# A Literature Survey on Electrical-Current-Assisted Friction Stir Welding
## 6 EA-FSW of Dissimilar Joints
### EA-FSW of Aluminum to Steel  
Aluminum-steel joints are the most popular joint produced by the FSW process. Due to the combination of base metals properties, the produced structure can be solid and lightweight. For this reason, the EA-FSW can improve the quality of this joint to reach a higher strength. [PERSON] et al. [48] investigated a dissimilar joint between AA16061 aluminum alloy and TRIP 780 steel by EA-FSW. They introduced a method where there is no need for the tool to be used as one of the electrodes, when in many similar procedures it is. They reported a significant reduction in the axial load applying the high-density current. They also reported the presence of micro interlocking in the joint's microstructure, which is considered beneficial for the joint quality. They concluded a promotion by forming a thin layer of IMC for the plunge section of the joint. The reason is the combined effect of accelerated atom diffusion and reduced activation energy for chemical reactions. The thickness of IMC in the EA-FSW case was similar to the FSW process with a high tool rotational speed. The electrical current helps decrease the shear strength of the base metal and increase the aluminum and steel interaction at the joint interface. The comparison between the IMC thickness of FSW and EA-FSW at the interface of the AA16061 aluminum alloy to TRIP 780 steel is presented in Figure 5.  
[PERSON] et al. [42] investigated the electrical current effects on the quality of dissimilar joints between aluminum alloy and advanced high-strength steel utilizing friction stir spot welding. In their setup, the aluminum alloy was placed on top, and the steel was  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Raw Material** & **Thickness** & **Type of Joint** & **Output Results** & **Ref.** \\ \hline AA6061 aluminum to AZ31B magnesium & 3 mm & Preheat & Material flow and mechanical properties & [31] \\ \hline
2 Cr13 Mn9 Ni4 stainless steel to Q235B steel & 2 mm & Preheat & Microstructure & [40] \\ \hline AA6061-T6511 aluminum to 1018 mild steel & 3 mm & Combine & Material flow and mechanical properties & [41] \\ \hline AA6061-T6 aluminum to TRIP steel & 2 mm & Combine & Material flow and mechanical properties & [42] \\ \hline
7075-T6 aluminum to glass fiber-reinforced & & & & \\ poly-ether-ether-ketone & & & & \\ \hline high-density polyethylene (HDPE) to 316L & 3 mm & Combine & Material flow and mechanical properties & [44] \\ stainless-steel textile & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Dissimilar joints welded by EA-FSW.  
placed at the bottom. They tried two approaches. First, they put two electrodes for passing electrical current on the top plate. In the second approach, they put one electrode on the top plate and the second on the bottom plate. They reported that using electrical current decreases the plunging force during the joining process and improves the joint strength. The average force value during electrical-assisted welding was near 13% less than without an electrical-assisted case. The electrical assist increased the aluminum flow in SZ, and the diffusion of aluminum elements in IMC increased.  
[PERSON] et al. [41] used two different tool materials and evaluated their effects on EA-FSW of the AA6061 aluminum alloy to mild steel. They made the FSW tool from tool steel and XSYTIN-1 ceramic base material. They stated that ceramic material decreases the maximum temperature in joint lines and the joint strength decreases. This change was related to the change in friction coefficient at the interface of the tool and workpieces. A lower friction coefficient at the interface of the XSYTIN-1 ceramic material with aluminum and steel leads to lower heat generation.