K. ANGANAN et al.: EXPERIMENTAL STUDY AND ANALYSIS OF THE WEAR PROPERTIES OF ...
201–205
EXPERIMENTAL STUDY AND ANALYSIS OF THE WEAR
PROPERTIES OF FRICTION-STIR-WELDED AA7075-T6 AND
A384.0-T6 DISSIMILAR ALUMINIUM ALLOYS OF BUTT JOINTS
EKSPERIMENTALNA [TUDIJA IN ANALIZA OBRABE ZVAROV,
IZDELANIH Z ROTACIJSKIM TORNIM VARJENJEM
RAZNOVRSTNIH ZLITIN AA7075-T6 IN A384.0-T6
Karuppannan Anganan1, Subramaniam Prabagaran2, Mayakrishnan Muthukrishnan3
1Karpagam Academy of Higher Education, Coimbatore, Department of Mechanical Engineering, 641 021 Tamil Nadu, India
2Karpagam Academy of Higher Education, Department of Mechanical Engineering, Coimbatore, 641 021 Tamil Nadu, India
3Kalaignar Karunanidhi Institute of Technology, Department of Mechanical Engineering, Coimbatore, 641 402 Tamil Nadu, India
anganan09@gmail.com
Prejem rokopisa – received: 2017-07-06; sprejem za objavo – accepted for publication: 2017-10-11
doi:10.17222/mit.2017.109
The wear is one of the main issues in friction-stir welding (FSW) of dissimilar aluminium alloys. Two dissimilar metals welded
with FSW have different mechanical, metallurgical and chemical properties compared to the parent materials. Therefore, the
wear resistance is an important property in an FSW process. In this research, AA7075-T6 and A384.0-T6 aluminium alloys with
a thickness of 6.35 mm were selected and a design matrix was developed to produce FSW welds using the MINITAB-17
software. Friction-stir-welded pieces were made as test specimens and their ultimate tensile strengths (UTSs) were tested. In
these experiments, the maximum- and minimum-UTS specimens were used for a wear-resistance analysis and its results were
compared with the wear resistance of the parent metals. The results were obtained by keeping the revolutions per minute
(min–1), time and sliding velocity as constants, while varying the load applied. The rpm, time and sliding velocity were 500, 300
s and 3.141 m/s, respectively. The loads applied were (20, 40 and 60) N. The conclusion is that, under all the applied loads, the
wear of the friction-stir weld produced is lower than that of the A384.0-T6 aluminium base metal. On the other hand, the wear
of the weld is higher than the AA7075-T6 aluminium base metal.
Keywords: wear resistance, dissimilar aluminium alloys, friction-stir welding, base metals, wear-resistance parameters
Obraba raznovrstnih aluminijevih zlitin je ena od glavnih tem v raziskavah na podro~ju rotacijskega tornega varjenja (FSW;
angl.: Friction Stir Welding). Dve razli~ni kovini, ki ju varimo, imata med FSW razli~ne mehanske, metalur{ke in kemi~ne
lastnosti v primerjavi s sorodnimi materiali. Odpornost proti obrabi je pomembna lastnost v FSW-procesu. V tej raziskavi so
avtorji izbrali dve Al zlitini AA7075-T6 in A384.0-T6 debeline 6,35 mm in z njima oblikovali matrico za FSW-zvare z uporabo
programske opreme MINITAB-17. Izdelali so vzorce varjene s postopkom FSW in dolo~ili natezno trdnost zvarov. Nato so za
nadaljnje preiskave obrabe izbrali vzorce z najmanj{o in najve~jo natezno trdnostjo in jih primerjali z FSW-zvari, izdelanimi iz
sorodnih materialov. Med eksperimenti so dr`ali konstantne naslednje procesne parametre varjenja: {tevilo obratov na minuto
(500 min–1), ~as (300 s) in hitrost drsenja (3,141 m/s); spreminjali pa so obremenitev (20, 40 in 60) N. Avtorji so v tej raziskavi
ugotovili, da je obrabna obstojnost zvarov, izdelanih z FSW druga~na od obrabe zvarov izdelanih iz osnovne Al zlitine
A384.0-T6 pri vseh obremenitvah. Obrabna obstojnost izdelanih zvarov iz izbranih nesorodnih zlitin pa je primerljiva z zvari
izdelanimi iz Al zlitine AA7075-T6.
Klju~ne besede: odpornost proti obrabi, raznovrstne Al zlitine, rotacijsko torno varjenje, osnovne kovine, parametri obrabne
odpornosti
1 INTRODUCTION
FSW is one of the solid-state fumeless welding
techniques. It was invented, developed and patented in
1991 by Wayne Thomas, The Welding Institute, United
Kingdom.1 For our experiment, the plates to be welded
were placed adjacent to each other and tightly clamped
by a specially made fixture. A tool was fitted to a chuck
and that was then fitted to the spindle of an FSW
machine. Figure 1 depicts the FSW machine. A rotating
tool with an axial pressure force and longitudinal
movement was inserted between the two plates. Hence,
as a stirring action takes place between the plates, heat is
developed and the metals are plastically deformed and
joined together.2 The concept of an FSW process is
shown in Figure 2. After the FSW process, the mecha-
nical, metallurgical, thermal and chemical properties are
changed compared to the parent-material properties. In
this research, the wear properties were analysed.
L. Guo et al.3 investigated the lubrication effect of
annealed Fe78Si9B13 glass particles in the FSW of the
AA6061 metal and found that the particles play an
important role in improving the wear resistance. S. K.
Naimuddin et al.4 conducted an experimental study
analysis of similar and dissimilar joints of the materials
of (AA6061-AA6061), (AA6082-AA6082) &
(AA6061-AA6082) under T6 conditions to find the wear
behaviours. They found low wear and low wear resis-
tance in the FSW welds. A. M. Hassan et al.5 experimen-
tally studied the wear characteristics of aluminium-
Materiali in tehnologije / Materials and technology 52 (2018) 2, 201–205 201
UDK 620.1:620.178.16:669.715 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 52(2)201(2018)
matrix composites reinforced with graphite and silicon
carbide particles using FSW techniques. The results
showed that the process parameters greatly influenced
the wear resistance of the welded joints.
S. Prabagaran et al.7 experimentally proved that the
formation of the oxides at the interface plays a signifi-
cant role in reducing the wear rate. To take decisions
about FSW weld quality, many welding parameters like
tool rotational speed, welding feed, axial load, tool pin
profile, etc., are considered.8 Many researchers are very
interested in optimizing the FSW process parameters.9
At the same time, most of the researchers analyse the
FSW tool-design parameters with regard to the welding
strength of the joints.10–13 R. Kumar et al.14 experimen-
tally studied the wear characteristics and defects after the
FSW of AA6061-T6 aluminium alloys using different
tool rotational speeds and welding speeds. They con-
cluded that the wear resistance of the FSW joints
increased compared to the base material.
2 EXPERIMENTAL SET-UP
In this research, the selected base materials were
wrought aluminium AA7075-T6 and cast aluminium
A384.0-T6 with a 6.35-mm thickness. Aluminium and
its alloys have low densities and high strength-to-weight
ratios. As a result, these materials are used in various
fields.15,16 The wrought AA7075-T6 aluminium with a
6.35-mm thickness was purchased and machined to
dimensions of (100 × 50 × 6.35) mm using a circular saw
machine. The A384.0-T6 aluminium was cast as an ingot
and machined to dimensions of 100 × 50 × 6.35 mm
using a saw machine and lathe. The chemical composi-
tions and mechanical properties of the parent materials
were tested and tabulated in Table 1 and Table 2,
respectively.
Table 2: Mechanical properties of the base metals
Base metals UTS(MPa)
YS
(MPa)
Elongation
(%)
Hardness
(HRB)
AA7075-T6 581.1 379.8 11.7 92.0
A384.0-T6 102.0 - 1.0 35.8
Table 3: Welding parameters
Process
parameters Unit
Sym-
bol
Levels
-1.682 -1 0 1 1.682
Tool rotational
speed min
–1 N 600 680 800 920 1000
Welding speed mm/min S 30 35 40 46 50
Axial load kN F 6 6.8 8 9.2 10
A design matrix was developed using the MINI-
TAB-17 software with 3 variables and 5 levels. The
welding parameters, or the variables selected for this
research, were the tool rotational speed in min–1, the
welding speed in mm/min and the axial load in kilo
newton. These are shown in Table 3. After making
different FSW welds as per the design matrix, the
ultimate tensile strength (UTS) was tested and its values
were tabulated in Table 4.
As seen in Table 4, the minimum UTS for Run
Number 5 was 246.33 MPa. The maximum UTS for Run
Number 10 was 277.37 MPa. These two FSW welds
were taken for further analysis of the wear resistance;
Runs 5 and 10 were also re-designated as W-1 and W-2,
respectively. The wear rates for W-1 and W-2 were
K. ANGANAN et al.: EXPERIMENTAL STUDY AND ANALYSIS OF THE WEAR PROPERTIES OF ...
202 Materiali in tehnologije / Materials and technology 52 (2018) 2, 201–205
Figure 2: FSW process principle6
Figure 1: FSW machine
Table 1: Chemical compositions of the base metals
Metals/ elements Mg Mn Pb Zn Fe Cu Si Cr Ni Al
AA7075-T6 2.29 0.047 0.004 5.44 0.20 1.45 0.071 0.24 0.006 Balance
A384.0-T6 0.11 0.24 0.54 1.83 0.96 1.54 10.15 0.031 0.099 Balance
analysed and compared with the wear resistance of the
parent materials, viz., AA7075-T6 and A384.0-T6. The
removal of the material from the solid surfaces of a
solid-state contact is known as the wear.
Table 4: Design matrix and the UTS results in MPa
Run no.
Design matrix
FSW process parameters UTS
N F S MPa
1 -1 1 -1 252.80
2 0 0 0 272.96
3 1 -1 -1 260.22
4 1 -1 1 255.85
5 -1 -1 -1 246.33
6 1 1 -1 267.80
7 1.682 0 0 261.76
8 -1.682 0 0 248.06
9 0 0 -1.682 260.60
10 1 1 1 277.37
11 0 1.682 0 264.02
12 -1 -1 1 252.37
13 0 0 1.682 271.67
14 -1 1 1 260.94
15 0 -1.682 0 248.31
16 0 0 0 271.00
17 0 0 0 271.90
18 0 0 0 272.00
19 0 0 0 272.10
20 0 0 0 271.80
The wear occurs on the outer surfaces of compo-
nents. In this research, the pin-on-disk wear-testing me-
thod was adopted. The pin-on-disk wear-testing appara-
tus is shown in Figures 3 and 4. During this tribological
test, a stationary disk rubs against the rotating pin while
the applied load is constant.17 For the normal load range,
the frictional-force range of the pin-on-disk apparatus
was up to 200 N. The sliding speed was 0.26–12 m/s and
the disk speed was 100–2000 min–1. The wear-disk
diameter was 165 mm and it was made of the En31
material having a disk hardness of 58–60 HRC. The
wear-disk track diameter ranged from 10 mm to
140 mm. The specimen-pin diameter ranged from 3 mm
to 12 mm and the length of the specimen pin ranged
from 25 to 30 mm.
The dimensions of the specimen prepared for this
research were (30 × 12 × 6.35) mm; the specimen
consisted of the base metals AA7075-T6 and A384.0-T6.
In the case of the dissimilar combination, the minimum
and maximum UTSs were obtained for welded plates
W-1 and W-2, whose weld-nugget areas were used as
specimens for the wear test. The experimental wear tests
were conducted under dry sliding conditions at normal
atmospheric temperature and pressure. Figures 5 and 6
depict the respective wear-test specimen.
3 RESULTS AND DISCUSSIONS
While conducting the wear test, the time and the
revolution per minute of the disc were kept constant at
300 s and 500 min–1, respectively. By varying the mate-
K. ANGANAN et al.: EXPERIMENTAL STUDY AND ANALYSIS OF THE WEAR PROPERTIES OF ...
Materiali in tehnologije / Materials and technology 52 (2018) 2, 201–205 203
Figure 3: Pin-on-disk wear-test apparatus
Figure 4: Pin-on-disk wear-test apparatus
Figure 6: Specimen after the wear test
Figure 5: Specimen before the wear test
rial and the applied loads, the magnitude of the wear in
microns was tabulated in Table 5.
Using the above table, on the basis of the same
applied loads, the materials were segregated and the
wear values in microns were discussed. The materials at
a 20-N load were grouped in one category and shown in
Figure 7 as a bar chart. In this bar chart, the X-axis
represents various materials and the Y-axis represents the
wear in microns. The wear of the base material
A384.0-T6 is higher than that of the base material
AA7075-T6 or that of welds W-1 and W-2. This is
because the hardness of the base material AA7075-T6
has a high hardness of 92 HRB, whereas the base
material A384.0-T6 has a low hardness of 35.8 HRB.
The materials at a 40-N load were grouped in another
category and shown in Figure 8 as a bar chart. In this
case, the wear of A384.0-T6 is also higher than that of
the base material AA7075-T6 or that of dissimilar weld
combinations of AA7075-T6 and A384.0-T6. The
materials at a 60-N load were grouped as the third
category and shown in Figure 9 as a bar chart. In this
case, the wear of A384.0-T6 is also higher than that of
the base material AA7075-T6 or that of dissimilar weld
combinations of AA7075-T6 and A384.0-T6. The wear
values for the base material AA7075-T6 and dissimilar
friction-stir weld W-2 are more or less the same.
K. ANGANAN et al.: EXPERIMENTAL STUDY AND ANALYSIS OF THE WEAR PROPERTIES OF ...
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Table 5: Wear values
Sl.no. Material min–1 Load (N) Time (s) Slidingvelocity
Wear in
microns COF average
Frictional force
(N) average
1 7075 500 20 300 3.141 m/s 27.34 0.4469 8.93
2 7075 500 40 300 3.141 m/s 43.07 0.3768 15.07
3 7075 500 60 300 3.141 m/s 38.17 0.3538 21.23
4 W-1 500 20 300 3.141 m/s 70.01 0.508 10.16
5 W-1 500 40 300 3.141 m/s 55.16 0.3451 13.80
6 W-1 500 60 300 3.141 m/s 50.56 0.2817 16.90
7 W-2 500 20 300 3.141 m/s 50.03 0.1452 2.90
8 W-2 500 40 300 3.141 m/s 50.19 0.2725 10.90
9 W-2 500 60 300 3.141 m/s 38.39 0.3088 18.53
10 384 500 20 300 3.141 m/s 90.51 0.345 6.90
11 384 500 40 300 3.141 m/s 63.77 0.4156 16.62
12 384 500 60 300 3.141 m/s 62.46 0.3354 20.12
Figure 10: Material wear at (20, 40 and 60) NFigure 7: Wear in microns at a load of 20 N
Figure 9: Wear in microns at a load of 60 N
Figure 8: Wear in microns at a load of 40 N
Figure 10 shows the wear in microns of the base
material AA7075-T6, welds W-1, W-2 and the base
material A384.0-T6 with the applied loads of 20, 40 and
60 N. In the case of the base material AA7075-T6 at the
applied loads of 20, 40 and 60 N, the wear was higher at
the load of 40 N. In the cases of dissimilar welds W-1,
W-2 and the base material A384.0-T6, the wear was
reduced if the applied load was increased. This may be
due to the increase in the temperature during the wear of
the materials.
4 CONCLUSIONS
The wear is one of the major mechanical properties
of any material. In this research, the base materials were
AA7075-T6 and A384.0-T6 aluminium alloys. The wear
was discussed and analysed based on the analyses of
dissimilar welds combining the AA7075-T6 and
A384.0-T6 aluminium materials. The AA7075-T6
aluminium alloy had a high hardness of 92 HRB and the
A384.0-T6 aluminium alloy had a hardness of 35.8
HRB. The hardness of FSW welds was between 35.8 and
92 HRB. At the same time, the wear was higher for the
A384.0-T6 aluminium alloy and lower for the
AA7075-T6 aluminium alloy. For the combinations of
FSW welds, the wear was between the wear values of the
base materials. Therefore, the hardness of materials and
the level of wear are inter-related parameters. This was
proved in our research.
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