# Deformation Behaviour of Cold-Rolled Ni/CNT Nanocomposites
## 1 Introduction  
The development of nanocomposites comes from the growing need to obtain advanced materials capable of combining low weight with high mechanical properties. In this sense, metal matrix nanocomposites are especially attractive for producing structural components in the mobility industry [1]. The range of reinforcement materials is vast, with carbon nanotubes (CNTs) standing out due to their unique properties when integrated into metal matrices. Furthermore, the heterointerfaces of nanocomposites can improve the properties of some components of the energy industry due to the possibility of increasing the ionic and/or electronic conductivity, electrocatalytic activity, and stability of electrolytes andelectrodes. These heterointerfaces are characterized normally by large variations in local composition, lattice strain, electronic structure, and other properties [2]. The promising mechanical properties of these nanocomposites depend on the contribution of several strengthening mechanisms, which act simultaneously. If they do not occur properly, they can compromise the strengthening effect, as analysed in previous work [3]. Since the final components' obtention is often dependent on some processing to obtain their final geometry, the knowledge of the effect of CNTs on the deformation behaviour of nanocomposites is essential for their implementation in the industry. In that sense, understanding how CNTs can influence the deformation behaviour of the nanocomposites and their interaction with the matrix during the process represents an added value in optimizing their properties and processing. This deformation alters their microstructure and, consequently, their mechanical properties, requiring detailed studies. For the heterointerface, the dislocation network along the interface also plays a role in the transport pathways in the ionic conductivity [2]. During the plastic deformation process, the grain morphology change is accompanied by grain rotation, so the structure accommodates the imposed deformation. The movement and multiplication of dislocations allow the plastic deformation process to continue until fracture. These aspects can increase domains, dislocation cells, and the appearance of one or more preferential crystallographic orientations. This texture is more evident with the greater degree of deformation of the material. There are two main plastic deformation mechanisms in metallic materials: dislocation slip or twinning. However, dislocation movement is the dominant plastic deformation process, most often the only one, and mainly responsible for grain rotation, usually occurring in the crystal's more compact planes and directions. When a polycrystalline material is plastically deformed, each grain tends to deform differently from its neighbours, as they have different orientations. This would lead to the formation of voids or overlaps between grains, which does not occur. When deforming polycrystalline metals, continuity is observed between the grains. However, for this continuity to occur, the grains deform in the direction of the applied strain. In turn, this deformation is guaranteed by geometric necessary dislocations (GNDs), whose movement and multiplication are due to local internal stresses and can accommodate the applied strains [4; 5]. All this contributes to a change in grain morphology during plastic deformation. The crystallographic orientations of individual grains in a polycrystalline material are modified during plastic deformation due to grain rotation. They can result in preferred orientation or textures, which become stronger with increasing deformation [6]. Texture formation can be influenced by several factors, such as (1) the chemical composition, namely the presence of alloying elements, which consequently can influence the atomic structure and energy faults; (2) the type of applied deformation (its temperature and type of strain path imposed); and (3) the initial crystallographic orientation of the grains, i.e., before deformation [6].