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Transactions of the Indian Institute ofMetals ISSN 0972-2815Volume 72Number 2 Trans Indian Inst Met (2019) 72:487-500DOI 10.1007/s12666-018-1500-z
Mechanical Properties and Microstructureson Dissimilar Metal Joints of Stainless Steel301 and Aluminum Alloy 1100 by Micro-Resistance Spot Welding
Ario Sunar Baskoro, Hakam Muzakki,Gandjar Kiswanto & Winarto Winarto
1 23
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TECHNICAL PAPER
Mechanical Properties and Microstructures on Dissimilar MetalJoints of Stainless Steel 301 and Aluminum Alloy 1100 by Micro-Resistance Spot Welding
Ario Sunar Baskoro1 • Hakam Muzakki1 • Gandjar Kiswanto1 • Winarto Winarto2
Received: 12 December 2017 / Accepted: 5 November 2018 / Published online: 4 December 2018
� The Indian Institute of Metals - IIM 2018
Abstract Aluminum and stainless steel are metals that
have some mechanical property advantages. Welding
technology has been developed to join both different and
dissimilar metals applied in a construction. The property
advantages have been used to improve the performance of
a construction. However, welding performance still creates
a problem as a result of properties’ differences in metals.
This study investigated the mechanical properties of a
steel-aluminum joint with the thickness of less than 1 mm,
welded by resistance spot welding (RSW); it is called a
micro-RSW. Mechanical properties of the joint were ana-
lyzed by tensile test and were measured at the fracture area
on the tensile test specimen. Moreover, it also analyzed
intermetallic microstructure in the nugget or welding joint.
Welding time of 8 CT was an optimum parameter on a
welding process to get the maximum load. The fracto-
graphic structure of a stainless steel-aluminum joint
showed a brittle nugget. Moreover, the fracture area on the
aluminum side was larger than that of the stainless steel.
Intermetallic compound (IMC) was created by melting and
joining it through the heat input in the welding process.
IMC in SS301-AA1100 nugget affected a brittle joint.
Keywords Dissimilar metals �Micro-resistance spot welding � Mechanical properties �Fractography and microstructures
1 Introduction
Stainless steel and aluminum show such excellent mechan-
ical properties. Aluminum alloy has widely been used in
various constructions including aerospace engine parts and
electrical equipments because of its high corrosion resis-
tance, low density, and easy recyclability [1]. Stainless steel
is a potential material used in light constructions and auto-
motive apparatus because of its superb corrosion resistance,
toughness, high strength, and hardness [2]. The advantages
of both materials can be synergized in the production process
of advanced products such as medical equipment by apply-
ing dissimilar joints. Nevertheless, there are many issues
hindering the process of joining aluminum and steel directly.
They include the welding methods [3], the IMC layer
structure in the nugget, and the difficulty in developing a
bond between the two metals [4].
In order to overcome the aforementioned problems,
several strategies have been proposed. Ezazi et al.
employed laser power welding to join a piece of 1 mm
stainless steel (SS) 304 and a piece of aluminum alloy
(AA) 5085 sheet. They found out that the strengths of the
joints had doubled up to 1.48 and 1.85 times by pre-placing
the single and multi-component activating flux (oxide-
based TiO2 and halide-based CaF2 flux powders) on the
surface [5]. Aluminum and copper were welded through
friction stir welding. Effect of plate position, tool offset,
tool rotational speed on mechanical properties and
microstructures were studied by Sahu et al. Their study
revealed that IMC of Al–Cu was almost the same in per-
centage, with mixed flow of Al/Cu materials throughout the
nugget zone, and grain size variation in the welding nugget
[6]. The objective of their study was to find out if a defect-
free ultra-narrow multi-pass weld could be achieved by
employing pulse current gas metal arc welding process
& Ario Sunar [email protected]
1 Mechanical Engineering Department, Faculty of Engineering,
Universitas Indonesia, Kampus Baru UI, Depok 16424,
Indonesia
2 Metallurgical and Materials Engineering Department, Faculty
of Engineering, Universitas Indonesia, Kampus Baru UI,
Depok 16424, Indonesia
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with vertically placed electrode depositing single bead per
layer in weld groove. Simultaneous effect of significant
decrease in joints’ surface depression led to welds’
geometry improvement in addition to less formation of
interfacial Fe–Al intermetallic, which were the major cause
for considerable strength improvement [5]. Ultrasonic
welding was also used to join aluminum–copper, and dif-
ferent recrystallization behavior was observed on alu-
minum and copper surface region [7]. Satpathy and Sahoo
studied microstructural and mechanical performances of
ultrasonic spot welding of aluminum to copper joint. They
found out that the tensile shear and T-peel failure load had
increased in accordance with the specifically reached
welding time [8]. A fiber laser welding process was
employed by Kuryntsev et al. to join butt austenitic steel to
commercially pure copper. The findings revealed that the
electrical resistivity coefficient of copper–SS weld was
higher than that of SS. The width of intermediate layer
between SS and copper was 41–53 lm, respectively [9].Dissimilar materials, that were a piece of 0.8 mm A6061A-
P6 and a piece of 0.5 mm SUS 304 were joined by a punch-
joined process [10]. Moreover, they also studied the ther-
moplastic process and the joining performance, parameters,
and tool geometry on the static tensile shear strength and
peel strength on the single-lap joint. Friction stir riveting
extrusion was employed to join a piece of 1 mm Al 6061 on
aluminum plates and a piece of 1.5 mm low-carbon steel
[4]. Mehta and Badheka [11] welded copper to aluminum
by employing the friction stir welding technology which
had been threatened by the preheating and cooling process.
They found out that the amount of intermetallic compounds
formed in stir area had increased because of the preheating
current, and the cooling treatment had led to a significant
intermetallic decrease.
RSW is a welding technology which can join different
kinds of metals. This welding generates heat to melt base
metal (BM) because of electrical current flow in metal
surface [12], and it depends on the metal resistivity. RSW
is generally employed in industrial sectors to join metal
sheets due to its simple welding process. Kang et al. [13]
studied fatigue properties of aural2 to aluminum alloy on
resistance spot of the welding nugget. The findings
revealed that the adhesive addition increased the nugget
size and the main fatigue crack had initiated at the edge of
the nugget on aural2 surface. RSW was used by Sun et al.
to join aluminum (AA 5754) and magnesium (AZ31)
alloys. They studied mechanical properties and
microstructures of a nugget [14]. Zhang et al. [15] opti-
mized an RSW electrode to join aluminum alloy and gal-
vanized high-strength steel. The findings revealed that the
welded joint could be achieved by optimizing the elec-
trodes due to a special weld–brazed joint, and an inter-
metallic compound layer with maximum thickness, the size
of which was about 4.0 lm was installed in the aluminumand steel interface in the welded joint. Zhang et al. [15]
welded a dual-phase 780 steel sheet the thickness of which
was 1.2 mm thickness to a dual-phase 600 steel sheet the
thickness of which was 1.5 mm using RSW. The proposed
hypothesis was that, tensile stress affected interfacial fail-
ure and shear stress affected pullout failure. RSW was
applied by Xinjian Yuan et al. [16] to join ultra-low-carbon
DC54D the thickness of which was 1.0 mm and DP600
steel the thickness of which was 1.6 mm. Austenitic
stainless steel and ferritic stainless steel sheet joined by
RSW was also studied by Bina et al. [17]. They found out
that the 9 kA welding current, the 14-cycles welding time,
and the 2.6 kN electrode force generated a 6.59 kN max-
imum load. The dissimilar spot welding resistances of a
piece of 16-Mn-high-strength steel the thickness of which
was 1.0 mm and a piece of 6063-T6 aluminum alloy plate,
the thickness of which was 1.5 mm were studied by using
different welding electrodes and welding parameters.
When the optimum welding electrode was employed, its
effects to the tensile strength went up and its effects to its
indentation ratio went down because of the temperature
distribution and weld quality improvement. Joining of less-
than-1-mm-thick metal sheets employing friction stir spot
welding (FSSW) is called micro-FSSW [18]. Papaefthy-
miou et al. [19] also studied micro-friction stir welding.
Spot welding resistance employed to join less-than-1-mm-
thick metal sheets is defined as micro-RSW [20]. Dissim-
ilar micro-resistance spot welding of Al 1100-KS 5 spring
steel has been conducted by Baskoro [20]. The welding
current effects on micro-properties were very slight;
moreover, the welding current highly depended on the size
of the nugget [21]. This study investigated micro-RSW to
join dissimilar stainless steel 301(SS301) materials and
aluminum alloy 1100 (AA1100), where welding parame-
ters of micro-RSW significantly influenced the nugget
quality.
Joining dissimilar metals has still created not only
mechanical problems but also problems in the thermal and
physical properties. Problems of joining dissimilar SS301
and AA1100 metal sheets lie on the intermetallic phase in
the joint area. Furthermore, it is more difficult to provide a
better mechanical property of welding joint in the micro-
RSW. There are not many researchers who have studied
this problem. Welding parameters are important factors to
maintain a mechanical property of welding joint. Welding
parameters affect the melting processes of both SS301 and
AA1100 where the thermal and physical properties differ.
A micro-RSW for a piece of SS301 sheet and a piece of
AA1100 sheet is interesting topics to study. The mechan-
ical properties have been studied by employing the tensile
test and fractographic and microstructure analysis.
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2 Methods of Experiments
2.1 Materials
Two materials employed in this study were a piece of
200-lm-thick stainless steel 301 sheet and a piece of400-lm-thick aluminum alloy 1100 sheet. The chemicalcompositions of both materials are shown in Table 1.
American Welding Society (AWS) is an American
welding association whose members consist of practition-
ers, scientists, and researchers who are experts in welding.
Welding technology is very broad and has unique charac-
teristics. And by using the standard testing process from
AWS, it will get more precise or more valid results [22].
Both materials were then cut according to AWS dimension
standard [23] that was 76 mm in length, 19 mm in width,
and 19 mm in overlap. Schematic of welded specimen is
shown in Fig. 1. The specimens were subsequently washed
by acetone solution. The detail of experimental works has
been outlined elsewhere [22].
2.2 Welding Process
Specimens were welded by RSW machine with AC
230/240 V, ? 15%, - 20% single-phase input voltage, 65
kA input current, and 8 kA maximum welding current. An
overlap joint was employed for the joining design, where
SS301 was placed on top of AA1100. This study employed
5 kA and 8 kA as welding current and varied the welding
time of 6, 8, and 10 cycle time (CT) as specimen code
shown in Table 2. Welding force and holding time were
assumed constant. Each welding parameter used 30 spec-
imens; 27 specimens were characterized with tensile tests
and fractographic analysis, and three other specimens were
used for microstructure analysis.
2.3 Tensile Test
Welded specimens were tensile-tested. Specifications of
machine RTF-2350 employed were as follows: 50 kN
maximum capacity, 798 mm effective stroke,
0.0005–1000 mm/min crosshead speed, ± 0.1% speed
accuracy, and load measurement accuracy of 0.5% of
indicated value. The data of tensile-test was recorded by
the machine computer, and the data was saved in Excel
format. The resultant data represented the effects of load
and elongation.
Because the area and the thickness of weld nugget was
so thin, therefore the setting parameter of tensile test
machine [8] was crucial to get a precision result. Some
parameters were 5000 N load cell rating, 1 mm/min test
speed, maximum point, upper yield, and break point.
Tensile test was employed to measure the weld nugget’s
load and elongation.
2.4 Fractographic Analysis
A fracture on a specimen of micro-RSW after the tensile
test represented the welding joint performance. The pur-
pose of this analysis was to know the weld nugget condi-
tion, the mixing of metal melt and cooling condition
leading to the joint condition. When the mixing of both
parent metals was better, it affected the tear or fracture of
the weld nugget. The weld nugget without hole or fracture
revealed the fact that the weld nugget was brittle or the
mixing of parent metals was not good enough.
The effects of tensile test on nugget were analyzed and
measured. There were two kinds of failure: interfacial
failure and pullout failure. Interfacial failure was tensile-
tested specimens failed on both surface, and pullout failure
was tear or fracture on the weld nugget [24]. Crack or
fracture zone was analyzed on the SS301 or AA1100 side
using visualization. When the analyzed result showed a
hole, it was analyzed by image analysis using digital
microscope and then it was measured [25] by using a
software of a microscope. Gibson et al. [26] also used this
method to analyze a failed welding. The flowchart of
analyzed specimen is shown in Fig. 2.
Each hole of the tensile-tested specimen was measured
by a digital microscope; it was supported by a software
which could measure the area of the crack or fracture of
Fig. 1 Welded sample schematic
Table 1 Chemical composition of observed materials
SS301 80% Fe 0.14.5% C 18% Cr 1% Si 2% Mn 0.045% P 6-8% Ni 0.03% S
AA1100 99% Al 0.0008% Be 0.20% Cu 0.95% Si ? Fe 0.050% Mn 0.10% Zn – –
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tensile-tested effect [27, 28]. The fracture zone was
zoomed to 20x and a measurement result of specimen is
presented in Fig. 3.
Measurement results of specimens were summarized,
and the crack or hole on interface was analyzed and dis-
cussed. Mechanical properties were influenced by the heat
input because of the change of microstructure; therefore,
the hardness of nugget was also changed.
2.5 Micro-hardness
Specimens casted by resin were cut along the center of the
spot of weld nugget in the direction of the width of the
sample. The cross section of the weld nugget in the resin
was polished and then was etched [27, 29]. The specimens
were polished by aluminum chloride-dissolved water and
etched by nital etchant solution. Specimen preparation for
microstructure analysis is presented in Fig. 4. Specimens
were used for micro-hardness and microstructure analysis.
Metallographic preparation was performed before the
microstructure of nugget could be analyzed. Some regions
were inspected by digital microscope such as base metal,
heat-affected zone (HAZ), and intermetallic. Each region
was measured using hardness tester with the indenter load
of 25 g. The change of the microstructure was analyzed by
using SEM and EDS to know the chemical composition in
the intermetallic.
2.6 Microstructural Analysis
Microstructural analysis was employed to know the new
microstructure development of a weld nugget affected by
the melting, mixing, and cooling of micro-RSW processes.
The results of scanning electron microscope (SEM) rep-
resented different microstructure images of weld nugget
and microstructure of parent metals and also showed the
intermetallic compounds of dissimilar metal in the weld
nugget. An energy dispersive X-ray spectroscopy (EDS)
was used to measure chemical composition.
The prepared specimens were analyzed with the weld
nugget in the resin zoomed 200x by digital microscope,
and intermetallic SS301–AA1100 was analyzed. The joint
feature and chemical composition of IMC were studied.
JSM-6510 SEM of JEOL equipped with an energy dis-
persive X-ray spectroscopy (EDS) was used to study the
new microstructure and chemical composition of the nug-
get. Microstructure analysis represented the IMC and
chemical composition in the nugget.
Fig. 2 Fractographic analysisprocess
Fig. 3 Measured specimen
Table 2 Welding parameters and sample code
No. Applied welding current (kA) Cycle time (CT) Sample code
1 5 6 SS-AA-56
2 8 SS-AA-58
3 10 SS-AA-510
4 8 6 SS-AA-86
5 8 SS-AA-88
6 10 SS-AA-810
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3 Result and Discussion
3.1 Maximum Load
In order to reveal the mechanical properties of the weld
nugget, maximum loads have been measured by a tensile
test machine. Maximum load of the 27 tested specimens of
each welding parameter combination is shown in Table 3.
The tensile test results of each parameter combination
have been analyzed. Each welding parameter (six combi-
nations) consists of 27 tested specimen results. The highest
and lowest results show the upper and lower limit of test
results, respectively. The lowest load and elongation curve
is presented in Fig. 5.
Figure 5 shows that the elongation of all observed
samples is less than 1 mm and the weld breaking point is
close to the maximum load. For example, the lowest
maximum load of SS-AA-56 and SS-AA-810 have an
elongation length less than 0.2 mm. Figure 5 exhibits
106.9 N maximum load and 0.14 mm elongation of SS-
AA-56. The rupture of weld nugget or the break point is on
maximum load point. Maximum load point of SS-AA-58 is
145.6 N when the elongation point is 0.08 mm and the
break point occurs at 0.08 mm elongation. SS-AA-510
obtaining the lowest maximum load is 126.7 N and the
elongation is 0.08 mm. The weld joint of SS-AA-86 sep-
arates at 0.1 mm elongation and at a load of 140.9 N. It is
the lowest maximum load for SS-AA-86. SS-AA-88 shows
that the maximum load is 156.9 N and elongation is
0.08 mm, where this elongation resembles with SS-AA-
510, in maximum load position. Figure 5 explains that SS-
AA-810 shows 152.3 N maximum load and 0.1 mm
elongation.
Figure 6 presents the highest maximum load of 27
specimens for each welding parameter. The maximum load
of SS-AA-56 at 196.4 N is the highest load of all the
specimen, and the break point is at 0.26 mm elongation.
The highest maximum load of SS-AA-58 and elongation
value are 251.9 N and 0.18 mm. It shows that break point
is near maximum load point. The highest maximum load
for SS-AA-58 in Fig. 6 appears like the lowest maximum
load for SS-AA-58 in Fig. 5, which is the break point in
maximum load point. Figure 6 shows that the highest
maximum load of SS-AA-510 is 187.7 N with the elon-
gation of 0.225 mm, and the elongation at the break point
is 0.385 mm. SS-AA-86 leads to 211.4 N maximum load
when the elongation value is 0.219 mm, and it exhibits
break point at 0.238 mm. The highest maximum load for
SS-AA-88 presented is 260.3 N at an elongation of
0.235 mm and break point is on elongation length of
0.32 mm. The highest maximum load of SS-AA-810 is
obtained as 244 N when elongation is 0.199 mm which
also shows its break point.
Figure 6 reveals that the highest of SS-AA-510 and the
highest of SS-AA-88 have long elongation in the weld
nugget. Figures 5 and 6 explain the break point near the
maximum load value. It shows that the nugget of SS301
and AA1100 weld by micro-RSW is brittle. SS301 is low-
carbon steel, and Fe composition leads to brittle weld in the
nugget when a joint of SS301–AA1100 melts and then cool
down to room temperature. Cooling process affects
microstructure composition.
The average values of the lowest and the highest max-
imum load of each weld parameter are measured for easy
analysis of maximum load trend of each weld parameter.
The highest, lowest, and average maximum loads are
shown in Fig. 7.
The maximum load of welding time 6 CT at 5 kA and 8
kA is lower than 8 CT and 10 CT. Maximum load at
welding time 8 CT tends to increase; the significant
increase is highest for 8 kA. Maximum load at welding
time 10 CT tends to decrease; maximum load at welding
time 10 CT for 5 kA decreases significantly. This trend is
similar with Xinjian Yuan et al. This result can be inter-
preted that welding time from 6 CT to 10 CT at 5 kA and
welding time more than 8 CT at 8 kA leaded to heat input
Fig. 4 Microstructure sample preparation and analysis process
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which spread in spot. Welding time 10 CT at 5 kA and 8
kA or more affect overlarge indentation [16]. Optimized
welding time and welding current combination influence
mechanical properties.
3.2 Fracture Analysis
Weld nugget performance can be studied by fracture on
weld nugget when the load rupture the weld joint. Tensile-
test damages in steel-aluminum joint, can be studied about
Fig. 5 Lowest peak load of each welding parameters Fig. 6 Highest peak load of each welding parameters
Table 3 Peak load of tensile test results in newton (N)
SS-AA-56 SS-AA-58 SS-AA-510 SS-AA-86 SS-AA-88 SS-AA-810
155.39 183.16 126.67 160.57 156.90 178.76
158.35 178.11 151.06 184.81 224.43 152.34
150.38 155.29 174.02 180.25 198.37 163.64
133.59 157.77 131.83 184.64 204.32 234.51
121.71 154.64 154.94 194.14 188.05 152.42
160.48 149.23 137.81 158.31 215.63 207.37
146.14 218.56 187.70 161.02 181.93 163.90
106.87 206.05 175.75 156.14 193.65 167.18
137.59 159.43 173.70 168.55 241.90 194.93
129.15 145.62 148.68 162.58 231.19 175.18
142.45 231.84 171.85 162.12 177.87 216.24
161.62 160.62 161.15 204.46 211.97 228.57
115.26 214.48 178.04 204.46 215.75 208.78
196.40 211.35 172.93 157.56 175.00 170.24
128.64 210.22 164.51 157.56 225.12 170.24
146.98 148.76 162.65 159.44 188.49 158.23
163.16 251.89 178.41 152.93 193.48 161.66
146.72 216.65 170.62 176.84 260.26 244.06
142.93 249.76 143.66 141.00 165.76 195.94
134.80 226.85 172.38 184.79 197.35 159.22
154.23 170.08 138.96 143.90 217.07 205.48
142.01 215.26 171.24 187.43 206.58 157.56
151.73 217.95 184.61 140.42 204.20 235.87
177.35 195.15 166.23 208.89 170.76 200.31
143.49 162.43 150.81 153.76 194.34 229.52
115.97 154.56 176.24 209.74 199.05 195.03
175.63 181.14 139.67 182.69 190.14 193.68
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the fracture condition to get information about the ductility
of weld nugget. Weld parameters of twenty-seven speci-
mens have been tensile-tested, and the specimens break
into two pieces: aluminum and steel. So 54 pieces of alu-
minum and steel have been analyzed and examined by a
digital microscope. The result of measurement and analysis
shows that not all specimens are broken or have a hole. The
rupture of specimens and their measured fracture area are
shown in Figs. 8, 9, 10, 11, 12, and 13.
The fracture condition is not only on stainless steel side
but also on aluminum side. Fig. 8 reveals area and condi-
tion of fracture on each rupture specimens. In SS-AA-56
four pieces out of 54 pieces leads to fracture on only alu-
minum side. The fracture areas on four specimens are
0.372 mm2, 0.428 mm2, 0.323 mm2, and 1.102 mm2, and
the fracture conditions are revealed in Fig. 8.
The specimen code of SS-AA-58 with the welding
process of 5 kA and 8 CT produces fracture on seven
pieces of specimens. The fractured positions are four pieces
on aluminum and three pieces on stainless steel. The
fracture areas of the aluminum side are 0.752 mm2,
1.110 mm2, 0.066 mm2, and 0.026 mm2, and the fracture
conditions are shown in Fig. 9a–d. The fracture areas and
fracture condition of the fractures on the steel side are
exhibited in Fig. 9e–g and the fracture areas of three
specimens are 0.122 mm2, 0.62 mm2, and 0.066 mm2.
At welding parameter of 5 kA and 10 CT (SS-AA-510),
eleven pieces of fractured specimens are obtained, where
seven pieces are on aluminum side and four pieces are on
steel. The fracture condition of each piece is shown in
Fig. 10. Figure 10a–g show the fracture area on aluminum
side with the fracture areas of 1.054 mm2, 0.420 mm2,
1.131 mm2, 0.871 mm2, 0.407 mm2, 0.356 mm2, and
0.496 mm2, respectively. And in Fig. 10h–k, the fracture
area on the steel side have areas of 0.159 mm2, 0.162 mm2,
0.093 mm2 and 0.067 mm2, respectively.
The area and fracture conditions due to 8 kA and 6 CT
welding parameter in SS-AA-86 are presented in Fig. 11a–
g. There only two pieces are only fractured on aluminum
side and five pieces are fractured on steel side. The fracture
areas of 0.132 mm2 and 0.175 mm2 are on the aluminum
side and the fractures areas on the steel are 0.209 mm2,
0.187 mm2, 0.059 mm2, 0.071 mm2, and 0.067 mm2.
Fig. 7 Average of lowest and highest maximum load. a Maximum load at 5 kA, b Maximum load at 8 kA
Fig. 8 Ruptured area on AA1100 side
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Fig. 9 Ruptured area on AA1100 and SS301 side
Fig. 10 Fracture area on AA1100 is larger than SS301 side
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The fracture condition and fracture area of 8 kA welding
current and 8 CT welding time as in SS-AA-88 is presented
in Fig. 12a to 12e. The fractured aluminum is only in two
pieces with areas of 0.772 mm2 and 0.195 mm2. Fracture
areas of 0.063 mm2, 0.095 mm2, and 0.034 mm2 are on
steel side.
Fracture condition and fracture area of SS-AA-810 are
presented in Fig. 13a–h; four pieces are on aluminum side
with fracture areas of 0.256 mm2, 0.434 mm2, 0.155 mm2,
and 0.117 mm2, and the fracture area on the steel seed are
0.166 mm2, 0.017 mm2, 0.107 mm2, and 0.015 mm2.
These results may be attributed to the welding current
and welding time leading to heat input used to melt base
metal; melting zone rises when welding current is
increased or with additional welding time. Microstructure
changes in SS301 also affect the brittleness on SS301
Fig. 11 Fracture position on SS301 and AA1100
Fig. 12 Fracture area and crack on AA1100 and SS301
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surface side. It can be interpreted in two aspects. Firstly
increased heat input produces large melt of both metal [30];
AA1100 is ductile, so fracture area is larger. Second, IMC
increases; it influences to easy crack.
3.3 Micro-hardness Analysis
Hardness properties affect the brittleness properties. Micro-
hardness analysis of nugget developed by AA1100 with
SS301 is present in Fig. 14.
The hardness of nugget can be measured using Vickers
method. Vickers hardness values from each zone are
measured and shown in Fig. 14. This figure represents the
hardness values of weld nuggets that are welded with
welding current of 5 kA and 8 kA and welding times of 6,
8, and 10 CT. Specimen code represents the materials,
welding current, and welding time. The indentation areas
of hardness testing are on stainless steel 301 side, HAZ in
the stainless steel side, intermetallic compound, HAZ of
the aluminum alloy AA1100, and aluminum alloy AA1100
side.
Figure 14 shows that hardness values of HAZ areas tend
to increase not only in the SS301 sides but also in the
AA1100 side. Hardness of intermetallics also tends to
increase; however, in two specimens they tend to decrease.
Hardness of HAZ in the stainless steel which is welded
with welding current of 5 kA and welding time of 6 CT
decreases, when the value is 290 HV compared to base
metal of 314 HV. In welding current of 5 kA and welding
time of 8 CT, the hardness value in HAZ of SS301
increases; moreover, with welding current of 8 kA, the
hardness value of HAZ of SS301 increases more. Hardness
values of intermetallic tend to increase. Especially the
hardness value with the welding current of 5 kA and
welding time of 10 CT and with welding current of 8 kA
and welding time of 10 CT are 373 HV and 327 HV,
respectively. These are higher than the hardness of base
metal. HAZ in AA1100 sides significantly increases than
hardness values of base metals. The average hardness value
of HAZ in AA1100 is 92 HV.
The heat input of welding process affects the changing
of microstructure around the weld nugget. When the
welding current increases from 5 to 8 kA, the hardness of
HAZ also increases; it shows that welding current improves
Fig. 13 Rupture and crack on AA1100 and SS301
Fig. 14 Results from micro-hardness measurement in the weldnugget
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the heat input, so it makes the HAZ area wider. The
developed intermetallic has the hardness value higher than
the base metals. With the increase in the micro-hardness of
intermetallic compound, the brittle properties also
increases.
3.4 Microstructure Analysis
Microstructure of the dissimilar material’s nugget is
important to develop and to create a better welding joint.
This article have also studied the microstructure of nugget
condition or intermetallic between SS301 and AA1100 in
the nugget that has been analyzed by SEM and EDS.
Fig. 15 Intermetallic in the nugget and EDS specimen location for 5 kA
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Nugget condition of each welding process parameter is
shown in Fig. 15. The chemical composition of IMC in the
nugget is shown in Table 4.
Figure 15a presents the SEM image of SS301 and
AA1100 joint welded by current 5 kA and time of welding
6 CT and producing an IMC layer. The IMC layer is clearly
visible. Figure 15b shows the EDS result bringing out the
chemical composition of the material. Elements, such as O,
Al, Cr, and Fe are detected. It is also observed that O
concentration is similar to that of Al. Figure 15c shows a
weld joint between SS301 and AA1100, joined by welding
current of 5 kA and welding time of 8 CT; the IMC layer is
not clear enough. Elemental chemistry of Al dominates,
and it is represented in Fig. 15d. In Figure 15e, a joint has
been welded by welding current of 5 kA and welding time
of 10 CT. It leads to the highly visible IMC layer. Fig-
ure 15f represents the elemental composition such as O,
Al, Cr, and Fe in IMC.
Figure 16a shows that the IMC layer with 8 kA welding
current and 6 CT welding time process is clearly visible.
Figure16b shows elements such as O, Al, Cr, and Fe.
Welding current and welding time of 8 kA and 8 CT
respectively affect the IMC layer. It is represented in
Fig. 16c. The IMC layer obtained form joining, by using 8
kA welding current and 10 CT welding time is the widest
one. Figure 16b, d, f shows the elemental composition of
Al, O, Cr, and Fe. C only appears in Fig. 16d. SS301 has
Fe, C, and Cr and Al dominates the composition in
AA1100. Aluminum tends to oxidize with oxygen to form
an alumina layer (Al2O3) [31–33]. Alumina affects the
intermetallic, which contains oxygen. This phenomenon is
influenced by the welding current, where the increase in
welding current leads to the growth of an IMC layer.
Table 4 shows that chemical composition of IMC in the
nugget of SS-AA-56 is strongly dominated by Fe; the
weight of Fe is 88.85% and Al is only 1.64%. Intermetallic
of SS-AA-58 has chemical composition of 76.04% Al and
14.37% Fe. While in the chemical composition of the IMC
layer in SS-AA-58 nugget, the composition of Al much
more than others. Chemical composition of Al and Fe in
the IMC of SS-AA-510 are 47.77% and 38.52%, and the
EDS does not detect Cr and C. In the IMC of SS-AA-86,
the portion of Al and Fe are similar, namely 40.5% and
46.34%. In chemical composition of SS-AA-88, portion of
C is higher than others where Al is of 0.58% only and Fe is
of 17.13%. Fe and Al portions in IMC in the SS-AA-810
nugget are similar: 45.67% Al and 40.97% Fe. Comparison
of chemical composition of AA1100 in the nugget with
AA1100 BM, it can be explained that Al portion decreased
from 99% in base metal to 83.67% in the nugget. In SS301,
the portion of Fe in base metal is 81% which become
87.58% in nuggets, with a 6.58 percent increase.
Microstructure of nugget reveals that the SS301 and
AA1100 joint welded by micro-RSW grow intermetallics
of both metals. The welding parameters affect the heat
input which leads to weld zone and changes chemical
composition. Joining interface of steel and aluminum
develops IMC that affects the mechanical properties of the
nugget.
4 Conclusions
This report reveals the study of mechanical properties and
microstructure analysis of SS301–AA1100 nugget of
micro-RSW. The following conclusions are obtained from
experimental results and discussions.
1. Joining dissimilar metals in the form of thin plates of
SS301 and AA1100 can be successfully produced by
micro-resistance spot welding.
2. Tensile test represents the break point of maximum
load. The highest of SS-AA-510 and the highest of SS-
AA-88 only have long elongation in the weld nugget.
Table 4 Chemical composition in the nugget and base metal
Specimen Al Fe Cr C O others
SS-AA-56 1.64 88.85 6.87 0 2.64 0
SS-AA-58 76.04 14.37 1.68 0 7.91 0
SS-AA-510 47.77 38.52 0 0 9.24 4.47
SS-AA-86 40.5 46.34 5.81 0 7.31 0.04
SS-AA-88 0.58 17.13 1.3 66.86 14.13 0
SS-AA-810 45.67 40.97 5 8.36 0
AA1100 in the nugget 83.67 11.19 0 0 5.14 0
SS301 in the nugget 0.81 87.58 11.61 0 0 0
AA1100 BM 99 0.95 0 0 0 0.05
SS301 BM 0 81 18 0.14 0 0.86
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A break point near maximum load value is brittle joint.
SS301 is low-carbon steel; its Fe composition influ-
ences the weld nugget when a joint of SS301–AA1100
melts and then brought down to room temperature by
the cold process.
3. Tensile test also shows effects of welding parameters
to peak load. SS-AA-88 and SS-AA-58 have 260.3 N
and 251.9 N peak loads. However, SS-AA-510 has the
lowest peak load of 195.9 N. The peak load mentioned
above explains that combination of welding current
and time influence the peak load. Welding time
between 6 CT and 10 CT at 5 kA and welding time
more than 8 CT at 8 kA increases the heat input
spreading in various spots. Welding time 10 CT at 8
Fig. 16 Intermetallic in the nugget and EDS specimen location from 5 kA
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kA or more results in overlarge indentation. Optimized
welding time and welding current combination affect
the nugget performance.
4. Fractographic analysis explains a nugget fracture size
of each welding parameter. The average fracture area
of 5 kA and 10 CT in aluminum side is 0.676 mm2,
and the average area of stainless steel is less than
0.2 mm2. Increased heat input produces the rising melt
of both metals; AA1100 has such ductility that the
fracture area is larger than that of SS301. Ferro
composition affects the microstructure change, so it
easily cracks.
5. Micro-hardness of HAZ of SS301 sides increases and
micro-hardness of intermetallic tend to increase;
however, the micro-hardness of weld nugget welded
by welding time of 10 CT and welding current of 5 kA
and 8 kA decrease. The hardness of HAZ in AA1100
sides increases and the hardness significantly increases
in intermetallic or IMC.
6. Microstructural analysis by SEM and EDS conclude
that the thin stainless steel and aluminum joined by
micro-RSW grow intermetallics of both metals.
Increased welding current affects the IMC improve-
ment. It also affect the mechanical properties such as a
brittle nugget. Chemical composition of IMC nugget is
dominated by Fe and Al; however, Fe portion increases
in the nugget zone.
Acknowledgement The authors would like to extend a lot ofappreciation to the Ministry of Research and Technology and Higher
Education for its financial support through the PTUPT program with
contract number of 488/UN2.R3.1/HKP05.00/2018.
References
1. Dong L, Chen W, Hou L, Liu Y, and Luo Q, J Mater Process
Technol 238 (2016) 325.2. Sun M, Niknejad S T, Zhang G, Lee M K, Wu L, and Zhou Y,
Mater Des 87 (2015) 905.3. Piccini J M, Svoboda H G, Proc Mater Sci 9 (2015) 504.4. Evans W T, Cox C, Gibson B T, Strauss A M, and Cook G E, J
Manuf Process 23 (2016) 115.
5. Ezazi M A, Yusof F, Sarhan A A D, Shukor M H A, and Fadzil
M, Mater Des 87 (2015) 105.6. Sahu P K, Pal S, Pal S K, and Jain R, J Mater Process Technol
235 (2016) 55.7. Wu X, Liu T, and Cai W, J Manuf Process 20 (2015) 515.8. Satpathy M P, and Sahoo S K, J Manuf Process 22 (2016) 108.9. Kuryntsev S V, Morushkin A E, and Gilmutdinov A K, Opt
Lasers Eng 90 (2017) 101.10. Huang Z, and Yanagimoto J, J Mater Process Technol 225 (2015)
393.
11. Mehta K P, and Badheka V J, J Mater Process Technol 239(2017) 336.
12. Ighodaro O L, Biro E, and Zhou Y N, J Mater Process Technol
236 (2016) 64.13. Kang J, Chen Y, Sigler D, Carlson B, and Wilkinson D S, Eng
Failure Anal 69 (2016) 57.14. Sun D, Zhang Y, Liu Y, Gu X, Li H, Mater Des 109 (2016) 596.15. Zhang H, Qiu X, Bai Y, Xing F, Yu H, and Shi Y, Mater Des 63
(2014) 151.
16. Yuan X, Li C, Chen J, Li X, Liang X, and Pan X, J Mater Process
Technol 239 (2017) 31.17. Bina M H, Jamali M, Shamanian M, Sabet H, Int J Adv Manuf
Technol 75 (2014) 1371.18. Baskoro A S, Suwarsono, Kiswanto G, and Winarto, Appl Mech
Mater 493 (2014) 739.19. Papaefthymioua S, Goulas C, and Gavalas E, J Mater Process
Technol 216 (2015) 133.20. Baskoro A S, Muzakki H, Winarto, Appl Mech Mater 842 (2016)
120.
21. Wan X, Wang Y, and Zhang P, J Mater Process Technol 214(2014) 2723.
22. Baskoro A S, Muzakki H, Kiswanto G, and Winarto, Int J
Technol 7 (2017) 1306.23. Baskoro A S, Muzakki H, and Winarto, ARPN J Eng Appl Sci 11
(2016) 1050.
24. Kianersi D, Mostafaei A, and Amadeh A A, Mater Des 61 (2014)251.
25. Krajcarz F, Gourgues-Lorenzon A-F, Lucas E, and Pineau A, Int
J Fract 181 (2013) 209.26. Gibson B T, Ballun M C, Cook G E, and Strauss A M, J Manuf
Process 18 (2015) 12.27. Xu H, Xu M J, Yu C, Lu H, Wei X, Chen J M et al, J Mater
Process Technol 240 (2017) 162.28. Razmpoosh M H, Shamanian M, Esmailzadeh M, Mater Des 67
(2015) 571.
29. Li Y, Zhang Y, Bi J, Luo Z, Mater Des 83 (2015) 577.30. Zhang W, Sun D, Han L, and Liu D, Mater Des 57 (2014) 186.31. Seli H, Noh M Z, Ismail A I M, Rachman E, and Ahmad Z A, J
Alloys Compd 506 (2010) 703.32. Li P, Li J, Dong H, and Ji C, Mater Des 127 (2017) 311.33. Uday M B, Fauzi M N A, Zuhailawati H, and Ismail A B, Mater
Sci Eng A 528 (2011) 1348.
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Mechanical Properties and Microstructures on Dissimilar Metal Joints of Stainless Steel 301 and Aluminum Alloy 1100 by Micro-Resistance Spot WeldingAbstractIntroductionMethods of ExperimentsMaterialsWelding ProcessTensile TestFractographic AnalysisMicro-hardnessMicrostructural Analysis
Result and DiscussionMaximum LoadFracture AnalysisMicro-hardness AnalysisMicrostructure Analysis
ConclusionsAcknowledgementReferences