123504-Grey Relational Analysis Approach for Optimization of Wear (2)

GREY RELATIONAL ANALYSIS APPROACH FOR OPTIMIZATION OF WEAR CHARACTERISTIC OF HYBRID MMCS

A Dissertation

Submitted to the

Department of Mechanical Engineering in

Partial Fulfillment of the Requirements for the Award of the Degree

of

MASTER OF TECHNOLOGY IN

MANUFACTURING ENGINEERING

SUBMITTED BY

DHARMENDRA KUMAR SINGH (ROLL NO. 123504)

UNDER THE GUIDANCE OF

Dr. L.KRISHNANAND HEAD OF DEPARTMENT

DEPARTMENT OF MECHANICAL ENGINEERING

NATIONAL INSTITUTE OF TECHNOLOGY WARANGAL-506004 (TELANGANA)

2012-2014

Dissertation Approval for M.Tech.

This project work entitled GREY RELATIONAL ANALYSIS APPROACH FOR

OPTIMIZATION OF WEAR CHARACTERISTIC OF HYBRID MMCS. by

DHARMENDRA KUMAR SINGH, Roll. No. 123504 is approved for the degree of Master

of Technology in Manufacturing Engineering.

Examiners

--------------------------------

--------------------------------

--------------------------------

Supervisor

--------------------------------

Chairman

--------------------------------

Date:

Place: Warangal

Department of Mechanical Engineering

National Institute of Technology

Warangal-506004

CERTIFICATE

This is to certify that the project titled GREY RELATIONAL ANALYSIS APPROACH

FOR OPTIMIZATION OF WEAR CHARACTERISTIC OF HYBRID MMCS is a

bonafide work done by Mr Dharmendra Kumar Singh (Roll No 123504), in partial

fulfilment of the requirements for the award of degree of Master of Technology in

(Manufacturing Engineering) and submitted to the Department of Mechanical Engineering,

National Institute of Technology, Warangal.

Dr. A. Venu Gopal

Head of Production Engineering Division


NIT Warangal

Dr. N.Venkaiah

Course Co-ordinator


NIT Warangal

Dr. L. Krishnanand

Project Guide & Head of the Department


NIT Warangal

DEPARTMENT OF MECHANICAL ENGINEERING

NATIONAL INSTITUTE OF TECHNOLOGY WARANGAL 506004, Telangana

DECLARATION

I declare that this written submission represents my ideas in my own words and where

others' ideas or words have been included, I have adequately cited and referenced the original

sources. I also declare that I have adhered to all principles of academic honesty and integrity

and have not misrepresented or fabricated or falsified any idea / data / fact / source in my

submission. I understand that any violation of the above will be cause for disciplinary action

by the Institute and can also evoke penal action from the sources which have thus not been

properly cited or from whom proper permission has not been taken when needed.

Dharmendra Kumar Singh

NIT Warangal

ACKNOWLEDGEMENTS

I take this golden opportunity to express my heartfelt thanks and my profound sense of

gratitude to my project guide Dr.L.Krishnanand and Head of Mechanical Engineering

Department for their valuable suggestions, guidance and encouragement throughout my thesis

work.

I express my sincere thanks to Dr.A.Venu Gopal, Head of Production Engineering Division

for his valuable suggestions, constructive cooperation and encouragement at various stages of

the project work.

I express my sincere thanks to Dr. N. Venkaiah, coordinator M.Tech. Manufacturing

engineering, National Institute of Technology- Warangal, to provide facilities to carry out the

experimental works.

I express my sincere thanks to Dr. Ashit Khanre, Asst. Professor of Metallurgy Department

to provide facilities to carry out the experimental works.

I express my sincere thanks to Mr.K.Satyanarayana Ph.D. Scholar for his help during the

project work.

I express my sincere thanks to Mr. S.Sai Phd. Scholar Metallurgy Department for his support

and guidance throughout my project work.

I cannot close these prefatory remarks without expressing my deep sense of gratitude and

reverence to the authors of the various papers I have used and referred to in order to complete

my research work.

Last but not least, I also express my wholehearted gratitude in huge measure to my family, all

my classmates and friends, for their everlasting help, encouragement and moral support

throughout my entire work.

Dharmendra Kumar Singh

Roll No. 123504

ABSTRACT

Aluminium Metal Matrix Hybrid Composite is relatively new material that has proved

its position in aerospace, automobile industries and other engineering design application due

to their low density and strong corrosion resistance and wear resistance, higher hardness, low

thermal coefficient of expansion as compared to conventional metals and alloys. The excellent

mechanical properties of these materials and relatively low production cost make them a very

attractive for a variety of applications both from scientific and technological viewpoints.

The aim involved in designing metal matrix hybrid composite materials is to combine the

desirable attributes of metals and Ceramics. Need for improved performance has lead to the

design and selection of newer variants of the composites.

Present work is focused on the study of behavior of AA6061/SiCp/C composites

produced by the powder metallurgy process by taking different Reinforcement C-% by weight

(0, 3, 5, and 7%). Sintered density, Hardness Test, SEM test, EDAX and Wear test

calculations have been performed on the samples obtained by the powder metallurgy process.

Experiments have been designed using L16 Taguchi orthogonal array to acquire the

wear data. Grey relational analysis approach is used for optimization of process parameters in

order to obtain minimum wear of the component. Conformation experiment has also been

conducted using optimal combination of process parameters which is found by analyzing

GRG value by Taguchi analysis in order to verify the results. An analysis of variance is

employed to investigate the influence of four controlling parameters, viz., SiC + C (Graphite)

composition, normal load, sliding distance & sliding speed on dry sliding wear of the

composites. The optimal combination of the four controlling parameters has been obtained for

minimum wear loss. The micro-structural study and EDAX of the produced sample and worn

out surface has also been performed.

I

TABLE OF CONTENTS

CONTENT PAGE NO.

ABSTRACT I

TABLE OF CONTENTS III

LIST OF FIGURES IV

LIST OF TABLES V

LIST OF NOTATION VI

Chapter 1 Introduction ........................................................................................................... 1

1.1 Metal Matrix Composites (MMCs) .......................................................................... 2

1.1.1 Types Of MMCs ................................................................................................ 3

1.1.2 Applications Of MMCs .................................................................................... 5

1.1.3 Necessity of MMCs . ....................................................................................... 7

1.2 Aluminium And Aluminium Alloys .......................................................................... 7

1.2.1 Classification Of Aluminium Alloys ................................................................... 8

1.2.2 International Designation System For Aluminium Alloys .................................. 8

1.2.3 Chemical Composition Of AA6061 Aluminium Alloys ................................... 10

1.3 Reinforcements ........................................................................................................ 10

1.3.1 Particulate Reinforcement ................................................................................. 11

1.4 Production Of Aluminium MMCs ......................................................................... 11

1.4.1 Liquid State Processing ..................................................................................... 12

1.4.2 Solid State Processing ....................................................................................... 15

1.5 Interface ................................................................................................................... 17

1.6 Basic Terminology Used In Experimental Analysis ............................................... 17

1.7 Hardness .................................................................................................................. 18

1.8 Wear And Wear Mechanism ................................................................................... 18

1.8.1 Wear................................................................................................................... 18

II

1.8.2 Types Of Wear................................................................................................... 19

1.8.3 Wear Mechanism ............................................................................................... 19

1.9 Importance of Hybrid MMC..............................................................................20

2.0 Wear study on MMCs.........................................................................................21

Chapter 2 Literatu Survey .................................................................................................... 22

2.1 Literature Survey ..................................................................................................... 22

2.2 Motivation For The Project ..................................................................................... 25

2.3 Challenges And Opportunities ................................................................................ 26

2.4 Objectives ................................................................................................................ 27

2.5 Problem Statement ................................................................................................... 28

Chapter 3 Experimental Procedure ..................................................................................... 29

3.1 Work Material.......................................................................................................... 29

3.1.1 Chemical Composition Of Base Alloy Powder ................................................. 29

3.2 Fabrication Of Al MMCs Pallets By Powder Metallurgy ...................................... 29

3.2.1 Powder Metallurgy ............................................................................................ 31

3.3 Physical Properties Of Produced Pallets ................................................................. 38

3.3.1 Density Of Produced Pallets .............................................................................. 38

3.3.2 Theoretical Density............................................................................................ 38

3.3.3 Apparent Density ............................................................................................... 38

3.3.4 Green Density .................................................................................................... 38

3.3.5 Sintered Density ................................................................................................ 42

3.4 Densification Factor ................................................................................................ 42

3.5 Mechanical Behaviour Of Produced Pallets ............................................................ 39

3.5.1 Hardness Of Produced Pallets Using Rockwell Tester ..................................... 39

3.6 Wear And Wear Mechanism ................................................................................... 41

3.6.1 Wear................................................................................................................... 41

3.6.2 Wear Mechanism ............................................................................................... 41

III

Chapter 4 Methodology48

4.1 Taguchi methodology.48

4.2 Signal to Noise Ratio..48

4.3 Design Of Experiment48

4.4 Taguchi based Grey Relational Analysis to Optimize the Multi Response.49

4.5 Grey Relational Analysis..50

4.6 Predictive Equation53

Chapter 5 Analysis Of Results And Discussion ................................................................ 54

5.1 Density Of Produced Pallets .................................................................................... 54

5.1.1 Theoretical Density & Composition Of Each Composites ................................ 54

5.1.2 Sintered Density Of Produced Pallets .............................................................. 54

5.2 Densification Factor Of Produced Pallet ................................................................. 56

5.3 Hardness Test Using Rockwell Hardness Tester Wear Test Using Pin-On-Disk

Wear And Friction Tester .................................................................................................... 56

5.3.1 Process Parameters And Their Levels ............................................................... 57

5.4 Design Of Experiment For Wear Test by Taguchi Orthogonal L16 Array .... 57

5.5 Response Table for the given Taguchi L16 Orthogonal Array .............................. 58

5.5.1 Grey Relational Analysis for multiple response ................................................ 59

5.6 Taguchi Analysis for Wear Test ............................................................................ 60

5.6.1 Taguchi Analysis for GRG ............................................................................... 62

5.7 Microstructure Study ............................................................................................... 65

5.8 Wear Mechanism ..................................................................................................... 68

Conclusion .............................................................................................................................. 73

Future scope ........................................................................................................................... 74

References............................................................................................................................... 75

IV

LIST OF FIGURES

Figure No. Description Page Number

Figure 1 Metal Matrix Composites (MMCs) Sector Study Scope ........................................... 1

Figure 2 Different Types of Metal Matrix Composites (MMCs)............................................. 4

Figure 3 Applications Of MMCs and Their Benifits in Existing Application ......................... 6

Figure 4 Various Steps Involved in Synthesis of Al-SiCp Composites by P/M Technique ... 16

Figure 5 Flow Chart of Powder Metallurgy Method and Specimen Analysis ........................ 29

Figure 6 Powder Production by Gas Atomization ................................................................... 32

Figure 7 SEM Image of Raw Materials Powders .................................................................... 33

Figure 8 Electronic Weighing Balance .................................................................................... 35

Figure 9 Terbula Blender ......................................................................................................... 35

Figure 10 Die used for Pallet Preparation ............................................................................... 36

Figure 11 Green Pallet Produced after Cold Die Compaction Placed in a Boat ..................... 36

Figure 12 Hydraulic Press for Compaction ............................................................................. 37

Figure 13 Steps in Sintering Geometry ................................................................................... 39

Figure 14 Property Change During Sintering Cycle ............................................................... 39

Figure 15 Inert Atmosphere Tubular Furnace ........................................................................ 39

Figure 16 Sintered Pallets Produced after Sintering Under N2 Atmosphere ........................... 40

Figure 17 Thermal Cycle for Microwave and Conventional Sintering of Al-Alloys .............. 40

Figure 18 Rockwell Hardness Tester....................................................................................... 43

Figure 19 Pallets after Hardness Test ...................................................................................... 43

Figure 20 Pin-on-Disk Wear and Friction Force Tester .......................................................... 45

V

LIST OF TABLES

Table No. Description Page number

Table 1 Designation System for Aluminium Alloys ................................................................. 9

Table 2 Particle Size and Purity of Raw Material ..................................................................... 9

Table 3 Chemical Composition of AA6061 Aluminium Alloys ............................................. 10

Table 4 Some Important Reinforcement for Metal Matrix Composites .................................. 11

Table 5 Chemical Composition of Base Alloy (AA6061) for Composites ............................. 31

Table 6 Particle Size in Terms of Number of Mesh Vs Microns ............................................ 32

Table 7 Array Selector ............................................................................................................. 49

Table 8 L16 Orthogonal Array ................................................................................................ 49

Table 10 Weight and Composition of Plane AA6061(90%) + SiC (10%) ............................. 50

Table 11 Weight and Composition of AA6061 (87%) + SiC (10% )+C(3%) ......................... 50

Table 12 Weight and Composition of AA6061 (85%) + SiC (10%)+C(5%) .......................... 51

Table 13 Weight and Composition of AA6061 (83%) + SiC (10% )+C(7%) ......................... 51

Table 14 Theoretical Density of Pallets .................................................................................. 52

Table 15 Sintered Density of Produced Pallets ....................................................................... 53

Table 15 Densification Factor of Produced Pallets ................................................................. 54

Table 16 Hardness Table for Produced Pallets at Different Conditions .................................. 56

Table 17 Process Parameters and Their Levels for Wear Test ................................................ 57

Table 18 L16 Orthogonal Array for wear test ......................................................................... 57

Table 19 Response Table for the given L16 Orthogonal Array.58

Table 20 Grey Relational Analysis for Multiple Responses..59

Table 21 GRG value of Experimental Run at Different Levels ............................................. 59

Table 22 Analysis of Variance of means for means of wear ................................................... 60

Table 23 Response Table for means of S/N Ratio .................................................................. 61

Table 24 Analysis of Variance of means for GRG .................................................................. 62

VI

List of Notation

1. MMCs = Metal Matrix Composites

2. AMCs = Aluminium Matrix Composites

3. PMCs = Polymer Matrix Composites

4. PMMCs = Particulates Reinforced Metal Matrix Composites

5. PAMCs = Particulates Aluminium Matrix Composites

6. P/M Processing = Powder Metallurgy Processing

7. CFMMCs = Continuous Fibre Metal Matrix Composites

8. CFAMCs = Continuous Fibre Aluminium Matrix Composites

9. SFMMCs = Short Fibre Metal Matrix Composites

10. ANSI = American National Standard Institute

11. SiCp = Silicon Carbide Particles

12. Al2O3 = Aluminium Oxide

13. TiB2 = Titanium Boride

14. ISO = International Organization for Standardization

15. DF = Densification Factor

16. SD = Sintered Density

17. GD = Green Density

18. TD = Theoretical Density

19. AD = Apparent Density

20. BHN = Brinell Hardness Number

21. HRB = Hardness Rockwell B-Scale

National Institute of Technology, Warangal Mechanical Engineering Department

Manufacturing Engineering (2012-2014) Page 1

CHAPTER-1 INTRODUCTION

1. INTRODUCTION:-

Composite materials are important engineering materials due to their outstanding

mechanical properties. Composites are materials in which the desirable properties of separate

materials are combined by mechanically or metallurgical binding them together. Each of the

components retains its structure and characteristic, but the composite generally possesses

better properties. Composite materials offer superior properties to conventional alloys for

various applications as they have high stiffness, strength and wear resistance. The

development of these materials started with the production of continuous-fiber-reinforced

composites. The high cost and difficulty of processing these composites restricted their

application and led to the development of discontinuously reinforced composites.

This study assesses the MMC technology base, detailing production capabilities, process

and product technology developments, the current marketplace, and future potential markets

and applications. Facilitators and barriers affecting the MMC sector are outlined, and

roadmaps of actions designed to enhance MMC development activities. Aluminium-silicon

alloys and aluminium-based metal matrix composites have found application in the

manufacture of various structural applications; automotive engine components such as

cylinder blocks, pistons and piston insert rings where adhesive wear (or dry sliding wear) is a

predominant process. Materials possessing high wear resistance (under dry sliding conditions)

are associated with a stable tribolayer on the wearing surface and the formation of fine

equiaxed wear debris. For adhesive wear, the influence of applied load, sliding speed, wearing

surface hardness, reinforcement fracture toughness and morphology are critical parameters in

relation to the wear regime encountered by the material. In this study contemporary wear

theories, issues related to counter face wear, and wear mechanisms are discussed. Figure 1

shows the MMCs scope in various sectors.

Figure 1: MMCs sector study scope



1.1 Metal Matrix Composites (MMCs):-

Metal matrix composites (MMCs), like all composites; consist of at least two chemically

& physically distinct phases, suitably distributed to provide properties not obtainable with

either of the individual phases. Generally, there are two phases, e.g., a fibrous or particulate

phase, distributed in a metallic matrix. The composite generally has superior characteristics

than those of each of the individual components. Usually the reinforcing component is

distributed in the continuous or matrix component. When the matrix is a metal, the composite

is termed a metal-matrix composite (MMC). In MMCs, the reinforcement usually takes the

form of particles, whiskers, short fibers, or continuous fibers.

Metal Matrix Composites (MMCs) have emerged as a class of material capable of

advanced structural, aerospace, automotive, electronic, thermal management and wear

applications. The MMCs have many advantages over monolithic metals including a higher

specific modulus, higher specific strength, better properties at elevated temperatures, lower

coefficients of thermal expansion and better wear resistance. However, on the debit side, their

toughness is inferior to monolithic metals and they are more expensive.

MMCs in general, consist of at least two components, the metal matrix and the

reinforcement. In all cases the matrix is defined as a metal, but pure metal is rarely used; it is

generally an alloy. The two most commonly used metal matrices are based on Aluminium and

Titanium. Both of these metals have comparatively low specific gravities and are available in

a variety of alloy forms. Although Magnesium is even lighter, its great affinity for oxygen

promotes atmospheric corrosion and makes it less suitable for many applications. Beryllium is

the lightest of all structural metal and has a tensile modulus higher than that of steel.

However, it suffers from extreme brittleness, which is the reason for its exclusion as one of

the potential matrix material. Nickel and Cobalt based super alloys have also been used as

matrices, but the alloying elements in these materials tend to accentuate the oxidation of fibres

at elevated temperatures.

Aluminium alloys, such as the 2000, 5000, 6000 and 7000 alloy series, are the most

commonly utilised materials in composite fabrication. Aluminium composites are widely

employed in the aerospace industry, automotive application & structural application. In the

present study we concern mainly on aluminium 6000 series (AA6061 aluminium

alloys+10%SiC) and the hybrid composites made by adding different weight % of graphite as

a reinforcement material.



1.1.1 Types of Metal Matrix Composites (MMCs):-

All metal matrix composites have a metal or a metallic alloy as the matrix. The

reinforcement can be metallic or ceramic. In some unusual cases, the composite may consist

of a metallic alloy "reinforced" by a fiber reinforced polymer matrix composite.

MMCs reinforcement can be generally divided into three major categories:-

(i) Particle reinforced MMCs

(ii) Short fiber or whisker reinforced MMCs

(iii) Continuous fiber or sheet reinforced MMCs

The particulates reinforced metal matrix composites (PMMCs) is one of the new

structural materials, and a rapid development can be seen in recent years because of excellent

properties and wide application prospects in the near future. For several years research on

fabrication methods and material property estimations for particulates reinforced metal matrix

composites has been one of the focuses in composite fields, and many excellent research

results have been obtained. Various materials have been combined with each other and give

intended properties and are different from their base materials. Such composite materials

make this concept true and reinforcement in a matrix of this material contributes enhancement

properties. But, neither matrix nor reinforcement alone but only MMC can able to fulfil the

requirement. MMCs are exciting materials which find increasing applications in aerospace,

defence, transportation, communication, power, electronics, recreation, sporting, and

numerous other commercial and consumer products. Rapid advancement in the science of the

fibres, matrix materials, processing interface structure, bonding and their characteristics on

the final properties of the composite have taken place in the recent years. Even though they

have recently used but have more tremendous effect due to their useful properties like specific

strength, specific stiffness, wear resistance, corrosion resistance and elastic modulus etc.

These composites generally contain equiaxed ceramic reinforcements with an aspect ratio

less than about 5. Ceramic reinforcements are generally oxides or carbides or borides (Al2O3

or SiCp or TiB2) and present in volume fraction less than 30% when used for structural and

wear resistance applications. In general, PAMCs are manufactured either by solid state (P/M

processing) or liquid state (stir casting, infiltration and in-situ) processes. PAMCs are less

expensive compared to CFAMCs. Mechanical properties of PAMCs are inferior compared to

whisker/short fibre/continuous fibre reinforced AMCs but far superior compared to

unreinforced aluminium alloys. These composites are isotropic in nature and can be subjected

to a variety of secondary forming operations including extrusion, rolling and forging.



The Short fibre or whisker-reinforced metal matrix composites (SFMMCs) contain

reinforcements with an aspect ratio of greater than 5, but are not continuous. Short alumina

fibre reinforced aluminium matrix composites is one of the first and most popular AMCs to

be developed and used in pistons. These were produced by squeeze infiltration process. Figure

2 show the microstructure of short fibre reinforced AMCs. Whisker reinforced composites are

produced by either by PM processing or by infiltration route. Mechanical properties of

whisker reinforced composites are superior compared to particle or short fibre reinforced

composites. However, in the recent years usage of whiskers as reinforcements in AMCs is

fading due to perceived health hazards and, hence of late commercial exploitation of whisker

reinforced composites has been very limited. Short fibre reinforced AMCs display

characteristics in between that of continuous fibre and particle reinforced AMCs.

The Continuous fibre-reinforced metal matrix composites (CFMMCs) having

reinforcements are in the form of continuous fibres (of alumina, SiCp or carbon) with a

diameter less than 20 m. The fibres can either be parallel or pre woven, braided prior to the

production of the composite as shown in Figure 2. AMCs having fibre volume fraction up to

40% are produced by squeeze infiltration technique. More recently 3MTm

Corporation has

developed 60 vol.% alumina fibre (continuous fibre) reinforced composite having a tensile

strength and elastic stiffness of 1500 MPa and 240 GPa respectively. These composites are

produced by pressure infiltration route.

Figure 2: Different Types of Metal Matrix Composites (MMCs)



1.1.2 Applications of Metal Matrix Composites (MMCs):-

Light alloy composite materials have, in automotive engineering, a high application

potential in the engine area (oscillating construction units: valve train, piston rod, piston and

piston pin; covers: cylinder head, crankshaft main bearing; engine block: part-strengthened

cylinder blocks). An example of the successful use of aluminium composite materials within

this range is the partially short-fiber reinforced aluminium alloy piston, in which the recess

range is strengthened by Al2O3 & SiCp short fibers. Comparable construction unit

characteristics are attainable only with the application of powder metallurgical aluminium

alloys or when using heavy iron pistons. The reason for the application of composite materials

is, as already described the improved high temperature properties. Potential applications are in

the area of undercarriages, e.g. transverse control arms and particle-strengthened brake disks,

which can be also applied in the area of rail mounted vehicles, e.g. for undergrounds and

railway (ICE). Some of the applications and their benefits in existing application are shown in

Figure 3 and discussed below:

I. Drive shaft for people and light load motor vehicles:

Material: - AlMg1SiCu + 20 vol. % Al2O3P

Processing: - extrusion form cast feed material

Development aims: - high dynamic stability, high Youngs modulus (95 GPa), Low

density (2.95 g cm3

), high fatigue strength (120 MPa), sufficient toughness, substitution of

steels.

II. Vented passenger car brake disk:

Material: - G-AlSi12Mg + 20 vol. % SiCP

Processing: - sand or gravity die casting

Development aims: - high wear resistance (better than conventional cast iron brake

discs), low heat conductivity, substitution of iron materials.

III. Disk brake calliper for passenger cars:

Material: - Aluminium alloy with Nextel ceramic fibre 610

Weight reduction: - 55 % compared to cast iron.

IV. Longitudinal bracing beam (Stringer) for planes:

Material: -AlCu4Mg2Zr + 15 vol. % SiCP

Processing: - extrusion and forging of casted feed material

Development aims: - high dynamic stability, high Youngs modulus (100 GPa), low

density (2.8 g cm3

), high strength, high fatigue strength (240 MPa), sufficient toughness

(19.9 MPa).



Figure 3: Applications of MMCs & Their Benefits in Existing Application



1.1.3 Necessity of Metal Matrix Composites (MMCs) .

The answer to this question can be subdivided into two parts:-

(a) Advantages with respect to unreinforced metals and

(b) Advantages with respect to other composites such as polymer matrix composites (PMCs).

a) With respect to metals, MMCs offer the following advantages:-

i. Major weight savings due to higher strength-to-weight ratio

ii. Exceptional dimensional stability (compare, for example, SiCp / Al to Al)

iii. Higher elevated temperature stability, i.e., creep resistance and

iv. Significantly improved cyclic fatigue characteristics.

b) With respect to PMCs, MMCs offer these distinct advantages:-

i. Higher strength and stiffness

ii. Higher service temperatures

iii. Higher electrical conductivity (grounding, space charging)

iv. Higher thermal conductivity

v. Better transverse properties

vi. Improved joining characteristics

vii. Radiation survivability (laser, UV, nuclear, etc.)

viii. Little or no contamination (no out-gassing or moisture absorption problems).

1.2 Aluminium and Aluminium Alloys:-

Aluminium (Al) is a silvery white and ductile member of the poor metal group of

chemical elements. Al is an abundant, light and strong metal which has found many uses.

Like all composites, aluminium-matrix composites are not a single material but a family of

materials whose stiffness, strength to weight ratio, density, and thermal and electrical

properties can be tailored. The matrix alloy, the reinforcement material, the volume and shape

of the reinforcement, the location of the reinforcement, and the fabrication method can all be

varied to achieve required properties. Aluminium is the most abundant metal in the Earth's

crust, and the third most abundant element, after oxygen and silicon. It makes up about 8% by

weight of the Earths solid surface. Due to easy availability, High strength to weight

ratio, easy machinability, durable, ductile, malleability and theoretically 100% recyclability

without any loss of its natural properties a lot of scope is there for Al MMCs.

Aluminium Alloys with a wide range of properties are used in engineering structures.

Alloy systems are classified by a number system (ANSI) or by names indicating their main



alloying constituents. Selecting the right alloy for a given application entails considerations of

its tensile strength, density, ductility, formability, workability, weld ability, and corrosion

resistance, to name a few. Aluminium alloys are used extensively in aircraft due to their high

strength-to-weight ratio. On the other hand, pure aluminium metal is much too soft for such

uses, and it does not have the high tensile strength that is needed for airplanes and helicopters.

Aluminum matrix composite (AMCs), that contain particle reinforcement have their

advantages such as isotropic distribution of the particles to be used in the engineering

applications. This distribution is generated during the fabrication processes by powder

metallurgy, compo-casting, squeeze casting, pressure-less infiltration, hot rolled extrusion etc.

Another consideration of AMCs is the influence of reinforcement particles on the corrosion

behavior. The high-strength, high-specific modulus and low-density aluminum alloy-based

composites with silicon carbide reinforcement have guaranteed significant interest in the

aerospace, defense and car industries. The combination of lightweight, environmental

resistance and useful mechanical properties such as modulus, strength, toughness and impact

resistance has made aluminium alloys well suited for use as matrix materials. Among various

reinforcements, SiCp is widely used because of its high modulus and strengths, excellent

thermal resistance, good corrosion resistance, good compatibility with matrix, low cost and

ready availability.

Table 1: Designation System for Aluminium Alloys

Alloy Designation Details (Major Alloying Element) Weight (%)

1xxx Pure Aluminium Al (99)

2xxx Cu containing alloy Cu (1.9 - 6.8)

3xxx Mn containing alloy Mn (0.3 - 1.5)

4xxx Si containing alloy Si (3.6 - 13.5)

5xxx Mg containing alloy Mg (0.5 - 5.5)

6xxx Mg and Si containing alloy Mg (0.4 - 1.5), Si (0.2 - 1.7)

7xxx Zn containing alloy Zn (1 - 8.2)

8xxx Lithium &others alloys others



Table 2: Particle Size and Purity of Raw Material

Raw Material Particle Size Purity

Aluminum -200/+325 mesh 99.50%

Silicon -325 mesh 99.57%

Magnesium -150 mesh 99.67%

Manganese -325 mesh 99.78%

Copper -325 mesh 99.81%

Iron -100 mesh 99.39%

Zinc -400 mesh 99.65%

Silicon Carbide -1200 mesh 99.00%

In the present study we are mainly concentrating on AA6061 Aluminium Alloys. The

main reason for selecting the Aluminium alloy 6061 is a medium strength alloy with excellent

Wear resistance & corrosion resistance. It has the highest strength of the 6000 series alloys.

Alloy 6061is known as a structural alloy. In plate form, 6061 is the alloy most commonly

used for machining. As a relatively new alloy, the higher strength of 6061 has seen it replace

6061 in many applications. The addition of a large amount of manganese controls the grain

structure which in turn results in a stronger alloy. It is difficult to produce thin walled,

complicated extrusion shapes in alloy 6061. The extruded surface finish is not as smooth as

other similar strength alloys in the 6000 series. 6061 is typically used in highly stressed

applications, Trusses, Bridges, cranes, Transport applications, Ore skips, Beer barrels & Milk

churns.

1.2.1 Chemical Composition of AA6061 Aluminium Alloys:-

Chemical composition of AA6061 Alloy is shown in Table 3.

Table 3: Chemical Composition of AA6061Aluminium Alloys

Element Mn Fe Mg Si Cu Zn Ti Cr Al

Weight (%) 0.4-1.0 0-0.5 0.6-1.2 0.7-1.3 0.1 0-0.2 0-0.1 0-0.25 Balance



1.3 Reinforcements:-

Reinforcement materials for metal matrix composites can be produced in the form of

continuous fibers, short fibers, whiskers, or particles. The parameter that allows us to

distinguish between these different forms of reinforcements is called the aspect ratio. Aspect

ratio is nothing but the ratio of length to diameter (or thickness) of the fiber, particle, or

whisker. Thus, continuous fibers have an aspect ratio approaching infinity while perfectly

equiaxed particles have an aspect ratio of around one.

Table 4 lists some important reinforcement materials available in different forms. Ceramic

reinforcements combine high strength and elastic modulus with high temperature capability.

Continuous ceramic fibers are also, however, more expensive than ceramic particulate

reinforcements. One can transform practically any material (polymers, metals, or ceramics)

into fibrous form. A fiber can be defined as an elongated material having a more or less

uniform diameter or thickness of less than 250 m and an aspect ratio of more than 100. Note

that this is not only an operational definition but also a purely geometrical one that applies to

any material. The long length of fibers also makes it imperative, in most cases, to incorporate

them in some continuous medium, i.e., the matrix, to hold them together to make a fiber

reinforced composite. It should be emphasized that this, by no means, is the sole purpose of

the matrix in a composite.

Table 4: Some Important Reinforcements for Metal Matrix Composites (MMCs)

Continuous Fibers A12O3, A12O3+SiO2, B, C, SiC, Si3N4,Nb-Ti, Nb3Sn

Discontinuous Fibers

a) Whiskers

b) Short fibers

SiC, Al2O3, TiB2

A12O3, SiC, (A12O3+SiO2), vapour grown carbon fibers

Particles SiCp, Al2O3, Tic, B4C, WC

1.3.1 Particulate Reinforcement:-

Silicon carbide (SiC) and (C) is composed of tetrahedral of carbon and silicon atoms

with strong bonds in the crystal lattice. This produces a very hard and strong material. SiC is

not attacked by any acids or alkalis or molten salts up to 800oC. In air, SiC forms a protective

silicon oxide coating at 1200oC and is able to be used up to 1600

oC. Silicon carbide in

particulate form has been available for a long time. It is quite cheap and commonly used for

abrasive, refractory, and chemical purposes. Particulate SiC is processed by reacting silica in



the form of sand and carbon in the form of coke at 2400C in an electric furnace. The SiC

produced in the form of large granules is subsequently commented to the desired size. Two

types of SiC particulate reinforcement are there with angular and rounded morphology,

respectively. The high thermal conductivity coupled with low thermal expansion and high

strength gives these material exceptional thermal shock resistant qualities. SiC ceramics with

little or no grain boundary impurities maintain their strength to very high temperatures,

approaching 1600oC with no strength loss. Properties of silicon carbide are low density, high

strength, low thermal expansion, high hardness, and high elastic modulus.

1.4 Production of Aluminium MMCs (Al MMCs):-

Aluminium matrix composites (AMCs) refer to the class of light weight high

performance aluminium centric material systems. The reinforcement in AMCs could be in the

form of continuous/discontinuous fibres, whisker or particulates, in volume fractions ranging

from a few percent to 70%. Properties of AMCs can be tailored to the demands of different

industrial applications by suitable combinations of matrix, reinforcement and processing

route. Presently several grades of AMCs are manufactured by different routes. Three decades

of intensive research have provided a wealth of new scientific knowledge on the intrinsic and

extrinsic effects of ceramic reinforcement on physical, mechanical, thermo-mechanical and

tribological properties of AMCs. In the last few years, AMCs have been utilised in high-tech

structural and functional applications including aerospace, defence, automotive, and thermal

management areas, as well as in sports and recreation.

The properties of the composites can be tailored by manipulating parameters such as

reinforcement particle distribution, size, volume fraction, orientation, and matrix

microstructure. Metal matrix composites (MMCs), such as SiC particle reinforced Al, are one

of the widely known composites because of their superior properties such as high strength,

hardness, stiffness, wear and corrosion resistance. SiC particle reinforced Al based MMCs are

among the most common MMC and available ones due to their economical production. They

can be widely used in the aerospace, automobiles industry such as electronic heat sinks,

automotive drive shafts, or explosion engine components, highly stressed application &

structural purpose. The physical and chemical compatibility between SiC particles and Al matrix

is the main concern in the preparation of Al/SiC/C/ composites.

Therefore, the particle reinforced metal matrix composites can be synthesized by such

methods as liquid, solid, or gaseous state processes for fabricating MMCs. Different method

results in different properties. In present study, the PM method (Solid state processing) is



carried out to prepare SiC and Gr particle reinforced Al MMC (AA6061). The effect of

weight percentage of the reinforced particles on physical & mechanical behaviour such as

density (green density and sintered density), hardness, wear resistance and microstructure

(Wear Pattern and distribution of particles along grain boundaries) of the composites can be

investigated.

1.4.1 Liquid State Processing: -

The Liquid State Processing can be subdivided into four major categories:-

a) Stir Casting: - This involves incorporation of ceramic particulate into liquid

aluminium melt and allowing the mixture to solidify. Here, the crucial thing is to

create good wetting between the particulate reinforcement and the liquid aluminium

alloy melt. The simplest and most commercially used technique is known as vortex

technique or stir-casting technique. The vortex technique involves the introduction of

pre-treated ceramic particles into the vortex of molten alloy created by the rotating

impeller. Lloyd (1999) reports that vortex-mixing technique for the preparation of

ceramic particle dispersed aluminium matrix composites was originally developed by

Surappa & Rohatgi (1981) at the Indian Institute of Science. Subsequently several

aluminium companies further refined and modified the process which are currently

employed to manufacture a variety of AMCs on commercial scale.

Microstructural inhomogeneties can cause notably particle agglomeration and

sedimentation in the melt and subsequently during solidification. Inhomogeneity in

reinforcement distribution in these cast composites could also be a problem as a result

of interaction between suspended ceramic particles and moving solid-liquid interface

during solidification. Generally it is possible to incorporate up to 30% ceramic

particles in the size range 5 to 100 m in a variety of molten aluminium alloys. The

meltceramic particle slurry may be transferred directly to a shaped mould prior to

complete solidification or it may be allowed to solidify in billet or rod shape so that it

can be reheated to the slurry form for further processing by technique such as die

casting, and investment casting. The process is not suitable for the incorporation of

sub-micron size ceramic particles or whiskers. Another variant of stir casting process

is compo-casting. Here, ceramic particles are incorporated into the alloy in the semi

solid state.



b) Infiltration Process: - Liquid aluminium alloy is injected/infiltrated into the

interstices of the porous pre-forms of continuous fibre/short fibre or whisker or

particle to produce AMCs. Depending on the nature of reinforcement and its volume

fraction perform can be infiltrated, with or without the application of pressure or

vacuum. AMC shaving reinforcement volume fraction ranging from 10 to 70% can be

produced using a variety of infiltration techniques. In order for the perform to retain its

integrity and shape, it is often necessary to use silica and alumina based mixtures as

binder. Some level of porosity and local variations in the volume fractions of the

reinforcement are often noticed in the AMCs processed by infiltration technique. The

process is widely used to produce aluminium matrix composites having

particle/whisker/short fibre/continuous fibre as reinforcement.

c) Spray Deposition: - Spray deposition techniques fall into two distinct classes,

depending whether the droplet stream is produced from a molten bath (Osprey

process) or by continuous feeding of cold metal into a zone of rapid heat injection

(thermal spray process). The spray process has been extensively explored for the

production of AMCs by injecting ceramic particle/whisker/short fibre into the spray.

AMCs produced in this way often exhibit inhomogeneous distribution of ceramic

particles. Porosity in the as sprayed state is typically about 510%. Depositions of this

type are typically consolidated to full density by subsequent processing. Spray process

also permit the production of continuous fibre reinforced aluminium matrix

composites. For this, fibres are wrapped around a mandrel with controlled 326 M K

Surappa inter fibre spacing, and the matrix metal is sprayed onto the fibres. A

composite monotype is thus formed; bulk composites are formed by hot pressing of

composite monotypes. Fibre volume fraction and distribution is controlled by

adjusting the fibre spacing and the number of fibre layers. AMCs processed by spray

deposition technique are relatively inexpensive with cost that is usually intermediate

between stir cast and PM processes.

d) In-Situ Processing (Reactive Processing): - There are several different processes that

would fall under this category including liquid-gas, liquid-solid, liquid-liquid and

mixed salt reactions. In these processes refractory reinforcement are created in the

aluminium alloy matrix. One of the examples is directional oxidation of aluminium

also known as DIMOX process.

In this process the alloy of AlMg is placed on the top of ceramic pre form in a

crucible. The entire assembly is heated to a suitable temperature in the atmosphere of



free flowing nitrogen bearing gas mixture. AlMg alloy soon after melting infiltrates

into the pre form and composite is formed. MartinMariettas exothermic dispersion

process or the XDTm process is another in-situ technique for composite processing.

XDTm process is used to produce TiB2 reinforced aluminium matrix composites. The

process is flexible and permits formation of both hard and soft phases of various sizes

and morphologies that includes whiskers, particles and platelets in aluminium alloy

matrices. Gasliquid reaction is also utilised to produce TiC reinforced aluminium

matrix composites. For example, by bubbling carbonaceous gas like methane into Al

Ti melt kept at elevated temperature it is possible to produce AlTiCp composites.

London and Scandinavian Metallurgical Company has developed an in-situ technique,

which utilises reaction between mixed salts to produce a dispersion of fine TiB2

particles in an aluminium matrix. A major limitation of in-situ technique is related to

the thermodynamic restrictions on the composition and nature of the reinforcement

phase that can form in a given system, and the kinetic restrictions on the shape, size

and volume fraction of the reinforcement that can be achieved through chemical

reactions under a given set of test conditions.

1.4.2 Solid State Processing: -

In Solid state processing Powder blending followed by consolidation (PM processing),

diffusion bonding and vapour deposition techniques comes under this section.

a) Powder Blending and Consolidation (P/M Processing): - This route is generally

preferred since its shows a number of product advantages. The uniform distribution of

ceramic particle reinforcements is readily realized. On the other hand, the solid state

process minimizes the reactions between the metal matrix and the ceramic

reinforcement, and thus enhances the bonding between reinforcement and the matrix.

The fine oxide particle tends to act as a dispersion-strengthening agent and often has

strong influence on the matrix properties particularly during heat treatment. Powder

metallurgy is a net shape forming process consisting of producing metal powder,

blending then, compacting them in dies, and sintering them to impart strength,

hardness and toughness. Although the size and the weight of its products are limited,

the PM process is capable of producing relatively complex parts economically, in net

shape form and wide variety of metal and alloy powders.



Basically, in the conventional PM production, after the metallic powders have

been produced, the sequence consists of three steps. Firstly, blending and mixing the

powder, and then compaction, in which the powders are pressed into the desired part

shape. The last step of PM method is sintering, which involves heating to a

temperature below the melting point to cause solid state bonding of the particles and

strengthening the part. Various steps involved in P/M technique is shown in Figure 4.

Blending refers to when powders of the same chemical composition but possibly

different chemistries being combine. After that, in compaction (pressing), high

pressure is applied to the powders to form them into the required shape. The pressure

required for pressing metal powders ranges from 70MPa (for Al) to 800MPa (for high

density iron parts). After pressing, the green compact lacks strength and hardness

without heat treatment. For that Sintering is done which is a heat treatment operation

performed on the compact to bond its metallic particles. Sintering is a high

temperature process used to develop the final properties of the component.

In this study, the PM method is carried out to prepare SiC and C particle

reinforced Al MMC (AA6061). Aluminium alloy 6061 is a medium strength alloy

with excellent wear & corrosion resistance. It has the highest strength of the 6000

series alloys. Alloy 6061 is known as a structural alloy. This increase in strength is

due the addition of a large quantity of manganese that controls the grain structural and

creates a strong alloy.

Figure 4: Various steps involved in synthesis of Al-SiC-C Hybrid composites by P/M

technique.



b) Diffusion Bonding: - Mono filament-reinforced AMCs are mainly produced by the

diffusion bonding (foil-fibre-foil) route or by the evaporation of relatively thick layers

of aluminium on the surface of the fibre. 6061 Al-boron fibre composites have been

produced by diffusion bonding via the foil-fibre-foil process. However, the process is

more commonly used to produce Ti based fibre reinforced composites. The process is

cumbersome and obtaining high fibre volume fraction and homogeneous fibre

distribution is difficult. The process is not suitable to produce complex shapes and

components.

c) Physical Vapour Deposition: - The process involves continuous passage of fibre

through a region of high partial pressure of the metal to be deposited, where

condensation takes place so as to produce a relatively thick coating on the fibre. The

vapour is produced by directing a high power electron beam onto the end of a solid bar

feed stock. Typical deposition rates are 510 m per minute. Composites with uniform

distribution of fibre and volume fraction as high as 80% can be produced by this

technique.

1.5 Interface: -

Interface is a very general term used in various fields of science and technology to

denote the location where two entities meet. The term in composites refers to a bounding

surface between the reinforcement and matrix across which there is a discontinuity in

chemical composition, elastic modulus, coefficient of thermal expansion, and thermodynamic

properties such as chemical potential. The interface (fiber/matrix or particle/matrix) is very

important in all kinds of composites. This is because in most composites, the interfacial area

per unit volume is very large. Also, in most metal matrix composite systems, the

reinforcement and the matrix will not be in thermodynamic equilibrium, i.e., a

thermodynamic driving force will be present for an interfacial reaction that will reduce the

energy of the system. All these items make the interface have a very important influence on

the properties of the composite. Crystallographic, Wet ability & nature of bonding manly comes

under this section.

Once the matrix and the reinforcement of a composite are chosen, it is the set of

characteristics of the interface region that determines the final properties of the composite. In

this regard, thorough characterization of the interface region assumes a great deal of

importance. A variety of sophisticated techniques are available to mechanical characterization



of the interface region. In particular, a quantitative measure of the strength of the interfacial

bond between the matrix and reinforcement is of great importances.

1.6 Basic Terminology Used in Experimental Analysis: -

a) Density: - The mass density or density of a material is its mass per unit volume. The

symbol most often used for density is . mathematically; density is defined as mass

divided by volume.

Where is the density, m is the mass, and V is the volume. In some cases (for

instance, in the United States oil and gas industry), density is also defined as

its weight per unit volume, although this quantity is more properly called specific

weight. Its unit is g/cm3.

b) Theoretical Density (TD): - Density of a pore free powder compact (practically not

attainable) is known as theoretical density and represented by th. Unit of theoretical

density is g/cm3.

c) Apparent Density (AD): - Density of the pallet when the powder fill with free fall

without any pressure (due to gravity).

d) Green Density (GD): - Density of the pallet produced by compaction is known as

green density.

e) Sintered Density (SD): - Density of the pallet produced by compaction after sintering

(heat treatment) is known as sintered density. The densities of the green compacts

were determined from the mass and the dimensions of the compacts, while the

densities of the sintered compacts were determined using the Archimedes principle.

f) Densification Factor (DF): - The densification factor for all sintered specimens was

defined, using the formula:

Where DF is densification factor, Sd is sintered density, Gd is green density, and Td is

theoretical density. A negative densification coefficient indicates expansion, while a

positive value represents shrinkage.

DF = (Sd Gd) / (Td Gd)



1.7 Hardness: -

Hardness is a measure of how resistant solid matter is to various kinds of permanent shape

change when a force is applied. It is also defined as the resistance to indentation or

scratching or surface abrasion.

There are two methods of hardness measurement:

i. Scratch Hardness: - Commonly measure by Mohrs test.

ii. Indentation Hardness (Abrasion): - measured by

Brinell hardness number (BHN)

Rockwell hardness number (HRB, HRC, etc.)

Vickers hardness number

Knoop hardness number

1.8 Wear and Wear Mechanism: -

1.8.1 Wear: -

It is defined as a process of removal of material from one or both of two solid surfaces

in solid contact. Wear is defined as the damage to a solid surface, generally involving

the progressive loss of material, due to relative motion between two moving surfaces.

Such a process is complicated, involving time-dependent deformation, failure and

removal of materials at the counter face.

1.8.2 Types of wear: -

Following are the various types of wear processes based on the types of wearing

contacts:-

(i) Single-phase wear: In which a solid moving relative to a sliding surface causes

material to be removed from the surface. The relative motion for wear to occur may be

sliding or rolling.

(ii) Multi-phase wear: In which wear, from a solid, liquid or gas acts as a carrier for a

second phase that actually produces the wear.



1.8.3 Wear Mechanisms: -

Common types of wear mechanisms are as listed below:-

(i) Abrasive wear

(ii) Solid particle erosion

(iii) Sliding and adhesive wear

(iv) Fretting wear

(v) Corrosive wear

(vi) Impact wear

Sliding and Adhesive Wear: -

As we have mentioned various types of wear mechanism which is taking place

in different application. As per my work sliding and adhesive wear mechanism is more

prominent so that my whole emphasis over sliding and adhesive wears studies.

Sliding and adhesive wear mechanism is a type of wear generated by the

sliding of one solid surface against another. Erosion, cavitations, rolling contact,

abrasion, oxidative wear, fretting, and corrosion are separated from the class of

"sliding" wear problems even though some sliding may take place in some of these

types of wear. Apparently, sliding wear is a type of wear that is "left over" when all

other types of wear have been identified under separate conditions. Although sliding

wear and adhesive wear are not synonymous, Adhesive wear is as ambiguously

defined as sliding wear. This phenomenon denotes a wearing action in which no

specific agency can be identified as the cause of wear. Adhesive wear is said to occur

if no abrasive substances are found, amplitude of sliding is greater than that in fretting

and oxidation does not take place.



1.9 Importance of hybrid MMC:-

It has been observed that the most important advantage associated with hybrid composites is

their high strength and stiffness along with low weight, which enables the greater usage of

composites in space applications where being light and strong is given prime importance.

Hybrid metal matrix composites with proper reinforcement of different material such as a SiC

Al2O3, and Graphite. Hybrid metal matrix composites are flexible in nature associated with

their desired property. With all these importance hybrid metal matrix composites have been

replaced metals as per desired application. One major drawback linked with this composite is

its high cost which is often due to the use of expensive raw materials and not due to the

manufacturing processes.

1.9.1 Wear study on MMC:-

With continual development in fabrication technique, more MMCs have been found to be

suitable to replace some of the conventional metallic monolithic alloys such as the various

grades of Al alloys in application, where light weight and energy saving are important design

considerations. The presence of hard reinforcement phases, particulates, bers or whiskers has

endowed these composites with good tribological with (friction and wear) characteristics.

These properties along with good specic strength and modulus make them good candidate

materials for many engineering situation where sliding contact is expected. Wear is a surface

phenomenon which occurs by displacement and detachment of material because wear usually

implies a progressive loss of weight and alteration of dimensions over a period of time. All

mechanical components that undergo sliding or rolling contact are subject to some degree of

wear. Such components are bearings, gears, seals, guides, piston rings, splines, brakes and

clutches.



CHAPTER-2: LITERATURE SURVEY

2.1 Literature Survey: -

The literature survey is carried out to study powder metallurgy processes, Metal

Matrix Composite preparation and behaviour, and evaluate the density, hardness & wear

properties of AA6082+SiC composites. The various parameters such as Silicon carbide

content, applied load, sliding distance, sliding speed & effect of microstructure, etc have been

studied. The work of researchers in this respect is been considered.

Federal BDM (1993) report addresses the collection and analysis of technical, market,

and policy information related to the world-wide Metal Matrix Composite (MMC) industry

sector. The report includes information gathered from a wide variety of sources. This

assessment provides a methodology and framework for conducting similar studies in the

future and identifies opportunities to enhance the level of joint effort between the U.S. and

Canada in creating and sustaining a viable MMC marketplace. This study assesses the MMC

technology base, detailing production capabilities, process and product technology

developments, the current marketplace, and future potential markets and applications.

Facilitators and barriers affecting the MMC sector are outlined, and roadmaps of actions

designed to enhance MMC development activities and foster joint U.S./Canada activities in

this arena are provided.

Liu Y.B., Lim S.C, Lu.L, And Lai M.O. (1994) have address about the advantages

to fabricate the metal matrix particulate composite (MMPCs) using powder metallurgy. They

also discussed about the various PM related methods used in fabricating MMCs and outline

the common problem associated with these methods.

Surappa M. K. (2003) had discussed about the Aluminium matrix composites

(AMCs) refer to the class of light weight high performance aluminium centric material

systems. The reinforcement in AMCs could be in the form of continuous/discontinuous fibres,

whisker or particulates, in volume fractions ranging from a few percent to 70%. Properties of

AMCs can be tailored to the demands of different industrial applications by suitable

combinations of matrix, reinforcement and processing route. He also discuss about the

presently available several grades of AMCs & their manufacturing methods by different

routes.



Khairaldien W. M, Khalil A.A. and Bayoumi M. R. (2004) have discussed about

the extensive utilization of aluminium reinforced with silicon carbide composites in different

structural applications & motivated the need to find a cost effective technological production

method for these composites. Compression tests are carried out for compositions containing

0%, 5%, 10%, 15%, 20%, 25% and 30% silicon carbide simultaneously at sintering

temperature of 650, 700, 750, 800, 850 and 9000C. Production of a homogenous, high

strength and net shape structural components made from aluminium-silicon carbide

composites can be achieved using powder metallurgy (PM) technology.

Th. Schubertet. al. (2004) have studied light weight materials are expected to replace

sintered iron and steel parts in automobiles in order to reduce weight, increase fuel efficiency

and also reduce exhaust emission.

Schaffer G.B. (2004) has pointed under the increasing interest in light weight

materials coupled to the need for cost-effective processing have combined to create a

significant opportunity for aluminium powder metallurgy. Net shape processing of aluminium

by the classical press-and-sinter powder metallurgy technique using elemental powder blends

is a unique and important metal forming method which is cost effective in producing complex

parts very close to final dimensions.

Karl Ulrich Kainer (2006) have discussed about the basics of metal matrix composite

fabrication process, applications, future scope and latest development in metal matrix

composite.

Gokce A. and Findik F. (2008) had compared the physical and mechanical

properties for argon atomized Al-1wt-%Mg powders with and without lubricant 1wt%

Acrawax. Pure nitrogen sintering was performed and the effect of sintering atmosphere for the

mixed Al-1%Mg powder compacts was also investigated.

Manoj Singla, Deepak Dwivedi D., Lakhvir Singh and Vikas Chawla (2009) have

made a modest attempt to develop aluminium based silicon carbide particulate MMCs with an

objective to develop a conventional low cost method of producing MMCs and to obtain

homogenous dispersion of ceramic material. To achieve these objectives two step-mixing

method of stir casting technique has been adopted and subsequent property analysis has been

made. Aluminium and SiC has been chosen as matrix and reinforcement material

respectively.

Padmavathi C., Agarwal D. and Upadhyaya A. (2008) studied sintering behaviour

of aluminium alloy powders. Blended 2712 (Al-Cu-Mg-Si-Sn) and 6711 (Al-Mg-Si-Cu) alloy



powders were consolidated by microwave sintering through temperature range of 570 to 630

C for 1 hr in vacuum, nitrogen, argon and hydrogen atmospheres. The influence of sintering

temperature and atmosphere on densification response were investigated in comparison with

conventional sintered parts. Microwave sintering enhanced the densification response in

shorter times and lower sintering temperature in turn leading to better properties.

Das S., R.Behera, A.Dutta, G.Majumdar, B.Oraon and G. Sutradhar (2010)

suggest that the forgability of aluminium metal matrix composite, which are produced by

powder metallurgy method, are greatly depends on the size and percentage of reinforcement

materials, compacting load, sintered temperature and soaking time etc. A comparison have

been made with different type of aluminium silicon carbide metal matrix composite materials

contains 0%, 5%, 10%, 15% & 20% by weight of silicon carbide.

A.Chennakesava Reddy and Essa Zitoun (2010) have done studies on mechanical

properties have been determined for different metal matrix composites produced from Al

6061, Al 6063 and Al 7072 matrix alloys reinforced with silicon carbide particulates.

Muller S., Schubert Th., Fiedler F., Stein R., Kieback B. and Deters L. (2011)

discussed about the mechanical and tribological behaviour of composites reinforced with

sharp edged or spherical ceramic particles. The wear resistance was evaluated during sliding

against hard steel under lubricating conditions at elevated temperatures.

Rajesh Purohit, Rana R. S. and Verma C. S. (2012) has been fabricated a

horizontal ball mill for milling of aluminium and SiC particles. The change in powder particle

morphology during mechanical alloying of Aluminium and SiC powders using horizontal ball

mill was studied. Al-SiC composites with 5 to 30 weight % of SiC were fabricated using

powder metallurgy process.

Haris Rudianto, Sangsun Yang, Yongjin Kim and Kiwoo Nam (2012) have

investigated the mechanical properties of pre-mixed aluminium matrix composites with

different chemical compositions. Mixed powers of Al-14Si-2.5Cu-0.5Mg and Al-14.5Si-

1.85Cu-2.85Fe-0.8Mg with 10% volume fraction of SiC (12 m) were used as starting

powders.

Mateusz Laska and Jan Kazior (2012) have produced using a wide range of

compaction pressures for three different chemical compositions. The compacts were then

sintered under a pure dry nitrogen atmosphere at three different temperatures. The heating and

cooling rates were the same throughout the entire test. The results showed that the green

density increases with compaction pressure, but that sintered density is independent of green

density (compaction pressure) for each sintering temperature.



Murugesan S., Balamurugan K. and Sathiya Narayanan C. (2010) have suggested

the optimization of EDM process parameter for Al 6061- 15% SiC composites with a multiple

electrode.

Siba Sankar Mahapatra and Saurav Datta (2011) have investigated to develop

redmud filled polyster composites with different weight fraction and characterize mechanical

and tribological properties. The responses have been predicted using both artificial neural

network (ANN) and Taguchi method so that a comparative evaluation can be made.

Shouvik Ghosh, Prasanta Sahoo and Goutam Sutradhar (2012) have studied the

analysis of variance is employed to investigate the influence of four controlling parameters,

viz., SiCp content, normal load, sliding speed and sliding time on dry sliding wear of the

composites. It is observed that SiCp content, sliding speed and normal load significantly

affect the dry sliding wear. The optimal combination of the four controlling parameters is also

obtained for minimum wear.

Gurcan A.B. and Baker T.N. (1995) have investigated the wear resistance of four

AA6061 MMCs together with the monolithic AA6061 alloy, all in the T6 condition, using a

pin-on-disc test.

Deuis R. L., Subramanian C. and Yellupb J. M. (1996) has reviewed

contemporary wear theories, issues related to counter face wear, and wear mechanisms are

discussed. Other areas of research relevant to adhesive wear of Al-5 alloys and aluminium

composites containing discontinuous reinforcement phases, such as the role of the

reinforcement phase, are also discussed.

Wilson S and Ball A. (2013) discussed the wear resistance of Al-MMCs and the

responses of a 6000 series aluminium alloy, reinforced with silicon carbide particles, to

cavitations erosion, solid particle erosion, abrasion and sliding wear are reported. The mode

and rate of material removal for each wear type is presented and compared to that of the

monolithic matrix alloy.

Riyadh A. Al-Samarai, Haftirman, Khairel Rafezi Ahmad and Y. Al-Douri

(2012) have discussed the effect of load and speed on sliding friction coefficient and

performance tribology of aluminiumsilicon casting alloy was evaluated using a pin-on-disc

with three different loads (10, 20, and 30 N) at three speeds (200, 300, and 400 r/min) and

relative humidity of 70%. Factors and conditions that had significant effect were identified.



D.Kondayya, S.Rajesh and Dr. A. Gopala Krishna (2010) discussed about the

study of optimal welding parameters and determined by the grey relational grade obtained

from the grey relational analysis.

2.2 Motivation for the Project: -

There are so many research is going on to meet the market requirement for

automobile, aerospace, and many engineering application to increase strength to weight ratio,

higher wear resistance property and much more that will reduce the inertia of the system and

increase performance of the system. Aluminium metal matrix composite is a relatively new

material among all the engineering materials. It has proved its position in automobile,

aerospace, and much other engineering application due to its wear resistance properties and

due to its sustainable hardness & high strength to weight ratio. The nature of distribution of

the reinforcement phase in the matrix greatly influenced the properties of aluminium metal

matrix composites. The wear of aluminium MMC which are produced by powder metallurgy

method are greatly depends upon the size and % of reinforcement materials (SiC, C) %, load,

sliding distance, sliding speed, sintering temperature and soaking time etc. so there is a lot of

scope in this aluminium based MMC. By changing the chemical composition in Al based

MMC with fixing 10% of reinforced material SiC and varying C% of powder. By using Grey

Relational Analysis we optimize the control factor according to required response variable

that will give the best result which is used for a certain application and find the most

significant control parameters which directly affect the response variable.

The increasing interest in light weight materials coupled to the need for cost-effective

processing have combined to create a significant opportunity for aluminium powder

metallurgy. Net shape processing of aluminium by the classical press-and-sinter powder

metallurgy technique using elemental powder blends is a unique and important metal forming

method which is cost effective in producing complex parts very close to final dimensions. For

cost effective production of MMCs by powder metallurgy and the high demand of these

MMCs leads to create the interest to work on that field.



2.3 Challenges and Opportunities: -

Several challenges must be overcome in order to intensify the engineering usage of

AMCs. Design, research and product development efforts and business development skills are

required to overcome these challenges. In this pursuit there is an imperative need to address

the following issues.

i. Science of primary processing of AMCs need to be understood more thoroughly,

especially factors affecting the micro structural integrity including agglomerates in

AMCs.

ii. There is need to improve the damage tolerant properties particularly fracture

toughness and ductility in AMCs.

iii. Work should be done to produce high quality and low cost reinforcements from

industrial wastes and by-products.

iv. Efforts should be made on the development of AMCs based on non-standard

aluminium alloys as matrices.

v. There is a greater need to classify different grades of AMCs based on property profile

and manufacturing cost.

vi. There is an urgent need to develop simple, economical and portable non-destructive

kits to quantify undesirable defects in AMCs.

vii. Secondary processing is an important issue in AMCs. Work must be initiated to

develop simple and affordable joining techniques for AMCs. Development of less

expensive tools for machining and cutting AMCs is of great necessity.

viii. Work must be done to develop re-cycling technology for AMCs.

ix. There must be more consortium/networking type approaches to share and document

wealth of information on AMCs.

There exist tremendous opportunities to disseminate several high profile success stories

on the engineering applications of AMCs amongst the materials community. AMCs must be

looked upon as materials for energy conservation and environmental protection. It increases

market acceptance by disseminating information on the outstanding potential of AMCs.



2.4 Objectives: -

The main purposes in accomplishing of this project are:-

I) To optimize structure and properties of AA6061/SiCp/C MMCs by varying process

parameters.

II) To synthesis Al6061+ (silicon carbide and Graphite) particle reinforced with aluminium

metal matrix composite using powder metallurgy process.

III) To study the effect of weight percentage of silicon carbide and C particles on physical

behaviour (Theoretical density & sintered density) & mechanical behaviour (Hardness, Wear

& Microstructure) of aluminium based hybrid metal matrix composite.

IV) Optimization of the experimental results using grey relation analysis & identification of

most significant control factor by ANNOVA ANALYSIS.



2.5 Problem Statement: -

Aluminium metal matrix composites (AA6061 MMCs) are attractive for a wide variety of

aerospace, transportation, structural, automobile and defence applications. But AA6061 has

lower resistance, low strength and hardness. To overcome this problem, silicon carbide (SiC)

and C (Graphite) is added as a reinforcement particle to enhance the mechanical behaviour of

Al MMC.

`

Figure 5: A flow chart of powder metallurgy method and specimen analysis

Figure 5 shows the powder metallurgy method to produce five composite specimens with

different weight percentage of SiC+C as reinforcement particles in the composites and final

analysis of produced specimen.

The experiment has been performed on different composition of C and fixed composition

of SiC. The Graphite particles which are varying (0%, 3%, 5%, and 7%) by weight

percentage. The composite has been prepared by powder metallurgy method and the

specimens were examined using the standardized test which are Density test, Rockwell

Hardness test (B-scale), Wear test & Microstructure.

In this study, four specimen of the composite are produced with different weight

percentage of C which are (0%, 3%, 5%, and 7%) to investigate the effect on mechanical

behaviour on the composites.

Raw material (Powders)

Blending

Compacting

Sintering

Final Specimen Analysis

i) Density (green & sintered)

ii) Hardness

iii) Wear Resistance

iv) Microstructure



CHAPTER- 3: EXPERIMENTAL PROCEDURES

3.1 Work Material:-

This chapter describes the experimental procedure as adopted in the present study. In

the present study, the PM method is carried out to prepare SiC particle and C reinforced Al

based Hybrid MMC (AA6061 + 10% of SiC+ varying %of C). Aluminium alloy 6061 is a

medium strength alloy with excellent corrosion resistance. Chemical composition of alloy

AA6061 is shown in Table 5. It has t

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123504-Grey Relational Analysis Approach for Optimization of Wear (2)