146
P. Sarkar et al.
4.2.3 Defects Generated Due to Improper Mixing
Improper mixing is the result of many factors. The low heat generation and improper
geometry of the tool and its positioning lead to defects. Some of the usual defects
due to improper mixing are oxide entrapment, lack of penetration, excessive flash
generation, which are described below.
Oxide entrapment The oxide layer, formed by the material in the presence of
air, gets penetrated through the weld material during the welding. This hinders the
formation of a bond, which severely decreases the joint strength [33].
Lack of penetration If PD is not sufficient enough, the tool is then unable to mix
the material at the bottom of the plate thus reducing the joint strength [33].
Excessive flash This occurs if PD is very high due to the use of the required longer
tool pin. This leads to severe plasticization, as well as expelling of the plasticized
material from the stir zone creating thinning of the base plate [33].
By properly cleaning the workpiece material before welding and also selecting
the tool pin and shoulder geometry according to the material properties and can solve
the above-mentioned problems.
4.3 Recent Market Demands of FSW Process
Initially, with the use of milling machines, the FSW process was estimated to be a
laboratory-compatible process only. However, soon with the ample advantages over
the conventional joining process and also with constant growth in research in this
area, FSW has been proved to be one of the fastest-growing welding processes to be
adopted in the industrial sector just after four years, from its invention in 1991. ESAB
of Sweden realized the importance of the process and developed the industry-scale
FSW machines with many modifications [38]. Many other companies soon followed
the path; and now the market is full with a large variety of advanced FSW machines
for more complicated joining.
The 2xxx and 7xxx series aluminium alloys, which are considered impossible to be
welded with the traditional welding techniques, were successfully welded by FSW.
Later, this process proved itself compatible with numerous alloys and materials,
including magnesium (Mg), thick copper, high-strength steels, titanium, stainless
steel, and pure carbon steel. FSW also successfully joined the dissimilar materials.
The invention of FSW changed the fabrication ways for various components used
in different industries, namely aerospace, automotive, shipbuilding, etc. [25]. The
constant requirement of light-weightiness without compromising the strength due to
low carbon emission and less fuel consumption is the prime factor for the increasing
demand for the FSW process. This factor is projected to increase the global market of
FSW by USD 885.55 Million increasing the CAGR by 6.9% in the forecast period of
P. Sarkar et al.
4.2.3 Defects Generated Due to Improper Mixing
Improper mixing is the result of many factors. The low heat generation and improper
geometry of the tool and its positioning lead to defects. Some of the usual defects
due to improper mixing are oxide entrapment, lack of penetration, excessive flash
generation, which are described below.
Oxide entrapment The oxide layer, formed by the material in the presence of
air, gets penetrated through the weld material during the welding. This hinders the
formation of a bond, which severely decreases the joint strength [33].
Lack of penetration If PD is not sufficient enough, the tool is then unable to mix
the material at the bottom of the plate thus reducing the joint strength [33].
Excessive flash This occurs if PD is very high due to the use of the required longer
tool pin. This leads to severe plasticization, as well as expelling of the plasticized
material from the stir zone creating thinning of the base plate [33].
By properly cleaning the workpiece material before welding and also selecting
the tool pin and shoulder geometry according to the material properties and can solve
the above-mentioned problems.
4.3 Recent Market Demands of FSW Process
Initially, with the use of milling machines, the FSW process was estimated to be a
laboratory-compatible process only. However, soon with the ample advantages over
the conventional joining process and also with constant growth in research in this
area, FSW has been proved to be one of the fastest-growing welding processes to be
adopted in the industrial sector just after four years, from its invention in 1991. ESAB
of Sweden realized the importance of the process and developed the industry-scale
FSW machines with many modifications [38]. Many other companies soon followed
the path; and now the market is full with a large variety of advanced FSW machines
for more complicated joining.
The 2xxx and 7xxx series aluminium alloys, which are considered impossible to be
welded with the traditional welding techniques, were successfully welded by FSW.
Later, this process proved itself compatible with numerous alloys and materials,
including magnesium (Mg), thick copper, high-strength steels, titanium, stainless
steel, and pure carbon steel. FSW also successfully joined the dissimilar materials.
The invention of FSW changed the fabrication ways for various components used
in different industries, namely aerospace, automotive, shipbuilding, etc. [25]. The
constant requirement of light-weightiness without compromising the strength due to
low carbon emission and less fuel consumption is the prime factor for the increasing
demand for the FSW process. This factor is projected to increase the global market of
FSW by USD 885.55 Million increasing the CAGR by 6.9% in the forecast period of