Friction Stir.Welding is an advance metal joining process: A Review

Umasankar Das Int. Journal of Engineering Research and Applications www.ijera.com
ISSN: 2248-9622, Vol. 5, Issue 9, (Part - 3) September 2015, pp.10-18
www.ijera.com 10 | P a g e
Friction Stir.Welding is an advance metal joining process: A
Review
Umasankar Das, Dr. Vijay Toppo
Research Scholar, Department of Manufacturing Engineering National Institute of Foundry and Forge
Technology Hatia, Ranchi, India
Associate Professor, Department of Manufacturing Engineering National Institute of Foundry and Forge
Technology Hatia, Ranchi, India
Abstract
The friction stir welding is recently developed solid state welding process which overcome the problem
associated with fusion welding technology. The properties achieved by friction stir welding is better than that
achieve by fusion welding technique It has been invented as a solid-state joining technique and initially applied
to aluminum alloys. FSW is used to replace rivets joints in the aeronautical industry. Recently the aircraft and
military industries widely have been using aluminum alloys particularly because of their fine strength to weight
ratio. However in compare with steels they represent welding difficulties and also lower ductility. In last years it
has been observed that Friction Stir Welding (FSW) method represents better microstructure and mechanical
properties than conventional methods in welding aluminum alloys. It has been widely investigated for mostly
low melting materials, such as Al, Mg and Cu alloys. Aluminum is the most usable material in engineering
application and a lot of improvement is needed in the area of its welding. The latest works on friction stir
welding of aluminum have been directed towards improving the quality of weld, reducing defects and applying
the process of FSW to aluminum for specific applications. This joining technique is energy efficient,
environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys
and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the
most significant development in metal joining in a last decade. The FSW of Aluminums and its alloys has been
commercialized; and recent interest is focused on joining dissimilar materials. However, in order to
commercialize the process, research studies are required to characterize and establish proper process parameters
for FSW. This paper summarizes the trends and advances of this welding processes in the field of welding.
Future aspects of the study are also discussed.
Keywords— FSW, Aluminium alloys , process parameters, tool rotation, transverse speed, tool design,
mechanical properties, tensile strength, hardness, microstructure properties.
I. INTRODUCTION
Friction stir welding (FSW) is a solid-state
joining technique that has expanded rapidly since its
development by Mr. Wayne Thomas in 1991 at TWI
(The Welding Institute) and has found applications in
a wide variety of industries, including aerospace,
automotive, railway, and maritime. The FSW process
exhibits a number of attractive advantages when
compared to other welding processes, perhaps the
most significant of which is the ability to weld alloys
that are difficult or impossible to weld using fusion
welding techniques. The FSW process takes place in
the solid-phase, at temperatures below the melting
point of the material, and as a result does not
experience problems related to re-solidification such
as the formation of second phases, porosity,
embrittlement and cracking. In addition, the lower
temperature of the process enables joining with lower
distortion and lower residual stresses.FSW is also an
energy efficient process that requires no filler material
and, in most cases, does not require the use of a
Shielding gas. Furthermore, the process lacks the
fumes, arc flash, spatter, and pollution associated with
most fusion welding techniques. For these and many
other reasons, FSW has become an attractive joining
process for many manufacturers. [1] Friction stir
welding of aluminium is now a mature and robust
process, which is becoming increasingly well
established in the fabrication of critical components. It
is true to say that FSW has extended the use of
welding in certain materials and applications, in
particular in the welding of 2xxx and 7xxx alloys for
the aerospace industry. The qualities making the
process attractive include reduced cost, minimal repair
requirement, good properties and total automation
leading to a high level of consistency. At the present
time, FSW can compete with other welding processes
for quality of welds and performance. It should be
noted that FSW is still relatively new, and has been in
commercial production for less than 15 years. As with
fusion welding, FSW is basically a thermal process.
Temperatures reached (typically around 500°C) are
RESEARCH ARTICLE OPEN ACCESS

sufficient to cause major micro structural changes in
precipitation hardened or work hardened alloys.
Unlike fusion processes, FSW also involves extremely
high shear strains and strain rates, which will have a
profound influence on the development of
microstructures. Friction stir welding is already one of
the most energy efficient processes available,
although improved process developments (in
particular better tool designs) will no doubt further
reduce the energy required to make the weld. Now
industry has a welding process that can provide high
quality and defect free welds in the high strength 2xxx
and 7xxx alloys, development of improved alloys
which can be welded without loss of properties is
required, and this is a major challenge for the
aluminium producers. [2]
To date, the predominant focus of FSW has been
for welding aluminium alloys, although the process
has been well developed for both copper alloys and
magnesium alloys. Work is under way to develop the
process for materials such as titanium alloys, steels,
nickel alloys and even molybdenum. The welding
process in these materials takes place at considerably
higher temperatures, and although the feasibility of
the process has been demonstrated, further work is
needed to improve the performance and longevity of
tool materials. In addition considerable work has
focused on using FSW to join dissimilar aluminium
alloys. Furthermore the steady push to lightweight
vehicles has largely been responsible for research in
joining aluminium alloys to other metals, including
aluminium to magnesium, aluminium to metal matrix
composites, aluminium to steel and aluminium to
copper. [1]
II. PRINCIPLE OF OPERATION –
FRICTION STIR WELDING
A constantly rotated non consumable cylindrical-
shouldered tool with a profiled nib is transversely fed
at a constant rate into a butt joint between two
clamped pieces of butted material. The nib is slightly
shorter than the weld depth required, with the tool
shoulder riding atop the work surface.
Frictional heat is generated between the wear-
resistant welding components and the work pieces.
This heat, along with that generated by the
mechanical mixing process and the adiabatic heat
within the material, cause the stirred materials to
soften without melting. As the pin is moved forward,
a special profile on its leading face forces plasticised
material to the rear where clamping force assists in a
forged consolidation of the weld. [1]
Fig. .1 Frictional stir welding process [3]
This process of the tool traversing along the weld
line in a plasticised tubular shaft of metal results in
severe solid state deformation involving dynamic re-
crystallization of the base material.
2.1 ADVANTAGES OF FRICTION STIR WELDING THAN
ALL OTHER WELDING PROCESSES [4, 5, 6, 7, AND 8]
 2xxx and 7xxxx series Al-alloys and Al-Li alloy
are easily joined in comparison to conventional
welding process.
 Mechanical properties loss is less because heat
input during process is very less.
 Distortion, shrinkage and residual stress are very
small in this plate.
 Due to solid state welding process, no chance of
occurrence of cracking and porosity is
comparison to conventional fusion welding
process.
 Welding without filler material.
 No need of further process of surface cleaning.
 Typically 1 Km long welding can be achieved
with the same tool.
 It is suitable for automation and robotic
application.
 Improved safety due to the absence of toxic
fumes or the spatter of molten materials.
 Easily automated on simple milling machines,
lower setup costs and less training.
 Can operate in all position (horizontal vertical,
etc.) as there is no weld pool
Table 1. Typical applications in FSW [9]
Industrial
category
Specific
application
Present
process
Advantage of
using FSW
Electrical
Heat–sink
welded
lamination
Gas
metal arc
welding
Higher
density of
fins-better
conductivity
Electrical
Cabinets
and
enclosures
GMAW Reduction
cost, weld
through
corrosion
coating
Aerospace
Floors,
wings and
Rivets Higher
quality,

fuselages. cheaper (no
rivets and
holes)
Rail
industry
Rail car
body,
window,
side wall
and
coupling
gears
GMAC High quality
joints.
Automoti
ve
Wheel rims
and
suspension
arms
GMAW,
MIG
Better joint
integrity
Table .2.Benefits of the FSW process [10].
Metallurgical
benefits
Environment
benefits
Energy benefits
Solid phase
process
No shielding
gas required for
materials with
low melting
temperature
Improved
materials use
Low
distribution
Minimal
surface
cleaning
required
Only 2.5% of
the energy
needed for a
laser weld
No loss of
alloying
element
Eliminates
grinding wastes
Decreased fuel
consumption in
lightweight
aircraft
Multiple parts
joint is replaced
by fasteners
No harmful
emissions
In joint area
mechanical
properties is
good
No consumable
materials
required
Alloying
element loss is
negligible
2.2 Microstructure Classification of weld zone
The first attempt at classifying FSW
microstructures was made by Threadgill. This work
was focused solely on aluminium alloys, and was
limited to features distinguishable by light
microscopy. However, work on other metallic
materials has demonstrated that the behaviour of
aluminium alloys is not typical of most metals and
alloys, and this initial classification was inadequate
[1]. Consequently, a revised set of terms was
suggested and then subsequently revised and adopted
in the American Welding Society Standard D17⋅3M
These micro structural terms are illustrated in Fig 2,
and are defined below along with alternative terms
commonly found in the literature:
1. Unaffected material or parent metal: material
remote from the weld, which has not deformed
and which, although it may have experienced a
thermal cycle from the weld, is not affected by
heat in terms of detectable changes in
microstructure or properties
2. Heat affected zone (HAZ): the region close
enough to the weld for the weld thermal cycle to
have modified the microstructure and/or
properties, but no apparent plastic deformation is
detected by light microscopy although it is
recognised that some plastic deformation will
have occurred, as is typically the case in any
weld HAZ.
3. Thermo mechanically affected zone (TMAZ): in
this region, the material has been plastically
deformed by the FSW tool, and heat from the
processing has also affected the material. In the
case of aluminium, it is possible to generate
considerable plastic strain without
recrystallisation in this region, and there is
generally a distinct boundary, at least at a
macroscopic level, between the recrystallised
and deformed zones of the TMAZ.
4. Stir zone: The stir zone (also nugget,
dynamically recrystallised zone) is a region of
heavily deformed material that roughly
corresponds to the location of the pin during
welding. A unique feature of the stir zone is the
common occurrence of several concentric rings
which has been referred to as an "onion-ring"
structure.
When presenting micrographs it is also
conventional to show the advancing side of welds on
the right
Fig. 2. Micro structural zone classification in a
friction stir weld in Al 2024 alloy (A: parent material,
unaffected by process; B: HAZ, thermally affected
but with no visible plastic deformation; C: TMAZ,
affected by heat and plastic deformation) [1]
2.3 Materials used in FSW:
Frictions stir welding process used in joining many
types of materials and materials combination. TWI
has concentrated most of its efforts to optimizing the
process for the joining of aluminium and its alloy.
 2000 series aluminium alloy (Al-Cu)
 5000 series aluminium (Al-Mg)

 6000 series aluminium (Al-Mg-Si)
 7000 series aluminium (Al-Zn)
 8000 series aluminium (Al-Li)
Continuing development of the FSW tool, its
design and materials have allowed preliminary weld
to be successfully produced in:
 Copper and its alloy
 Lead
 Titanium and its alloy
 Magnesium alloy ,magnesium to aluminium
 Zinc
 MMCs based on aluminium (metal matrix
composite)
 Other aluminium alloy of the 1000
(commercially pure), 3000(Al-Mg) and 4000(Al-
Si) series.
 Plastic
 Mild steel
Single pass butt joint with aluminium alloy have
been made in thickness ranging from 1.2 to 50 mm
without the need for a weld preparation .Thickness of
up to 100 mm can be welded using two passes one
from each side with 6082 aluminium alloy.
Parameters for butt welding of most aluminium
alloys have been optimised, is thickness range from
1.6 to 10 mm. Special lap joining tools have also
been developed for aluminium with thickness of 1.2
to 6.4 [11].
2.4 FSW Tool materials
FSW tools are made by different materials. Tool
is chosen as for the requirement of material to be
welded. Tool materials depend upon the melting
temperature of the materials and the desired
travelling speed.
Table 3 Summary of current friction stir welding tool
materials [12]
2.5 Tool design:
Heat generation, the power required, plastic flow
and the uniformity of the welded joint depend upon
the tool design. Tool geometry such as probe length,
probe shape and shoulder size are key parameters
because it would affect the heat generation and
plastic material flow for welding [13]. Tool is
important part it consist of shoulder and pin. Main
function of tool profile is material flow and in turn
regulates the welding speed of FSW process. Main
function of shoulder is to generate most of heat and
prevents the plasticized materials escaping from the
work piece while both the shoulder and the tool pin
affect the material flow. A tool should perform
following function (i) reduce the welding force, (ii)
enable easier flow of plasticized material, (iii)
facilitate the downward angering effect and (iv)
increase the interface between the pin and the
plasticized material, thereby increasing the heat
generation. Commonly five pin profile i.e. strength,
cylindrical, tapered cylindrical, threaded cylindrical,
triangular and square pin to fabricate the joints, in
FSW as shown in Fig. .3 [13].
Fig.3. Types of tool pin profiles [14].
2.6 Manufacturing of FSW tool:
Manufacturing of five different FSW tools were
made of high carbon high chromium Steel. Different
tool pin profiles of straight square (SS), tapered
square (TS), straight hexagon (SH), straight octagon
(SO) and tapered octagon (TO) without draft were
manufactured using CNC turning centre and wire
cut electrical discharge machining to get accurate
profiles. Each tool had configuration of shoulder
diameter of 18 mm, pin diameter of 6 mm and pin
length of 5.6 mm, and shoulder to work piece
interference surface with 3 concentric
circular equally spaced slots of 2 mm in depth on all
tools. The tools were oil hardened [15]. The image
of manufactured tools is shown in Fig..4.
Alloy Thickness
(mm)
Tool materials
Aluminium
alloy
< 12
< 26
Tool steel, WC-CO
MP159
Magnesium
alloy
< 6 Tool steel ,WC
Copper and
copper alloy
< 50
< 11
Nickel alloy, PCBN,
tungsten alloy Tool
steel
Titanium
alloy
< 6 Tungsten alloy
Stainless
alloy
< 6 PCBN, tungsten
alloy
Low alloy
steel
< 6 Tungsten Carbide
(WC), PCBN

Fig.4. Image of manufacture tool with different tool
profile [15]
III. Important FSW process parameters
3.1 Tool rotation and traverse speeds
There are two tool speeds to be considered in
friction-stir welding; how fast the tool rotates and
how quickly it traverses the interface. These two
parameters have considerable importance and must
be chosen with care to ensure a successful and
efficient welding cycle. The relationship between the
welding speeds and the heat input during welding is
complex but, in general, it can be said that increasing
the rotation speed or decreasing the traverse speed
will result in a hotter weld. In order to produce a
successful weld it is necessary that the material
surrounding the tool is hot enough to enable the
extensive plastic flow required and minimize the
forces acting on the tool. If the material is too cold
then voids or other flaws may be present in the stir
zone and in extreme cases the tool may break
Excessively high heat input, on the other hand may
be detrimental to the final properties of the weld.
Theoretically, this could even result in defects due to
the liquation of low-melting point phases (similar to
liquation cracking in fusion welds). These competing
demands lead onto the concept of a "processing
window": the range of processing parameters viz.
tool rotation and traverse speed that will produce a
good quality weld. Within this window the resulting
weld will have a sufficiently high heat input to ensure
adequate material plasticity but not so high that the
weld properties are excessively deteriorated.[1]
3.2 Tool tilt and plunge depth
The plunge depth is defined as the depth of the
lowest point of the shoulder below the surface of the
welded plate and has been found to be a critical
parameter for ensuring weld quality. Plunging the
shoulder below the plate surface increases the
pressure below the tool and helps ensure adequate
forging of the material at the rear of the tool. Tilting
the tool by 2–4 degrees, such that the rear of the tool
is lower than the front, has been found to assist this
forging process. The plunge depth needs to be
correctly set, both to ensure the necessary downward
pressure is achieved and to ensure that the tool fully
penetrates the weld.
Fig. 5 drawing showing the plunge depth and tilt of
the tool [1]
Given the high loads required, the welding
machine may deflect and so reduce the plunge depth
compared to the nominal setting, which may result in
flaws in the weld. On the other hand, an excessive
plunge depth may result in the pin rubbing on the
backing plate surface or a significant under match of
the weld thickness compared to the base material.
Variable load welders have been developed to
automatically compensate for changes in the tool
displacement. [1]
3.3 Welding forces
A downwards force is necessary to maintain the
position of the tool at or below the material surface.
Some friction-stir welding machines operate under
load control but in many cases the vertical position of
the tool are preset and so the load will vary during
welding. The traverse force acts parallel to the tool
motion and is positive in the traverse direction. Since
this force arises as a result of the resistance of the
material to the motion of the tool it might be
expected that this force will decrease as the
temperature of the material around the tool is
increased. The lateral force may act perpendicular to
the tool traverse direction and is defined here as
positive towards the advancing side of the weld.
Torque is required to rotate the tool, the amount of
which will depend on the down force and friction
coefficient (sliding friction) and/or the flow strength
of the material in the surrounding region. In order to
prevent tool fracture and to minimize excessive wear
and tear on the tool and associated machinery, the
welding cycle is modified so that the forces acting on
the tool are as low as possible and abrupt changes are
avoided. [1]
3.4 Flow of material
Early work on the mode of material flow around
the tool used inserts of a different alloy, which had a
different contrast to the normal material when viewed
through a microscope, in an effort to determine where
material was moved as the tool passed. The data was
interpreted as representing a form of in-situ extrusion

where the tool, backing plate and cold base material
form the "extrusion chamber" through which the hot,
plasticised material is forced. In this model the
rotation of the tool draws little or no material around
the front of the pin instead the material parts in front
of the pin and passes down either side. After the
material has passed the pin the side pressure exerted
by the "die" forces the material back together and
consolidation of the join occurs as the rear of the tool
shoulder passes overhead and the large down force
forges the material.[1]
3.5 Generation and flow of heat
For any welding process it is, in general,
desirable to increase the travel speed and minimise
the heat input as this will increase productivity and
possibly reduce the impact of welding on the
mechanical properties of the weld. At the same time
it is necessary to ensure that the temperature around
the tool is sufficiently high to permit adequate
material flow and prevent flaws or tool damage.
When the traverse speed is increased, for a given heat
input, there is less time for heat to conduct ahead of
the tool and the thermal gradients are larger. At some
point the speed will be so high that the material ahead
of the tool will be too cold and the flow stress too
high, to permit adequate material movement,
resulting in flaws or tool fracture. If the "hot zone" is
too large then there is scope to increase the traverse
speed and hence productivity. Heat generation during
friction-stir welding arises from two main sources:
friction at the surface of the tool and the deformation
of the material around the tool. The heat generation is
often assumed to occur predominantly under the
shoulder, due to its greater surface area, and to be
equal to the power required to overcome the contact
forces between the tool and the work piece. [1]
Table 4. Main process parameter of FSW process
[16].
Parameter Effect
Welding speed Appearance, heat control
Rotational speed Frictional heat, stirring oxide
layer breaking and mixing of
materials
Tilting angle The appearance of weld
shining
Down force Frictional heat, maintaining
contact condition
IV. Mechanical properties.
Friction stir welding results in a significant
microstructural evolution within and around the
stirred zone ,which change the mechanical properties
,such as hardness ,tensile strength, ductility, residual
stress and fatigue are briefly reviewed.
4.1 Hardness
Many researchers use hardness data as an initial
assessment of mechanical properties. Aluminum
alloys are classified into heat-treatable (precipitation-
hardenable) alloys and non-heat treatable (solid-
solution-hardened) alloys. A number of
investigations established that the change in hardness
in the friction stir welds is different for precipitation-
hardened and solid-solution-hardened aluminum
alloys Many studies on the mechanical properties of
FSW joints aluminum alloys of are available. Xu et
al. [17] showed that in case of friction stir welded
thick 2219-O aluminum alloy, the hardness presents
an asymmetrical distribution through the weld centre
line and the maximum hardness was obtained at the
weld top on the advancing side because of the piling
of materials on advancing side. The weld top was
significantly harder than the weld bottom. Cavaliere
et al. [18] investigated the effect of processing
parameters on the mechanical and metallurgical
properties of dissimilar AA6082-AA2024 joints
produced by friction stir welding. The joints were
produced with different alloy positioned on the
advancing side of the tool. The joints were realized
with a rotation speed of 1600rpm and by changing
the advancing speed from 80 to 115mm/min. It was
reported that the highest value of micro hardness
were reached in the case of dissimilar AA2024-
AA6082 when the 2024 alloy was on the advancing
side of the tool and the welding speed was 115
mm/min. When 6082 alloy was employed on the
advancing side of the tool, the micro hardness profile
in the weld nugget appeared more uniform, indicating
a better mixing of the material. The hardness in the
nugget zone was slightly higher than that in the base
material, and the maximum hardness was located in
the TMAZ. In all the cases of welding, minimum
hardness was reported in the HAZ because of over
aging effect. Bousquet et al. [19] reported that the
AA2024-T351 friction stir welded joint exhibited a
significant micro hardness evolution through the
weld due to modifications in microstructure.
4.2 Strength and Ductility
The welding parameters have a significant effect
on the ductility and strength of friction stir welded
aluminum joints. Rajamanickam et al. [20]
investigated the statistical significance of process
parameters such as tool rotation and weld speed on
thermal history and mechanical properties of
aluminum alloy AA2014. From analysis of tensile
property data of joints, it was concluded that the weld
speed was the main input parameter that had the
highest statistical influence on tensile properties Liu
et al. [21] studied the effect of FSW parameters on
the tensile properties and fracture locations of FSW
2017-T351 aluminum alloy. It was reported that for
revolutionary pitch greater than a definite value,

some void defects exist in the joints, the tensile
properties of the joints were considerably low, and
the joints fractured at the weld centre. Hatamleh [22]
investigated the local tensile properties at the
different regions of the weld of AA 2195 joint
produced by friction stir welding using digital image
correlation technique. Highest tensile properties were
located in the heat affected zone and the lowest in the
weld nugget. More recently Malarvizhi and
Balasubramaniam [23] compared the tensile behavior
of AA2219 joints produced by GTAW, EBW and
FSW. They reported that of the three welded joints,
FSW joints exhibited superior tensile properties
compared to EBW and GTAW joints.
4.3 Residual stress
The residual stresses developed during the
welding can severely affect the fatigue behavior of
the weldments. In order to improve the fatigue life
of the weldments, it becomes essential to understand
residual stresses and methods to moderate them. The
metal flow and the heat generation due to friction
forces is greatly affected by operating parameters
such as the height and the shape of the pin as well as
the shoulder surface of the tool. Furthermore, the
force superimposed on the rotating tool during the
process itself has to be chosen properly since the
generated pressure on the tool shoulder surface and
under the pin end determines the heat generation
during the process. The high thermal input in FSW
can result in tensile residual stresses in the weld
region[24,25] Fratini and Zuccarello [26] examined
the through-thickness residual stresses using the hole-
drilling method that occur on aluminum joints, after
the welding process. Lombard et al. [27] investigated
the effect of varying welding parameters on the
residual stress profiles in friction stir welds of
aluminum alloy AA5083-H321. They reported that
the residual stresses are generally tensile in the weld
region, with balancing compressive stresses in the
parent plate. Fratini et al. [28] determined the
residual stress intensity factor by cut compliance
method in friction stir welds produced in 2024-T351
aluminum lloy. They reported tensile residual stresses
inside the weld with the heat affected zones subjected
to compressive residual stress. Chen and Kovacevic
[29] developed a three-dimensional model based on
finite element method to study the thermal impact
and evolution of the stresses in the weld considering
the effect of the tool.
4.4 Fatigue
It is important to understand the fatigue
characteristics of FSW welds Moreira et al. [30]
investigated the influence of FSW on the fatigue life
of specimens of aluminum alloy 6063-T6, containing
notches in the TMAZ. Both welded and unwelded
notched specimens were fatigue tested under load
control at different stress levels. They further used
strain-based approach to fatigue for life prediction.
Their study revealed the following three important
observations. First, the fatigue life of specimens
containing a notch machined in the material directly
affected by stirring process was higher than the
fatigue life of similar notched specimens of parent
material.
The increase in fatigue life was present at all
stress levels. Second, lower fatigue notch sensitivity
was observed in friction stirred specimens in
comparison to the base material.
Further, surface quality of the FSW weld exerts a
significant effect on the fatigue life. Third, the effect
of FSW parameters on the fatigue strength is
complicated and no consistent trend is available so
far.
4.4 corrosion behavior
Various microstructural zones exhibit different
corrosion susceptibility.it is because FSW exhibit
different microstructural characteristics such as grain
size, precipitate size and texture. Surekha et al. [31]
investigated the effect of processing parameters
(rotation speed and traverse speed) on the corrosion
behavior of friction stir processed high strength
precipitation hardened AA2219-T87 alloy. Corrosion
resistance of friction stir processed alloy was studied
by potentiodynamic polarization, electrochemical
impedance spectroscopy and salt spray and
immersion tests. Anodic polarization and
electrochemical impedance tests in 3.5% NaCl
showed an improved corrosion resistance of the
processed alloy, which increased with the number of
passes. Salt spray and immersion tests also showed
improved resistance to corrosion. The increased
resistance to corrosion was attributed to the
dissolution of CuAl2 particles
V. IMPORTANT PROBLEMS AND
ISSUES TO BE ADDRESSED[32]
Some of the major key problems are discussed
below
 Forming of FSW welds is still challenging due to
the limit formability. The studies on the
relationship between formability and
microstructural stability of FSW joint are rare
 The essential drawback of this technique,
however, is the low stability of the welded
material against abnormal grain growth during
subsequent annealing
 Welding speeds are somewhat slower than those
of some fusion welding processes.
 There is a keyhole at the end of each weld seam.
 The evolution of microstructure and properties of
friction stir welded joints.

So, the attainment of this milestone is well within
the reach of the welding community within the next
ten years.
VI. Outlook and remark
Despite the initial success of FSW, there are still
many challenging problems that need to be overcome
for its fully automated industrial application: the
optimization of parameters, the detection of defects,
and the control of the process. Extensive
experimentation for joining a particular combination
of materials helps in determining the process
parameters for a particular weld setup. Effort has been
concentrated on the modeling of the process in order
to predict the thermo-mechanical conditions, to better
understand the behavior of the workpiece and the
conditions which result in successful weld formation
and the lowering of residual stresses in the weldments.
Process monitoring has been undertaken by capturing
and processing the acoustic emission during welding
for determining the quality of the weld and the status
of the FSW tool (tool wear and tool breakage).
Mechanical and microstructural characterization using
tensile and peel tests, SEM micrographs and electron
probe micro-analysis help in classifying the quality of
the welds [33]In spite of its short history, it has found
widespread applications in diverse industries. Hard
materials such as steel and other important
engineering alloys can now be welded efficiently
using this process. The understanding has been useful
in reducing defects and improving uniformity of weld
properties and, at the same time, expanding the
applicability of FSW to new engineering alloys.
Some conclusions on future work are listed below:
 The future work is to analyses the influence of
the processing parameters on the transition,
plunging and welding stages
 Future work will be to perform the analysis on
other heat treatable and non-heat-treatable
aluminium series. The future work will also be
focused on the investigation of the thermo-
mechanical phenomenon, leading to the
uncharacteristic force and torque behavior, etc
The demand of Aircraft Industries to substitute
the conventional joining technologies with low costs
and high efficient processes such as friction stir
welding is considered as one of the most
encouraging design challenge for the future So, with
better quantitative understanding of the underlying
principles of heat transfer, material flow, tool-work–
piece contact conditions and effects of various
process parameters, efficient tools have been devised.
At the current pace of development, FSW is likely to
be more widely applied in the future[32]
References
[1] http://en.wikipedia.org/wiki/Friction_stir_ w
elding
[2] R P L Threadgill, A J Leonard, H R Shercliff
and P J Withers. Friction stir welding of
aluminium alloys. International Materials
Reviews, vol.54. no.2. March 2009. pp. 49-
93.
[3] K.Rajes B.T. Gibson, D.H. Lammlein, T.J.
Prater, W.R. Longhurst, C.D. Cox, M.C.
Ballun,K.J. Dharmaraj, G.E. Cook, A.M.
Strauss. Friction stir welding: Process,
automation, and control. Journal of
manufacturing process 21 january 2013
[4] Elangovan C.J. Dawes and W.M. Thomas,
“Friction Stir Process Welds Aluminum
Alloys’’, Weld. J., (1996), 75, p 41–45.
[5] Patil H. R.S. Mishra and Z.Y. Ma,’’ Friction
Stir Welding and Processing’’, Mater. Sci.
Eng. R, (2005) 50, p 1–78.
[6] W.M. Thomas, K.I. Johnson, and C.S.
Wiesner, “Friction Stir Welding Recent
Developments in Tool and Process
Technologies,’’Adv. Eng. Mater.( 2003)5, p
485–490.
[7] J. Defalco, “Friction Stir Welding vs. Fusion
Welding’’, Weld. J. (2006)85, p 42–44.
[8] J.W. Arbegast, “Friction Stir Welding’’,
Weld. J.(2006)85, p 28–35.
[9] R.S Mishra and M.W Mahoney,
“Introduction In Friction stir welding and
processing’’, Materials Park Ohio: ASM
International; (2007).
[10] C.J. Dawes and W.M. Thomas, “Friction Stir
Process Welds Aluminum Alloys’’, Weld. J.,
(1996), 75, p 41–45
[11] Stephan Kallee and Dave Nicholas’ “Friction
Stir Welding at TWI”
[12] Rajiv S. Mishra, Murray W. Mahoney,
“Friction Stir Welding and Processing”
[13] S. Gopalakrishnan, N. Murugan, “Prediction
of tensile strength of friction stir welded
aluminium matrix TiC particulate reinforced
composite’’ Materials and Design 32 (2011)
462–467.
[14] K. Elangovan, V. Balasubramanian, S. Babu,
“Predicting tensile strength of friction stir
welded AA6061 aluminium alloy joints by a
mathematical model’’.Materials and Design
30 (2009) 188–193.
[15] R. Palanivel, P. Koshy Mathews,
N.Murugan, “Optimization of process
parameters to maximize ultimate tensile
strength of friction stir welded dissimilar
aluminum alloys using response surface
methodology”.
[16] G.C.Jadhav,R.S.Dalu, “Friction Stir Welding
– Process Parameters and its Variables: A
Review’’
[17] W. Xu, J. Liu, G. Luan, and C. Dong,
“Temperature evolution, microstructure and

mechanical properties of friction stir welded
thick2219-O aluminum alloy joints,”
Materials and Design, vol. 30, pp.3460-
3467, 2008.
[18] P. Cavaliere, D. A. Santis, F. Panella, and A.
Squillace, “Effect of welding parameters on
mechanical and microstructural properties of
dissimilar AA6082-AA2024 joints produced
by friction stir welding,” Materials and
Design, vol. 30, pp. 609-616, 2009.
[19] E. Bousquet, A. Poulon-Quintin, M.
Puiggali, O. Devos, and M. Touzet,
“Relationship between microstructure,
microhardness and corrosion sensitivity of an
AA 2024-T3 friction stir welded joint,”
Corrosion Science, vol. 53, pp. 3026-3034,
2011.
[20] N. Rajamanickam, V. Balusamy, M. G.
Reddy, and K. Natarajan, “Effect of process
parameters on thermal history and
mechanical properties of friction stir welds,”
Materials and Design, vol. 30, pp. 2726-
2731, 2009
[21] H. J. Liu, H. Fujii, M. Maeda, and K. Nogi,
“Tensile properties and fracture locations of
friction-stir-welded joints of 2017-T351
aluminum alloy,” Journal of Materials
Processing Technology, vol. 142, pp. 692-
696, 2003
[22] O. Hatamleh, and A. DeWald, “An
investigation of peening effects on the
residual stresses in friction stir welded 2195
and 7075 aluminum alloy joints,” Journal of
Materials Processing Technology, vol. 209,
no.10, pp. 4822-4829, 2009.
[23] S. Malarvizhi, and V. Balasubramaniam,
“Effect of welding processeson AA2219
aluminium alloy joint properties,” Trans.
Nonferrous Met.Soc. China, vol. 21, pp. 962-
973, 2011.
[24] W. Xu, J. Liu, G. Luan, and C. Dong,
“Temperature evolution, microstructure and
mechanical properties of friction stir welded
thick 2219-O aluminum alloy joints,”
Materials and Design, vol. 30, pp. 3460-
3467, 2008.
[25] G. Pouget, and A. P. Reynolds, Residual
stress and microstructure effects on fatigue
crack growth in AA2050 friction stir welds,”
International Journal of Fatigue, vol. 30, pp.
463-472, 2008.
[26] L. Fratini, and B. Zuccarello, “An analysis of
through-thickness residual stresses in
aluminium FSW butt joints,” International
Journal of Machine Tools & Manufacture,
vol. 46, pp. 611-619, 2006.
[27] H. Lombard, D. G. Hattingh, A. Steuwer,
and M. N. James, “Effect of process
parameters on the residual stresses in
AA5083-H321 friction stir welds,” Materials
Science and Engineering A, vol. 501, pp.
119-124, 2009 .
[28] L. Fratini, S. Pasta, and A. P. Reynolds,
“Fatigue crack growth in 2024- T351 friction
stir welded joints: Longitudinal residual
stress and microstructural effects,”
International Journal of Fatigue, vol. 31, pp.
495-500, 2009.
[29] C. M. Chen, and R. Kovacevic, “Finite
element modeling of friction stir welding –
thermal and thermo mechanical analysis,”
International Journal of Machine Tools &
Manufacture, vol. 43, pp. 1319-1326, 2003
[30] P. M. G. P. Moreira, M. A. V. de Figueiredo,
and P. M. S. T. de Castro, “Fatigue
behaviour of FSW and MIG weldments for
two aluminium alloys,” Theoretical and
Applied Fracture Mechanics, vol. 48, pp.
169- 177, 2007
[31] K. Surekha, B. S. Murty, and K. R. Prasad,
“Effect of processing parameters on the
corrosion behaviour of friction stir processed
AA 2219 aluminium alloy,” Solid State
Sciences, vol. 11, no. 4, pp. 907-917, 2009.
[32] Mandeep Singh Sidhu et.al Friction Stir
Welding – Process and its Variables: A
Review nternational Journal of Emerging
Technology and Advanced Engineering,
Volume 2, Issue 12, December 2012
[33] V. Soundararajan, M. Valant and
R.Kovacevic,Metalurgija-- J ournal of
metallurgy, An over view of R&D work in
friction stir welding at SMU

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