Fabrication and characterization of carbon nanotube nanocomposites into 2024-T3 Al substrates via friction stir welding process

Abstract

Carbon nanotube (CNT)-aluminum (Al) nanocomposites were prepared using friction stir welding (FSW) processing, and then the mechanical properties of these nanostructured materials were determined using the universal MTS machine. The fabrication of the CNT-metal composite consisted of the following steps: (a) homogenizing the CNTs and Al powder at three different ratios: 0/100, 25/75, and 50/50, (b) compacting the mixtures into grooves that were initially machined into the substrate (2024-T3) for the three cases, (c) incorporating CNTs in a substrate by the FSW process, and (d) validating the dispersion of the CNTs into the Al substrates after the characterization steps. Scanning electron microscopy (SEM) analysis and other physical characterization tests (e.g., mechanical, metallography, and fracture surfaces) were conducted on the prepared substrates. Test results showed that CNTs were dispersed and aligned uniquely in the different locations of the metal structures depending on the FSW zones: advancing, retreating, transverse, and stir zone regions. The mechanical properties of each zone were also compared to the distribution of CNTs. The advancing side had the highest amount of CNTs mixed into the aluminum substrate while retaining the yield strength (YS); however, the elongation was reduced. The retreating side had little to no CNTs distributed into the substrate and the mechanical properties were not significantly affected. The stir zone YS had little influence of the CNTs at the lower CNT/Al powder ratio (25/50), but a significant effect was noticed at the higher ratio of 50/50. The elongation to failure was significantly affected for both cases. The transverse zone YS and elongation to failure was significantly reduced by the powder mixtures. These results may open up new possibilities in the aircraft and other manufacturing industries for future development in the field.