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P. Sarkar et al.
offered by this process. The process and its benefits are broadly explained in the
subsequent sections.
4.1.1 Development of FSW
The history of welding can be traced back to ancient times. In the Bronze Age,
humans realized that joining two metals provides the opportunity for new tools and
objects that could not be previously manufactured. This opportunity brought out the
invention of welding. In the 1800s, with the help of the discovery of the arc, the
arc welding process was first invented for the joining of lead plates [1]. Since then,
the science and application of metal joining has grown from strength to strength.
Many new metal joining techniques have been developed over all the years, both in
fusion and solid-state conditions. One of the recent additions to the list of solid-state
welding techniques is FSW.
The developmental history of FSW is quite interesting. Around the 1980s, it was
observed that aluminium (Al) and magnesium (Mg) alloys, because of their low
weight and higher strength to weight ratio, have enormous potential to be used in
various parts of machinery to reduce weight and fuel consumption. In a component
comprised of steel, substituting steel sub-components with lightweight alloys like Al
and Mg reduced the component’s overall weight, notably without making a significant
compromise in the strength. Researchers realized that using these alloys in various
industries could prove to be significantly economic and have environmental value. For
example, in automobile industries, vehicles built with lighter alloys would increase
fuel efficiency and reduce carbon emissions. The use of mechanical fasteners offset
weight reduction. Again, for traditional welding techniques, the high reactivity of
these lightweight alloys to oxygen in their molten state was found to be a severe
bottleneck that had to be eliminated to facilitate their use. The traditional welding
techniques available such as TIG, MIG, and resistance welding, showed limited
success, and the joint efficiency was unsatisfactory. These challenges, as well as the
defects generated during traditional welding techniques including porosity, voids,
distortion, and the formation of brittle intermetallics, motivated the researchers to
seek a better welding technique to overcome these problems related to the traditional
fusion welding techniques.
In 1991, The Welding Institute (TWI) invented the Friction Stir Welding Process
[2], an advanced solid-state joining process that can weld materials of different alloys
without reaching their molten state. FSW can weld similar or dissimilar materials,
especially the lightweight and reactive materials, that are otherwise hard-to-weld with
the available traditional welding processes like TIG and MIG. The FSW technique
was found to be superior to these traditional welding processes in other aspects as
well. FSW was found to be immune to the ill effects of re-solidification observed in
fusion welding processes. It produces zero pollutants, and hence can be termed as
‘green welding’ technique. The stress corrosion cracking related to the traditional
fusion welding processes is also absent in FSW.
P. Sarkar et al.
offered by this process. The process and its benefits are broadly explained in the
subsequent sections.
4.1.1 Development of FSW
The history of welding can be traced back to ancient times. In the Bronze Age,
humans realized that joining two metals provides the opportunity for new tools and
objects that could not be previously manufactured. This opportunity brought out the
invention of welding. In the 1800s, with the help of the discovery of the arc, the
arc welding process was first invented for the joining of lead plates [1]. Since then,
the science and application of metal joining has grown from strength to strength.
Many new metal joining techniques have been developed over all the years, both in
fusion and solid-state conditions. One of the recent additions to the list of solid-state
welding techniques is FSW.
The developmental history of FSW is quite interesting. Around the 1980s, it was
observed that aluminium (Al) and magnesium (Mg) alloys, because of their low
weight and higher strength to weight ratio, have enormous potential to be used in
various parts of machinery to reduce weight and fuel consumption. In a component
comprised of steel, substituting steel sub-components with lightweight alloys like Al
and Mg reduced the component’s overall weight, notably without making a significant
compromise in the strength. Researchers realized that using these alloys in various
industries could prove to be significantly economic and have environmental value. For
example, in automobile industries, vehicles built with lighter alloys would increase
fuel efficiency and reduce carbon emissions. The use of mechanical fasteners offset
weight reduction. Again, for traditional welding techniques, the high reactivity of
these lightweight alloys to oxygen in their molten state was found to be a severe
bottleneck that had to be eliminated to facilitate their use. The traditional welding
techniques available such as TIG, MIG, and resistance welding, showed limited
success, and the joint efficiency was unsatisfactory. These challenges, as well as the
defects generated during traditional welding techniques including porosity, voids,
distortion, and the formation of brittle intermetallics, motivated the researchers to
seek a better welding technique to overcome these problems related to the traditional
fusion welding techniques.
In 1991, The Welding Institute (TWI) invented the Friction Stir Welding Process
[2], an advanced solid-state joining process that can weld materials of different alloys
without reaching their molten state. FSW can weld similar or dissimilar materials,
especially the lightweight and reactive materials, that are otherwise hard-to-weld with
the available traditional welding processes like TIG and MIG. The FSW technique
was found to be superior to these traditional welding processes in other aspects as
well. FSW was found to be immune to the ill effects of re-solidification observed in
fusion welding processes. It produces zero pollutants, and hence can be termed as
‘green welding’ technique. The stress corrosion cracking related to the traditional
fusion welding processes is also absent in FSW.