Research On Preparation Process Of CNTs/Mg By Friction Stirring-Liquid-Solid Extrusion

Carbon nanotube reinforced magnesium matrix(CNTs / Mg)composites have potential applications in the fields of aerospace,automotive,electronics and automation because of their excellent properties.However,the carbon nanotubes are easy to aggregate in the magnesium matrix because of the strong van der Waals forces between the carbon nanotubes(CNTs)and their large specific surface area and high aspect ratio.Therefore,how to achieve uniform dispersion of CNTs in the metal matrix and improve the mechanical properties of the prepared composite material are a key technology that needs to be solved in the preparation of CNTs/Mg composites.In order to obtain good dispersion of carbon nanotubes,a new technology of CNTs / Mg composites was proposed by changing the way of adding carbon nanotubes.Magnesium plate electrophoresis deposited carbon nanotubes was prepared as CNTs / Mg composite material by friction stir-liquid-solid extrusion process.The process overcomes the defects that the carbon nanotubes prepared in the prior art are easily reunited,floated and the equipment is complex.At the same time,the process will effectively improve the dispersion effect of the carbon nanotubes in the magnesium matrix.The main study of this paper was as follows:According to the characteristics of the process,the electrophoretic deposition experiment device,the friction stir processing experiment device and the extrusion die experimental device design were completed.The uniformity of electrodeposited carbon nanotubes on the surface of magnesium alloy sheets was studied.The influence of electrophoresis time and deposition voltage on the uniformity of the distribution of carbon nanotubes on the surface of magnesium alloy plates was analyzed under different electrophoresis concentrations.Quantitative characterization of magnesium alloy plate deposited carbon nanotube quality and electrophoretic deposition time relationship under the best electrophoretic deposition process parameters.The process properties of CNTs/Mg composite friction stir processing were studied.The reasonable process parameters for the good quality of CNTs / Mg prepared by friction stir processing were determined.Based on the reasonable process parameters,CNTs were successfully added into the magnesium alloy and the remarkable dispersion effect was obtained.The average particle size of CNTs reached 0.65 ?m,which is respectively 1/166 and 1/152 of the average particle size of CNTs in the CNTs / Mg composites prepared by pore-filling method.The liquid-solid extrusion process of CNTs/Mg composites was studied.Under the light microscope,the distribution of particle diameter of CNTs with different mass fractions in the matrix was statistically analyzed and analyzed by Image J software.The compressive properties of the composites were tested.The CNTs / Mg composites with compressive strength up to 520 MPa were obtained,which was 23.81% higher than the matrix.The fracture morphology of the matrix and the composite under scanning electron microscope(SEM)was analyzed.It was found that the rupture direction of the matrix ruptured at 45 ° to the compression axis and the fracture was straight,while the composite material along the fracture direction was "jagged" fracture.The preparation of CNTs / Mg composite by friction stir-liquid-solid extrusion in this paper will provide an effective way to improve the dispersion of CNTs in metal matrix.