# Deformation Behaviour of Cold-Rolled Ni/CNT Nanocomposites
## 2 Materials and Methods  
The nanocomposites were produced by powder metallurgy. The nickel powders used were from the supplier Goodfellow (Goodfellow Cambridge Ltd., Huntingdon, UK), whose morphology and microstructure were thoroughly studied by advanced characterization techniques in other works [21; 22; 23; 24]. The carbon nanotubes used as reinforcing material were multi-walled and non-functionalized, supplied by Fibermax (Fibermax Ltd., London, UK) and have also been characterized in detail in previous work [25].  
The metallic powders and carbon nanotubes (1.00 %vol.) were mixed. The dispersion and mixture of powders and CNTs were performed simultaneously in a single step, consisting of 15 min of ultrasonication with isopropanol; followed by cold pressing; and, finally, sintered in a vacuum. This process has already been described elsewhere [3; 23; 24; 25; 26; 27], as well as its effect on the carbon nanotubes [28] and metallic powders [22]. Unreinforced samples (matrix only) were produced and deformed under the same conditions for comparison purposes.  
To study the deformation behaviour, nanocomposites, and the matrix, produced under the same conditions, were submitted to cold-rolling, with different thickness reduction percentages (from 10 to 60%), as schematized in Figure 1a. The cold-rolling process was performed at room temperature (\(\approx\)25 \({}^{\circ}\)C) with 10 rpm, and each thickness reduction was gradually achieved in a maximum of 5 passes. The microstructure of rolling samples was analysed in the cross-section, parallel to the rolling direction, as represented by the letter A in Figure 1b. The thickness reduction can be associated with the respective logarithmic strain (\(\epsilon\)) by Equation (1) [29]:  
\[\epsilon=\ln\left(\frac{h_{0}}{h}\right) \tag{1}\]  
where the \(h_{0}\) represents the initial thickness of the sample and \(h\) its thickness after rolling.  
All the samples were microstructurally characterized using scanning electron microscopy (SEM) with high-resolution equipment FEI QUANTA 400 FEG SEM (Thermo Fisher Scientific, Waltham, MA, USA) and a TSL-EDAX EBSD detector (Ametek Inc., Devon-Ber Wyn, PA, USA). While acquiring the raw EBSD data, small step size was used to obtain highly detailed information. In this case, the minimum step size used was 0.03 \(\upmu\)m. The analysis of the EBSD data was performed using two software with different functionalities: the TSL OIM Analysis 5.2 (Ametek Inc., Devon-Ber Wyn, PA, USA) and the ATEX version 3.28 (University of Lorraine, Metz, France) [30]. The first one was used for most maps, for example, inverse pole figure (IPF) and Kernel average misorientation (KAM) maps, and to distinguish between different boundary characters. The conditions applied in each map, as well as the clean-up routine applied to avoid misleading results of this software, are described in previous works [3,22]. The ATEX software allowed the elaboration of estimated maps of average geometrically necessary dislocations (GNDs), grain disorientation maps, as well as pole figures (PF), and orientation distribution functions (ODF).  
The mechanical properties of the deformed samples (matrix and nanocomposite submitted to each applied strain) were evaluated by microhardness tests. The condition used was a 98 mN load during the normalized time (15 s). The calculated average values refer to about 15 indentations per sample, measured on cross-section A, illustrated in Figure 1b. The microhardness tests were performed using Duramin-1 equipment (Struers, Ballerup, Denmark).