CNTs/AZ91D magnesium matrix nanocomposites were prepared by high-energy ultrasonic dispersion technology and metal mold gravity casting process.The solid solution T4 heat treatment and the aging T6 heat treatment were carried out for the composites prepared.The tensile strength and elongation of 1.0% CNTs/AZ91D composites with T4 treatment can reach 285 MPa and 17.3%

which are improved by 45% and 322%

respectively

compared with 196 MPa and 4.1% of the as-cast ones.After the aging T6 heat treatment

the tensile strength of the composites is further increased to 296 MPa

and the yield strength is increased significantly to 155 MPa

while the elongation is declined to 5.5%

showing obvious aging hardening effetcs.The microstructure of 1.0%CNTs/AZ91D composites was observed by metallographic microscope

scanning electron microscope and transmission electron microscope.The results reveal that carbon nanotubes can refine grain

promote slip and twinning and transfer load

so that the comprehensive mechanical properties of CNTs/AZ91 Dcomposites can be improved obviously.