## 3 Results and Discussion  
Figures 2 and 3 illustrate the Optical and EBSD images of as-received AA1100 (wrought alloy) and annealed Al alloy, respectively. As stated, the wrought alloy showed an elongated grain morphology (Figure 2a,b). In contrast to the wrought alloy, annealed specimen's initial microstructure consists of coarse equiaxed grains (Figure 3a,b) with an average size of \(\sim\)40-50 \(\upmu\)m. As can be seen, the fraction of the low-angle grain boundaries (LAGBs) is high for both samples (Figures 2c and 3c ). Optical micrographs of the rolled and the annealed specimens after FSP are shown in Figure 4. The stir zone (SZ) can be distinctly recognised from the base metal in both samples. As stated above, the base metal of rolled specimen consists of elongated grains in the rolling direction; in contrast, the annealed sample's base metal shows equiaxed grains. However, the SZs of both samples consist of extremely fine grains. The subsequent figures will demonstrate more detailed information on microstructural features (Figures 6-8). Monitoring thermal histories during FSP is essential as these affect microstructural developments and mechanical characteristics. Figure 5 shows the temperature profiles during the fourth pass of FSP. The two curves experienced a similar pattern. The annealed Al alloy's maximum temperature (499.7 \({}^{\circ}\)C) is about 2.5% higher than that of the wrought alloy (488.2 \({}^{\circ}\)C). Due to its prior thermo-mechanical treatments, which result in higher dislocation density, the wrought aluminium alloy exhibits superior mechanical strength and thermal resistance. As a result, the material experienced a less intense materials flow during FSP and showed a lower peak temperature compared to the annealed alloy with higher flowability. The wrought and annealed AA1100 alloy microstructure after FSP with Al + Fe\({}_{2}\)O\({}_{3}\) milled powder mixture was studied by optical microscopy, FE-SEM, and EBSD technique. The outcomes of the study by optical microscopy and FE-SEM are shown in Figure 6. As shown in Figure 6a,c, no agglomerated coarse particles, pores, and other defects are found in the SZs of both FSPed specimens. Furthermore, grains were thoroughly refined to equiaxial grains. FE-SEM images (Figure 6b,d) show particles were uniformly distributed  
Figure 3: Optical micrographs (**a**), EBSD maps (**b**), high angle fraction diagrams (**c**), and grain size distribution (**d**) in annealed AA1100 aluminium alloy. Figure 2: Optical micrographs (**a**), EBSD maps (**b**), high angle fraction diagrams (**c**), and grain size distribution (**d**) in as-received (wrought alloy) AA1100 aluminium alloy. in the SZs of the specimens. Thus, it can be confirmed that composite material is formed for both samples. Figure 7 presents XRD patterns of both the rolled and the annealed specimens after FSP with powder addition. Minor phases associated with the crystal structures of Al\({}_{13}\)Fe\({}_{4}\), Al\({}_{2}\)O\({}_{3}\), FeO, and Fe\({}_{3}\)O\({}_{4}\) were also shown, in addition to peaks dominant to Al. The reaction between Al and Fe\({}_{2}\)O\({}_{3}\) occurred during FSP, according to XRD findings. Consequently, in both specimens (rolled and annealed), in situ hybrid nanocomposites were developed. The formation of nanosized reaction products and the associated peak-broadening effect are the causes of low peak-to-background ratios. The iron oxide direction peaks showed that four FSP passes were insufficient to complete the Al-Fe\({}_{2}\)O\({}_{3}\) reaction. The microstructure of the composite sample made from the annealed specimens was examined more closely by transmission electron microscopy (Figure 8). As seen in the picture, different particles are uniformly distributed in the aluminium matrix. Two types of particles can be recognised in the processed composite: elliptical shape and irregular shape. Figure 9 displays the nanometer phases present in the sample made from the annealed specimens, which were taken by scanning transmission electron microscopy.