Influence of aging treatment on the microstructure and mechanical properties of CNTs/7075 Al composites

Abstract The carbon nanotubes reinforced 7075 Al composites (CNTs/7075 Al) were fabricated by powder metallurgy. The precipitation hardening behavior of CNTs/7075 Al composites with 1 wt% CNTs during aging treatment was revealed by microstructure characterization and mechanical properties. It was found that the introduction of CNTs accelerated the precipitation hardening of 7075 Al alloy due to the dislocations generated between the CNTs and the Al matrix. The localization of dislocation distribution led to the formation of enrichment and poor areas of MgZn2, which were called precipitates-rich region and precipitates-poor region, respectively. After aging treatment, the CNTs/7075 Al composites had the peak hardness of 151.4 HV, and the peak-aging time decreased from 14 h to 10 h compared to 7075 Al alloy. Moreover, the average diameter of MgZn2 in composites after aging treatment was reduced to 25 nm, and the spatial distance between MgZn2 was significantly reduced. As a result, the CNTs/7075 Al composites exhibited a tensile strength of 558.3 MPa and an elongation of 7.7%. These experimental phenomena provide a new understanding of the effects of CNTs on precipitation hardening behavior of Al alloys.