## 5 Conclusions  
There was no evidence of second-phase development throughout the milling process, as confirmed by the X-ray diffraction evaluation. This could be because the milling process was developed under low energy conditions, which means that there was not enough provision of mechanical energy to the mixture of powders to induce mechanochemical reactions. Scanning electron microscopy results, on the other hand, demonstrated the presence of Cr\({}_{2}\)Al precipitates in the Al matrix of the consolidated Al5 Cr specimen. Furthermore, electron microscopy examination of the Al-7.5 Cr consolidated specimen revealed the formation of a supersaturated (Cr) phase with the Pearson symbol cl2 and belonging to the space group Im3m, with a prototype phase of the kind W that corresponds to the binary alloy phase diagram of the system Al-Cr.  
In addition, X-ray diffraction spectra denoted that the crystallite size experienced a continuous decrement as the milling time had elapsed, even after the sintering process, the crystallite size exhibited the same trend to diminish. This behavior could be explained by the pinning effect imposed by Al-Cr precipitates on grain boundary movement, which was uniformly precipitated in Al based matrix during sintering process.  
The lattice strain determined from the Williamson-Hall method exhibited a continuous increase as the ball milling process had advanced; however, after the sintering treatment was applied, the lattice strain had a decrement. This behavior is related to the removal of crystalline defects, in particular, the large ones. This elimination of punctual defects originated from thermal energy provided during the sintering process.  
The density of dislocations was computed using the size of nanosized grains as a rough reference. The dislocation density ascended as the milling process progressed, according to this estimate even after the sintering the multiplication of dislocations prevailed following the same tendency.  
Results derived from a theoretical model of mechanical properties showed values of hardness and yield strength of 58.6 Hv and 75.9 MPa for Al5 Cr specimens. In a similar way, estimated values of hardness and yield strength resulted in values equal to 42.2 Hv and 52.4 MPa for the Al7.5 Cr specimen.  
Conceptualization, J.P.-C., C.D.A.-G., N.B.G.-G. and I.D.P.G.; Methodology, R.A.R.-D.; Formal analysis, R.A.R.-D., J.P.-C. and J.L.R.B.; Investigation, R.A.R.-D.; Resources, C.D.A.-G., N.B.G.-G. and I.D.P.G.; Writing--original draft, R.A.R.-D.; Writing--review & editing, J.P.-C. and J.L.R.B.; Visualization, J.L.R.B., C.D.A.-G., N.B.G.-G. and I.D.P.G.; Supervision, R.A.R.-D.; Project administration, R.A.R.-D.; Funding acquisition, J.P.-C., J.L.R.B., C.D.A.-G., N.B.G.-G. and I.D.P.G. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Figure 20: (**a**) Hardness and (**b**) yield strength dependence with volume fraction of Al matrix in Al7.5 Cr Matrix Composite.  
**Institutional Review Board Statement:** The study did not require ethical approval.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data of the results can be consulted with the corresponding author.  
**Conflicts of Interest:** The authors declare no conflict of interest.