## 3 Results
### Fracture Mechanisms  
An interesting aspect of this study is the evaluation of the fracture mechanisms in the different experimental samples. First, we present the fractography shown in Figure 10, which corresponds to the sample from run 1, which exhibited the lowest UTS among all the samples. The fractographic analysis reveals the presence of microvoids, characteristic of ductile fracture. However, we also observe traces of cleavage, indicative of brittle fracture. Therefore, this sample exhibited a mixed fracture mechanism, combining both ductile and brittle features [43; 44].  
Figure 8: (a) XRD spectra for the heat-treated 6061 aluminum alloy at full scale (1 st run, worst case); (b) amplification of the trace peaks.  
Figure 9: (a) XRD spectra for the heat-treated 6061 aluminum alloy at full scale (7 th run, best case); (b) amplification of the trace peaks.  
In contrast, samples in the best condition (7 th run, which reported the best performance in the tensile test, achieving the highest UTS result) exhibited different fracture mechanisms. The fracture was predominantly ductile, as indicated by the white arrows highlighting the presence of dimples and micro-cracks, which are characteristic of ductile fracture, as depicted in Figure 11a. Furthermore, Figure 11b, captured at 300\(\times\) magnification, illustrates the presence of dimples and microvoids, reinforcing the observation that the specimen exhibits good ductility [8]. The rest of the samples, including the as-received materials, exhibit similar fracture behavior, demonstrating consistent ductile fracture characteristics across these conditions.  
The existence of distributed microvoids throughout the fractured aluminum matrix indicates good ductility and a favorable distribution of the strengthening \(\beta\) phase (Mg\({}_{2}\)Si). The formation of microvoids occurs due to various mechanisms, including grain boundary sliding and dislocation movement [16]. During tensile deformation, stress concentrations can lead to the nucleation and growth of microvoids, which subsequently coalesce and form larger voids. These voids are then observed as dimples on the fracture surface. The localized coalescence of microvoids into larger dimples results from the interaction between  
Figure 11: (**a**) Fracture zone micrograph of selected sample from 7 th run. (**b**) Magnification of the same sample exhibiting microvoids and dimples.  
Figure 10: (**a**) Fracture zone micrograph of selected sample from 1 st run. (**b**) Magnification of the same sample exhibiting microvoids and dimples.  
the plastic deformation mechanisms and the material microstructure. Grain boundaries, as well as dislocations, play a crucial role in this process. The sliding of grain boundaries and the movement of dislocations promote stress concentration around certain regions, leading to the nucleation and growth of microvoids. As deformation continues, these microvoids coalesce and form dimples, which are energy-absorbing features during the fracture process. A significant note is that fractographs obtained from tensile testing are more likely to reflect the plastic deformation ability of the material, corresponding to its elongation property, rather than solely indicating its strength. It is essential to consider that numerous factors, including the phases present within the material, influence the stress experienced by the material during testing.