Jurnal Kejuruteraan 35(1) 2023: 13-28
https://doi.org/10.17576/jkukm-2023-35(1)-02
13
Influence of Welding parameters on Mechanical property during Friction Stir Welded
joint on Aluminium Alloys: A Review
Aditya Mamgain, Vivek Singh & Ajay Pratap Singh
Department of Mechanical Engineering, AKGEC, Ghaziabad, Uttar Pradesh.
*Corresponding author: vivekgwt@gmail.com
Received 12 February 2022, Received in revised form 24 June 2022
Accepted 28 July 2022, Available online 30 January 2023
ABSTRACT
The friction stir welding (FSW) is widely used in the fabrication of Aluminium alloy and other non-ferrous alloy. It has good
potential to be used in major industries such as automobiles, aerospace, shipbuilding and can be used in the joining of
high strength alloys. The FSW process low distortion and heat affected zone (HAZ) with fine recrystallized microstructure
which leads to better mechanical properties at the weld zone and produces great stability. In this study, the different FSW
parameters such as weld speed, tool rotation speed, tool tilt angle, feed per min has been discussed. The different types of
tool pin profile and shoulder have also been discussed and their impacts on mechanical and microstructural properties at
welded joints. Among various welding parameters the rotational speed is the most influencing parameter in FSW. Increasing
the rotational speed exhibits the increase at tensile strength and is supposed to improve the mechanical properties. The
most affected tool pin profile would be considered to be tapered threaded cylindrical pin profile which makes the adequate
mixing of material with better flow ability and provide the fine grains at nugget zone. Comparing the FSW with other arc
welding processes, it shows a wide range of environmental benefits which are noticeable such as saving in consumable
materials, decrease in consumption of filler material and reduction in grinding wastes. Harmful emissions created from arc
welding causes a health hazard to the welder. For achieving the high joint-strength for aerospace aluminium alloys and
high temperature sustainable metallic alloys, friction stir welding will be preferred.
Keywords: Aluminium; tool design; rotational speed; welding tool speed; tool profile; mechanical properties
INTRODUCTION
Friction stir welding (FSW) is a solid-state welding process
which has been recognized for its potential of joining for
high strength aluminium alloys. It was first invented and
patented by TWI in the year 1991. During the development
phase, the friction welding only restricted to aluminium
alloy and mainly used to reduce the weight of aircraft
but with the span of time, its research area increased to a
range of materials, which is possible due to development in
tool profiles. The aluminium alloys have rapidly gathered
attention for a wide range of structural application as well
as for innovation in improvement of the welding technique.
It is being extensively used for similar as well as dissimilar
joining of Al, Mg, Cu, Ti and their alloys. Possibly it
is difficult to join dissimilar material using solid-state
joining methods without having the compatibility issues of
physical properties of the materials as well as formation of
intermetallic compounds. Hence, a suitable interlayer which
prevents the formation of intermetallic compounds is often
employed in such cases.
Friction stir welding (FSW) has emerged as one of
the vital alternative technologies which has good potential
to use in major industries like automobiles, aerospace,
shipbuilding, railways and can be used in high strength
alloys.
With the use of friction stir welding, the common
problems of fusion welding such as solidification, liquation
cracking and porosity have become vanished. As the
composite materials have hardness, rigidity, fatigue strength,
flexural strength, modulus of rigidity, etc. FSW is very
suitable for the composite material. The heat is generated
through the translation rotating of a non-consumable tool
which increases the temperature of material and leads to a
fine grain structure being produced in the weld area which
raises the mechanical strength of the material. During FSW
process at the faying surface the advancing side from where
material starts melting and the other is the retreating side
where material gets cooled. Material flow path also possess
the responsibility for better mixing of material. However,
attentive choices of welding parameters were required for
enhancing the microstructural and mechanical properties.
During the joining of soft materials like aluminium alloys,
FSW becomes the first priority compared with any other
fusion welding process as it has other environmental
benefits. The illustration of FSW process is depicted in
Figure 1. It was initially developed for only aluminium
alloys but with the glimpse of time it becomes suitable for
14
joining a large number of materials. In friction stir welding,
a rotating cylindrical tool with respective pin geometry
is plunged into the spindle and contacts it with the upper
surface of the workpiece. With this process, heat is generated
due to friction and visco-elastic dissipation of mechanical
energy at high strain rates which softens the material and
produces the weld. The tool is high wear resistant and when
it becomes in contact with workpiece metal, it produces
friction heat. Due to this, the workpiece reached a high
temperature which softened the material and made solid
phase connection between two parts. But initially the tool
materials couldn’t able to resist the high temperature such as
steels and other high-strength materials and failure occurred.
Advancement in technology made it a better strength of
material which comes with tungsten, rehenium, ceramics
and polycrystalline cubic boron nitride. The study of the
major influencing parameters of welding and tool design
has been carried out. Also, the impact of these parameters
on mechanical and microstructure properties has been
discussed. The comparison of friction stir welding and other
arc welding processes has been attempted.
FIGURE 1. Illustration of Friction Stir Welding (adapted from Elatharasan et al. 2020)
LITERATURE REVIEW
Reported the flow of shear layer and deposition of them into
the cavity at the end of pin. As from the welded sample,
two small defects can be seen which were due to insufficient
shoulder flow in the upper weld. The shear zone was made
to start from the advancing side and end at the retreating
side where the material is deposited to form the nugget zone.
They conclude that the cavity made in the advancing side
was stable and filled continuously when the pin is continuing
to move forward in the front side (Chen et al. 2008). Studied
the asymmetric mechanical and tensile properties of
AA5083 during friction stir welding joints. The asymmetry
of microstructure can be seen from the results as from
stirred zone to thermo-mechanically affected zone, the ring
was clearly seen at the advancing side but decreased when
going towards weld center. They concluded that because of
root flow, the FSW was fractured through the retreating side
(Rao et al. 2013). Trying to show the influence of multi-pass
friction stir welding on various properties of AA6082. With
the increase in number of passes, the dynamic crystallization
in the stirred zone which leads to equiaxed grains at FSP,
also increased. While increase in the feed rate would not
affect more but reduces the particle size and increases the
mean hardness and tensile strength. They concluded that if
the rotation speed were increased, the coarse grain in the
stirred zone could be seen while change in hardness and
other mechanical effects would inconsiderable (Rayer et
al. 2012). Worked upon commercial 7075-T6 aluminium
alloy and explored the grain refinement, thermal stability
and thermal properties. When the material was annealed to
the temperature 623K to 773K, the grain refinement was
fine but going above 773K temperature range, it leads to an
abnormal grain growth with large grain size. The superplastic
behavior can also be seen where strain hardening takes place
at the initial deformation where it increases due to decrease
in temperature. They conclude that the same alloy while
respected to friction stir processing reveals the maximum
elongation due to variation in experimental conditions
which can also influence the fine-grained microstructure
(Goloborodko et al. 2004). Investigates the effect of different
process parameters using dissimilar AA5085 and AA 6082
aluminium alloy. By using neutron and synchrotron X-ray
diffraction, they found that the maximum longitudinal stress
is two or three times the transverse direction stress. They
reported that the change in residual stress towards weld line
could be seen which was more influential than change in
transverse speed, which shows that rotation speed would
be more beneficial to optimize the residual stress as shown
in their work (Steuwer et al. 2006). Reviewed and studied
the several researchers and their work study. They study the
different process parameters used by researchers and show
through their work. On the basis of various researchers, they
concluded that FSW still needs more research and scrutiny
15
with influencing the rotational speed, thickness and other
vital parameters which directly affects the welded material
(Abdullah et al. 2017).
Scrutinize the material flow and microstructure of similar
and dissimilar aluminium alloy during friction stir welding.
They found vortex-like structure in similar weld of AA6061
and lamellae on dissimilar AA6061-AA2024 with the three
distinct regions of nugget zone. Mechanically mixed region
(MMR), Stirred-induced plastic region (SPFR) and Unmixed
region (UMR), the weldment is able to sustain high degree
of plastic deformation and goes to recrystallization, which
enhances its hardness. They concluded that a fast rotational
speed gives the more uniform mixture in dissimilar welds
(Ouyang et al. 2002). Explore investigate the microstructural
behavior of two dissimilar aluminium alloy while aligned
them in perpendicular rolling direction during friction stir
welding. Metallurgical analysis shows the fine equiaxed
grains throughout the nugget zone. The HAZ shows the
non-uniform grains with slightly layer size and the hardness
was found to be low with respect to base metal. The joint
of AA2024 and AA7075 dissimilar aluminium alloy shows
better ductility with higher tensile strength. Through SEM
analysis, the ductility behavior shows the typical fracture
surface with very fine grain size (Cavaliere et al. 2006).
Studied the microstructural properties and behavior of
dissimilar AA6061-T6 and AISI 1018 steel with friction
stir welding. The tensile results of both the welded joints
showed the different values for low and high pressure and
suggested that higher pressures were beneficial for better
joint strength. They reported that FeAl is rare in solid-state
processes but while going above 1200ºC, the intermetallic
phase was formed of Fe-rich FeAl and Fe3Al (Taban et
al 2010). Investigates the different regions in the welded
samples of AA7075 using microstructural characterization
of friction stir processed weld. They found that the formation
of new grain was developed due to continuous dynamic
recrystallization (DRX) where in a big amount nuclei were
created and formed grain boundaries. The dynamic recovery
(DRV) creates the sub grains for enhancing the size and
orientation of sub grains boundaries during continuous
DRX. Through overall microstructure evolution, the author
suggested that tool design process parameters and cooling
rate directly puts the effect on final microstructure (Oing Su
et al. 2005). Investigates that on what variation of machine
parameters, the tensile strength does affect while joining
dissimilar AA7075-AA6061 friction stir welds. They used
response surface methodology (RSM) in which statistical
analysis and central composite design were taken and
successfully scrutinized the influence of machine variables
on weldment. The stable joints with defect free weld was
formed with proper clamping design but the joint strength
was slightly lowered. They concluded that the tool design
for tensile strength is the most affecting factor. Overall, from
this study, it was recommended that tapered tool with threads
or flat surface would have achieved better material mixing
and high UTS value as compared to smooth cylindrical pin
(Hassan et al. 2017). Predicted the residual stress in friction
stir welding by finding the calculated data and experimental
measured data and comparing it with the proposed methods.
They obtained the good capability of the welded material
and are equivalent to calculated ones (Buffa et al. 2011).
Predicts the average grain size by using a neutral network
during friction-stir welding. Using the experimental
evidence and numerical prediction, the lap and T-joints were
processed and made strongly joint resistance from process
parameters to find grain size (Fratini et al. 2009). Scrutinize
the dwell phase in friction stir welding and compare it with
experimental data. The recording of applied torque with
two rotational speeds indicates the lower friction rate at
the interface of tool and workpiece (Gemme et al. 2010).
Simulates the material flow using finite element technique
which results in a quasi-linear strain during friction-stir
welding. They concluded that the distribution of equivalent
plastic strain exhibits more at the advancing side and the
material flow at the retreating side is faster in front of the pin
while slower at behind the pin (Zhang et al. 2007). Presents
a thermomechanical model for friction stir welding which
estimates temperature contours, sliding ratio and power
dissipation in the welded coupon. They found that with the
increase in tool rotational velocity, the sliding ratio increases
which elaborates that if it is too high, the flash or local
melting which creates instabilities during welding (Jacquin
et al. 2011). Investigates the joining of dissimilar AA6063
and AA7075 and observe the several welding parameters
like tool rotation, welding speed during friction stir welding.
They concluded that the better weld finish and strong joint
strength can be achieved by using square tool and also
the tensile strength shows the better result at 800 rpm and
900 rpm (Arunprasath et al. 2007). Examine the different
behaviors of friction stir welded butt joints and evaluate the
microstructure of AA6061 and AA063. With the high joint
efficiency, the hardness of AA6063 is higher but the tensile
strength is poor than AA6061. They reported that the grains
were slightly elongated at HAZ with fine cracks for AA6061
(Venkatesha et al. 2014). Trying to develop an empirical
relationship for AA2219 to estimate the tensile strength
during friction stir welding. They concluded that the square
pin profile reveals the best tensile strength by focusing on
welding parameters using ANOVA and design of experiments.
They also shows the defects on aluminium alloys related to
variation in rotational speed. The lower rotational speed of
1450rpm shows pinhole type defect at weld region. Due to
having defects like tunnel, pinhole, micro-void and cracks
in the weld region, the fractured points also dislocated from
lowest hardness zone to defected area. Similarly at high
rotational speed of experimental value 1850rpm, the size of
defect becomes large due to high heat input and becomes
tunnel defect (Elangovan et al. 2008). Trying to estimate
the recent advances in friction-stir welding which includes
the properties, structure and process parameters. They
investigated that there were some uncertain parameters
such as frictional and heat transfer coefficient, extent of slip
which contributes to lack of reliability. They concluded that
the researchers should contrast on cooling rates, geometry
16
of stirred zones and other attributes so that it will become
successful in the entire quantitative knowledge (Nandan et
al. 2008). Trying to approaching the sustainability analysis
of friction stir welding at 5xxx series aluminium alloy. They
used life cycle assessment (LCA) methodology to calculate
the effect of friction welding on environment. At the lowest
parameters i.e. at low rotational speed and feed rate, the
environmental impact index (EII) value found to be lowest.
The mechanical properties of joints makes the conditions
most favorable to EII as according to welding parameters
(Bevilacqua et al. 2017).
IMPACT OF TOOL GEOMETRY AT FRICTION
STIR WELDED JOINT
The design of the tool perceives the vital role in having
a good welding property as it has the ability to improve
quality of weld and welding speed. Figure 2 shows the basic
geometry of a friction welded tool. The tool material should
be high wear resistant, high temperature resistant and strong
enough to have good oxidation. Also the pin design matters
a lot. Many researchers have mentioned in their research
that tapered cylindrical pins give the best mechanical and
microstructural properties as compared to square, rectangle
and triangle pin profiles. The improved tool design will help
to make the joint precisely good and also provide improved
quality. Figure 3 shows the different tool pin profile with
shoulder and pin. The pin of the tool should be considered
to be tapered or conical as due to low thermal conductivity,
the material flow and mixing becomes proper at aluminium
joints.
The tool design plays a very crucial role in terms of weld
quality and achieve better mechanical and microstructural
property. According to most of the researchers, the square
pin profile shows highest hardness and tensile strength
without any defect at 1600rpm out of five profiles, which
proves that different pin profile provides great impact on
both the welding properties. The straight cylindrical pin
profile was the lowest performing profile and creates coarse
granular appearance with uneven surface.
The tool geometry could have been optimized using
several pin profiles and through mechanical testing, it would
become clear that which is suitable for their respective work.
The tool pin profile affects the heat generation, torque and
traversing force during friction welding and also affects the
material flow on Aluminium Alloys.
Using threaded tools, trying to understand the flow path
of material during friction stir welding process. They found
that the deposition of material with unthreaded pins were the
same as of the classical threaded pins as in the upper part
of the advancing side and lower part of the retreating side.
Through their work, they reported that with the increase
in plunge force and rotational speed, the size of the weld
joint first increased and then decreased (Lorrain et al. 2010).
Used two profiles of shoulder to investigate the effect of its
geometry on flow of material during friction stir welding.
The shoulder with cavity made the onion ring structure
around the pin and throughout the plate thickness with
some reduction (Leal et al. 2008). Represents the multiple
optimization by varying the welding parameters like tool
rotation speed, translational speed, etc. during friction stir
welding of two dissimilar aluminium alloy. Due to the
presence of kissing bond and uneven joining of dissimilar
aluminium alloy, the joint fractures from the center line and
shows the low UTS value, when keeping the AA5052-H32
at the advancing side. While using square and triangular pin
geometry, a large amount of plastic deformation was held
due to which formation of stress takes place in localized
strain. This shows that the fracture is at TMAZ and possesses
the configuration of higher strength value of the weld
(Kesharwani et al. 2014). Using thermoplastic material,
specifically high density polypropylene plate to optimize the
process parameters on friction stir welding. With the several
experimentation trials, the best parameters they found were
1000rpm of rotational speed and 10mm/min of feed rate
with 1º of tilt angle and tapered cylindrical as tool pin profile
(Jaiganesh et al. 2014).
FIGURE 2. Illustration of FSW tool (adapted from Elangovan et al. 2008)
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Investigated the impact of tool profile and axial force
on AA6061 of friction stir processing zone. They reported
that from the experimental values of five tool pin profiles,
the square pin profile makes defect free weld at 78kN of
axial force with better surface finish (Elangovan et al.
2008). Used an assisted heating tool for friction welding of
thermoplastics to obtain a better weld surface finish. They
concluded that the assisted tool design provides more heat
and enhances the tensile strength for propylene welded
coupons (Banjare et al. 2017). Trying to optimize the welding
parameter for enhancing the tensile strength of AA6061
during friction-stir welding. They concluded that the values
optimized from Hooke and Jeeves algorithm were closely
same enough as experimental values with the developed
mathematical model (Elangovan et al. 2008). Scrutinize
the friction-stir butt welded joint by using the spindle
motor electric current as a parameter. They found that the
square and conical tool pin profile consumes less power and
provides good tensile strength but as the thickness increases,
the power consumption increases (Kumar et al. 2013). Find
the impact on pin profile and rotational speed on AA2219
with friction stir processing zone. They concluded that
the experiments performed with square pin profile, shows
the best tensile strength and produce defect free FSP zone
(Elangovan et al. 2008). Analyze and scrutinize the erosion
of aluminium alloys as they are the most applicable materials
used in sea applications. They used AA5083 and AA6061
to make dissimilar friction-stir welded joints for observing
the variation in mechanical and microstructural properties.
They found that the grains were equally axed and with the
use of a cylindrical pin, the tensile strength was achieved to
be maximum at 800rpm. As pH value decreases, the erosion
becomes lower from the center of weld and shows that pH
value prevails over another parameter. They also added that
with the help of these outcomes, the essential things were
enlightened as for the use of marine applications (Ramesh
et al. 2020).
Conducted the experiments on different welding
parameters and optimized it for friction welded AA6061
and AA6082 samples. Different types of tool pin profiles
were used for observing the difference between the flow
of material and mixing using the Taguchi array. They
reported from their research that the octagonal pin type of
tool possesses the maximum tensile strength as compared
to others. The threaded and tapered cylindrical type of pin
was inappropriate to make proper mixing which leads to
less hardness and tensile strength. The tensile strength and
hardness was observed between 264MPa to 273 MPa and 77
to 85 µHD respectively (Kumar et al. 2013).
TABLE 1. Various types of tool profile used in friction stir welding process
Sr.
No.
Author
Experimental
Material
Variable Tool Profile
Outcomes
1
Lorrain et al. 2010
AA7076-T6
Straight
and
cylindrical pin
2
Leal et al. 2008
AA518-H111
AA6016-T4
Conical shoulder, Scrolled Reduction, onion ring structure at conical pin less reduction
shoulder
in thickness and provide good mechanical properties
3
Kesharwani et al.
2014
AA5052H32
AA5754-H22
Circular,
triangular
4
Jaiganesh et al.
2014
Polypropylene
Composite
Cylindrical, tapered and At particular parameter, tapered tool profile found to be
grooved cylindrical
optimum
5
Elangovan et al.
2008
AA6061
Straight,
tapered
and Square produces highest pulsating action followed by
threaded cylindrical with triangular pin without any defect
square and triangular
6
Banjare et al. 2017
Polypropylene
Threaded cylindrical
With the preheat, threaded tool makes smooth surface,
proper material mixing
7
Elangovan et al.
2008
AA6061
Square
Square pin profile shows optimum tensile strength with
change in axial force and rotational speed
8
Kumar et al. 2013
AA6063-T6
Square, triangular, circular, Square profile improves flow of material and produces
conical
highest pulses per second at 1000rpm, conical profile also
shows good tensile strength
9
Elangovan et al.
2007
AA2219
Straight, Tapered and
Threaded cylindrical,
triangular, Square
10
Ramesh et al. 2020
AA5083
Taper tool pin, threaded Taper produces maximum hardness while cylindrical pin
and cylindrical pin
provides maximum tensile strength
11
Kumar et al. 2013
AA6061
AA6082
Octagonal, threaded and Maximum deformation due to eight edges of pin, Octagonal
tapered cylindrical
help to provide good surface finish as due to more edges
tapered Tapered cylindrical pin shows less deformation but with
unexpected change in thickness
square
and Square pin shows the maximum mechanical strength
The defect free welded joint was made by square pin profile
due to adequate working of plasticized metal and pulsating
action of pin profile.
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Impact of various types of tools at friction welded joints is shown at Table 1.
FIGURE 3. Different tool profile with shoulder and pin diameter (adapted from Garg et al. 2019)
INFLUENCE OF WELDING PARAMETERS ON FRICTION
STIR WELDED JOINT
The tool rotation and traverse speed have their own
preferences in the field of their outcomes. It proposed how
fast the tool rotates and how quickly it traverses along
the interface. For having efficient and successful welding
cycles, these factors could persist. The tool rotation shows
the variation in tensile strength as if it increases, the weld
temperature becomes high and could variate microstructure.
The flow of heat should be adequate so that it forms a good
weld. So to enhance it, a dwell time and traverse speed is
needed whose variation becomes a good generation in heat
input. Sometimes it is possible that the area ahead of the
tool is so cold that flow of stress becomes high and results
in tool fracture. So it is the responsibility to make a hot
zone which is due to high traverse speed and resulting in
good welding. The plunging depth is a crucial factor which
has its vitality because it is the depth under the surface of
the workpiece at the lowest point of the shoulder of the
tool. It defines the weld quality and creates pressure on
the material. The tool tilt angle shows the enhancement in
mechanical properties as increase in tool tilt angle increases
the welding temperature. The slight tilt is given at the back
of the material so that the welding defect should minimize.
The input parameters in friction stir welding are influential
in the output of fabrication. The shape, size, tool geometry,
plunging depth, rotational speed, dwell time all persist an
importance in having the best outcomes.
Proper Rotational Speed will be required for achieving
the better mechanical properties. Likewise, it shouldn’t be
less than 800rpm which causes inadequate heat generation
while rotational speed more than 1700rpm will cause
turbulence and made pinhole type defect. But overall, high
tensile strength would found at every high rotational speed
as per the experimental values. Similarly lower the welding
speed, heat input will be extreme and can cause tunnel
defect while having the high welding speed results in poor
plasticization of metal. The tool tilt angle must be prior to
be set at 2-4º which affects the weld quality and impact
better at mechanical property. The mixing of material will
be better in this tilt angle.
Shows the impact of different parameters on grain size
and formability in AA5083 aluminium alloy. No cracks
or porosity was visible while observing the cross-section
of weldment and fine equiaxed grains were found in
microstructure testing. They found that for the present alloy,
the hardness increases slightly with the decrease in grain size
in the stirred zone, which occurs due to recrystallization due
to excessive plastic deformation. They concluded that the
ductility can be improved while changes in combination of Rt
and V and with lowering the friction heat flow, the formability
in friction stir weld (Hirata et al. 2007). Investigates the
suitability of friction stir welded but joints of AA2024-T3
and AA7075-T6 aluminium alloy. They found that the weld
strength of the weldment is lower than the base material due
to lesser thickness ratio of dissimilar welds. The grains in
unmixed zones were fine equiaxed which shows that it goes
to dynamic recrystallization. They discussed that the flow of
material through the advancing side to retreating has been
uniform (Avinash et al. 2014). Trying to predict the size of
grain and tensile strength of friction stir welded joints and
to establish the empirical relationship between them. By
using response surface methodology (RSM), they developed
the empirical relationship and identified the vital process
parameters by analyzing the predicted value and actual value
for tensile strength; they found out that with the narrower
confidence interval, the precision rate would become higher
(Rajakumar et al. 2010). Using Taguchi’s technique, trying
to find out the optimized process parameter for joining of
19
AA6061-AA7075 with friction-stir welding. With Taguchi’s
L9 algorithm, they got the better parameters from the
higher tensile strength welded sample. It was also analyzed
from the S/N ratio where “Larger is Better” was desirable.
Through this study, it was recommended that in all aspects,
rotational speed contributes more and is the key feature
for getting the best results. The contribution of different
process parameters such as number of passes and rotating
speed is shown in Figure 4 (Ugrasen et al. 2018). Studied
and investigated the mechanical and thermal behavior while
doing the friction welding on Al-Al, Cu-Cu and Al-Cu
couples. Through a scanning electron microscope, no voids
or defects can be seen which indicates the proper mixing of
aluminium and copper with 800rpm of rotational speed and
60mm/min of feed rate. They found that at low rotational
speed, poor tensile strength can be seen at similar and
dissimilar joints but at the above parameters, the UTS value
of 64.81 N/mm2 would achieve which was good and higher
than other experimental trials. Table 2 describes the several
welding parameters having impact on mechanical properties
of friction welded joints (Rane et al. 2018).
Found through their experimental results that low
rotational speed will be required for thick sheets due to
necessity of lower heat input. Whereas, the welding speed
and axial force was required to be increase in thickness
with increase of aluminium sheets due to the variation in
microstructural grains and joint strength. If the rotational
speed puts too high, coarse grain will form with wormhole type defect. While if welding speed is not sufficient
then it causes lack of fill defect. For better productivity,
6mm to 15mm aluminium sheets would be compatible for
commercial applications which maintains the mechanical
and microstructural properties (Mallieswaran et al. 2021).
Inquired into material flow for the use of plasticine as
an analog in friction-stir welding. They observed the weld
deformation features while comparing at low tool rotational
and feed rates where original interface is clearly perceptible
and little mixing is formed (Liechty et al. 2007).
Scrutinize the microstructural characterization of 304
stainless steel and st37 steel during friction stir welding.
They reported that the st37 became recrystallized at the
stirred zone due to high heat input and shows the large
ferrite grains while the 304SS shows small austenitic grains
when dynamic recrystallization occurred in the stirred zone
(Jafarzadegan et al. 2012).
Trying to make a defect free friction stir weld through
a mathematical model of magnesium alloy. They found that
at high welding speed and constant rotation speed, pores
were made at the welding line. But it was avoided by a
mathematical model with less welding speed and constant
welding pressure (Zhang et al. 2006). Investigates the impact
of different welding parameters on dissimilar welded joints
through various resources such as optical and scanning
electron microscopy and tensile test. The 430 stainless
steel and AA6061 material had been taken for research
study and with friction stir welding the joint were made.
They concluded that the microstructural property variates
highly from the vital parameter tool offset, for those which
have tool offset zero, shows maximum tensile strength
with better joint efficiency. The variation in temperature of
microstructure during welding is shown in the form of graph
at Figure 5 (Zandsalimi et al. 2019).
TABLE 2. Different parameters influenced in friction welded joint
Sr. No.
Authors
Work Material
Influencing Parameters
Outcomes
1
Hirata et al.
2007
AA5083
Rotational and Welding Grain size increased with increase in welding speed and
speed
vice-versa in rotational speed, At lowest speeds, the tensile
strength was at highest
2
Avinash et al.
2014
AA2024T3 and
AA7075-T6
Rotational and traverse At rotational 1450rpm and traverse 82mm/min, highest
speed
strength of 262MPa was achieved, at low rotation, the grains
were large and elongated
3
Rajakumar et
al. 2010
AA6061-T6
Axial force, Rotational Increase in grain size occurs in fall of tensile strength, at 95%
and welding speed, tool CI the highest 2tensile strength obtained was 199MPa and
lowest was 195MPa
pin profile
4
Ugrasen et al.
2018
AA6061 and
AA7075
Number of welding
passes, welding and tool
rotational speed
At midrange of rotational with single pass, exhibits the
higher tensile of 110MPa, S/N ratio shows the optimum
range of parameters which was 650 to 850rpm, The hardness
shows maximum at low rpm
5
Rane et al.
2018
Aluminium and
Copper
Cylindrical tool,
transverse speed, tool
speed
At lowest and highest rpm the sample become failed, the
optimum range of parameter were found to be 850 to 1100
rpm which show 146MPa of strength, Lower the feed rate
smooth the surface
6
Mallieswaran
et al. 2021
AA5083 and
AA6082
Tapered cylindrical, Flat Different thickness sheets were tested by source of strength,
cylindrical
hardness and fractographs. The 3mm sheets sustains the
higher load with a tapered pin profile, heat input required to
be high for thick sheets.
(Al-Mg-Si)
continue ...
20
... continued
7
Liechty et al.
2007
Non-Sulphurated Threaded pin, Smooth
Plasticine (NSP), Pin
Roma Plasticine
8
Jafarzadegan
et al. 2012
304SS and St37
Steel
Tilt angle, welding speed Due to high heat input of increased tool rotation, the area
of stirred zone increase, Onion rings were made due to
increased grain size at aluminium, higher rpm shows higher
tensile strength and hardness
9
Zhang et al.
2006
AZ31 (3% Al.
Varying welding speed To avoid the voids and defects, the welding speed was kept
with same rotational to be constant with larger value of tool rotaion and welding
speed
pressure. Pore was produced when welding and rotational
speed were kept at constant
10
Zandsalimi et
al. 2019
430SS and
AA6061
Tool offset, Rotational For optimization, the main influencing parameter was tool
speed
offset. With the increased heat input, the thickness becomes
increased, steel parts becomes micro crack
11
Kranthi et al.
2021
AA5083 and
AA6061
Feed, Rotational
speed
and 1% Zn.)
Through thermal testing and compression testing, the
qualitative flow of stress was found during FSW which was
similar to metals.
tool At high tool rotation, the temperature increases and thus the
width of the stirred zone increases. At mid rpm, the highest
tensile was achieved 198MPa. At high rpm, the ring becomes
small without any corrosion factor
FIGURE 4. Contribution of process parameters (adapted from Ugrasen et al. 2018)
FIGURE 5. Observations from Jafarzadegan et al. 2012 which shows the temperature of various microstructures.
21
The steel shows the micro voids which have lower
hardness. This occurs due to the heat treated condition of
aluminium and steel. It shows that at interface, the hardness
at HAZ is lower than that of aluminium and faces the negative
impact of micro voids. Trying to highlight the influence of
process parameters on mechanical property and material
flow by using dissimilar AA5083-AA6061 material. The
normal tensile test and notch tensile test shows a difference
in strength even at different parameters. The researcher
found that at 1150rpm, the superior tensile strength was
shown to be 198MPa and at the notch test it was at 1450rpm
with joint efficiency 69%. They also observed that the
onion ring layer was decreased at high rpm with improving
corrosion resistance. The microhardness of traverse speed
and rotational speed at dissimilar aluminium alloy is shown
in Figure 6. It depicts the variations in traverse speed and
rotational speed with the outcome of hardness values 84.4
HV and 87.9 HV for AA5083 and AA6061 respectively.
The minimum hardness occurred at HAZ region due to
coarse grain and dissolution of second phase at AA6061.
The average hardness value was shown at higher traverse
speed due to loss of work hardening behavior of AA5083.
While at stirred zone, higher rotational speed shows lower
hardness value due to large grain size and prolonged thermal
exposure (Kranthi et al. 2021.
FIGURE 6. The figure shows the microhardness of AA5083-AA6061 at varying (a) traverse speed and (b) rotational speed respectively
(adapted from Kranthi et al. 2021)
COMPARISON OF FRICTION STIR WELDING TO
OTHER ARC WELDING
For joining the metals, welding is the first preference which
all do as it provides the same strength as of its parent metal
while being used in a diverse variety of applications. Its use
could have occurred in several places from outside premises
on rural farms to inside locations such as manufacturing
laboratories and factories. Friction stir welding (FSW)
has emerged as one of the vital alternative technologies
which has good potential to be used in major industries
like automobiles, aerospace, shipbuilding and can be used
in high strength alloys. The materials being light in weight
like aluminum, magnesium, etc. can be frequently used
in transport and other industries. As the tool rotates and
moves along the workpiece with the joining of plates, the
softened material would extrude around the tool. The heat
generated in the joint area is typically about 80-90% of the
melting temperature. Gas tungsten arc welding is a type of
arc welding in which a tungsten electrode is used to produce
the heat and weld the two metal pieces. The electrode is
non-consumable in nature. The welding torch for GTAW is
greatly designed for manual and automatic torch is, manual
torch consists of the handle from the centerline which consist
of tungsten electrode to variate. Friction welds possess
more joint strength and superior in microstructural grains
as compare to GTAW and GMAW. The comparison done by
researcher shows the 38% reduction in the tensile strength
of GTAW welded joints while the FSW performs highest
tensile strength and yield strength. In terms of hardness,
GTAW also becomes low from FSW as due to improper
welding heat input and usage of lower hardness filler metal.
Also the presence of Silicon contaminates the welded joints
and hence reduces the hardness in GTAW welded joint.
Gas metal arc welding (GMAW) is a process in which a
consumable electrode is used and through the electric power
22
supply, an arc is generated between electrode and workpiece
which melts the metal and causes it to join. But in most of
the conditions, if we compare friction welding from arc
welding above regarding the mechanical and microstructure
property, the friction becomes more suitable and optimum as
the heat generation during welding is low and balanced. Due
to high heat input in GTAW and GMAW, there will be more
chances of making defects with low mechanical strength.
Scrutinize and try to find out the variation in fatigue
strength of friction-stir welds altered by welding speed.
The researcher found that the friction welded aluminium
alloy shows higher pulse rate than arc welds with higher
ductility. As due to high heat input, the material becomes
less sensitive and shows better mechanical properties. They
concluded that the TIG and MIG welds don’t show better
fatigue strength than Al-Mg-Si 6082 alloy which were
independent of welding speed (Ericsson et al. 2003). Trying
to show the variation in tensile strength of AA6061 while
effecting the welding process on aluminium joints and to
compare the arc welding with friction-stir welding. In their
research study, they used AA4043 filler grade for the gas
metal arc welding. Through their research, it is clearly
shown that the superior tensile strength at friction welded
specimen was 295MPa. They found that the joint efficiency
of friction welded samples is 74% while it was 49% and
63% for metal inert gas and tungsten inert gas welded joints
respectively. Also, the hardness shown is more for frictionstir as the motion of the tool generates high shear stress and
is made of very fine grain structure (Lakshminarayan et al.
2009).
TABLE 3. Comparison of Friction welding to GTAW and GMAW
Sr. No.
Author
Work Material
Influencing Parameters
Conclusions Made
Ericsson et al.
2003
AA6082
2
Laksminarayanan
et al. 2009
AA6061, AA4043
Shoulder and pin diameter, Higher tensile strength shown by FS weld which
rotational and welding speed, was 249MPa with 86VHN hardness. Due to fast
axial force, pulsating current heating and cooling at GTAW, dendritic structure
was formed
3
Kulekci et al.
2010
AA6061-T6
Tilt angle, tool speed and Less the heat input, smaller the impact at areas
transverse speed, voltage
where hardness varies. Due to less HAZ at GMAW,
the mechanical properties were low compared to
FSW. FSW made the quality welds
Balasubramanian
et al. 2011
AA2219-T87
1
4
(Al-Si-Mg-Mn)
filler material
(Al-Mg-Si-Cu),
AA4145 filler
material
Axial force, welding speed, The FS weld shows high tensile strength followed by
rotational speed, depth of TIG. The alloy with T4 aged high shows a maximum
penetration
of 291MPa tensile strength. At low welding speed,
the flow and mixing of material become adequate
Gas flow rate, current, FSW shows the joint efficiency of 73% with 243MPa
voltage, tool speed, Threaded of tensile strength which was higher than the other
pin tool, axial force,
two. Fine equiaxed grains were made
Scrutinize the comparison of variation of mechanical
properties to gas metal arc welding and friction-stir welding
at welded joints of material EN AA6061-T6. For the
experimental runs of friction-stir, the semiautomatic milling
machine is used while for metal inert gas, it was MIG-350
semiautomatic. They found that the welded samples were
broken from heat affected zones for friction and showed
the maximum tensile strength of 270MPa but the strength
decreased for metal arc welding for about 23%. The
microstructure shows the rough surface for MIG specimen
and fine grains at friction sample. Overall, the heat generation
and balancing at friction stir is the superior quality which
enhances its mechanical properties (Kulekci et al. 2010).
Worked upon AA2219 to make butt joints and studied the
impact of gas tungsten arc welding, electron beam welding
and friction-stir welding on mechanical properties of
aluminium alloy. They used individually welding machines
for the related welding processes. In their research study,
they found that the friction-stir shows the highest tensile
strength of 343MPa which shows the lowest reduction from
base metal. The maximum reduction of 50% was shown by
tungsten inert gas welding joints with 243MPa (Malarvizhi
et al. 2011). Pointing towards the joint efficiency, friction
stir specimen shows 73% which is highest in class. The
microstructure study of welded specimens shows fine
equiaxed grains due to consistently recrystallization caused
by the heating process.
CASE STUDIES OF FRICTION STIR WELDING
Investigates the suitability of processing the tailor welded
blanks during friction-stir welding. The joints were created
by phase transformation and undesirable changes in
microstructure could be seen. They reported that with the
increase in the thickness ratio, the increase in temperature
would be seen near the HAZ area on the advancing side
(Buffa et al. 2006). Scrutinize and try to show the influence
of friction-stir welding on AA7075. They concluded that
a nugget zone with 2-4µm grain size was shown when
23
recrystallized and concentric flow lines were observed
(Rhodes et al. 1996). Trying to show the impact on tensile
strength of different welding parameters at pulsed current
tungsten inert gas at AA6061. The basic influencing
parameters which the researcher used were peak current,
pulse on time, pulse frequency and base current. From
their experimental work and calculations, they came to the
conclusion that tensile property variates according to peak
current and pulse frequency and they are indirectly related,
if one increases then other also increases or vice-versa.
However, it is totally polar for other parameters i.e. for base
current and pulse on time, they have an inverse relation to
tensile properties which was noticed by researcher (Kumar
et al. 2007). The case studies of several researchers at
friction stir welding and other processes are shown at Table
4. The various zones at macrostructure made during friction
stir welding are shown in Figure 7.
TABLE 4. Case study of various researcher about influencing parameter used during friction stir welding
Sr.
No.
Author
Experimental
Material
Different parameters
used at welding
1
Buffa et al. 2006
AA7075-T6, H13
2
Rhodes et al.
1996
AA7075-T6,
Tool design, travel speed, At weld nugget, the density of dislocating the parent
tool rotation speed
metal was very low. The grains would be recrystallized
3
Kumar et al.
2007
AA6061-T6 and
AA4043 weld metal
Pulsed current, voltage, The pulsed current enhances the tensile strength and
non-consumable filler
aluminium was broken from the weld region. Hardness
also comes more than continuous current.
4
Ramaswamy et
al. 2020
AA6061-T6, ER4043
Filler wire, current, wire Due to pulsating current, hardness exhibits more. The
feed, frequency, welding range was between 76 to 250A with 150 HZ. The tensile
speed
strength was improved by 15%
Cylindrical pin, tool
steel for tool material rotation and welding
speed
Thickness 6.4mm
as filler with 1.2mm
diameter, Thickness
was 3mm
Observations
Poor material flow and mixing due to the thick plate at
the advancing side. Due to large value of nutting angle,
the mechanical strength of joint become less
5
Gomathisankar et AA6061-T6 square
Dwell time, tilt angle, The hardness and tensile strength was achieved to be
al. 2018
plate with 6mm thick rotational and welding 44VHN and 229MPa with most influencing parameter
speed
welding speed
6
Devaiah et al.
2017
AA5083-H321 and
AA6061-T6 with
Taper cylindrical threaded With the macrographs, some dimples were found which
tool, tilt angle, welding were due to plastic deformation. Higher tensile strength
and tool speed
at midrange of rotational speed welding speed. Slow
speed shows the reduction at mechanical properties
7
Elatharasan et al.
2020
AA6061-T6 and
AA5083-H111
Transverse speed,
pentagon, polygon, and
cylindrical pin profile,
rotational speed
At 1250rpm, the tensile strength shows better joint
strength. At 95% certainty level, the influencing
parameter shows the efficient strength
8
Akinlabi et al.
2012
AA5754 and C11000
Rotational speed, feed
rate, threaded pin
Onion rings were found at lower rpm and feed. The
micro voids were present at lower rpm due to insufficient
heating
9
Devaiah et al.
2018
AA5083 and AA6061
Tilt angle, welding
speed, tapered threaded
cylindrical tool
The most influencing parameter was rotation speed
which gives 63% of contribution. The optimum
parameter range was between 1000 to 1200rpm with
80mm/min feed
10
Moreira et al.
2009
AA6061-T6 and
AA6082-T6
Travel speed, tilt angle Due to some impurities involved in aluminium, more
of 2.5º, M5 threaded pin flash was generated and lower the value of hardness.
tool, gage length
The dissimilar joint produce 64% of joint efficiency
5mm thickness
copper
24
FIGURE 7. Macrostructure observation shown from Moreira et al. 2009 of friction welded joints of (a) AA6082-T6, (b) AA6061-T6 and
(c) dissimilar weld.
Ramaswamy et al. [51] describes the impact of different
parameters on the mechanical properties of AA6061-T6
during gas metal arc welding. The thickness of material was
kept to be thin and the parameters were constant current,
pulsed current, cold metal and pulsed cold metal transfer
taken. Through their research study, they found the 15%
growth in tensile strength at pulsed core metal transfer
(PCMT) parameter while low in constant current variant. The
hardness is also recorded to be highest for pure-cold metal
transfer at weld metal and HAZ. This caused the narrow
zones at the advancing side and retreating side as compared
to other joints. Used complex proportional assessment
(COPRAS) for optimizing the best welded parameters which
enhances the mechanical property of AA6061-T6 during
friction-stir welding. After determining and evaluating the
optimum parameters using COPRAS and ANOVA, they reach
a conclusion with different mechanical properties. They
said that the most remarkable parameter which influences
heavily on properties is welding speed as it varies the heat
generation and recrystallization. The actual data of optimum
level were rotational speed at 460rpm, welding speed at
25mm/min, dwell time at 2 min and tool tilt angle of 1.5º
(Gomathisankar et al. 2018).
Using tapered threaded cylindrical pin profile, author
was trying to find out the impact of welding speed at
dissimilar AA5083 and AA6061 welded joint properties.
With the 5mm of thickness, friction stir welding was used
as due to thermal diffusivity and high heat generation, the
fusion process doesn’t able to achieve such mechanical
properties. Though their research study observed that
increasing the welding speed at limit, better weld quality
could be achievable. They also added that at 1140 rpm, the
fine grains at microstructure and higher tensile strength
was accomplished and hence the best parameter with weld
speed 80mm/min at tilt angle 2.6º (Devaiah et al. 2017).
With improvising grey relation analysis, trying to find out
the optimum parameters as joining the different alloys of
aluminium where one is heat treated and other is not. Using
ANOVA technique, response surface method, the properties
of the welded joint of AA6061 and AA5083 were observed
doing friction stir welding. With the 95% confidence level at
regression analysis, they came to the result that the highest
and lowest tensile strength was achieved by threaded
cylindrical and hexagonal pins respectively. For, different
pin profile the ANOVA shows 95% of certainty level and
with GRA the optimized parameters were selected and come
with great output (Elatharasan et al. 2020). Scrutinize the
characterization of dissimilar material to be joined by friction
welding which are AA5754 and C11000 copper. With the
scanning electron microscopy, the welded joints at different
parameters were observed. From their research study, they
found the reduction in thickness at 650rpm at different feeds,
but at high feed of 340mm/min, large voids as defects were
shown which resulted in low material mixing. When the
analysis of 1200rpm was taken, no reduction in thickness
with good material mixing was found. They concluded
that at highest feed, no joints were fused and showed the
maximum number of voids with low-material mixing
(Akinlabi et al. 2012). Using Taguchi, trying to optimize the
process parameter at friction stir welded dissimilar joints of
AA5083 and AA6061. As per using the L9 array of Taguchi
and optimization technique of ANOVA, the significant role
of each parameter was observed. After the confirmation
test to the welded sample, the researcher concluded that the
value observed of yield strength has become approximated
to predicted value which was 213MPa. They said that the
parameter rotation speed sustains the most influencing
parameter followed by traverse speed (Devaiah et al. 2018).
Scrutinize the characterization of welding properties
of dissimilar friction welded AA6061-T6 and AA6082-T6
25
aluminium alloys. The two different alloys were made and
tested on different parameters for analyzing the strength,
grains and various aspects of testing. The researcher
observed that the AA6082 shows lower strength and
hardness as compared to others. The intermediate zone
shows the proper mixing of material at the nugget zone. The
load sustain capability of AA6061 would always be shown
from the results due to higher tensile strength and less plastic
deformation (Moreira et al. 2009).
Through their experimental work, trying to observe the
impact in macro and microstructure of different welding
parameters at friction welded joints of AA7075-T6 and
AA6061-T6. The researcher used different pin profiles
for comparing the fusion between two plates at the same
parameters. They found the tapered cylindrical profile to
be superior as it provides approximate fusion and gives
206MPa of tensile strength. The microstructure reveals
the fine equiaxed grains at nugget zone for AA6061 while
AA7075 shows the rolling flow along the direction of the
tool (Ravikumar et al. 2014). Trying to achieve the peak
tensile strength through the optimization of tool parameters
and friction stir welded joints in AA7075-T6. Through
their experiments, attempts have been made to analyze the
relationship between process and tool parameters with the
help of regression analysis and ANOVA technique. From their
observations, the researcher concluded that the tool rotation
speed is the most sensitive parameter as compared to others
and exhibits higher strength of 376MPa at 1440rpm. They
explained that material which has lower in strength should
be welded at higher rotation speed unless it will result in
the tensile strength to lowest Rajakumar et al. 2010). Took
a 7mm thickness of AA6063 plate through which they
tried to optimize the welding parameters at friction stir
welding. With the use of scanning electron microscopy
testing Taguchi method, they analyze the distribution of
composites and precipitates made and to compare with
the base material composition. They concluded from their
research study that the optimum parameter was axial force
which contributes 49% of the total through which the
maximum tensile achieved is 102MPa with 41 S/N ratio
(Ganapathy et al. 2017).
Analyze the effect of tool heating on the friction
welded aluminium joint. Different types of pin profile
such as cylindrical tapered, square, cylindrical with full
thread were used to define the changes in mechanical and
microstructural properties of dissimilar AA6061-T6 and
AA7075-T651 joints. From their research study, they found
that the threaded with intermittent flat surface and full thread
perceives the highest axial force and the tunnel defects were
also minimized. There was improvement in microhardness
as adequate mixing of material was there in the stirred
zone (Garg et al. 2019). Trying to find out the influencing
parameters in the friction welding of copper and AA6061-T6.
The design of tool pin profile kept to be threaded cylindrical
and welding parameters were tilt angle, rotational speed,
tool offset to analyze the impact on mechanical properties.
They found that if we increase the tool pin offset from low
to high, the axial load decreases due to the pin displacement
towards the aluminium side. They concluded that the taper
tool was not acceptable for the dissimilar welding of copper
and alloy due to not proper mixing of material at the nugget
zone. They observed that the joint strength becomes reduced
due to the presence of intermetallic compounds at stirred
zone (Mehta et al. 2015).
There are several challenges associated with Friction
Welding. Without the adequate heat input there could be
chance of marking cracks and porosities inside of weld
which can directly reduce the fatigue life. Remedies would
be the use of chemical ingredients which prevents local
melting and provides better control. However, they found
the challenges for the detection of weld defects. They told
that with the crucial welding parameters, plunging force
should also be considered to a nominated value which
makes a defect free weld (Wahab et al. 2019).
As per the section 5 of this manuscript, it was studied
that how researchers found the friction welding to be
superior from other arc welding. However, the benefits
of friction welding is the welding nature as it provides
fine, equiaxed grains with uniformly distribution without
generating excessive heat. Also, it prevents from harmful
emission of gases and light. Friction is now priorly used
in aerospace, marine and transportation industries over arc
welding, where aluminium is the most preferable material.
Trying to observe the microstructure variation on
dissimilar AA6061 andAA7075 during friction stir welding.
With the using of K-type thermocouple, they measured
the temperature at six different positions and optimize the
result. The microstructure at nugget zone shows the fine
grains towards AA7075, hence grain density and strength
becomes high as compare to AA6061. As per the temperature
measurement, third position at 4.6mm penetration provides
maximum temperature at advancing side (Godhami et al.
2019).
With near net shape forming technique trying to went
through the development done at friction stir processing.
Mechanical properties of superplastic forming and different
variables such as tool rotation, travel speed, tool geometry
and multiple pass were optimized. Due to breaking of
secondary phase particles, a fine and without porosity
processed aluminium as well as magnesium alloy was found
which enhanced its mechanical properties. The multi-pass
also impacts the mechanical properties (Patel et al 2019).
Analyze the temperature distribution at AA2014
experimentally and statistically during friction stir welding.
With using various welding parameters such as tool rotation,
welding speed, tilt angle the temperature were analyzed at
eight different positions by using K-type thermocouples.
Through experimental values, the ratio of tool rotation
and welding (N/v) is directly depends on temperature i.e.
with increasing the N/v ratio, temperature increases. The
temperature at advancing side would founded to be higher
due to the initial heat input. They found the most vital
welding parameters as tool tilt angle through statistically
analysis (Chaudhary et al. 2019).
26
CONCLUSION
The numerous studies regarding the tool design, welding
parameters, comparison of FSW with arc welding process
and several case studies, the following important conclusions
are made:
1. The influence of tool geometry shows the great
impact at mechanical and microstructure properties.
Several researcher in their study shows the square pin
profile which exhibits higher tensile strength and less
deformation.
2. Several literature survey has been done in this study from
various researchers with different experimental values
and parameters. The outcomes and recommendation
have been insert and preferred in this review paper.
3. Welding parameters play a significant role for perfectly
joining a similar or dissimilar weld. Through this
study, it has been concluded that the rotational speed
will be the supreme welding parameter which possess
the capability to change microstructure grains and
mechanical strength. Welding speed also has a major
role with different tool pin profile and tool tilt angle.
4. Many investigations have been carried out to compare
the FSW and other arc welding processes and therefore
it is considered to show the conclusion of various
researcher in the prescribed format. Due to adequate
heat supply during welding, the microstructural and
mechanical properties are superior in FSW joints.
5. FSW is not only limited to aluminium alloys. Friction
welding can also be applied to weld the stainless steel
material and copper alloys. Through case studies, it is
clear that dissimilar joint of aluminium with copper and
steel can be frictionally welded.
ACKNOWLEDGEMENT
This work was supported by the AKGEC, Ghaziabad, Uttar
Pradesh.
DECLARATION OF COMPETING INTEREST
None
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