**1. Introduction**

The welding process is a significant issue in metal industrial applications such as automotive, aerospace, electronics, and medical functions. Friction stir spot welding (FSSW) is known as a solid-state metal joining process that is applied to join two dissimilar metal plates. It is most often utilized when the combination of metals through fusion welding is not applicable. In this process, a welding tool, including a shoulder and a pin, is rotated, and then contact with workpieces is going to be joined. This process includes three main steps: plunging, stirring, and drawing out [1–3]. In the plunging step, the rotating tool with the pin plunges and penetrates the joining

workpieces until the shoulder contacts the surface of the up workpiece and reaches the desired depth. Due to friction between the tool and workpiece heat is generated. The heated and softened material around the pin deforms plastically in the stirring step and the two workpieces are mixed. In the drawn-out step, the solid-state bonding between the upper and lower workpieces is achieved. The most important parameters of FSSW include rotational speed (RS) of the tool, dwell time, plunging rate, and plunge depth. These parameters are the key parameters for the size of the stirred zone during welding and weld outcome.

Several welding procedures and several applications for FSSW have been reported [4–8]. Czechowski [9] studied the effect of corrosion cracking on various aluminum alloys during the friction stir welding process. The heat generation analysis in the FSSW process of aluminum alloys was carried out by Awang and Muncino [10]. The results showed that most of the heat (around 96.84%) was produced from friction at the interface of the tool and workpiece. Matori et al. [11] investigated the corrosion properties of AA6061-T6 joint obtained using FSSW. The effect of pin length on the FSSW process for dissimilar aluminum and steel joints was studied by Piccini and Svoboda [12]. It was found that the maximum tool load value increases as tool penetration depth increases and the pin length decreases. Mechanical properties of the weld produced between AA6082-T6 sheets via FSSW were investigated by Aydin et al. [13]. The results showed that the tensile shear load increased almost linearly with increasing plunge depth. Jedrasiak et al. [14] determined the thermal modeling of FSSW for Al-Al and Al-steel joints. It was reported that the results gave a noticeable quantitative prediction of the radial diversity of the thickness of the intermetallic layer. FSSW for automotive applications was studied by Capar et al. [15].

Chevan and Shete [16] studied the optimization of FSSW parameters by using of Artificial Neural Network (ANN). It was found that the FSSW provided the maximum lap shear strength of 3.749 N/mm2 on the tool rotation speed of 900 rpm and dwell time of 30 sec for the taper cylindrical pin. Astarita et al. [17] studied the stress corrosion behavior of joints made by FSSW between aluminum alloys for aeronautic applications. It was reported that the weld area has lower resistance to intergranular and pitting corrosion compared to other areas. Shekhawat and Nadakuduru [18] analyzed the bonding zones during the FSSW in underwater and normal conditions for Al6061-T6 alloys.

Rostamiyan et al. [19] mixed two welding methods, including FSSW, and ultrasonic welding to improve the weld quality. In their research, FSSW was performed by the ultrasonic vibration of the tool. The impact of process parameters namely vibration, tool rotary speed, tool plunge depth, and dwell time on mechanical properties such as lap-shear force and hardness were examined. It was reported that introduce of vibration enhanced the lap shear force and hardness. Ji et al. [20] introduced the "ultrasonic-assisted friction stir spot welding" (UAFSSW) technique. This process was employed to join dissimilar AZ31and AA6061alloy sheets. It was shown that ultrasonic vibration was significant for the upward flow of the bottom plate and to get a flawless joint. It was found also that the existence of ultrasonic vibration improved the stir zone width and led to finer grains in the stir zone.

In this research, a new method to increase the efficiency of FSSW is presented. The workpiece is vibrated normally to the tool plunge path while the tool is rotated. This new method is entitled friction stir spot vibration welding (FSSVW). Mechanical properties of friction stir spot vibration (FSSV) welded samples such as hardness, fracture surface, and shear strength are compared with those from friction stir spot (FSS) welded samples.

*Study on Microstructure Evolution and Mechanical Properties of Al5083 Joint Obtained… DOI: http://dx.doi.org/10.5772/intechopen.102082*
