i

EFFECT OF MACHINING PARAMETERS AND BISMUTH ADDITION ON AL-

20%MG2SI MACHINABILITY DURING DRY TURNING

ABBAS RAZAVYKIA

A project report submitted in partial fulfilment of the

requirements for the award from the degree of

Master of Engineering (Mechanical-Advanced Manufacturing Technology)

Faculty of Mechanical Engineering

Universiti Teknologi Malaysia

JUNE 2014

iii

To my beloved family and specially my dear father, mother, brother and sisters

iv

ACKNOWLEDGEMENT

First and foremost, I would like to thank Allah Almighty for his guidance,

help and giving me the strength to complete this report. A special thank to my great

supervisor Prof. Dr. Noordin Mohd Yusof for his advice, encouragement and

continuous assistance whenever required.

I would like also to express my sincere thanks to all technical staffs at the

Production and Material Science Laboratories.

I am also forever indebted to my parents Eslamali Razavykia and Kobra

Marjani who gave me real love, pray, moral support, and all their doa.

v

ABSTRACT

The metal matrix composite has become an important material in aerospace

and automotive industry due to their mechanical properties such as light weight, wear

resistance and high strength. although metal matrix composite, are produced in net

shape, there is some need for secondary operation such as machining. The main

problem in MMC machining is high tool wear which result in extra cost. This

observation has resulted in an investigation to evaluate the effect of machining

parameters and Bismuth as modifier on machinability of Al-20%Mg2Si. The

classical experimental design was also applied to develop empirical model,

(regression model), to represent the relationship between machining parameters and

cutting forces, surface roughness and the Bi modifier.

vi

ABSTRAK

Komposit logam matrik merupakan bahan yang penting terutamanya dalam

industri aero-angkasa dan automotif. Ini kerana bahan tersebut mempunyai sifat-sifat

mekanikal seperti ringan, rintangan terhadap kehausan dan mempunyai kekuatan

yang tinggi. Walaupun komposit logam matrik dihasilkan dalam bentuk yang tepat

dan jelas, ianya masih memerlukan operasi sekunder seperti pemesinan. Namun,

masalah utama dengan komposit logam matrik ini adalah kehausan pada mata alat

yang tinggi dan secara tidak langsungnya, kos yang tinggi juga diperlukan.

Pemerhatian ini telah menderong satu pengiastan untuk menilai kesan parameter

pemesinan dan penambahan Bismuth sebagai pengubahsuai lupada kebolehmesihan

Al-20%Mg2Si. Rekabentuk ujikaji klasik juga digunakan untuk menghasilkan model

emprikal (model regresi) untuk menjelaskan hubungan antara parameter pemesinan

dengan daya pemotongan, kekasaran permukaan dan juga pengubahsuai Bi.

vii

TABLE OF CONTENT

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xii

1 INTRODUCTION 1

1.1 Background 1

1.2 Problem Statement 2

1.3 Objective 2

1.4 Scope 3

1.5 Thesis Organization 3

2 LITERATURE REVIEW 5

2.1 The Aluminium Industry Today 5

2.1.1Recycled or Secondary Aluminium 6

2.1.2Important Physical Properties 7

2.1.3Crystal Structure 7

2.1.4Density 8

2.2 Metal Matrix Composites

2.3 Magnesium

9

11

2.4 Bismuth and Its Properties 13

viii

2.5 Silicon 13

2.6 Al-Mg2Si 14

2.6.1The Effect of Adding Bismuth on

Al-20%Mg2Si

15

2.7 Machining 17

2.7.1 Mechanics of Cutting 20

2.7.2 Types of Chips Produced in Metal Cutting 23

2.7.2.1 Continuous Chips 23

2.7.2.2 Built-up Edge Chips 23

2.7.2.3 Serrated Chips 24

2.7.2.4 Discontinuous Chips 24

2.8 The Forces During Turning 25

2.8.1 Cutting Force 26

2.8.2 Thrust Force 26

2.9 Temperatures in Cutting 27

2.10 Surface Finish and Integrity 28

2.11 Machinability 28

2.11.1 Machinability of Nonferrous Metals 29

2.11.2 Machinability of Miscellaneous Materials 30

2.12 Cutting Tool 31

2.12.1 High-Speed Steels 33

2.12.2 Cast-Cobalt Alloys 33

2.12.3 Carbides 34

2.12.3.1 Tungsten Carbide 34

2.12.3.2 Titanium Carbide 35

2.12.3.3 Inserts 35

2.12.4 Coated Tools 36

2.12.5 Alumina-Based Ceramics 37

2.12.6 Cubic Boron Nitride 38

2.12.7 Silicon Nitride Based Ceramics 39

2.12.8 Diamond 39

2.12.9 Whisker Reinforced Materials and Nano-

materials

40

ix

2.14 Surface Integrity 41

2.15 Surface Roughness 42

2.15.1 Arithmetic Parameters 42

2.16 Previous Research 44

3 RESEARCH METHODOLOGY 49

3.1 Introduction 49

3.2 Research Design Variables 50

3.2.1 Response Parameters 50

3.3 Cutting Condition 50

3.4 Work-piece Material 51

3.5 Preliminary Machining 51

3.6 Tool Material 51

3.7Cutting Forces Measurements 52

3.8 Surface Roughness Measurement 52

3.9 Machines and Equipment 53

3.10 Experimental Set Up 54

4 EXPERIMENTAL RESULTS AND DISCUSSION 56

4.1 Introduction 56

4.2 Effect of Cutting Condition on Cutting Force 57

4.2.1 Effect of Feed Rate on Cutting Force 58

4.2.2 Effect of Cutting Speed on Cutting Force 60

4.2.3 Effect of Modifier on Cutting Force 60

4.3 Effect of Cutting Condition on Surface Roughness 64

4.3.1 Effect of Cutting Speed on Surface Roughness 65

4.3.2 Effect of Feed Rate on Surface Roughness 67

4.3.3 Effect of Modifier on Surface Roughness 68

4.4 Classical DOE Method Data Analysis 70

4.4.1 Experiment Design 71

4.4.2 Data Analysis for Cutting Force 72

4.4.2.1 Box-Cox Plot 76

4.4.2.2 Contour Plot 77

x

4.4.2.3 3D Surface 78

4.4.3 Data Analysis for Surface Roughness 80

4.4.3.1 Box-Cox Plot 83

4.4.3.2 Contour Plot 84

4.4.3.3 3D Surface 85

4.5 Confirmation Test 86

5 CONCLUSION AND RECOMMENDATION FOR

FURTHER STUDIES

87

5.1 Conclusion 87

5.2 Recommendation 88

REFERENCES 90-92

xi

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Factors influencing machining operation 21

3.1 Cutting conditions 51

4.1 Experimental results of cutting force (Al-20%Mg2Si) 57

4.2 Experimental results of cutting force (Al-20%Mg2Si-

0.6wt.%Bi)

58

4.3 Experimental results for surface roughness (Al-20%Mg2Si) 64

4.4 Experimental results for surface roughness (Al-20%Mg2Si-

0.6wt.%Bi)

65

4.5 Average of surface roughness for non-modified work-piece

V= 210 m/min, f= 0.2 mm/rev and D=0.5 mm

67

4.6 Average of surface roughness for modified work-piece V=

210 m/min, f= 0.2 mm/rev and D=0.5 mm

68

4.7 Design summary 73

4.8 Analysis of variance table [Partial sum of squares - Type III 74

4.9 Post ANOVA table 75

4.10 Analysis of variance table [Partial sum of squares - Type

III]

81

4.11 Post ANOVA table 82

4.12 Confirmation experiments 86

xii

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Atomic structure of aluminium 8

2.2 Volume per unit weight 9

2.3 Classification of composite materials with metal matrixes 10

2.4 Schematic presentation of three shapes of metal matrix

composite materials

11

2.5 Cooling curves of Al–Mg2Si respective with the

morphology changes at different concentrations of Bi

refiner; 0.2, 0.4, 0.6, 0.8 and 1.0 wt.%.

16

2.6 (a) Depression in TN and TG corresponding to different

Bi addition and (b) characteristic particles of primary

Mg2Si as a function of Bi content

17

2.7 Some examples of common machining operations 18

2.8 Schematic illustration of the turning operation, showing

various features

19

2.9 Schematic illustration of a two-dimensional cutting

process, also called orthogonal cutting

20

2.10 Force components in three dimensional oblique cutting 27

2.11 The hardness of various cutting-tool materials depend on

the temperature

32

2.12 Methods of mounting inserts on tool holders 36

2.13 Relative time required to machine with various cutting-

tool materials, indicating the year the tool materials were

first introduced.

37

2.14 Mean line system and definition of Ra 43

2.15 Definition of the Rt, Rp and Rv amplitude parameters 44

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3.1 Summary of the methodology used in the study 50

3.2 Mitutoyo surface tester SJ-301 53

3.3 ALPHA 1350S 2-axis CNC Lathe 53

3.4 Scanning Electron Microscopy 54

4.1 Cutting force and feed rate relationship when turning non-

modified (Al-20%Mg2Si)

59

4.2 Cutting force and feed rate relationship when turning

modified specimen (Al-20%Mg2Si-0.6wt.%Bi)

59

4.3 SEM picture of microstructure of non-modified work-

piece with 500X magnification

61

4.4 SEM picture of microstructure of modified work-piece

with 500X magnification

61

4.5 SEM picture of machining surface of work-piece (left

non-modified, right modified) with 200X magnification

62

4.6 The relationship of cutting force and modifier when

turning work-piece at cutting speed 70 m/min

62

4.7 The relationship of cutting force and modifier when

turning work-piece at cutting speed 140 m/min

63

4.8 The relationship of cutting force and modifier when

turning work-piece at cutting speed 210 m/min

63

4.9 Surface roughness and feed rate relationship when turning

Al-20%Mg2Si

66

4.10 Surface roughness and feed rate relationship when turning

Al-20%Mg2Si-0.6wt.%Bi

66

4.11 Surface roughness graph and machining surface for non-

modified work-piece (with 50X magnification), V= 210

m/min, f= 0.2 mm/rev and D=0.5 mm

67

4.12 Surface roughness graph and machining surface for

modified work-piece (with 50X magnification), V= 210

m/min, f= 0.2 mm/rev and D=0.5 mm

68

4.13 Surface roughness and feed rate relationship when turning

with cutting speed 70 m/min

69

4.14 Surface roughness and feed rate relationship when turning

xiv

with cutting speed 140 m/min 69

4.15 Surface roughness and feed rate relationship when turning

with cutting speed 210 m/min

70

4.16 BUE formation in both specimens, left side non-modified

and right side modified work-piece at V= 210 m/min, f=

0.2 and D= 0.5

70

4.17 Multilevel categoric design 71

4.18 Design layout screen 72

4.19 Half-normal plot of effects for cutting force 73

4.20 Normal plot of residuals 76

4.21 Box-Cox plot 77

4.22 Contour plot for non-modified 78

4.23 Contour plot for modified 78

4.24 3D Surface plot for non-modified 79

4.25 3D Surface plot for modified 79

4.26 Half-Normal plot of effects for cutting force 80

4.27 Normal plot of residuals 83

4.28 Box-Cox plot 83

4.29 Contour plot for non-modified 84

4.30 Contour plot for modified 84

4.31 3D Surface plot for non-modified 85

4.32 3D Surface plot for modified 85

1

CHAPTER 1

INTRODUCTION

1.1 Background

MMCs are compounded of a moderately soft and ductile metal base material,

or ‘‘matrix’’ reinforced with a hard and brittle reinforcement material. The

reinforcement are divided to three groups, particles, whiskers, or fibers. The first

advantages provided by these materials are their enhanced mechanical properties,

especially in the aspects of wear, strength and stiffness. These matrix materials

contributes to the properties of high specific stiffness and strength. In the form of

particle is most typically shape for reinforcement. Fiber reinforcement is not so

common and is barred to situations where performance is the important factor rather

than cost. The amount of reinforcement in MMCs is often less than 40%.

The perfect properties are experienced with Mg2Si, and as result have high

potential as structural material. It attracts engineers attention in the automotive

industry to produce items such as cylinder blocks and cylinder heads. The low

density of Mg2Si brings about weight reduction and reduce cost as result of Al, Mg

and Si as starting materials, provide excellent advantages. Attributed to the

intermetallic compound Mg2Si offers some advantages such as high melting

temperature, low density, high hardness, low thermal expansion coefficient and high

elastic modulus.

2

The cast composites which are produced by conventional casting tends to

form undesirable coarse primary Mg2Si particulates, which have considerable effect

on the mechanical properties because of the large and brittle nature of Mg2Si

particles and enhancement in the mechanical properties may be obtained by fast

solidification during casting and mechanical alloying which result in the production

of composite with very fine matrix structure and in situ Mg2Si particles(Nordin,

Farahany et al. 2013).

Although the MMCs are produced to net shape by using appropriate

techniques, there is still the need for some operation such as secondary machining.

The high tool wear due to the abrasive action of reinforcement particles is the most

important consideration during MMCs machining(El-Gallab and Sklad 1998).

1.2 problem Statement

There are many factors including cutting speed and feed rate which

influenced the machining of AL-Mg2Si. However the following reasons provide the

motivation for performing this work.

• Unavailability of information of machining and machinability of Al-Mg2Si.

• To make available empirical models to predict the final surface roughness

and cutting force when turning Al-Mg2Si (Non-modified) and Bismuth modified Al-

Mg2Si in specific cutting speed and feed rate.

1.3 Objective

The objective of this study are as follow:

3

To evaluate the effect of machining parameters (Cutting speed and Feed rate)

on surface roughness and cutting forces when turning non-modified and

modified Al-20%Mg2Si.

To develop empirical model, to represent the relationship between machining

parameters and surface roughness and cutting forces.

1.4 Scope

The scope of this work are as follow:

Work-piece materials which will be used in this investigation are, Al-

20% Mg2Si (non-modified) and Al-20% Mg2SiBi modified (0.6wt.%Bi).

The experiments will be conducted on an ALPHA 1350S 2-Axis CNC Lathe

turning machine and PVD coated ceramic cutting tool will be used.

The surface roughness and cutting force (Fc) during the dry turning are the

machinability parameters that will be evaluated in terms of determine

machinability.

Statistical Design of Experiment will be implemented in this study.

The surface morphology and integrity will be analyzed by using Scanning

Electron Microscope (SEM).

1.5 Thesis Organization

Chapter one, covers an introduction and overview of metal matrix composites

and their properties. This chapter also discusses background of the study, statement

of problem, determining the objective and scope of the study.

4

Chapter two includes the review of literature consisting of basic definitions

regarding composites, machining and related concepts. And finally all information

about machinability, cutting tools, cutting forces and related equipment.

chapter three puts forward research framework and methodology, which

provides guidelines on how this research will be conducted in order to reach its

objective.

In chapter four, the appropriate model and experiment variables based on

objective and study condition are selected. And all data are compared to evaluate the

concerned material and its machinability.

In chapter five, the result of the study is provided and findings are discussed.

In order to investigate the effect of machining parameters on Al-20%Mg2Si

machinability and develop empirical model to represent the relationship between

cutting speed, feed rate, cutting force and surface roughness.

90

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