*Challenges and Advances in Welding and Joining Magnesium Alloy to Steel DOI: http://dx.doi.org/10.5772/intechopen.101862*

mechanism revealed that with the addition of suitable interlayers, the joint shear strength could reach a significantly high value or even surpasses Mg alloy BM.

Generally, the corrosion behavior of magnesium alloys is affected by the microstructural variation imposed by welding process [27, 43, 56, 63, 64, 125, 126, 131]. For similar Mg/Mg welds, the grain refinement imposed by welding process was reported to improve the corrosion resistance [132]. However, Liu et al. studied the corrosion behavior of the magnesium to steel joints produced by TIG-assisted laser process in NaCl solution. It was found that the grain refinement and iron splashes imposed by welding process were observed in the weld, which accelerated the corrosion of the magnesium alloy. Interestingly, the use of Al coating was reported to raise the lifespan of the dissimilar joints [47].

A comparison of the Mg alloys/steel joints maximum tensile shear strength produced by laser-TIG process is shown in **Table 6**. In hybrid laser-TIG welding, excessive vaporization of the magnesium was observed due to the penetration of the laser


#### **Table 6.**

*Comparison of the magnesium alloys/steel joints maximum tensile shear strength produced by laser-TIG process.*


*Challenges and Advances in Welding and Joining Magnesium Alloy to Steel DOI: http://dx.doi.org/10.5772/intechopen.101862*

#### **Table 7.**

*Comparison of the Mg alloys/steel joints maximum tensile shear strength produced by MIG welding brazing.*

from upper magnesium plate and the interlayer into the bottom steel. Furthermore, the violent stirring of molten pool restricted metallurgical bonding adjacent to the steel interface, which limited the application of this welding technique. Despite the fast heating and cooling rate of the TIG-assisted laser process, the interfacial reaction was achieved through diffusion and combination of alloying elements from the BM. Based on the existing literature, the interfacial characteristics and the mechanism of wetting in Mg alloys to steel joints produced using TIG-assisted laser process with addition of interlayers were thoroughly investigated. The feasibility of using Cu, Ni, Sn, Zn, and Cu-Zn intermediate elements was also explored. The presence of interlayer was essential for successful joining Mg to steel. The selection of a suitable interlayer was essential for successful bonding. For instance, the Sn added joint shows comparatively lower value due to inhomogeneous compositions in the FZ. A comparison of the joints mechanical properties shows that excellent static strength has been achieved, even surpassing that of magnesium alloy base metal with insertion of Cu and Ni intermediate elements. The high joint shear strength obtained was associated with better wettability and deeper penetration in the weld. However, limited studies focused on corrosion behavior of the TIG-assisted laser magnesium to steel joints. Furthermore, no study has focused on the behavior of the joints under dynamic loading.

#### *3.2.3 Arc welding*

Arc welding involves joining the materials surface permanently using power supply to obtain an electric arc between the electrode mounted in a torch and a metal. Among the arc welding processes, so far only metal inert gas welding has been used for this material combination.

Metal inert gas (MIG) welding has been widely used in automobile industries due its inherent properties, such as high efficiency, lower cost, and excellent adoptability to material geometry [133, 134]. Therefore, obtaining a reliable Mg alloy to steel joint by MIG welding is essential. However, joining magnesium to steel by MIG is rarely reported, including AZ31B/Zn-coated steel [99, 101, 102, 135], AZ31B/Q235 with Cu interlayer [72, 100] and AZ31B/Aluminized steel [102]. Generally, the addition of suitable interlayer improves the spreadability and the nucleation of magnesium on the steels.

Cold metal transfer (CMT) modified gas metal arc welding of AZ31B Mg to galvanized and bare mild steel sheets showed that welded brazed joints formed in both joints [99, 101].

A comparison of the Mg alloys/steel joints maximum tensile shear strength produced by MIG welding brazing is shown in **Table 7**. Generally, the investigation on the Mg alloys/steel joints produced by MIG welding is still in its infancy. Therefore, more interlayers should be tested. Moreover, the behavior of the joints under dynamic loading should be studied.
