Study On The Mechanical Properties Of Casting 2024 Al-Matrix Composite With Carbon Nanotube Reinforcement

Aluminum and its alloy are widely used in modern industries such as aviation,aerospace and automobile manufacturing,because of their light weight and high strength,excellent ductility,good conductivity and easy molding,becoming the second largest class of metal materials in industrial use compared to steel with development of low cost reinforcement.Carbon nanotubes(CNTs)have more excellent mechanical properties than traditional reinforcements and have a promising prospect in aluminum matrix composites as new reinforcements.In the experiment,aluminum-matrix composites reinforced with carbon nanotubes and as-cast 2024 aluminum alloy were prepared by liquid casting method.The strengthening effect of CNTs on as cast 2024 aluminum alloy was studied by observing the microstructures and testing the mechanical properties of the alloy.The main conclusions are as follows:It can be found that the metallographic structure of 2024 aluminum alloy has been improved with the addition of CNTs,which can reduce the number of dendrites a obtain certain number of equiaxed grains and refine the grains.When the CNTs content is 1.1 wt%,a better structure is obtained and the performance is improved.The tensile strength and the yield strength of the cast aluminum-matrix composites were 276 MPa and 189 MPa respectively.The results showed that the tensile strength and the yield strength of the aluminum alloy matrix are increased by 38% and 25%,respectively,compared with the as-cast aluminum alloy obtained under the same conditions.On the contrary,the change in elongation after fracture is firstly down to the minimum,and then a slight increase with the CNTs content,and the elongation is reduced to a minimum when the tensile strength and yield strength reach a peak.Grain size in the microstructure becomes bigger and mechanical properties are worse when CNTs content is lower or more than 1.1 wt%.Through the analysis of the fracture surface,it is found that most of the fracture surfaces are tearing edges with some dissociation steps,and there are some dimples in some locations,so it can be concluded that the material fracture is basically brittle fracture.In conclusion,the aluminum-matrix composites attain the best microstructure and maximum mechanical properties when CNTs content is 1.1wt%.