Electron backscatter diffraction (EBSD) has been attracting enormous interest in the microstructural characterization of metals in recent years. This characterization technique has several advantages over conventional ones, since it allows obtaining a wide range of characterization possibilities in a single method, which is not possible in others. The grain size, crystallographic orientation, texture, and grain boundary character distribution can be obtained by EBSD analysis. Despite the limited resolution of this technique (20–50 nm), EBSD is powerful, even for nanostructured materials. Through this technique, the microstructure can be characterized at different scales and levels with a high number of microstructural characteristics. It is known that the mechanical properties are strongly related to several microstructural aspects such as the size, shape, and distribution of grains, the presence of texture, grain boundaries character, and also the grain boundary plane distribution. In this context, this work aims to describe and discuss the possibilities of microstructural characterization, recent advances, the challenges in sample preparation, and the application of the EBSD in the characterization of metals.

Carbon nanotubes (CNTs)-reinforced metal matrix composites are very attractive advanced nanocomposites due to their potential unusual combination of excellent properties. These nanocomposites can be produced by several techniques, the most reported being powder metallurgy, electrochemical routes, and stir or ultrasonic casting. However, the final mechanical properties are often lower than expected. This can be attributed to a lack of understanding concerning the strengthening mechanisms that act to improve the mechanical properties of the metal matrix via the presence of the CNTs. The dispersion of the CNTs is the main challenge in the production of the nanocomposites, and is independent of the production technique used. This review describes the strengthening mechanism that act in CNT-reinforced metal matrix nanocomposites, such as the load transfer, grain refinement or texture strengthening, second phase, and strain hardening. However, other mechanisms can occur, such as solid solution strengthening, and these depend on the metal matrix used to produce the nanocomposites. Different metallic matrices and different production techniques are described to evaluate their influence on the reinforcement of these nanocomposites.

The development of metal nanocomposites reinforced by carbon nanotubes (CNTs) remains a focus of the scientific community due to the growing need to produce lightweight advanced materials with unique mechanical properties. However, for the successful production of these nanocomposites, there is a need to consolidate knowledge about how reinforcement influences the matrix microstructure and which are the strengthening mechanisms promoting the best properties. In this context, this investigation focuses on the study of the reinforcement effect on the microstructure of an Ni-CNT nanocomposites produced by powder metallurgy. The microstructural evolution was analysed by electron backscattered diffraction (EBSD). The EBSD results revealed that the dispersion/mixing and pressing processes induce plastic deformation in the as-received powders. The dislocation structures produced in those initial steps are partially eliminated in the sintering process due to the activation of recovery and recrystallization mechanisms. However, the presence of CNTs in the matrix has a significant effect on the dislocation annihilation, thus reducing the recovery of the dislocation structures.

The strengthening effect of carbon nanotubes (CNTs) in metal matrix nanocomposites occurs due to several mechanisms that act simultaneously. The possible strengthening mechanisms for metal matrix nanocomposites reinforced with CNTs consist of: (1) load transfer, (2) grain refinement and texture strengthening, (3) second phase strengthening, and (4) strain hardening. The main focus of this work is to identify the strengthening mechanisms that play a role in the case of the Ni-CNT nanocomposite produced by powder metallurgy. For the dispersion and mixing of the metallic powders with CNTs, two different routes were performed by ultrasonication and ball milling. The results indicated that four different strengthening mechanisms are present in the nanocomposites and had a different contribution to the final mechanical properties. The load transfer and the increase in dislocation density seem to strongly affect the properties and microstructure of the nanocomposite. The grain refinement and the presence of second phase particles have a small contribution in the strengthening of this nanocomposite, since the introduction of CNTs in the Ni matrix slightly affects the size and orientation of the grains in the matrix and a few nanometric particles of Ni₃C were identified.

The effect of using different carbon nanotubes (CNTs) on the production of nanocomposites was evaluated in this work. The investigated CNTs were multi-walled carbon nanotubes (MWCNTs) with different morphologies and structures. The main objective was to relate the results reported by numerical simulation with the results obtained experimentally in order to validate these methodologies. A detailed characterization of CNTs was carried out to establish the different main characteristics, such as inner and outer diameters, defects, structure and the number of walls. Metal matrix nanocomposites were produced using the powder metallurgy route. The experimental results show that the morphology and structure of MWCNTs have a significant effect on the dispersion process for nanocomposite production. Straight CNTs with a larger diameter and with few defects allow for the production of nanocomposites with uniform dispersion and strong interface bonding, leading to a higher hardness value. In addition, the CNT introduction into a metal matrix induces a change in the deformation behavior that plays an important role in the strengthening mechanisms. Although some aspects are not considered in the molecular dynamic (MD) simulation, such as the CNT random orientation and CNT agglomeration, some comparative relationships can be performed in order to validate some methodologies. While the structure and morphology of the CNTs have a significant influence on the dispersion process, the influence of the diameter and the functionalization treatment on the properties of the nanocomposites is also identified. The experimental results show that the decrease in the diameter of the CNTs and the use of functionalized CNTs also contribute to the obtention of lower mechanical properties of the nanocomposites, as is pointed out in the results of MD carried out in nanocomposites.

In this research, copper nanocomposites reinforced with carbon nanotubes (CNTs) were produced by ultrasonication and conventional sintering, followed by cold rolling. These nanocomposites may be good candidates due to their excellent properties for components in the electrical, electronics, or aerospace industries with highly demanding requirements. The main objectives of this work were to produce and characterize the Cu/CNT nanocomposites, identify the strengthening mechanisms, and study the deformation behavior of the nanocomposites during cold rolling. The nanocomposites exhibited an improvement in hardness and tensile strength of 17 and 67%, respectively, attesting to the strengthening effect of the reinforced material. The yield strength of the nanocomposites was determined considering different mechanisms: (1) load transfer, (2) grain refinement or texture, (3) dislocation, and (4) Orowan strengthening mechanisms. The microstructural and calculated results show that the mechanism that contributes the most to the increase in the properties of the nanocomposite is the load transfer. The nanocomposites show a different texture evolution of the Cu matrix during cold rolling. This can be due to differences in the active slip planes between the matrix and the nanocomposite, which affects the lattice rotation.