## 2 Materials and Methods  
In the present research, the production of nanocomposite from the Fe2O3-Al system will be reported using FSP technology. The matrix alloy selected was a 5 mm thick commercial 1050 aluminium alloy plate. Table 1 indicates the typical chemical composition of the Al sheet. Both rolled and annealed plates were utilised for the FSP in order to study the effect of the base metal microstructure on the microstructure of the friction stir processed composite (Figure 1). Annealing was performed at 673 K for 3.5 h. The Al sheet was cut into pieces that measured 210 mm \(\times\) 70 mm \(\times\) 5 mm to prepare the workpieces, and a groove that was 1.4 mm wide and 3.5 mm deep was machined into the middle of the piece. The milled powder combination is next inserted into the groove that has been cut out. The stoichiometric compositions were used to prepare the powder mixture of Fe\({}_{2}\)O\({}_{3}\) (?98% purity, the particle size of 1 \(\upmu\)m) and Al (?99% purity, the average size of \(\sim\)100 \(\upmu\)m). The mixed powder was mechanically milled for two hours using a high-energy planetary mill under the argon atmosphere. The purpose of ball milling of the powder mixture before the FSP was to enhance the reaction rate during the FSP. FSP is performed rapidly after embedding the milled product in the created groove to avoid powder oxidation. The tracks filled with powder were FSPed, employing a vertical milling machine. The rotational tool speed and the traverse velocity were 1400 rpm and about 40 mm/min, respectively. Four FSP passes were carried out with 100% overlap. X-ray diffractometry (XRD), using a Philips X'Pert Pro unit, was used to determine the crystal structures of the top surfaces of the fabricated hybrid nanocomposites. The unit was equipped with monochromatic Cu-K\({}_{\alpha}\) radiation and \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Al** & **Zn** & **Cr** & **Mg** & **Mn** & **Cu** & **Fe** & **Si** \\ \hline Balance & 0.0097 & 0.0041 & 0.0017 & 0.0061 & 0.0123 & 0.272 & 0.206 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Nominal chemical composition of BM, 1050 aluminium alloy sheet (wt.%). Figure 1: (**a**) Specimen preparation for the FSP, (**b**) schematic of FSP accomplishment and (**c**) the prepared nanocomposite from the top view. operated at a voltage and current of 40 kV and 30 mA, respectively. Employing a step size of 0.02\({}^{\circ}\) and time per step of 5 s, high-precision X-ray diffraction patterns were obtained. Microstructural characterisation of the fabricated hybrid nanocomposites was carried out using optical (OM, Olympus GX51) and Jeol-JSM7600F field emission scanning electron microscopy (FESEM). The latter was operated at 20 kV and linked to an energy-dispersive spectrometer device (Bruker silicon drift detector) for point chemical analyses and X-ray mapping. Cross sections of the fabricated hybrid nanocomposites were prepared and polished according to the standard metallographic preparation. In addition, both secondary and backscattered electron imaging were obtained. Moreover, the electron backscattered diffraction (EBSD) examination was conducted using a plan-view cross-section of the fabricated hybrid nanocomposites. In this regard, the samples were automatically ground and polished, followed by colloidal silica polishing for 45 min to achieve high-quality surfaces for EBSD studies. HKL technology's Channel V software was used to process the data after it was created using the EBSD (OXFORD Instrument-X Max, Abingdon, UK) method, which was utilised to obtain electron channelling patterns using an ultra-sensitive CCD camera. Each EBSD map had a scanning step of 0.2 \(\upmu\)m and an average confidential index that varied from 0.38 to 0.57. Using the Channel V software, the volume fraction of LAGBs and HAGs was calculated from the EBSD maps. The data analysis did not include below 2\({}^{\circ}\) misorientation at the grain boundary. High-angle boundaries (HABs) were defined using a 15\({}^{\circ}\) boundary misorientation.