www.ijcrt.

org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

FRICTION STIR WELDING OF ALUMINIUM

FOAM SANDWICH PANELS
1
B.Ashok, 2N.Karthik, 3V.Sravan kumar, 4S.Yerni Vasu Deva, 5P.Ajay Reddy
1,2,3,4,5
B.Tech Final Year Student
1,2,3,4,5
Department of Mechanical Engineering
1,2,3,4,5
Visakha Institute of Engineering and Technology, Visakhapatnam, A.P, India.

Abstract: The friction stir multi-lap welded joint has been created between the sheets of two aluminium
Al5052-H32 alloys and the pure copper foil. The values of the shear strengths in the multi-lap weld of
dissimilar materials, has been evaluated consisting of a sandwich structure. The sheets used are very thin in
terms of thicknesses. The tool material is M2 HSS (High Speed Steel). The design of experiments has been
done by following Taguchi method’s L9 approach. The ultimate shear strength is determined for all the
samples. Microstructure has been evaluated with the scanning electron microscope (SEM) and the optical
microscope for the AlA-Cu-AlA sample found to have the highest ultimate shear strength. Also, micro-hardness
has been found out for the same. The AlA-Cu-AlA weld having the highest ultimate shear strength was made
with the friction stir weld parameters: 800 RPM of tool rotation speed, 5 mm/min of traverse speed & 0.2 mm
of the plunge depth. It was also found that the AlA-AlA weld had higher strength than the AlACu-AlA weld for
the same set of varying parameters. While dealing with the thin sheets, clamping plays a significant role. The
discussed process could be utilised to create the copper cladding over the tubes of aluminium alloys which
would make them light weight and excellent heat sinks.
Index Terms: FSW, Al5052-H32, Copper Foil, Taguchi Method’s and SEM.

I. INTRODUCTION
Before the advent of friction stir welding, when arc fusion welding was in fashion, the defects to welding
ratio was considerably higher. The culprit behind that unfavourable event was the low energy-density fusion
welding process which causes the formation of a large pool molten metal and a large heat affected zone. This
led to the formation of defects that were developed during the weld pool solidification. In return, these defects
led to the distortion of work piece and the welded joint while reducing the strength of the joint as well. Up until
1990s, fusion arc welding and gas welding had been the prevalent players in the welding industry.[1] Not long
before the invention of FSW, certain other non-fusion welding processes such as friction welding, had already
been developed. However, the former non-fusion welding processes could only find a very limited use in the
industrial applications. In the case of friction welding, the two work pieces are made to come in contact with
each other and with the help of linear motion or rotations, relative motion is achieved between them. Along
with the relative motion, there is also simultaneous application of the compressive force along the two work-
pieces. The reason why the geometry of the parts joined by the friction welding is restricted is due to the
availability of only two movements: linear and rotational, which can be utilized to create the relative motion
between the work-pieces. The principle governing the joining process in friction welding is that due to the
relative motion between the two parts that are to be joined, frictional heat is generated. This frictional heat in
turn, causes the softening of the metal at ends of parts in contact. At this semi-plastic softened state, when
pressure is also applied, the two parts make up a strong joint at the surface of contact. Friction welding is very
IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i354
www.ijcrt.org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

much similar to the forming process. Even though there had been geometrical restrictions for the use of friction
welding and difficulties in clamping varying sections, it proved to be an efficient way for creating a firm joint
between metals, plastics and many other polymers as the area of heat affected zone created in friction welding
is very minimal just as in most of other solid state welding processes. This new technology involving the
frictional heat and the pressure also unleashed the possibilities of dissimilar material joining. Fig.1.1 schematic
diagram of friction stir welding process
Another invention that took place during the same period in 1950s when friction welding was prevailing
was the laser welding. Since then and until now the laser welding is considered to be a very convenient and
efficient mode of creating a joint between the multiples.[2] However, laser beam welding also has a few cost
based restrictions and the restrictions cause due the size of parts that are to be joined. In laser beam welding, a
high concentration welding source with high degree of penetration heats up the region in the material to be
joined very precisely. It is a high density joining process and along with accuracy, offers the minimal affected
zone while creating a very thing section of the heat affected zone which is, in some cases, negligible.

Fig.1.1 Schematic Diagram of Friction Stir Welding Process

1.1MATERIALS AND RESEARCH METHODOLOGY

1.1.1 MATERIAL SPECIFICATIONS
There were a total of three different types of materials involved in the experimentation work. One of the
materials made up the tool. Other two materials constituted the sheets to be joined and the foil to be inserted.
1.1.2 MATERIAL OF THE TOOL
The material of the friction stir welding tool was M2 (Molybdenum) HSS (High Speed Steel), also known
as the tool steel and is a standard to be used for the tools, in industry. The M2 HSS tool used for friction stir
welding in this experimentation was used without heat treatment due to the following reasons:
1.) The M2 HSS tool already has a hardness of 60 HRC (Rockwell C Hardness) without the heat treatment
which is much higher than the softer material Al5052-H32, with a Brinell hardness of 60, which is to be
welded.
2.) After annealing, the shocks would prove more harmful for the tool and it might break under heavy loads
as in case of friction stir welding.
3.) Unnecessary hardening the tool would result in superfluous costs and would also cause wastage of time.
The chemical composition of the FSW tool material: M2 HSS is given below:
Table: 1.1 Chemical Composition Of M2 HSS

ELEMENTS W Mo Cr V C Si Mn Fe
MASS(%) 6.15 5.00 4.15 1.85 0.85 0.30 0.28 81.42

The physical properties of M2 HSS are listed below:

Table: 1.2 Physical Properties Of M2 HSS

IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i355

www.ijcrt.org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

Figure 1.2 M2 HSS Tool Used For Friction Stir Welding

The dimensions of the tool were as follows:
Table: 1.3 Tool Dimensions

Pin Height Pin Diameter Shoulder Diameter Collet Size for Tool Total Length of
Tool
1.5mm 5.0mm 18.0mm 18.0mm 94.5mm

1.1.3 MATERIAL OF THE TWO OUTER SHEETS TO BE JOINED

The aluminium alloys are joined in the experimentation of grade Al5052-H32. It is a comparatively softer
alloy than stainless steel.

Figure 1.3 Al5052 - H32 Sheets

The chemical composition of Al5052-H32 is given as:
Table: 1.4 Chemical Composition Of Al5052-H32
Element Mg Fe Cr Si Mn Cu Ti Al
Mass(%) 2.48 0.30 0.23 0.09 0.03 0.02 0.02 96.83

The physical properties of Al5052-H32 are mentioned below:

Table: 1.5 Physical Properties Of Al5052 - H32

The aluminium sheets are of the thicknesses 1 mm each and cross-sectional area 150 mm * 150 mm each.
1.1.4 THE SANDWICHED MATERIAL
Pure copper foil is used as the material that is sandwiched in the two sheets of aluminium alloys.
The physical properties of copper are given below:
Table: 1.6 Physical Properties Of Pure Copper

The value of Rockwell Hardness (F scale) for copper, is 54.

The thickness of the copper foil is 0.1 mm and the cross sectional area is 150 mm * 40 mm for each foil.

IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i356

www.ijcrt.org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

II. RESEARCH METHODOLOGY

2.1 TOPIC SELECTION & MATERIAL SELECTION
The topic was selected seeing the wide use of friction stir welding in the futuristic world. Also, another area
that was found interesting was copper cladded aluminium tubes.

Figure.2.1 Copper Cladded Aluminium Tubes

These kinds of tubes have vast applications in cooling the bigger computer systems and are also used in
super cars which heat up quite quickly when run at their limits, because of its excellent heat sinking capability.
Besides, the inner material is aluminium alloy (Al5052 H32) which is light weight as well as cheap and only a
thin layer of copper enhances its thermal properties. The copper cladded aluminium tubes could be used as a
radio frequency cable or as the refrigeration tubes. In this thesis work also the fundamentals of joining two
aluminium sheets with a copper foil in middle could be used to clad copper to aluminium alloy.
Among the different types of aluminium alloys, Al5052 was found to have good machinability, good
weldability, flexibility and also good corrosion resistance. On the other hand, copper was the best choice
available to construct a heat sink. Thus, both of them made a very good combination.

2.1.1 SELECTION OF EQUIPMENT

The Vertical Milling Centre (VMC) which a type of vertical milling machine having a CNC (computer
numeric control) interface was readily available rather than a dedicated FSW Setup which has not penetrated
into the market at a large scale. Moreover, the clamping modifications and tool mounting was very easy on a
VMC. So it was the best choice to conduct experiments.
2.1.2 SELECTION OF TOOL PROFILE AND MATERIAL
Upon going through various research papers, it was clear that the cylindrical pin profile was giving out best
results in terms of ultimate shear strengths in case of tensile strength for FSW joints. Also, since the thickness
of sheets forming the lap joint was very thin with the total thickness accounting to 2.1 mm, it was quite difficult
to form threading on the tool. However, only a single tool was used throughout which was straight cylindrical
(not tapered). The tool material was M2 HSS which is a tool standard and a trusted name in industry having
Rockwell hardness of 60 HRC without heat-treatment and 65 HRC after the heat treatment. For obvious reasons
as discussed in section 2.1.1, tool was used without any heat treatment.
2.2 PARAMETERS IN WORK
It is very essential to set restrictions in the boundary of research so as to be able to follow more vertical
approach. For the same, the tool material, tool profile and direction of rotation were kept constant while the tool
rotational speed, plunge depth and traverse speed were varied.

IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i357

www.ijcrt.org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

2.3 DESIGN OF EXPERIMENTS – TAGUCHI

A series of experiments were conducted, some of which failed with the tunneling defects in the friction stir
weld zone. With this the, favorable limits for the sampling method: Taguchi were set to obtain samples defect
free. Only the shear strengths of defect-free samples were considered.

Figure.2.2: FSW at 800 RPM; 0.1 mm Plunge Depth; 5 mm/min Traverse Speed (a) Front Side of Weld (b)
Back Side of Weld

Figure.2.3: 500 RPM; 0.4 mm Plunge Depth; 20 mm/min Traverse Speed (a) Front Side of Weld (b) Back Side
Of Weld

Figure.2.4: 700 RPM; 0.2 mm Plunge Depth; 20 mm/min Traverse Speed (a) Front Side of Weld (b) Back Side
Of Weld
The design of experimentation has been done in accordance with the Taguchi method, with the help of
“Minitab” software, and is listed below:
Table 2.1 Design and Actual Welding Parameters By Taguchi Method
S.No Rotational Speed(RPM) Traverse(mm/min) Plunge Depth (mm)
1 700 5 0.1
2 700 10 0.2
3 700 15 0.3
4 800 5 0.2
5 800 10 0.3
6 800 15 0.1
7 900 5 0.3
8 900 10 0.1
9 900 15 0.2

IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i358

www.ijcrt.org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

III. RESULTS AND DISCUSSIONS

There were a total of nine friction stir welded specimens tested for the shear strengths as per the L9
orthogonal array of Taguchi sampling method, having a sandwich structure with the two Al5052-H32
aluminium alloy sheets having thickness of 1 mm each on the outer sides and the copper foil of thickness 0.1
mm, place in the middle. Then, as per two parameters where the shear strengths came out to be the highest in
case of AlA-Cu-AlA multi-lap friction stir welded joints, two samples of AlA-AlA were friction stir lap welded
and their shear strengths were also determined.
The highest ultimate shear strength came out to be 4.413 MPa in the case of AlA-Cu-AlA joint with the
parameters: 800 rpm, 5 mm/min traverse and 0.2 mm plunge depth. For the same parameters, the ultimate shear
strength came out to be even higher as in the case of AlA-AlA joint having the ultimate shear strength as 5.955
MPa. Moreover, the second highest value of the ultimate shear strength came out to be 3.921 MPa, in case of
AlA-CuAlA joints at the parameters: 800 rpm, 15 mm/min traverse and 0.1 mm plunge depth. For the same
parameters, the ultimate shear strength for the AlA-AlA joint came out to be 4.922 MPa.
The need of proper clamping was felt during experimenting, especially in case of the thin sheets which bend
quite easily when the sliding load is applied. Moreover, setting the clamps very tightly over the work-piece
material deformed the surface of sheets as Al5052-H32, the work-piece material used, is a soft metal. So, the
resolution of the problem could be incorporation of more clamps in the middle or bring some modification in
the design of additional clamps such as the use of roller type clamp which is movable as well.

3.1 EXPERIMENTAL WORK

3.1.1 DESIGN OF EXPERIMENTS (D.O.E.)
Table 3.1 Actual Design of Experiments by Taguchi Method
S. No Level 1: Rotational Level 2: Traverse (mm/min) Level 3: Plunge
Speed (RSM) Depth (mm)
1 700(S) 5(S) 0.1(S)
2 700(S) 10(U) 0.2(U)
3 700(S) 15(W) 0.3(W)
4 800(U) 5(S) 0.1(S)
5 800(U) 10(U) 0.2(U)
6 800(U) 15(W) 0.3(W)
7 900(W) 5(S) 0.1(S)
8 900(W) 10(U) 0.2(U)
9 900(W) 15(W) 0.3(W)

3.2 CALCULATION OF ULTIMATE SHEAR STRENGTH

Figure: 4.1 Sample Preparations for Shear Testing

Figure.3.1: Front View of the Tool &Top View of the Tool

IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i359

www.ijcrt.org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

Thus, Area = Diameter of tool shoulder * Width of sample = 0.018 m * 0.04 m = 7.2 * 10-4
Also, ultimate shear strength (MPa) = maximum load of fracture (N) / contact area (m2) Hence, the values
for the ultimate shear strength are given as:
Table: 3.2 Ultimate Shear Strength Values
S.No. Parameters for AlA-Cu-AlA Joint Maximum Shear Ultimate Shear
(Tool Rotation Speed in RPM; Load (N) Strength (MPa)
Traverse Speed in mm/min;
Plunge Depth in mm)
1 800;5;0.2 3177.459 4.413
2 800;15;0.1 2823.318 3.921
3 900;10;0.1 2819.394 3.915
4 800;10;0.3 2727.180 3.787
5 900;15;0.2 2442.690 3.392
6 700;5;0.1 2159.181 2.998
7 900;5;0.3 1799.154 2.498
8 700;10;0.2 1654.947 2.298
9 700;15;0.3 1617.669 2.246
Table: 3.3 Response Table for Means

Table: 3.4 Response Table for Signal to Noise Ratios (Larger is better)
Level S U W
1 19.06 21.26 22.21
2 23.24 21.34 21.37
3 21.27 20.96 19.98
Delta 4.18 0.38 2.24
Rank 1 3 2

Figure: 3.2 Main Effects Plot For Means & Main Effects Plot For SN Ratio

IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i360

www.ijcrt.org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

3.3 MACROSTRUCTURE AND MICROSTRUCTURE AFTER F.S.W.

Figure: 3.3 Microstructure of Welded Sample Having Highest Ultimate Shear Strength

Figure: 3.4 SEM images of the weld surface at 1200X, 2000X, 3500X & 6500X Zoom

Figure: 3.5 SEM images of the weld surface at 12000X, 35000X & 65000X

Figure: 3.6 SEM images of the weld surface at 120000X Zoom

IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i361

www.ijcrt.org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

Figure: 3.7 Vicker’s Micro-hardness for the Sample with Optimum Parameters

3.4 CONCLUSION
After carrying out a series of experiments on the friction stir welded specimens, we come to the following
conclusions:
1.) The friction stir lap welded bond of AlA-AlA always has ultimate shear strength higher than the AlA-Cu-
AlA FSW lap joint for the same parameters.
2.) For the thin sheets, clamping is vital because otherwise the sheets may bend under the heavy loads.
3.) All the factors: plunge depth, tool rotational speed and the traverse speed play a very significant role in the
surface as well as the strength of the joint.
4.) In case of thin sheets of AL5052, lower values of tool rotational speed cause the material not to plasticize
properly and thus making a weak and irregular joint while the higher values of tool rotational speeds burn the
work-piece material and cause tunneling defects.
Friction stir welding, the process discussed in this thesis report has potential to be used in the aerospace
industry (since it doesn’t add any extra material to the existing mass), in heat exchangers as well as in the radio
communication industry. Also, as friction stir welding has the ability to make a leak-proof joint between the
dissimilar Al5052-H32 and pure Cu, the process could be utilized for the AlA-Cu structures based near water
bodies, even though it is not recommended due to electrolytic reaction and thus corrosion, yet is a better option
than other kind of welding processes.

REFERENCES
[1] Çam G. Friction stir welded structural materials: beyond Al-alloys. International Materials Reviews.
2011;56:1-48.
[2] Farrokhi H, Heidarzadeh A, Saeid T. Frictions stir welding of copper under different welding parameters
and media. Science and Technology of Welding and Joining. 2013;18:697-702.
[3] Motalleb-nejad P, Saeid T, Heidarzadeh A, Darzi K, Ashjari M. Effect of tool pin profile on microstructure
and mechanical properties of friction stir welded AZ31B magnesium alloy. Materials & Design.
2014;59:221-6.
[4] Mishra RS, Ma ZY. Friction stir welding and processing. Materials Science and Engineering: R: Reports.
2005;50:1-78.
[5] Amber Shrivastava, Michael Zinn, Neil A. Duffie, Nicola J. Ferrier, Christopher B. Smith, Frank E.
Pfefferkorn. Force measurement-based discontinuity detection during friction stir welding. Journal of
Manufacturing Processes 26 (2017) 113–121
[6] Pankaj Sahlot, Kaushal Jha, G.K. Dey, Amit Arora. Quantitative wear analysis of H13 steel tool during
friction stir welding of Cu-0.8%Cr-0.1%Zr alloy. Wear378- 379(2017)82–89.
[7] Bipul Das, Sukhomay Pal, Swarup Bag. Torque based defect detection and weld quality modelling in
friction stir welding process. Journal of Manufacturing Processes 27 (2017) 8–17. [8] Goebel, Jannik,
Reimann, Martin, Norman, Andrew, dos Santos, Jorge F., Semistationary shoulder bobbin tool friction stir
welding of AA2198-T851.Journal of Materials Processing Technology
http://dx.doi.org/10.1016/j.jmatprotec.2017.02.011
[9] Kush P. MEHTA, Vishvesh J. BADHEKA. Influence of tool pin design on properties of dissimilar copper
to aluminum friction stir welding. Trans. Nonferrous Met. Soc. China 27(2017) 36−54.
[10] G.M. Karthik, G.D. Janaki Ram, Ravi Sankar Kottada. Friction stir selective alloying. Materials Science &
Engineering A 684 (2017) 186–190.
IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i362
www.ijcrt.org © 2024 IJCRT | Volume 12, Issue 3 March 2024 | ISSN: 2320-2882

[11] N.Z. Khan, A.N. Siddiquee, Z.A. Khan, A.K. Mukhopadhyay, Mechanical and microstructural behavior of
friction stir welded similar and dissimilar sheets of AA2219 and AA7475 aluminium alloys, Journal of
Alloys and Compounds (2016), doi: 10.1016/j.jallcom.2016.11.389.
[12] Wei Zhang, Yifu Shen, Yinfei Yan and Rui Guo, Dissimilar friction stir welding of 6061 Al to T2 pure Cu
adopting tooth-shaped joint configuration: microstructure and mechanical properties, Materials Science &
Engineering A, http://dx.doi.org/10.1016/j.msea.2017.02.091
[13] Shude Ji, Zhengwei Li, Liguo Zhang, Yue Wang. Eliminating the tearing defect in Ti-6Al-4V alloy joint
by back heating assisted friction stir welding. Materials Letters.
[14] Nan Xu, Qining Song, Yefeng Bao, Yongfeng Jiang and Jun Shen, Achieving good strength-ductility
synergy of friction stir welded Cu joint by using large load with extremely low welding speed and rotation
rate, Materials Science & Engineering A, http://dx.doi.org/10.1016/j.msea.2017.01.052
[15] Hui Shi, Ke Chen, Zhiyuan Liang, Fengbo Dong, Taiwu Yu, Xianping Dong, Lanting Zhang, Aidang
Shan. Intermetallic Compounds in the Banded Structure and Their Effect on Mechanical Properties of
Al/Mg Dissimilar Friction StirWelding Joints. Journal of Materials Science & Technology (2016).
[16] Ahmed, M.M.Z., Ataya, Sabbah, El-Sayed Seleman, M.M., Ammar, H.R., Ahmed, Essam, Friction stir
welding of similar and dissimilar AA7075 and AA5083.Journal of Materials Processing Technology
http://dx.doi.org/10.1016/j.jmatprotec.2016.11.024
[17] H. Dawson, M. Serrano, S. Cater, N. Iqbal, L. Almásy, Q. Tian, E. Jimenez- Melero, Impact of friction stir
welding on the microstructure of ODS steel, Journal of Nuclear Materials (2017), doi:
10.1016/j.jnucmat.2016.12.033.
[18] Kim, K.H., Bang, H.S., Bang, H.S., Kaplan, A.F.H., Joint properties of ultra thin 430M2 ferritic stainless
steel sheets by friction stir welding using pinless tool.Journal of Materials Processing Technology
http://dx.doi.org/10.1016/j.jmatprotec.2016.12.018
[19] V.C. Sinha, S. Kundu, S. Chatterjee. Microstructure and mechanical propertiesof similar and dissimilar
joints of aluminiumalloy and pure copper by friction stir welding. Perspectives in Science (2016) 8, 543—
546 51
[20] Q. Zheng, X. Feng, Y. Shen, G. Huang, P. Zhao, Dissimilar friction stir welding of 6061 Al to 316
stainless steel using Zn as a filler metal, Journal of Alloys and Compounds (2016), doi:
10.1016/j.jallcom.2016.06.092.
[21] A. Yazdipour, A. Heidarzadeh, Effect of friction stir welding on microstructure and mechanical properties
of dissimilar Al 5083-H321 and 316L stainless steel alloy joints, Journal of Alloys and Compounds
(2016), doi: 10.1016/j.jallcom.2016.03.307.

IJCRT2403994 International Journal of Creative Research Thoughts (IJCRT) www.ijcrt.org i363