## 3 Results and Discussion
### Mechanical Properties of the Nanocomposites and Aluminum Matrix
Figure 12 shows the Kernel average misorientation (KAM) and the tensile Taylor factor maps for Al and Al/CNT samples for the region of 2.0 mm from the fracture surface of tensile specimens. The KAM maps are one of the most powerful tools to study the deformation shown in a microstructure and are often used for this purpose [26; 27; 28; 29; 30; 31; 32; 33; 34]. These maps show, in both samples, that the highest deformation (represented by red associated with higher misorientation values) is presented around the pores and CNTs agglomerates (in the nanocomposite case) of the samples. This result is because these areas are brittle points of the samples, being zones without any material, having lower strength and being easier to deform during tensile testing. Figure 11: Hardness distribution maps (HV 0.01) of (**a**) Al and (**d**) Al/CNT of fractured tensile test specimens close to the fracture and average geometrically necessary dislocations (GNDs) density maps of (**b**,**c**) Al and (**e**,**f**) Al/CNT samples. As mentioned previously, the cracks are also more prone to initiate in these areas due to their vulnerability. Based on these images, it is possible to conclude that the Al samples reveal higher misorientation close to the surface fracture than the nanocomposites. This agrees with the hardness, dislocation density, and tensile curve results. The Taylor maps show grains with a higher factor than the nanocomposites, revealing their different behavior to deformation. Another point in common between the two samples is that it is nitid that some of the grains are significantly more deformed than the others, which is represented by green within the grains. One of the possible causes of these effects is the different crystallographic orientations of these grains, being that softer grains, orientated  
Figure 12: (**a,b**) 2 nd neighbor kernel average misorientation (KAM) maps, (**c,d**) tensile Taylor factor maps and (**e,f**) Taylor factor distribution of (**a,c,e**) Al and (**b,d,f**) Al/CNT tensile test specimen 2.0 mm from the fracture surface. to directions favorable to the dislocation formation and propagation, will be the first to deform when a load is applied. Whether these grains are surrounded by other grains in a favorable crystallographic orientation (softer grains) or not (harder grains), the deformation can be easier or more difficult. When harder ones surround a soft grain, it is more difficult for the deformation to continue, and more load is needed for the process to occur [35]. In addition, what should be mentioned is that the analysis of Figure 12 allows us to verify some differences in the grain size, being visible smaller grains around the larger ones. The presence of these small grains could be formed during the sintering, where some recrystallization of the aluminum occurs [14] but also with the presence of CNTs agglomerates, in the case of nanocomposites, where the grain growth is hindered. Either way, the presence of these smaller grains can affect the mechanical properties since materials with smaller grains show a more fragile deformation behavior. In comparison, samples with larger grains have higher elongation but lower tensile strength. In that sense, bimodal microstructure, as in this case, can be a good compromise as it presents a behavior between soft and brittle [36]. Analyzing the area at 10 mm from the fracture, Vickers hardness maps, GND distribution maps and tensile Taylor maps can be seen in Figure 6:0 With the observation of these results, the increase in hardness for the nanocomposites in this region cannot be attributed to the increase in dislocation density or to the grain size of the samples (7.0 for Al matrix and 6.4 for nanocomposites). In fact, the dislocation density is similar for the two samples. The hardness in this region can be explained by the presence of CNTs or even other microstructural changes. In the Taylor factor maps, it is visible that significant differences can be observed, which is an indication of the different tensile behavior of these materials.