## 3 Results
### Electron Backscatter Diffraction  
EBSD scans were performed for texture characterization across the thickness of the profiles, for the examination of the grain boundaries characteristics on the surface and the mid-thickness regions and the correlation of misorientation with precipitation behavior. Scans were performed on transverse sections, as these are considered more representative for texture observation of extruded products. The SC sample was selected for the specific examination, but the same results regarding texture applied for the AC and WQ samples as well. The sample in terms of texture characterization can be divided into two distinct zones, i.e., the surface zones (inner and outer) with an approximate thickness of 200 \(\upmu\)m and a mid-thickness (Figure 5). The subsurface zones did not exhibit strong, preferred texture; however, the (001) orientations had a higher density (4.5 times random in the inverse pole texture plot). On the other hand, the mid-thickness region was strongly textured, exhibiting a single (001) fiber texture which was typical for extruded products (17.6 times random). This preferred texture was responsible for the poor response of the profiles to Barker's electrolytic etch. The surface zones were mostly characterized by HAGBs, a low percentage of LAGBs, and a minor percentage of SGBs (81/15/4 fraction, Figure 6a). The precipitation behavior was observed in different grain boundaries of the same area. After electrolytic polishing the HAGBs were easily discerned, while the LAGBs were not so easily detected and only at high magnifications greater than 10k X were they fully traceable. In area of interest (AOI) 1, it was observed that extensive grain boundary precipitation occurred on the HAGBs with 20 nm precipitates in length and limited precipitation on the LAGB, while on the triple boundary a coarse precipitate of a 100 nm length was observed (Figure 6c). However, this behavior was not identical on the other boundaries. In AOI 2, grain boundary precipitation was observed on an LAGB with characteristics similar to those of the precipitation of HAGBs of AOI 1. The precipitates were almost globular with a 15 nm mean diameter, and they were met at a random spacing between two successive precipitates ranging  
Figure 4: PFZs formation in the WQ sample (**a**) and in the SC sample (**b**). between 20 and 500 nm (Figure 6d). In AOI 3, it is shown that precipitation occurred at both HAGBs and LAGBs but the size of the precipitates was coarser on the HAGBs, taking into consideration both length and thickness reaching a length of 90 nm and a thickness of 8 nm in the HAGB (Figure 7). The precipitates of the LAGBs boundaries reached a maximum length of 75 nm, and the spacing between them was higher than that of the HAGBs. Similar behaviors were observed on the other areas of interest of the subsurface-recrystallized regions of the profile. On the other hand, mid-thickness region was characterized by the presence of HAGBs, LAGBs, and SGBs at a fraction of 51/32/17 approximately (Figure 8a). The mean grain size was 52 \(\upmu\)m. It is worth noting that the relatively high amount of SGBs was present in a region, which was considered fully recrystallized judged also from the size and the morphology of equiaxed grains. Regarding the grain boundaries characteristics, the results differed a lot in the mid-thickness region. Considerable amounts of LAGBs (14.7%) and SGBs (4.5%) were detected as can be observed in Figure 8. In AOI 4, it is presented that the precipitates were rounded to elliptical with a mean diameter of 40 nm on the HAGBs and globular with a 30 nm diameter in LAGBs and minor precipitation of few nanometers scale was also detectable on SGBs. The inter-spacing was comparable for LAGBs and HAGBs boundaries. In AOI 5, precipitation on the HAGBs was semi-continuous; however, the precipitates did not exhibit considerable thickness. On the LAGBs, the sizes of the precipitates were finer, not exceeding 25 nm, and in no case were they continuous as in HAGBs.