of the specimen is tested using Vickers hardness tester and found considerable increase when compare with parent alloy Al 6061. Also mechanical and tribological properties of hybrid Aluminium metal matrix composite were employed. The fortifying material, Silicon Carbide is composed of tetrahedral of carbon and silicon atoms with strong bonds in crystal lattice along with its excellent wear resistance property and alumina have high strength and wear resistance. To avoid enormous material wastage and to achieve absolute accuracy, wire-cut EDM process is capitalised to engrave the specimen as per required dimensions. Three Tensile test specimens were prepared, in order to achieve reliability in results as per ASTM- E8 standard, and the values were tabulated. Impact test was carried out and the readings were tabulated. Wear test was carried out using pin on disc wear test apparatus and the results show considerable increase in wear resistant property when compare with parent alloy Al6061.The above work proves the successful fabrication of composite and evaluation of properties.

Introduction. The dawning of any component begins with the significant selection of material. In the bygone days there is a lot of fascination towards materials that are having good mechanical and combination of different materials, it could be a metal, ceramics, [1].Aluminium metal matrix composite emerged from the need of lighter weight, higher performance characteristics in aerospace, automobile industries etc. Aluminium metal matrix composite replaces conventional aluminium alloys due to its high wear resistance, lower thermal expansion and higher strength to weight ratio[2].Silicon carbide is preferred because of its excellent refractory property and fatigue resistance.

In the work of Bhoopathi adding of silicon carbide results in increase of hardness and density.[3]Among the various manufacturing process available for the production of discontinuous metal matrix composite, stir casting is widely accepted due to its large flexibility, simplicity and higher bonding ratio [4]. The various mechanical properties are available among which the tensile, impact, hardness test are widely used. Wear test was carried out and increase in wear resistant property was reported due to addition of SiC has been reported by SJ James. Tribological property is studied to analyse the science behind two interacting surfaces. [5-7]. In this assessment an effort has been taken to assess the mechanical and tribological properties of hybrid aluminium metal matrix which is developed using stir casting mixing reinforcement SiC and Al2O3 respectively.

Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Mechanics, Materials Science & Engineering, May 2017

ISSN 2412-5954

Experimental procedure. In this assessment, the hybrid aluminium metal matrix composite was prepared by exploiting stir casting method. To carry out this process, we have chosen 90% of aluminium alloy 6061, silicon carbide7.5% and alumina 2.5% were subjected to preheating process.

The preheating is done at a temperature of 2500c.The melting of aluminium alloy rod takes place at a casting temperature of 6600c and the melt was stirred with the help of stainless steel stirrer which rotates at 550rpm.The entire setup operates at a voltage of 214 V with a frequency of about 50.1 Hz. The impurities were removed and magnesium was added with a proportion to increase wettability.

The molten composite is allowed to solidify in the mould to get the desired shape. The finished casting product is later subjected to wire cut EDM to prepare test specimens. In order to perform microstructure study specimens were polished and optical microscope was used to capture images.

The tensile test was carried out using Tensometer and the specimen dimension refers to ASTM E8 standard. The hardness test was carried out using Vickers hardness test containing pyramid shape diamond intender. The ability of the component to withstand heavy blow without fracture is defined as impact strength. The specimen size is mentioned as per the standard Charpy test. The length is of 55mm and 10mm width with 10mm thickness. The notch angle is about 450 with 0.25mm radius.

Two samples were taken into consideration to evaluate the mean impact strength. The resultant impact strength was calculated in joules. This will indicate the maximum amount of energy it is absorbed before deformation or failure. The wear or tribological behaviour is assessed using pin on disk apparatus. The frictional force, coefficient of friction, wear rate are the parameters that are evaluated in this section. The Linear Reciprocating Tribometer can accommodate a variety of sample geometries to create point, line and area contacts. Customized sample holders can also be provided for tests requiring conformal contacts.This system is computer controlled and includes a data acquisition software that can be used to acquire, view and report results. Lubricant was applied during the wear test.

Results &Discussion. This study of external force observation depicts the mechanical properties of the composites. The characterization of the developed composite was carried using microstructure study. The various mechanical properties include tensile behaviour, hardness, and Impact characteristics. The tribological property of the developed composite was assessed by conducting wear test.

Microstructure Study

Al203 Si

a)

b)

Fig. 1. (a), (b) Micrograph of developed Composite.

Optical microscope has been used to plot the micrographs. The Fig. 1 (a) indicates the focal length of 50 micrometer and Fig. 1 (b) focal length of 20 micrometer. From Fig. 1 (b) shows the dispersed reinforcements along the metal matrix. This study proves the existence of the reinforcements.

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Tensile Characteristics. Three test specimens were subjected to tensile test and the tensile strength values of developed composite were tabulated in Table.1. The higher poisons ratio clearly indicates that this material is completely brittle in nature. The variation in tensile strength values is due to the uneven dispersion of reinforcements. The agglomeration of reinforcements during casting decides high and low tensile strength. The developed composite exhibits a maximum tensile strength of 152 Mpa. The following gives the calculated tensile value. Fig 2 and 3 are the graphs plots from the values obtained during tests.

Table 1. Tensile values of developed Composite Al6061/SiC/Al2O3.

S. no.

Sample no.

Tensile strength

Elongation

Poissons ratio

1

1

131 Mpa

2.47%

0.820

2

2

152 Mpa

3.26%

0.891

3

3

120 Mpa

2.11%

0.978

Maximum tensile value

152 MPa

The tensile strength is calculated by the expression: Tensile strength=Breaking load/Cross sectional area Tensile strength=4716/36=131N/mm2 The elongation is calculated by the equation: (Final gauge length-Initial gauge length)/(Final gauge length)x100 The poisons ratio is calculated by the equation: Poisons ratio=Lateral strain/longitudinal strain Lateral strain=change in breadth/original breadth Lateral strain=5/6=0.833 Longitudinal strain=change in length/original length Longitudinal strain=101.5/100=1.015 Poisons ratio=lateral strain/longitudinal strain Poisons ratio=0.833/1.015 Poisons ratio=0.820 The graphical representation is given in the figure 1 and figure 2.

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TENSILE STRENGTH [Mpa]

LOAD vs TENSILE STRENGTH 200

150 100 STRENGTH

50

0 471.6

547.2

432

LOAD [Kg]

Fig. 2. Graph-Tensile value of developed Composite Al6061/SiC/Al2O3.

ELONGATION vs LOAD ELONGATION(%)

4.00% 3.00% 2.00% elongation

1.00% 0.00% 432

471.6

547.2

LOAD (Kg)

Fig. 3. Graph-Tensile value of developed Composite Al6061/SiC/Al2O3.

Hardness characteristic. Hardness in this assessment was done by Vickers micro hardness tester.

The test was carried out using a diamond -pyramid indenter. The hardness value of aluminium alloy Al6061is 59.18 HRC. The mean value obtained after five tests were 91.98 HRC. The value obtained is 64.35% greater than hardness value of parent metal alloy Al6061.The below Table 2 indicates the mean hardness value of developed composite. The highest hardness value is due to the addition of reinforcements. This is one of the peculiar properties of composites. These values are obtained before doing the tempering operation; if heat treatment was done result would show higher values.

Impact characteristics.Two specimens were prepared and subjected to impact test. The values are tabulated in Table 3. The resultant impact strength was calculated in joules. This will indicate the maximum amount of energy it is absorbed before deformation or failure. The variation in the 2 distinct values of the impact strength is probably due to the improper mixing of reinforcements with the base metal.

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Mechanics, Materials Science & Engineering, May 2017

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Table 2. Hardness values of developed Composite Al6061/SiC/Al2O3.

S.no.

Position

Hardness value

Unit

1

P1

95.9

HRC

2

P2

79.6

HRC

3

P3

99.9

HRC

4

P4

101.6

HRC

5

P5

82.9

HRC

Mean value

91.98 HRC

Table 3. Impact test values of developed Composite Al6061/SiC/Al2O3.

Sample no

Impact strength (joules)

1

16

2

6

Maximum value

16 Joules

Wear characteristics.The wear specimen is made as per the requirement 30X30X10 mm. The pin is made up of mild steel and is 10mm in dia and 30mm in length. The load applied is 50N and time of rotation is 60 min. The value of wear is measured in microns and its value is 9.918. The wear is negligible due to the addition of reinforcements. The COF, frictional force, speed and wear is tabulated in Table.4.

As the Coefficient of friction decreases the frictional force also decreases. The below Fig.4 indicates the fluctuation in the coefficient of friction as the load varies. This clearly shows that frictional force is directly proportional to coefficient of friction.

Table 4. Wear test values of developed Composite Al6061/SiC/Al2O3 S.no

Cof

Frictional force

Time

Temperature

Load

Speed

Wear (micrometer)

1

0.121

6.169

54.018

35.026

50.877

609.337

9.918

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10 8 6 4 2 0

0.124 0.117

0.129

0.129 0.132

0.14

0.133

0.143

0.143 0.141

0.15

FORCE 0.016

FRICTIONAL FORCE

CO-EFFICIENT OF FRICTION vs FRICTIONAL FORCE

CO-EFFICIENT OF FRICTION Fig. 4. Graph-wear test values of developed Composite Al6061/SiC/Al2O3.

Summary. The new composite was successfully designed and synthesised using stir casting route.

The specimens were cut as per requirement using wire EDM. Microstructure study proves the existence of reinforcements in the metal matrix and agglomeration as well. The tensile test value along with poisons ratio clearly shows that the material fracture is ductile-brittle mode. It also adds that the maximum tensile value is 152MPa. The hardness value is nearly 64.35% greater than the base metal hardness value. The impact test shows variation in values and is due to agglomeration. The maximum impact value is 16 joules.The wear test value indicates the enhanced wear resistance property of the developed composite with applied base oil lubricant. The maximum wear value is 9.918 micrometer. Excellent wear resistance property is achieved which is one of the unique property of composites.

References [1] Rajan H. M., Ramabalan S., Dinaharan I., & Vijay S. J. (2013). Synthesis and characterization of in situ formed titanium diboride particulate reinforced AA7075 aluminum alloy cast composites. Materials & Design, 44, 438-445.

[2] Alaneme K. K., Bodunrin M. O. (2013). Mechanical behaviour of alumina reinforced AA 6063 metal matrix composites developed by two step-stir casting process. Acta Technica Corviniensisbulletin of engineering, 6(3), 105.

[3] Boopathi M. M., Arulshri K. P., & Iyandurai, N. (2013). Evaluation of mechanical properties of aluminium alloy 2024 reinforced with silicon carbide and fly ash hybrid metal matrix composites.

American journal of applied sciences, 10(3), 219.

[4] Suragimath M. P. K., Purohit G. K. (2013). A study on mechanical properties of aluminium alloy (LM6) reinforced with SiC and fly ash. IOSR J. Mechanical and Civil Engg, 8, 13-18.

[5] Lloyd D. J. (1994). Particle reinforced aluminium and magnesium matrix composites.

International Materials Reviews, 39(1), 1-23.

[6] James S. J., Venkatesan K., Kuppan P., & Ramanujam R. (2014). Hybrid Aluminium Metal Matrix Composite Reinforced with SiC and TiB 2. Procedia Engineering, 97, 1018-1026.

[7] Mistry J. M., & Gohil P. P. (2016). An overview of diversified reinforcement on aluminum metal matrix composites: Tribological aspects. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, DOI 10.1177/1350650116658572 [8] Poria S., Sahoo P., & Sutradhar G. (2016). Tribological Characterization of Stir-cast AluminiumTiB2 Metal Matrix Composites. Silicon, 1-9.

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