Technical Study On The CNTs Reinforced Magnesium Matrix Composite By Powder Metallurgy

The significance to study on the CNTs reinforced magnesium matrix composites were reviewed at first in this paper, and then the common reinforcements and matrix of magnesium matrix composites were introduced. The structure and properties of carbon nano-tubes were introduced, and the advantage of carbon nano-tubes as reinforcement was also discussed. The characteristics and applications of CNTs reinforced magnesium matrix composite were primarily summarized, and the problems of fabricating CNTs/Mg composite and the developing current of CNTs/magnesium composite was reviewed.Carbon nano-tubes and magnesium powder were mixed by3-D high-efficiency mixer and the CNTs reinforced magnesium matrix composite was fabricated by vacuum hot-pressing sintering. In order to improve the wetting property of carbon nano-tubes with magnesium, a nickel film was coated on carbon nano-tubes by surface modification and electroless plating. The mechanical and physical properties of CNTs/magnesium composite were tested and the microstructure, fracture pattern and the distribution of CNTs in matrix was observed by optical microscope, SEM. The obtained conclusion as follows:(1)Using dispersant in alcohol solution can ameliorate the agglomeration of CNTs obviously by ultrasonic dispersion method, density activated sites were formed on the surface of carbon nanotubes after surface modification. When Theplating temperature keep at20℃or so and the PH value maintains about8.2, more uniform Ni coated layer will be obtained. The layer will become smoother, more continuous and more condense after heat treatment at410℃and preservation for2h to theCNTs with Ni coated layers. The thickness of layer is about12-20nm.(2)The long CNTs were broken by3-D high-efficiency mixer, and the CNTs can be uniform distributed in the matrix. Experiment proved that when the ratio is5:1with mixing time8h, CNTs are the best uniform distribution in the matrix.(3) Pure Mg,0.5vol.%CNTs/Mg and1.0vol.%CNTs/Mg were endured hot-pressing sintering in550℃and600℃for30min. The results show that Interface hardness of1.Ovol.%CNTs/Mg is higher, and the crystalline grain is finer.(4) Through Observation of fracture appearance of pure Mg and CNTS/Mg and analyses of mechanical property, the strengthening mechanisms are smaller grain size mechanisms and enhanced dislocation density...