## 1 Introduction  
Magnesium alloys display exceptional engineering properties because of their high specific strength, good machinability, stiffness, damping capacity, good weldability, and castability. These properties make them attractive for various industries, such as automobiles, aerospace, and electronics [1, 2]. However, these alloys possess poor formability, due to insufficient slip systems in the hexagonal close-packed (hcp) lattice at room temperature, which limits widespread application [3, 4]. Gas tungsten arc (GTA), metal inert gas (MIG), laser beam, electron beam, friction, friction stir, stud, spot welding, laser hybrid welding, and ultrasonic welding techniques are reported in the literature for the welding of Mg alloys [5, 6, 7, 8, 9, 10, 11]. The main problems of magnesium welding are in-flammability, oxide film formation, solidification cracking, columnar grains in the fusion zone, and porosity during solidification. The GTA welding technique used in this study has several advantages (good weld quality) over the other arc welding processes [12, 13, 14]. [PERSON] et al. [15] study the influence of different welding techniques (GTA, CO\({}_{2}\), and Nd: YAG laser) on the microstructure and mechanical properties of Mg-Al-Zn welds. They report that laser welds produce fine grain size compared to the GTA welds. It is observed that hardness reduction in the fusion zone (FZ) and the heat-affected zone (HAZ), compared with the base metal, is evident in GTA and laser welding techniques, attributed to the loss in strengthening effect of the weld thermal cycle. The influence of welding techniques, such as alternating current (AC), variable polarity mixed (VPM), alternating current pulsing (ACPC), and variable polarity (VP) techniques on the microstructure and mechanical properties of AZ31 GTA welds are reported by [PERSON] et al. [16]. They show that ACPCresults in significant grain refinement compared with un-pulsed welds. It is also shown that improved tensile strength, hardness, and ductility of ACPC welds are associated with the grain refinement mechanism obtained by weld pool agitation and dendrite fragmentation. [PERSON] et al. [17] investigate the influence of high-frequency vibration on the microstructure and mechanical properties (hardness and strength) of AZ31 alloy GTA welds. They suggest that the degree of grain refinement increases with the increased vibration amplitude, strongly affected by wave energy transferring to the weld pool. [PERSON] et al. [18] conduct detailed studies on grain refinement of AZ31 and AZ91 GTA welds using the arc oscillation technique. They observe that significant grain refinement is achieved through dendrite fragmentation. It is also shown that constitutional supercooling is significant in AZ91 welds, due to the high Al content compared to AZ31 welds. [PERSON] et al. [19] show that with decreasing heat input, the tensile strength of AZ31 laser welds increases, due to fast cooling rates and moderate concentration of precipitates. They report that the AZ31 alloy melt quickly solidifies because of rapid cooling employed in laser welding, and results in the precipitation of the Mg\({}_{17}\)Al\({}_{12}\) phase. [PERSON] et al. [20] compare and correlate the microstructure, hardness, and tensile properties of friction stir welded (FSW) AZ31B Mg with fusion welding techniques (GTA and laser welding). They report that the laser beam welded joints exhibit superior tensile properties (yield strength (YS): 174 MPa, ultimate tensile strength (UTS): 212 MPa and % elongation (% El): 12.1) compared to GTA welds (YS: 148 MPa, UTS: 183 MPa, % El: 7.6) and FSW joints (YS: 171 MPa, UTS: 208 MPa, % El: 11.8), which is attributed to the fine grains present in the fusion zone [20]. [PERSON] and [PERSON] [21] prepared AZ31 alloy GTA welds, with both AZ61 filler wire and without any filler. The welds prepared with AZ61 filler exhibit a UTS of 94% of base metal compared to welds without filler (90% of base metal).