## 3 Results
### Microstructure Characterization  
The microstructure of the profiles was fully recrystallized with a mean grain size of 56 \(\upmu\)m (Figure 2a). The grains of the outer and inner surface layers (surface zone) of 200-250 \(\upmu\)m thickness exhibited different orientations, which rendered different anodizing responses to the specific regions after [PERSON] electrolytic etch (Figure 2b). In the mid-thickness, the grains were not easily identified because of the strong extrusion texture resulting from the hot extrusion process. No differences were detected on the microstructure among the WQ, AC, and SC samples regarding the grain size, morphology, and texture, as these were formed during extrusion and they were not affected by the subsequent laboratory heat treatment. Upon the examination of the bent region of the three-point bent SC specimen, it was discovered that \"orange peeling\" and microcracking developed on the outer surface, with a maximum crack depth of 25 \(\upmu\)m (Figure 2c). However, more pronounced microcracking was observed in the subsurface region, between the surface zone and the mid-thickness region. Moreover, it was observed that surface roughening and the formation of shear bands coincided with the development of intergranular discontinuities, predominantly not only on the surface, but also in the subsurface regions. These discontinuities could occur due to strain accommodation differences in neighboring grains and were formed along grain boundaries. Shear bands were also observed in traversing different grains on the surface and subsurface regions, characterized by intergranular cracks with approximately 100 \(\upmu\)m in size, coinciding with the location of slip bands that extended from the surface to the interior of the profile. In addition, the formation of discontinuities was observed between constituent intermetallic particles, both intergranularly and transgranularly. The optical and electron microscopy analysis of the intermetallic particles' size, morphology, and general appearance in this particular type of Al-alloy provided typical evidence of AlFeSi secondary phases that underwent deformation during processing (extrusion). The intermetallic particles not only served as sites for discontinuities formation during bending testing, but also promoted cracking due to their inherent brittleness. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **TS (MPa)** & **YS (MPa)** & **EI. (\%)** \\ \hline WQ & 315 & 304 & 12.1 \\ AC & 284 & 241 & 9.6 \\ SC & 310 & 298 & 12.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Tensile test results (mean of five measurements). Figure 1: (**a**) AC sample divided into two pieces during a three-point bending test from the top-view imaging of the fracture area; (**b**) “orange peel” on the bent region of the WQ ample after a three-point bending test; (**c**) linear minor crack coinciding with the bending line on the bent region of the SC sample; (**d**) fracture surface of the sample AC after a three-point bending test. The intergranular fracture mode was noticed; (**e**) electron fractograph of the same area. The intergranular fracture mode accompanied by fine, shallow dimples on the grain faces and brittle intergranular secondary cracks was noted. The samples were further etched by a HF solution for revealing PFZs. It was observed that in the AC sample a semi-continuous network of wide PFZs existed across thickness. Due to the size of the zones they were easily discerned by optical microscopy. In some areas, their width reached 7.8 \(\upmu\)m (Figure 3). PFZs were also detected in the WQ and SC samples, but not at the same degree of continuity, and with a lower width compared to in the AC sample (Figure 4). Figure 3: Continuous network of grain boundary PFZs in the AC sample (white color). Figure 2: (**a**) EBSD grain structure map of the profile. (**b**) Grain structure of the WQ sample away from the bending region (unaffected area).