Influence of Ni-CNTs additions on the microstructure and mechanical properties of extruded Mg-9Al alloy

Ni-coated carbon nanotubes (Ni-CNTs) reinforced Mg nanocomposites were successfully fabricated via one step ultrasound-assisted extrusion technique. The Ni-CNTs were well dispersed in both the low and high mass fraction of Mg matrices, although occasional small aggregates were observed when mass fraction of Ni-CNTs exceeded 1.5%. There are no significant variations in grain size as the introduction of Ni-CNTs. The mechanical properties of the Ni-CNTs/Mg nanocomposites with different weight percentages of Ni-CNTs (0, 0.5, 1.0, 1.5, 2.0, 3.0 wt%) were discussed. The results showed that yield strength (0.2% YS), ultimate tensile strength (UTS) and hardness of Mg nanocomposites were higher than the as-extruded AZ91D alloy. The strength and ductility could be improved by Ni-CNTs addition, however, it was decreased beyond a threshold value 1.0 wt%. The hardness was increased with the Ni-CNTs content. The fracture of composites was mainly caused by the pull-out and failure of Ni-CNTs. A good bonding interface without defects was observed.