CNTs And In-situ Al₄C₃ Hybrid Reinforced Aluminum Matrix Composites Preparation, Microstructure And Mechanical Properties

Carbon nanotubes reinforced aluminium matrix composites?CNTs?have broad application prospects in aerospace,transportation,electrical engineering and other fields,and have become a research hotspot in the field of metal matrix composites in recent years.Relevant research has made remarkable progress.However,the properties of the composites have not reached people's expectations.In this paper,carbon nanotubes?CNTs?and aluminium carbide?Al₄C₃?hybrid reinforced aluminium matrix composites were used to study the effects of reinforcement phase content and heat treatment temperature on the structure and mechanical properties of the composites in order to improve the mechanical properties of the composites.Firstly,the effects of CNTs and Al₄C₃ content on the structure and mechanical properties of composites were studied.Aluminum-based composite powders with different contents of CNTs and Al₄C₃ were prepared by high-energy ball milling.The composite powders were then prepared into bulk composites by spark plasma sintering?SPS?sintering and hot rolling.X-ray diffraction,Raman spectroscopy,field emission scanning electron microscopy,microhardness tester,transmission electron microscopy and electronic universal testing machine were used to analyze and test the microstructures and mechanical properties of composite powders and composites.The results show that CNTs are uniformly dispersed in short-time ball milling?6h?composite powders and their structures are relatively complete.In long-time ball milling?24h?composite powders,most of CNTs react with aluminium powders to form Al₄C₃ in situ.Changing the amount of CNTs added in different ball milling stages can change the contents of CNTs and Al₄C₃ in composites,thus affecting the structure and properties of composites.?The composite with 0.5%CNTs and 1%Al₄C₃ has the highest tensile strength?297MPa?,which is obviously improved compared with the composite reinforced by a single reinforcement.This is mainly due to the synergistic strengthening of CNTs and Al₄C₃ in hybrid reinforced aluminium matrix composites.CNTs mainly play the role of load transfer strengthening,while in situ Al₄C₃ mainly plays the role of dispersion strengthening.Then,the hybrid reinforced aluminum matrix composites with the best mechanical properties were heat treated to study the effect of heat treatment temperature on the structure and mechanical properties of the composites.The results show that the tensile strength of the composites increases first and then decreases with the increase of heat treatment temperature,and the highest tensile strength of 317 MPa is obtained for the composites heat treated at590?.With the increase of heat treatment temperature,the chemical reaction between CNTs and Al matrix in composites results in in-situ formation of an appropriate amount of Al₄C₃ at the interface,which is helpful to improve the shear strength of the interface between CNTs and Al matrix,thus facilitating the load transfer strengthening of CNTs.When the heat treatment temperature is too high?e.g.610 C?,The growth of Al4C3 in composites is obvious.The size of Al₄C₃ has exceeded 500 nm.The growth of Al₄C₃ is not only harmful to the interface bonding of the composites,but also reduces the Oroven strengthening efficiency of the composites due to the increase of the size,thus reducing the mechanical properties of the composites.