Preparation Of Carbon Nanotube Reinforced Magnesium Alloy Composite Materials

CNTs/Al-5wt%Mg composite powder with different contents of CNTs were fabricated by high energy ball milling, and then powder metallurgy technique were used to consolidate the high energy ball milled composite powders.The purification of CNTs, the effect of milling process parameters on performance of CNTs/Al-5wt%Mg composite powder, the effect of pressing and sintering process and the contents of CNTs on CNTs/Al-5wt%Mg composites were systemically investigated and analyzed. By using SEM, XRD, laser particle size detector, tensile test and hardness test techniques, the microstructure, the mechanical properties and the processing parameters of the composite powders and composites were examined and optimized. In addition, the strengthening mechanism of CNTs/Al-5wt%Mg composites was related.The results showed that CNTs could effectively disperse in the matrix uniformly by high energy ball milling. The CNTs employed in this study played a certain role of the grinding aiddition, which also could prevent agglomeration of particles. When the content of CNTs equal to3wt%, the average grain size of the composite powder was fined to a minimum of64.3nm. The best milling parameters had been obtained as follows:ball-to-powder weight ratio is25:1, rotation speed is800/1000, milling time is90min, and the process control agent is2wt%.The CNTs/Al-5wt%Mg composites prepared by hot pressing sintering process and cold pressing-sintering process respectively.The results showed that the composites prepared by hot pressing sintering process more excellent than cold pressing-sintering process.The best sintering process as follows:sintering temperature560℃,holding time60min.The content of CNTs significantly influences the mechanical properties of the composite material. The hardness and tensile strength of the CNTs/Al-5wt%Mg composite increase firstly and then reduce with the increase of CNTs content. The hardness and tensile strength reached the maximum value,90.5HB and175.62Mpa respectively, when CNTs content equal to2wt%. It increased36.5%in hardness and 42.39%in tensile strength compared to the maximum when contents of CNTs equal to2wt%.The fracture surfaces of the composite involved in bridging and pulling out/breakage of CNTs. No entangled CNTs were obtained on the fracture surface. It was suggesting that the CNTs were dispersed completely and had a strong interfacial bonding with the Al-5wt%Mg matrix. However second phase precipitate Al3Mg2were obtained in the matrix, which play the role of dispersion strengthened. Finally the strengthening mechanisms of CNTs reinforced Al-5wt%Mg matrix composites were discussed. In this case, Orowan looping; load transfer and fine grain strengthening were proved to be the main strengthening mechanisms of the Al-5wt%Mg composites.