Thesis_Final

Development of Layered Mg-Ti Composites
for Biomedical Applications
Thesis submitted towards partial fulfilment of the requirements
for the degree of
Master of Science in
Materials Science and Engineering
by
Niranjan Ramakrishnegowda
Matr.-Nr.: 1020406
Technische Fakultät
Christian-Albrechts-Universität zu Kiel
First supervisor Prof. Dr. Regine Willumeit-Römer
Second supervisor Dr. rer. nat. Thomas Ebel
Third supervisor Dr. Vasyl Mikhailovich Haramus
Geesthacht, Germany
March 2016

i
Declaration of Authorship
I, Niranjan Ramakrishnegowda, hereby declare that this thesis entitled “Development of
Layered Mg-Ti Composite materials for Biomedical Applications” is the result of my own
research work and was completed with authorized assistance. Wherever contributions of
others are involved, every effort is made to indicate this clearly, with due reference to the
literature, and acknowledgement of collaborative research and discussions. I agree that the
library of Helmholtz-Zentrum Geesthacht would make a free copy of this thesis available for
internal distribution. The reproducibility of the thesis or a part of thesis shall be brought into
the active notice of the author or Helmholtz-Zentrum Geesthacht. By signing this, I certify
that the thesis I am submitting is the final copy on approval from my supervisors.
________________________ ____________________________
(city, date) (signature)
Niranjan Ramakrishnegowda
First Supervisor
Prof. Dr. Regine Willumeit-Römer
Second supervisor
Dr. rer. nat. Thomas Ebel
Third supervisor
Dr. Vasyl Mikhailovich Haramus

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Acknowledgements
Firstly, I would like to express my sincere gratitude to my advisors Prof. Dr. Regine
Willumeit- Römer, Dr. rer. nat. Thomas Ebel and Dr. Vasyl Mikhailovich Haramus for the
continuous support during my master thesis, for their patience, motivation, and immense
knowledge. Their guidance helped me in all the time of research and writing of this thesis. I
could not have imagined having better advisors and mentors for my master thesis.
Besides my advisors, I would like to thank the rest of colleagues at WBM HZG: Mr. Johannes
Schaper, PhD student, Dept. of Material design and characterization, for his insightful
comments and encouragement, but also for the discussions which incented me to widen
my research from various perspectives.
My sincere thanks to Mr. Wolfgang Limberg, Scientist, Material design and
characterization, for his on-timely guidance and help during SEM analysis and for the
quality discussions which helped me to broaden my perspectives on understanding of
the work more.
The research leading to these results has received funding from the Helmholtz Virtual
Institute “In vivo studies of biodegradable magnesium based implant materials (MetBioMat)”
under grant agreement n° VH-VI-523.
I would like to remember all my staff, lab technicians and friends for providing me a
peaceful working environment and constant encouragement.
Last but not the least, I would like to thank my parents Ramakrishnegowda.K.P and
Gangalakshmi.R for supporting me in every aspect throughout this thesis and my life in
general.

iii
Contents
List of tables ..........................................................................................................v
List of figures .......................................................................................................vi
1 Introduction.....................................................................................................1
2 Theoretical background...................................................................................5
2.1 Metallic Biomaterials................................................................................5
2.2 Biomedical implants .................................................................................6
2.3 Titanium and its alloys for biomedical applications.................................7
2.4 Magnesium and its alloys for biomedical applications ............................8
2.5 Composite Materials...............................................................................10
2.6 Mutual solubility between different elements in the alloys ...................10
2.7 Metal Injection Moulding.......................................................................11
2.7.1 Powder...........................................................................................12
2.7.2 Binder............................................................................................13
2.7.3 Feedstock.......................................................................................13
2.7.4 Space holder technique..................................................................13
2.8 Debinding................................................................................................14
2.9 Sintering..................................................................................................15
2.9.1 Theory of sintering........................................................................15
2.9.2 Important aspects in the sintering of Mg alloys (Mg-0.9Ca)........17
3 Approach.......................................................................................................20
4 Materials and Methods..................................................................................22
4.1 Binder system .........................................................................................22
4.2 Powder processing..................................................................................22
4.3 Methods ..................................................................................................24
4.3.1 Binder preparation.........................................................................24
4.3.2 Feedstock preparation ...................................................................25
4.3.3 NaCl as space holders ...................................................................25
4.3.4 Sample Preparation by MIM.........................................................26
4.3.5 Layered composite materials by MIM..........................................28

iv
4.3.6 Dissolution of the space holders ...................................................30
4.3.7 Chemical/Solvent debinding .........................................................30
4.3.8 Thermal debinding and sintering ..................................................31
4.4 Sample Analysis .....................................................................................34
4.4.1 Density and porosity measurements..............................................34
4.4.2 Sample preparation........................................................................34
4.4.3 Microscopy Analysis.....................................................................35
4.4.4 Uniaxial bending test.....................................................................35
4.5 Possible cross contamination during polishing ......................................36
5 Results...........................................................................................................39
5.1 Different Samples developed..................................................................39
5.2 Optical micrographs of composite material produced by MIM.............40
5.3 Density dependence on sintering time....................................................41
5.4 Porosity dependence on sintering time...................................................42
5.5 SEM Analysis .........................................................................................43
5.5.1 Before uniaxial bending test..........................................................43
5.5.2 After uniaxial bending test............................................................57
6 Discussions....................................................................................................67
6.1 Composite material produced by MIM ..................................................67
6.2 Density dependence on sintering time....................................................67
6.3 Porosity dependence on sintering time...................................................68
6.4 Possible cross contamination during polishing ......................................69
6.5 Elemental distribution.............................................................................69
6.5.1 Before uniaxial bending test..........................................................69
6.5.2 After uniaxial bending test............................................................72
7 Conclusions...................................................................................................75
References ...........................................................................................................77

v
List of tables
Table 2-1 Summary of the physical and mechanical properties of various
implant materials in comparison to natural bone..................................................9
Table 4-1 Standard binder system for titanium...................................................22
Table 4-2 Binder system for magnesium. ...........................................................22
Table 4-3 Metal powders of Ti and Mg used in the work...................................23
Table 4-4 Grinding and polishing procedure for Mg-Ti composites..................35
Table 5-1 Overview of different samples produced in this work. ......................39

vi
List of figures
Figure 2-1 Mg-Ti phase diagram ........................................................................10
Figure 2-2 Flowchart illustrating the main stages of MIM.................................12
Figure 2-3 Microstructural changes of the compact during thermal debinding .14
Figure 2-4 Different stages of neck growth during sintering..............................15
Figure 2-5 A schematic of the microstructure changes during liquid phase
sintering, starting with mixed powders and pores between the particles............16
Figure 2-6 Mg-Ca phase diagram........................................................................17
Figure 2-7 Maximum solubility of Mg in Ca......................................................17
Figure 2-8 Inner crucibles, and outer crucibles with (left) and without (right)
Mg-getter materials .............................................................................................18
Figure 2-9 Pure Mg sintered without getter (left) and Pure Mg sintered with
getter (right).........................................................................................................18
Figure 3-1 Sample geometry (Mg-Ti composite). ..............................................20
Figure 4-1 Binder system heated to around 150o
C and mixed in Thinky mixer.24
Figure 4-2 Hand Mixing of the feedstock after heating......................................25
Figure 4-3 Feedstock of Titanium after granulating. ..........................................27
Figure 4-4 An inlay of the die of MIM with an arrangement to obtain rough
surface. A two way tape with salt on it. ..............................................................27
Figure 4-5 MIM tool with an arrangement to obtain rough Ti-6Al-4V samples.
.............................................................................................................................27
Figure 4-6 MIM tool with an inlay in it to obtain correct thickness of the sample
and a two way tape with salt to obtain roughness...............................................27
Figure 4-7 SE image of Ti-6Al-4V from SEM showing roughness achieved on it
with undercuts. ....................................................................................................28
Figure 4-8 as-sintered Ti-6Al-4V sample. ..........................................................28
Figure 4-9 Arrangement to obtain Mg-Ti composites. .......................................29
Figure 4-10 Image shows Mg-o.9Ca side of composites. After Mg-0.9Ca
deposition on to as-sintered Ti-6Al-4V (Bottom three) and composites after
sintering of Mg-0.9Ca (Top three)......................................................................29
Figure 4-11 Image shows Ti-6Al-4V side of composites. After Mg-0.9Ca
deposition on to as-sintered Ti-6Al-4V (Bottom three) and composites after
sintering of Mg-0.9Ca (Top three)......................................................................29
Figure 4-12 Ti-6Al-4V in water for dissolution of salt.......................................30
Figure 4-13 Time cycle for thermal debinding and sintering. ............................31
Figure 4-14 Brown and sintered parts of Ti-6Al-4V. .........................................32

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Figure 4-15 Temperature vs time graph for sintering of Mg-0.9Ca. ..................33
Figure 4-16 Apparatus used to bend the samples................................................36
Figure 4-17 Pure Ti-6Al-4V and Mg-Ti composites kept together for polishing.
.............................................................................................................................38
Figure 4-18 BSE image of Ti-6Al-4V after polishing........................................38
Figure 4-19 EDX analysis of area 1 in figure 4-18.............................................38
Figure 4-20 EDX analysis of spot 3 in figure 4-18.............................................38
Figure 4-21 BSE image of Ti-6Al-4V after polishing........................................38
Figure 4-22 EDX analysis of area 3 in figure 4-21.............................................38
Figure 5-1 Mg-Ti interface produced by MIM with flat Ti layer: ID1119-1. ....40
Figure 5-2 Mg-Ti interface produced by MIM with rough Ti layer: ID1119-2. 40
Figure 5-3 Mg-Ti interface produced by MIM with flat Ti layer: ID1119-1. ....40
Figure 5-4 Mg-Ti interface produced by MIM with rough Ti layer: ID1119-2. 40
Figure 5-5 Density dependence on different sintering times. .............................41
Figure 5-6 Archimedes and optical porosity dependence on the different
sintering times for Mg-0.9Ca layer. ....................................................................42
Figure 5-7 BSE image of a layered Mg-Ti composite with ID1119-2. ..............44
Figure 5-8 EDX analysis of area 1 from figure 5-7. ...........................................44
Figure 5-9 EDX analysis of area 2 in figure 5-7.................................................44
Figure 5-10 Line scan data of Mg.......................................................................44
Figure 5-11 Line scan data of Ca. .......................................................................45
Figure 5-12 Line scan data of Ti.........................................................................45
Figure 5-13 Line scan data of Al.........................................................................45
Figure 5-14 Line scan data of V..........................................................................45
Figure 5-15 BSE image of an interface between Mg and rough Ti with ID1119-
2. ..........................................................................................................................46
Figure 5-20 Line scan data of V..........................................................................46
Figure 5-21 BSE image of an interface between Mg and flat Ti with ID1119-1.
.............................................................................................................................47
Figure 5-22 EDX analysis of area 2 from figure 5-21........................................47
Figure 5-23 EDX analysis of area 3 from figure 5-21........................................47
.............................................................................................................................48

viii
Figure 5-25 Comparison between weight percentage of Ti and Al at different
spots from figure 5-24.........................................................................................48
Figure 5-26 BSE image of an interface between Mg-Ti with ID1119-3............49
Figure 5-27 EDX analysis of Spot 1 in the figure 5-26. .....................................49
Figure 5-29 EDX analysis of area 3 in the figure 5-26.......................................49
Figure 5-30 BSE image of an interface of Mg and Ti with ID1119-3................50
Figure 5-33 BSE image of Mg-Ti interface with ID1119-3. ..............................51
Figure 5-38 BSE image of Mg-Ti composite with ID1119-4.............................53
Figure 5-43 BSE image of Mg-Ti composite with ID1119-4.............................54
Figure 5-48 BSE image showing a presence of diffused Ti along the particle
boundary of Mg- ID1119-4.................................................................................55
Figure 5-49 EDX analysis of spot 1 in the figure 5-48.......................................55
Figure 5-51 BSE image of Mg-Ti interface with ID1119-5. ..............................56
Figure 5-56 BSE image of a fractured surface of Ti layer coated with Mg:
sample ID1119-2.................................................................................................57

ix
Figure 5-60 BSE image of a fractured surface of titanium coated uniformly with
magnesium: Sample ID1119-2............................................................................59
Figure 5-64 BSE image of a Mg-0.9Ca layer with traces of Ti left from the walls
between the undercuts of Ti-6Al-4V: sample ID1119-2. ...................................60
Figure 5-69 BSE image showing a fractured interface between Mg and flat Ti:
ID1119-1..............................................................................................................62
Figure 5-70 SE image showing a fractured interface with retained connection
between Mg and flat Ti: ID1119-1......................................................................62
Figure 5-71 SE image showing a fractured interface with retained connection
between Mg and flat Ti: ID1119-1......................................................................62
Figure 5-72 Image showing different looking directions in SEM. .....................62
Figure 5-73 BSE image of a titanium layer after fracture coated with
magnesium: sample ID1119-4. ...........................................................................63
Figure 5-75 EDX analysis of spot 2in the figure 5-73........................................63
Figure 5-78 BSE image of an interface between Mg and Ti showing retained
pore filling after breakage: ID1119-2..................................................................64
Figure 5-79 BSE image of a fracture interface between Mg and Ti: ID1119-5. 65
Figure 5-80 EDX analysis of area 1 in the above figure....................................66
Figure 5-81 EDX analysis of area 1 in the above figure.....................................66

x
Abbreviations
⍴ arc
Archimedes density.
⍴ geo
Geometrical density.
⍴ th
Theoretical density of Mg.
bcc Body centered cubic.
EDX Energy dispersive x-ray spectroscopy.
hcp Hexagonal close packed.
HZG Helmholtz-Zentrum Geesthacht.
Line scan Measuring the elemental composition along a particular line
profile.
MAP Master alloy powder (Mg-10 wt. % Ca).
Mg-0.9Ca Mg-0.9 wt.% Ca.
OM Optical microscope.
Pcl Archimedes porosity.
PM Powder metallurgy.
SEM Scanning electron microscope.
SFM Société pour la Fabrication du Magnésium, Switzerland.
Ti-6Al-4V Titanium with 6 wt.% Al and 4 wt.% V as α and β stabilizers
respectively.
WBM Material Design and Characterization.
WZP Magnesium-Prozesstechnik.
ZFW Zentrum für Funktionswerkstoffe gemeinnützige GmbH, Clausthal
Germany.

1
1 Introduction
With the advance of technology, people demand for an improved quality of living and
longevity of life. Such demands are expected to be fulfilled by biomaterials. Biomaterials are
artificial or natural materials used in the making of implants which help in regaining the form
and functionality of the lost or diseased biological structure. They serve as a boon to mankind
in the form of artificial bone replacements. They can be found in different parts of the body as
artificial valves in the heart, stents in blood vessels, replacement implant in shoulders, knees,
ears, elbows, legs and orthodontic structures [1]. In addition, biomaterials are also being used
for total hip replacements. For example, it has been projected that approximately 572,000
total hip replacements will annually be performed by 2030 in the world [2]. For many
centuries metals were used for biomedical applications. Currently 70-80% of the biomaterials
are metallic in nature. So far, a wide variety of metallic biomaterials have been invented. The
composition of a biomaterial is basically non-toxic. Among all metals, Titanium turns out to
be the most preferred metal because of its excellent biocompatibility, corrosion resistance,
and specific strength (ratio of the tensile strength to density), compared to stainless steels and
Co–Cr alloys [3].
Commercially pure titanium (CP) and its alloy Ti-6Al-4V are widely used clinically in
dentistry and orthopedic applications because of their good biocompatibility and mechanical
stability. Ti-6Al-4V is used because of its higher fatigue resistance in addition to its
exceptional strength in comparison to pure titanium [4].
Magnesium-based implants have the potential to serve as biocompatible,
osseoconductive, degradable implants for load-bearing applications because of the following
properties magnesium possesses. Magnesium is a lightweight metal with mechanical
properties similar to that of natural bone, a natural ionic presence with significant functional
roles in biological systems, and in vivo degradation via corrosion in the electrolytic
environment of the body [5].
Biocompatibility reflects the nature and degree of interaction between biomaterials
and host tissue and is one of the critical concerns in biomedical research [6]. The surface of
the implant material comes in direct contact with the host tissue and hence it plays a major

2
role in deciding the biocompatibility and mechanical stability of the implant material [7]. In
order to protect the body from foreign objects after implantation, reactions of the implants on
host blood/tissue as well as of the host on the implantable device have to be understood to
avoid health complications to the patient and/or device failure [6]. The degree to which the
homeostatic mechanisms are perturbed, the pathophysiological conditions created, and
resolution of the inflammatory response can be considered as a measure of the host reaction,
which ultimately determines the relative compatibility of the device [6].
Some common problems associated with Ti-6Al-4V alloy are the release of vanadium
and aluminum from it to the human body. Vanadium ions are cytotoxic and can cause small
osseointegration and limit the life span of the prosthesis, while aluminum ions can lead to
neurological disorder [4]. Because of such negative effects shown by Al and V on the human
body, its distribution in the Mg-0.9Ca layer of the composites being developed in this work
has to be avoided or controlled.
An implant material is expected to have Young’s modulus closer to that of bone (4 to
30 GPa depending on the type of bone and the direction of measurement). Current implants
have higher stiffness than bone, thereby avoiding stress transfer to the bone. This can cause
bone resorption and implant loosening and is termed as ‘stress shielding effect’ [1].
The implant's surface properties like surface chemistry, surface energy, topography
and roughness influence the initial cell response at the cell material interface, ultimately
affecting the rate and quality of new tissue formation. Hence the primary goal is to increase
the roughness of the implant surface. Current study is motivated by the importance of surface
roughness on the initial cell response at material interface.
Magnesium as an implant has the capability to enhance osseointegration between the
implant and the host blood/tissue. Hence this work develops a composite with a Mg layer to
enhance osseointegration. Drug delivery devices can effectively deliver the drug to a target
site and thus increase the therapeutic benefit, while minimizing side effects. The major goal
in designing such drug delivery devices is the controlled release (CR) of pharmacologically
active agents to the specific site of action at the therapeutically optimal rate and dose regimen
[8]. An important characteristic that the implant intended for drug delivery applications
should possess is optimal interconnected porosity in order to hold the drug for potential drug
delivery devices. The amount of drug absorbed and then released can be controlled by the

3
quantity and size of the pores present in the implant material and hence pore size control and
porosity control become important aspects when the implant has to act as a drug delivery
device [9]. In order to achieve drug delivery by a Mg layer, optimal porosity is an important
aspect to be obtained and will be tried in the present work.
Metal injection molding (MIM) is the technique used in order to obtain rough surface
of Ti-6Al-4V because MIM offers a net-shape or near-net shape fabrication route for the
making of complex shapes in large volumes [10]. Manufacturing of complex shapes like
prototypes of anatomically shaped aortic heart valve prosthesis, prototypes of implantable
bone screws for dens-axis repair has been possible by MIM. These products clearly depict the
ability of MIM to produce complex parts.
Biomaterial implants can either be used to replace a diseased part or to assist in the
healing process. While the former application requires implants to stay in the body
permanently, the latter only requires that the implant remains in the body temporarily. Thus,
in situations where a permanent implant is used for a short-term application, additional
surgeries are required to remove these devices once the healing process is complete. This
removal process increases the cost of health care and patient morbidity. In contrast,
biodegradable materials dissolve after the healing process is complete and thus, no additional
surgeries are required for removal of these implants. This also eliminates the complications
associated with long-term presence of implants in the body. In addition, once these materials
degrade within the body, it is important that the products from degradation are able to be
metabolized by the body, and thus are bioabsorbable. Polymers were the first material to be
used as commercial biodegradable and bioabsorbable implant materials. However, these
materials are limited by their low mechanical properties and radiolucency. Low strength of
polymers severely restricts their use in load-bearing and tissue supporting applications, as
greater amount of material is required to meet the mechanical needs of the body. In search of
materials which are biodegradable and bioabsorbable, metals serve as a potential alternative to
polymers because of their relatively high strength and fracture toughness. However, majority
of metals are biologically non-absorbable or toxic. Magnesium and its products from
degradation have excellent biocompatibility and are considered to be promising materials for
temporary medical implants [11].
Many researches have been conducted on permanent implants for load bearing
applications. This work is motivated by the lack of researches aiming to develop an implant

4
which possesses a combination of properties like that of permanent implants providing
necessary strength for load bearing applications and also providing an implant the ability to
enhance the initial integration between host bone/tissue and the implant material. Hence, this
work aims in developing a layered composite material with Mg-0.9Ca and Ti-6Al-4V. Mg-
0.9Ca layer acts as a bioabsorbable metallic implant and also has the ability of drug reservoir
only if it is possible to achieve interconnected porosities. Ti-6Al-4V layer acts as a permanent
implant.
In the current framework Mg-Ti layered composite is developed using MIM which is a
novel route for material design. This thesis explains the process technique feasible to develop
such composites. Rough surface preparation with undercuts (Rough surface is important for a
good mechanical interlocking of the host bone with Ti-6Al-4V layer after the Mg-0.9Ca layer
is degraded) on Ti-6Al-4V layer has been tried. The porosity of Mg layer is varied using
sintering time as an approach in order to achieve drug delivery. Uniaxial bending tests reveal
the mechanical stability of the interface. Characterization is done using optical microscope
(OM) and scanning electron microscopy (SEM). EDX analysis is also done to see element
distribution in the layers of the composite.

5
2 Theoretical background
2.1 Metallic Biomaterials
Metallic biomaterials started to find application in medical field as soon as the metal industry
had seen a revolution in 19th
century. Despite the fact that many different metals and alloys
can be made industrially, very few are biocompatible. A biomaterial is any biocompatible
material, natural or man-made, which is used to replace or assist part of an organ or tissue,
while in intimate contact with it.
Human tissue is made of polymers (proteins) and ceramics (bone minerals) with metal traces
playing molecular scale functions. However, metals and their alloys have played a
predominant role as structural biomaterials. Nevertheless, there are few critical issues about
metallic biomaterials in clinical applications such as toxicity of released metallic ions due to
degradation, fatigue failure of structural components due to repeated loading and wear off of
joint replacements due to movement.
Thus, there are several important essential considerations during the design of biomaterials.
The material should exhibit excellent biocompatibility, high corrosion resistance, mechanical
properties for suitable application, high wear resistance and osseointegration [12].
Depending on the tissue response, biomaterials can be classified as follows,
 Bioinert: On implantation, there is no or little interaction with the tissue in contact.
 Bioactive: On implantation, there is an interaction with the surrounding bone and also
with the soft tissue.
 Bioresorbable: On implantation, dissolving of the implant can be observed and a
gradual restoring by the advancing tissue [13].

6
2.2 Biomedical implants
There are several requirements materials should possess to be accepted as biomedical
implants. First and foremost being their biocompatibility, the body should accept the implant
and the implanted material should not cause any adverse effects like allergy, inflammation
and toxicity either immediately after surgery or under post-operative conditions. Secondly, the
implant should possess sufficient mechanical strength depending on the part of the body in
which it is implanted.
Another important property is that an implant should possess high corrosion resistance in a
corrosive body environment and wear resistance under varying load conditions. In addition,
fatigue strength and fracture toughness are also important for an implant material [14].
Apart from mechanical properties and biocompatibility, surface of implants play a major role
in the bioactivity at the interfaces of implant and bone. Surface texture development in the
form of macro pores to achieve good mechanical fixation with the bone or a coating of
bioactive ceramics and glass on the implant’s surface are some of the examples of chemical
surface modifications to accelerate the bone bonding [15].
Corrosion is a common problem biomedical implants face. The reason for the failure of
biomedical implants is the wear off which in turn accelerates the phenomenon of corrosion.
Hence high wear resistant materials are preferred to fabricate biomedical implants. In order to
obtain best combination of corrosion and wear resistance, several researches have been
undertaken. However, the nature and distribution of corrosion products released into the body
from these orthopedic implants remains an important issue. In this case, research on surface
modifications is of importance in order to enhance the surface-related properties of
biomaterials to reduce the failure of implants due to poor cell adhesion and leaching of ions
due to wear and corrosion [14].
Surface modifications are often performed on biomedical implants to improve corrosion
resistance, wear resistance, surface texture and biocompatibility [14].

7
2.3 Titanium and its alloys for biomedical applications
Ti was discovered in 1792 by William Gregor the British reverend, mineralogist, and chemist.
Ti ranks as the 9th
most plentiful element and 4th
most abundant structural metal. It is never
found in a pure state, hence making it expensive. It has a melting point of 1668o
C and the
electronic configuration is [Ar] 3d2
4s2
and a density of 4.5g/cm3
and hence it is considered as
the heaviest light element. Ti alloy stands out for its two important properties, high specific
strength and excellent corrosion resistance. This makes it possible for Ti to be preferred by
aerospace industry and medical engineering.
The crystal structure of Ti at ambient temperature and pressure is hexagonal close packed (α)
and at high temperature body centered cubic structure is stable (β). The lowest temperature at
which β Ti can exist is called β-transus temperature and it is 882±2o
C for pure Ti and ranges
between 700o
C and to as high as 1050o
C depending on the alloy composition. The physical
and mechanical properties of CP-Ti and Ti alloys can also be greatly varied with the addition
of small amount of elements oxygen, iron, carbon and nitrogen. The ease of plastic
deformation increases from hcp to bcc lattice. Final mechanical working and heat treatments
of Ti alloys are generally conducted below the beta transition temperature in order to achieve
the proper micro-structural phase distribution and grain size.
Depending on the amounts of α and β retained in its structure at room temperature Ti alloys
can be classified as alpha, near alpha, alpha-beta and beta alloys [16].
The alloy used in this work is the most often used alloy of Ti which is Ti-6Al-4V and this is
an α+β alloy which means that Ti-6Al-4V retains both α and β phases at room temperature.
Ti alloys are now the most attractive metallic materials for biomedical applications. In
medicine, they are used for implant devices replacing failed hard tissue. Examples include
artificial hip joints, artificial knee joints, and bone plates, screws for fracture fixation, cardiac
valve prostheses, pacemakers, and artificial hearts. Ti-6Al-4V has long been a main medical
Ti alloy. However, for permanent implant applications the alloy has possible toxic effects
because of the partially released Al and V ions and this leads to the development of implants
with new alloys free from Al and V for example Ti- 6Al-7Nb (ASTM F1295), Ti-13Nb-13Zr
(ASTM F1713), and Ti-12Mo- 6Zr (ASTM F1813) [17].
Several studies have been published to see the interactions of Ti with the proteins and cells
which show that Ti readily absorbs specific proteins like albumin, laminin V,

8
glycosaminoglycans, collagenase etc. Even though several researches have been published on
cell interactions with Ti, correlations have not yet been made between in vitro cell adhesion
and in vivo healing.
Surface modification of Ti has been an extensive research now a days. The insulating oxide
layer on Ti has an ability to absorb halogens (Cl, F), calcium ions, lanthanum ions and
phosphates. The effect of these fluorine ions to enhance bone pull-out is interesting. Surface
modifications involving developing a porous texture on the surface has good effect on the Ti
as implants. However, the effects are mechanical, achieving good mechanical interlocking.
Chemical surface modifications involving coating of bioactive ceramics and glasses are
prevalent and it is said that they help in achieving true bone bonding [15].
The effect of surface roughness of the Ti alloy Ti-6Al-4V on the short- and long-term
response of human bone marrow cells in vitro and on protein adsorption was investigated. It
was found out in this literature that cell attachment and proliferation were surface roughness
sensitive and increased as the roughness of Ti alloy increased [4].
2.4 Magnesium and its alloys for biomedical applications
Mg was discovered by Sir Humphrey Davy in 1755 at England. The name Mg is derived from
the Greek word "Magnesia", a district of Thessaly. Mg is a silver-white metal with the symbol
Mg. The atomic number is 12. It belongs to the group 2 of the periodic table (alkaline earth
metals). It is an exceptionally lightweight metal with a density of 1.74 g/cm3
, it is 1.6 and 4.5
times less dense than aluminum and steel respectively. Mg is essential to human metabolism
and is naturally found in bone tissue [18].
Mg reacts with oxygen to form magnesium oxide. The crystal structure is hexagonal-close
packed (HCP). It has a melting and boiling point of 650o
C and 1107o
C.
Mg is an essential component of human body. To meet the demand, the body needs 4.5mg/kg
bodyweight. It is involved in many enzyme reactions and together with Ca, it takes part in
signal transmission of the neurons [19].
Mg has seen lot of advent in biomedical applications. Metallic materials continue to play an
important role as biomaterials to assist with the repair or replacement of bone tissue that has
become diseased or damaged. Currently approved and commonly used metallic biomaterials

9
include stainless steels, titanium and cobalt–chromium-based alloys. A limitation of these
current metallic biomaterials is the possible release of toxic metallic ions and/or particles
through corrosion or wear processes that lead to inflammatory cascades which reduce
biocompatibility and cause tissue loss. In addition, the elastic moduli of the current
biomaterials do not match with that of bone causing “stress shielding effect”. Current metallic
biomaterials remain as permanent fixtures and demand a second surgery which increases the
costs [18].
All these disadvantages of the currently existing biomaterials are the motivation for
researchers to develop new biomaterials which possess same elastic moduli as bone. These
new biomaterials should also not contain toxic elements which creates a detrimental effect on
the biocompatible properties of the implant.
In the search of new biodegradable materials, Mg seems to be a promising material because of
its properties matching that of bone (see Table 2-1). Mg is osseoinductive and promotes bone
remodeling [20].
Table 2-1 Summary of the physical and mechanical properties of various implant materials in comparison
to natural bone [17].
Ca being an essential element in the human body, its salts are used to stabilize bones and
teeth and it is involved in many enzymatic reactions, its alloying into pure magnesium doesn’t
have negative effects on the human body [21]. Instead, addition of 0.5 to 3 mass% of Ca into
pure Mg results in an increase in degradation resistance and decrease of oxide layer thickness
compared to pure Mg above 480o
C thereby making the sintering of Mg easier [22].

10
2.5 Composite Materials
In a continuing expedition for improved performance of materials like improved strength, less
weight and lower cost, currently used materials reach the limits of usefulness. In this case
composite materials come into picture.
A composite is a material having two or more distinct constituents or phases. For a material to
be considered as a composite, there are three criterions to be satisfied. First, both the
constituents have to be available in reasonable quantities, say greater than 5%. Secondly, the
constituent phases have different properties so that the resulting composite properties are
noticeably different than the constituents itself. Lastly, a man made composite is made by
intimately mixing and combining the constituents by various means.
Composites have two (or more) chemically distinct phases on a microscopic scale, separated
by a distinct interface enabling to specify the constituents [23].
2.6 Mutual solubility between different elements in the alloys
Since this work involves the use of alloys of Mg and Ti which are Mg-0.9Ca and Ti-6Al-4V
respectively, it is important to check the phase diagrams of the elements involved in these
alloys to see how they combine each other.
Figure 2-1 Mg-Ti phase diagram [24].

11
As seen in the figure 2-1 there is little mutual solubility between Mg and Ti in any phase and
no intermetallic compound occurs. Thus, the equilibrium solid phases are low temperature α-
Ti and Mg solid solutions and the bcc solid (β-Ti) based on high temperature form of pure Ti.
A good mutual solubility is seen between Ti and Al [25] and also between Mg and Al [26].
The alloys used in this work are Ti-6Al-4V and Mg-0.9Ca. Because of the fact that there
exists a mutual solubility between Mg-Al and Ti-Al, Al is expected to induce a good
interconnection between the interfacial layers of Mg and Ti in this work.
2.7 Metal Injection Moulding
Metal Injection Moulding (MIM) is a modification of the common injection moulding process
for plastics where a significant volume fraction of plastic is replaced by a fine metal powder
[27]. It is a process by which powder is shaped into complex components by using tooling
and injection moulding machines that are very similar to those used in plastic injection
moulding. Like in powder metallurgy techniques, MIM relies on shaping metal particles and
subsequently sintering them. The final product is a nearly full density component. This
technique enables shape complexities, high production rates, and excellent performance and
often is lower in cost compared to the other competitive techniques. MIM technique is
typically for samples weighing approximately less than 100g. Obtaining a good surface finish
is another possibility associated with MIM. One of the important advantages of MIM has the
possibility to reuse the feedstock from the gate, runner, sprue and green parts with defects
thereby reducing the manufacturing costs.
MIM involves certain trail runs to be performed before a final sample preparation in order to
obtain optimum operating parameters. For example, when the moulding pressure or holding
pressure is low, low green density areas and incomplete filling of the mold can occur [28].
Porous materials are a class of materials with low density, large specific surface and a range
of novel properties in the physical, mechanical, thermal, electrical and acoustic fields. It is the
other possibility of MIM to produce such porous materials by space holder method [28].

12
Figure 2-2 Flowchart illustrating the main stages of MIM [29].
Initially, the metal powder (base metal and alloys or pre-alloyed powder) is mixed with binder
under heat input until a homogeneous compound is reached called feedstock (see figure2-2).
Obtained feedstock is cooled down and then granulated. The granulated feedstock is filled in
the hopper and it becomes molten on passing it through the screw because of the presence of
heating element. The molten feedstock is injected into the die at certain pressure to produce
green parts of required shape. The resultant product obtained after injection moulding is
called green part. During the process of de-binding, binder components are removed from the
green part and the de-bound part after de-binding is called brown part.
Sintering takes place after de-binding and is a process at which powder particles bond
together due to heat treatment performed at around 60% of the melting point of the metal.
After the process of sintering, the resultant product obtained is a volume-shrunk part with
certain porosity [30].
2.7.1 Powder
Powders can be classified depending on the shape as spherical or irregular shaped powders,
pure and impure depending on the percentage of oxygen impurity present in it or other
contaminations from the production process. There are different methods to prepare powder,
they are inert gas atomization, plasma rotating electrode processing, hydride-dehydrate
process and so on [31].

13
2.7.2 Binder
Binder has a vital role in deciding the rheological properties of the resulting feedstock during
moulding. Several binder system exists, either the components of the binder system itself can
be varied or the percentage composition of the same components can be varied. The
processing of feedstock occurs at temperatures above the final melt temperature of the binder
system but well below the decomposition temperature. The components used in the binder
should mainly possess an easily debinding capability and on the other hand, they guarantee
the stability of green and brown parts. The process of debinding has two steps, solvent
debinding which involves removal of solvent soluble binder component paving the way for
interconnections which helps in easy removal of the left components of the binder during
thermal debinding. Since thermal debinding is carried out at high temperatures prior to
sintering step, there is more possibility for oxidation and carbonization of the metal powders.
Hence high amount of second binder results in high oxidation and carbonization. Stearic acid
is used as the third component of binder system, it has the role of mold release, influencing
viscosity and improving the wettability of the powder [31].
2.7.3 Feedstock
Feedstock is composed fundamentally of metal powder and complex binder system. Any kind
of agglomeration should be overcome by rigorous mixing [31].
2.7.4 Space holder technique
This technique involves the use of space holder materials in order to obtain porous materials
or rough surfaces. Porous materials provide the ability to overcome the concern of long term
prosthesis, bone resorption due to stiffness mismatch between the bone and the implant [32].
Porous materials have already proved to be an excellent part to provide a good mechanical
support and also to achieve the ingrowth of bone so that a good integration can be obtained
with the host bone tissue.
This technique also offers an ability to control pore size and shape by varying and the size and
shapes of space holders used, with the potential to achieve good interconnectivity and pore
uniformity all over the specimen [33].

14
However, in this work, NaCl is used as space holders to achieve an uniform rough surface of
Ti-6Al-4V during sample molding by MIM.
2.8 Debinding
The use of binder is just an intermediate processing aid in order to hold the powder particles
in shape and hence it must always be removed. Debinding is carried out in two process steps
namely solvent and thermal debinding because binder removal only by providing thermal
energy results in defects like cracking and bloating resulting from stresses due to trapped
gases caused by decomposition of binders [28]. Solvent debinding in which a solvent soluble
component of the binder is removed at low temperature by immersing the part inside a solvent
like hexane [34]. This step creates a network for the escape of the binder during thermal
debinding step without cracking and causing sudden stress increase which distorts the sample.
After the removal of primary solvent soluble binders, there are still secondary binders left in
the sample which acts as a back bone in holding the particles to retain its shape produced by
Moulding. Removal of secondary binders involves heating of the samples to a temperature
where these binders can evaporate and holding the parts at this temperature to ensure the
complete removal of the binders and this step is called thermal debinding. If there is a
presence of more than one secondary binder then it involves holding the samples at two
different temperatures for the removal of the binders. The driving force for the thermally
debinded samples to retain its shape is the diffusion bond formed by the end of the process
[30].
Figure 2-3 Microstructural changes of the compact during thermal debinding [35].

15
Incomplete binder removal can occur either because of wrong debinding temperature or
insufficient time at the temperature. Gas flow rate is also an important aid for the binder
removal, insufficient gas flow results in an incomplete removal of the evaporated binder [35].
2.9 Sintering
Sintering is a heat treatment for bonding particles into a coherent, predominantly solid
structure via mass transport events that often occur on the atomic state. The bonding improves
strength and reduces the system energy. It is carried out at sintering temperature which is
typically 0.6 times the melting point of the alloy being sintered. It is a mass transport
mechanism which eliminates high surface energies [30].
2.9.1 Theory of sintering
Figure 2-4 Different stages of neck growth during sintering [28].
The driving force for the mass transport mechanism is the reduction of surface energy by
forming bond between two particles. In addition, atoms vibrate even in solid state, this
movement along with need to reduce surface energies results in bond between the particles.
This bond formation mechanism is enhanced by heating to the sintering temperature. On

16
holding the temperature to infinite times results in two particles ending up as one which is a
state of least energy. And hence different holding times results in densification to the different
extents there by affecting porosity and density inversely [28].
The process of mass transport resulting in bonding occurs as mentioned in the following steps.
Initially two powder particles come in contact, necks are formed and surface transport
mechanisms like evaporation and condensation (E-C), surface diffusion (SD) and volume
diffusion (VD) are predominate in causing the transport of atoms resulting in a growth of
necks. During surface diffusion, atoms move from the surface of the two particles and
diffusing to the neck resulting in a volume contraction of the particles and increase in neck
size [28].
2.9.1.1 Liquid phase sintering
Liquid phase sintering (LPS) is a process for forming high performance, multiple-phase
components from powders. It involves sintering under conditions where solid grains coexist
with a wetting liquid in a particular heating cycle. The solid grains undergo solid-state
sintering during heating. Depending on the solid–liquid solubility relations, different
microstructure evolution pathways are possible. The common situation is for the liquid to wet
the solid. In this case, the newly formed liquid penetrates between the solid grains, dissolves
the sinter bonds, and induces grain rearrangement. Further, because of solid solubility in the
liquid, the liquid improves transport rates responsible for grain coarsening and densification.
The result of LPS is densification and pore removal [36].
Figure 2-5 A schematic of the microstructure changes during liquid phase sintering, starting with mixed
powders and pores between the particles [34].

17
2.9.2 Important aspects in the sintering of Mg alloys (Mg-0.9Ca)
Figure 2-6 Mg-Ca phase diagram [37].
Figure 2-7 Maximum solubility of Mg in Ca [37].
Figure 2-6 shows the phase diagram of Mg-Ca. Figure 2-7 shows the area of this diagram
where the maximum solubility of calcium in magnesium occurs. The phase diagram shows a

18
double eutectic behavior. The maximum solubility of calcium in magnesium after [37] points
out to be 0.7 m.% (0.43 at.%). Calcium, on the other hand, has no solubility for magnesium.
The data of [37] agree with [38] but differs from older publications where the maximum
solubility is specified as 1.34 m.% [ [39], [40]]. Magnesium has an HCP structure and calcium
an FCC structure. The intermetallic phase Mg2Ca divides the phase diagram at about 45 m.%.
Two eutectics can be found, one on the magnesium rich and the other on the calcium rich side
of the diagram. The magnesium rich eutectic is at 16.33 m.% and 516.5 °C and the calcium
rich eutectic is at 80.36 m.% and 446.3 °C. Since this work deals with Mg-0.9Ca alloy and
sintered at 640o
C, only magnesium rich side is of importance. This area is dominated by the
heterogeneous two-phase crystal mixture α-Mg and Liquid (see encircled region in the figure
2-7).
Figure 2-8 Inner crucibles, and outer crucibles with (left) and without (right) Mg-getter materials
[41].
Figure 2-9 Pure Mg sintered without getter (left) and Pure Mg sintered with getter (right).
Exposing Mg to air results in an oxide layer of 3-4nm which inhibits the sintering of Mg [42].
Moreover, there is no solubility of oxygen in Mg, nevertheless an even higher affinity and
hence this oxide layer is not dissolved during sintering there by hindering the bonding

19
between the particles making the sintering of Mg time consuming and challenging. In order to
reduce the oxygen percentages in the Mg alloys being sintered, a new approach has been
reported. Mg getter material was used around the inner crucible No.1 and 2 within the outer
crucible No.2 (see left side image in figure2-8). This Mg getter material helps in protecting
the samples from oxygen contamination during sintering and meanwhile the temporary liquid
forming additive in the alloy (Ca) transforms into liquid phase thereby providing better
sintering conditions by removing the oxide layer on the Mg particles. By doing so, an
improvement in the compressive strength can be seen when the samples being sintered were
loose filled by Mg-getter whereas lower compressive strength can be seen for samples which
were not surrounded by getter at all. In addition, neck formation is apparent in case of
samples sintered with getter material whereas only point contact is apparent in case of
samples sintered without getter material [41].

20
3 Approach
Figure 3-1 Sample geometry (Mg-Ti composite).
Figure 3-1 shows the sample geometry of the Mg-Ti composite that has to be developed. It
will have a dense Ti-6Al-4V layer with an uniformly distributed rough surface with undercuts
to provide good mechanical fixation with the bone when the Mg-0.9Ca layer degrades and
also to provide necessary mechanical properties, and a porous Mg-0.9Ca layer which will act
as a drug delivery device only on achieving optimal porosity. Mg-0.9Ca layer is also believed
to enhance osseointegration between the implant and the host blood/tissue.
The goal of this work is to manufacture layered composites of Mg-Ti by MIM. These layered
composites are expected to serve dual functionality that is to be a permanent implant material
and also to be a drug reservoir for the later drug release applications. The approach used to
achieve the goal is the MIM technique. NaCl particles are used as space holders to obtain the
rough surface. 2-way tape is used on the metallic inlays to hold the NaCl particles intact.
Dissolution in water is conducted to remove the salt entrapments.
Optimal interconnected porosity is a very important parameter to be obtained in the layer of
Mg-0.9Ca in the composite to be eligible for drug delivery applications. The aim is to find a
way to vary the porosity of the Mg-0.9Ca layer. The approach adopted in this work is, varying
the sintering times during sintering of Mg-0.9Ca layer. For porosity measurements, optical
and Archimedes porosity is calculated using analySIS software tools and mathematical
formulae respectively.
Mg-0.9Ca
Ti-6Al-4V

21
Conducting uniaxial bending test is necessary to break the interface between Mg and Ti for
cross-sectional observation along the interface to check whether the interconnection is just
mechanical or a chemical bond exists between the two layers.
Interfacial and surface morphological studies are conducted using OM and SEM images. The
interfaces have to be observed before and after uniaxial bending test. In order to obtain
elemental distribution in two layers, EDX analysis is conducted using SEM. Several line, area
and spot measurements are essential to see the elemental distribution at the interface and also
in the bulk.

22
4 Materials and Methods
4.1 Binder system
Components Amounts (Wt. %)
Paraffinwachs 1.07157.1000 10
Paraffinwachs 1.07158.1000 50
Stearic acid 1.00671.9020 5
Lupolen V 2920 K 35
Table 4-1 Standard binder system for titanium.
Components Amounts (Wt. %)
Paraffinwachs 1.07157.1000 11.67
Paraffinwachs 1.07158.1000 58.33
Stearic acid 1.00671.9020 5
Polpropylene copolymer 25
Table 4-2 Binder system for magnesium.
Table 4-1 and 4-2 shows the binder systems used for Ti and Mg respectively. In order to
obtain dense part of Ti, 10 wt.% standard binder mass is used in the feedstock preparation.
Whereas, 22.69 wt.% of binder mass in feedstock is used in the feedstock of Mg in order to
obtain the porous structure of Mg.
4.2 Powder processing
In this study pre-alloyed spherical powder of Titanium, Ti-6Al-4V <45µm, grade 5 are used
(see Table 4-3). All the powders used are prepared by gas atomization technique by TLS
Technik, Germany.
Pure Mg [025] powder of particle size ≤ 45µm delivered by SFM-SA Martigny, Switzerland
and the Mg-Master alloy powder (MAP [017] X10) of particle size between 45-63µm
produced by ZfW, Clausthal-Zellerfeld, Germany are used (see Table 4-3). They both are

23
mixed in proper stoichiometric quantities during feedstock preparation with the binders of Mg
to obtain feedstock of Mg-0.9Ca alloy.
Used Powder Particle Size Manufacturer Chemical
composition
Ti-6Al-4V Pre-alloyed, Grade 5 <45µm TLS Technik Ti
(Balance),
6% Al and
4% V. For
Oxygen %
(see Table
2-1)
Pure Mg[025] 45µm SFM- SA Pure Mg.
[025]
refers to
the in-
house
labeling at
HZG.
MAP [017] X10 45-63 µm ZFW - HZG Mg-
0.9wt.%
Ca
Table 4-3 Metal powders of Ti and Mg used in the work.

24
4.3 Methods
4.3.1 Binder preparation
The binder system for Mg and Ti and its components are clearly mentioned in tables 4-1 and
4-2 respectively. Binder has four components. Paraffinwachs 1.07157.1000, Paraffin wax
1.07158.1000, Stearic acid and Polymer. Initially PW 1.07158.1000 and polymer is added and
hand mixed while heating and finally heated to a temperature of around 150o
C under argon
atmosphere in a glove box system (MBraun, Germany) and mixed in a planetary mixer
(Thinky ARE-250, Japan) for 5min at a speed of 2000RPM. These heating and mixing cycles
are continued until a homogenous mixture is obtained. The container is later taken to the
glove box and Paraffinwachs 1.07157.1000 and Stearic acid are added while heating and hand
mixing. The mixture is again heated to a temperature of around 150o
C and mixed in a Thinky
mixer. In the initial cycles homogenous mixture is not obtained. Hence heating is continued
on a hot plate outside the glove box and mixed in the Thinky mixer to obtain a homogenous
mixture of the binder. The mixture is left to dry and granulated by hand to obtain almost fine
granules of the binder system.
Figure 4-1 Binder system heated to around 150o
C and mixed in Thinky mixer.
Figure 4-1 shows the binder system which is heated to around 150o
C and mixed in Thinky
mixer at 2000RPM for 5min.

25
4.3.2 Feedstock preparation
Depending on the amount of feedstock required, weight of metal powder is decided and
depending on the weight% of binder in feedstock amount of binder to be added is calculated.
Both metal powders and binder are added to a steel box and heated to around 150o
C till the
binder is molten followed by hand mixing. Later the mixture is mixed in a Thinky mixer.
These heating and mixing cycles are continued till a homogenous mixture of the feedstock is
obtained (see figure 4-2). The resulting mixture is left to cool and granulated by hand to
obtain granulates of the feedstock.
Figure 4-2 Hand Mixing of the feedstock after heating.
4.3.3 NaCl as space holders
NaCl (SIGMA-ALDRICH, Molecular weight = 58.44, Melting point = 801 o
C) is selected as
a space holder in the current study because of ease of removal just by dissolution in water for
several hours. NaCl particles are sieved (Analysensieb, mesh width = 0.09mm and mesh
diameter = 0.063mm) to obtain equi-sized particles to have uniform pore size in the rough
sample.
NaCl as space holders are used to obtain uniform rough surface with undercuts on Ti-6Al-4V
samples.

26
4.3.4 Sample Preparation by MIM
Samples are prepared using Arburg Allrounder 320S metal injection moulding machine. MIM
has already been proved as a novel route to prepare samples without cracks. This capability of
MIM makes it possible to be used to obtain dense samples without cracks. MIM enables
shape complexity and hence shows a possibility to produce complex shapes as required by
this work. The target is to obtain dense Ti-6Al-4V samples with uniformly spread roughness
on top. In order to obtain a Ti-6Al-4V dense part with rough surface without cracks, the
samples are prepared by using MIM technique where a feedstock is granulated (see figure 4-
3) using a granulator of mixer blade type (Wittmann) and it is allowed to pass through the
screw of MIM in order to homogenize the feedstock and is granulated again and reused. The
arrangement to obtain rough surface of Ti-6Al-4V is seen in figure 4-4, figure 4-5 and figure
4-6 where a 2-way tape is stuck on to the metallic inlay and salt is poured uniformly on to the
top of the tape, it is also possible to obtain samples of different thickness by using metallic
inlays of different thicknesses. The metallic inlay stuck with tape and salt particles poured on
to the tape are placed into the die as seen in the figure 4-6. In order to obtain different amount
of roughness, few samples are made by using less salt on the tape and few other samples are
made with more salt on the tape to obtain less and more roughness pits with undercuts
respectively. Later, normal MIM procedure is followed where a molten feedstock is injected
into the die and an optimum amount of pressure is applied to obtain dense samples with
roughness. Samples are ejected from the tool and the sample is separated carefully from
sticking to the inlay to obtain the sample. Figure 4-7 shows SE image of rough Ti-6Al-4V
sample with undercuts obtained from MIM. Weights of all the samples are measured and
recorded to see the weight losses after dissolution, Solvent Debinding and sintering to ensure
the complete removal of Salt and Binder respectively.

27
Figure 4-3 Feedstock of Titanium after granulating.
Figure 4-4 An inlay of the die of MIM with an
arrangement to obtain rough surface. A two
way tape with salt on it.
Figure 4-5 MIM tool with an arrangement to obtain
rough Ti-6Al-4V samples.
Figure 4-6 MIM tool with an inlay in it to
obtain correct thickness of the sample and a
two way tape with salt to obtain roughness.
34mm

28
Figure 4-7 SE image of Ti-6Al-4V from SEM showing
roughness achieved on it with undercuts.
Figure 4-8 as-sintered Ti-6Al-4V sample.
A flat surface can be seen on as-sintered Ti-6Al-4V sample on one of the corners. This is
because of the high pressure involved in the MIM which pushes away the salt in the entrance
of the die to the bulk of sample and these entrapments are hard to remove just by dissolution
in water. After sintering, macro pores are apparent as shown in figure 4-8 which is from the
salt entrapments in the bulk which are burnt out during sintering.
4.3.5 Layered composite materials by MIM
The composite material prepared in this work is an interfacial layered composite of Mg and
Ti. Such a composite preparation involves two steps. Firstly, a Ti-6Al-4V layer with rough
surface is produced by MIM as described in the section 4.3.4. The layer of Ti-6Al-4V is
subjected to solvent debinding and sintering. Secondly, as-Sintered Ti-6Al-4V layer is stuck
inside the die on 2-way tape (see figure 4-9) and the same procedure is followed in MIM but
now with Mg-0.9Ca feedstock. The composite obtained are then solvent debinded and
sintered now for Mg-0.9Ca layer to obtain bonding between the two layers.
Flat Surface Macro Pores
34mm

29
Figure 4-9 Arrangement to obtain Mg-Ti composites.
Figure 4-10 Image shows Mg-o.9Ca side of
composites. After Mg-0.9Ca deposition on to as-
sintered Ti-6Al-4V (Bottom three) and composites
after sintering of Mg-0.9Ca (Top three).
Figure 4-11 Image shows Ti-6Al-4V side of
composites. After Mg-0.9Ca deposition on to as-
sintered Ti-6Al-4V (Bottom three) and composites
after sintering of Mg-0.9Ca (Top three).
The figures 4-10 and 4-11 shows a comparison between Mg-Ti layered composites before and
after sintering. It can be noticed that the Mg-0.9Ca layer after sintering has a volume
shrinkage because of which it possess a bulged layer of Mg-0.9Ca (See top three samples in
figures 4-10 and 4-11) in the corners compared to the bottom samples.
36mm
36mm
36mm

30
4.3.6 Dissolution of the space holders
NaCl is selected as a space holder because of the ease of removal of it just by placing the
sample in room temperature distilled water. The process of dissolution starts with a bubble
formation on top of the sample as shown in the figure 4-12. Dissolution of salt was done for
duration of 12h for every sample.
Figure 4-12 Ti-6Al-4V in water for dissolution of salt.
Since Ti-6Al-4V samples from MIM had undercuts entrapped with salts open to the surface,
dissolution is carried out where all the salt entrapments on the surface are removed where as
in order to remove the salt entrapments in the bulk (as mentioned in section 4.3.4), dissolution
is done after solvent debinding (for duration of 6h) because solvent debinding involves
removal of certain amount of binder component which leaves out pores which would help in
salt removal from bulk. However, this attempt is not much successful in complete removal of
salt from bulk.
4.3.7 Chemical/Solvent debinding
Binder is removed in two debinding steps, solvent debinding in which only one component of
the binder system is removed and thermal debinding in which rest of the components of the
binder system is removed because of high temperatures involved. Solvent debinding is carried
out at 40o
C for duration of 900 minutes with hexane as solvent in LÖMI EBA 50 debinding
furnace. The complete removal is proved when the weight loss before and after solvent
debinding corresponds to the weight of solvent soluble paraffin wax in the binder. The

31
samples after debinding are called brown parts. In order to avoid oxygen contamination the
brown parts are stored in the glove box.
4.3.8 Thermal debinding and sintering
4.3.8.1 Ti-6Al-4V layer in composites
Samples of Ti-6Al-4V are sintered using XERION XVAC 1600 furnace with tungsten heating
elements and shield packs of molybdenum. They are sintered at 1300o
C for 2h. Thermal
debinding is carried out for 4 h in 2 steps at 450°C and at 600°C under argon atmosphere.
Sintering process is further continued at temperature 1300°C for 2 h under high vacuum (<10-
4
mbar) and then cooled it to room temperature at 10 °C/min (see figure 4-13).
Figure 4-13 Time cycle for thermal debinding and sintering.

32
Figure 4-14 Brown and sintered parts of Ti-6Al-4V.
Weights and dimensions losses between green, brown and sintered parts are measured and
noted down to cross check the amount of binders removed. The volume contraction occurring
during the process can be seen in the figure 4-14.
4.3.8.2 Mg-0.9Ca layer in composites
Interfaces of as-sintered Ti-6Al-4V and Mg-0.9Ca are sintered in a hot wall furnace (XRetort,
Xerion) for 64, 32 and 4 h. Several flooding and evacuating cycles are carried out in order to
obtain a clean atmosphere before the heating is started. The samples are initially heated under
vacuum to a temperature of 300o
C at the rate of 8K/min and until 400o
C under vacuum at the
rate of 2K/min. Once the temperature is 400o
C, gas flow (Ar+ 5%H2) is started. This is to
remove the binders that are debinded during the initial thermal debinding cycle. Heating is
continued in the presence of gas flow. After 4 cycles of evacuating and flooding, heating is
carried out without gas flow, under vacuum. The last evacuating and flooding cycle is
performed, heating is carried out with Ar 6.0 at 500mbar. Once temperature of 645o
C is
reached, sintering is carried out for 64, 32 and 4h for different samples with the presence of
Ar 6.0 at 1050 mbar. After sintering, furnace is left to cool down at the rate 100K/min, but
this cooling rate is the set controller rate which differs from the actual rate at which furnace
cools. The heating cycle as shown by bold line in figure 4-15 refers to furnace heating
whereas the sample is subjected to different temperatures (see blue dotted line in figure 4-15)
when compared to the furnace. This can be observed from a graph in figure 4-15.
Brown Part
Sintered Part
35mm

33
Figure 4-15 Temperature vs time graph for sintering of Mg-0.9Ca.

34
4.4 Sample Analysis
4.4.1 Density and porosity measurements
For density measurements, Sartorious LA 230S density measurement meter, operating on the
principle of Archimedes is used. Archimedes density (⍴ arc) takes into account the volume of
the displaced fluid (absolute ethanol) which is directly proportional to the apparent weight
change of the immersed object (sample). Based on these density calculations, the Archimedes
porosity (Pcl) of the samples is calculated as shown in the equation below. ⍴ th refers to the
theoretical density of Mg.
Since it is not possible to conduct Archimedes density measurements for composites because
it involves two different metals, in this work, it is conducted for done bone shaped tensile
samples which are produced using same binder system as in case of Mg-0.9Ca layer in the
composites and also sintered in the same furnace run as composites.
Pcl = 1-
⍴ arc
⍴ th
(1)
Optical porosity is calculated using software analySIS. In order to avoid software related
errors during optical porosity calculation, pores are shaded, scanned and resulting image is
calibrated to the dimensions of original microscope image and region of interest (ROI) is
defined. Following this procedure gives optical porosity values.
4.4.2 Sample preparation
The composite interfaces obtained after sintering of Mg-0.9Ca layer are cut using Struers,
Secotom-10, Cleveland, USA into different shapes and dimensions depending on whether
they will be used for characterization in OM and SEM or for uniaxial bending tests. Samples
to be characterized by OM and SEM are mounted using Struers Labopress-3 and
Konductomet (BUEHLER, Illinois, USA). Konductomet is a conducting powder and is used
because it does not show charging on exposing to the high energy electron beams in the SEM.
Mounted samples are grinded and polished using MOTOPOL 2000 (BUEHLER, Illinois,
USA) to obtain good polishing results. Since polishing of Mg-Ti composites has no standard
operational procedure, the following steps are followed for the grinding and polishing of such

35
composites. In order to grind off the Konductomet holder enclosing the sample surface,
320grade SiC paper is used till the sample surfaces are reached.
Grades of SiC paper (unit) Duration (minutes)
Grinding
1000 2
1200 2
2400 2
4000 2
Polishing Polishing cloth (Mikromet) 7
Table 4-4 Grinding and polishing procedure for Mg-Ti composites.
Polishing of Mg-Ti composites are done using Mikromet WZM and OPS solution (Alkaline,
0.05µ) for 7min. Polishing is done using only OPS and distilled water for the initial 5min. In
order to remove the OPS, a lot of soap water is added and in the last minute distilled water is
used in order to completely get rid of OPS sticking to the polishing cloth. Samples after
polishing are rinsed with ethanol to remove the water from the pores and dried to make
samples ready for microscopic analysis.
4.4.3 Microscopy Analysis
Observation of interfaces between Mg and Ti is done using VEGA3 TESCAN-15kV,
Kohoutovice, Česká republika. Several images in BSE and SE modes are done to observe the
appearance of the interface. Several line scans, area scans and spot scans in the individual
layers and across the layers are done to see the elemental distributions using EDX analysis in
SEM.
4.4.4 Uniaxial bending test
The bending test is performed in equipment as shown in the figure 5-19. The equipment used
for bending is a mechanical utility tool used for the purpose of holding samples for cutting or
similar operations.

36
Figure 4-16 Apparatus used to bend the samples.
The process of breaking of composites on bending loads is observed for different cases, for
example, placing the composite in such a way that Ti-6Al-4V layer faces up and vice-versa.
Figure 4-16 shows the apparatus used to bend the composites. Ti-6Al-4V layer faces up in the
figure mentioned above.
Each composite with Mg-0.9Ca layer in the composite sintered to a different duration (64, 32
and 4h) to see the effect of sintering time on bonding (initially) between the layers is bent.
4.5 Possible cross contamination during polishing
This test is done to check if there is a possibility for the elements to migrate into the adjacent
layers as a result of polishing. Grinding and polishing of Mg-Ti composites has no standard
procedure so far and hence in this work a new grinding and polishing procedure is followed
using grinding papers of different grades as mentioned in section 4.4.2. The consequences
faced by the composites after following this procedure are illustrated below.
Figure 4-17 shows Pure Ti-6Al-4V kept together with composites for polishing. Figure 4-19
and 4-20 shows EDX analysis data of area 1 and spot 3 in figure 4-18 respectively. Presence
of small amounts of Mg and Ca in Ti-6Al-4V matrix can be observed. Even though, these
amounts are negligible, it is important to consider these small inclusions during analysis of
elemental distribution in section 6.5. Even on placing pure Ti-6Al-4V and composites in

37
different sample holders, some amount of inclusions of Mg and Ca are seen on Ti-6Al-4V
surface. During polishing of composites, since Mg and Ti layers are in contact, this effect due
to polishing will be enriched. However, it is still not clear how to distinguish the effect of
element diffusion due to sintering and elemental inclusions during polishing.
Figure 4-21 shows BSE image of Ti-6Al-4V after polishing. Figure 5-22 is an EDX analysis
data from area 3 in figure 4-21. It can be seen that the inclusions of Mg and Ca into Ti-6Al-
4V are not seen at several other areas of the same sample as in figure 4-18.

38
Figure 4-17 Pure Ti-6Al-4V and Mg-Ti composites
kept together for polishing.
Figure 4-18 BSE image of Ti-6Al-4V after
polishing.
Figure 4-19 EDX analysis of area 1 in figure 4-18. Figure 4-20 EDX analysis of spot 3 in figure 4-18.
Figure 4-21 BSE image of Ti-6Al-4V after polishing.
Figure 4-22 EDX analysis of area 3 in figure 4-21.
35mm
Pure Ti-6Al-4V
Composites
Ti-6Al-4V
Ti-6Al-4V

39
5 Results
5.1 Different Samples developed
The below table lists the different samples produced during this work.
Sample ID Method and procedure for sample preparation
ID1119-1: Flat Ti in contact
with Mg
ID1119-2: Rough Ti in
contact with Mg.
contact with Mg.
Note: All 3 samples are
sintered in Mg sintering
furnace for 64h.
MIM- Firstly, Ti layer with rough surface and undercuts are
produced by using an inlay stuck with 2-way tape and salt
particles. Later, as-sintered Ti sample is placed on the inlay
with the help of tape and normal MIM procedure is carried
out now by using Mg-0.9Ca feedstock to obtain a composite
of Mg-Ti. After solvent debinding and sintering of Mg,
characterization of the composite is done.
contact with Mg.
Sintering of Mg is done for
32h.
MIM- Same procedure as followed for ID1119-1,2,3.
contact with Mg.
Sintering of Mg is done for
4h.
MIM- Same procedure as followed for ID1119-1,2,3.
Table 5-1 Overview of different samples produced in this work.

40
5.2 Optical micrographs of composite material produced by MIM
Figure 5-1 Mg-Ti interface produced by MIM with
flat Ti layer: ID1119-1.
rough Ti layer: ID1119-2.
flat Ti layer: ID1119-1.
rough Ti layer: ID1119-2.
Figure 5-1 shows a layered Mg-Ti composite with a flat Ti-layer produced by MIM. A good
interconnection is established for a combination of flat Ti and Mg.
Figure 5-2 shows a layered Mg-Ti composite with a rough Ti-layer produced by using NaCl
particles. Pore filling of Mg into the undercuts of Ti is apparent in the figure. However,
several pores are present along the interface. The regions corresponding to the presence of
konductomet has pores whereas a good pore filling of Mg-0.9Ca can be seen.
Mg-0.9Ca
Flat Ti-6Al-4V
Rough Ti-6Al-4V
Mg-0.9Ca
Mg-0.9Ca
Rough Ti-6Al-4VFlat Ti-6Al-4V
Mg-0.9Ca
Konductomet
Pore filled Mg-0.9Ca

41
Figure 5-3 shows a layered Mg-Ti composite with a flat Ti-layer produced by MIM. A good
interconnection is established for a combination of flat Ti and Mg.
Figure 5-4 shows a layered Mg-Ti composite with a rough Ti-layer produced by using NaCl
particles. Pore filling of Mg into the undercuts of Ti is apparent in the figure. However,
several pores are present along the interface. The regions corresponding to the presence of
konductomet has pores whereas a good pore filling of Mg-0.9Ca can be seen.
5.3 Density dependence on sintering time
In this section, the data corresponding to the Archimedes density measurements of dog bone
shaped tensile samples of Mg.0.9Ca is presented. These dog bone shaped tensile samples are
produced using same binder system as in case of Mg-0.9Ca layer in the composite and also
sintered in the same furnace run.
Figure 5-5 Density dependence on different sintering times.
Figure 5-5 shows the Archimedes density dependence on different sintering times maintained
during the sintering of Mg-0.9Ca layers in different composite materials. Archimedes density
measurement is done for dog bone shaped tensile samples of Mg-0.9Ca and not for layered
composites. Increase in density can be seen on sintering for longer times.
1.6
1.62
1.64
1.66
1.68
1.7
1.72
4 32 64
Archimedesdensity(g/cc)
Sintering time (hours)
Archimedes density vs sintering time
Archimedes density

42
5.4 Porosity dependence on sintering time
To spot the influence of sintering time on porosity, optical and Archimedes porosities are
calculated.
All the optical porosity values plotted below corresponds to the porosity of Mg-0.9Ca layer in
the composite.
Since Archimedes density measurements is not possible for composites like Mg-Ti because of
the presence of two different metals. They are conducted for dog bone shaped tensile samples
of Mg-0.9Ca. These Mg-0.9Ca dog bone shaped samples are prepared using same binder
system as in case of Mg-0.9Ca layer in the composite and also sintered in the same sintering
run. Archimedes porosity values are calculated from Archimedes density using the equation 1
in section 4.4.1 and are plotted below.
Figure 5-6 Archimedes and optical porosity dependence on the different sintering times for Mg-0.9Ca
layer.
Figure 5-6 shows the dependence of optical and Archimedes porosity on different sintering
times maintained during the sintering of Mg-0.9Ca layer in different composite materials and
done bone shaped tensile samples respectively. Increase in optical and Archimedes porosities
can be seen on decreasing the sintering time. Archimedes porosity is a measure of closed
pores in the sample whereas optical porosity is a measure of total porosity in the samples.
0
1
2
3
4
5
6
7
8
9
10
4 32 64
Porosity(%)
Sintering time (hours)
Archimedes and optical porosity vs Sintering time
Archimedes porosity
Optical porosity

43
5.5 SEM Analysis
All the results of composites from SEM before and after bending are listed below.
All the figures with line scans have an arrow mark showing the direction in which line scan is
conducted. The line has 50 data points which are equally separated. Arrow edge points
towards the 50th
data point on the line scan plot whereas the other edge points to the 1st
data
point on the line scan plot.
5.5.1 Before uniaxial bending test
In this section, results from the samples analyzed before conducting uniaxial bending tests are
presented. Each composite is sintered for Mg layer to a different duration to see the effect of
sintering time on bonding between the layers.
5.5.1.1 Magnesium layer in the composite sintered for 64h
The composite which is examined in this section has a Ti-6Al-4V layer sintered at 1300o
C for
2h as mentioned in section 4.3.8.1 and Mg-0.9Ca layer sintered for 64h as mentioned in
section 4.3.8.2.
All the line scan graph of Intensity versus number of data points in line measurement has X-
ray counts per channel as the unit for intensity, and number of data points in line measurement
represents the small segments obtained on dividing the line length by 50.

44
Figure 5-7 BSE image of a layered Mg-Ti composite
with ID1119-2.
Figure 5-8 EDX analysis of area 1 from figure 5-7.
Figure 5-9 EDX analysis of area 2 in figure 5-7.
Figure 5-10 Line scan data of Mg.
Mg-0.9Ca
Direction of Line scan.

45
Figure 5-11 Line scan data of Ca.
Figure 5-12 Line scan data of Ti.
Figure 5-13 Line scan data of Al.
Figure 5-14 Line scan data of V.
Figure 5-7 shows BSE image of Mg-Ti composite with ID1119-2 (see table 5-1 in section 5.1)
and figure 5-8 to 5-14 shows the corresponding EDX analysis data and line scan data
associated with the BSE image respectively.

46
Figure 5-15 BSE image of an interface between Mg
and rough Ti with ID1119-2.
Figure 5-17 Line scan data of Ca. Figure 5-18 Line scan data of Ti.
Figure 5-19 Line scan data of Al. Figure 5-20 Line scan data of V.
Figure 5-15 shows BSE image of Mg-Ti composite with ID1119-2 (see table 5-1 in section
5.1). Figure 5-16 to 5-20 shows the variations in weight percentages of different elements
along the line scan 1 in the figure 5-15.
Direction of Line scan.
Mg-0.9Ca
Rough Ti-6Al-4V

47
Figure 5-22 EDX analysis of area 2 from figure 5-21. Figure 5-23 EDX analysis of area 3 from figure 5-
21.
5.1). Presence of Mg in Ti-6Al-4V and Ti in Mg-0.9Ca layer can be seen from the EDX
analysis data.
Mg-0.9Ca
Flat Ti-6Al-4V

48
Figure 5-24 BSE image of an interface between Mg
and flat Ti with ID1119-1.
Figure 5-25 Comparison between weight
percentage of Ti and Al at different spots from
figure 5-24.
Figure 5-24 shows BSE image of Mg-Ti composite with sample ID1119-1. Spot 1 and 2 show
a very high content of Ti whereas spot 3 and 4 shows Ti and Al diffusion along the grain
boundaries of Mg during sintering.
Mg-0.9Ca
Flat Ti-6Al-4V

49
The data shown below is from other composite interface sintered also for 64h with ID1119-3
(see table 5-1 in section 5.1).
Figure 5-26 BSE image of an interface between Mg-Ti with
ID1119-3
Figure 5-27 EDX analysis of Spot 1 in
the figure 5-26.
Figure 5-28 EDX analysis of Spot 2 in the figure 5-26.
Figure 5-29 EDX analysis of area 3 in
the figure 5-26.
Diffusion of Ti only along the particle boundaries of Mg-0.9Ca near to the interface can be
clearly seen from the figure 5-26. Porosity difference in Mg-0.9Ca layer near to the interface
and away from the interface can also be observed. Diffusion of Ti into Mg-0.9Ca layer is seen
only along the particle boundary of Mg-0.9Ca.
Mg-0.9Ca
Ti-6Al-4V

50
Figure 5-30 BSE image of an interface of Mg and Ti with ID1119-3.
Figure 5-31 EDX analysis of Spot 1 in the figure 5-30. Figure 5-32 EDX analysis of Spot 2
in the figure 5-30.
Both the effects can be observed from the figures 5-30 to 5-32 where a high amount of Ti is
present at spot 1 whereas spot 2 has low amount of Ti. Similar effect can be observed in a
different region of the same sample as shown in figure 5-33.
On comparing the particle sizes (before sintering) of pure-Mg and MAP used during the
preparation (see table 4-3 in section 4.2) to the scale bar in the figure 5-30, one can estimate
that spot 2 lies on the grain whereas spot 1 on the grain boundary.
Mg-0.9CaTi-6Al-4V

51
Figure 5-33 BSE image of Mg-Ti interface with ID1119-3.
Figure 5-34 EDX analysis of Spot 1 in the figure 5-33. Figure 5-35 EDX analysis of Spot 2 in the
figure 5-33.
Figure 5-36 EDX analysis of area 3 in the figure 5-33. Figure 5-37 EDX analysis of area 4 in the
figure 5-33
Mg-0.9CaTi-6Al-4V

52
Figure 5-33 shows the BSE image of an interface between Mg and rough Ti with ID1119-3
(see table 5-1 in section 5.1) showing diffusion of Ti only along the particle boundary. One
can also observe that the porosity of Mg-0.9Ca varies from near to the interface and away
from the interface.

53
Figure 5-38 BSE image of Mg-Ti composite with ID1119-4.
Figure 5-39 Line scan data of Mg. Figure 5-40 Line scan data of Ca.
Figure 5-41 Line scan data of Ti. Figure 5-42 Line scan data of Al.
5.1). Presence of Ca in the Ti layer can be made out from line scan data. It can also be
Ti-6Al-4V Mg-0.9Ca
Pore in Ti-6Al-4V filled with Mg. Pore in Mg-0.9Ca filled with Ti.

54
observed that there is a presence of Ti in the pores of Mg-0.9Ca near to the interface and vice-
versa.
Figure 5-43 BSE image of Mg-Ti composite with ID1119-4.
Figure 5-45 Line scan data of Ca.
Figure 5-46 Line scan data of Ti. Figure 5-47 Line scan data of Al.
Mg-0.9Ca
Ti-6Al-4V

55
5.1). Line scan is made only in the Mg layer to see the element distribution. High amounts of
Ti can be encountered at the points where low Mg is seen which means that Ti has diffused
into Mg layer and the low Mg corresponding to the particle boundaries of Mg where Ti is
seen diffused. In addition, several regions with low Mg also correspond to the pores which are
filled by Ti particles which are migrated during polishing.
Figure 5-48 BSE image showing a presence of diffused Ti along the particle boundary of Mg- ID1119-4.
Figure 5-49 EDX analysis of spot 1 in the figure 5-48.
Figure 5-50 EDX analysis of spot 2 in the figure 5-
48.
Figure 5-48 shows BSE image of Mg-Ti composite with ID1119-4 4 (see table 5-1 in section
5.1) . Figures 5-49 and 5-50 shows the EDX analysis of spot 1 and 2. On comparing the EDX
results of spot 1 and 2, it is clear that Ti is present only along the particle boundary.
Mg-0.9Ca

56
Figure 5-51 BSE image of Mg-Ti interface with ID1119-5.
Figure 5-52 Line scan data of Mg. Figure 5-53 Line scan data of Ca.
Figure 5-54 Line scan data of Ti.
Figure 5-55 Line scan data of Al.
5.1). It can be seen from the line scan data that even though there is sharp edge between Mg
Mg-0.9Ca
Ti-6Al-4V

57
and Ti, Ti is seen in the layers of Mg. Ca diffusion into the layer of Ti-6Al-4V can also be
seen.
5.5.2 After uniaxial bending test
Uniaxial bending test is conducted as show in the section 4.4.4. The appearance of the layers
after bending and breakage is presented in this section. It is important to note that, the uniaxial
bending test performed is not a quantitative test; rather, the test is conducted to observe the
basic bonding between Mg and Ti.
Figure 5-56 BSE image of a fractured surface of Ti
layer coated with Mg: sample ID1119-2.
Figure 5-57 EDX analysis of spot 1 in the
figure 5-56.

58
Figure 5-58 EDX analysis of spot 2 in the figure 5-56. Figure 5-59 EDX analysis of spot 3 in the
figure 5-56.
Figure 5-56 shows BSE image of fractured surface from sample ID1119-2. Spot 2 has pure
Mg whereas spot 3 corresponds to higher amount of MgO. However, a good coating of Mg is
seen on the rough surface of Ti-6Al-4V. Pore filling can also be seen in the figure 5-56.

59
Figure 5-60 BSE image of a fractured surface of
titanium coated uniformly with magnesium:
Sample ID1119-2.
Figure 5-61 EDX analysis of area 1 in the figure 5-
60.
60.
Figure 5-60 shows BSE image of fractured surface from sample ID1119-2. The coating of Mg
and Ca on the Ti-6Al-4V can be observed from the figure 5-60. EDX analysis at area 1, spot 2
and spot 3 shows all the elements from Mg-0.9Ca and Ti-6Al-4V.

60
Figure 5-64 BSE image of a Mg-0.9Ca layer with traces of Ti left from the walls between the undercuts of
Ti-6Al-4V: sample ID1119-2.
Figure 5-65 EDX analysis of area 1 in the figure
5-64.
Figure 5-66 EDX analysis of area 2 in the figure 5-64.
Figure 5-67 EDX analysis of area 3 in the figure
5-64.
Figure 5-68 EDX analysis of area 4 in the figure 5-64.

61
The bright areas in the figure 5-64 correspond to the traces of Ti-6Al-4V left on the Mg-0.9Ca
layer after fracture by bending and the dark areas correspond to the Mg-0.9Ca layer itself. Ti,
Al and V diffusion into the layer of Mg-0.9Ca and vice-versa can be observed by looking in
to the EDX data of different area scans.

62
Figure 5-69 BSE image showing a fractured interface
between Mg and flat Ti: ID1119-1.
Figure 5-70 SE image showing a fractured
interface with retained connection between Mg
and flat Ti: ID1119-1.
Figure 5-71 SE image showing a fractured interface
with retained connection between Mg and flat Ti:
ID1119-1.
Figure 5-72 Image showing different looking
directions in SEM.
Figure 5-69 and figures 5-70 to 5-71 show the BSE and SE images of fractured interfaces of
Mg-Ti composites with different looking direction in SEM respectively (see figure 5-72). A
retained interconnection even after applying bending loads is seen from the images.

63
Figure 5-73 BSE image of a titanium layer after fracture coated with magnesium: sample ID1119-4.
73.
Figure 5-75 EDX analysis of spot 2in the figure 5-73.
73.

64
Figure 5-73 shows BSE image of a Ti-6Al-4V layer after fracture, where it is coated with
MgO. Significant amounts of MgO layer can be seen on the Ti-6Al-4V layer and also in the
undercuts of Ti-6Al-4V.
Figure 5-78 BSE image of an interface between Mg and Ti showing retained pore filling after breakage:
ID1119-2.
It can be seen from figure 5-78 that, failure of an interface between Mg-0.9Ca and Ti-6Al-4V
under bending load has occurred in the Mg layer leaving out the bonded pore filling as it is.

65
Figure 5-79 BSE image of a fracture interface between
Mg and Ti: ID1119-5.

66
Figure 5-80 EDX analysis of area 1 in the above
figure.
Figure 5-81 EDX analysis of area 1 in the above
figure.
Coating of Mg and Ca on to the Ti-6Al-4V layer is achieved even on sintering just for 4h.
Diffusion effects between Mg-0.9Ca and Ti-6Al-4V layers are also seen in case of Mg-0.9Ca
layer sintered for 4h.

67
6 Discussions
6.1 Composite material produced by MIM
Figure 5-1, 5-2, 5-3 and 5-4 shows the optical images of composites of Mg-Ti produced by
MIM for the combination of Mg-0.9Ca and flat or rough Ti-6Al-4V.
A good interconnection formation for Mg-0.9Ca and flat Ti-6Al-4V combination could be
seen in the figure 5-1 and this was unexpected. This shows the possibility of MIM to develop
composites for the combination of Mg-0.9Ca and flat Ti-6Al-4V. This interconnection has a
good chemical bonding between Mg-0.9Ca and flat Ti-6Al-4V rather than just mechanical
interlocking, this could be seen after uniaxial bending tests were performed for this
combination of composite. Figures 5-69, 5-70 and 5-71 shows the interconnection between
Mg-0.9Ca and flat Ti-6Al-4V after uniaxial bending test. Even after uniaxial bending test, the
interconnection is still retained which was apparent in the figure 5-71.
For the combination of Mg-0.9Ca and rough Ti-6Al-4V, the above results still holds good
where a good filling of Mg-0.9Ca in the pores of Ti-6Al-4V was achieved. The black phase
seen in between the layers in the figure 5-2 was the conductive material from sample holder
(Konductomet). The reason for the presence of Konductomet in between the interface was
because of the presence of small pores between the layers of Mg-0.9Ca and Ti-6Al-4V.
Existence of pores between the interfaces was because of the effect from volume contraction
during sintering. Even for the combination of Mg-0.9Ca and rough Ti-6Al-4V, a good
mechanical interlocking exists. In addition, chemical bonding was also apparent from the
results after uniaxial bending tests. Figures 5-56, 5-60, 5-64 shows the existence of chemical
bonding between the two layers. Presence of Mg-0.9Ca in the pores of Ti-6Al-4V retained
after uniaxial bending also serves as a proof for the existence of chemical bonding between
the layers. Diffusion phenomenon was also seen occurring between the retained Mg-0.9Ca in
the pores of Ti-6Al-4V in the figure 5-56.
6.2 Density dependence on sintering time
Figure 5-5 shows a plot of density of Mg-0.9Ca dog bone shaped tensile samples versus
sintering times (4h, 32h and 64h). An increase in density was seen for increasing sintering

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