Plastic deformation mechanism of MWCNTs/AZ91D nanocomposites with high ductility at room temperature

Abstract

1.0 wt% MWCNTs/AZ91D magnesium matrix nanocomposites were prepared by metal mold gravity casting process assisted by high-intensity ultrasonic dispersion, and the ductility was further improved by T4 solid solution treatment. The tensile test results at room temperature revealed that the tensile strength and elongation of 1.0 wt% MWCNTs/AZ91D nanocomposites after T4 solid solution treatment reached up to 281.7 MPa and 15.4%, respectively. The ductility of magnesium matrix nanocomposites was significantly improved by the addition of Multiwalled carbon nanotubes (MWCNTs) and T4 solid solution treatment. SEM and TEM were used to observe the microstructure of 1.0 wt% MWCNTs/AZ91D-T4 nanocomposites after the tensile plastic deformation at room temperature. A considerable number of slip bands and twins were found in the microstructure of the nanocomposites. High strain zones were formed around MWCNTs during the tensile process at room temperature. A large number of dislocations and stacking faults were generated in the high strain zones, which could be used as the origin of slip bands and twins, so MWCNTs can promote slip and twining. MWCNTs can further activate non-basal slip and cross slip, and improve the ductility of 1.0 wt% MWCNTs/AZ91D-T4 nanocomposites.