Fabrication of 2014 aluminum matrix composites reinforced with untreated and carboxyl-functionalized carbon nanotubes

Abstract

2014 aluminum matrix composites reinforced with untreated (P-CNTs) and carboxyl-functionalized carbon nanotubes (C-CNTs) were successfully fabricated by the combination of sintering and hot extrusion. It is revealed that the C-CNTs are easier to disperse compared to the P-CNTs. Interfacial analysis indicated that a thin layer of aluminum carbide (Al4C3) exists at the interface between the matrix and the P-CNTs. However, no obvious transition layers of Al4C3 were observed at the interface of C-CNTs and 2014Al matrix in composites. Also, no preferred interfacial crystallographic orientation relationship between the C-CNTs and aluminum matrix was observed. Furthermore, C-CNTs have a larger effective interfacial contact with aluminum matrix compared to the untreated CNTs, due to large amount of –COOH group and defects on the surface of the C-CNTs interacting with Al by strong chemical and physical interactions. These aspects in turn affect the mechanical properties of the composites. The ultimate tensile strength of the composites were raised from 530 to 600 and 630 MPa with 0.5 wt.% of P-CNTs and C-CNTs, respectively. It reveals that the C-CNTs are more effective in strengthening the aluminum matrix than the P-CNTs.