5 Welding of Dissimilar Metals—Challenges and a Way Forward …
169
devising proper development of required metals, and use of advanced integration
technologies [3].
5.1.1.3 Aerospace
Aviation has been one of the major factors of global warming and environmental
pollution. This is because of the fuel being consumed. Light-weight structures
have been an effective way to increase energy efficiency and decrease the rate of
fuel consumption. An example in this regard is the Boeing 787 airline, which has
mentioned a 20% increase in fuel efficiency with a weight saving of 20% [4].
5.2 Welding—A Permanent Joining Approach
Welding is a permanent joining process performed either in a fusion state or a solidstate. Both these approaches have several different techniques for joining. Broadly,
fusion welding produces a bond in which the base materials are chemically bonded
because of the melting phenomenon. The process may use filler material as well.
Some of the well-known techniques of fusion welding are: (a) gas metal arc gas
(GMAW) welding, (b) gas tungsten arc (GTAW) welding, (c) laser beam welding
(LBW), and (d) electron beam welding (EBW). With regard to the joining of dissimilar metals, the major demerits of these techniques are the melting and solidification
of the base materials. Another important challenge with fusion welding is that it
results in defects, such as porosity, oxidation of the molten metal, micro-segregation,
hot cracking, etc., deteriorating the performance of the joint. Larger heat input in
the case of fusion welding techniques leads to a wider heat-affected zone (HAZ),
which degrades the mechanical properties of the joints. Some of these challenges
and limitations are avoided in solid-state welding processes.
As the name suggests, in a solid-state welding method no melting happens; thus
the protection of weld pool is not a concern here. The techniques in this approach are:
(a) friction welding, (b) explosion welding, (c) friction stir welding (FSW), and (d)
ultrasonic welding. Mostly, joints produced with these techniques retain the original
properties of the substrate. In this case, the HAZ is very narrow as compared to the
one produced in any of the fusion welding techniques because of the lower heat input.
The major advantage comes with their ability to join dissimilar metals together. The
thermal expansion is not severe in these processes as the joining phenomenon occurs
below the melting temperature of the materials [5].
169
devising proper development of required metals, and use of advanced integration
technologies [3].
5.1.1.3 Aerospace
Aviation has been one of the major factors of global warming and environmental
pollution. This is because of the fuel being consumed. Light-weight structures
have been an effective way to increase energy efficiency and decrease the rate of
fuel consumption. An example in this regard is the Boeing 787 airline, which has
mentioned a 20% increase in fuel efficiency with a weight saving of 20% [4].
5.2 Welding—A Permanent Joining Approach
Welding is a permanent joining process performed either in a fusion state or a solidstate. Both these approaches have several different techniques for joining. Broadly,
fusion welding produces a bond in which the base materials are chemically bonded
because of the melting phenomenon. The process may use filler material as well.
Some of the well-known techniques of fusion welding are: (a) gas metal arc gas
(GMAW) welding, (b) gas tungsten arc (GTAW) welding, (c) laser beam welding
(LBW), and (d) electron beam welding (EBW). With regard to the joining of dissimilar metals, the major demerits of these techniques are the melting and solidification
of the base materials. Another important challenge with fusion welding is that it
results in defects, such as porosity, oxidation of the molten metal, micro-segregation,
hot cracking, etc., deteriorating the performance of the joint. Larger heat input in
the case of fusion welding techniques leads to a wider heat-affected zone (HAZ),
which degrades the mechanical properties of the joints. Some of these challenges
and limitations are avoided in solid-state welding processes.
As the name suggests, in a solid-state welding method no melting happens; thus
the protection of weld pool is not a concern here. The techniques in this approach are:
(a) friction welding, (b) explosion welding, (c) friction stir welding (FSW), and (d)
ultrasonic welding. Mostly, joints produced with these techniques retain the original
properties of the substrate. In this case, the HAZ is very narrow as compared to the
one produced in any of the fusion welding techniques because of the lower heat input.
The major advantage comes with their ability to join dissimilar metals together. The
thermal expansion is not severe in these processes as the joining phenomenon occurs
below the melting temperature of the materials [5].