## 3 Results and Discussion
### Macrostructure and Microstructure Investigation
Figure 11 displays histograms of the average grain size distribution formed at various feeding rates of 1, 2, 3 and 4 mm/min and 400 rpm constant  
Figure 9: Optical microstructures: (**a**) AA7075-T6 rod BM, (**b**) at higher magnification of (**a**), (**c**) the AA2024 plate, (**d**) the interfacial region between AA7075 deposited layers and the AA2024 substrate of the specimen processed at 400 rpm and 3 mm/min, and (**e**) at higher magnification of (**d**). rotation speed. The grain size slightly increases with increasing deposition feed rates as a result of increase in the processing temperature. It attains the average values of 1.75 \(\pm\) 0.35, 2.25 \(\pm\) 0.30, 3.25 \(\pm\) 0.25 and 3.75 \(\pm\) 0.45 \(\upmu\)m at 1, 2, 3 and 4 mm/min feeding rates, respectively, compared to the average grain size value of 52 \(\pm\) 13 \(\upmu\)m for the AA7075 rod BM material in the deposition direction (Figure 9a,b). Figure 9c represents the microstructure of the AA2024 substrate material. Its grains are elongated in the rolling direction and have an average grain size of 33 \(\pm\) 6.2 \(\upmu\)m. Another microstructure feature was noted: that the microstructures of AA7075-T6 BM (Figure 9a,b) and the deposited layers (Figure 9d,e) contain black dots, elongated aggregates, and irregular aggregates. These features were found in the deposited layers as dispersed fragments. Previous studies [59; 60; 61] indicated that the AA7075 (Al-Zn-Mg-Cu) aluminum alloy contained different types of intermetallic materials in both the T-6 and the friction stir welded or processed conditions. Thus, it can be inferred that the deposition feed rate and the rotation speed are crucial processing parameters that exert a noticeable effect on the presence and distribution of intermetallics in the microstructure of the DPs. Figure 10: OM-imegs of the obtained microstrcures of the AA7075 DPs processed at different deposition feed rates of (**a**) 1, (**b**) 2, (**c**) 3, and (**d**) 4 mm/min and at 400 rpm. XRD was used as a tool to examine the presence phases for both the AA7075-T6 rod and the additive friction stir deposited materials at 400 rpm and feed rates of 1, 2, 3 and 4 mm/min, as represented in Figure 12. It can be seen that all the XRD patterns revealed typical peaks for the aluminum phase at 2-0 of 38.3, 44.5, 65.0, 78.2, 82.3 and 98.7\({}^{\circ}\) as the majority phase. The presence of only small peaks indicates the detection of MgZn\({}_{2}\) as a minor phase. This intermetallic appears at 2-0 of 19.7, 20.9, 40.7, 42.5, 51.8, 69.2, and 72.7\({}^{\circ}\). In addition, the possibility of detection of an Al\({}_{7}\)Cu\({}_{2}\)Fe phase is not confirmed with the XRD technique used as it appears overlapped with the aluminum peaks, as shown in Figure 12. This phenomenon was observed by [PERSON] and [PERSON] [61] who reported the same phenomenon. Therefore, an advanced SEM-EDS analysis system was used to confirm the possible intermetallics in the AA7075-T6 rod BM and the built material at 400 rpm and a 3 mm/min feed rate, as shown in Figure 13. It can be remarked that the EDS investigation showed three different intermetallics in the aluminum matrix: MgZn\({}_{2}\) (Spot 1) AlCuMg, (Spot 2) and Al\({}_{7}\)Cu\({}_{2}\)Fe (Spot 3), as shown in Figure 13a,b. The EDS-spots 1, 2 and 3 are represented in Figure 13c-e, respectively. These intermetallics differ in their morphology and phase composition. The intermetallic morphologies in the aluminum matrix alloy are governed by numerous parameters, like chemical composition, type of alloying elements, processing technique and heat treatment program [62; 63]. The noted morphologies of the detected intermetallics are elongated intermetallic, almost-spherical and irregular for MgZn\({}_{2}\), AlCuMg and Al\({}_{7}\)Cu\({}_{2}\)Fe, respectively, as seen in Figure 13. These results are consistent with those mentioned by [PERSON] et al. [41] and [PERSON] et al. [64] for joining AA7075 and AA2024 via FSW.