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Aluminium and its alloys have gained increasing importance in structural engineering due to advantageous properties such as light weight, ease of machining and corrosion resistance. This article presents surface-related challenges facing aluminium welding, specifically weld process limitations and joint limitations. The methodological approach is a critical review of published literature and results based on eight industrial welding processes for aluminium and six joint types. It is shown that challenges such as heat input control, hot cracking, porosity and weldable thickness vary with the process used and that there is no optimal general weld process for all aluminium alloys and thicknesses. A selection table is presented to assist in selection of the optimal process for specific applications. This study illustrates that knowledge of weld limitations is valuable in selection of appropriate weld processes.
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Manufacture
Engineers, Part B: Journal of Engineering
Proceedings of the Institution of Mechanical
http://pib.sagepub.com/content/227/8/1129
The online version of this article can be found at:
DOI: 10.1177/0954405413484015
originally published online 23 May 2013 2013 227: 1129Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture
Muyiwa Olabode, Paul Kah and Jukka Martikainen
Aluminium alloys welding processes: Challenges, joint types and process selection
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Review Article
Proc IMechE Part B:
J Engineering Manufacture
227(8) 1129–1137
ÓIMechE 2013
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DOI: 10.1177/0954405413484015
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Aluminium alloys welding processes:
Challenges, joint types and process
selection
Muyiwa Olabode, Paul Kah and Jukka Martikainen
Abstract
Aluminium and its alloys have gained increasing importance in structural engineering due to advantageous properties
such as light weight, ease of machining and corrosion resistance. This article presents surface-related challenges facing
aluminium welding, specifically weld process limitations and joint limitations. The methodological approach is a critical
review of published literature and results based on eight industrial welding processes for aluminium and six joint types. It
is shown that challenges such as heat input control, hot cracking, porosity and weldable thickness vary with the process
used and that there is no optimal general weld process for all aluminium alloys and thicknesses. A selection table is pre-
sented to assist in selection of the optimal process for specific applications. This study illustrates that knowledge of weld
limitations is valuable in selection of appropriate weld processes.
Keywords
Aluminium alloys, aluminium oxide, shielding gases, anodising, aluminium welding process selection
Date received: 17 September 2012; accepted: 4 March 2013
Introduction
Aluminium and its alloys are widely used in welding
industries due to economic advantages such as light
weight, good corrosion resistance, high toughness,
extreme temperature capabilities and easy recyclabil-
ity.
1
Aluminium alloys are used for construction of air-
planes, cars, rail coaches and marine transports.
Aluminium alloys are used in manufacture of tanks
and pressure vessels because of their high specific
strength, good heat conductivity and beneficial proper-
ties at low temperatures.
2
Aluminium is the second
most used metal after iron and steel in the industry; for
example, aluminium is the second most used material
taking about 15% of total body weight of average cars
and about 34% in Audi A2.
3
There are comprehensive
reviews on the uses and applications of aluminium and
its alloys.
4,5
Welding is a means of joining metals by
creating coalescence due to heat. The work piece is
melted at the joint point (weld pool) that solidifies on
cooling. Welding of aluminium alloys is important for
fabricating structural constructions and mechanical
fabrications like aircrafts. However, welding has prob-
lems and can be challenging. Welding defects common
to aluminium include porosity, hot cracking, incom-
plete fusion and so on.
2,6
Researches
7,8
have shown that welding aluminium
demands greater caution compared with steel, particu-
larly as regards the amount of heat input and pre-weld
cleaning, and that acceptable weld processes for alumi-
nium joints are limited because the weldable thickness
varies considerably with the different welding processes.
It is therefore of interest to study the limitations facing
aluminium welding, particularly joint- and process-
specific limitations.
The aim of this article is to present a comprehensive
guide to understanding aluminium-welding challenges.
In the field of aluminium welding, there are eight
industrially common welding processes and six basic
joint types that have been analysed. For comparison
purposes, a table is designed that shows the influence of
joint and process limitations on optimum welding pro-
cess selection. The remainder of this article is divided
into two main parts, which are surface-related welding
challenges and joint types and process limitations.
Lappeenranta University of Technology, Lappeenranta, Finland
Corresponding author:
Muyiwa Olabode, Lappeenranta University of Technology, Skinnarilankatu
34, 53850 Lappeenranta, Finland.
Email: muyiwa.olabode@lut.fi
at Lappeenrannan Teknillinen on September 3, 2013pib.sagepub.comDownloaded from
Evaluation of the findings shows that there is no sin-
gular optimum process for welding aluminium.
However, understanding of the limitations of individ-
ual welding processes helps in selection of the optimal
process for specific aluminium weld applications.
Surface-related welding considerations
A clean, smooth and protected surface is important in
pre-weld aluminium structures to ensure good alumi-
nium weldments except in high energy density welding
processes like hybrid laser beam welding (LBW) (using
pulsed metal inert gas (MIG)).
9
It is therefore impor-
tant to understand different surface-related phenomena
and their effect on the weldability of the work piece. In
addition, knowledge of preventative measures ensuring
the attainment of acceptable welds, despite any adverse
surface effects, is also important.
Presence of aluminium oxide surface
Oxide formation in aluminium occurs due to the strong
chemical affinity of aluminium for oxygen on exposure
to air. The aluminium oxide thickness increases as a
result of thermal treatment, moist storage conditions
and electrochemical treatment (anodising).
10–14
It is
also important to note that Al
2
O
3
melts at about
2050 °C, while aluminium alloys melts at about 660 °C
9
(as illustrated in Figure 1). Therefore, the layer is
removed by pickling or dry machining just before weld.
However, the difference in melting point is not a prob-
lem during the processing by means of high energy den-
sity welding processes; it can also be an advantage, for
example, the presence of oxide layer during laser weld-
ing increases the absorptivity of aluminium and its
alloys to laser radiation.
15,16
It should be noted, that a
main challenge in applying most joining technologies to
aluminium is its tendency to form a thick, coherent
oxide layer. This oxide layer has a melting temperature
much higher than that of aluminium itself; moreover, it
has a significant mechanical strength. Therefore, this
oxide layer can remain as a solid film (or fractured in
small particles) due to the flow of the molten material,
16
even when the surrounding metal is molten. This can
result in severe incomplete fusion defects. Therefore,
the removal of the oxide layer just before welding is
important.
The aluminium oxide layer is, furthermore, an elec-
trical insulator, and the layer may sometimes be thick
enough to prevent arc initiation. In MIG processes, a
thick oxide layer can produce erratic electrical com-
mutation in the gun’s contact tube, resulting in poor
welds.
It is thus evident that aluminium oxide has to be
removed before welding because it compromises the
quality of the weld. Generally, the oxide removal can
be done by mechanical processes like brushing with a
stainless steel brush, cutting with a saw or grinding with
semi-flexible aluminium oxide grinding discs.
9
Some
welding processes enhance additional oxide removal
processes, for example, in ultrasound metal welding
processes (UW), oxides and contaminates are removed
by high-frequency motion, thus providing metal–metal
contact and allowing for the work pieces to bond prop-
erly.
17
In hybrid laser MIG-welding of aluminium
alloys, the MIG-welding process has a cleaning effect
that removes the aluminium oxide layer. However, it is
recommended that pre-weld cleaning of the weld sur-
face should be carried out preferably by pickling or dry
machining.
18
In gas-shielded arc welding, aluminium
oxide removal from the weld pool can be done by cath-
ode etching (which is controlled chemical surface corro-
sion done to reveal the details of the microstructure).
19
A direct current passes through the electrode connected
to the positive pole of the power source. There is thus a
flow of electrons from the work piece to the electrode
and the ions flow in the opposite direction, bombarding
the work piece surface. The aluminium oxide film is
broken and dispersed by the ion bombardment, thereby
allowing the flowing weld metal to fuse with the parent
metal. It is advantageous to remove the aluminium
oxide layer before welding because
2,9
1. It significantly reduces the amount of hydrogen
porosity in the weld.
2. It helps to improve the stability of the weld process
especially in tungsten inert gas welding (TIG).
3. It allows for complete fusion of the weld. Cathode
cleaning is important in TIG process as the oxide
starts to form immediately after wire brushing.
Figure 1. Schematic of aluminium showing its oxide layer and the anodised surface.
1130 Proc IMechE Part B: J Engineering Manufacture 227(8)
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Aluminium oxide can also be removed by chemical
etching or pickling. Table 1 presents chemical treat-
ments for oxide layer removal.
9
One of the causes of the oxide layer is from anodisa-
tion, which is an electrochemical process by which a
metal surface is converted into a decorative, durable,
corrosion resistant anodic oxide finish.
20,21
Anodisation
utilises the unique ability of amorphous alumina to build
up an even porous morphology
22
formed in alkaline and
acidic electrolytes. During anodising, aluminium oxide is
not applied like paint or plating. Rather, it is integrated
fully with the underlying aluminium substrate.
Therefore, it cannot peel or chip off. The anodic oxide
structure is highly ordered and porous, thereby allowing
for further processing like sealing and colouring.
20
The reasons for the utilisation of anodisation are to
increase corrosion resistance and ensure the metal sur-
face is fade proof for up to 50 years,
23
to improve dec-
orative appearance, to increase abrasion resistance and
paint adhesion, to improve adhesive bonding and lubri-
city, to provide unique decorative colours or electrical
insulation, to permit subsequent plating, to detect sur-
face flaws, to increase emissivity and to permit applica-
tion of photographic and lithographic emulsions.
14,20,24
Anodising of aluminium alloys is generally advanta-
geous. However, it poses challenges for aluminium
welding because the arc cleaning effect of the AC cur-
rent cannot remove the double layer (the anodised layer
and oxide layer as in Figure 1). Before welding, the
anodised surface needs to be removed.
20
Shielding gas selection
Shielding gas protects the molten weld pool from the
atmosphere, which is important because aluminium has
a tendency to react with atmospheric air to form oxide
and nitrides. The shielding gases commonly used in
welding aluminium and its alloys are inert gases such
as argon and helium.
Argon is used as a shielding gas for manual and
automatic welding. Argon is cheaper than helium, and
the use of argon produces a more stable arc and
smoother welds. However, argon gives lower heat input
and lower attainable welding speed, and therefore there
is the possibility of a lack of fusion and porosity in
thick sections. In addition, use of argon can result in a
black sooty deposit on weld surfaces, although this can
be wire brushed away. It has been observed that with
helium shielding gas, the arc voltage is increased by
20%, resulting in a higher, hotter arc, deeper penetra-
tion and wider weld beads. This implies that the criti-
cality of arc positioning (aids avoidance of missed edge
and insufficient penetration defects) is lower with
helium. There is a reduction in the level of porosity
when helium shielding gas is used because the weld
pool is hotter and there is slower cooling, which allows
hydrogen to diffuse from the weld pool. Due to the
higher heat produced, the use of helium allows that
welding speeds up to three times higher than with
argon. The high cost of helium and the inherent arc
instability mean, however, that helium is used mainly
in mechanised and automatic welding processes.
9
It is common practice to use a mixture of helium and
argon as it provides a compromise on the advantages of
each gas. Common combinations are 50% or 75% of
helium in argon, which allow for better productivity by
increasing the welding speed and provide a wider toler-
ance for acceptable welds. The purity of the shielding
gas is of importance. At the torch, not at the cylinder
regulator, a minimum purity requirement of 99.998%
and low moisture levels of less than 250 °C (less than
39 parts per million (ppm) H
2
O) are expected.
9
Generally, the shielding gas should be selected with the
following considerations.
2,9,25,26
Table 1. Chemical treatments for cleaning and oxide removal.
9
Solution Concentration Temp (°C) Procedure Container material Purpose
Nitric acid 50% water
50% HNO
3
(technical
grade)
18–24 Immerse 15 min
Rinse in cold water
Rinse in hot water
Dry
Stainless steel Removal of thin oxide
film for fusion welding
Sodium hydroxide
followed
by nitric acid
5% NaOH in
water
Concentrated
HNO
3
70
18–24
Immerse for 10–60 s
Rinse in cold water
Immerse 30 s
Rinse in cold water
Rinse in hot water
Dry
Mild steel
Stainless steel
Removal of thick oxide
film for all welding and
brazing operations
Sulphuric chromic
acid
5LH
2
SO
4
1.4 kg CrO
3
40 L water
70–80 Dip for 2–3 min
Rinse in cold water
Rinse in hot water
Dry
Antimonial
lead lined steel
tank
Removal of films and
stains from heat treating
and oxide coatings
Phosphoric chromic
acid
1.98 L of 75%
H
3
PO
3
0.65 kg of CrO
3
45 L of water
95 Dip for 5–10 min
Rinse in cold water
Rinse in hot water
Dry
Stainless steel Removal of anodic
coatings
Olabode et al. 1131
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1. The gas must be able to generate plasma and a sta-
ble arc mechanism and characteristics.
2. It should provide smooth detachment of molten
metal from the wire and fulfil the desired mode of
metal transfer.
3. It should protect the welding head (in the arc’s
immediate vicinity), molten pool and wire tip from
oxidation.
4. It should help to attain good penetration and good
weld bead profile.
5. It should not affect the welding speed of the
process.
6. It should prevent undercutting tendencies.
7. It should limit the need for post-weld cleaning.
8. It should not be detrimental to the weld metal
mechanical properties.
The recommended shielding gas for welding alumi-
nium using pulsed MIG is argon (99.998%)
25,27
at a
flow rate of about 20 L/min.
27
A mixture of argon and
helium can also be used and even helium alone. Helium
increases the weld penetration and offers higher arc
energy and thus increased deposition rate,
27,28
and it
should be used when the section is greater than 50 mm.
9
More details can be seen in Table 2, which presents
MIG shielding gases for aluminium, and Table 3 pre-
sents the effects of shielding gases on aluminium weld-
ing. Studies have shown that welding of aluminium can
be improved (arc stability) by oxygen doping of inert
shielding gas.
29
In addition, the alternating shielding
gases reduces weld porosity.
30–32
Joint types and process limitations
This article considers eight industrially accepted welding
processes and six joint types. Joint design is important
because it costs money to buy weld metal. The fillet throat,
weld accessibility and the functionality of the welded work
piece are taken into consideration in this design. The six
joints considered are butt, T-joint, corner, cruciform, edge
and lap joint (see Table 4), which are derived from the
three basic welding joints (fillet, lap and butt joints). Joint
designs are based on the strength requirements, the alloys
to be joined, the thickness of the material, the joint type
and location, weld accessibility and the welding process.
Before choosing the joint design, it is important to note
that welding in the flat or downward position is preferable
in all arc-welding processes, as there is the easier possibility
of depositing high-quality weld metal at a high deposition
rate in a flat position. Additionally, the weld pool is larger,
allowing for a slower cooling and solidification rate, which
enhances the escape of trapped gases in the weld pool. The
flat position reduces weld porosity, reduces weld cost, and
gives the best weld metal quality compared with other
positions. The static tensile strength of the weld is deter-
mined by the throat thickness, which must be designed to
ensure that it can carry the workload for which the weld is
designed. Conventional TIG and MIG processes produce
Table 3. Effect of shielding gas on aluminium welding.
9,29–34
Shielding gas Relative effect (100% argon as the reference)
100% Ar Ar + He 100% He
Gas flow Nominal Higher Highest
Arc voltage (MIG) Nominal Higher Highest
Arc (MIG) Nominal stability More unstable Most unstable
Weld seam width and depth Nominal width and depth Higher width
Shorter depth
Highest width
Shortest depth
Weld seam appearance Nominal smoothness Smoother Smoothest
Penetration Nominal depth and roundness Deeper and more round Deepest and most round
Welding speed Nominal welding speed Higher attainability Highest attainability
Lack of fusion Nominal Lower Lowest
Porosity Nominal Lower Lowest
Pre-heating Nominal Less needed Least needed
Heat production Nominal warmth Warmer work piece Warmest work piece
Cost of shielding gas Nominal price More expensive Most expensive
MIG: metal inert gas welding.
Table 2. MIG shielding gases for aluminium.
26
Metal transfer mode Shielding gas Characteristics
Spray transfer 100% Argon Best metal transfer and arc stability, least spatter, and good cleaning action.
35% Argon–65% Helium Higher heat input than 100% argon; improved fusion characteristics on thicker
material; minimises porosity.
25% Argon–75% Helium Highest heat input; minimises porosity; least cleaning action
Short circuiting Argon or Argon + Helium Argon satisfactory on sheet metal; argon–helium preferred for thicker base
material.
1132 Proc IMechE Part B: J Engineering Manufacture 227(8)
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Table 4. Joint types and process limitations of aluminium alloys.
2,8,9,17,18,35–52
Processes
Joints
MIG TIG PAW FSW LBW RW EBW UW
Butt joint (a)
Lap joint (b)
T-joint (c)
Edge joint (d)
Corner joint (e)
Cruciform (f)
Limitation Limitation Limitation Limitation Limitation Limitation Limitation Limitation
(a)
(b)
(c)
(d)
(e)
(f)
With argon, weldable
thickness is limited to
25 mm, and with helium,
it is limited to 75 mm.
Limited torch distance of
10–19 mm to ensure
properly shielded weld
metal limits flexibility.
Limited outdoor
application because air
drafts can disperse the
shielding gas.
Limited operator
acceptability of the
process because of the
relatively high levels of
radiated heat and arc
intensity.
Limited to thin gauges of
up to 6 mm thickness.
Limited (shallower)
penetration into parent
metal compared to MIG.
With argon shielding gas,
the economical weld
thickness limit is 10–
18 mm with helium
(DCEN).
Difficult to penetrate
into corners and into the
roots of fillet welds.
Limited by the lower
deposition rate, low
tolerance on filler and
base metal, and cost for
thick sections compared
to MIG.
Plasma MIG weld
thicknesses limited to 6–
60 mm range.
Plasma TIG weld
thicknesses range can be
less than 2.5–16 mm in a
single pass.
Limited by the high
capital equipment and
material cost compared
to TIG.
Limited tolerance of the
process to joint gaps and
misalignment.
Limited operator
acceptability of the
process due to the
complex torch
architecture that
requires more
maintenance and
accurate set-back of the
electrode tip with
respect to the nozzle
orifice, which is
challenging.
Weldable thickness
ranges from 1–50 mm
(single pass).
Tool design, process
parameters, and
mechanical properties
database is limited and
only available for limited
alloys and thicknesses
(up to 70 mm).
Limited to lower
productivity cases
compared to LBW.
Insufficient design
guidelines and limited
education for
implementation.
Exit hole left when tool
is withdrawn.
Large down forces
required with heavy duty
clamping necessary to
hold the plates together
during welding.
Environmentally friendly
welding process because
fumes and spatters are
not generated.
Limited conversion
efficiency of electrical
power to focused
infrared laser beam also
called wall plug efficiency
(about 10%–30% and up
to 40% in fibre lasers).
Limited fit up tolerance.
Precise fit up (15% of
material thickness)
needed for butt and lap
joints.
Limited operator
acceptability of the
process due to the large
capital investment
needed, therefore
requiring high volume
production or critical
applications to justify the
expenditure.
Limited weld thickness
range (0.9–3.2 mm)
Lower tensile and fatigue
strength compared to
other fusion welding
processes.
Limited joint designs or
configuration. Seam
welds can generate
unzipping effect.
Limited operator
acceptability of the
process because, in
thick-sectioned upset
welds; there is lack of
good non-destructive
weld quality testing high
electrode wear rate and
deterioration.
In addition, it requires
access to both sides of
the joint.
High cost of
equipment.
Work chamber size
constraints.
Time delay when
welding in a vacuum.
High weld preparation
costs.
X-rays produced
during welding can be a
health risk.
Rapid solidification
rates can cause
cracking in some
materials.
Can weld up to
450 mm thick plates.
Expensive high
powered transducers
are needed to enable
welding of thick gauges,
castings, extrusions,
and hydro-formed
components.
Alternative welding
configurations are
needed to weld a wide
variety of component
geometries and joint
configurations.
Vibration control
strategies are needed
to ensure weld quality
across a wide range of
component geometries
and the thickness of
the weld piece is
limited.
DCEN: direct current electrode negative; EBW: electron beam welding; FSW: friction stir welding; LBW: laser beam welding; MIG: metal inert gas welding; PAW: plasma arc welding; RW: resistance welding; TIG, tungsten inert
gas welding; UW: ultrasonic welding.
Olabode et al. 1133
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weld metal on the surface of a plate during bead-on-plate
weldstoadepthof3mmforTIGand6mmforMIG.
Therefore, to attain complete penetration for welds over
3 mm (MIG) and 6 mm (TIG), there is the need for bevel-
ling on butt joints, for example. The bevel can be single or
double sided.
9
As presented in Table 4, eight considered welding
processes are correlated with their applicability on six
different welding joints. Butt and lap joints are applica-
ble to all the selected weld processes. Cruciform joints
have the least applicability across the processes, which
is due to limited fixturing possibility during welding.
Table 4 provides additional information on the viabi-
lity of six joint types on the eighth selected welding pro-
cesses by presenting the process-specific limitations.
An application of this review article is to use the pre-
stated information to influence the selection case-
specific optimum welding process. It can be challenging
to determine an appropriate welding process to be used
for aluminium. However, the challenge can be simpli-
fied by considering various comparison selection factors
as presented in Table 5. The solution to the challenge is
case specific. An understanding of the selection factors
considered provides better process selection and thus a
better evaluation.
It is important to point out that the scaling is subject
to the designer’s discretion and not completely objective.
The welding designer determines the importance level of
the selected aluminium-welding project by answering a
question like ‘how important is’ strength, elongation,
chemical stability, etc., to the finished product. The
designer defines the importance level on a scale of 1–3
(1= least, 2 = moderate and 3 = high). In a similar
fashion, the advantageous level is determined by answer-
ing a question like ‘how advantageous is’ the selected
welding process to the selected consideration. The
importance level is multiplied by the advantage level
and the result is called an impact factor. The impact fac-
tor is summed up for each selected welding process, and
the welding process with the highest impact factor sum-
mation is selected as the optimal welding process.
Case study
Awelding process for high-strength aluminium for aero-
space is to be selected. The available welding processes
Table 5. Weld process selection (the highest factor summation is the best of the processes considered).
Selection factors Process A (TIG) Process B (FSW) Process C (PAW) Process D (MIG)
Quality of the welded joint Imp. Ad. I. Fac. Imp. Ad. I. Fac. Imp. Ad. I. Fac. Imp. Ad. I. Fac.
Strength 3 2 6 3 2 6 – – – 3 2 6
Elongation 2 2 4 2 3 6 2 2 4 2 3 6
Chemical stability 2 2 4 2 3 6 2 3 6 2 3 6
Weld defects 2 3 6 2 1 2 2 1 2 2 1 2
Penetration 1 3 3 1 3 3 1 3 3 1 3 3
Distortion 1 1 1 1 2 2 1 2 2 1 2 2
Suitability for use
Welding thin sheet (\1mm)224 236 236 224
Sheet welding (.3mm) 111 122 122 133
Welding Al-Mg alloys 1 2 2 1 2 2 1 2 2 1 2 2
Overhead welding 1 1 1 1 3 3 – – – – – –
Variable material thickness 2 1 2 2 1 2 2 2 4 2 2 4
Variable welding speed 1 1 1 1 2 2 1 3 3 1 2 2
Welding of castings 2 2 4 2 3 6 2 2 4 2 2 4
Joining cast to wrought alloys 1 3 3 1 3 3 1 1 1 1 2 2
Repair welds on castings 2 3 6 2 3 6 2 1 2 2 2 4
Suitability for automation
With filler 1 1 1 1 3 3 1 2 2 1 3 3
Without filler 2 3 6 2 1 2 2 1 2 2 1 2
Butt welding \3mm 2 12 2 24 2 24 2 24
.3mm 1 22 1 11 1 33 1 11
Suitability for joint type
Butt joint 1 2 2 1 1 1 1 1 1 – – –
Lap joint 1 3 3 1 3 3 1 1 1 1 1 1
Economic aspects
Equipment costs 3 2 6 3 3 9 3 2 6 3 1 3
Maintenance costs 3 2 6 3 2 6 3 3 9 3 2 6
Labour costs 1 3 3 1 2 2 1 3 3 1 3 3
Welder’s training time 1 1 1 1 1 1 1 1 1 1 3 3
Process rating (P) 80897376
Imp.: importance level; Ad.: advantage level; I. Fac.: impact factor; EBW: electron beam welding; FSW: friction stir welding; LBW: laser beam welding;
MIG: metal inert gas welding; PAW: plasma arc welding; RW: resistance welding; TIG, tungsten inert gas welding; UW: ultrasonic welding.
1134 Proc IMechE Part B: J Engineering Manufacture 227(8)
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are as presented in Table 5. A blank table is constructed
and the considered welding processes are selected and
filled into the table.
The selection factors under consideration are as pre-
sented in Table 5, which are categorised under quality
of the weld joint, suitability for use, suitability of fillers,
joint suitability and economics. Therefore, at this stage
in the design, the processes row and the selection factor
column are filled in the table.
As the designer, the importance level is determined
and designed on a scale of 1–3, and using a scale of five
is also applicable, but the calculation becomes more
complex. Choosing a scale of 1–3 (1 = low, 2 = moder-
ate and 3 = high), a number is assigned to the consid-
ered selection factor. Therefore, at this stage, the
importance level of the selection factor under consider-
ation is filled into the ‘Imp.’ column (Table 5). It is
important to note that the number is the same across
row (all processes) because the importance of a selec-
tion factor is independent of the process.
The advantage level is determined and designed by
the designer on the same scaling used for importance
level. If the scaling used in importance level is five, the
scaling of five should be used. In this case, a scaling of
1–3 is used where 1 = low, 2 = moderate and 3 = high.
At this stage, the entire advantageous level column on
Table 5 is filled for all the considered selection factors
into the ‘Ad.’ column.
The calculation for the impact factor and the process
rating is carried out. The impact factor for each consid-
ered selection factor is derived by multiplying the
importance level column of each process by advanta-
geous level column of each process. The derived value
is filled into the ‘I. Fac.’ (impact factor) column of
Table 5. The process rating (welding process) is derived
by the summation of all the impact values column of
each process. Therefore, the process rating row is filled
in Table 5.
The optimum weld process is the process with the
highest process rating, which in this case study is pro-
cess C friction stir welding (FSW).
Conclusion
This article examined the surface-related challenges,
joint types and limitations of aluminium alloys with the
focus on providing a guide on how to select an optimal
welding process. Aluminium and its alloys have welding
challenges, which include the presence of aluminium
oxide on surfaces, welding of anodised aluminium and
limited shielding gas options. The aluminium oxide sur-
face is formed when aluminium is exposed to an atmo-
sphere containing oxygen, and the aluminium oxide has
to be cleaned away from the surface before welding
because its causes weld defects like porosity.
The chemical affinity of aluminium for oxygen is uti-
lised for anodising aluminium alloys and then painting
to improve corrosion resistance. However, it can be
detrimental when welding anodised aluminium as the
anodised layer has to be cleaned before welding. The
melting point of aluminium alloys is generally around
660 °C and the melting point of aluminium oxide is
2050 °C. It is therefore recommended that the aluminium
oxide layer or the anodised layer be removed, mechani-
cally or chemically, just before welding.
Aluminium alloys have high chemical affinity; there-
fore only inert gases can be used as shielding gases dur-
ing welding. Argon and helium gases are used in
aluminium welding to protect the weld pool. The pres-
ence of helium increases the arc heat input and there-
fore allows for deeper penetration compared with
argon gas, but on the other hand, helium is more
expensive than argon. A mixture of helium and argon
is sometimes used to improve weldability of some alu-
minium alloys. A wider range of shielding gases would
increase the manipulation possibility for aluminium
alloy welding, but currently argon and helium are the
only gases used.
The industrial welding processes considered in this
work include MIG, TIG, plasma arc welding (PAW),
FSW, LBW, resistance welding (RW), electron beam
welding (EBW) and UW. The weldable thickness is a
limitation in all the processes; the highest weldable
thickness of up to 70 mm is achieved with EBW. FSW
produces the best weld because the mechanical property
deterioration is minimal, and the process is friendly as
no fumes or spatters are produced during welding.
The joint configurations considered include the butt
joint, lap joint, T-joint, edge joint, corner joints and
cruciform joint. The butt joint and lap joint are appli-
cable to all the considered welding processes. The pos-
sibility of using different joint orientations with the
considered welding processes depends on the manipula-
tion of the work piece (fixturing).
Although FSW produces the best weld for alumi-
nium alloys, the optimal welding process is case spe-
cific. The designed table for weld process selection
provides information on how to select the optimal
process based on case-specific considerations for alu-
minium alloys.
Declaration of conflicting interests
The authors declare that there are no conflicts of
interest.
Funding
This research received no specific grant from any fund-
ing agency in the public, commercial or not-for-profit
sectors.
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Appendix 1
Notation
EBW electron beam welding
FSW friction stir welding
LBW laser beam welding
MIG metal inert gas welding
PAW plasma arc welding
ppm parts per million
RW resistance welding
TIG tungsten inert gas welding
UW ultrasonic welding
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... FSW has been invented for aluminum (Al) and this pairing is found to perform optimally: Joining sheets with FSW generally avoids hot cracking, porosity, distortion and other problems which typically pertain to fusion welding and especially Al is said to be troublesome to weld by fusion. If welded by friction, however, its low melting point is makes it easy to plasticize [1]. The versatility of this process also allows for joining dissimilar metals [2][3][4]. ...
... Stop time of the simulation is dependent on the deformation speed ε ˙and the number of turns N and can be evaluated using =⁄ (1) Calculations are known to be a time-consuming process. In order to avoid error by configuration they were initially executed on a simpler model with fewer steps and nodes or made to break specifically early in the process to compare the calculated values with the expected one. ...
... The curves given in Fig. 4, which depict the relevant part of the recorded temperature and torque time series for experiments at a deformation speed of 700 rpm with one full twist, may thus be understood as representative for each material's response behavior. The end of twisting operation for the given parameters according to (1) is at about 900 ms. Further space on the time axis is to provide context. ...
To physically simulate Friction Stir Welding (FSW) the hot high strain rate torsion tests were realized on Gleeble-3800 System for different Al-based materials: technically pure A5 (ISO equivalent 1050), AMg5 (5056) and D16 (2024). A finite element model was built and validated using temperature and torque data obtained after physical simulation. Experimental data was compared with a numerical simulation of the process. The possibility to use physical simulation for description of the processes during FSW is discussed.
... The GTAW is an easy and inexpensive welding technique that can produce sound and high quality weldements, however, it is slower than most of other welding techniques. The weld quality in GTAW is primarily controlled by many factors such as workpiece characteristics, electrode quality, filler material, power source type, and welder procedure [2,3]. ...
... Aluminum alloys have been widely used in manufacturing aeronautical and aerospace structures thanks to their high specific strengths and moderate cost. Gas tungsten arc welding (GTAW) is one of the main welding processes employed in welding such structures of aluminum alloys, within which complex three-dimensional (3D) weld paths may exist [1,2]. In GTAW of such 3D welds, it is often impractical to realize and maintain the conventional flat welding position by manipulating the structures for fixed arc because of their large dimensions and/or weights. ...
This study aims to reveal the cause of different weld formation quality for varying welding position in the GTAW (Gas Tungsten Arc Welding) of a thick-sheet aluminum alloy structure. The fluid flow characteristics of weld pools are investigated by CFD (Computational Fluid Dynamic) modeling and high-speed imaging for the climbing and flat welding positions, which correspond to the start and finish ends of the welds of the structure, respectively. Results show that the directions of gravity relative to weld pools may notably affect the fluid flows in weld pools for different welding positions. For flat welding, gravity will accelerate the fluid flow in the direction of sheet thickness only and in turn result in a high velocity downwards, which implies a good penetrating capability. Welds of good formation with smooth surface and consistent width can be produced under flat welding position. In contrast, for climbing welding, gravity will act on the molten metal in both the direction of sheet thickness and the lateral direction of the weld pool. As a result, the velocity in sheet-thickness direction is decreased, which implies a decreased penetrating capability. Meanwhile, the velocity backwards is increased in the top portion of the weld pool, which makes the molten metal apt to flow out of the weld pool. Both the decreased penetrating capability and the accelerated molten metal outflow would render the climbing welding process unstable, and result in welds of poor formation with uneven weld surface and inconsistent weld width. Based on the study, possible methods are proposed that could be used to improve the weld formation quality when welding thick-sheet aluminum alloys structures using various welding positions.
... Currently, there are various ways of connecting dis- similar metals, such as tungsten inert gas (TIG) weld- ing, 1 laser welding 2 and friction stir welding. 3 However, TIG welding is relatively traditional and technologically mature. ...
Auto-body lightweight is becoming an important trend of energy saving and emission reduction. Various materials assembled together would be used to fabricate the auto-body to satisfy this demand. However, the assembly dimensional quality is difficult to be controlled in the real processing due to the huge differences in material properties. Therefore, it is necessary to control and analyze the welding deformation of aluminum alloy and steel. In this work, the orthogonal design experiment has been adopted to analyze the welding deformation of steel–aluminum sheet parts. Subsequently, the response surface model is proposed to establish the relationship between welding deformation and welding parameters by finite element analysis, which is verified by physical experiments again. Meanwhile, the anti-deformation method is also used to decrease the assembly deformation successfully. And the case of Z-shaped planes is applied to further illustrate the proposed method of this work. Finally, the results show that both the methods have a good simulation effect and a high prediction accuracy for the assembly dimensional quality.
... Shaping (LENS) [7][8][9] 、Laser Metal Forming (LMF) [10][11][12][13] 、Direct Metal Deposition (DMD) [14,15] 、Directed Light Fabrication (DLF) [16] 、Laser Additive Manufacturing (LAM) [17][18][19] 、Selective Laser Melting (SLM) [20][21][22][23] [25,26] 、气孔/夹 杂 [27][28][29] 、裂纹 [30][31][32][33][34] )和组织成分控制(枝晶粗化 [35][36][37][38] 、凝固取向 [39,40] 、宏观/微 观偏析 [41,42] 、金属间化合物 [43,44] ...
... Furthermore, to implement the welding of a compact oxide film on the surface of aluminum alloys, the cathode atomization effect resulting from an intense heat source is required. Therefore, the heat input into the base metal must be strictly controlled [12]. The welding power supply should not only ensure welding stability and form aesthetic welding seam, but it should also reduce the heat input and decrease deformation during the welding process [13,14]. ...
In this investigation, a sinusoid modulated pulse gas metal arc welding (SP-GMAW) method based on a current waveform control method and on the welding mechanism of pulsed gas metal arc welding (P-GMAW) was proposed. This method achieved smooth control over the welding current. The process formulas were simplified. Then, the control parameters were discussed and optimized. Finally, three comparison experiments were conducted. The results indicated that the SP-GMAW method, as an improved double-pulsed gas metal arc welding (DP-GMAW) method, had the following features: The SP-GMAW minimized porosity rate and generated palpable weld ripples in contrast with the P-GMAW. The SP-GMAW produced the finest fusion zone grain, highest fusion zone microhardness, and highest tensile strength among three welding methods. The feasibility and superiority of the method for welding aluminum sheet were verified.
The concept of “sustainability” has recently risen to take the old concept of going “green” further. This article presents general methodologies for sustainability assessments. These were then adapted to measure and assess the sustainability of welding processes through building a complete framework, to determine the best welding process for a particular application. To apply this methodology, data about the welding processes would be collected and segregated into four categories: environmental impact, economic impact, social impact, and physical performance. The performance of each category would then be aggregated into a single sustainability score. To demonstrate the capability of this methodology, case studies of three different welding processes were performed. Friction stir welding obtained the highest overall sustainability score compared to gas tungsten arc welding and gas metal arc welding.
The suspension system of a vehicle is responsible for absorbing the vibrations during vehicle movement, thereby providing reliability and stability to the vehicle. The components of the suspension system enable damping the vibrations and avoid transmitting them to the frame. The major components of the suspension system along with their loading conditions are discussed in this paper. An attempt is made to analyze the structural behavior of the trailing arm of the suspension using FEM simulation by meshing and strength analysis using ANSYS analysis software. ANSYS static structural analysis module is used to verify the stress developed in the automobile suspension system. The distribution of the load on the trailing arm and the critical section are presented in this paper.
Dual laser-beam bilateral synchronous welding technique is considered to replace riveting in terms of skin–stringer joints. The 2.0-mm thick Al-Li alloy T-joint, which is welded by dual laser-beam bilateral synchronous welding between 2099-T83 stringer and 2060-T8 skin, is investigated in the current study. Under the tailored process conditions, the examinations and analyses of microstructures, microhardness distribution, hoop tensile mechanical properties, and fractographies of the T-joint are conducted. Experimental results show that the maximum tensile strength of the weld seam is up to 85% of the tensile strength of the skin material. In order to explore the special fracture characteristics of dual laser-beam bilateral synchronous welding joints after tensile test, a three-dimensional finite element model is established and the residual stress of the weldment is analyzed. Considering the scanning electron microscopy results and simulation results comprehensively, stress concentration is the main reason for the weldment failure in tensile test.
Metal inert gas arc welding process was implemented to join 6063T6 wrought alloy and ADC12 die-casting alloy using ER4047 filler metal. The microstructure of the weld seam and weld interface was investigated. The bonding strength of the butt joints was tested by Charpy U-notch impact test and tensile test. The results showed that a sound welding butt joint with finely silicon particles and excellent mechanical properties was formed, and the size of the silicon particles was nearly 2 μm. Compared with 6063T6 wrought alloy, the impact absorbing energies and the tensile strengths of the butt joint were higher and reached 1.173 kJ/cm² and 205 MPa, respectively, and the fractures of all tensile specimens occur at the 6063T6 aluminum.
Hybrid laser-arc welding (HLAW) is a combination of laser welding with arc welding that overcomes many of the shortfalls of both processes. This important book gives a comprehensive account of hybrid laser-arc welding technology and applications. The first part of the book reviews the characteristics of the process, including the properties of joints produced by hybrid laser-arc welding and ways of assessing weld quality. Part two discusses applications of the process to such metals as magnesium alloys, aluminium and steel as well as the use of hybrid laser-arc welding in such sectors as ship building and the automotive industry. With its distinguished editor and international team of contributors, Hybrid laser-arc welding is a valuable source of reference for all those using this important welding technology. Reviews arc and laser welding including both advantages and disadvantages of the hybrid laser-arc approach. Explores the characteristics of the process including the properties of joints produced by hybrid laser-arc welding and ways of assessing weld quality. Examines applications of the process including magnesium alloys, aluminium and steel with specific focus on applications in the shipbuilding and automotive industries.
Ultrasonic metal welding has many advantages including speed, weld quality consistency, and efficiency compared to other joining methods. In order to further improve the process, this work focused on enhancing process consistency. A comparison between three control modes: energy, height (post height), and time was conducted and the results were analyzed. Thus, the main objective of this study was to characterize and compare the weld consistencies of the various control modes. In this study, 60 welds made with optimum welding parameters with each mode were made, and the average weld strength and variance of the population were statistically compared. It was determined by analyzing the data with an F-test with a probability a = 0.05 that there was a slight improvement in weld strength consistency for the time mode compared to the other two modes (energy and post height). No significant difference in the average weld strength was seen for the three modes, only in the consistency of the welds. It is believed that in the energy and post height modes, while the average weld strengths were similar to the time mode, these modes were affected by sample fixture loading and sample variations.
Aluminium alloys are well established as engineering materials for a wide range of applications because they offer a combination of low weight, high strength, good corrosion resistance, formability and weldability. This article identifies the common weldable aluminium alloys and processes used. It also highlights the growth of aluminium as a structural material, giving applications and references to the current British and European standards relating to welding aluminium.
This paper reviews the function of shielding gases in GTAW and GMAW processes and discusses the mixtures currently available and their applications. In addition, an attempt is made to enable the user to critically assess the shielding gas requirements for given applications.
Double-pulse MIG welding of aluminum alloy can improve the efficiency of welding and meanwhile get beautiful weld surface with scaly figures. Based on single-pulse welding, the experiments of double-pulse MIG welding of aluminum alloy were carried out by changing the current, high-frequency, low-frequency and welding velocity of the power which is the self-developed double-pulse MIG welding inverter power. Tests shows that strong/weak pulse peak current and high-frequency have great influence on die stability of welding process and spatters. When the difference between strong and weak pulse peak current is 40 A and high-frequency is 250 Hz, the weld forming is good. To a certain extent, the width of the scaly figure on the weld surface is directly related to low-frequency and welding velocity: the width of the scaly figure will decrease with the improvement of low-frequency and widen with acceleration of welding velocity. An empirical formula reflecting the relationship between low-frequency, welding velocity and the width of the scaly figure through statistical methods is obtained, and the results show that when the ratio of welding velocity to low-frequency is from 0.19 to 0.30, the width of the scaly figure is from 2 to 3 mm, which means good welding performance.
Some of the many applications of aluminum within the welding fabrication industry and its use which has aroused in these industries are discussed. Aluminum became an economically viable competitor to steel within the engineering environment as recently as the end of the 19th century. Aluminum-intensive vehicles provide better handling and braking capability, improving their ability to avoid crashes. Fast ferry projects have advanced the use of aluminum in shipbuilding through development of a new concept in marine transportation. Defense and aerospace industries use high-strength 5xxx series (Al-Mg) non heat-treatable base alloys for some applications, but also make use of some of the more specialized heat- treatable aluminum alloys with superior mechanical properties. The use of aluminum continues to grow within the welding fabrication industry in both size and complexity, and with it the need for aluminum filler metals that will meet these needs, the advancement.
Ultrasonic metal welding is a promising joining method for aluminum automotive body construction applications. In order to achieve technology implementation readiness, process robustness to weld orientation, aluminum sheet rolling direction, residual stamping lubricant level, and material age must be assessed. Experiments were conducted to characterize variations in weld failure loads and microstructural features resulting from the directional nature of the energy input during ultrasonic welding to ensure that the angle at which components are ultrasonically welded together does not affect weld performance. These experiments were also designed to ascertain whether the orientation of a welding machine with respect to the rolling lines on an AA6111 sheet component or the relative orientation of the rolling directions of two components being joined is critical. A second set of experiments was conducted to determine the effects of surface lubricant level on tensile-shear and T-peel failure loads and fatigue performance for AA6111 and AA5754 sheet. Robustness to surface lubricant level is important because often in North American automotive production facilities, components are not cleaned prior to welding; rather, they are welded with residual stamping lubricant on the surfaces. Finally, because AA6111 naturally ages at room temperature for an extended period of time in the T4 temper, experiments were performed to ascertain the impact of AA6111 material age on ultrasonic weld tensile-shear and T-peel failure loads. For all factors considered in this study, ultrasonic metal welding process robustness was demonstrated.
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