**3. GMAW**

GMAW is also known as metal inert gas (MIG) welding in which an external gas, such as argon, helium, carbon dioxide, argon + oxygen, and other gas mixtures, is used as a shielding gas [1]. Consumable electrode wire, having the same or approximate chemical composition to that of parent metal, is continuously fed from a spool to the arc zone. The arc from the welding parameters (voltage and current) heats and melts the samples' edges and the filler wire. The fused filler metal is supplied to the surface of the workpiece, fills the weld pools, and forms the joint between the workpieces similarly or dissimilarly. The overall process in GMAW is described as a semi-automatic method because of the automatic feeding of the filler rod while the welder controls only the position and speed of the torch. GMAW can weld almost all metals and alloys, aluminum alloys, and stainless steel [2].

properties of the parent metal. There are two types of welding area, namely conduction or keyhole mode. The obvious width and depth difference in this welding area is due to the

Introductory Chapter: A Brief Introduction to Joining and Welding

http://dx.doi.org/10.5772/64726

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Laser welding has many advantages over the conventional joining method, such as deep penetration, low heat input, small heat-affected zone (HAZ), and high speed. In terms of production, some of the advantages of laser welding are high speed, high process productivity, flexibility in control, and automation. Three common types of laser machines, namely CO2, Nd:YAG, and fiber lasers, are widely used in the industry for welding purposes. CO2 is known as a gas laser with a wider wavelength compared with solid-state lasers Nd:YAG and fiber lasers. Unlike solid-state lasers, the wide wavelength of the CO2 laser results in poor absorption by a wide range of materials. Meanwhile, the fiber laser presents several advantages over the Nd:YAG laser because of the former's compact design, good beam quality, and low cost of

FSW is a welding process that involves solid-state joining; this process has expanded rapidly since its development in 1991 by The Welding Institute, UK [3–6]. FSW is a solid-state welding technique that does not involve melting and occurs below the melting point. It uses a rotating tool to generate necessary heat for welding. This tool consists of three parts: the shank, shoulder, and pin. The shank is the part where the tool is attached to the FSW machine, whereas the shoulder and pin are attached to the workpiece. The shoulder and pin provide additional frictional treatment and prevent the plasticized material from escaping from the weld region. During FSW, the rotating tool moves along the joint of two plates that generate heat. This tool then recirculates flow of the plasticized material near the tool surface. The size of the tool shoulder is larger than that of the pin tool. The FSW tool serves two main functions, namely workpiece heating and material movement to produce a joint [4]. Heating is produced by friction of the pin and workpiece and plastic deformation of the workpiece. The heat that is produced will soften the material around the pin, and tool rotation will move the material from the front of the pin to the back of the pin. The result of this process is a joint produced in solid

FSW can be utilized in a wide variety of industries, such as automotive, aerospace, maritime, and railway [3, 4, 7–11]. FSW has been considered the most substantial joining process in the past decade because it offers many advantages such as energy efficiency, environmental friendliness, and versatility [4]. Compared with arc welding, FSW uses less energy and does not require a shielding gas and flux, thereby making this process an eco-friendly one. This joining process does not need any filler, so it is suitable to join many types of dissimilar metals. FSW is a technique that can avoid drawbacks from common fusion welding because FSW can be conducted under solid state. Several problems (e.g., spatter, hot cracking, and distortion) in other types of welding are eliminated by using FSW [12]. Defects such as voids, lack of

penetration, and broken surface can be minimized by using this welding technique.

energy *E* and peak power density *PPD* applied.

ownership and maintenance.

**6. FSW**

state.
