Fabrication of Fullerene-Reinforced Aluminum Matrix Nanocomposites

Abstract

Fullerene-reinforced Al matrix nanocomposites were fabricated by high-energy mechanical milling followed by consolidation through hot extrusion or high-pressure torsion (HPT). The results indicate that a relatively homogeneous microstructure consisting of elongated, micrometer-sized Al grains is formed in the hot-extruded specimens. However, the microstructure is not uniform along the radius of the HPT disks, which includes coarse grains near the center of the disk and ultrafine grains in the middle and along the edge of the specimen. Microstructural evaluations of the HPT disks indicate that Al grain refinement occurs due to the addition of fullerene, as grain size is reduced to 60 nm from 118 nm. The formation of the harmful aluminum carbide phase is not detected during the fabrication of Al/C-60 nanocomposites. The hardness, yield stress, and ultimate tensile strength of the Al-2 vol.% C-60 nanocomposites are about 27-160% higher than those of the monolithic Al samples, revealing the effective strengthening of fullerene particles in Al matrix. Moreover, mechanical properties of the Al/fullerene nanocomposites are significantly enhanced (59-272%) by utilizing HPT in comparison to hot-extruded specimens due to their much finer Al grain structure. The reduction in the number and the size of the dimples, as well as the formation of smooth regions on the tensile fracture surface of Al/C-60, results in their overall lower ductility compared to monolithic Al.