Friction Stir Welding (FSW) is the latest innovative and most complex process that is widely applied to the welding of lightweight alloys, such as aluminum alloys. this process provides the frictional heating and plastic deformation realized at the interaction between a non-consumable welding tool that rotates on the contact surfaces of the work-pieces. The welding tool is positioned vertically on the material and then moved at welding speed along the joint line. The plasticized material is transferred behind the tool, forming a welded joint. In this research, a new approach for friction-stir welding of similar alloys of aluminum alloy 6061 and using cerium particles. The weld mechanical properties of the welds were investigated in this research. The effects of friction-stir welding process parameters such as tool rotational and traverse speeds were also examined. Mechanical properties of the welded parts will be examined by using tensile test, Impact test, and Hardness test.

1. A Project Report on
INVESTIGATION ON FRICTION STIR WELDING OF
SIMILAR ALUMINIUM ALLOYS (AA6061) USING CERIUM
POWDER
Submitted in partial fulfillment of the requirement for the award of the degree of
BACHELOR OF TECHNOLOGY
in
MECHANICAL ENGINEERING
by
V. RENUKA REDDY (17911A03A9)
Under the guidance of
Mr. K RAJESH KUMAR
(Associate Professor)
Submitted to
DEPARTMENT OF MECHANICAL ENGINEERING
VIDYA JYOTHI INSTITUTE OF TECHNOLOGY
(An Autonomous Institution)
Approved by AICTE New Delhi & Permanently Affiliated to JNTUH, Accredited by NAAC & NBA,
An ISO 9001:2015 Certified Institution
Aziz Nagar Gate, C.B. Post, Hyderabad-500 075
(2020-2021)

2. DEPARTMENT OF MECHANICAL ENGINEERING
VIDYA JYOTHI INSTITUTE OF TECHNOLOGY
(An Autonomous Institution)
Approved by AICTE New Delhi & Permanently Affiliated to JNTUH, Accredited by NAAC &NBA, An ISO 9001:2015
Certified Institution
Aziznagar Gate, C.B. Post, Hyderabad-500 075
BONAFIDE CERTIFICATE
This is to certify that the project work entitled “INVESTIGATION ON FRICTION STIR
WELDING OF SIMILAR ALUMINIUM ALLOY (AA6061) USING CERIUM POWDER” is
bonafide project work submitted by D.RAKESH GOUD (17911A0371), V.RENUKA REDDY
(17911A03A9), T.NESHWANTH KUMAR (17911A03F4), K.PAVAN KUMAR (18915A0327) in the
department of Mechanical Engineering in partial fulfillment of requirements for the award of degree of
Bachelor of Technology in Mechanical Engineering for the academic year 2020-21. This work has been
carried out under my guidance and has not been submitted the same for any university/institution for
award of any Degree/Diploma.
PROJECT GUIDE HEAD OFDEPARTMENT
Mr. K RAJESH KUMAR Dr. G.SREERAM REDDY
INTERNAL EXAMINER EXTERNAL EXAMINER

3. ACKNOWLEDGMENT
The project entitled “INVESTIGATION ON FRICTION STIR WELDING OF SIMILAR
ALUMINIUM ALLOYS (AA 6061) USING CERIUM POWDER” is sum of total effort of
our batch. It is our duty to bring forward each and every one who is directly and indirectly in
relation with our project and without whom it would not have gained a structure.
We express our deep sense of gratitude to our respected guide, Mr. K. RAJESH KUMAR,
Associate Professor for his valuable help and guidance. We are thankful to him for the
encouragement he has given us to complete the project.
We also owe a great thanks to our institution VJIT, Moinabad and Mr. Dr. G. SREERAM
REDDY, HOD & Mr. K. RAJESH KUMAR, Associate Professor for their encouragement and
support in achieving success.
Finally we thank our professors, our parents, workshop technicians for their fine motivation and
inspiration.
V.RENUKA REDDY (17911A03A9)

4. ABSTRACT
Friction Stir Welding (FSW) is the latest innovative and most complex process which is widely
applied to the welding of lightweight alloys, such as aluminum alloys. In this process which
provides the frictional heating and plastic deformation realized at the interaction between a non-
consumable welding tool that rotates on the contact surfaces of the work-pieces. The welding
tool is positioned vertically on the material and then moved at welding speed along the joint line.
The plasticized material is transferred behind the tool, forming a welded joint.
In this research, a new approach for friction-stir welding of similar alloys of aluminum alloy
6061 and using cerium particles. The weld mechanical properties of the welds were investigated
in this research. The effects of friction-stir welding process parameter such as tool rotational and
traverse speeds were also examined. Mechanical properties of the welded parts will be examined
by using tensile test, Impact test and Hardness test.
Keywords: Friction stir welding, frictional heating, plastic deformation, cerium powder,
Mechanical properties

5. S. NO TABLE OF CONTENT PAGE
NUMBER
1 TITLE PAGE I
2 BONAFIDE Iii
3 ACKNOWLEDGEMENT Iv
4 ABSTRACT V
5 TABLE OF CONTENT Vi
6 LIST OF FIGURES Vii
7 LIST OF TABLES Viii
8 CHAPTER 1 – INTRODUCTION 1 – 4
9 CHAPTER 2 – LITERATURE
PROCESS VARIABLE IN FSW, FORMATION OF INTERMETALLIC
COMPONENTS, TOOL GEOMETRY, MATERIAL FLOW IN FSW,
5 – 13
10 CHAPTER 3 – OBJECTIVE METHODOLOGY 14
11 CHAPTER 4 – EXPERIMENTAL WORK
MATERIAL USED, PROPERTIES OF AA6061, TOOL DESIGN AND
FABRICATION, CERIUM POWDER, FSW MACHINE AND
EQUIPMENT
15 – 25
12 CHAPTER 5 – RESULT AND DISCUSSION
TENSILE STRENGTH, IMPACT STRENGTH, HARDESS STRENGTH
AND THEIR TESTS, TEST REPORTS
26 – 36
13 CHAPTER 6 – CONCLUSION AND FUTURE SCOPE 37 – 41
14 REFERENCES 41 – 42

6. LIST OF FIGURES
Fig. no. Caption Pg. no.
1 Schematic representation of Friction Stir Welding 2
2 Friction stir welding 3
3 Friction stir welding tool 3
4 Detailed view of FSW tool 7
5 Tool shoulder geometries, viewed from underneath the
shoulder
10
6 Showing metal flow pattern and metallurgical zones developed
during FSW
11
7 Methodology of FSW process 11
8 2D Model of designed tool in CAD software in Front view 14
9 Cerium powder 17
10 Similar AA6061 plates being welded with cerium powder 17
11 Showing the welded joints produced 19
12 Specimen mounted over Universal testing machine 20

7. ix
Fig. no. Caption Pg. no.
13 Images showimg the sample of tensile test specimen 21
14 Hardness testing machine 22
15 Hardness tested specimen 23
16 Impact testing machine 23
17 Impact tested specimen 24
18 Tensile testing machine 24
19 Tensile tested specimen 25
20 Hardness test specimen of welded material 27

8. x
LIST OF TABLES
Table. No. Caption Pg. No.
1 Key benefits of Friction Stir Welding 4
2 Details of Materials 15
3 Nominal chemical composition of AA6061 15
4 Nominal physical and chemical composition of AA6061 15
5 Chemical composition of H13 tool steel 16
6 Physical properties of Cerium powder 17
7 Showing the process parameters used for welding joints
with and with Cerium powder
20
8 Tensile Test Results with and without Cerium powder 26
9 Hardness Test Results with and without Cerium
powder
27
10 Impact Test Results with and without Cerium powder 27

9. xi
CHAPTER -1
INTRODUCTION
The friction-Stir welding (FSW) is a new welding technique in domain of welding. It is solid
state welding process and invented by the welding institute (TWI) of Cambridge, England in
1991. This process is simple, environment friendly, energy efficient and becomes major
attraction for an automobile, aircraft, marine and aerospace industries due to the high strength of
the FSW joints as near as base metal. It allows considerable weight savings in light weight
construction compared to conventional joining technologies. In contrast to conventional joining
welding process, there is no liquid state for the weld pool during FSW, the welding takes place in
the solid phase below the melting point of the materials to be joined. Thus, all the problems
related to the solidification of a fused material are avoided. Materials which are difficult to
fusion weld like the high strength aluminium alloys can be joined with minor loss in strength.
In friction-stir welding a non-consumable rotating tool with a specially profiled threaded/
unthreaded pin and shoulder is rotated at a constant speed. The tool plunges into the two pieces
of sheet or plate material and through frictional heat it locally plasticized the joint region. The
tool then allowed stirring the joint surface along the joining direction. During tool plunge, the
rotating tool undergoes only rotational motion at only one place till the shoulder touches the
surface of the work material; this is called the dwelling period of the tool. During this stage of
tool plunge it produces lateral force orthogonal to welding or joining direction. The following
diagram depicts the procedures of FSW.
The upper surface of the weld consists of material that is dragged by the shoulder from the
retreating side of the weld, and deposited on the advancing side. After the dwell period the tool
traverse along the joining direction, the forward motion of the tool produces force parallel to the
direction of travel known as traverse force. After the successful weld, the tool reaches to
termination phase where it is withdrawn from the work piece. This is shown in fig. 1.

10. xi
During the welding process the parts have to be clamped rigidly onto a backing bar in a manner
that prevents the abutting joint faces from being forced apart. The length of the tool pin is
slightly less than the weld depth required and the tool shoulder should be in intimate contact with
the work surface.
Fig. 1 Schematic representation of FSW.
Besides tight clamping of the members to be welded, the key to success is to select the optimum
parameters which include rotational speed, welding speed, axial force, and tool pin as well as
shoulder profile. Detailed description of FSW process is shown in Fig.2.

11. 13
Fig 2. Friction stirs welding process
Above diagram of friction stir welding indicates two terms advancing side and retreating side,
when rotation of tool is the same as the tool traverse direction along weld line is called
advancing side and when rotation of tool is opposite to the tool traverse direction is called
retreating side. Non consumable tool is most important tool in friction stir welding process, it
serves following function like heating of the work piece, movement of material to produce joint
and containment of the hot metal beneath the tool shoulder. Friction stir welding tool consist pin
and shoulder and both has individual purposes.
Fig 3. FSW Tool

12. 14
In recent development, the FSW has found application into the welding of the circumference,
cylinders, curvilinear, three dimensional objects and objects which require finer executing the
movements. FSW is considered to be the most significant development in metal joining in a
decade and is a ‘‘green’’ technology due to its energy efficiency, environment friendliness, and
versatility. The process has the unique characteristics, as there is no melting of parent material,
the alloying elements are not lost and thus mechanical properties are preserved. Therefore, the
degree of combining different materials is high and hence increases the possibility of welding
materials which was difficult to weld. As compared to the conventional welding methods, FSW
consumes considerably less energy. No cover gas or flux is used, thereby making the process
environmentally friendly. Key benefits of FSW process are enlisted in table 1.
Table 1: Key benefits of friction stir welding
Metallurgical benefits
• Solid phase process
• Low distortion of work piece
• Good dimensional stability and repeatability
• No loss of alloying elements
• Excellent metallurgical properties in the joint area
• Fine microstructure
• Absence of cracking
• Replace multiple parts joined by fasteners
Environmental benefits
• No shielding gas required
• No surface cleaning required
• Eliminate grinding wastes
• Eliminate solvents required for degreasing
• Consumable materials saving, such as rugs, wire
or any other gases
Energy benefits
• Improved materials use
• Only 2.5% of the energy needed for a laser weld
• Decreased fuel consumption in light weight
aircraft, automotive and ship applications

13. 15
CHAPTER-2 LITERATURE
REVIEW
Aluminium and its alloys show unique characteristics like light weight, high strength, high
toughness, extreme temperature capability, versatility of extruding, and excellent corrosion
resistance. Those make it the obvious choice of material by engineers and designers for the
variety of engineering applications.
Many researchers, they have given copious attention towards the parameters optimization like
rotational speed (N), traverse speed (ʋ) and axial force (F) and apart from parameters
optimization they have also given sufficient focus to find out the effect of tool pin profile on
friction stir welding joints that yields optimum characteristics of joint. But very less work has
been done on tool shoulder like effect of tool shoulder profiles and tool shoulder geometry on
mechanical properties of friction-stir welded joint.
2.1 Process variables in FSW
The tool rotational speed (N), welding speed (ʋ) and the axial force (F) are the three important
welding variables in FSW. The study of the effect of welding variables on the friction stir
welding process is important because it directly decides the weld quality of the FSW joint. The
welding process affects the joint properties primarily through heat generation and material flow.
The rotation speed (N) results in stirring and mixing of material around the rotating pin and the
translation of the tool moves the stirred material from the front to the back of the pin. The axial
force (F) is another important parameter to avoid the frictional slippage at the tool work piece
interface.

14. 16
V. Paradiso, F. Rubino analyzed on the variation in mechanical properties during friction stir
welding of dissimilar alloys. The materials chosen for friction stir welding were ZE41A Mg
alloy and AA2024-T3 Al alloy. Both the materials were of plate form with 4 mm thickness.
Friction stir welding was carried out offsetting the tool of 1 mm towards the magnesium side.
The tool was made up of high speed steel consists of a shoulder diameter of 20mm , a conical
unthreaded pin of height 3.80 mm, major diameter 6.20 mm, and cone angle 30 deg. The process
parameters selected were Tool rotational speed ranging from 1000 to 1400 rpm, feed rate
ranging from 20 to 80 mm/min, tilt angle of 2° and shoulder plunge depth of 0.48 mm.
Y. Zhao, L. Huang investigated the effects of tool travel speed on mechanical properties of final
weld. The materials chosen were Al 5754/AZ31 Mg alloy plates of 3mm thickness. The tool was
made of H13 Tool steel with concave shoulder with diameter of 16 mm and a threaded pin with
the length of 2.8 mm. and a constant tile angle of 3.5° was maintained Al alloy was placed on the
AS and Mg alloy on the RS as per trials. Three kinds of defects had been detected during the
experiment surface peeling, overflow of solidified microstructure and groove like defect are
detected due to the variation in selected process parameters.
P. Venkateswaran studied about the various factors that affect the weld quality during friction
stir welding of Al/Mg dissimilar alloys. The materials chosen were AA 6063 aluminium and
AZ31B Mg alloys. The welding was done using tool made up of H13 Tool steel with a fluted
probe. Tool rotational speed from 900-2700rpm, Tool travel speed from 1.69-6.4mm/min and
axial force from 14-30KN were selected.
Preheating or cooling can also be important for some specific FSW processes. For materials with
high melting point such as steel and titanium or high conductivity such as copper, the heat
produced by friction and stirring may be not sufficient to soften and plasticize the material
around the rotating tool. Thus, it is difficult to produce continuous defect-free weld. In these
cases, preheating or additional external heating source can help the material flow and increase
the process window. On the other hand, materials with lower melting point such as aluminium

15. x
cooling can be used to reduce extensive growth of recrystallized grains and dissolution of
strengthening precipitates in and around the stirred zone.
Formation of Intermetallic compounds
The formation of Intermetallic phases during dissimilar welding using conventional fusion
welding is an issue because it can impair the joint integrity severely depending on the thickness.
Formations of Intermetallic compounds are greatly influence by welding parameters and the
resultant temperature as well. Though the Intermetallic formation is not completely avoidable in
majority cases its effect, thickness etc. can be reduced thus contributing to the final weld quality.
M. Tabasi had concentrated on the Friction stir welding of dissimilar Al/Mg alloys. The alloys
chosen were Al 7075 & AZ31 Mg having 5mm thickness. Silicon carbide nanoparticles were
introduced into the weldment for the formation of metal matrix composites. Tool rotational speed
of 450, 560, 710,900, and 1100 rpm and traverse speed of 11.2, 22.4, 35.5, and 45 mm/min were
selected as process parameters. The tool selected for experimentation was of H13 Tool steel
material with triangular threaded pin.
Tool Geometry
Tool geometry is the most influential aspect of process development. The tool geometry plays
critical role in material flow and in turn governs the traverse rate at which FSW can be
conducted. An FSW tool consists of a shoulder and a pin as shown schematically in Fig. 2.1.
Fig.4. Schematic diagram of the FSW tool

16. x
As mentioned earlier, the tool has two primary functions: (a) localized heating, and (b) material
flow. The friction between the shoulder and work piece results in the biggest component of
heating. From the heating aspect, the relative size of pin and shoulder is important. The shoulder
also provides confinement for the heated volume of material. The second function of the tool is
to ‘stir’ and ‘move’ the material. It is desirable that the tool material is sufficiently strong, tough
and hard wearing at the welding temperature.
Tool shoulders are designed to produce heat (through friction and material deformation) to
surface and subsurface regions of the work piece. The tool shoulder produces a majority of the
heating in thin sheet, while the pin produces a majority of the heating in thick work pieces. Also,
the shoulder produces the downward forging action necessary for weld consolidation. Tool pin is
designed to disrupt the faying, or contacting, surface of the work piece, shear material in front of
the tool, and move material behind the tool.
Fujii et al. investigated the effect of tool shape on mechanical properties of friction stir welded
aluminium alloys. Prospecting the optimal tool design for welding steels, the effect of the tool
shape on the mechanical properties and microstructures of 5mm thick welded aluminium plates
was investigated. The simplest shape (column without threads), the ordinary shape (column with
threads) and the triangular prism shape probes were used to weld three types of aluminium
alloys. For 1050-H24 whose deformation resistance is very low, a

17. x
Columnar tool without threads produces weld with the best mechanical properties, for 6061
whose deformation resistance is relatively low, the tool shape does not significantly affect the
mechanical properties.
Apart from tool pin design there is significant impact of tool shoulder profile and tool shoulder
geometries on weld quality. Various tool shoulder geometries have been designed by TWI. These
geometries increase the amount of material deformation produced by the shoulder, resulting in
increased work piece mixing and higher-quality friction stir welds. Following figure consists of
scrolls, ridge or knurling, grooves, and concentric circles and can be machined on any tool
shoulder profile.
Fig.5. Tool shoulder geometries, viewed from underneath the shoulder
Galvao et al. studied the influence of tool shoulder geometry on properties of friction stir welds
in thin copper plate. The welds were produced using three different shoulder geometries like flat
shoulder, conical shoulder and scrolled shoulder with varying the rotational and welding speed
of tool. After experiment we observed that scrolled tool provides the best flow of material that
yield defect free welding and scrolled tool also provides greater grain refinement that gives
better weld strength and hardness with respect to flat and conical tool.

18. x
Zhang et al. investigation has been carried out by rotational tool without pin but different
geometry over bottom surface of tool shoulder. The experiments of FSW are carried out by using
inner-concave-flute shoulder, concentric-circles-flute and three spiral- flute shoulder with
welding speed of 20mm/min and 50mm/min and constant rotational speed of 1800rpm. In case
of three spiral-flute shoulder tensile strength of joint increases with decreasing of welding speed
while the value of tensile strength attended by the welding speed of 20mm/min and rotational
speed of 1800mm/min is about 398Mpa, which is more than parent material strength.
Material flow in FSW
The FSW process can be modeled as a metalworking process in terms of five conventional metal
working zones: (a) preheat, (b) initial deformation, (c) extrusion, (d) forging, and (e) post
heat/cool down. Typical zones obtained during the process are shown in Fig 2.3. In the preheat
zone ahead of the pin, temperature rises due to the frictional heating of the rotating tool and
adiabatic heating because of the deformation of material. The thermal properties of material and
the traverse speed of the tool govern the extent and heating rate of this zone. As the tool moves
forward, an initial deformation zone forms when material is heated to above a critical
temperature and the magnitude of stress exceeds the critical flow stress of the material, resulting
in material flow. The material in this zone is forced both upwards into the shoulder zone and
downwards into the extrusion zone, as shown in Fig.2.3.
Fig.6. Showing (a) Metal flow pattern and (b) Metallurgical processing zones developed
during friction stir welding

19. x
A small amount of material is captured in the swirl zone beneath the pin tip where a vortex flow
pattern exists. In the extrusion zone with a finite width, material flows around the pin from the
front to the rear. A critical isotherm on each side of the tool defines the width of the extrusion
zone where the magnitudes of stress and temperature are insufficient to allow metal flow.
Following the extrusion zone is the forging zone where the material from the front of the tool is
forced into the cavity left by the forward moving pin under hydrostatic pressure conditions. The
shoulder of the tool helps to constrain material in this cavity and also applies a downward
forging force. Material from shoulder zone is dragged across the joint from the retreating side
toward the advancing side.

20. x
Won-Bae Lee, et.al (2006), examined Friction Stir Welding (FSW) of AZ91/SiC/10p resulted in
the creation of SiC particles that were homogenously distributed. It was found that the microstructural
alteration resulted in an increase in the weld zone's hardness and wear properties relative to the base metal
ones. The hardness outside the weld zone was higher and distributed more homogeneously, and the wear
resistance within the weld zone, as measured by the common wear loss, was higher than the base metal.
The creation of phases containing elements from the welding tool provides evidence of the friction stir
welding abrasion of the welding tool. The weld zone's hardness was homogeneous and had higher values
than the Base Metal (BM) and the wear properties in the weld zone were also improved .
A Kouadri-Henni, et.al. (2014), demonstrated the microstructural and anisotropic modifications in
a thin sheet of magnesium alloy (AZ91), caused by FSW. The results of this study show that FSW
induces several distinct zones with different microstructural, anisotropic, and mechanical properties to be
produced. This study observed that complex changes in microstructural and mechanical properties occur
due to FSW welding in the case of heterogeneous deformation in a multi-phase material. These results are
considered a basis for future investigation to better understand the microstructural and mechanical
properties of welding materials. The most surprising finding was that crystallographic textures existed in
two zones from a base metal without texture: the thermo-mechanically affected areas and the stir welded
areas .
A Shanmugasundaram, et.al. (2015), compared the microstructural changes and variability in
tensile strength of cast magnesium alloy joints prepared from gas tungsten arc welding (GTAW) and
strong friction stir welding (FSW). Of the two joints made, the FSW joint yielded 190 MPa tensile
strength, which is 2.6% lower and 7.4% higher than the base metal and GTAW joint respectively.
Longitudinal tensile analysis showed that the stirzone yielded 245 MPa, 20 percent higher than the base
metal and 14 percent higher than the GTAW joint. The results proved that FSW joint showed superior
tensile properties compared to GTAW joint, which was due to the difference in microstructural gradient
across the weld cross section .

21. x
Parviz Asadi, et.al. (2015), established a finite element model (FEM) to study the microstructure
evolution of AZ91 magnesium alloy during friction stir welding (FSW). Parameters like hardening, the
parameter of recovery and the sensitivity of the strain rate needed for the system, were determined based
on the results of the flow pressure. A model based on the combination of cellular automaton and
Laasraoui-Jonas models was proposed to test weld zone microstructure. Results show that the weld zone's
virtual microstructure was in good agreement with the experiments. Under different system conditions,
the simulated grain size increases, which is shown by increasing the w / v parameter [16, 17].
P Asadi, et.al. (2012), investigated the effects on the microstructure and mechanical properties of
friction stir welded AZ91 magnesium alloy by water cooling procedure, rotational direction of the system
(RD) and friction stir processing pass number.The samples were produced using various process
parameter combinations. Results showed that water cooling increased the hardness and reduced the final
size of the grain, while the amount of oxide particles increased in the processed region. Nevertheless,
there is a crucial FSP passage beyond which the grain size remains almost constant in the absence of
water cooling. The study concluded that adjusting the RD in each pass significantly reduces grain size
(due to more suitable nucleation sites being produced during dynamic recrystallization) and significantly
increases hardness and tensile strength. Due to the pinning of the grain boundaries that limits the grain
growth, the oxide particles reduce the final grain size. Although FSP changes the mechanical properties
of the AZ91 alloy under different conditions, the effect of these changes on wear resistance is negligible
[19].
Z Zhang, et.al. (2012), predicted the tool forces using the Adaptive Remeshing Technique based on
the FSW finite element model. The study found that the tool forces increased with the increase in
transverse speed in three directions (perpendicular to the welding line, along the welding line and along
the tool axis) and decreased with the increase in angular speed. The maximum is the axial force of the
tool and the minimum is the force of the tool in the direction perpendicular to the weld line. The non-
uniform material flow induced this force. The study also found that the maximum temperatures on the
welding plate and on the tool can be increased with the increase in angular velocity of the welding tool
[20].

22. x
Fang Chai, et.al. (2013), measured the microstructure and superplastic tensile behavior of fine-
grained AZ91 magnesium alloy, which was prepared by submerged friction stir processing (SFSP). The
results showed a remarkable grain precision in magnesium alloys as-cast AZ91, with 7.8 mm and 1.2 mm
respectively the average grain size of the standard FSP and SFSP AZ91 alloys. The study concluded that
SFSP contributes to significantly increased superplasticity compared to normal FSP. At 623 K, an
elongation of 990 million is reached, suggesting that the AZ91 SFSP alloy has excellent superplasticity of
high strain speed (HSRS). On the other hand, the failure elongations of the standard FSP AZ91 alloys are
all below 200%. The SFSP material's excellent HSRS is due to its finer grain structures which comprise a
larger fraction of the grain boundary. Grain growth and coalescence of cavities is the main mechanism of
failure during superplastic deformation for standard FSP and SFSP alloys [21].
D. Sammaiah, et.al. (2015), found that, from experimental study, the variability of the toughness across
the weld is uniform and homogeneous in nature due to the distribution of the interfaced reinforcement of
the newly formed grains in the magnesium matrix. Due to high tool rotational speed leading to poor bond
formation with a number of FSW defects found, the variability of the strength across the weld is non-
uniform and inhomogeneous in nature for 1400 rpm tool rotational speed. The hardness increases with
increase of rotational speed. With a constant tool rotational speed, the tensile strength increases with a
decreased tool translation speed. The reduction in heat generation leads to a decrease in the material's
plastic flow and thus the formed metallurgical bond has a lower resistance. Analysis of the mechanical
and metallurgical properties of the welded joints of ZE41 magnesium alloy shows that mechanical stirring
is the main mechanism of metal flow in the formation of metallurgical bonds. Comparison of the joints '
mechanical and metallurgical properties showing that the joint properties and bond strength depend on
mechanical stirring and the newly formed grains. The rotational speed of the tool strongly influences the
newly formed grains during welding
CHAPTER-3 OBJECTIVE – METHODOLOGY
It has been observed that most of the experimental work in the field of friction stir welding of
similar metals or alloys has been carried out by making straight Lap joints between flat plates

23. x
Design of friction stir welding tool in solid works
Fabrication of friction stir welding tool using H13 steel
Welding of similar aluminium AA6061 using the
fabricated tool
using different tool pin profiles by different researchers. After extensive literature survey, it was
found that very less work has been done on FSW of dissimilar alloys on aluminum alloys. Thus
on the basis of literature survey the current research on similar Aluminium Alloy AA6061 has
been finalized. The research mainly focuses on the mechanical properties and strength of the
weldment. In order to improve the weld joints Cerium powders are introduced in the friction stir
welding.
Methodology: the methodology adopted in this research work is as shown in figure below.
.
Fig.7. Methodology of FSW Process
Testing of the weld joint for tensile test, hardness,
impact and microstructure
Results and Discussion

24. x
CHAPTER-4
EXPERIMENTAL WORK
Materials Used
The similar materials Chosen for FSW in this research work are Aluminum AA6061 and their
dimensions are shown in table below.
Chemical composition of Aluminum AA6061 work material as given below:
Table 2: Details of materials
No. Item Specifications Qty.
1. AA 6061 sheet metal 120mm (Length)x75mm(Breadth)X5mm(width) 12No.s
Table 3: Nominal chemical composition of AA6061
Element Al Mg Si Fe Cu Cr Zn Ti Mn Others
%(Weight) 96.85 0.9 0.7 0.6 0.30 0.25 0.20 0.10 0.05 0.05
Physical & Thermal composition of Aluminum AA6061 work material as given below:
Table 4: Nominal Physical & Thermal composition of AA6061
Properties Strength
Ultimate Tensile strength 290MPa
Yield strength 241MPa
% of Elongation 12-25
Thermal Conductivity 166 W/m-ᵒK
Melting Temperature 650 ᵒC

25. x
Properties of Aluminum alloy 6061
• It is a precipitation hardened aluminum alloy containing magnesium &silicon as major
alloy components.
• It has good mechanical properties and good weld ability.
• It is one of the most common alloys of aluminum for general purpose use.
Tool design and fabrication
Chemical composition of work piece AA6061 aluminum alloy is non-heat treatable series of
aluminum alloys so non consumable tool with H13 tool steel has been designed using CAD
software and has been fabricated.
Table 5: Chemical composition of H13 tool steel
H13 steel Tool
Elements Weight in %
Carbon 0.32-0.45
Chromium 4.75-5.50
Molybdenum 1.10-1.75
Vanadium 0.80-1.20
Iron Balance
Silicon 0.80-1.25
Sulpher 0.30 max
Phosphorus 0.30 max
Manganese 0.25-0.50
The below figure shows CAD model of friction stir tool which was used in welding. Dimensions
of geometry which was made over tool shoulder with convex angle of six degrees and the pin
length was given as 9.6 mm.

26. x
Fig 8: 2-d model of designed tool in cad software in front view
The shoulder diameter was taken as 25 mm and the pin diameter was ¼ of the shoulder diameter
i.e, 8.3mm and was further tapered to 7.3 mm, the pitch on the pin was taken as 0.6mm.
Cerium powder
The cerium powder is used in the experimental procedure and the properties are listed
in the below table.
Figure 9 : Cerium powder
Table 6: Properties of Cerium powder
Molecular Weight 140.12(gm/mol.)
Appearance Metalloid
Melting Point 2340 °C
Boiling Point 3500 °C
Density 6.0 g/cm3
Specific Heat
390 J/kg-k
Thermal Conductivity 18.72 W/(m·K)

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FSW machine and equipment
A HMT knee type vertical milling machine has been used to fabricate the joints is shown
in Fig. Friction stir welding setup has been installed over this milling machine knee type vertical
milling machine. This has a facility of rpm ranges from 50 to 1800 rpm and traverse speed
ranges from 16 to 800 mm/min which made possible to do number of experiments by varying
welding speed and rotational speed and tool holding spindle can be rotated either direction
(clockwise or counter clockwise direction), maximum traverse length of machine table is 500
mm over which work piece is kept For conducting actual experiments it requires a fixture which
can hold the welding plates firmly and prevents the rotary and translator motions. Fixture has
been properly installed over milling machine bed is as shown in Fig 4.7.Fixture has been
properly installed over the bed of VF3.5 knee type vertical milling machine which is shown in
Fig.4.7. Material used to make a fixture is cast iron 27 which has higher damping coefficient and
shock absorbing capabilities so that it will sustain during the actual experiments and provides
best clamping.

28. x
Experimental procedure
The AA6061 aluminum alloy sheet has been cut into desired dimensions of
120mmx75mmx5mm by power hacksaw machine. Lap joint configuration has been prepared to
fabricate FSW joints. Single way welding procedure has been used to fabricate the joints with
friction stir welding tool with and without cerium powder and attempt has been made to find out
effect of difference on mechanical properties of FSW joints. No preprocessing treatment was
carried out before welding and testing. Non-consumable tools made of H13 tool steel has been
used to fabricate the joint.
Figure 10: Similar AA6061 plates being welded with Cerium powder
The weld was carried out using the required parameters. For the joints made with titanium powder
a 2mm groove was made from the center of the plates i.e 5mm and to a depth of 1.5mm and the
cerium powder was filled into the grooves manually and hen the plates were fixed on to the fixture
using the backing plate and fastened using bolts.
Process Parameters
There were totally three different process parameters used in the experimental procedure and
6 experiments were conducted in total three with cerium powder and three without cerium
powder. The parameters are listed in the below table.

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Table 7: Showing the process parameters used for welding joints with and without
cerium powder
Experiment No. Tool Speed(RPM) Feed (mm/min) Tool angle (Degrees)
1 710 16 2
2 900 20 2
3 1100 25 2
Weld joints
The weld joints produced using these parameters are shown in the below figure.
Figure 11: showing the weld joint produced
Tensile test
The welded joints are sliced using power hacksaw and then machined to the required
dimensions to prepare tensile specimens according to, American Society for Testing of Materials
(ASTM E8M-04) guidelines is followed for preparing the test specimens. Tensile test has been
carried out in 100 kN, electro-mechanical controlled Universal Testing Machine (INSTRON) as
shown in Fig. The specimen is loaded at the strain rate of 2mm/min as per ASTM specifications,
so that tensile specimen undergoes deformation as shown in Fig. The spec1imen finally fails
after necking and the load versus displacement has been recorded. The 0.2% offset yield
strength; ultimate tensile strength and percentage of elongation have been evaluated. Instron
Ultimate Tensile Machine (UTM) is used for performed tensile test, and so on.

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Figure 12: specimen mounted over the universal testing machine (instron)
A universal testing machine (UTM), also known as a universal tester,materials testing machine or
materials test frame, is used to test the tensile strength and compressive strength of materials. An earlier
name for a tensile testing machine is a tensometer.
Components of UTM
1.Load frame
2.Load cell
3.Cross Head
4.output device
The Impact test machine is an ASTM standard method of determining the impact resistance of materials.
A pivoting arm is raised to a specific height (constant potential energy) and then released. The arm
swings down hitting a notched sample, breaking the specimen. The energy absorbed by the sample is
calculated from the height the arm swings to after hitting the sample. A notched sample is generally used
to determine impact energy and notch sensitivity.

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Figure 13: image showing the sample of tensile test specimen
Rockwell hardness test
The Rockwell test is generally easier to perform, and more accurate than other type of hardness
methods. The Rockwell test method is used on all metals, except in condition where the test
metal structure or surface conditions would introduce too much variations; where the
indentations would be too large for the application; or where the sample size or sample shape
prohibits its use. The Rockwell method measures the permanent depth of indentation produced
by a force/load on an indenter. The test was conducted on the Rockwell hardness testing machine
with a load of 150kg and using a 1/16 inch ball indenter and the values were observed in HRF
scale.

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Figure 14: Hardness Testing Machine
Figure 15: Hardness Tested Specimen
Impact test
The Impact Test entails striking a notched impact specimen with a swinging weight or a “tup”
attached to a swinging pendulum. The specimen breaks at its notched cross-section upon impact,
and the upward swing of the pendulum is used to determine the amount of energy absorbed
(notch toughness) in the process. Energy absorption is directly related to the brittleness of the
material. Since temperature can affect the toughness of a material, the charpy test is performed at
a series of temperatures to show the relationship of ductile to brittle transition in absorbed
energy.

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Figure 16: Impact testing machine
Figure 17: Impact tested Specimen
Figure 18: Tensile testing machine

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CHAPTER-5
RESULTS AND DISCUSSIONS
The welded plates with cerium and without cerium powder are sliced using power hacksaw and
then machined in vertical milling machine to the required dimensions to prepare for tensile test and
the specimens are as shown below in Fig.5.1. American Society for Testing of Materials
(ASTME8M-04) guidelines was followed while preparing the specimens for test.
Fig.19 Tensile test specimen of welded material
Tensile test were carried out over UTM and 0.2% offset yield strength, ultimate tensile strength and
percentage of elongation have been evaluated. Engineering stress-strain curve for welded
specimens were obtained and are as shown in figure below.
Transverse tensile properties of FSW joints such as ultimate tensile strength, yield Strength and
percentage of elongation have been evaluated as shown in Table. Specimens were tested at each
condition. It can be inferred that the tool shoulder geometry, welding speed and rotational speed
are having influence on tensile properties of the FSW joints. Of the eight joints, the joints
fabricated without cerium powder exhibited superior tensile properties

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Table 8: Tensile test results of welded joints with and without cerium powder.
S. No Tool
speed
(rpm)
Feed
(mm/min)
Tool
angle
(degree)
Elongation
%
Ultimate tensile
stress (N/mm2)
Ultimate load
(KN)
1 710 16 2 8.04 159.87 9.52
2 900 20 2 7.44 165.86 9.64
3 1100 25 2 8.04 158.71 9.44
4 710 16 2 8.42 170.47 9.48
5 900 20 2 4.36 141.47 8.16
6 1100 25 2 7.74 137.38 7.28
The tensile strength values were observed to be lower in the joints made with titanium powder.
Due to the grooves made in the plates there were air gaps created in between the weld joint.
Second reason is that because of more stirring in nugget zone at high rotational speed and low
welding speed that reduces grains size of particles thus hardness increases which cause
brittleness in joint. Ultimate tensile stress as well as % of elongation is more in case of the weld
joints made with titanium powder because there were no air gaps created in the weld zone.
Hardness and Impact test properties
The hardness was best observed in the weld joint made with cerium powder as cerium is
considered to be the hard material compared to aluminium, introducing it in the weld joint
increased the hardness of the weldments.
Fig.20. Hardness test specimen of welded material

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S.No Tool
Speed
(rpm)
Feed
(mm/min
)
Tool
angle
(degree)
Indenter Load applied Average
Hardness
Material used
(Cerium)
1 710 16 2 Diamond
pyramid
500gf 58.94
Without Cerium
Powder
2 900 20 2 Diamond
pyramid
500gf 66.32
3 1100 25 2 Diamond
pyramid
500gf 74.35
4 710 16 2 Diamond
pyramid
500gf 57.67
With Cerium
Powder
5 900 20 2 Diamond
pyramid
500gf 54.36
6 1100 25 2 Diamond
pyramid
500gf 68.29
Table 9: hardness test results with and without cerium powder
Table 10: Impact Test results with and without powder
S.No Tool
Speed
(rpm)
Feed
(mm/min
)
Tool
angle
(degree)
Impact
Test
(joules)
With Material
(Cerium powder)
1 710 16 2 11.5
Without Cerium Powder
2 900 20 2 11.5
3 1100 25 2 9.5
4 710 16 2 12.0
With Cerium Powder
5 900 20 2 12.0
6 1100 25 2 12.0
.

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CHAPTER-6
CONCLUSI
ON
In this investigation an attempt has been made to study the effect of cerium powder in the weld
joint of similar aluminum alloys AA6061. The tensile properties, hardness, impact properties and
have been obtained, it is concluded that
➢ The tensile strength is higher in the joints made without cerium powder.
➢ By using cerium powder in the friction stir weld joints only the hardness has
been improved and the other properties of the weld joint have reduced.
➢ The optimum parameters that were observed in the investigation are were at 900RPM,
feed rate of 60 mm/min and tool angle 2 degrees.
➢ The maximum tensile stress obtained is 9.52 KN and elongation% of 4.36%.
FUTURE SCOPE
• In this investigation an attempt has been made to study the effect on cerium
powder in the weld joint of dissimilar aluminium alloys AA6061.
• The tensile properties, hardness, impact properties. The investigation can be
done by preheating the cerium powder and introducing it in the weld joint.
• The welding parameters can be changed and also different tool geometries can
be used to do the research.

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