Mechanical And Physical Properties Of Aluminum-Based Composite Materials Reinforced With Carbon Nanotubes

Aluminum-based composites have excellent properties such as low density,high specific strength,and good electrical and thermal conductivity,making them widely used in transportation,military defense,and power electronics.Carbon nanotubes(CNTs)are considered to be the ideal reinforcing agent for developing structure-functional integrated aluminum-based composites due to their outstanding mechanical and physical properties.Powder metallurgy is one of the main methods for preparing aluminum-based composites,which is easy to achieve autonomous design of composite materials.Combining hot-pressing sintering with plastic deformation can further optimize the microstructure and comprehensive properties.This study starts with the influence of vacuum hot-pressing sintering temperature on the microstructure and physical properties of CNT/Al composites,and selects the optimal sintering temperature.Then,the relationship between CNT content and microstructure and physical properties of CNT/Al composites is studied.Finally,based on the advantage of hotpressing sintering,CNT/Al gradient composites with CNT content gradient change are autonomously designed,and encapsulated rolling and medium-temperature heat treatment are carried out to study the comprehensive properties of CNT/Al gradient composites.The study found that:Sintering temperature has a significant effect on the density of CNT/Al composites,and high-density samples also show high hardness,strength,and excellent conductivity.The experimental material obtained better density at 570°C,and its hardness was higher than that of other composite materials sintered at other temperatures by more than 20 HV,and the tensile strength increased by more than 70 MPa while maintaining good elongation rate.There are also significant differences in the microstructure of aluminum-based composites with different CNT contents.The variation of CNT content has little effect on the density,but the addition of CNT causes a significant change in the hardness of CNT/Al composites.When the CNT content is 1.6wt%,the average hardness of aluminum-based composites exceeds 230 HV,which is nearly 90 HV higher than that of aluminum-based composites with 0.8wt% CNT content.The 1.6wt% CNT/Al composite material has the highest tensile strength,but the 0.8wt% CNT/Al composite material has the largest elongation rate.Hot-pressing sintering can achieve flexible design of arbitrary component gradients and realize rapid preparation of gradient materials.The hardness values along the thick component gradient change direction also show a gradient distribution,and the high CNT content layer has a higher hardness value.Designing a high CNT content surface layer can improve the wear resistance of the composite material.The conductivity of the finished product is related to the total CNT content,and when the total CNT content is the same,reducing the surface CNT content helps to improve the conductivity.Through rolling and heat treatment,the internal pores of CNT/Al gradient composites can be reduced,and the density can be improved.After rolling processing,the hardness of the composite material increased significantly,but the interlayer hardness difference decreased.The conductivity of the composite material decreased significantly after rolling,but the wear resistance increased.After heat treatment,CNT/Al gradient composites have good electrical conductivity and wear resistance.The wear mechanism of CNT/Al gradient composites is closely related to the CNT content.When the surface CNT content is low,adhesion wear is dominant.With the increase of CNT content,adhesive wear turns to plowing wear.