Origin of insignificant strengthening effect of CNTs in T6-treated CNT/6061Al composites

Abstract

Carbon nanotube (CNT)-reinforced 6061Al (CNT/6061Al) composites were fabricated via powder metallurgy combined with friction stir processing (FSP). CNTs were dispersed after FSP and accelerated the precipitation process of the CNT/6061Al composites. However, the strengthening effect of CNTs on the T6-treated materials was insignificant, while the composites under the FSP and solution treatment conditions exhibited increased strength compared to the matrix. Precipitate-free zones (PFZs) were detected around CNTs in the T6-treated CNT/6061Al composites, and a model was proposed to describe the effect of PFZs on strength. The calculations indicated that the strength of PFZs was similar to that of the T6-treated 6061Al. As a result, the strengthening effect of CNTs on the T6-treated CNT/6061Al composites was insignificant.