# Deformation Behaviour of Cold-Rolled Ni/CNT Nanocomposites
## 4 Conclusions  
This study evaluated the cold-rolling of Ni/CNT nanocomposites under different strains (between 0.11 and 0.92) to investigate the effect of the reinforcement on deformation behaviour. The Ni matrix was also produced and subjected to cold-rolling and analysed for comparison purposes. The samples were initially produced by powder metallurgy. The microstructural characterization of cold-rolled specimens revealed that the nanocomposites exhibited a different microstructural evolution from the Ni matrix during the cold-rolling. This was attributed to the presence of CNTs that influenced the density of dislocations and initial crystallographic orientation of the matrix during production. The nanocomposites revealed a higher density of GNDs than the Ni matrix after the sintering process due to the clusters of the CNTs, mainly at grain boundaries, that hindered the recovery process during sintering, and that did not occur in the same proportion in both samples. Consequently, the nanocomposites showed a different crystallographic orientation than the Ni matrix after sintering, which affected the texture evolution when deformation was applied. In both samples, when low strains were applied (\(\varepsilon\) = 0.11 and 0.22), a decrease in the density of dislocations was observed in GNDs' density maps due to their rearrangement  
Figure 9: IPF maps of (**a,c,e,g**) and (**b,d,f,h**) Kernel misorientation maps of Ni and Ni/CNT samples deformed with strains of (**a,b,e,f**) 0.36, and (**c,d,g,h**) 0.69. (scale bar = 15 \(\upmu\)m). and annihilation during the application of these strains. This effect is attributed to the Bauschinger effect. With these lower strains, there were some differences between Ni and nanocomposite microstructures since the starting point (the sintering samples) had significant remaining deformation in the microstructures. For higher strains (\(\varepsilon=0.36\) and 0.69), the dislocation density gradually increased until it reached a critical point, beyond which this density remained roughly stable. The sample's microstructures also became similar. The hardness of the matrix increased with increasing strain due to the strain hardening. However, for nanocomposites, the observed behaviour was different. For strains of 0.11 and 0.22, a softening (from 180 HV0.01 to 132 HV 0.01) of the sample was observed due to the significant dislocation density decrease--Bauschinger effect--as already mentioned. For higher strains (\(\varepsilon=0.36\) to 0.92), the overall hardness increased for both samples. However, the nanocomposites showed values lower than for the matrix under the same conditions (305 and 263 HV 0.01 for the Ni and Ni/CNT with strains of 0.92, for example), which was not foreseen. These unpredicted hardness values can be justified by the different texture evolution of Ni and Ni/CNTs during the plastic deformation because the samples exhibited different initial crystalline orientations that affected the texture evolution during the cold-rolling. The texture evolution was investigated using both ODFs and IPs' images. For the matrix, typical rolling components, such as Copper and Brass, were observed, resultant, and expected given the used deformation method. However, applying strains of 0.92 induced the formation of a shear texture (revealed by the components bb, A1, and C) that can be explained due to an inhomogeneous rolling in the sheet thickness. For the nanocomposites, the main rolling components observed were Copper and Taylor for the strain of 0.36, and the shear texture components were observed sooner, with strains from 0.69 up. This difference between Ni and nanocomposite texture evolution can be justified by the different initial crystalline orientations and microstructures that affect the texture evolution during cold-rolling.