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International Journal of Engineering, Applied and Management Sciences Paradigms

Volume 52, Issue 04, Quarter 04 (October-November-December 2018)

An Indexed and Referred Journal with Impact Factor: 2.50

ISSN (Online): 2320-6608

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Experimental Investigation on Microstructure and

Mechanical Properties of AA6063 with S i l i c on

C ar b ide

Rajkumar1, Pardeep Gahlot2, Naveen Hooda3 and Ashish4

1,2,3,4Mechanical Engineering Department, U.I.E.T.,

Maharshi Dayanand University, Rohtak, INDIA

Publishing Date: October 11, 2018

Abstract Aluminum Metal Matrix Composites (MMC)’s are

prominent in various applications because of having low

density and high stiffness. AA6063 MMC also has unique

features as well. SiC has garnered a maintained space to

be used as reinforcement material for aluminum based

metal matrix composites. In the present work, an attempt

has been to develop AA6063 based MMC’s by means of

muffle furnace whereby SiC is used as reinforcement b y

stir casting techniques. The SEM images and optical

micrograph image microstructure details are presented

for the different composition structures of MMC’s that

have been developed. It is evident from the SEM images

that microstructure of composites is observed to have a

homogeneous distribution of reinforcement and enhanced

bonding exists between the molecules of SiC and AA6063

particles. It has been resulted that the micro hardness and

impact strength of the prepared specimen has increased

considerably from the parent metal. The ultimate tensile

strength is also improved significantly.

Keywords: Metal matrix composite, AA6063, SiC,

microstructure, mechanical properties.

Introduction

Al is about a third of the steel and its weight of 2.7

gm. /cm3, Al is a particular very light metal. For

instance the utilization of Al in vehicles vitality

utilization while expanding load limit and decreases

with dead-weight. A profoundly corrosion resistant

and is protective oxide coating normally produces by

Al. It is especially valuable for applications where

protection and insurance are necessary. Al MMC’s

are highly popular in various engineering and

technical applications as they have low density and

high stiffness. These unique mechanical properties of

AA6063 alloys have forced the researchers to

develop new alloys and MMC’s having enhanced

properties [6]. The incomparable properties of SiC

have brought favorable challenges for using it as a

potential reinforcing material for enhancing

mechanical, thermal and electrical properties of

composites [1]. Today, Silicon carbide has been

created into a great specialized review earthenware

with great mechanical properties (such as abrasives,

ceramics, refractoriness, and numerous high-

performance). The Silicon carbide is mainly used in

resistance heating, flame ignites, electrical conductor

and electronic components. Silicon Carbide is a very

hard and solid material having tetrahedral shape [9].





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Table 1: Properties of Silicon Carbide

In this present work, AA6063 alloy along with SiC

as reinforcement has been used to prepare MMC

using stir casting technique. Different compositions

of SiC used are 0, 3.5wt%, 6.5wt%, 9.5wt% and

12.5wt% of the castings prepared. The

microstructure and the dispersion of reinforcement,

mechanical properties were studied.

Sample Preparation

Cleaned AA6063 strips were liquefied over the super

heating temperature of about 9000C in graphite

crucibles under a layer of flux utilizing an muffle

resistance furnace as shown in Figure 1 and 2. The

preheated silicon carbide particulates were then

added to the liquid metal and stirred ceaselessly for

about 15 minutes at stirrer speed of 700 rpm.

Aluminium matrix and silicon carbide particles were

weighed utilizing an electronic weighing machine

(Accuracy 0.0001gm). During stirring, 1% by weight

of Mg (magnesium) was added to expand the wet

ability of silicon carbide particles. [2, 3] The melt

with reinforced particles was emptied by gravity

casting into the dried, rectangular permanent metallic

moulds of size 100mm x 50mm x 50 mm. The

mixture of AA6063 and SiC was permitted to solidify

in the moulds for about 30-50 minutes and cooled to

room temperature. [5] With the end goal of

correlation base composite samples were likewise

thrown under comparative handling conditions. [4]

Samples of different weight percentages of the cast

composite specimens are shown in Figure 2.

Figure 1: Schematic Set Up of Stir Casting Technique [Source: (Ravi Kumar 2012)] [7]





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Figure 2: Testing of Mechanical Properties

Results & Discussion

(i) Microstructure using optical micrograph and SEM images

The Scanning Electron Microscope (SEM) is a standout amongst the most adaptable instruments available for the

test and investigation of the microstructural attributes of solid objects. It enables us to contemplate the dispersion of

the SiC in the Al Alloy Metal Matrix. There must be a uniform distribution of the reinforcement materials in the Al

6063 Matrix. Multiple Images were taken at different scaling sizes and weight fractions. For microstructure testing,

the fabricated MMC’s were polished in such a fine way that there should be mirror like image on upper surface of

samples. [8] The mirror like surface finish of samples were achieved by rubbing the sample on emery papers (100 to

2000 micron) and valvet cloth with help of polishing machine and then surface of samples were washed by killer’s

etching reagent (Methnol, Hcl, Hno3, one drop of Hf). In the fabricated MMC’s the difference of distribution of SiC

particle to be seen by optical microstructure tester [range X50 to X 1500] Dewinter technologies Italy as shown in

Figure 3(OM) and Figure 4(SEM). Micrographs of Al/ SiC-MMC’s samples for various size and weight fraction of

SiC particles as shown in Figure 3 and Figure 4, respectively.

Figure 3: OM images of microstructure





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Figure 4: SEM Images of microstructure

(ii) Mechanical Properties The Micro Vickers hardness estimations of

composite specimens illustrate an increase in

hardness with increase in different weight fractions of

SiC (3.5, 6.5, 9.5, and 12.5%) with size of SiC

particles. Hardness of the composites likewise

expanded with increment in mesh silicon carbide

content which gives a near direct association with

hardness. Hardness of the composites expanded with

increment in SiC molecule measure. It is observed

that, with the increase in the SiC weight fraction %,

the tensile strength also increases. The least tensile

strength esteem (105 MPa) was seen in 3.5 wt. % size

of SiC particles composites, while the most

noteworthy tensile strength of (157MPa) was seen in

12.5 wt. % size of SiC particles composites

reinforced with Al 6063 respectively. Izod impact

strength of composite specimens reinforced with

Silicon carbide particle of various weight divisions

(3.5, 6.5, 9.5, and 12.5%) with size of SiC particles

was observed. It was apparent from the graphs that

the impact resistances increase with increase in

weight fraction of SiC Particles (3.5, 6.5, 9.5, and

12.5%) with size of SiC particles content. Impact

strength of micro sized silicon carbide composites

was speculated to be higher than that of the

unreinforced Al alloy. Figure 5, 6 and 7 are

describing about tabulated values of hardness, tensile

strength and impact strength at different weight % if

SiC. The mechanical properties of various test

results are shown in Table 2.

Table 2: Hardness, Tensile Strength and Impact Strength at different weight % of SiC

Weight % of SiC 0 3.5 6.5 9.5 12.5

Hardness (Vicker’s) 47.9 51.3 52.60 66.7 72.4

Tensile Strength (MPa) 97 105 117 131 157

Impact Strength (Izod) 18 21 25 31 36





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Figure 5: Hardness at different weight % of SiC

Figure 6: Ultimate tensile strength at different weight % of SiC

0

10

20

30

40

50

60

70

80

0 3.5 6.5 9.5 12.5

Har

dn

ess

0

20

40

60

80

100

120

140

160

180

0 3.5 6.5 9.5 12.5

Ult

imat

e T

en

sile

Str

en

gth

Column1





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Figure 7: Impact Test variations of AA 6063 with different weight % of SiC

Conclusion

The SEM images revealed the white eutectic

matrix (AA6063) and dark phase with an interphase

between them. The experimental analysis also

confirms the composition of various elements into

the cast matrix composite. The formation of any

other compound was denied in the SEM analysis.

The increased homogeneity in the composite matrix

is attributed to the increase in properties. It can be

interpreted from the study that the properties of

micro SiC particulates reinforced AMCs increases

with increase in weight fraction. The experimental

results revealed that there is an appreciable increase

in the mechanical properties for 3.5% of weight

fraction. With further increase in weight fraction

upto 12.5%, the mechanical and tribological

properties increased significantly. This is due to

decreased porosity, voids while blending SiC with

the Al matrix. The increased homogeneity in the

composite matrix is attributed to the increase in

properties. It can be interpreted from the study that

the properties of micro SiC particulates reinforced

AMCs increases with increase in weight fraction.

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0

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0 3.5 6.5 9.5 12.5

Imp

act

Stre

ngt

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Series 1





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[5] Manoj Singla(2009), “Development of

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