## 3 Results
### XRD Phase Identification  
We utilized XRD analysis to identify the \(\beta\) phase. The identification of the strengthening phase presents challenges because the predominant peaks of aluminum from the aluminum matrix complicate intensity measurements, leading to potential confusion between the crystallographic planes of hexagonal aluminum corresponding to the \(\beta\) phase  
Figure 5: (**a**) Equiaxed grains on the heat-treated surface of a representative sample from the 7 th run of the DOE and (**b**) precipitates in the Al matrix on the surface of the same sample.  
Figure 6: EDS spectrum exhibiting (**a**) elements precursors of \(\beta\) phase (Al-Mg-Si) and (**b**) dispersoid-forming elements (Al-Fe-Si).  
and the FCC structure of the aluminum matrix. However, it is still possible to distinguish the \(\beta\) phase with careful analysis, as explained in the following paragraphs.  
Figure 7a presents the XRD pattern of the as-received sample; the highest peak corresponds to aluminum with (200) orientation. By zooming in on the spectrum in Figure 7b, the presence of the \(\beta\) phase (Mg\({}_{2}\)Si) with (220) orientation becomes more evident. Traces of the aluminum matrix with orientations (111) and (311) are also observed [41].  
Figure 8 shows the XRD spectrum corresponding to the sample that exhibited the lowest mechanical properties (1 st run), in which the presence of the \(\beta\) phase with orientation (220) is observed. The presence of aluminum peaks having the orientations (111), (220), and (311) is noticeable with greater relative intensity compared to the as-received sample.  
Figure 9 presents the XRD pattern of a representative sample from the 7 th run, subjected to a solubilization temperature of 540 \({}^{\circ}\)C for 3 h and aging at 170 \({}^{\circ}\)C for 18 h. It can be confirmed that the thermal treatment has induced recrystallization in the aluminum matrix. This is evident from the altered orientation of the aluminum diffraction peak initially observed at (200) in Figure 7. Furthermore, Figure 9 demonstrates a change in the relative intensity of other peaks, indicating the presence of the \(\beta\) phase in the alloy. According to the literature, the morphology of the \(\beta\) phase is typically observed in the form of plates or needles [11], as previously depicted in Figure 5, which corroborates the XRD findings. It is important to note that increasing the solution time can result in the dissolution of a more significant amount of the \(\beta\) strengthening phase, leading to increased hardening after the solution treatment [42]. Therefore, traces of the beta phase can be observed in Figures 7-9.  
The recrystallization of the aluminum matrix after the thermal treatment is a significant phenomenon in alloy processing. Recrystallization refers to forming new grains with a lower dislocation density and improved structural stability. In this case, the observed shift in the diffraction peak of aluminum (200) suggests a realignment of crystallographic planes, indicating the occurrence of recrystallization. The recrystallization process promotes the development of a more uniform and fine-grained microstructure, which can contribute to enhanced mechanical properties, such as increased strength and improved formability.  
Figure 7: (a) XRD spectra for 6061 aluminum alloy (as-received) at full scale; (b) amplification of the trace peaks.