# Mechanical Properties Analysis of WAAM Produced Wall Made from 6063 Alloy Using AC MIG Process
## 3 Results and Discussion
### Tensile Properties  
Tensile specimens were extracted from different samples, all oriented horizontally to the deposited build. Figure 7 presents the stress-strain curves for all samples, while Table 4 provides a comparison of the ultimate tensile strength (UTS), yield strength (YS) and elongation (\(\epsilon\)) at room temperature for the different samples. The narrow ranges of UTS and YS (excluding the value for sample 11A) indicate stable strength properties of the deposited material. In contrast, the comparatively broader range of elongation suggests lower stability in ductility properties relative to strength. Overall, the maximum UTS values were obtained in samples extracted from the bottom part of the WAAM-produced wall (designated as \"B\" samples).  
Due to slippage during gripping, sample 11B exhibited an unusually high initial stress of about 40 MPa, in contrast to the other specimens, which started near zero. This probably affected the accuracy of the yield strength. However, the ultimate tensile strength (UTS) is still considered reliable as the fracture occurred within the gauge length, indicating that the sample experienced proper deformation and failure despite the initial slippage.  
In the WAAM production process, cooling and heating rates are not uniform along the build-up direction. Samples taken from the bottom region, near the substrate, experience rapid cooling (compared to samples extracted from the upper region of the wall) as layers are deposited onto the cooled substrate. This cooling effect promotes fine grain formation, leading to increased strength (up to 172 MPa) in the bottom region. Additionally, the subsequent \"heat treatment\" from the electric arc of the following deposited layers positively affects the mechanical properties.  
The effect of heat input and distribution can also be observed when analyzing the UTS value of sample 14B. Although the heat input is almost the lowest, the distribution of heat  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **UTS,** & \multirow{2}{*}{**\(\epsilon\), /**} & \multirow{2}{*}{**YS, MPa**} & \multirow{2}{*}{**Sample**} & **UTS,** & \multirow{2}{*}{**\(\epsilon\), /**} & \multirow{2}{*}{**YS, MPa**} \\  & **MPa** & & & & & & \\ \hline
**11A** & 135.72 & 0.103 & 99.93 & **11B** & 164.84 & 0.204 & 70.06 \\
**12A** & 151.42 & 0.182 & 70.03 & **12B** & 151.43 & 0.173 & 69.95 \\
**13A**  
is primarily directed to the deposited layer, which acts as a heat treatment for the produced layers and ultimately plays a beneficial role in improving mechanical properties.  
The mechanical properties achieved in this study--particularly the ultimate tensile strength (UTS) of up to 172 MPa--are in good agreement with the results of [PERSON] et al. [PERSON] et al. (2019), who also investigated WAAM-manufactured components using a TiB\({}_{2}\)-modified Al-Mg-Si filler wire. Their study yielded comparable UTS and yield strength values, confirming that the use of structurally refined filler wire enables stable and competitive mechanical performance in WAAM-produced aluminum alloys.  
Among the tested samples, those with higher porosity also tended to have lower UTS values. This can be explained by the fact that increased porosity leads to stress concentrations that act as crack initiation points under tensile loading. This reduces the effective load-bearing cross-section and thus leads to a measurable reduction in ultimate tensile strength. This correlation reinforces the importance of controlling the process parameters, not only for the geometry but also for the mechanical performance.