Study On Preparation Of Carbon Nanotubes Reinforced Aluminum Matrix Composites By High Energy Ball Milling And Its Properties

Carbon nanotube/aluminum composite material has a lot of advantages, such as low density, high specific strength, good processing performance and high conductivity. Thus it is a composite full of broad application prospects. But the research results have not reached the target, and the relevant theoretical research was also insufficient. Therefore, it possesses important theoretical and practical value to carry out the study of carbon nanotube/aluminum composite.In this paper, pure aluminum and multi-walled carbon nanotubes (MWCNTs) were used to prepare pure Al/MWCNTs-A1composite powders by mechanical alloying. To reduce the impurity and increase the dispersibility of MWCNTs, strong alkalis treating, strong acids treating, strong acid and high temperature oxidation treating were used to preprocess carbon nanotubes. After cold pressing, sintering and hot extrusion, these composite powders were processed into composite bars, The study contents and results are as follows:The microstructure and mechanical properties evolution of the MWCNTs/Al composite powders with different milling time in the mechanical alloying process were systematically studied by the characterization of the microstructures, grain size, micro-strain, microhardness and other parameters. The results showed:(1) the composites became more and more dense, but the grain size decreased gradually, and the micro-strain gradually and the microhardness gradually increased with increasing ball milling time; The Al4C3was discovered in the composite powders prepared by a long time ball milling;(2) The mechanical properties of the composite were tested by the common mechanical testing machine, and its fracture morphology was observed by scanning electron microscopy (SEM). The results showed:the method of ball milling+cold pressing+sintering+hot extrusion process can successfully prepared high-strength materials; the strength of the composite prepared by12h ball milling was253MPa, owing to the excellent interfacial bonding between MWCNTs and aluminum.The sintering temperature can also enhance the interfacial bonding especially the grain bonding. The tensile strength of composite sample by650℃sintered was167MPa, which is improved23%compared with the sample by500℃sintered; Either a too long or a too short sintering time will reduce the composite performance. The diffusion and reaction of composite powders, the crystallization and recrystallization of composite in the preparation process was critical factor related to the properties of composite.