Investigation of Mechanical Properties of Al/CNT Nanocomposites Produced by Powder Metallurgy

Abstract

Demanding requirements in automotive and aerospace applications promote the growing need to obtain materials and advanced technology capable of combining low weight with high mechanical properties. Aluminum matrix nanocomposites could be great candidates to respond to such needs. In this sense, this investigation aims to study the mechanical properties of nanocomposites of aluminum matrices reinforced with carbon nanotubes (CNTs). The nanocomposites were produced by powder metallurgy with 1.00 vol.% of reinforcement and ultrasonication as the dispersion method. Tensile, Vickers microhardness and nanoindentation tests were carried out in different sections. Microstructural characterizations were conducted in scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) to understand and relate to the mechanical properties. An increase in the yield strength of 185% was observed for the nanocomposites, which can be attributed to the load transfer mechanism. However, the CNTs observed at the grain boundaries promote a decrease in the ductility of the nanocomposites. The mechanical behavior of the nanocomposites was further investigated by EBSD observation. The results revealed that the nanocomposites have a less extensive area of plastic deformation than the Al matrix, which is consistent with the tensile results. The presence of reinforcement affects the lattice rotation during the tensile test and the active slip systems, thus affecting their deformation behavior.

Aluminum Nanocomposites Reinforced with Al2O3 Nanoparticles: Synthesis, Structure, and Properties

“…A higher density of dislocations during the production of the nanocomposites is observed due to the presence of the Al2O3 nanoparticles that will significantly affect the mobility of the dislocation. The same result was reported for nanocomposites reinforced with other nanoparticles [11,18]. Different microstructural characteristics are evident between the matrix and the nanocomposites processed under the same conditions.…”

“…What was observed in this work is that with the applied dispersion technique, there is a limit on the volume fraction that allows a uniform dispersion to be followed. The same was observed for other metallic matrix nanocomposites reinforced with other nanoparticles [11,18]. This is because the more significant the fraction volume, the closer the nanoparticles will be, making their dispersion difficult (Figures 2 and 3).…”

“…The as-received materials were characterized using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) using FEI QUANTA 400 FEG equipment (Hillsboro, OR, USA) with an EDS from Oxford Instrument (Abingdon, Oxfordshire, UK) and an EBSD detector, the TSL-EDAX EBSD Unit (EDAX Inc. (Ametek), Mahwah, NJ, USA). Aluminum particles have already been intensively characterized in other works [18,19], where it has been observed that each particle has more than one grain and is characterized by surface deformation due to the manufacturing process they were subjected to.…”

“…This work selected a one-step dispersion and mixing process using ultrasonication. Various dispersion/mixing media (ethanol, isopropanol, and water) and various ultrasonication frequencies (12.0, 15.0, and 20.4 kHz) are based on previous work using other nanoparticles [11,18,19]. Table 1 shows the conditions tested in this work.…”

“…Cold compaction was carried out at 300 MPa and sintering at 640 • C for 90 min. These processing conditions were selected based on the best conditions obtained for Al/SiC and Al/CNT nanocomposites [11,18]. Archimedes' principle was employed to measure the density of the sintered specimens, providing insights into the compaction and porosity levels.…”