EFFECT OF EQUAL CHANNEL ANGULAR PRESSING ON

MICROSTRUCTURE AND MECHANICAL PROPERTIES ON NON

DENDRITIC LM25 ALUMINIUM ALLOY

This report is submitted in accordance with requirement of the University Teknikal

Malaysia Melaka (UTeM) for Bachelor Degree of Manufacturing Engineering

(Engineering Process) (Hons.)

by

NURHASYINAZ BT MOKHTAR

B051310232

940618-02-5542

FACULTY OF MANUFACTURING ENGINEERING

2017

Disahkan oleh:

_____________________________ ______________________________

Alamat Tetap: Cop Rasmi: Kg. Teluk. Mukim Binjal,_______ 06000 Jitra.___________________ Kedah._______________________

Tarikh: _______________________ Tarikh: _______________________ *Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai SULIT atau TERHAD.

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA

Tajuk: EFFECT OF EQUAL CHANNEL ANGULAR PRESSING ON MICROSTRUCTURE AND MECHANICAL PROPERTIES ON NON DENDRITIC LM25 ALUMINIUM ALLOY Sesi Pengajian: 2016/2017 Semester 2 Saya NURHASYINAZ BINTI MOKHTAR (940618-02-5542) mengaku membenarkan Laporan Projek Sarjana Muda (PSM) ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut: 1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan

untuk tujuan pengajian sahaja dengan izin penulis. 3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan

pertukaran antara institusi pengajian tinggi. 4. *Sila tandakan (√)

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysiasebagaimana yang termaktub dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/ badan di mana penyelidikan dijalankan)

SULIT

TERHAD

TIDAK TERHAD

DECLARATION

I hereby, declared this report entitled “Effect of Equal Channel Angular Pressing on

Microstructure and Mechanical Properties on Non Dendritic LM25 Aluminium Alloy” is the

results of my own research except as cited in references.

Signature :…………………………………………..

Author’s Name :NURHASYINAZ BINTI MOKHTAR

Date :22 June 2017

APPROVAL

This report is submitted to the Faculty of Manufacturing Engineering of Universiti

Teknikal Malaysia Melaka as a partial fulfillment of the requirements for the degree of

Bachelor of Manufacturing Engineering (Manufacturing Process)(Hons.). The member of the

supervisory is as follow:

…………………..........

(Dr. Mohd Shukor bin Salleh)

i

ABSTRAK

Kajian ini adalah mengenai pemprosesan logam separa pepejal aloi aluminium

LM25 menggunakan penyejukan pemutus cerun diikuti oleh saluran sama sudut menekan.

Dalam kajian eksperimen ini, parameter yang paling berpengaruh di antara suhu tuangan dan

panjang penyejukan cerun yang memberi kesan globalisasi aloi LM25 semasa penyejukan

pemutus cerun telah dikaji. Selain itu, kekerasan, kekuatan tegangan dan tingkah laku patah

penyejukan pemutus cerun dan sampel pemutus konvensional telah disiasat. Semua kerja-kerja

eksperimen telah dilakukan dengan menggunakan sama aloi aluminium LM25. Aluminium

LM25 bilet aloi bahan mentah telah disediakan melalui teknik cerun penyejukan dan pemutus

konvensional yang telah dibuang terus ke dalam acuan. Beberapa sampel kemudiannya dirawat

dengan rawatan haba T6 iaitu rawatan penyelesaian 520 ° C selama 8 jam, penyejukan dalam

air, diikuti oleh penuaan pada 154 ° C selama 4 jam. Semua sampel kemudiannya diperhatikan

dengan menggunakan mikroskop optik (OM), Mikroskop Imbasan Elektron (SEM), kekerasan

dan ujian tegangan serta sifat-sifat patah. Keputusan mendedahkan bahawa pada mencurah

suhu 650 ° C dan 400 mm penyejukan panjang cerun, aloi LM25 yang mempamerkan ciri

mikrostruktur sfera kerana semua struktur dendrit telah diubah ke dalam ɑ-Al globul dan roset.

nilai kekerasan Vicker yang digambarkan bahawa sampel ECAP diproses dipertingkatkan

kekerasan tertinggi daripada pemutus konvensional dan penyejukan pemutus cerun. Di samping

itu, ia telah diperhatikan bahawa untuk kekuatan tegangan muktamad, sampel ECAP dengan

satu laluan sahaja yang 188,98 MPa mempunyai nilai tertinggi berbanding syarat lain dan

sampel as-tuang. Dalam semua penyiasatan dan ujian mekanikal, pemutus cerun penyejukan

yang menjalani T6 rawatan haba mendedahkan hasil yang jelas yang menjadi sifat-sifat yang

paling dominan dalam pengagihan mikrostruktur, kekerasan dan tegangan hartanah, berbeza

dengansampelbukanhabadirawat

ii

ABSTRACT

This study is about the semisolid metal processing of aluminium LM25 alloy using

cooling slope casting followed by equal channel angular pressing. In this experimental

study, the most influential parameters between the pouring temperature and the length of

cooling slope that affect the globalization of LM25 alloy during cooling slope casting were

studied. Besides, the hardness, tensile strength and fracture behavior of cooling slope

casting and conventional casting samples were investigated. All the experimental works

were accomplished by using same LM25 aluminium alloy. The aluminium LM25 alloy

feedstock billets were prepared through the cooling slope technique and conventional

casting that were cast directly into mould. Several of samples were then treated with a T6

heat treatment that is solution treatment 520°C for 8 hours, quenching in water,

followed by aging at 154°C for 4 hours. All of the samples were then observed by

u s i n g optical microscopy (OM), Scanning Electron Microscope (SEM), hardness and

tensile tests as well as fracture properties. The results revealed that at pouring temperature

of 650°C and 400 mm cooling slope length, the LM25 alloy exhibits the spherical

microstructural feature due to all dendritic structures were altered into ɑ-Al globule and

rosette. The Vicker’s hardness value depicted that ECAP processed sample enhanced the

highest hardness than conventional casting and cooling slope casting. In addition, it was

observed that for ultimate tensile strength, the sample of ECAP with one pass only which is

188.98 MPa has the highest value compared to other conditions and as-cast sample. In all

investigations and mechanical testing, the cooling slope casting that underwent T6 heat

treatment revealed the obvious results which became the most dominant properties in

microstructure distribution, hardness and tensile properties, in contrast with non-heat treated

sample.

iii

DEDICATION

I am dedicating this work to my beloved parents, Mokhtar bin Malid and Sopiah bt

Md. Isa, who always support and inspire me with their boundless love in achieving a

success in everything I do.

To my supervisor, Dr. Mohd Shukor bin Salleh, family and all my friends, without

them none of my success would be possible.

iv

ACKNOWLEDGEMENT

Alhamdulillah, all praise to Allah for His Grace and Blessings. First and foremost I

would like to express my gratitude to Allah S.W.T because of His love and strength that He

has given to me to complete my final year project. I do thank for His blessings to my daily

life, good health, healthy mind and good ideas especially during 10 months of the

completion of this project.

I would like to take this opportunity to extend my deepest gratitude to my supervisor,

Dr. Mohd Shukor bin Salleh for his excellent cooperation and supervised me in spite of

being extraordinarily busy with his daily duty. Thank you for all guidance, advices,

supports and the opportunity given for me to learn and endure the experience while

working on this project. Without his guidance and persistent help, this project would not be

possible.

In addition, I would like to give this appreciation to all assistant engineers and

lecturers in Faculty of Manufacturing Engineering (FKP) and Faculty of Engineering

Technology (FTK), UTeM for their sincere assistance and knowledge sharing regarding

this project.

Last but not least, I would like to thank to my beloved parents, family and all friends

for all of their moral support, prayers and encouragement that they gave to me during this

study.

v

TABLE OF CONTENT

Abstrak Abstract

i ii

Dedication

Acknowledgement

Table of Content

List of Tables

iii

iv v vi ix

List of Figures

List of Abbreviations

List of Symbols

x

xiii

xiv

CHAPTER 1: INTRODUCTION

1

1.1 Background of study 1

1.2 Problem statement 3

1.3 Objectives 4

1.4 Scope of study 4

1.5 Chapter overview 4

CHAPTER 2: LITERATURE REVIEW

6

2.1 Alloy (Aluminium) 6

2.1.1 Aluminium alloy 6

2.2 Semisolid Metal Processing (SSM) 9

2.2.1 Semisolid casting of aluminium alloy 2.2.2 Microstructure of Semisolid casting materials

9 11

2.3 Grain refinement 13

2.3.1 Grain refinement of Aluminium LM25 13

2.4 Cooling Slope Casting (CS) 15

2.5 Parameters of Cooling Slope Technique 17

vi

2.5.1 Angle of cooling Slope 2.5.2 Pouring temperature of molten metal 2.5.3 Cooling Slope length

17 18

19

vii

2.6 Equal Channel Angular Pressing 19 2.6.2 Grain refinement by ECAP 21 2.7 Parameters of Equal channel angular pressing 21 2.7.1 Number of passes 21 2.7.2 Type of routes 24 2.8 Tensile Testing 26

CHAPTER 3: METHODOLOGY 27

3.1 Gantt Chart of the Project 27

3.2 Flowchart of the Cooling Slope Casting and ECAP 29

3.3 Selection of Process Parameter 29

3.4 Experimental Procedures 30

3.4.1 Sample preparation 30

3.4.2 Feedstock production Using Cooling Slope Casting and Conventional

Casting Process 31

3.4.3 T6 Heat Treatment 33

3.5 Microstructure Investigation 34

3.5.1 Preparation of Samples for Morphology Investigation 34

3.5.2 Image Analysis 34

3.6 Hardness Testing 35

3.7 Tensile Testing 36

3.7.1 Preparation of tensile test samples 36

CHAPTER 4: RESULT AND DISCUSSION 38

4.1 Microstructure investigation 38

4.1.1 Cooling slope casting and conventional casting 38

4.1.2 Cooling slope casting and ECAP 39

4.1.3 T6 heat treatment 40

4.1.4 Shape factor and Globule size 42

4.2 Hardness testing 46

4.3 Tensile testing 48

4.4 Fracture Testing 51

CHAPTER 5: CONCLUSION AND RECOMMENDATIONS 54

5.1 Conclusion 54

viii

5.2 Recommendations 55

5.3 Sustainability Development 55

REFERENCES 57

APPENDICES

A Gantt Chart of FYP I 60

B Gantt Chart of FYP II 61

C Graph of Tensile Result for LM25 Aluminium Alloy 62

ix

LIST OF TABLES

2.1 Alloy chemical composition data of LM25 8

2.2 Thermophysical properties of LM25 aluminium alloy 9

2.3 Solid fraction of different slope angle 18

3.1 Gantt Chart for PSM 1 28

3.2 Parameters of cooling slope process for LM25 alloy 30

3.3 Composition of LM25 alloy specimen 31

4.1 The value of Vickers Hardness in as-cast, cooling slope and ECAP 46

samples

x

LIST OF FIGURES

2.1 Typical microstructure in semisolid metal 10

2.3a

2.3b

2.3c

Low magnification,

High magnification of dendritic microstructure by conventional casting

Globular microstructure by semisolid metal casting

12

2.4 Schematic illustration of cooling slope casting 16

2.5 Microstructure of Aluminium alloy processed by cooling slope 17

2.6 Hardness value versus passes of ECAP 22

2.7 Stress-strain curves of different number of ECAP passes 23

2.8 YS and UTS against number of passes 23

2.9

Schematic diagram for four fundamental type of routes

24

3.0 Values of Vickers hardness using route BC and C 25

3.1 Yield strength against number of ECAP passes 25

3.2 Example of tensile sample 26

3.3 Flowchart of cooling slope and ECAP process 29

3.4 Band saw machine 31

3.7 Set up apparatus for cooling slope 32

3.8 ECAP split die 33

3.9 T6 Heat Treatment 33

3.10 Sample preparation for microstructure investigation 34

xi

3.11 Rockwell hardness machine 36 4.0 Microstructure of LM25 aluminium alloy (a) as-cast at 650°C and 39

(b) cooling slope casting at 650°C and 400 mm length of slope

4.1 Microstructure of (a) cooling slope casting (b) equal channel angular

pressing of LM25 aluminium alloy 39

4.2 Microstructure investigation under OM (a) non-heat treated CS casting (b) heat

treated CS casting (c) non-heat treated ECAP (d) heat treated ECAP 41

4.3 SEM micrograph of CS casting which undergo (a) heat treatment process

and (b) non-heat treatment process 42

4.4 Variation of Shape factor for three different processes sample 43

xii

4.5 Comparison in the grain size (μm) of three sample types in different processes and non heat treated in cooling slope casting 44

4.6 Comparison of Non-heat treated and T6 heat treated sample in Cooling Slope casting and ECAP process 45

4.7 Comparison between non-heat treated and T6 heat treated fo CS casting and ECAP

45

4.8 The value of Vickers Hardness for Conventional casting and Cooling slope

casting 47

4.9 Variations of Vickers Hardness value for LM25 aluminium alloy of non-heat

treated and T6 heat treated for CS and ECAP samples

5.0 Sample that performed tensile test 49

5.1 Variation of Comparison of Ultimate Tensile Strength of As-cast, non-heat

treated CS, T6 heat treated CS, non-heat treated ECAP and T6 heat treated ECAP 49

5.2 The elongation to fracture of each type of LM25 alloy sample 50

5.3 SEM image for fracture testing in as-cast sample 51

5.4 SEM image for fracture testing in non-heat treated CS sample 51

5.5 SEM image for fracture testing in heat treated CS sample 52

5.6 SEM image for fracture testing in non-heat treated ECAP sample 52

5.7 SEM image for fracture testing in T6 heat treated ECAP sample

5.8 The metal scrap that is not used at cooling slope casting area 56

xiii

LIST OF ABBREVIATIONS

CNC - Computer Numerical Method

CS - Computer Slope

ECAP - Equal Channel Angular Pressing

EDM - Electrical Discharge Machine

FKP - Fakulti Kejuruteraan Pembuatan

FTK - Fakulti Teknologi Kejuruteraan

OM - Optical Microscopy

SEM - Scanning Electrone Microscope

SSM - Semisolid Metal

xiv

LIST OF SYMBOLS

°C - Degree Celcius

μm - Micrometer

MPa - Mega Pascal

% - Percentage

1

CHAPTER 1

INTRODUCTION

In introduction of Chapter 1, it will discuss and explain briefly about the background

of conducted study. From this chapter 1, the problem statement of study, research objective,

scope of study and chapter overview will be discussed.

1.1 Background of study

Equal channel angular pressing (ECAP) is a metal forming process that is well-known

used to improve the microstructure as well as the mechanical properties. This process is one

of an interesting technique because of its simple procedure. It also gives the metals that

ultrafine grained microstructure which can lead in increasing the mechanical properties. The

materials used for equal channel angular pressing is ranging from hardened alloys, pure

metals to precipitation, intermetallic and also metal matrix composites. Back to the early age

of 1980s, the equal channel angular pressing techniques was introduced by Segal. From the

method, the materials produced will be high-strength and also gives a very high strains into

bulk using of pure iron and pure copper. The effect of using ECAP method on the mechanical

behaviour has proven increase in the strength and hardness of the material. One of the success

way to increase the strength of metals is using severe plastic deformation (SPD) technique by

accumulating very large plastic strain without changing the area of cross section in

workpiece. During the equal channel angular pressing based severe plastic deformation

process, the cross section of workpiece retain same thus it can be process repeatedly until

2

achieved the required level of deformation. When the simple shear taking place in a thin layer

equal channels crossing plane, the deformation of billet will occur. Thus, with the high strain

and more fine grains of materials the behaviour of physical along with mechanical will be

improved.

In general principle of ECAP, basically the square or round cross section of billet is

crossed through is pressed through a rigid die. Then, the flow is forced to go through an

angled channel. The factor for a successive ECAP technique is that using the same outer

dimensions of billet in order to press for several times so that a high cumulative strains can be

achieved. Recently, this method is widely used and is well established. ECAP method is

utilized to enhance the characterization of metallic materials. The ultra-fine grained structure

of ECAP process have make them the most applied technique to obtain the high

performances level of some materials. In this regard, aluminium and its alloy are commonly

used in various application in industry such as in automotive and aircraft. Besides that,

aluminium alloy is also a light weight material. Over the last two decades Abd El Aal &

Sadawy (2015), materials with nanostructured and sub-microstructure have shown that an

improvement in their mechanical properties affected by ECAP method.

In order to produce products that having similarly or near net-shaped products,

specifically in automotive applications, semisolid metal (SSM) processing is the most

effective method for that reason. Semisolid metal process is chosen because of its advantages

over the conventional casting. Back to the few years before, the development of new alloys

and modified commercial alloys have turn to broad enthusiastically. Nowadays, this method

is used widely in manufacturing technology as an important role for producing engineering

stuffs. Semisolid processing is said to be capable in long-life die due to the reduced thermal

shock as well as reduce the macrosegregation.

Among all of the methods to produce semi-solid slurries including mechanical

vibration, mechanical stirring, new rheocasting process (NRP), twin screw reo-molding

process, narrow melt stream (NMS) and strain induced melt activation (SIMA), cooling slope

casting is the most preferable method. Cooling slope casting is one of the technique that is

3

simple and yet cost effective manner. In addition, a non-dendritic and globular microstructure

can be obtained through this cooling slope technique when it is heated at the range of semi-

solid.

Therefore, this present study is to analyse the microstructure on non-dendritic LM25

aluminium alloy by doing experimental test using cooling slope process and equal channel

angular pressing respectively. Thus, this study will be followed up by examined the effect of

ECAP on microstructure and mechanical behaviour of the alloy.

1.2 Problem Statement

According to the past study by Abd El Aal & Sadawy (2015) to produce the ultra-fine

grained (UFG) bulk pure aluminium it has be in increasing the number of passes by equal

channel angular pressing (ECAP) method. Based on his study, the sample are said to have

high misorientation angle, high mechanical properties and resistance to corrosion. While, in

the previous study Darban et al. (2016), the effect of equal channel angular pressing of Al-

7075 alloy on the fracture toughness is experimentally investigated by processing the ECAP

technique up to four passes but with the different routes used. Furthermore, the yield strength,

ultimate strength and microhardness depicted an improvement after four passes of ECAP.

Besides, the average grain size shown in transmission electron microscope (TEM) is

obviously refined from 40μm to less than about 500nm. There is less research that has been

carried out using this technique thus lack of information regarding the parameters that affect

the morphology of the sample and also the mechanical properties. This approach may give a

refine microstructure compared to other routes due to the high plastic strain rate undergone

by the specimen. It is important to know the effect of the process on the morphology and

mechanical properties. Regarding to this shortage, this project is conducted to visualize both

of microstructure and mechanical characteristics after the ECAP process. In addition, the

LM25 aluminium alloy was cast earlier by cooling slope method to produce a non-dendritic

microstructural specimen.

1.3 Research Objectives

4

Based on the stated problem above, this present study is conducted to achieve the

following objectives:

1. To produce the feedstock or billet by using cooling slope technique.

2. To investigate the microstructure behaviour of aluminium alloy after cooling slope

combined with equal channel angular pressing (ECAP).

3. To investigate the mechanical properties of LM25 aluminium alloy after ECAP

method.

1.4 Scope

This study is practically conducted to investigate on the microstructural properties and

also the mechanical behaviour of the ECAPed specimen. The ECAPed specimen is then

examined using Vickers hardness tester. In this work, the aluminium LM25 alloy is chosen as

the workpiece. Subsequently, the reason that affects the microstructural properties on non-

dendritic LM25 aluminium alloy will be identified.

1.5 Chapter Overview

For the overview in chapter one, it contains the background of study and also the

problem statement of project. Apart from that, the research objectives, the study scope and

chapter overview are also included. The important objectives of this study is being

highlighted earlier as to produce the feedstock or billet by using cooling slope method in

order to get the globular or non-dendritic microstructure properties. The mechanical

properties is also have to be investigated just after the equal channel angular pressing method

in order to know the improvement on the specimen properties. Next, during this study there

are only two main priotities that have being construct on the test specimen which is the

5

microstructure and mechanical properties by using equal channel angular pressing machine.

In chapter two, it explain about the literature review of project. The purpose of the review is

to assist the discussion and also the methodology of study. Lots of journals and other legal

resources is searched and being studied in detail so that the information and knowledge about

the project is accurate. The apparatus and method used within this study is consist in chapter

three. While in chapter four, the result and data obtained throughout the project has been

discussed and applied. Lastly, the overall of the study has been conclude in chapter five along

with the recommendations for the future improvement.

6

CHAPTER 2

LITERATURE REVIEW

The chapter of this literature review on effect of equal channel angular pressing on

microstructure and mechanical properties on non-dendritic LM25 aluminium alloy that is

widely used in industry of manufacturing to produce smaller grain size of material.

Furthermore, this chapter will begin on the semisolid metal processing review of aluminium

alloy. Apart from that, the LM25 aluminium alloy that is preferred to use in this study is also

assisted in this chapter.

2.1 Alloy (Aluminium)

2.1.1 LM25 Aluminium Alloy

Aluminium-Magnesium-Silicon alloy or LM25 aluminium alloy is one of the

aluminium material that is widely used by industry especially automotive industry.

Nowadays, automotive industry has dominated the aluminium casting with two thirds of all

aluminium castings. Aluminium casting is said to grow continually at the expense of iron

castings because the uses of aluminium has become important in some industry. Despite of its

cost that is obviously expensive than ferrous castings, the requirement of its characteristics as