## 3 Results  
### Macroscopic Analysis and Roughness  
Figure 2 is a single thin-walled wall profile obtained using the AlMg4,5 Mn CMT process (see Table 2 for the corresponding process parameters of different group numbers). Group 1 and Group 2 were continuously formed at 132.2 mm and 70.9 mm, respectively. It can be seen that the side of the swing-welded specimen is smooth, but the hump phenomenon appears, and the side profile fluctuates greatly. Pure CMT is prone to flow during the deposition process, resulting in a rough local surface.  
Figure 3 is the profile of the single thin-walled wall of Group 3 using the Mg alloy CMT process. It can be seen that the CMT mode under the Mg alloy CMT process has a smooth surface, but the spreading effect is poor. When the wire filling speed increases to 7 m/min, the first and the second layers' morphology is improved, and the fish scale is clearer and more uniform, but the hump still appears in the subsequent forming, resulting in some voids in the sample. The deposited layer surface in the swing welding process is smooth, the spreading effect is better, and the fish scales are clear and evenly distributed.  
Figure 1: Model and physical diagram of tensile specimen.  
Figure 3: Side-wall profile of No. 3: (**a**) first layer, (**b**) second layer, (**c**) overview.  
Figure 2: Side-wall morphology of magnesium deposited sample: (**a**) overview of No. 1, (**b**) No. 1, (**c**) No. 2.  
Figure 4 is the profile of the single thin-walled wall of Group 3 using the Mg alloy CMT process. When the scanning speed is 6 mm/s, the surface of the first layer is not smooth, and the distribution of fish scales is not dense. Local splashing will occur during subsequent forming, resulting in uneven local areas on the side. When the scanning speed is reduced to 4 mm/s, the surface of the first layer is bright and smooth, and the fish scales are densely distributed, so the forming is stable. The side is well distributed with fish scales, and the surface is flat. This shows that the lower scanning speed increases the heat input, which in turn increases the fluidity of the liquid metal.  
Figure 5 shows the side-wall scanning contour results of a single thin-walled wall. The surface roughness (Ra) and machining allowance of Group 1 and Group 2 using the AlMg4,5 Mn CMT process are not notably different. The Ra and machining allowance of Group 5 using the Mg alloy CMT process are the minimum values, which are 146.1 \(\upmu\)m and 2.2 mm, respectively, and they are 24.7% and 29% lower than those of Group 4 (194 \(\upmu\)m and 3.1 mm). In addition, the Ra of Group 4 is 90% higher than that of the HWMM-produced Al5 Si aluminum sample [31]. At the same time, the Ra and machining allowance of Group 5 are reduced by 21.9% and 4.3%, compared with the minimum value in the AlMg4,5 Mn CMT process. In addition, the deviations of Ra and machining allowance in Group 1 are the largest among the four groups, and they are 68.9 \(\upmu\)m and 0.9 mm, respectively. The deviation of the Ra and machining allowance in Group 5 is 8.4 \(\upmu\)m and 0.1 mm, respectively, being 88.4% and 88.9% lower than that in Group 1. Therefore, the swing welding Mg alloy process deposition is better. This better process parameter includes the wire feeding speed of 12 m/min, the scanning speed of 4 mm/s, the swing welding frequency of 5 Hz, and the amplitude of 8 mm.  
Figure 4: Single layer morphology, (**a**) No. 4, (**b**) No. 5; overview, (**c**) No. 4, (**d**) No. 5.  
Figure 5: (**a**) Side-wall scanning contour, (**b**) surface roughness (Ra) and machining allowance.