# Mechanical Properties Analysis of WAAM Produced Wall Made from 6063 Alloy Using AC MIG Process
## 3 Results and Discussion
### Microstructure Characterization  
The microstructural analysis of the samples was conducted using an Olympus GX51 light microscope with a depth of field of \(0.2\)\(\upmu\)m. The microstructural observations were carried out on macrosections made from cross-sections of the walls produced with WAAM. Figure 3: Macroscopic view of the samples (**a**) sample \(11\), (**b**) sample \(12\), (**c**) sample \(13\) and (**d**) sample \(14\). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **Sample Width, mm** & **Sample Height, mm** \\ \hline
**11** & 9.1 & 92.3 \\
**12** & 10.6 & 71.6 \\
**13** & 12.1 & 57.1 \\
**14** & 12.5 & 64.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Macroscopic characterization. The observations were carried out at several points, particularly in the middle and upper areas of the walls, in order to determine representative microstructural features and the presence of specific defects. Figure 4a illustrates the microstructure of aluminum alloy 6063 in sample 11, which was produced using WAAM. The grains are predominantly regular in shape, polygonal, and uniform in size. Within the deposited layer, a uniform and homogeneous microstructure is observed, characterized by clearly defined aluminum grain boundaries along which intermetallic phases (precipitates) have formed. This suggests favorable and stable thermal conditions during solidification. Among the typical defects associated with WAAM processing of aluminum alloys, only gas pores of varying sizes were observed. Similar grain morphology and refinement trends were also observed in studies by [PERSON] et al. [18] and [PERSON] et al. [19], who investigated WAAM processing using a structurally refined Al-Mg-Si filler wire and reported fine equiaxed grains with min  
Figure 4: Microstructure of the aluminum alloy 6063 of produced with WAAM: (**a**) microstructure of sample 11, (**b**) three successive layers of sample 11, (**c**) microstructure of sample 12, (**d**) microstructure of sample 13, (**e**) microstructure of sample 14, and (**f**) intermetallic precipitates between two layers of sample 14.  
imal columnar growth, supporting the effectiveness of TiB\({}_{2}\) additions in promoting a uniform microstructure. Figure 4b shows three successive layers of sample 11, each exhibiting differences in grain size and morphology. These variations are attributed to the partial recrystallization of the previous layer, induced by repeated thermal cycling during deposition. The distinct separation between the layers indicates local thermal gradients and varying solidification conditions. Some porosity is also observed, likely caused by gas entrapment during solidification. This, along with the microstructural inhomogeneity, may influence the overall mechanical performance of the part. Figure 4c presents the microstructure of sample 12, which shares similarities with the features observed in sample 11. The solidification patterns seen can be attributed to the heat dissipation trajectories resulting from subsequent thermal passes, suggesting directional solidification influenced by localized thermal gradients. In the Al 6063 alloy, the central aluminum matrix has a higher melting point than the intermetallic precipitates, which normally form at the grain boundaries. During the WAAM process, additional segregation and precipitation of these phases occur at the boundaries of the individual deposition layers due to multi-layer welding (Figure 4d,f). Figure 4e displays the microstructure of sample 14, produced via DC-MIG welding. A high density of medium-sized, rounded pores is clearly visible. The average pore diameter ranges from 30 to 50 \(\upmu\)m, with some pores locally exceeding this range. The microstructure is characterized by a predominance of equiaxed grains, indicating relatively uniform solidification conditions. However, compared to the microstructures obtained during AC-MIG welding, this structure appears coarser, suggesting a different heat input and cooling behavior during DC-MIG deposition.