Fabrication and mechanical properties of CNTs/Mg composites prepared by combining friction stir processing and ultrasonic assisted extrusion

A novel process for preparing carbon nanotubes (CNTs) reinforced magnesium nanocomposites were developed, which combined friction stir processing (FSP) and ultrasonic assisted extrusion. A very good dispersion of CNTs in AZ91D alloy could be observed. It was demonstrated that the strength of Mg nanocomposites was remarkably enhanced. This was contributed to dislocation strengthening mechanism and stress transfer mechanism, not concerned with the grain refinement. Moreover, the composites maintained good ductility. The interfaces between CNTs and Mg matrix were well bonded, and the interfacial reaction product formation of Al₂MgC₂ was confirmed. A few edge dislocations were observed at CNTs-matrix boundaries by adding carbon nanotubes.