FABRICATION OF STUDY OF MECHANICAL PROPERTIES ......FABRICATION OF STUDY OF MECHANICAL PROPERTIES OF ALUMINIUM ALLOY 6061 REINFORCED WITH NANO ZIRCONIA Ravi Kiran R1, Ghanaraja S2

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FABRICATION OF STUDY OF MECHANICAL PROPERTIES OF

ALUMINIUM ALLOY 6061 REINFORCED WITH NANO ZIRCONIA

Ravi Kiran R*1, Ghanaraja S*

2

*1PG Student, Dept. of Mechanical Engineering, P.E.S College of Engineering, Mandya, India.

*2Professor, Dept. of Mechanical Engineering, P.E.S College of Engineering, Mandya, India.

ABSTRACT

Metal matrix composite Aluminum alloy (Al 6061) and Magnesium (Mg) matrix are reinforced with Nano

zirconia (ZrO2) nanoparticles prepared by the stir casting technique. Aluminum alloy is chosen as the matrix

materials and zirconia particles is co-operated with various proportions of 0 wt%, 0. wt%, 1 wt%, 1.5 wt% and 2

wt% and all other parameters are kept stable. Stirring was performed to record uniform distribution of

particulates of reinforcement and round castings were made by pouring the composite mixture into sand mould.

The composite was then studied with respect to its micro structure and mechanical properties. The composite

was then studied with regard to its microstructure and mechanical properties. Tensile specimens were machined

to determine the mechanical properties of the composite according to ASTM standards. The comparative study

for all said composites is done with regard to tensile strength, hardness. Scanning electron microscope (SEM) is

used to observe the distribution of particulates to understand the nature of fractured surface.

KEYWORDS: Metal matrix composite, Aluminium alloy 6061, Magnesium, Nano zironia, Stir casting and

SEM

I. INTRODUCTION

Composite materials are created by combining two or more different materials with distinct chemical or

physical properties. The resulting composite exhibits properties that are distinct from its constituent materials,

which remain separate and independent within the finished structure and are not kept together by formal

chemical bonds. In nano-composites, either one of the constituents has nanoscale dimensions (< 100 nm), or

alternatively the composite structure exhibits phase separation of the individual components in nano-sized

formats. In mechanical terms, nanocomposites differ from conventional composite materials due to the

exceptionally high surface to volume ratio of the reinforcing phase and its exceptionally high aspect ratio. The

reinforcing material can be made up of particles, sheets or fibres. The area of the interface between the matrix

and reinforcement phase is typically an order of magnitude greater than for conventional composite materials.

The matrix material properties are significantly affected in the vicinity of the reinforcement.

Aluminium is now the world’s second most commonly used metal after iron. It is because aluminum has a rare

combination of desirable properties such as low weight, high strength, superior malleability, simple machining,

excellent resistance to corrosion and strong thermal and electrical conductivity are among the most significant

properties of aluminum. It’s also very simple to recycle aluminium. A mixture of two or more materials

(reinforcing components, fillers, and composite matrix binder), which vary on a macro-scale in shape or

composition. The members maintain their personalities, that is, when they behave in concert, they do not break

or fuse entirely into one another. The elements may usually be physically defined and an interaction displayed

with each other. Sources of these are composites of cermet and metal matrix. Materials constitute the

fundamental aspect of both natural and manmade structures. Any material composed of two or more

components with different properties and distinct boundaries between the components may usually be called a

composite material. Aluminum alloy based composites are very attractive due to their processing flexibility,

wide range, low density and abundant availability, high wear resistance, high thermal conductivity , high heat

treatment capability, improved elastic modulus, high strength , high stiffness and high dimensional stability.

Applications of MMC based aluminum have increased as engineering materials in recent years. The introduction

of a ceramic material into a metal matrix produces a composite material which results in an attractive

combination of physical and mechanical properties which cannot be achieved with monolithic alloys.

https://en.wikipedia.org/wiki/Composite_material

https://en.wikipedia.org/wiki/Aspect_ratio



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Discontinuously reinforced aluminum matrix composites have emerged from the need for light weight and high-

stiffness materials that are suitable in many applications, especially in aerospace and automotive products such

as engine piston, cylinder liner, brake disc / drum, etc. Strengthening aluminum alloys with the reinforcement of

fine ceramic particles has greatly increased their potential for wear resistance and structural applications. There

is an increasing interest in the development of metal matrix composites (MMCs) with low cost reinforcements,

high strength, high stiffness and better wear resistance.

In the present study, nano composites are synthesized by adding different wt% of nano zirconia (ZrO2) particles

to aluminum 6061 molten alloy during stirring. The objective of developing nano composites in this study by

stir casting is to study their potential applications in structural components and the mechanical properties of

these composites are essential for this study. To order to correlate with the observed mechanical properties

calculated to terms of hardness and tensile strength, attempts are made to consider the microstructure of the

composites like particle distribution.

II. LITERATURE

K. B. Girisha, et al. [1] project on the effect of different weight fraction of nano zirconia (2.0%, 2.5%, 3.0%,

and 3.5%) reinforced with Al356.1 metal matrix composite by stir casting method. It was observed that particle

agglomeration in composites with high content of nano zirconia. It was observed that particle agglomeration in

composite due to high content of nano zirconia. Hardness and wear properties increases with the increase of

weight fraction of nano zirconia particle.

Dharmesh M.Patoliya, et al. [2] in their investigation they take approximately 2 Kg of Al 6061 in solid form

and melted that in furnace and add fixed quantity of Zirconia, it was taken in powder form in suitable crucibles.

They preheat the ZrO2 to remove moisture and gasses from surface of the particles. In stir casting method they

maintain the stirrer speed at 500 rpm and then added preheated ZrO2 to molten metal and stirred continuously

for 15min for proper mixing of reinforced material and base metal. Then they poured in the sand mould and get

desired shape of testing specimens. For microstructure testing by scanning electron micrograph (SEM). With the

help of this the particulate size is found to be 50nm. The distribution of ZrO2 is uniform and form good

interfacial bonding between Al 6061 and ZrO2, from this they clearly confirmed that the nano-particles

successfully embedded in the al matrix. And finally they concluded that the production of bulk nanocomposites

using conventional stir casting is effective, and they did some corrosion test on that specimen and they observed

that the corrosion rate of Al 6061 is higher than the nano-composites produced. By observing the total plots, we

can conclude that on increasing the percentage of nano ZrO2 in the nano-composite the corrosion rate decreased

simultaneously.

Ali Mazahery and Mohsen Ostad Shabani [3] in their investigation, the aluminum alloy A356 is filled with

nano SiC particles in their investigation using composite materials. Microstructures of the composite material

were studied using an optical microscope and a transmission electron microscope. Microscopic measurements of

the microstructures show uniform particle dispersion. With the addition of 3.5 per cent SiC nano-particles, the

maximum yield strength and ultimate tensile strength are obtained. In optical microscope examination study the

grain refining effect of nano particles. With rising particulate content which can be due to the increased surface

area of the nano SiC particles, the porosity amount increases slightly. In addition to nano particles, the

composites result in significant increase in hardness, yield strength and overall tensile strength. The dispersed

dimples with varying sizes are observed in the fractured surface of tensile specimens, confirming the high

ductility of the nano composites.

M. Ramachandra, et al. [4] the main aim of this research is to study the corrosion property of aluminum matrix

nanocomposite of an aluminum alloy (Al 6061) reinforced with nano ZrO2 particles. The mechanical and

physical properties due to their extremely grain size and high boundary volume fractions we called them as

Nano-Structure materials (1-100nm). They used 50nm sized zirconia as a reinforcement and Al 6061 as a base

material. In this paper they prepared composite material by using vortex technique. The base metal Al 6061 are

melted at a temperature of 800 0C. Preheated the reinforcement particle of nano ZrO2 at 650

0C and then it is

added to molten metal and stirred continuously. To increase the wettability, they added magnesium in small



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quantities additionally. Poured these molten metal into a cylindrical permanent metallic molds. In these the

reinforcement fractions varies from 0wt% to 7.5wt% in steps of 2.5wt%. For microstructure testing by scanning

electron micrograph (SEM). With the help of this the particulate size is found to be 50nm. The distribution of

ZrO2 is uniform and form good interfacial bonding between Al 6061 and ZrO2, from this they clearly confirmed

that the nano-particles successfully embedded in the al matrix. And finally they concluded that the production of

bulk nanocomposites using conventional stir casting is effective, and they did some corrosion test on that

specimen and they observed that the corrosion rate of Al 6061 is higher than the nano-composites produced. By

observing the total plots, we can conclude that on increasing the percentage of nano ZrO2 in the nano-composite

the corrosion rate decreased simultaneously.

P. Chinna sreenivas Rao, et al [5] in this investigation, metal matrix composites are formed using stir casting

method by reinforcing nano zirconia in Aluminum alloy Al 7075. The composite specimens are prepared by

changing the weight fraction percentage of the reinforced particles as 5 % and 10 %, respectively, and the

remaining aluminum alloy. Examine the mechanical properties of composite materials, such as tensile strength,

impact test, and hardness. By inserting nano zirconia particles, the tensile properties of the composite specimens

were considerably improved. At 95 per cent Al 7075 + 5 % ZrO2 the maximum tensile strength was observed,

135 N/mm2. The hardness properties are strengthened by adding 10 % of nano zirconia (ZrO2) with 90 percent

of Al 7075, at 10 % nano zirconia (ZrO2) with 90 % Al 7075 being 104 the highest hardness was observed.

III. OBJECTIVE

1. Selection of Al 6061 alloy as base matrix and Nano zirconia (ZrO2) as reinforcement for the present work.

2. Preparation of Aluminium Matrix Nano Composites (AMNCs) by adding nano ZrO2 with different wt% (0,

0.5, 1, 1.5 and 2) reinforcement and add constant 3 wt% of Mg to improve the wettability in the method of

Stir casting technique.

3. Study of tensile strength and hardness of composites by preparing specimens as per ASTM standard.

4. Study of various micro structural changes on the metal matrix composites by using Scanning Electron

Microscope (SEM) photographs.

IV. EXPERIMENTAL METHODOLOGY

4.1 Selection Of Matrix Alloy

Al 6061 was chosen as the matrix of the composite in the composite in the current study because of it is easily

machinable. It is used in applications that require a high resistance to weight ratio, as well as good resistance to

corrosion and wear. Al6061 is usually used in train coaches, truck frames, ship construction, bridges and

military bridges, transport towers, boiler making and motorboats for heavy duty structures.

Table-1: Chemical composition of the Aluminium 6061 alloy and magnesium.

Chemical composition (wt %)

Material

Al 6061 Mg

Fe 0.7 0.020

Mn 0.15 0.002

Cu 0.4 0.016

Zn 0.25 0.002

Si 0.8 0.006

Mg 1.2 Bal.

Al Bal. 0.023



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4.2 SELECTION OF REINFORCEMENT

In this investigation, Nano Zirconia (ZrO2) size 30-50 nm was used for the reinforcement and the supplier for

this powder is Ultrananotech pvt. ltd, Bangaloru some of the properties of nano ZrO2 are shown in Table 2.

Table-2: Properties of nano ZrO2 powder

Table-3: Chemical composition of nano ZrO2 powder

Constituent Wt%

Al2O3 0.02

SiO2 0.03

Fe2O3 0.005

CaO 0.005

MgO 0.01

TiO2 0.03

ZrO2 99.9

4.3 Fabrication Procedure

In a method of stir casting, the reinforcing phases are dispersed by mechanical stirring into molten matrix. A

specially designed furnace in which a remote control mechanism is used to pump melt into the mould from its

bottom. This type of furnace does not require the user to lift and pour the melt into the mould.

The Al 6061 was melted in a graphite crucible which was repeatedly cleaned to prevent contamination. The

graphite crucible has a cylindrical shape at the middle of its bottom, with an inner diameter of 120 mm and a

hole of 30 mm in diameter. The crucible of graphite was mounted inside the furnace. A stirring mechanism had

been made to stir the melt in the crucible. A stirrer was operated by digitally. The stirrer was connected by

screw coupling arrangement to the motor shaft. Even a provision was made for height adjustment of the stirrer.

A power supply unit was connected to supply 240 V voltage. A calibrated thermocouple was used to measure

the furnace temperature by placing it inside the furnace.

Initial start the furnace. Ingots of aluminium alloy 6061 were melted at 750 ºC and mixing the ZrO2 particles

were preheated at 200 ºC for 20 min to make in hot air oven. To overcome wettability problem 3 wt% of

magnesium was added in crucible. The furnace temperature was first raised at 800 ºC after add the Al 6061 to

melt completely, after completely melted a magnesium lump of 3 wt% was wrapped by aluminium foil and

Sl.No Properties Values

1 Density (kg/cm3) 5.89

2 Poisson's Ratio 0.32

3 Young's modulus (GPa) 207

4 Melting point oC 1843

5 Boiling point oC 4371

6 Appearance White powder

7 Solubility in water insoluble



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plunged into the melting slurry and allow to melt. After melting Al 6061 and magnesium, and add degasser

tablet in the crucible. Degas tablet was used to remove the slag. After removal of slag, stirrer was dipped into

the molten material by using controller and start the stirrer and the speed of the stirrer was kept constant at 300

rpm stir the molten slurry upto vertex formation. At this stage the weighed amount of preheated ZrO2 particles

(0, 0.5, 1.0, 1.5 and 2 wt %) were added, mixing was carried out for 10 minutes at a stirring rate of 300 rpm.

After final mixing process, pouring of the composite slurry has been carried out in bottom pouring die. The die

was preheated at 300 ºC to easy flow. To cool the mould, kept it in room temperature. After solidification of the

nano-composite this composite goes to machining process.

Fig 1: Computerized bottom stir casting machine Fig 2: Composite specimen in mould

Table-4: Nomenclature of nano composition.

Designation of composite / alloy Al 6061 (wt%) Magnesium (wt%) Particle (wt%)

AMP 97 3 0

AMP 0.5 96.5 3 0.5

AMP 1 96 3 1

AMP 1.5 95.5 3 1.5

AMP 2 95 3 2

Where, A: Aluminium alloy (Al 6061)

M: Magnesium (Mg)

P: Nano zirconium dioxide (ZrO2)

V. RESULTS AND DISCUSSION

5.1 Morphology Of Nano ZrO2 Partcle

The size and shape of the nano ZrO2 particles in the powder was observed under SEM and TEM. The results are

shown in Fig 3.1(a) and Fig 3.1(b). The size of particles is in the range between 30 nm to 90 nm and the shape

of the particles are irregular in shape. The nano ZrO2 particles in the powder have been observed under SEM.



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Fig-3(a): SEM micrographs showing size and shape of the nano ZrO2 powder

Fig-3(b): TEM micrographs showing size and shape of the nano ZrO2 powder

Fig-4: XRD pattern of ZrO2 particles used in casting of Al 6061 (Mg) - ZrO2

Using X-ray diffractometer in the two theta range of 10-900 using Cu as target material, Kα radiation and nickel

filter, the powder was examined for their X-ray diffraction pattern (XRD) Step size and dwell time were

appropriately adjusted, which was used to identify different phases with the help of the inorganic JCPDS (Joint

a a



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Committee on Powder Diffraction Standards) X-ray diffraction data card available from the International Center

for Diffraction Data as the Powder Diffraction File (PDF), which shows that the ZrO2 particles are fairly pure.

The XRD pattern of ZrO2 particles used in the Al 6061 (Mg) - ZrO2 composite synthesis is shown in Fig 4.

5.2 Sem Results

A scanning electron microscope (SEM) scans a focused electron beam to create an image over a surface. The

electrons in the beam interact with the sample, producing different signals that can be used to gather

information about the topography and composition of the surface. From Fig 5 (a, b, c, d, and e) shows the

scanning electron micrographs of nano-composite. Figures shows the distribution of Al 6061 with nano

zirconia.

a b

c d



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Fig-5: SEM micrographs of different nano composite.

(a) AM, (b) AMP0.5, (c) AMP1, (d) AMP1.5, (e) APM2 respectively.

The SEM shows clearly the uniform distribution of nano zirconium dioxide and Mg in the matrix. There was a

good interfacial bonding between the particles and matrix material. The composite AMP 2 has more distributed

phases than that in the composite AMP 0.5.

5.3 Hardness Of Nano Composite

Average Brinell hardness was measured for nano composites formed by addition of nano ZrO2 powder, with a 5

mm hardened Steel ball indenter of 250 kg load applied to the sample for 30 seconds, and then the indentation

diameter was measured with the aid of the tool manufacturer's microscope. For through Indentation, the

corresponding hardness was calculated using an average of two diameters measured perpendicular to one

another. At least three indentations were made at different locations on each sample for hardness measurement

and the average of these values was recorded as the average hardness value of the specimen. The Fig 6 shows

that hardness of the cast composite increases with increasing addition of nano ZrO2 particles to base alloy.

BHN =

√

Where, P: load [kg]

D: diameter of the ball [mm]

d: diameter of indentation [mm]

e



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Fig-6: Variation of average hardness of Al 6061 alloy and cast composites

5.4 Tensile Properties Of Nano Composition

Fig-7: Schematic representation of tensile specimen ASTM E8 standard

The tensile test specimen were prepared as per ASTM E8 standards as shown in Fig 5. Three specimens were

tested for each trail. Nano composites were tested under uniaxial tension on Universal Testing Machine (UTM),

at an extension rate 1 mm/min. yield strength and tensile strength of cast composites improved with the increase

in addition of nano ZrO2, the nano composite with 2 wt% of ZrO2 exhibiting highest yield strength and tensile

strength. and 1.5 wt% has highest percentage of elongation. The comparison of average yield strength, ultimate

tensile strength and percentage elongation of cast alloy and composites, are shown in Fig 7, Fig 8 and Fig 9

respectively.

Fig-7: Yield stress with increasing addition of nano ZrO2 powder

0

20

40

60

80

0 0.5 1 1.5 2

BH

N

Weight percentage of nano ZrO2 particles added

Brinell hardness nunber

0

20

40

60

80

100

0 0.5 1 1.5 2

Yie

ld s

tren

gth

in M

Pa


Yeild strength



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Fig-8: Tensile strength with increasing addition of nano ZrO2 powder

Fig-9: Percentage of elongation with increasing addition of nano ZrO2 powder

VI. CONCLUSIONS

The aluminium metal matrix composites have been produced successfully by the addition of 0, 0.5, 1, 1.5 and 2

wt% of nano zirconium dioxide (ZrO2) powder to molten Al 6061 alloy by liquid stir casting method followed

by casting in mould. The effect of growing quantities of nano ZrO2 powder addition on cast microstructure

evolution and its effects on the mechanical properties of the resulting composite has been investigated. The

results of this analysis are summarized below.

1. Stir casting technique (Liquid Metallurgy) was successfully adopted in the preparation of Al 6061 (Mg) –

nano ZrO2 powder alloy and composites containing 0, 0.5, 1, 1.5 and 2 wt% of nano ZrO2 powder

reinforcement.

2. XRD analysis shows the nano ZrO2 particles are fairly pure and SEM metallographic study revealed the

presence of ZrO2 particles in the composites with fairly homogeneous dispersion.

3. The hardness of the composites is improve with the increase in nano ZrO2 reinforcement and the higher

hardness 66.5 BHN noticed at 2 wt% of nano ZrO2 powder addition.

4. The composite with 2 wt% of nano ZrO2 powder addition exhibited good yield strength of 82.851 MPa,

tensile strength of 128.148 MPa and 0 wt% of nano ZrO2 addition exhibited good percentage of elongation

around 6.18% compared to all other composites.

0

20

40

60

80

100

120

140

0 0.5 1 1.5 2Ten

sile

str

ength

in M

Pa


Ultimate tensile strength

0

2

4

6

8

0 0.5 1 1.5 2

Per

centa

ge

of

elongat

ion

(%)


Elongation



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VII. REFERENCES

[1] K. B. Girish, Rishav Kumar, Sameer Ahamed, “Microstructure and Wear Properties of Zirconium

Nano Metal Matrix Composites”, ISSN: 2277-9655 Issue 3, June 2016, pp 1-9.

[2] Dharmesh M Patoliya, Sunil Sharma, “Preparation and Characterization of Zirconium Dioxide

Reinforced Aluminium Metal Matrix Composites”, Volume 4, Issue 5, May 2015, pp 2347-6710.

[3] Ali Mazahery, Mohsen Ostad Shabani, “Characterization of cast A356 alloy reinforced with nano SiC

Composites”, Volume 4, 23 May 2011, pp 275-280.

[4] M. Ramachandra, A. Abhishek, P. Siddeshwar, “Hardness and Wear Resistance of ZrO2 Nano particle

Reinforced Al Nanocomposites Produced by Powder Metallurgy”, Volume 10, October 2015, pp 212-

219.

[5] P. Chinni Sreenivas Rao, T. Prasad, M. Harish, “Evaluation of Mechanical Properties of Al 7075 –

ZrO2 Metal Matrix Composite by using Stir Casting Technique”, Volume 6, Issue 4, April 2017, pp

377-381.

FABRICATION OF STUDY OF MECHANICAL PROPERTIES ......FABRICATION OF STUDY OF MECHANICAL PROPERTIES OF ALUMINIUM ALLOY 6061 REINFORCED WITH NANO ZIRCONIA Ravi Kiran R*1, Ghanaraja S*2

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FABRICATION OF STUDY OF MECHANICAL PROPERTIES ......FABRICATION OF STUDY OF MECHANICAL PROPERTIES OF ALUMINIUM ALLOY 6061 REINFORCED WITH NANO ZIRCONIA Ravi Kiran R1, Ghanaraja S2