Carbon nanotubes-reinforced aluminum alloy functionally graded materials fabricated by powder extrusion process

Tubular shape aluminum (Al) 6063/Al-3 vol% carbon nanotubes (CNT)/Al3003 functionally graded materials (FGMs) were fabricated by hot extrusion process. FGMs is consisted by Al6063 which exhibits high strength and hardness, Al-3 vol% CNT which exhibit superior mechanical and thermal properties and Al3003 which has high ductility. The Al-3 vol%CNT powder, which is middle layer of FGMs, was used to increase contact surface area with other materials resulting in improved interface properties. The composite powder was observed using a field-emission scanning electron microscope (FE-SEM). To analyze the microstructures, FGMs were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy(TEM). Al-3 vol%CNT was recrystallized by friction with bulk. In this zone, the Vickers hardness value was almost 120 HV, which is twice of the values of Al6063and Al3003. Although the FGMs has high strength of 142 MPa, it also realizes high elongation of 22%. We considered some possible strengthening mechanisms, including CNT strengthening, grain refinement, precipitation hardening, and oxide dispersion strengthening.