Study On Fabrication, Interface Of MWCNT/Mg-6Zn Magnesium Matrix Composites

Carbon nanotubes(CNTs)were pre-dispersed by ball-milling. CNTs/Mg-6Zn composite was fabricated by mechanical stirring accompanied with high intensity ultrasonic process. It was observed by field emission scanning electron microscopy that CNTs were distributed homogeneously on the grain boundary together with the second phase. OM, SEM and TEM were used to study the microstructure of the composites. Universal tensile test machine was used to investigate the mechanical properties of the as-cast and as-extrued composite.The study of dispersion process show that mechanical ball-milling could break up the entanglement of original carbon nanotubes and improve the dispersion of them. Ball-milling speed and time can influence the dispersion of carbon nanotubes simultaneous. CNTs/Mg-6Zn composite was fabricated by mechanical stirring accompany with high intensity ultrasonic process successfully. When the rotation speed is 400 rpm, it can reach the optimum distribution effect after 4 hours’ ball-milling.In as-cast CNTs/Mg-6Zn composite materials, carbon nanotubes within the substrate distribution is relatively uniform, no obvious reunion was found. Tissue analysis show that the joining of carbon nanotubes can cause grain refinement which make the matrix alloy refine grain size drop from 200 μm to 90 μm. the as-cast composite material’s ultimate tensile strength and yield strength was enhanced significantly or so the addition of CNTs makes the yield strength and tensile strength of the matrix alloy improved obviously because of the joining of carbon nanotubes.Significant grain refinement of the matrix alloy was caused by hot extrusion deformation. But the grain size distribution is very uneven. CNTs band formed in the process of hot extrusion. Small grain size in the band show that CNTs can have a strong influence on recrystallization rate by retarding the migration of recrystallization grain boundaries so that to improves the strength of the composite material, makes the elongation increased significantly.It can be seen from the fracture that carbon nanotubes is very complete which means that ball-mill do no harm to carbon nanotubes. In addition, reunion of carbon nanotubes was not found on the fracture, which shows that carbon nanotubes are uniformly distributed in the matrix. The study show that a part of the carbon nanotubes still rooted in the matrix, while the rest of it was pulled outside of the matrix. The matrix was reinforced in this way.