vii
TABLE OF CONTENTS
CHAPTER
1
2
TITLE
PAGE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
xii
LIST OF FIGURES
xiv
LIST OF ABBREVIATIONS
xix
LIST OF SYMBOLS
xxi
LIST OF APPENDICES
xxii
INTRODUCTION
1
1.1
Background of the Research
1
1.2
Problem Statements
4
1.3
Objectives of the Research
5
1.4
Scope of the Research
5
1.5
Significance of the Research
6
1.6
Thesis Organisation
7
LITERATURE REVIEW
9
2.1
Introduction
9
2.2
Background of Biomaterials
9
2.3
Implant Biomaterials and its Applications
10
2.4
Major Issues on Implant Materials
15
viii
2.4.1
Mechanical Properties Requirement of
Implant Materials
16
2.4.2
Corrosion Properties of Implant Materials
20
2.4.3
Biocompatibility of Implant Materials
21
2.5
Issues and Challenges of Biodegradable Implants
23
2.6
Brief Overview of Zinc Metal
26
2.7
Brief Review on Development of Zn-Mg Alloy
28
2.8
Heat Treatment of Zinc and Zinc Based Alloys
32
2.9
Severe Plastic Deformation (SPD)
37
2.9.1
Principle of Equal Channel Angular
Pressing Technique
39
2.9.2
Shear Strain in ECAP Processing
41
2.9.3
Effect of ECAP Parameters on Material
Properties
2.9.4
Critical Review on Zn-Based Alloys
Processed Through ECAP Technique
2.10
3
44
Summary
46
47
METHODOLOGY
49
3.1
Introduction
49
3.2
Research Approach
49
3.2.1
Development of Sample
53
3.2.2
Permanent Mould Design and Fabrication
54
3.3
Preliminary Experiments
55
3.3.1
Thermal Analysis
55
3.3.2
Sample Preparations
56
3.3.2.1 Cutting of Sample Material
57
3.3.2.2 Sample Material Mounting
58
3.3.2.3 Grinding Process
58
3.3.2.4 Polishing Process
59
3.3.2.5 Samples Cleaning Process
60
3.3.2.6 Wet Chemical Etching Process
61
3.3.3
Heat Treatment Performed on Cast Zn3Mg Alloy
62
ix
3.4
Final Stage Experiments
63
3.4.1
Selection of ECAP Die Material
63
3.4.2
ECAP Die Design and Fabrication
64
3.4.3
Processing of Zn-3Mg Alloy Using ECAP
Die
3.5
66
Material Characterizations
68
3.5.1
Microstructure Analysis
68
3.5.2
Mechanical Properties
69
3.5.2.1 Hardness Measurement
69
3.5.2.2 Tensile Test Measurements
70
3.5.2.3 Compressive Test
71
Degradation Experiments
72
3.5.3.1 Electrochemical Technique
72
3.5.3.2 Weight Loss Technique
74
3.5.3
3.5.3.3 Measurement of Metal Ions
Release
3.5.4
75
Biocompatibility Assessment of
Developed Zn-3Mg Alloy
76
3.5.4.1 Extraction Preparation
76
3.5.4.2 Cell Viability Assay
77
3.5.4.3 Alkaline Phosphatase (ALP)
Extracellular Enzyme Activity
Assay
4
77
RESULTS AND DISCUSSION
79
4.1
Introduction
79
4.2
Preliminary Results -Microstructure Analysis of
Cast Zn-3Mg Alloy
4.3
Preliminary Results - Thermal Analysis of Zn-3Mg
Alloy
4.4
79
82
Preliminary Results - Heat Treatment Analysis of
Zn-3Mg Alloy
4.4.1
85
Influence of Cooling Mediums on
Microstructures of Zn-3Mg alloy
86
x
4.4.2
Influence of Cooling Mediums on
Degradation Behaviour
4.4.3
Influence of Water Cooling Medium on
Mechanical Properties
4.4.4
90
97
Influence of Water Cooling Medium on
Degradation Properties
102
4.4.4.1 Corrosion Analysis Using
Weight Loss Method
102
4.4.4.2 Corrosion Analysis Using PDP
Method
108
4.4.4.3 Corrosion Analysis Using EIS
Method
4.5
112
Final Stage Experimental Results and Discussion
115
4.5.1
Analysis of ECAP Die Performance
116
4.5.2
ECAPed Samples Microstructure and
Grain Size Analysis
4.5.3
118
Analysis of Mechanical Properties of
ECAPed Zn-3Mg Samples
123
4.5.3.1 Microhardness Analysis of
4.5.4
ECAPed Samples
123
4.5.3.2 Tensile strength Analysis
125
Analysis of Degradation Bahaviour of
ECAPed Zn-3Mg Samples
132
4.5.4.1 Corrosion Analysis Using
Weight Loss Method
132
4.5.4.2 Corrosion Analysis Using PDP
Methods
137
4.5.4.3 Corrosion Analysis Using EIS
Method
4.6
Biocompatibility Analysis on ECAPed Zn-3Mg
Samples
4.7
140
142
4.6.1
Cell Viability Analysis Using MTS Assay
143
4.6.2
Analysis of ALP Enzymes Activity Assay
144
Summary of the Findings
146
xi
5
CONCLUSIONS AND RECOMMENDATIONS FOR
FUTURE WORK
149
5.1
Introduction
149
5.2
Conclusions
149
5.3
Recommendations for Future Work
151
REFERENCES
Appendices A - M
152
173 – 199
xii
LIST OF TABLES
TABLE NO.
2.1
TITLE
Potential applications of biomaterial in surgical field
[54].
2.2
PAGE
11
Advantages and disadvantages of different types of
implant materials [54, 59, 60]
14
2.3
Typical issues on implantation responses [64]
16
2.4
Physical-Chemical-Thermo properties of zinc [119-122]
28
2.5
Zn and Zn-based alloys as biodegradable metal
30
2.6
Summary of pathophysiology and toxicology of Zn and
Mg element[130, 131].
2.7
Previously reported heat treatment performed on Znbased alloys
2.8
35
Common processing routes during ECAP operation
[175]
2.9
30
45
Summary of researches on Zn-based alloys using various
ECAP design and processing parameters
47
3.1
Ion concentration in the Kokubo SBF [133]
73
4.1
Percentage porosity area of untreated and treated Zn3Mg samples.
4.2
Average grains size of as-cast and homogenised Zn-3Mg
samples
4.3
90
Polarization corrosion results of as cast and heat treated
Zn-3Mn samples
4.4
87
91
Average corrosion pits area of as-cast and homogenised
Zn-3Mg samples
93
xiii
4.5
Hardness value of as cast, homogenised Zn-3Mg
samples
4.6
Hardness value of as cast, homogenised Zn-3Mg alloy
and cortical bones
4.7
97
97
Compressive strength results of as-cast and homogenised
Zn-3Mg samples in comparison to human cortical bone
[131].
4.8
98
Tensile results of as cast and heat treated Zn-3Mg alloy
[205, 207]
100
4.9
Immersed Zn-3Mg sample ions released to SBF solution
103
4.10
Potentiodynamic polarization results
111
4.11
Simulated corrosion results obtained from the proposed
EIS equivalent circuit
4.12
Element compositions of ECAP die steel GDS result
compared to as-supplied.
4.13
133
Corrosion results obtained from polarization curves
analysis.
4.20
130
Zn and Mg ions released during immersion corrosion
test
4.19
129
Grain size analysis of untreated and treated Zn-3Mg
samples
4.18
127
Percentage porosity area of as cast, homogenized and
ECAPed Zn-3Mg samples
4.17
124
Mechanical properties of untreated and treated Zn-3Mg
alloy.
4.16
119
Hardness value of 1-, 2-ECAP pass, and homogenised
Zn-3Mg samples
4.15
116
Average grains size (µm) of homogenised and ECAPed
Zn-3Mg samples.
4.14
114
139
EIS simulated results of ECAPed and homogenised Zn3Mg samples
141
xiv
LIST OF FIGURES
FIGURE NO.
2.1
TITLE
PAGE
Examples of orthopaedic implants for: (a) knee, (b) plate
and screw (c) hip and elbow. Courtesy from MediTeg,
Universiti Teknologi Malaysia
2.2
Strength and ductility plots of some Zn and Mg based
alloys processed via ECAP technique [43, 79-82].
2.3
12
19
Images of (a) craniofacial plates, (b) orthopaedic screws
and (c) dentals screws.
24
2.4
Mg-Zn Equilibrium Phase Diagram[144]
32
2.5
Sectional view of ECAP die showing a channel
intersection angle Φ = 90o and the angle of outer corner
curvature Ψ = 20o [163].
2.6
40
Section through an ECAP die showing geometry of
shear of a square element abcd where Φ is the angle of
intersection of the two channels and Ψ is the angle
subtended by the curvature of the outer corner: (a) when
Ψ = 0, and (a) when Ψ has a value 0 ≤ Ψ ≤π – Φ[165].
41
3.1
Main activities under each stage of experiment.
50
3.2
Overall research methodology flow chart.
52
3.3
Induction furnace (Inductotherm, Australia).
54
3.4
Photo of fabricated mild steel mould (a) unassembled,
(b) assembled.
55
3.5
Schematic and actual thermal analysis set up.
56
3.6
Samples preparation overall flowchart.
57
3.7
Actual and schematic drawing of cast Zn-3Mg small
samples machined
58
xv
3.8
Tegramin-25
programmable
automatic
grinding/polishing machine
59
3.9
Branson 2510 ultrasonic cleaning machine.
61
3.10
Wet chemical etching process carried out undr vacuum
cupboard.
3.11
62
Homogenisation set up: (a) high temperature vacuum
tube furnace (OTP-1200X), (b) Schematic diagram of
heating cycle
63
3.12
Schematic drawing and assembled fabricated ECAP die.
65
3.13
ECAP experimental die set-up on Instron 600DX
SATEC series tensile/compressive testing machine.
67
3.14
Cross section of ECAP die setup.
67
3.15
Samples processed through 1 and 2 ECAP passes after
grinding.
3.16
DVK-2 Matsuzawa microhardness testing machine used
to measure samples hardness.
3.17
68
70
Detailed drawing of tensile test specimens dimensions
according to ASTM E8/E8M-08.
71
3.18
Image of machined Zn-3Mg samples tensile specimens.
71
3.19
Instron 600DX SATEC series tensile/compressive
testing machine used to conduct compressive and tensile
test.
72
3.20
Electrochemical corrosion cell set up.
74
3.21
Weight loss (immersion) test experimental set-up.
75
4.1
Microstructure of as-cast Zn-3Mg alloy (a) Optical
Image (b) high magnification of rectangular area X.
4.2
80
Cast Zn-3Mg alloy shows (a) enlargement of selected
rectangular area Y (b) EDS spectrum of selected
rectangular area Y.
4.3
X-ray diffraction patterns confirm the presence of
Mg2Zn11 and Zn phases on as-cast Zn-3Mg alloy.
4.4
81
82
Cooling curve and its first and second derivative curves
showing characteristic temperatures and times for the
solidification of Zn-3%Mg cast alloy.
84
xvi
4.5
Cooling curve recorded by the centre and wall
thermocouples
with
corresponding
temperature
difference curve indicating ECP.
4.6
Solid fraction of Zn-3Mg cast alloy as a function of time
during solidification stage.
4.7
84
85
Optical microstructure image of Zn-3Mg alloy (a) ascast, and after heat treatment in different mediums (b)
open air, (c) inside furnace and (d) water bath.
4.8
XRD spectrums of as-cast and homogenised Zn-3Mg
samples
4.9
90
Potentiodynamic polarization curves of as-cast and heat
treated Zn-3Mg alloy samples.
4.12
89
Microstructure of Zn-3Mg alloy (a) as-cast and (b)
homogenised
4.11
88
Zn-3Mg alloy grains size distribution (a) as cast (b)
homogenised.
4.10
87
91
FESEM images of surface corrosion morphology of Zn3Mg samples exposed to SBF solutions during
potentiodymanic polarization test (a) as-cast (b) air
quenched (c) furnace quenched (c) water quenched.
4.13
93
Optical microstructure of homogenised Zn-3Mg samples
homogenised for (a) 5 hrs, (b) 10 hrs, (c) 15 hrs, and (d)
25 hrs duration
4.14
95
Vickers microhardness plot of as cast and homogenised
for 5, 10, 15, and 25 hrs duration then followed by water
quenched Zn-3Mg alloy
4.15
Compressive strength curves of as-cast and homogenised
Zn-3Mg samples.
4.16
101
Tensile test fracture morphology of Zn-3Mg samples (a)
as cast, (b) homogenised
4.18
99
Tensile test plot of as-cast and homogenised Zn-3Mg
alloy
4.17
96
102
Changes in pH of Kakubo’s solution during immersion
test of as-cast and homogenised Zn-3Mg samples
104
xvii
4.19
SEM surface morphology of immersed Zn-3Mg samples
(a) as-cast (b) homogenised (c) high magnification of
area A in Figure 4.20(a), (c) high magnification of area
B in Figure 4.20(b)
4.20
EDS analysis of Zn-3Mg alloy corrosion products (a) ascast (b) homogenised
4.21
107
XRD pattern of as-cast and homogenised Zn-3Mg
samples immersed in SBF solution for 21 days
4.22
106
108
Potentiodynamic polarization curves of as-cast and
homogenised Zn-3Mg samples in comparison to curves
of pure Zn and pure Mg samples
4.23
110
Corrosion morphology images of (a) cast and (b)
homogenised Zn-3Mg alloy (c) pure Zn, and (d) pure
Mg
4.24
Nyquist plots of as-cast & homogenised Zn-3Mg, pure
Zn and pure Mg samples.
4.25
113
Proposed EIS equivalent circuit for simulation of
Nyquest results
4.27
112
Bode phase plots of as-cast & homogenised Zn-3Mg,
pure Zn and pure Mg samples.
4.26
110
114
Images of ECAP processed Zn-3Mg samples at
temperature range of (a) 1000C to190oC, (b) 210oC to
250oC, and (c) 200oC.
4.28
Heat distribution image captured using FLIR E60 series
infrared thermal imaging camera
4.29
120
Grain size distribution of ECAPed Zn-3Mg alloy (a)1ECAP pass (b) 2-ECAP pass
4.31
118
Optical images of Zn-3Mg microstructure after (a) 1ECAP pass, and (b) 2-ECAP pass.
4.30
117
122
Grains size mapping of ECAPed Zn-3Mg samples (a) 1ECAP pass (b) 2-ECAP pass. (Note: colours shows grain
size classification)
4.32
123
Vickers hardness value for homogenised and ECAPed
Zn-3Mg samples
124
xviii
4.33
Hardness indentation imprints of Zn-3Mg samples (a)
homogenised, (b) 1-ECAP pass (c) 2-ECAP passes.
4.34
Tensile test plots of untreated and treated Zn-3Mg
samples.
4.35
127
Tensile test fracture morphology of Zn-3Mg samples (a)
1-ECAP pass (b) 2-ECAP passes.
4.36
125
132
Corrosion morphology of ECAPed Zn-3Mg samples (a)
1-ECAP pass (b) magnified rectangular area in Figure
4.37(a), (c) 2-ECAP pass (d) magnified rectangular area
in Figure 4.37(b).
4.37
EDS analysis of surface corrosion products on
rectangular areas of Figure 4.36(a & b).
4.38
137
Potentiodynamic polarization curves of homogenised, 1and 2-ECAP pass Zn-3Mg samples.
4.40
136
XRD spectrums of 1-, and 2-ECAP pass Zn-3Mg
samples
4.39
135
138
Zn-3Mg samples corrosion morphology (a) 1-ECAP
pass (b) Magnified rectangular area in Figure 4.40(a), (c)
2-ECAP pass. (d) Magnified rectangular area in Figure
4.40(c)
4.41
Nyquist plots of homogenised, 1-ECAP pass, and 2ECAP pass Zn-3Mg samples
4.42
140
142
Cell viability of NHOst cells after 1, 3 and 7 days. Note:
1 = 0.1 mg/ml, 2 = 0.5 mg/ml, 3 = 1.0 mg/ml and 4 = 2.0
mg/ml. Note: *** p<0.005.
4.43
144
ALP enzyme concentration of all groups. Note: 1 = 0.1
mg/ml, 2 = 0.5 mg/ml, 3 = 1.0 mg/ml and 4 = 2.0 mg/ml.
Note: *** p=0.005.
4.44
145
Developed methodology for improving the mechanical
and degradation properties of Zn-3Mg alloy and research
novelty obtained.
147
xix
LIST OF ABBREVIATIONS
DNA
-
Deoxyribunuclei Acid
ROS
-
Reactive Oxygen Species
SPD
-
Severe Plastic Deformation
NHOst
-
Normal Human Osteoblast cell
OM
-
Optical Microscope
FESEM
-
Field Emission Scanning Electron Microscope
EDX
-
Energy Dispersive Electron Microscope
XRD
-
X-Ray Diffraction
MTS
-
Methylthiozol Tetrazolium Salt
ALP
-
Alkaline Phosphatase
SBF
-
Simulated Body Fluid
PTFE
-
Polymer-ply-tetra-fluorethylene
PMMA
-
Polymethyl-metheacralyte
HA
-
Hydroxyapatite
ECAP
-
Equal channels angular pressing
HCP
-
Hexagonal Closed-Packed
B.C
-
Before Christ
R.E
-
Rare Earth
HPT
-
High Pressure Torsional
SSMR
-
Super-Short Multi pass Rolling
RCS
-
Repetitive Corrugated and Straightening
CEC
-
Cyclic Extrusion Compression
DCCAP
-
Double Channel Angular Pressing
MDF
-
Multi-Directional Forging
F.C.C
-
Face Centered Cubic
B.C.C.
-
Body Centered Cubic
A.A.S
-
Atomic Absorption Spectrum
xx
EDM
-
Electric Discharge Machining
CNC
-
Computer Numerical Control
ASTM
-
American Society for Testing and Materials
PDP
-
Potentiodynamic Polarization
EIS
-
Electrochemical Impedance Spectroscopy
SCE
-
Saturated Calomel Electrode
OPC
-
Open Circuit Potential
OBM
-
Osteoblast Basal Medium
S.D
-
Standard Deviation
ECP
-
Eutectic Coherency Point
CR
-
Corrosion Resistance
GDS
-
Glow Discharge Spectrometer
ROI
-
Region Of Interest
HAGB
-
High Angle Grain Boundary
ISO
-
International Standard Organization
IC50
-
50% Inhibition Concentration
xxi
LIST OF SYMBOLS
ɸ
-
Channels internal intersection angle
Ψ
-
Channels outer intersection angle
Icorr
-
Corrosion current density
Ecorr
-
Corrosion potential
µ
-
Micron
Rt
-
Charge transfer Resistance
W
-
Warburg impedance
Cdl
-
Double layer capacitance
Rs
-
Resistance of electrolyte surface films
Tm
-
Melting Temperature
xxii
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
Publications
175
B
Certificate of heat treatments performed on fabricated
177
ECAP
C
Detailed isometric and projected drawing of fabricated
179
ECAP die.
D
ASTM G1-03 standard for corrosion products removed
186
and corrosion rate calculation.
E
Typical print out data of AAS flame techniques generated
188
F
Snap screen view of DEWESoft 7.5 data acquisition
190
software
G
Typical snap screen view of grains size analysis and
191
statistical results.
H
Snap screen view of VersaStat-3 (Princeton Applied
193
Research) electrochemical equipment
I
Snap screen view of simulated EIS corrosion experiments
194
results.
J
Q090 steel manufacturer elemental compositions
195
certificate
K
Snap screen view of Q090 steel GDS elemental
196
compositions result
L
Anova statistical analysis of MTS and ALP
biocompatibility results
197