A Project Work onMECHANICAL BEHAVIOUR OF Al ALLOY

REINFORCED WITH Al2O3/RICE HUSK ASH PARTICLES SYNTHESIZED BY STIR CASTIING

University VOC College of Engineering

Tuticorin Campus

PROJECT MEMBERS

S. Marimuthu @ Mathavan [953211114021]P. Pon Rajesh Kumar [953211114032]R. Sivagaminathan [953211114049]M. Vignesh [953211114055]

PROJECT GUIDE : Mr. S. AMAL BOSCO JUDE(Ph.D), AP/MECH

PROJECT CO-GUIDE : Mr. P. VENKALAKUMAR, TF/MECH

ABSTRACT

In the past few years the global need for low cost, high performance and good quality materials has caused a shift in research from monolithic to composite materials.

Present work is focused on the study of behavior of Aluminum Alloy (AA6061) with Alumina and rice husk ash particulate composite fabricated by double layer feeding stir casting technique.

Different wt% of alumina powder and rice husk ash is used as reinforcement phase in this AMMC.

The mechanical behaviour of these composites with different wt% of alumina and rice husk ash are investigated by Tensile Test, Hardness Test, Flexural Test, Density Measurement and Microstructural Behaviour.

PROBLEM DEFINITION

In India, we are mostly using coal based fuel cars which is non-conventional source of energy.

So fuel economy became dominant while designing cars in India.

One approach to increase an automobile’s fuel economy by reducing vehicle weight and friction loss simultaneously is to remove the cast iron cylinder block and replace them with a lighter more thermally efficient material.

INTRODUCTION TO HYBRID MMC

Composites – mixture of two/more constituents insoluble in each other.

Properties better than sum of their constituents.

Hybrid Composites - Incorporation of several different types of particulates into single matrix.

Advantages of Aluminum Matrix Composite (AMC)• Low density• High Strength• Superior creep resistance• High damping resistance• Good dimensional stability

METHODOLOGY

MATERIALS

Aluminum Alloy Alumina Powder

Rice Husk Ash(After

Pretreatment)

FABRICATION(Stir Casting)

AMC with 2 wt% of Alumina & RHA

AMC with 4 wt% of

Alumina & RHA

TESTING(Density Measurement,

Tensile Test, Hardness Test, Flexural Test)

ALUMINIUM ALLOY

The aluminum alloy used in our project work is AA 6061, which has major composition of magnesium and silica.

The Chemical Composition of AA 6061 is given below

Element

Mg Fe Si Cu Mn V Ti Al

Weight %

1.08 0.17 0.63 0.32 0.52 0.01 0.02 Remainder

Alumina Powder

The reinforcement of Alumina (Al2O3) with the average size of 25µm into aluminum matrix improves

Hard, Wear Resistant

Resist alkali attacks at high temperature

Good thermal conductivity High Strength and Stiffness

Rice Husk Ash (RHA)

The second particulate reinforcement is RHA obtained from Rice Husk

Rice Husk is used in small boilers for heat generation

The RHA obtained is rich in silica and carbon content, when disposed in environment causes pollution.

In order to used RHA as a reinforcement in Aluminum matrix Composite, it has to be pretreated to remove carbonaceous material.

Pretreatment of RHA

The Rice Husk is thoroughly washed with water to remove dust and dried at room temperature for 1 day.

Heated to 200˚C for 1h to remove moisture and volatile materials.

Heated to 600˚C for 5h to remove carbonaceous material.

It was observed that colour of ash changes from black to grayish white.

The change in colour is due to removal of carbonaceous material.

The end product is Silica rich RHA.

Before heat treatment After heat treatment

XRD pattern of heat treated RHA

Chemical composition of heat treated RHA

FABRICATION OF ALUMINUM MATRIX COMPOSITES

Stir casting (Melt stirring) process, which is one of the liquid metallurgy technique is used to AMC.

The advantages of using this techniques are

wide selection of materials better matrix-particle bonding easier control of matrix structure simple and less expensive flexibility

However some problems with stir casting includes

poor wettability porosity heterogeneous distribution

Improve Wettability

• Molten matrix cannot wet the surface of reinforcement material

• Hence alumina and RHA particles donot mix with aluminum matrix, instead float on melt surface due to

1.Surface tension2.Large specific surface area3.Oxide films on melt surface

• To eradicate this problem 1 wt% MAGNESIUM is added to the composites.

• The addition of magnesium improves wettability of reinforcements.

• The reinforcements are also preheated before processing to remove adsorbed gases in the particle surface.

MAGNESIUM POWDER

Reduce Porosity

Porosity is due to presence of insoluble gases such as hydrogen present in the molten aluminum alloy.

The insoluble gases can be remove with the help of degassing tablet.

The degassing tablet is Hexa Methyl Formate which is an organic compound that removes insoluble gases from the molten aluminum alloy.

Degassing Tablet

Homogeneous Distribution The next problem is distribution of reinforcement in the molten matrix

After Wetting particles tends to float or sink according to density difference between matrix reinforcements and matrix alloy melt

Thus leading to high tendency for clustering

To accompany uniform distribution, the following factors has to be considered

The number of blades in the stirrer should be 4 The blade angle must be 45˚ or 60˚ Blade should 20mm above the bottom of the crucible The feed rate of reinforcements must be uniform The flow pattern of reinforcements should from outward to

inward The metal pouring rate should be constant to avoid bubble

formation.

Hand Stirrer Mechanical Stirrer Setup

Blades of Mechanical Stirrer

STIR CASTING EQUIPMENT

STIR CASTING PROCEDUREAluminum alloy is

weighed and cut into pieces and placed in

graphite crucible

Preheating of weighed Alumina & RHA to 200˚C for 1h

Al alloy melted in furnace at 800˚C

Addition of degassing tablet

Addition of 1 wt% Mg powder

Addition of preheated Alumina to crucible

Addition of preheated RHA to

crucible

Mechanical Stirring at 950rpm

Final casting poured to preheated mould

Sample Matrix [ A6061 Alloy ]

Reinforcements

Alumina Rice Husk Ash

1. 100 0 0

2. 96 2 2

3. 92 4 4

Composition of Samples

AA 6061 pieces in Graphite Crucible of furnaceWeighing of Alumina

Weighing of RHA

Hand Stirring Mechanical Stirring

Pouring of Casting to mould Finished Product

RESULTS AND DISCUSSION

The Aluminum Matrix composites with 2 and 4 wt% of Alumina & RHA is subjected to following measurements to evaluate its mechanical properties

Tensile Test Hardness Test (Brinell’s Hardness) Flexural Test Density Measurement Micro-structural Behaviour using SEM

Tensile Test

The specimen for tensile test were prepared according to ASTM E8 standard

This is used to determine elastic limit, elongation, proportional limit, and reduction in area, ultimate tensile strength, yield point and yield strength

The Ultimate Tensile Strength (UTS) and percentage elongation of the specimen are tabulated

Pure 2% 4%708090

100

80 84

96

Wt% of RHA and Al2O3

UTS

MPa

Ultimate Tensile Strength (UTS) of fabricated samples

Pure 2% 4%05

1015 14

6.84 4.8

Wt% of RHA and Al2O3

% e

long

atio

n

% elongation of fabricated samples

Hardness Test

Hardness of the hybrid composites were measured using a standard Brinell’s Hardness tester as per ASTM E10 standards.

Where F is the applied load, D is the diameter of the steel ball and d is the size of the indent.

Pure 2% 4%020406080

3357 61

Wt% of RHA and Al2O3

Har

dnes

s BH

N

Hardness of Fabricated Samples

Flexural Test

The transverse bending specimen is employed in which a rod specimen having a rectangular cross section is bent until fracture using three-point loading technique. The stress at failure is known as flexural strength. The Flexural strength is calculated for the unreinforced and A6061/ Al2O3 /RHA composites using 3 point loading technique.

Test piece after flexural test

Pure 2% 4%0

200

400164

281407

Wt% of RHA and Al2O3

Flex

ural

St

reng

th

MPa

Flexural Test of Fabricated Samples

Density Measurement

Density measurement is carried out on base material and reinforced sample using Archimedes principle.

The formulae used to calculate density is given below

ρmmc = mρw/(m-m1)

where m is the mass of the composite sample in air m1 is the mass of the same composite sample in distilled water ρw is the density of the distilled water.The density of distilled water at 20 ◦C is 998 kg/m3.

Pure 2% 4%26402660268027002720274027602780

2755

27102690

Density of Fabricated Samples

Wt% of RHA and Al2O3

Den

sity

(K

g/m

3)

Microstructural Behaviour

The SEM is a microscope that uses electrons instead of light to form an image.

Good retention of rice husk ash particles was clearly seen in the microstructures of A6061/ Al2O3 /RHA composites.

I. SEM picture of A6061/2% Al2O3 &RHA Composites II.SEM picture of A6061/4% Al2O3 &RHA Composites

Mechanical Properties of Matrix and hybrid composites

S. no. Sample Hardne

ss BHNUTS MPa

% elongati

on

Flexural TestMPa

Density

Kg/m3

1. AA 6061 33 80 14 164 2755

2.AA 6061 with 2wt% of RHA

and Al2O3

57 84 6.84 281 2710

3.AA 6061 with 2wt% of RHA

and Al2O3

61 96 4.8 407 2690

Discussions The results confirmed that stir formed AA 6061 with RHA / Al2O3 reinforced composites is clearly superior to base AA 6061 in the comparison of tensile strength, Flexural strength as well as Hardness.

Dispersion of RHA / Al2O3 particles in aluminum matrix is investigated using SEM image.

It appears from this study that UTS starts increases with increase in weight percentage of RHA and Al2O3 in the matrix.

The Hardness increases after addition of RHA / Al2O3 particles in the matrix.

Stir casting process, stirrer design and position, stirring speed and time, particle- preheating temperature, particle incorporation rate etc. are the important process parameters.

Conclusions

The results confirmed that the stir formed Al alloy with Al2O3&RHA reinforced composites is clearly superior to base Al alloy in the comparison of Ultimate Tensile Strength, Hardness and Flexural Strength.

Dispersion of Al2O3&RHA particles in the aluminum matrix improves hardness and reduce density of the matrix material.

Aluminum matrix composites have been successfully fabricated by stir casting technique with fairly uniform distribution of Al2O3&RHA particles.

ACKNOWLEDGEMENTS

We convey our sincere thanks to

Dr.S.SANKARAN, Ph.D., Associate Professor, Department of Metallurgical & Materials Engineering, IIT Madras

Mr.N.THIRUNAVUKARASU, Sr. Technician, Department of Metallurgical & Materials Engineering, IIT Madras

Mr.N.SANKARESWARAN,M.E.,(Ph.D), AP/Mech, Anna University – Tirunelveli Region

We are indeed very thankful to our

Dean, Dr.N.SHENBAGA VINAYAGA MOORTHI, M.E, Ph.D.

HOD, Dr.R.A.MALAIRAJAN,M.E.,Ph.D.,M.B.A., AP/Mech

Guide, Mr. S. AMAL BOSCO JUDE, M.E.,(Ph.D), AP/Mech

Co-Guide, Mr.P.VENGALAKUMAR, M.E., TF/Mech

Project Co-ordinator, Mr.A.KARTHIKEYAN, M.E.,(Ph.D), AP/Mech

References

1. Autar K.Kaw (2013) ‘Mechanics of Composite Materials’, CRC press.

2. Balasubramanian R (2010) ‘callister’s Material Science and Engineering’, Wiley-India (P) Ltd.

3. Rajeshkumar Gangaram Bhandare et al, 2013. Preparation of Aluminum Matrix Composite by using Stir Casting Method, IJEAT, ISSN:2249-8958, Volume-3, Issue-2.

4. Atunaya, C.U., Aigbodicon, V.S., 2014. Evaluation of Al-Cu-Mg alloy / bean pod ash nanoparticles synthesis by double layer feeding-stir casting method. Elsevier Ltd.

5. Himanush Kala, Mer, K.K.S., Sandeep Kumar, 2014. A Review on Mechanical and Tribological Behaviors of Stir Cast Aluminum Matrix Composites. 2211-8128, Elsevier Ltd.

THANK YOU