# Production and Characterization of Cu/CNT Nanocomposites
## 3 Results and Discussion
### Deformation Behavior during Cold Rolling  
The behavior during cold rolling of the nanocomposites was also investigated. Figure 13 reveals the hardness evolution with increasing deformation of Cu and Cu/CNT samples and the IQ maps with the grain boundaries of sintered and cold-rolled samples up to strains of 0.11, 0.69, and 1.61. Figure 11: (**a–c**) Cu and (**d–f**) Cu/CNT (1.0% vol.) samples were analyzed using (**a,b,d,e**) IQ maps with high- (black) and low-angle (red) boundaries and (**c,f**) GND estimated density maps of the area marked in (**a,d**). Figure 12: Contribution of the strengthening mechanisms on the yield strength of the nanocomposites. Figure 13: (**a**) Evolution of Cu and Cu/CNT microhardness with cold-rolling strain (**b–i**) and IQ maps marked with LAGBs (in red) and HAGBs (in black) for (**b–e**) Cu (**f**-i) and Cu/CNT samples, as-sintered and cold rolled to strains of 0.11, 0.69, and 1.61, respectively. As expected, the increased hardness is observed with the increasing of the strain. However, the matrix exhibits higher hardness for high strain values. This means that the strengthening effect of the CNTs no longer plays a role in these strain values. These results can be explained due to (i) the damage in the CNTs during the increase in the strain and/or (ii) the different behavior of the nanocomposites during the cold rolling. Regarding structural damage during the cold rolling, [PERSON] et al. (2018) observed an increase in the I\({}_{\text{D}}\) and I\({}_{\text{G}}\) intensity ratio, which means a growth in the defect in the CNTs during plastic deformation. The grain boundary character and dislocation density were investigated to evaluate the differences between the Cu matrix and the nanocomposites. The IQ maps with the HAGB and LAGB boundaries show no significant differences between the samples. The high density of the LAGB can be associated with regions with a high density of dislocations. Figure 14 shows the evolution of the estimated GND density and the GND maps for the Cu and Cu/CNT as-sintered and cold-rolled samples. These results show that with increasing strain, there is an apparent increase in the dislocation density until stabilization is reached. The Cu and Cu/CNT samples show similar values of this density. For this reason, the discrepancies observed in hardness cannot be associated with the movement and multiplication of dislocations during deformation. The texture evolution of Cu and Cu/CNTs was investigated during the cold rolling. Figure 15 shows the results of the orientation distribution function (ODF) and their development during the deformation of Cu and Cu/CNTs. The ODFs of sintered samples were added for comparison and are present as \(\varepsilon\) = 0.00. In the as-sintered samples, no texture was observed, although slight differences exist between the inherent crystallographic orientations. The Cu sample deformed with \(\varepsilon\) = 0.11 showing a random orientation without any prominent component, while the Cu/CNTs revealed the Goss, Brass, A2, Ab, and B components. For samples cold rolled at a strain of 0.69, the main components are Copper, Goss, and Taylor for the Cu sample, while for Cu/CNTs, the Goss component shows the highest intensity, followed by Copper. However, the matrix texture at a 1.61 strain has Goss and A2 as the main components. Note that Goss is one of the characteristic components of cold rolling in face-centered cubic (FCC) structures. On the other hand, the nanocomposite and the components Copper, Goss, and Brass also show shear components. Based on these results, the matrix and the nanocomposite show a different texture evolution. In nanocomposites, CNTs in the matrix can affect the lattice rotation during deformation, making the active slip systems different from the Cu matrix and affecting texture evolution. Thus, the evolution of hardness during deformation is also affected by this change. However, the texture evolution needs to fully explain the difference in behavior between the nanocomposites and the matrix.