## 1 Introduction  
The automotive and aerospace industries increasingly demand lightweight materials with high strength and stiffness to achieve the established requirements to reduce vehicle weight, increase fuel efficiency and lower emissions. Aluminum matrix nanocomposites could be an attractive option to meet the requirements demanded by these industries [1, 2]. Carbon nanotubes, mainly due to their mechanical properties, could be the ideal reinforcement material for these nanocomposites. In this sense, aluminum nanocomposites reinforced by carbon nanotubes (Al/CNT) may have the advantage of being potential candidates for lightweight components with high mechanical strength even when only a small amount of CNTs are added [3, 4, 5, 6, 7, 8, 9, 10, 11]. However, some challenges in producing these nanocomposites must be overcome to obtain properties close to potential ones. Due to the formation of CNT agglomerates and damage to its structure during the processing of the nanocomposite, the reinforcement potential is compromised, resulting in lower mechanical properties than expected. Previous work has shown that the effectiveness of the reinforcement effect increases with a better reinforcement dispersion, with better results observed in nanocomposites with 1.00 vol.% CNTs dispersed by ultrasonication [12, 13, 14]. The mechanical properties of nanocomposites must therefore be investigated to assess the dispersion of CNTs, production conditions, the effect of the CNTs fraction and the interfacial bonding of Al/CNTs to evaluate the effect of reinforcement on the final component. For instance, an increase in CNT fraction can promote an increase in the elastic modulus of the composite from 70 GPa to about 110 GPa for CNT addition from 1 to 5 vol.% [3]. However, in the case of poor dispersion of the CNTs, an increase in the fraction can also decrease the elastic modulus due to the formation of large CNT clusters. Due to CNT agglomeration and a reduced load transfer, the stiffness increase rate decreases as CNT content increases [3; 4; 5; 6; 7; 8]. In this context, some published works investigate the mechanical properties of Al/CNTs nanocomposites produced by different processes and with different fractions of CNTs [3; 4; 5; 6; 7; 8; 9; 10; 11]. [PERSON] et al. [5] investigated the conditions of the dispersion method in the mechanical properties of the Al/CNTs nanocomposites produced by powder metallurgy. The nanocomposites were produced with 3.00 vol.% of CNTs using high-energy ball milling. The nanocomposites revealed higher tensile strength and Young modulus than the Al matrix did. These results were attributed to the uniform CNTs distribution obtained for 2 h of ball-milling samples. [PERSON] et al. [6] produced Al/CNTs with different CNTs fractions by ball milling and hot pressing. The yield strength of the nanocomposites increases until 1 wt.% CNTs than the Al matrix, and then it was observed a decrease. The decrease observed for higher amounts of CNTs than 1 wt.% can be explained due to the formation of CNTs clusters. [PERSON] et al. [7] studied the mechanical properties of Al/CNTs nanocomposites produced by friction stir welding. The authors observed an enhancement of yield and tensile strength of \(\approx\)105 and \(\approx\)52%, respectively, while the elongation went from \(\approx\)39.5 to \(\approx\)24.0% when added 3.20 vol.% CNTs. The authors also observed the fracture surface, seeing the presence of dimples in both Al and the nanocomposite, showing that both had a typical ductile fracture. [PERSON] et al. [11] observed the same type of fracture surface for the nanocomposites of Al/CNTs produced by powder metallurgy with two different types of CNTs. The CNTs used presented higher and lower aspect ratios. The authors observed a maximum increase in tensile and yield strength of \(\approx\)50% and \(\approx\)48%, respectively, for concentrations of 0.5 wt.% lower aspect ratio CNTs than aluminum matrix samples. [PERSON] et al.