Indian Journal of Science and Technology, Vol 8(36), DOI: 10.17485/ijst/2015/v8i36/88513, December 2015
ISSN (Print) : 0974-6846
ISSN (Online) : 0974-5645
Magnetic Pulse Welding of Two Dissimilar Materials
with Various Combinations Adopted in Nuclear
Applications
S. Kudiyarasan1* and S. Arungalai Vendan2
AMET University and Technical Group, Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI), Kalpakkam,
Kancheepuram District - 603102, Tamil Nadu, India; kudiyarasan@rediffmail.com
2
Industrial Automation and Instrumentation Division, School of Electrical Engineering, VIT University,
Vellore - 632014, Tamil Nadu, India
1
Abstract
In this paper the joining of two dissimilar metals as Al-SS, Al-Cu and SS-Cu were studied. Commonly, MPW is considered
as a non-melting process. Magnetic Pulse machine which is belong to Non-conventional technique instead of conventional
technique. Magnetic Pulse Welding (MPW) is a joining process in which lap joint surfaces of cylindrical shape metals,
such as pipes and tubes, are welded by impact, using electromagnetic forces. MPW is classified in the group of solid-state
bonding processes together with Explosive Welding (EXW). The technique has become an unique and acknowledged
welding process because it enables to join similar, as well as dissimilar metals, which is very difficult to weld by traditional
methods such as GTAW or EBW due differences in melting points etc. MPW process is very fast, produces no Heat Affected
Zone (HAZ) and may be performed without filler metals and protective gases. Nevertheless, it was detected a very thin
film (10 to 50 µm) of two welded metals in the form of intermetallic phases, in which melting and solidification processes
took place. These inter-metallic phases significantly affect the mechanical properties of the joint. The diffusion of elements
in the intermetallic phase was studied for the pattern and the composition of the blended metals and formation of pores
etc. The interface typically presents a wavy pattern and mutual diffusion of elements happens in the transition zone.
The transition zone is composed of elements intermetallics, micro cracks and micro pores as expected in our study. The
effect of the parameters on the morphology, configuration and structure of the interface has been thoroughly studied. The
weld interface composition, structure and morphology were studied by optical and Scanning Electron Microscopy (SEM).
Energy-Dispersive Spectrometry (EDS) was used in order to evaluate the local distribution of alloying elements at the joint
interface and its vicinity and also nano-hardness tests were performed across the bonding zone at regular increments.
The results of the joints were analysed for process parameters and based on the result , the process parameters has to be
reviewed accordingly to yield best interface weld results.
Keywords: Dissimilar Metals, Interfaces, Inter-Metallic Phases Transfer, Magnetic Pulse Welding, Welding
1. Introduction
The Prototype Fast Breeder Reactor (PFBR) is a 500MWe
sodium–cooled fast breeder nuclear reactor presently
being constructed by Bharatiya Nabhikiya Vidyut Nigam
Limited (BHAVINI) in Kalpakkam, India. The Indira
Gandhi Centre for Atomic Research (IGCAR) is responsible for the design of this reactor. The cooling system of
*Author for correspondence
the reactor uses liquid sodium and requires additional
safety measures to isolate the coolant from environment.
The steam generator made of modified 91 steel, is connected to the intermediate heat exchanger, made of AISI
316LN stainless steel with the dissimilar metal weld.
The schematic of the rector system is shown in
Figure 1(a) and the steam generator with the dissimilar
metal weld in Figure 1(b) currently the dissimilar metal
Magnetic Pulse Welding of Two Dissimilar Materials with Various Combinations Adopted in Nuclear Applications
power plants, an extensive failure analysis was carried out
at IGCAR on dissimilar metal welds between 2.25Cr-Mo
ferritic steel and AISI type 316 stainless steel with and
without Inconel-82 buttering using non–destruction
X-Ray Diffraction (XRD) technique and to assess the
effectiveness of the buttering on the extent of reduction
in the residual stress.
To avoid the complex design, it is proposed the two
dissimilar materials by Magnetic Pulse Welding. The
Magnetic Pulse Welding (MPW) is solid-state joining
(a)
(a)
process employed for both similar and dissimilar con(a)
ductive metal combinations viz., aluminum, brass, and
copper to steel, titanium, stainless, aluminum, magnesium copper etc. MPW system’s architecture consists of
a dedicated AC power supply, bank of capacitors, a highspeed switching system and a coil (Figure 1(c)). The
parts to be joined are inserted into the coil. The capacitor
bank is charged and the high-speed switch is activated. A
strong magnetic flux is created around the coil as per the
principle of electromagnetic flux generated in a winding
excited with an AC power supply. When the current is
applied and as a result eddy currents are formed in the
(b)
parts. The eddy currents oppose the magnetic field in the
(b)
coil as per(c)Lenz Law of Electromagnetics and an opposFigure 1. (a) Schematic (b)
of the rector system. (b) The steam generator with dissimilar
Pulse Welding
(c) metal weld. (c) Magnetic
1
ing force
generated
. This
Power
Supply
Set Upof
with
bank.(b) The steam generator with dissimilar
Figure
1. (a)
Schematic
the capacitor
rector system.
metalisweld.
(c) Magnetic
Pulse force
Weldingdrives the materials
Power Supply Set Up with capacitor bank.
together at a tremendous high rate of speed and creates
The schematic of the rector system is shown in Figure 1(a) and the steam generator with the dissimilar metal weld in Figure 1(b)
weld (Figure Tungsten
2).
theofdissimilar
weld
is a tri-metallic
transition
joint
andgenerator
uses a multi–pass
Inert Gas
welding
Thecurrently
schematic
the rectormetal
system
is shown
in Figure 1(a)
and the
steam
with the dissimilar metal
weld(TIG)
in Figure
1(b) the
When
a filler
highmaterial
magnetic
field
BNi
isandsuddenly genercomplex
of the
jointweld
was is
necessary
to minimize
thermal
stresses.
is an
with
16%
Cr 8%
currently
thedesign
dissimilar
metal
a tri-metallic
transition
joint and
uses ER16-8-2
a multi–pass
Tungsten
Inert
Gas
(TIG)
welding
the
2% Mo,
usedoffor
austenitic
stainless
steels,
alloyER16-8-2
800 is anis Inconel
withwith
very
good
creep
complex
design
the high
joint temperature
was necessary
to minimize
thermal
stresses.
an penetrated
filler alloy
material
16%
Cr 8%
Ni rupture
andthe eddy currents
ated
and
into
metal,
then
600temperature
Inconel 182austenitic
is an electrode
in alloy
dissimilar
metal
welds ofalloy
stainless
steel good
joinedcreep
to carbon
2%properties
Mo, used above
for high
stainlessused
steels,
800 is
an Inconel
with very
rupturesteel
(current
passjoined
through
them
experience
with600
dissimilar
weld
has shown
a considerable
number
ofstainless
failures Ioccurred
at a to
very
early
stage
in as a result, an
properties
above
Inconelmetal
182 is
an joints
electrode
used inthat
dissimilar
metal
welds ofdensity
steel
carbon
steeland
service than
powerhas
plants,
anthat
extensive
failure analysis
carriedoccurred
out at IGCAR
onearly
dissimilar
metal
experience
with expected,
dissimilarespecially
metal weldinjoints
shown
a considerable
number was
of failures
at
aFvery
stage
inmainly on the base
electromagnetic
force
of
=
I
×
B
acts
weldsthan
between
2.25Cr-Mo
ferritic
steel plants,
and AISI
316 stainless
steel with
without
buttering
using
non–
service
expected,
especially
in power
an type
extensive
failure analysis
wasand
carried
out atInconel-82
IGCAR on
dissimilar
metal
it is Inconel-82
accelerated
away
fromnon–
thethecoil and collides
destruction
Diffraction
technique
and to
assess
the effectiveness
ofand
the
buttering
on the extent
of reduction
in
welds
betweenX-Ray
2.25Cr-Mo
ferritic(XRD)
steel and
AISI type
316
stainless
steelmetal
with and
without
buttering
using
residual stress.
destruction
X-Ray Diffraction
of the with
buttering
the extent
of reduction
in the current I and the
(c)(XRD) technique and to assess the effectiveness
rapidly
theontarget
metal.
The eddy
(c)
residual stress.
rector system. (b) The steam generator
with
dissimilar
metal
weld.
(c)
Magnetic
Pulse
Welding
magnetic
pressure
p are given
as following:
avoid
the complex
it is proposed
the two
by Magnetic
Pulse Welding.
The Magnetic
Pulse
Figure 1. To (a)
Schematic
of design,
the rector
system. (b)
Thedissimilar
steam materials
acitor bank.
is solid-state
process
employed
for both
similar
dissimilar
conductive
combinations
To Welding
avoid the(MPW)
complex
design, it isjoining
proposed
the two
dissimilar
materials
byand
Magnetic
Pulse
Welding.metal
The Magnetic
Pulseviz.,

the coil
as per
Lenz
of Electromagnetics
and an opposing force is generated1. T
generator
with(MPW)
dissimilar
metaljoining
(c) Magnetic
Pulse
aluminum,
brass,
and copper
to weld.
steel,process
titanium,
stainless,for
aluminum,
magnesium
copper
etc.
MPWLaw
system’s
architecture
Welding
is solid-state
employed
both similar
and dissimilar
conductive
metalcombinations
viz.,
 ∂B consists
tremendous
high
rate
of
speed
and
creates
weld
(Figure 2).
tem is shown in Figure
1(a) and
generator
with
dissimilar
weld in aluminum,
Figure
1(b)magnesium
ofthea steam
dedicated
ACSet
power
supply,
bank metal
of capacitors,
a high-speed
switching
system
a coil
(Figure
parts to be
∆ × architecture
i 1(c)).
= −kThe
aluminum,
brass,
and
copper
to
steel,
titanium,
stainless,
copper
etc.and
MPW
system’s
Welding
Power
Supply
Upthe
with
capacitor
bank.
 ∂consists
 flux is
weld is a tri-metallic transition
and
a multi–pass
Inert
Gas bank
(TIG)
welding
areuses
inserted
into supply,
the Tungsten
coil.bank
The capacitor
chargedthe
and
the high-speed
activated.
strong
of joint
ajoined
dedicated
AC
power
of capacitors,
aishigh-speed
switching
systemswitch
and a is
coil
(Figure A
1(c)).
Themagnetic
partst to
be
s necessary to minimize thermal
stresses.
ER16-8-2
is an
filler
material
with
Cr 8% Niand
and
created
around
the
as
perThe
the
principle
of16%
electromagnetic
flux
generated in
a winding
excitedAwith
anmagnetic
AC power
supply.
joined
are inserted
intocoil
the
coil.
capacitor
bank
is charged
the high-speed
switch
is activated.
strong
flux
is
rature austenitic stainless
steels,
alloy
is transition
anis Inconel
alloy
very
good
creep are
rupture
the800
current
applied
and
aswith
a and
result
eddy
formed
in the parts.
The eddyexcited
currents
oppose
thepower
magnetic
field in
weld is
a When
tri-metallic
joint
uses
acurrents
multi–pass
created
around
the
coil
as per the
principle
of
electromagnetic
flux
generated
in a winding
with
an AC
supply.
182 is an electrode used in
dissimilar
metal
welds ofand
stainless
steel
joined
to carbon
steelin the parts. The eddy currents oppose the magnetic field in
When
the current
is applied
as a result
eddy
currents
are formed
Tungsten
Inert
Gasnumber
(TIG)
welding
the
al weld joints has shown
that a considerable
of failures
occurred
atcomplex
a very earlydesign
stage in
ly in power plants, of
an the
extensive
was carried
out at IGCAR
on dissimilar
metal
jointfailure
was analysis
necessary
to minimize
thermal
stresses.
ritic steel and AISI type 316 stainless steel with and without Inconel-82 buttering using non–
ER16-8-2 is an filler material with 16% Cr 8% Ni and 2%
(XRD) technique and to assess the effectiveness of the buttering on the extent of reduction in the
Mo, used for high temperature austenitic stainless steels,
800 is an
Inconel
alloy with
goodThe
creep
rupture
it is proposed the alloy
two dissimilar
materials
by Magnetic
Pulsevery
Welding.
Magnetic
Pulse
joining process employed
for both
similar600
and Inconel
dissimilar conductive
combinations
properties
above
182 is anmetal
electrode
usedviz.,
in
steel, titanium, stainless, aluminum, magnesium copper etc. MPW system’s architecture consists
dissimilar metal welds of stainless steel joined to carbon
ly, bank of capacitors, a high-speed switching system and a coil (Figure 1(c)). The parts to be
. The capacitor banksteel
is charged
and the high-speed
switch is activated.
A strong
experience
with dissimilar
metal
weldmagnetic
joints flux
hasis
the principle of electromagnetic flux generated in a winding excited with an AC power supply.
shown
that
a
considerable
number
of
failures
occurred
at
d as a result eddy currents are formed in the parts. The eddy currents oppose the magnetic field in
a very early stage in service than expected, especially in
Figure 2. Magnetic Pulse Welding (MPW) principle.
Figure 2. Magnetic Pulse Welding (MPW) principle.
2
Vol 8 (36) | December 2015 | www.indjst.org
When a high magnetic field B is suddenly generated and penetrated into metal, the
Indian Journal of Science and Technology
through them and as a result, an electromagnetic force of F = I × B acts mainly on th
the coil and collides rapidly with the target metal. The eddy current I and the magneti
S. Kudiyarasan and S. Arungalai Vendan
p=
(B
d=
2
o
− Bi2
2m
) =  B  (1 − e
2
o
 
 2m
−2 x / d
)n
2
1
and k w =
wk m
LC
Where K, µ, τ, Bo and Bi are the electrical conductivity,
magnetic permeability, thickness, the magnetic flux density at lower and upper surfaces of Al, respectively. The
depth of skin effect (δ) can be obtained by calculation
of angular frequency (ω) and it is governed by the complete MPW system’s inductivity L and its capacity C. The
skin depth becomes important parameter especially for
thin metal bonding process. When the thickness of the
base metal is the same as the skin depth, then magnetic
pressure equals 85% of its maximum value and it reaches
97% when the base metal thickness is twice of the skin
depth. The appropriate skin depth and higher magnetic
pressure can be adjusted by the frequency of the discharge
­current2.
At the moment of collision the colliding surfaces can
be cleaned by a large kinetic energy getting before the collision. The velocities attained during this process range
from 250 m/s to 500 m/s and the joining process completed within microsecond. Because of the short impact
period, the extent of heating might be minimal along the
joints3. Therefore, comparing to the traditional fusion
welding process, no significant heat affected zones is
produced in MPW joints and it can be noticed as a main
advantage.
The practical limitations of MPW relate to handling
very high electrical currents. The major limitation of
MPW equipment concerns the electrical connections
between capacitors, switch, and coil. Very large metal
components cannot be formed due to problems in design
of very large coils4. It is very expensive equipment, just if
able only by important mass production18.
The experimental results and welding characteristics
for several samples such as Al-Al and Al-Fe are reported
in the available literatures already. However, Al-SS,
Al-Cu and SS-Cu tubular combination which has greater
demand in nuclear industries has been less reported with
respect to MPW process. Moreover, the metallurgical
characterization and non-destructive tests on MPW specimens in the available literatures are scanty. Hence, in this
study, an attempt is being made to weld Al-SS, Al-Cu and
SS-Cu tubular components using MPW process. Further,
mechanical testing and metallurgical ­characterizations
by destructive and non destructive methods are being
­carried out8.
2. Experimental Prior and
Procedures
The three specimens are employed in this study. However
a typical one specimen consists of Cu (Driver) and Al
(Flyer). The MPW equipment that is used in this study
has a maximum charging energy of 10 kJ, Current of
12 kA and a Voltage of 10 kV. An outer Cu pipe was
machined to be 2 mm thick, 80 mm long, and 40 mm in
diameter. An inner SS pipe 9 mm thick, 90 mm long, and
36 mm in diameter was employed. For the pipe joint, the
gap between the Cu and SS was 1mm. The specimens are
ground using emery paper to remove marks sustained
during machining. First, the voltage had to be charged
according to the welding conditions. Then welding is
carried out by electromagnetic force from discharged
current through a working coil which develops a repulsive force between the induced currents flowing parallel
and in the opposite direction in the tube14. Figure 3 shows
few typical samples dimensional diagram, specimens
after weld and cut cross section and inner weld view
respectively.
It may be observed that there is a reduction in diame8 Procedures
2. Experimental
ter in the
area of thePrior
weldand
. After welding, the work pieces
are cross
sectioned
and
prepared
forstudy.
examination
by one specimen con
The three specimens are employed
in this
However a typical
MPW
equipment that is used
in this studysuch
has a as
maximum
charging energy of 10 kJ, C
standard
metallographic
procedures
mechanical
An outer Cu pipe was machined to be 2 mm thick, 80 mm long, and 40 mm in diamete
polishing
grit andForlight
chemical
long,down
and 36 to
mm1-micrometer
in diameter was employed.
the pipe
joint, the gap between the C
ground
emerywere
paper then
to remove
marks sustained
during and
machining. First, the vo
etching.
The using
samples
examined
by optical
welding conditions. Then welding is carried out by electromagnetic force from discharg
scanning
electron
microscopy.
develops
a repulsive
force between the induced currents flowing parallel and in the o
shows few typical samples dimensional diagram, specimens after weld and cut cross sec
Figure 3. MPW specimen dimensional diagram with cut cross section and inner weld vi
Figure 3. MPW specimen dimensional diagram with cut
It may be observed that there is a reduction in diameter in the area of the weld8. A
cross section
and inner weld view.
sectioned and prepared for examination by standard metallographic procedures suc
micrometer grit and light chemical etching. The samples were then examined by optical
Vol 8 (36) | December 2015 | www.indjst.org
Microanalysis by wavelength dispersive spectroscopy was utilized to evaluate the loca
3
Indian Journal of Science and Technology
joint and its vicinity.
3. Results and Discussion
Magnetic Pulse Welding of Two Dissimilar Materials with Various Combinations Adopted in Nuclear Applications
(a)
Microanalysis by wavelength dispersive spectroscopy
was utilized to evaluate the local distribution of alloying
elements at the joint and its vicinity.
(a)
3. Results and Discussion
The welded specimens are subjected to destructive and
non destructive tests to evaluate its quality and strength.
Metallurgical characterizations are performed to analyze the bond integrity and examined for presences of
­intermetallic phases5,6.
3.1 Tensile Test
Specimen Description
Al - SS
Al - Cu
SS - Cu
Tensile Strength in kN
11.750
11.050
07.400*
During the testing specimen got broken at weld joint
*
SS-Cu dissimilar metal configuration having failed in
tensility, the improved configuration needs to be analyzed
and tested; the base parameters tested with this configuration however has provided viable results, which would
supplement further analyzing the same for testing again
for tensility. The reports of the same are enumerated in
the upcoming paragraphs.
3.2 Metallography Test
For all the three welded samples, the optical microscopic
examination was done and the results observed were as
expected in all the aspects of perfections and integrity.
First sample (Al-Cu), that was examined under optical
microscope after etching and polishing then the bonding
of two materials were verified with magnification ranging
from 10X to 100X and observed that there is no imperfections and defects noticed and integrity of both the
materials is intact6,7.
3.3 Radiography Test
Radiography tests are performed for investigating the
presence of pore/cluster of pores if any and also to ­examine
4
Vol 8 (36) | December 2015 | www.indjst.org
(b)
(b)
Welded samples are tested on a standard tensile testing
machine. In all cases, failure occurred in the region away
from the weld area. The tensile results emphasizes that
ductile failure of a welded Al-SS, Al-Cu and SS-Cu Rod/
Pipe occurs at a distant from the weld. There is no failure
on the weld interface15.
Sl. No.
1
2
3
(b)
(a)
(a)
(b)
(c)
(c)
(c)
(d)
(d)
Figure 4. (a) Specimens after Tensile test. (b) Al-SS Tensile test graph. (c) Al-Cu Tensile test graph. (d) SS-Cu
graph.
Figure 4. (a) Specimens after Tensile test. (b) Al-SS Tensile
dissimilar Tensile
metal configuration
failed in tensility,
the improvedTensile
configuration needs to be analyzed a
test graph. (c)SS-Cu
Al-Cu
testhaving
graph.
(d) SS-Cu
base parameters tested with this configuration however has provided viable results, which would supplement furt
the
same
for
testing
again
for
tensility.
The
reports
of
the
same
are
enumerated
in the upcoming paragraphs.
test graph.
3.2 Metallography Test
(c)
For all the three welded samples, the optical microscopic examination was done and the results observed were as e
the aspects of perfections and integrity. First sample (Al-Cu), that was examined under optical microscope afte
the effectiveness
the
fused
dissimilar
joints.
X-rayranging
mode
polishingof
then
the bonding
of two
materials were verified
with magnification
from 10X to 100X and obser
is no imperfections and defects noticed and integrity of both the materials is intact .
with 150KV and 10mA source is used for this study. The
3.3 Radiography Test
exposure time
was about 100 seconds and ASME Sec V is
Radiography tests are performed for investigating the presence of pore/cluster of pores if any and also to
effectiveness
of
the fused(No
dissimilar
joints. X-ray modestandard
with 150KV and 10mA
sourcein
is used for this study. The e
the standardwas
being
used
particular
given
about 100 seconds and ASME Sec V is the standard being used (No particular standard given in literatures). Fi
the post radiographic examined samples.
literatures). Figure 5 shows the post radiographic examined samples.
The results of the radiography suggest that the quality
is good and free from impurities/pores. Further, it illustrates good fusion in many samples. However, in few more
Figure 5. Al/SS, Al/Cu and Cu/SS weldment specimen subjected to radiography.
samples, the response appears to indicate lack of fusion.
The results of the radiography suggest that the quality is good and free from impurities/pores. Further, it illustrate
in many
few more
samples,radiography
the response appears to indicate
lack of
It is important
tosamples.
noteHowever,
the infact
that,
is not
a fusion. It is important to
that, radiography is not a suitable technique for solid state bonds as the thin line of interlayer’s formed at the weld
identified generally by x-ray.
suitable technique for solid state bonds as the thin line
Micro-Structural Analysis
of interlayer’s3.4 formed
at the weldment are not ­identified
Microstructures of cross sections of the different configurations of dissimilar welds are presented in Figure 6 (a), 6
generally by x-ray.
6,7
3.4 Micro-Structural Analysis
Microstructures of cross sections of the different
­configurations of dissimilar welds are presented in
Figure 6 (a), 6 (b) and 6 (c).
There is a prominent difference in the quality of welding particularly for these configurations, and in general
there is no bonding or minimal bonding in the corners
and start-end zones, however the center of the welds
showed a exemplary bonding or bond integrity. This may
be regarded as the important feature or even the very
unique feature of this type of welding. The inadequacy in
bonding at the corners of the weld zone is a typical feature
of MPW cylindrical parts and according to literature is not
critical for many applications11,12. The minimally bonded
Indian Journal of Science and Technology
S. Kudiyarasan and S. Arungalai Vendan
If the interface shows a wavy appearance, the
i­ ntermetallics mainly concentrate in so called “melt pockets”, which are mostly located at the crests of the waves
(Figure 6(a)). If EMP produces a wave less interface, the
intermetallic phases form a film
of byvarying
thickness
The wave pattern
the side of the interface
significantly depends on sample geometry and to
parameters.
Substantial
utility
of
dissimilar
specimen cylinders and relatively low pulse energ
(Figure 6(b)). It is pointed out that
the
phase
film
appears
Contrary, applying hollow dissimilar combines’ cylinders and high pulse energies pronounce
(a)
5.
the middle sectionany
of the welds
(Figure 6(c)). This geometrical influence is in accordance wi
to be interrupted by regions without
intermetallics.
(a) Al/SS, Al/Cu and Cu/SS Weldment Specimen Subjected to Radiography.
FigureFigure
5. Al/SS,
Al/Cu and Cu/SS weldment specimen
note that the wave formation process is not mandatory for a good bonding. It is furthermo
There is a prominent difference in the quality of welding particularly for these configurations, and in general there is no bonding
There is a prominent difference in the
quality of welding particularly for these configurations, and in general there is no bonding
or minimal bonding in the corners and start-end zones, however the center of the welds showed a exemplary
bonding
or bond
For
a
thickness
below
5
microns
the
intermetallics
­contain
extent
wave
formation
could
also
be observed
in regions without bonding. Circumventing the
subjected
totheradiography.
or minimal bonding in
cornersintegrity.
and start-end
of the welds
exemplary
bonding
or bond
This zones,
may behowever
regardedthe
as center
the important
featureshowed
or evena the
very unique
feature
of this type of welding. The inadequacy
at the welding interface is impossible. The extent of interface depends on the process paramete
integrity. This may be regarded as in
thebonding
important
feature
or even
theweld
veryzone
unique
this type
of welding.
The inadequacy
at the
corners
of the
is afeature
typicaloffeature
of MPW
cylindrical
parts and according to literature is not critical
in bonding at the corners of the weld
a typical feature. The
of MPW
cylindrical
parts
and according
to specimen
literature however
is not critical
any
minimally
bonded
corners
of the weld
pose undesirabilityrarely
and less adaptive
in cracks, voids or pores.
forzone
manyisapplications
structure of the interface.
for many applications . The minimally bonded corners of the weld specimen however pose undesirability and less adaptive in
11,12
11,12
corrosive environments and in the case of recurrent cycled loads.
corrosive environments and in the case of recurrent cycled loads.
If the interface shows a wavy appearance, the intermetallics mainly concentrate in so called
located at the crests of the waves (Figure 6(a)). If EMP produces a wave less interface, the i
3.5 Scanning Electron Microscopy
(SEM)
varying thickness (Figure 6(b)). It is pointed out that the phase film appears to be int
intermetallics. For a thickness below 5 microns the intermetallics contain rarely any cracks, vo
With Energy Dispersive Spectroscopy
3.5 Scanning Electron Microscopy (SEM) With Energy Dispersive Spectroscopy (EDS)
(EDS)
The SEM investigations present more information on bonding and phase formations. The SEM
shown inmore
Figure 7(a). Itinformation
may be noted that the dearth ofon
any diffusion layers leads to the postu
The SEM investigations present
involved in the phase formation and bonding process along the interface.
bonding and phase formations. The SEM of the Al-Cu
(a)
(a)
(b)(b)
(b)
There is a prominent difference in the quality of welding particularly for these configurations, and in general there is no bonding
welded specimen is shown in Figure 7(a). It may be noted
or minimal bonding in the corners and start-end zones, however the center of the welds showed a exemplary bonding or bond
integrity. This may be regarded as the important feature or even the very unique feature of this type of welding. The inadequacy
in bonding at the corners of the weld zone is a typical feature of MPW cylindrical parts and according to literature is not critical
that the dearth of any diffusion layers leads to the postufor many applications . The minimally bonded corners of the weld specimen however pose undesirability and less adaptive in
corrosive environments and in the case of recurrent cycled loads.
lation that local melting is mainly involved in the phase
The wave pattern by the side of the interface significantly depends on sample geometry and to a negligible degree on the process
formation
along
the
interface.
parameters. Substantialand
utility of bonding
dissimilar specimen process
cylinders and relatively
low pulse
energies
inhibited the wave formation.
Contrary, applying hollow dissimilar combines’ cylinders and high pulse energies pronounced waves are visible, especially in
to
the middle
section
of thelow
welds (Figure
6(c)). This energies
geometrical influencethe
is in accordance
with findings in . It is imperative
As
for
pulse
intermetallic
phases
note that the wave formation process is not mandatory for a good bonding. It is furthermore worth mentioning that to some
extent wave formation could also be observed in regions without bonding. Circumventing the formation of intermetallic phases
consist
primarily
ofextentaluminum,
itprocess
is parameters
deduced
that
at the welding interface
is impossible. The
of interface depends on the
and is fairly
connectedsolely
with the
(c)
structure of the interface.
(c)(c)viewed under the optic microscope. (b) SS-Al specimen viewed under the optic microscope. (c)
Figure 6. (a) Cu-SS specimen
aluminum
but
not
copper
was
molten
during
low
energy
If the interface shows a wavy appearance, the intermetallics mainly concentrate in so called “melt pockets”, which are mostly
Cu-Al specimen viewed under the optic microscope.
located at the crests of the waves (Figure 6(a)). If EMP produces a wave less interface, the intermetallic phases form a film of
Figure 6. (a) Cu-SS specimen viewed under the optic microscope. (b) SS-Al specimen viewed under the optic microscope. (c)
varying thickness
(Figure 6(b)).phases
It is pointed out
that formed
the phase film appears
to be interrupted
by regions
any
MPW.
Al-rich
are
under
strong
nonwithout
equiCu-Al specimen 6. viewed under
microscope.specimen viewed under the optic
Figure
(a)the optic
Cu-SS
intermetallics. For a thickness below 5 microns the intermetallics contain rarely any cracks, voids or pores.
(b)
librium
conditions.
the
sharp
and(EDS)
stepwise transition
microscope. (b) SS-Al specimen
viewed under the optic
3.5 Scanning Electron
Microscopy (SEM)From
With Energy
Dispersive
Spectroscopy
13
accordance
with
Carpenter
and
Wittman
who
deduced
thatmetals
solidis state diffusion is not i
The SEM
investigations
present
more
information
on bonding
and phase
formations.
The
SEM of
welded
specimen
(a)the­pAl-Cu
in
chemical
composition
between
the
two
arent
microscope. (c) Cu-Al specimen viewed under the optic
shown in Figure 7(a). It may be noted that the dearth of any diffusion layers leads to the postulation that local melting is mainly
the
process
of
MPW
aluminum
to
copper.
involved in the phase formation and bonding process along the interface.
microscope.
11,12
11
corners of the weld specimen however pose undesirability
and less adaptive in corrosive environments and in the
(c)
case
of recurrent cycled loads.
Figure 6. (a) Cu-SS specimen viewed under the optic microscope. (b) SS-Al specimen viewed under the optic microscope. (c)
Cu-Al specimen viewed under the optic microscope.
The wave pattern by the side of the interface significantly depends on sample geometry and to a negligible
degree on the process parameters. Substantial utility of
dissimilar specimen cylinders and relatively low pulse
energies inhibited the wave formation. Contrary, applying hollow dissimilar combines’ cylinders and high pulse
energies pronounced waves are visible, especially in the
middle section of the welds (Figure 6(c)). This geometrical influence is in accordance with findings in11. It is
imperative to note that the wave formation process is not
mandatory for a good bonding. It is furthermore worth
mentioning that to some extent wave formation could also
be observed in regions without bonding. Circumventing
the formation of intermetallic phases at the welding interface is impossible. The extent of interface depends on the
process parameters and is fairly connected with the structure of the interface.
Vol 8 (36) | December 2015 | www.indjst.org
The Sum spectra of the welded specimen clearly illustrates the % composition of Co
shown in Figure 7(b). The proportionate quantity of Aluminium is remarkably more
region and copper dominates to the right of the curve, the AL-Cu in equal proportion
shown in Figure 7(c). The mixing of the dissimilar metals at the welded joint for the 30u
the perfection of the mixing of dissimilar metals.
Al vs SS shows a moderate to low mixing of metals at the weld joint as shown in Figur
as the unique quality of MPW is clearly depicted in Figure 7(d) and similar studies has b
(a)
The bonding
(b)(b)for the 10um to 20um width of the
(a) of the SS vs Al at the welded joint
bonding in compared to Cu Vs SS.
As for low pulse energies the intermetallic phases consist primarily of aluminum, it is dedu
copper was molten during low energy MPW. Al-rich phases are formed under strong non equi
and stepwise transition in chemical composition between the two parent metals and the fo
(b)
As for low pulse energies the intermetallic phases consist primarily of aluminum, it is deduced that solely aluminum but not
copper was molten during low energy MPW. Al-rich phases are formed under strong non equilibrium conditions. From the sharp
and stepwise transition in chemical composition between the two parent metals and the formed intermetallic phases it is in
(c)
(c)
Indian Journal of Science and Technology
5
Magnetic Pulse Welding of Two Dissimilar Materials with Various Combinations Adopted in Nuclear Applications
(c)
prevalent at the intermetallic region shown in Figure 7(c).
The mixing of the dissimilar metals at the welded joint
for the 30um to 40um width of the specimen shows the
perfection of the mixing of dissimilar metals.
Al vs SS shows a moderate to low mixing of metals at
the weld joint as shown in Figure 7(d). The wavy pattern
of bonded area as the unique quality of MPW is clearly
depicted in Figure 7(d) and similar studies has been
already taken12,13,16,17.
The bonding of SS-Cu found to be imperfect, due to the applied energy being
Theinadequate
bondingforofthis
theconfiguration,
SS vs Al athowever
the welded joint for the
bonding in the range 5um-10um is observed and to make the bonding even more efficient and in line with others, the
10um tothe20um
width
of concentrated
the specimen
improvement and further study is required. The bonding was prevalent throughout
specimen
however
in theshows the little or
narrow region, which is inadequate for the tensility point of view. The bonded
zone is analyzed
with in
SEM
methodology
and
theVs SS.
moderate
bonding
compared
to
Cu
(d) 7(e).
same can be viewed in Figure
(d)
The bonding of SS-Cu found to be imperfect, due
to the applied energy being inadequate for this configuration, however bonding in the range 5um-10um is
observed and to make the bonding even more efficient
and in line with others, the improvement and further
study is required. The bonding was prevalent throughout
the specimen however concentrated in the narrow region,
which is inadequate for the tensility point of view. The
bonded zone is analyzed with SEM methodology and the
same can be viewed in Figure 7(e).
The later studies of MPW would be in this area to
further the equally distributed bonding of this SS-CU
specimens at the lower KeV as applied for the other
­samples.
Owing to short bonding time and the finite rates of
solid-state phase transformations, there is prospectus that
a thin layer on the low-melting point material fused and
alloyed with the more refractory metal. Rapid melting
and solidification explain the formation of intermetallic
(e)
phases.
(e)
Figure
7.
(a)
SEM
of
the
Al-Cu
welded
specimen.
(b)
Sum
spectra
view
of
proportionate
quantity of metals in the welded
Figure 7. (a) SEM of the Al-Cu welded specimen. (b)
portion. (c) Graphical analysis of dissimilar metals in intermetallic phase region. (d) Wavy pattern and line scanning of Al vs SS.
Sum spectra
of proportionate
quantity of metals in the
(e) SEMview
and EDS
analysis of SS vs Cu.
3.6 Nano Indentation
welded portion. (c) Graphical analysis of dissimilar metals
The later studies of MPW would be in this area to further the equally distributed
this SS-CU
specimens
at the lower
For bonding
MPW ofjoint
at the
discharge
voltage of 10kV, the
in intermetallic
phase region. (d) Wavy pattern and line
KeV as applied for the other samples.
nano
indentation
test
was
carried
out to measure the
scanning of Al vs SS. (e) SEM and EDS analysis of SS vs Cu.
Owing to short bonding time and the finite rates of solid-state phase transformations,
there
is
prospectus
that
a
thin
layer
on
micro hardness across the transition the
zone by using Nano
low-melting point material fused and alloyed with the more refractory metal. Rapid melting and solidification explain the
Indeniter
XP
equipment.
Five
points
near the interfaces
and the
formed
intermetallic
phases
it
is
in
accordance
formation of intermetallic phases.
13
on
both
basic
metals
and
one
point
on
the transition zone
with Carpenter and Wittman who deduced that solid
3.6 Nano Indentation
were chosen for the test.
state diffusion is not involved as active bonding mechaFor
MPW
joint
at
the
discharge
voltage
of
10kV,
the
nano
indentation
test
was
carried
out to measureand
the micro
hardness acrossof the micro hardThe magnitude
the distribution
nism in the process of MPW aluminum to copper.
the transition zone by using Nano Indeniter XP equipment. Five points near the interfaces on both basic metals and one point on
ness are given in Figure 8 (a) and (b). It is illustrated that
ThetheSum
spectra
of the
welded
clearly illustransition
zone were
chosen
for thespecimen
test.
The magnitude
and the distribution
of the micro
hardness are given
8 (a)hardness
and (b). It isvalue
illustrated
hardness value
in that
thethetransition
zone is the highest
trates the
% composition
of Copper
and Aluminium
inin Figurethe
in the transition zone is the highest and the values decrease with increasing the distance away from the zone or the interface. It
and
the
values
decrease
with
increasing
the weld
shownto in
7(b).deformation
The proportionate
can joints
be attributable
the Figure
sharp plastic
along the interfaces that causes the gradient of work hardening near the the distance away
interface.
from the zone or the interface. It can be attributable to the
quantity of Aluminium is remarkably more in the left hand
sharp plastic deformation along the interfaces that causes
side of the intermetallic region and copper dominates to
the gradient of work hardening near the interface.
the right of the curve, the AL-Cu in equal proportion is
6
Vol 8 (36) | December 2015 | www.indjst.org
Indian Journal of Science and Technology
(b)
Figure 8. (a) Indentation hardness of Al/Cu. (b) Indentation modulus of Al/Cu.
S. Kudiyarasan and S. Arungalai Vendan
Similarly in combination of SS/Cu also the intermediate compounds produced in the tran
hardness than the basic metals which is shown Figure 9 (a), (b) and (c).
(a)
(a)
(a)
Both the plastic deformation and the hardness reduce with increasing the distance from the interfaces. In addition, the
intermediate compounds might be produced in the transition zone that is fragile and has higher hardness than the basic metals16,
which will be analyzed deeply.
(a)
(a)
Both the plastic deformation and the hardness reduce with increasing the distance from the interfaces. In addition, the
intermediate compounds might be produced in the transition zone that is fragile and has higher hardness than the basic metals16,
which will be analyzed deeply.
(b)
(b)
(b)
(b)
(b)
(b)
Figure
(a) Indentationhardness
hardness ofofAl/Cu.
(b)(b)
Indentation
modulus of Al/Cu.
Figure 8. (a)8.Indentation
Al/Cu.
Indentation
modulus of Al/Cu.
Similarly in combination of SS/Cu also the intermediate compounds produced in the transition zone that is fragile and has higher
hardness than the basic metals(b)
which is shown Figure 9 (a), (b) and (c).
8. (a) Indentation
hardnessand
of Al/Cu.
(b) Indentation
modulus of Al/Cu.
BothFigure
the plastic
deformation
the hardness
reduce
(c)(c)
with increasing the distance from the interfaces. In addi(c)
Figure
(a) Indentation
in
Side
start
from interface.
Indentation Hardness of SS/Cu
in combination
of SS/Cu also
the intermediate
compounds
in the9. transition
zone
that is fragile
and
has
higher
Figure
(a) 9.Indentation
inSSSS
Side
start
from (b)
interface.
tion, theSimilarly
intermediate
compounds
might
be produced
in produced
Figure 9. (a) Indentation in SS Side start from interface. (b) Indentation Hardness of SS/Cu
hardness than the basic metals which is shown Figure 9 (a), (b) and (c).
(b) Indentation Hardness of SS/Cu.
(c) (c) Indentation Modulus
the transition zone that is fragile and has higher hardness
16
of
SS/Cu.
than the basic metals , which will be analyzed deeply.
Figure 9. (a) Indentation in SS Side start from interface. (b) Indentation Hardness of S
Similarly in combination of SS/Cu also the intermediate compounds produced
in the transition zone that
(a)
is fragile and has higher hardness than the basic metals
which is shown Figure 9 (a), (b) and (c).
(a)
(a)
Similarly in combination of Al/SS also the interme(a)
diate compounds produced in the transition zone that
(a)(a)
is fragile and has higher hardness than the basic metals
which is shown Figure 10 (a), (b) and (c).
4. Reliability Analysis
The Magnetic Pulse Welding (MPW) is one of the ­reliable
methods that can be used for the dissimilar metal joints.
The Magnetic Pulse Welding (MPW) provides an excellent
tool for achieving of conductive metals such as aluminum,
brass, or copper to steel, titanium, stainless, aluminum,
magnesium copper and most other metals joints19. The
Vol 8 (36) | December 2015 | www.indjst.org
(b)
(b)
Indian Journal of Science and Technology
7
(b)
Magnetic Pulse Welding of
Two Dissimilar Materials with Various Combinations Adopted in Nuclear Applications
c­ racking and spallation. The Cu-SS requires further study
in the betterment of bonding.
6. Acknowledgements
The authors sincerely thank SERB, Dept. of Science and
Technology, India for providing the financial assistance
vide order # FTYSS: SR/FTP/ETA-0134/2011 to carry out
this research and IGCAR, India for testing and analysis.
7. References
(c)
(c)
Figure 10. (a) Indentation in Al/SS side start from interface. (b) Indentation hardness of Al/SS. (c) Indentation modulus of
10. (a) Indentation in Al/SS side start Al/SS.
from
1. Pulsar Ltd: Magnetic pulse welding
Figure
solutions. Raanana,
interface. (b) Indentation hardness of Al/SS. (c) Indentation
Israel:
Pulsar
Ltd;
2006.
Available
from:
Similarly in combination of Al/SS also the intermediate compounds produced in the transition zone that is fragile and has higher http://www.pulsar.
modulus
of Al/SS.
hardness
than the basic metals which is shown Figure 10 (a), (b) and (c).
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structure
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joints. The
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de Physique 4. 1997;
microscope
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Magnetic
Pulse
Welding microscope,
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metals joints19. The structure of an interphase
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was determined
by a process
spectroscope.
3. Austin
W. The
cold welding
is being used for more
Pulse Welding
(MPW)
is reliable
and
wellandsuited
to to high-volume
The Magnetic
Pulse Welding
(MPW) is
reliable
well suited
production (MTBF typically 1-5 million
and more
high-volume applications. Assembly Magazine;
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microstructure
and strength
of steel/aluminum
alloy
Magnetic Pulse Welding of three dissimilar configurations of metals is performed
and a detailed comparative
study between
the
jointheat
fabricated
by magnetic
pressure seam welding.
specimens is done. Specific Observations include the dissimilar metals generateslap
enough
at the interface
to enhance plenty
5. Conclusion
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amounts
of these and
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chemical
composition
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chosen. This behavior is endorsed to different
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Pulse
Weldingofofthethree
dissimilar
configurations
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Masumoto
I, Tamaki K, Kojima M. Electromagnetic
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