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Friction stir welding of aluminium alloys EN AW 2024-0 and EN AW 5754-H22
C. Ozarpa
a
, A. Ogur
b
, G. Cam
c
, M. Vural
d
a, c
Istanbul Technical University, Faculty of Mechanical Engineering, Gumussuyu, Istanbul, Turkey
*Corresponding author; e-mail: cozarpa@igdas.com.tr, e-mail: vuralmu@itu.edu.tr
b
Sakarya University, Faculty of Engineering, Esentepe, Sakarya, Turkey
*Corresponding author; e-mail: ogur@sau.edu.tr
d
Mustafa Kemal University, Faculty of Engineering, Hatay, Turkey
*Corresponding author; e-mail: gcam@mku.edu.tr
Abstract
Friction Stir welding (FSW) is a new solid phase technique invented and patented for the butt and lap welding of ferrous and non-
ferrous metals. In this article, structure and mechanical properties of friction welded joınts of aluminium alloys EN AW 2024 and EN
AW 5754 is studied. By using of different aluminium alloys EN AW 2024 and EN AW 5754 , friction stir welding performed that is
called dissimilar welding.
Keywords: Friction stir welding; Aluminium alloys 2024 and 5754; Dissimilar metarial welding
1. Introduction
A method of solid phase welding, which permits a wide range
of parts and geometries to be welded, and called friction stir
welding (FSW), was invented by W. Thomas and his colleagues
of The Welding Institute (TWI), UK, in 1991. [1]
Friction stir welding can be used for joining many types of
material and metal combinations, if tool material and designs can
be found which operate at the forging temperature of the
workpieces. The process has been used for manufacture of butt
welds, overlap welds, T-sections and corner welds. For each of
these joint geometries specific tool designs are required which are
being further developed and optimised. In this study we have
studied the butt welding of the EN AW 2024 and EN AW 5754
Al alloys. [2, 3]
Friction stir welding is a relatively simple process as shown
in Figure1. and a specially shaped cylindrical tool with a screw
thread probe, made from material that have a hard and wear
resistant relative to the material being welded, is rotated and
plunged into the abutting edges of the aluminium parts to be
joined. After entry of the screw thread probe to almost the
thickness of the material and to allow the tool shoulder to just
penetrate into the aluminium plate, the rotating tool is transitioned
along the joint line. The rotating tool develops frictional heating of
the material, causing it to plasticize and flow from the front of the
tool to the back where it cools and consolidates to produce a high
integrity weld, in the solid phase. [4, 5]
Subsequent improvement mainly accomplished in the tool
design brought the technology forward for application especially
to commercial aluminum alloys such as 2219, 2014, 6083, 6082
and 7075. Friction stir welding has a wide application potential in
ship building, aerospace, automobile and other manufacturing
industries. The developments in friction stir welding of Al and
Mg alloys will make the production of lightweight transport
system possible, thus considerible reductions in fuel cosumptiom
could be achived [1, 2]
The process proves predominance for welding non-heat-
treatable or powder metallurgy aluminum alloys, to which the
fusion welding can not be applied. Thus fundamental studies both
on the weld mechanism and on the relation all arrow ship
between microstructure , properties and process parameters,
have recently been started [5, 6].
Figure 1.Schema of friction stir welding of aluminium alloys.
758
C. Ozarpa, A. Ogur, G. Cam, M. Vural
2. Experimental Procedures
2.1. Material
The materials tested are hot-rolled plates of commercial
aluminium alloys EN AW-2024 [AlCu4Mgl] and EN AW-5754
[AlMg3] of 3 mm thick, supplied by ACA Metal Co., the nominal
composition of which is given below in table 1. and mechanical
properties is given in table 2.
Table 1.
The nominal composition of commercial aluminium alloy EN
AW-2024 [AlCu4Mgl] and EN AW-5754 [AlMg3]
Al
Alloy
Si
%
Fe %
Cu
%
Mn
%
Mg
%
Cr %
Zn %
Ti %
2024 0.50 0.50 3.8-
4.9
0.30-
0.9
1.2-
1.8 0.10 0.25 0.15
5754 0.40 0.40 0.10 0.50 2.6-
3.6 0.30 0.20 0.15
Table 2.
Mechanical properties of commercial aluminium alloy EN AW-
2024 [AlCu4Mgl] and EN AW-5754 [AlMg3
Thickness
(mm) Rm (MPa)
Rp 0,2
(MPa)
Elongation,
min (%)
Tem-
per
Hard-
ness
(BS) Between Min
Ma
x Min
Ma
x
A
50
mm
A
2024
-
O
55 3 6 -- 220 140 13 -
5754-
H22/H
32
63 3 6 220 270 130 11 -
2.2. Friction Stir Welding
Friction stir welding (FSW) was carried out according to the
following sequence. A pair of workpieces free from oil films
were abutted along a longitudinal section and fastened rigidly on
the steel thick backing plate, which was mechanically fixed on
the bed of a vertical type-milling machine (DAHLIH MCV 1020
BA CNC has a rotating speed 10.000 rpm. and transition speed
max. 20 m/min.) A specially designed rotating tool, the details of
which are shown in Fig.2, saw from the chuck side and rotated
anti-clockwise was vertically inserted in the workpiece(Navasawa
and Otsuka,2003) . The surface of the workpiece came in contact
in the shoulder, and the insertion of the rotating tool was stopped,
after the generation of frictional heating was waited enough by
the thing maintained as it was for 40 seconds, tools were moved
along the joint line and welded. In this case, the height and
diameter of pin was 2.8 mm and 6.0 mm, and order screw of M6
was given, respectively.
In this paper, tool rotation speed (rpm) and transition speed
(welding speed mm/min.) will be given in table 3, table 4 and table 5.
Figure 2: Specially designed rotating tool details
Table 3.
Welded specimens tensile test results and welding performances
of EN AW 2024 Al alloy
Weld
Performance
Alloy and
Temper
Condition
Revoluati
on Speed
(rpm)
Welding
speed
(mm/min)
Ultimate
Tensile
Strength
(MPa)
Elongat
ion (%)
Strength.
(%)
Elongat
ion (%)
… Base Metal 177.93 9.67 … …
15 115.34 0.71 64.82%
7.34%
15 154.18 1.73 86.65%
17.89%
10 107.74 0.84 60.55%
8.69%
10 171.81 4.48 96.56%
46.33%
7.5 107.6 0.57 60.47%
5.89%
AL 2024 0
2000
7.5 119.97 1 67.43%
10.34%
… Base Metal 173.80 16.33
… …
15 104.56 1.37 60.16%
8.39%
15 123.35 1.05 70.97%
6.43%
10 123.52 1 71.07%
6.12%
10 168.48 3.23 96.94%
19.78%
7.5 116.40 0.72 66.97%
4.41%
AL 2024
AA*
*
Artificial
Aging
After
welding
2000
7.5 132.27 1.16 76.10%
7.10%
… Base Metal 173.80 16.33
… …
7.5 111.50 0.62 64.15%
3.80%
7.5 122.87 0.78 70.70%
4.78%
5 144.50 1.4 83.14%
8.57%
AL 2024
AA
Artificial
aging
before
welding
2000
5 117.68 0.79 67.71%
4.84%
Typically, the surface apparence of FSW is a regular series of
partially circular ripples, which point towords the start of the weld.
These ripples are essentially cycloidal and are produced by the final
sweep of the trailing circumferential edge of the shoulder during
traverse. The rotational speed of the tool and traverse speed of work
piece determine the pitch between the ripples. The surface colour of
FSW is sivery white for studied materials (Kulekci,2003). In order to
evaluate the performance of friction stir weld of EN AW 2024 and EN
AW 5754 aluminium alloys, several tests employed. The speciman
used in mechanical test were machined out of the welded joint so that
the longitual rolling direction of the material was parallel to the traverse
direction. EN 485-2 is used to dimension test specimens for tensile test.
The gauge section of tensile test specimens was located within the
welded zone and had a size of 200 x 50 x 10 mm.
Friction stir welding of aluminium alloys EN AW 2024-0 and EN AW 5754-H22
759
Table 4.
Welded specimens tensile test results and welding performances
of EN AW 5754 Al alloy
Weld Performance
Alloy
and
Tempe
r
Conditi
on
Revolu
ation
Speed
(rpm)
Weldin
g speed
(mm/m
in)
Ultimate
Tensile
Strength
(MPa)
Elongation (%)
Strength.(%
)
Elongation
(%)
Base
Metal
235,17 15,04 … …
25 134,53 1,68 57,21% 11,17%
25 108,73 0,96 46,23% 6,38%
20 90,87 0,63 38,64% 4,19%
20 95,92 0,64 40,79% 4,26%
15 99,23 0,68 42,20% 4,52%
3000
15 102,9 1,1 43,76% 7,31%
… Base
Metal
235,17 15,04 … …
25 96,79 0,61 41,16% 4,05%
25 95,35 0,58 40,55% 3,85%
20 99,19 0,73 42,18% 4,84%
20 102,26 0,67 43,48% 4,44%
15 111,27 0,91 47,31% 6,04%
AL
5754 H
22
2000
15 104,35 0,81 44,37% 5,37%
Table 5.
Tensile test results of dissimilar welded EN AW 2024 and EN
AW 5754 specimens and welding performances
Weld Performance
Alloy
and
Temper
Conditio
n
Revolu
ation
Speed
(rpm)
Weldin
g speed
(mm/m
in)
Ultimate
Tensile
Strength
(MPa)
Elonga-
tion (%)
Strength.(%)
Elongation
(%)
AL 2024
0
Base Metal 177,93 9,67 … …
AL 5754
H 22
Base Metal 235,17 15,04 … …
2000 5 111,27 0,81 62,54% 8,38%
2024 -
5754
H22 2000 5 118,13 0,95 66,39% 9,82%
3. Results and Discussion
In order to evaluate the performance of friction stir weld joint
of EN AW-2024 and EN AW-5754 alloy plate, the tensile test
was applied to base metal (given results for base metal is the
average of three different specimens) and friction stir welded
specimens. The results of tensile tests are given below in table 3,
table 4, and table 5.
Artificial aging was performed by using of a industrial oven.
After welding process and before welding process aliminium
plates were stayed in industrial oven 8,5 hour at a tempereture of
190
0
C for artificial aging (Atik and Meric,2001) .
Dissimilar material, EN AW 2024 and EN AW 5757 alloys were
welded by friction stir welding. Welding performances were given in
table 5. Welding performance reached a value of 66,93 %.
Microstructure observation of welded joints were made. The
mechanically polished surface was chemically etched with an
agent, the standard compositions. Welding zone is observed in
the electronmicroscope. And analysis of black area is given in
table 4. There is no change in microstructure of welding area.
Table 6.
Elektron microscope analysis of black area of EN AW 5754
shown in figure 3 b).
ELT. LINE INTESITY (c/s) CONC
O Ka 12.06 4.257 wt.%
Mg Ka 43.68 3.051 wt.%
Al Ka 1126.32 92.692 wt.%
a) Base metal
b) Welded metal
Figure 3. Microstructure of EN AW 5754 in elektronmicroscope
Figure 4: Microstructure of welded area of EN AW 2024
760
C. Ozarpa, A. Ogur, G. Cam, M. Vural
0
20
40
60
80
100
120
140
1
4
7
10
13
16
19
22
25
28
Distance from weld center mm
Hardness HV0,1
2000 5 2T6
2000 7,5 2T6
2000 7,5 2
2000 10 2
2000 15 2
2000 15 ST6
2000 10 ST6
2000 7,5 ST6
Figure 5: Hardness profile of EN AW 2024 measured along a
central line on the transverse plane perpendicular to the welding
direction
The microstructure of welded joints was evaluated by
measuring hardness distribution along a central line drawn on a
plane perpendicular to the tool transitioning direction. The results
are given below in figure 5, figure 6 and figure 7
0
20
40
60
80
100
120
140
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
3000 15 57
3000 20 57
3000 25 57
2000 15 57
2000 20 57
2000 25 57
Figure 6: Hardness profile of EN AW 5754 measured along a
central line on the transverse plane perpendicular to the welding
direction.
D 2000 5 20 57
0
10
20
30
40
50
60
70
80
90
100
1
3
5
7
9
11
13
15
17
19
21
23
25
27
Distance from weld center mm.
Hardness HV0,1
D 2000 5 20 57
Figure 7. Hardness profile of EN AW 2024 and EN AW 5754
measured along a central line on the transverse plane
perpendicular to the welding direction.
As shown in figure 6.friction stir welding is performed for
EN AW 2024 by rotating speed 2000 rpm. and by different four
welding speeds (5, 7.5 ,10, and 15 mm/min).
As shown in figure 6. there are two rotating speeds (3000 and
2000 rpm.) and three welding speeds (15, 20 and 25 mm/min).
Hardness profile of dissimilar welding of EN AW 2024 and
EN AW 5754 is given in figure 7. Welding is performed by 2000
prm pin speed and 5 mm/min welding speed. In different welding
speed (as 20, 15,10 mm/min) we have tried to perform friction
stir welding but welding could not be performed.
4. Conclusions
The following conclusions can be written:
Friction stir welding process is based on machine technology.
This process is able to semi and fully automated.
After welding process surface quality is high, this situation
reduces production costs in further processing and finishing.
There is no need consumable materials and shielding gas.
The process is solid phase with process temperature regimes
lower than fusion techniques, thus avoiding problems, which
occur with the liquid phase such as alloy segregation, porosity,
cracking and distorsion.
Hardness value in weld area for EN AW 2024, there is an
increase about 10-40 Hv. Because of this is recrystalization and
getting smaller grains. For EN AW 5754 there is a decrease of
hardness value because of recrystalization.
Welding performance of EN AW 2024 is reached to 96,6 %.
This value is 57 % for EN AW 5754.
t is possible to perform dissimilar welding using different
aluminium allaoys. Welding performance of dissimilar welding
EN AW 2024 and EN AW5754 is reached a value of 66,39%
References
[1] Cam ,G. 1999. Secience and Technology of joining and
welding, 4, 1999 : 317.
[2] Navasawa ,T. and Otsuka , M. 2003. Structure and
Mechanical Properties of Friction Stir Weld Joints of
Magnesium Alloy AZ31,298110, Japon 2003
[3] Nicholas ,E.D.1998. Developments in the Friction Stir
Welding of Metals, Proc. of ICAA-6 (6
th
Int. Conf.
Aluminum Alloys), Toyohashi, Japan, (1998) :139-151.
[4] Thomas, W.M.; Nicholas, E.D.;Needham, J.C. ;Murch,M.G.;
Templesmith ,P. and Dawes,C.J.1991. Friction Stir Butt
Welding h, International Patent Application PCT GB 920 22
03, GB Patent Application 9125978.8, 6 Dec. 1991 and US
Patent 5,460,317.
[5] Yang ,H.S., Microstructural Development in Friction Stir
Welding of Aluminum Alloys Proc. of ICAA-6 (6
th
Int. Conf.
Aluminum Alloys), Toyohashi, Japan, (1998): 1483-1488.
[6] 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, Volume 142(2003), 692-696
Distance from weld center mm
Hardness Hv 0,1
