# Mechanical Properties Analysis of WAAM Produced Wall Made from 6063 Alloy Using AC MIG Process
## 4 Conclusions  
In the present work, the mechanical properties and microstructural characteristics of WAAM walls made of aluminum alloy 6063 using the AC-MIG process were investigated. The results show that polarity balance significantly influences wall geometry, porosity and grain structure. A higher electrode-negative (EN) ratio (AC balance 50) resulted in taller and narrower walls with reduced porosity, while a higher positive polarity (AC balance \(-\)50) resulted in wider walls. Microstructural analysis revealed predominantly equiaxed and polygonal grains with minimal defects, with gas pores being the only typical WAAM  
Figure 9: Distribution of longitudinal residual stress along the line A-B (Figure 6).  
related defects. Although the DC-MIG samples exhibited slightly coarser grains, they also showed a higher density of gas pores. The highest average hardness was measured in samples produced with balanced polarity (EN = 0), but due to the relatively high standard deviations, the observed differences were not statistically significant. The tensile test showed stable mechanical performance for all samples, with the highest tensile strength (172 MPa) measured in the lower region of the DC-MIG sample, which is probably due to rapid cooling near the substrate. Residual stress analysis showed that the DC-MIG samples had the highest surface stress values, while the AC-MIG samples showed lower stresses with a characteristic tensile-compressive-tensile pattern. Among the AC-MIG samples, sample 11--which reached the highest build-up height--also exhibited the highest tensile residual stress, suggesting a correlation between structure height and residual stress accumulation.  
Conceptualization, I.G.; methodology, I.G., M.J. and M.S.; validation, M.P., D.S. and I.G.; formal analysis, M.J.; investigation, M.P.; resources, I.G.; data curation, M.P. and D.S.; writing--original draft preparation, M.J. and M.S.; writing--review and editing, M.J.; visualization, M.J. and M.P.; supervision, I.G. and D.S. All authors have read and agreed to the published version of the manuscript.  
This work was partly supported by the Croatian Science Foundation under the project number HRZZ-IP-2022-10-9298 (REAL-fit: Reliable design methods for aluminium structures fit for the future requirements, project leader: [PERSON]).  
Not applicable.  
No new data were created or analyzed in this study.  
The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} WAM & Wire And Arc Additive Manufacturing \\ DED & Direct Energy Deposition \\ DC-MIG & Direct Current Metal Inert Gas Welding \\ AC-MIG & Alternating Current Metal Inert Gas Welding \\ XRD & X-ray Diffraction \\ WA-DED & Wire Arc Direct Energy Deposition \\ BTF & Buy-To-Fly \\ GMAW & Gas Metal Arc Welding \\ CMT & Cold Metal Transfer \\ CMT-P & Cold Metal Transfer-Pulsed \\ CMT-ADV & Cold Metal Transfer- Alternating Polarity \\ CMT-PADV & Cold Metal Transfer-Pulsed Alternating Polarity \\ VP-GMAW & Pulsed Variable Polarity Gas Metal Arc Welding \\ EN & Electrode Negative \\ UTS & Ultimate Tensile Strength \\ YS & Yield Strength \\ HV5 & Vickers Hardness (5 kg load) \\ TiB\({}_{2}\) & Titanium Diboride \\ \end{tabular}