## 3 Results
### Microstructural Analysis by X-ray Diffraction  
Figure 5a,b depicts the X-ray diffractograms of the pure Al and Fe40 Al intermetallic phases, both in particulate powder aggregation. The X-ray diffractograms of Al exhibit the (111), (200), (220), and (311) diffraction peaks, indicating that the crystal orientations inside the powder particles were randomly distributed. In addition, Figure 5b illustrates the (110) and (200) diffraction peaks related to the intermetallic particulate phase. In this case, the presence of only two diffraction peaks could be due to a preferential crystallographic orientation since the intermetallic particulate powder was produced by a solid-state trituration and pulverization process from ingots with coarse grains. Figures 6-8 depict the X-ray diffraction patterns of the powder mixtures subjected to mechanical milling at various processing times. In accordance with the diffraction patterns, only the diffraction peaks of Al can be predominantly observed. The presence of the diffraction peaks of Fe-Al is negligible; this behavior could be related to the low content of the intermetallic phase and the possible overlap of the peaks of the intermetallic phase with those of aluminum. The highest peaks of Al pertain to the reflections produced by the (111) crystallographic planes. From 0 to 8 h of milling time, the little peak corresponding to the Fe40 Al vanished progressively. This behavior could be related to a combined effect consisting of the disorder or amorphization of the Fe40 Al intermetallic phase during the processing period. Figure 5: X-ray diffraction profiles of (**a**) pure Al and (**b**) Fe40 Al intermetallic phase. Figure 6: X-ray diffraction profiles of the powder mixture of Al-5 Fe40 Al at different processing times. Figure 7: X-ray diffraction profiles of the powder mixture of Al-10 Fe40 Al at different processing times. There is no evidence of the presence of secondary phases that could have been produced by mechanochemical reactions among Al and Fe40 Al. It can be observed that the intensity of the Fe40 Al diffraction peak increased as the content of the intermetallic phase increased in the Al-xFe40 Al powder mixtures. All the diffractograms show that the width of peaks at half its height belonging to the Al exhibited a trend to increase as the milling time elapsed. It is well known that this tendency is related to a decrease in the crystallite size and the generation of lattice strain [20]. Figures 9-11 exhibit the dependence of the crystallite size as a function of the processing time of the powder mixtures composed of Al-5 Fe40 Al, Al-10 Fe40 Al, and Al-15 Fe40 Al, respectively. In this case, the nanometric size of grains was determined from all the X-ray diffraction peaks, and a mean value of the crystallite size was calculated. The crystallite size (nm) was computed by the typical method that employs the Scherrer equation [21] by utilizing the width of the XRD diffraction peak at half its height. It is worth noticing that the trend of the decreasing crystallite size in the ball milling process has typically been reported in the literature where Al composite powders were subjected to this non-equilibrium processing technique [22; 23; 24; 25]. Figure 8: X-ray diffraction profiles of the powder mixture of Al-15 Fe40 Al at different processing times. Figure 10: Variations of the crystallite sizes of Al and Fe40 Al, lattice strain (Al), and dislocation density (Al) as a function of processing time for the Al-10 Fe40 Al powder mixture. Figure 9: Variation of crystallite size of Al and Fe40 Al, lattice strain (Al), and dislocation density (Al) as a function of processing time for Al-5 Fe40 Al powder mixture. Crystalline sizes were utilized to compute dislocation density. In a preliminary approach, dislocation density was considered to be at least one dislocation per crystallite. Thus, in agreement with Equation (1), dislocation density (\(N\)) becomes the inverse square of the crystallite size (\(I_{c}\)) [26].