*1.4. Welding Techniques Examined*

In recent times, alternative welding techniques have been successfully applied to aluminum alloys. MIG welding is an electric arc welding process that uses a continuously fed wire into the weld pool. It can be used to join long stretches of metal without stopping. Among the main advantages of this type of weld are that good quality welds can be produced much faster and there is flexibility for a wide variety of alloys. In addition, thanks to the gas protection, there is very little loss of alloying elements. Unfortunately, MIG welding cannot be used in vertical or overhead welding positions because of the high heat input, the fluidity of the weld puddle, and the complexity of the equipment [11,39].

CMT is a form of modified MIG welding based on the short-circuiting transfer process that guarantees interesting achievements such as process stability, reproducibility, and cost-effectiveness. This process differs from MIG welding only in the type of mechanical droplet cutting method that provides controlled material deposition and low thermal input by incorporating an innovative wire feed system coupled with a high-speed digital control. The two main advantages of the CMT process are the low heat input and the occurrence of short circuits in a stable controlled manner [40–43].

Laser welding is a very interesting joint process due to the high welding speed, smaller heat-affected zone (HAZ), and low deformation. Unfortunately, the high cooling rates can lead to the formation of hardening structures that increases hardness, decreases plasticity of the weld joint and HAZ, and increases the level of residual stresses. Fiber laser welding is one of many laser processes where the laser light is generated in a remote source and guided to the work piece by a flexible delivery optic fiber. The main benefits of this type of weld are the good beam quality, high precision control, lower heat input, lower electrical energy consumption, low cost of maintenance, and compact size. Welding with the laser technique requires alignment, fixation, and welding process control. This critical procedure can be solved by using the twin spot laser technique with filler wire or hybrid arc-laser welding, but will decrease the welding speed. One of the ways to solve this problem is the use of laser beam wobbling mode [11,12,44–50].
