Arch. Metall. Mater.

66 (2021), 3, 887-892

DOI: 10.24425/amm.2021.136394

1 1* 2 3
A. Mohan Kumar , R. Rajasekar , V. Karthik , S. Kheawhom

Optimization of Process Parameters of Ultrasonic Welding

on Dissimilar Metal Joints

Nowadays the automotive industry mostly prefers innovative solid-state welding technologies that would enable to welding of
lightweight and high-performance materials. In this work, 3105-H18 Aluminium alloy (Al) and pure Copper (Cu) specimens with
0.5 mm thickness have been ultrasonically welded in a dissimilar (Al-Cu) manner. Optimization of process parameters of ultra-
sonic welding has been carried out through full factorial method, three levels of variables considered for this experimental studies
namely, weld pressure, amplitude, and time, also each variable interaction with welding strength has been studied. Additionally,
micro-hardness and microstructure investigation in welded joints has been studied. The result shows that the weld strength greatly
influenced weld amplitude at a medium and higher level of weld pressure. The interface micro-hardness of the welded joint has
lower compared to the base metal.
Keyword: 3105-H18 aluminium alloy, pure copper, ultrasonic welding, optimization, micro-hardness

1. Introduction to weld in conventional welding process. Fusion welding used

for welding dissimilar metals is difficult due to their difference
Ultrasonic welding process is one of faster welding process, of mechanical and physical properties [9]. Due to specific ad-
compared to laser and friction stir welding [1,2] material loss vantages of ultrasonic welding, it has used for welding dissimilar
is very minimum and also it needs minimum energy compare metals especially aluminium based metals. Ultrasonic welding
to resistance spot welding [3,4]. Owing to the many advantages is one of solid state welding process, in which similar or dis-
of ultrasonic welding, it becomes more appropriate for dis- similar metals can be weld by applying vibration and pressure
similar metal joints especially aluminium and copper, which shown in Fig. 1. The major advantages of ultrasonic welding are
are applicable to aerospace industries. High-power ultrasonic temperature developed during welding and time taken to finish
welding have highly preferable for dissimilar metals, due its joining process are very minimum without effecting properties
ability to weld thicker metals. However, intermediate compound of the materials [10].
layer found during welding process at the aluminium and copper
interface, it reduces welding quality and mechanical properties.
Recent researchers found that the Al and Zn interlayer improved
ultrasonic welding quality of Al-Cu [5].
The applications of 3105-H18 aluminium alloys are auto-
motive parts, household applications etc. Salifu et al. analyzed
the hybrid material (3105-H18 aluminium and carbon-epoxy)
used in automotive component [6]. Few researches has carried
out on welding of dissimilar metals due to their application
in various fields namely, automotive, electric power industry,
aerospace industry etc., [7,8]. In previous researches, friction stir
welding mostly used for aluminium based metals while difficult Fig. 1. Basic principal of ultrasonic metal welding
1
School of Building and Mechanical Sciences, Kongu Engineering College, Erode, Tamilnadu, India - 638060
2
NIT, Tiruchirappalli, Department of Metallurgical and materials Engineering, Tamilnadu, India – 620015
3
Chulalongkorn University, Faculty of Engineering, Department of Chemical Engineering, Bangkok, Thailand – 10330
* Corresponding author: rajamech.mech@kongu.edu

© 2021. The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCom-
mercial License (CC BY-NC 4.0, https://creativecommons.org/licenses/by-nc/4.0/deed.en which permits the use, redistribution of
the material in any medium or format, transforming and building upon the material, provided that the article is properly cited, the
BY NC use is noncommercial, and no modifications or adaptations are made.
888
Satpathy et al. [11] investigated optimization of process machine shown in Fig. 2. Components of ultrasonic welding
parameters of ultrasonic welding during welding of aluminium machine namely, generator, converter, booster, horn, holding
and brass with 0.3mm thick. They used input parameters namely, fixture, pneumatic assembly, and start switches.
vibration amplitude, weld pressure and weld time, output pa- Tensometer is used for measuring material response under
rameters namely, Tensile shear stress, T-peel stress and weld the load applied. Horizontal microcontroller based tensometer
area. They have used full factorial method and two optimization has used for experiments. The load cell varies from 200 N
methods namely, Genetic algorithm and fuzzy logic. It has found to 20 kN, AC servo motor with drive, the load accuracy is 0.5%,
that the optimized parameters obtained from fuzzy logic was it has electronic overload stopper for load cells. Vickers micro
better than Genetic algorithm. Few researchers has been carried hardness tester has used to found hardness of the test specimen.
out research work on the parameter optimization of ultrasonic The machine modal is HVS-1000 B, digital display, test force
welding, however, no research work has been found in ultrasonic varies from 10 to 1000 kgf, and magnification ranges from 100×
welding using dissimilar metals namely, 3105-H18 Aluminium to 400×, maximum height of the specimen can be test is 75 mm
alloys and copper with specimen thickness 0.5 mm. and power supply is 220 V and 50 Hz. The microscopic model
In this work, dissimilar (Al-Cu) metals has weld by using AEI/BMM/55 type of machine has used for experiment, the
ultrasonic welding machine, full factorial design has been used ranges from 50× to 450× with illumination by Halogen lamp
and 27 experiments has conducted for each category. Control with power 20W-6V, inclined 45° and 360° rotatable.
process parameter selected for the study namely, welding pres-
sure, amplitude and weld time with three levels each. Output
parameter namely, weld strength, objective of this study is to 2.2. Specimen composition
maximize the welding strength.
The specimen composition (Aluminium Alloy 3105 – H18)
is shown in Table 1. The Manganese (Mn) content as higher than
2. Materials and methods other alloying elements and it will induce the hardness and cor-
rosion resistance but Magnesium (Mg) presents in higher alloy
2.1. Experimental setup quantity next to Mn and it will induce the toughness and ductility.
As presents of Silicon content deoxidising effect have increased.
The welding process has been carried out using ultrasonic Pure copper specimen contains minimum 99.9% copper, 0.05%
welding machine shown in Fig. 2, output power 2 kW, voltage oxygen and rest contains metal impurities.
230 V, Frequency 20 kHz, PLC controlled, Pneumatic powered

2.3. Process parameter selection

In this study process parameters selected namely, weld

pressure, amplitude and weld time with 3 level as to carry out
the interaction of each parameter on response variable as taken
as tensile strength. To optimize these welding parameters and
its levels the full factorial design of experiments methodology
was included to obtain the maximize weld strength on Al-Cu
joint. The welding parameters has selected as per trial and error
method as shown in the following Table 2.

2.4. Specimen preparation

The specimens were prepared as per the standard of ASTM

D1002 [12]. Both of material specimens has cut into the specified
dimension (65 mm × 15 mm × 0.5 mm) with overlap distance
of 15 mm. The schematic diagram of the specimen as shown in
Fig. 2. Ultrasonic welding machine Fig. 3. A Tensometer has used to determine the weld strengths,

TABLE 1
Composition of Aluminium alloy 3105 – H18

Material Mg % Mn % Fe % Si % Cu % Zn % Ti % Cr % Al %
Aluminium Alloy
0.2-0.8 0.3-0.8 0.7 0.6 0.3 0.25 0.1 0.1 Remaining
3105 – H18
 889
TABLE 2 pressure the welding strength is decreases with increase of am-
Welding process parameters & its range plitude initially due to rubbing action between the two metals.
Further increase of amplitude and welding time leads to increase
Weld pressure Amplitude Weld time
Specimen of welding strength upto 39.6 Mpa due to dispersion of mol-
(bar) (µm) (sec)
Al-Cu 6.5 6.75 7 54 56 58 2.5 2.75 3
ecules. The same trend has been followed at 6.75 bar and 7 bar
welding pressures. At 6.75 bar welding pressure, the welding
strength is decreases initially and then increases upto 46.6 Mpa
which has coupled with the computerized data storage system.
due to rubbing action of metal and dispersion of molecules dur-
The specimens has fixed by the fixture to avoid slippage due
ing welding respectively. The welding strength increases upto
high frequency shearing forces.
46.6 Mpa due to increases of welding amplitude and welding
pressure initially, the Vander-wall forces develops between the
metals may be the reason for increasing of tensile strength. The
welding time increases with increase of tensile strength initially
and then dropped due to dispersion of molecules optimum upto
2.75 s, further increases of welding time leads to decrease of
weld strength.

TABLE 3
Tensile strength of the specimen

Welding Tensile
Amplitude Weld time
S. No Pressure strength
(µm) (sec)
(bar) (MPa)
1 6.5 54 2.5 30
Fig. 3. Schematic diagram of specimen 2 6.5 54 2.75 32.3
3 6.5 54 3 30
4 6.5 56 2.5 27
5 6.5 56 2.75 29.3
2.5. Taguchi method
6 6.5 56 3 22.3
7 6.5 58 2.5 29.3
Taguchi method is one of statistical tool, which have use
8 6.5 58 2.75 39.6
to designing high quality system. To find the deviation of ex-
9 6.5 58 3 32.6
perimental and desired values, a loss function has characterized.
10 6.75 54 2.5 21.6
Three process characteristic has been used to analyze signal to 11 6.75 54 2.75 32.6
noise (S/N) ratio namely, lower-the-better, nominal-the-better 12 6.75 54 3 33.3
and higher-the-better Eq. (1). 13 6.75 56 2.5 46.6
1 n 1  14 6.75 56 2.75 30
Higher – the – better  10 log   2  (1) 15 6.75 56 3 32
n 
 i 1 yt  16 6.75 58 2.5 34.6
17 6.75 58 2.75 27.6
Here, n – Number of replication, yt – Tensile strength for i th trial. 18 7 58 3 22.5
The highest S/N ratio gives optimum process parameters 19 7 54 2.5 23.2
and lesser variation in tensile strength, hence the predicted values 20 7 54 2.75 43.3
near to the preferred target. The mean S/N ratio found average 21 7 54 3 27.6
of each level [13]. Three process parameters of ultrasonic weld- 22 7 56 2.5 32
ing has been considered as input parameters namely, welding 23 7 56 2.75 32
pressure, amplitude and weld time with three levels each. L27 24 7 56 3 37.3
orthogonal array has found to be appropriate for this study. 25 7 58 2.5 45.3
26 7 58 2.75 25.3
27 7 58 3 42
3. Result and discussion
The optimized weld strength has been obtained and tabu-
3.1. Effect of welding process parameters lated as shown in Table 3. From all combinations of welded
on tensile strength joint parameters shown in Table 3, parameters of weld pressure
6.75 bar, amplitude 56 µm, weld time 2.5 sec gives the maximum
Table 3 shows the effect of 6.5 bar pressure on welding weld strength of 46.6 MPa. The ultrasonically welded specimen
strength is various from 22.3 MPa and to 39.6 Mpa. At 6.5 bar is shown in the Fig. 4.
890
molecular attraction between the metals, further increase of weld
time leads to dispersion of molecules may be the reason for
reducing strength [14].

Fig. 6. S/N ratio for process parameters

Fig. 4. Al-Cu Welded samples

The tensile tested specimen has shown in the Fig. 5. Using 3.2. Effect of interaction of welding process parameters
the Minitab software the results were analysed, the interaction on tensile strength
of each welding parameters on weld strength has been inves-
tigated. Fig. 7. depicted that interaction of welding variables on
weld strength. From this graph at 6.5 bar of pressure and constant
increase of welding amplitude the following observation has
been described, the weld strength has dropped initially, reached
upto 24 Mpa and then increased upto 34 Mpa but at 6.75 bar
raised initially upto 37 Mpa and then dropped to 32 Mpa. At 7 bar
welding pressure, the tensile strength has increased slightly
with increase of amplitude and weld time because of high
pressure permits Vander-wall forces between the plates during
welding. At welding pressure of 6.75 bar the tensile strength
has dropped gradually with increase of weld time, in contrary,
at 7 bar welding pressure, the welding strength gradually in-
creases with increase of molecular dispersion and further in-
crease of weld time may be the reason for increasing of tensile
strength.

Fig. 5. Tensile strength tested specimen

Fig. 6. shows S/N ratio for tensile strength and it showed

that weld strength has increased with increase in pressure and
amplitude. The tensile strength rises with increase of welding
pressure, Vander-wall forces develops between the metals may
be the reason for increase bonding between the weld metals
[14]. Tensile strength increases with increase of amplitude due
to increase area for rubbing action between the two metals. The
weld strength was initially increased then dropped with increased
in weld time as shown in Fig. 6. strength increases due to the Fig. 7. Interaction plot for Tensile strength
 891
Due to the welding amplitude of 27 µm the tensile strength
has raised initially with weld time and then dropped to 30 Mpa,
in contrary at amplitude of 29 µm dropped initially and then
increased due to rubbing action of two metals. At 28 µm weld-
ing amplitude, the tensile strength has decreased with increase
of weld time, due to the variation of area for rubbing action of
two metals.

3.3. Micro-hardness Test

The micro-hardness test has carried out for the specimen

having optimum parameters namely, weld pressure 6.75 bar, am-
plitude 56 µm, weld time 2.5 sec using Vickers micro-hardness
tester and the results are shown in Table 4. The load and dwell
time used for hardness test are 200 kgf and 15 s respectively.
Here the base metal section having the higher hardness value
than intermetallic section. The results were analyzed which arise
during micro-hardness test through the Minitab software as fol-
lowing. Here the hardness values has taken from intermediate
section and at 2 points from intermediate to base material direc-
tion, which has the average interval of 0.15 mm.

TABLE 4
Fig. 9. Upper and Lower weldment
Al-Cu hardness

Interface Left side Right side

HV-27.5 HV-30.4 HV-63.5 3.4. Microscopic examination

The microstructural investigation has been carried out for

specimen having optimized process parameters as shown in
Fig. 10.
• The intermetallic diffusion occurred from both sides as
shown in Fig. 10, it implies strong bonding has been ob-
tained at optimized parameters of ultrasonic welding.
• The diffusion width is narrow in middle section and rise
in sideward direction because of plastic flow has occurred
due to higher pressure.
• The joint having more plastic flow on aluminium side
compare to copper due to its excess vacancy concentration
accelerates inter-diffusion between the metals [15].

Fig. 8. Effects of different sections in welded specimen

• Through this analyses by Minitab software the hardness

values increased with increase in distance from intermediate
section shown in Fig. 8, which implies the hardnes s value
has obtained higher in base metal section than intermediate
section.
• Also the hardness was higher in upper weldment than lower
weldment shown in Fig. 9. Fig. 10. Microstructure of Al-Cu Joint
892
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