| With the rapid development of aerospace,automotive,electronics,military and other fields,B4CP/A1 composites with structural and functional integration are attracting more and more attention from researchers.The traditional high content micron size B4CP play an excellent role in improving the hardness and strength of the B4CP/A1 composites.But the existence of a large amount of hard phase has lowed the processing properties of the composites.As the advanced structural material production and application,only has the stable machinability could give full play its value.High-performance nanoparticles can be achieved by adding a small amount of particles significantly improve the mechanical properties of materials.However,the large specific surface area and strong interfacial interaction of nanoparticles are easy to agglomerate,and it is difficult to achieve uniform distribution in the metal matrix,which result in the nano-particles can not give full play to their excellent enhancement effect and the preparation process complicated.Especially with the increase of nanoparticle content,the agglomeration of nano-particles will reduce the mechanical properties of the materials.Therefore,improving the dispersion of nano-particles in the matrix has become an urgent problem to be solved at home and abroad.However,there are few researches on nano-B4Cp/A1 composites at home and abroad.Therefore,how to prepare nano-B4Cp uniformly distributed in the matrix by high-efficient preparation technology,so that nano-B4Cp will give full play to enhance the advantages.This will result in great practical significance to further improve the comprehensive properties of aluminum matrix composites.In this paper,a new method for the preparation of high strength n-B4Cp/2009A1 composites was proposed,which was difficult to be effectively dispersed in the high content nano-B4Cp/A1 composites.2,4,6vol.%nano-B4Cp/2009A1 composites were successfully prepared by powder metallurgy and hot extrusion.The best preparation method of n-B4Cp/2009A1 composites was optimized by exploring the preparation process of 6vol.%n-B4Cp/2009A1 composites.The effects of preparation process and heat treatment and reinforcement content on the microstructure and mechanical properties of the composites were studied by means of OM,XRD,SEM and TEM.The main research results show that:(1)According to a reasonable process system,the composites with different volume fraction of nano-B4Cp/2009Al composites were successfully prepared by three-dimensional high-performance mixer,multi-stage vacuum hot pressing and hot extrusion.The nano-B4Cp were dispersed uniformly in the prepared composites,and no obvious holes defects were found.After the optimum heat treatment process,4vol.%nano-B4Cp/2009Al composite have the best comprehensive mechanical properties,and the tensile strength,yield strength and elongation reached 51 0MPa,375MPa and 4.6%,respectively.(2)The preparation process of three-dimensional high-performance mixing was simple and efficient.When the ratio of ball charge mass is 5:1,and mixing time is 30h,the uniform distribution of nano-B4Cp in the matrix can be realized.During the dry mixing,nano-B4Cp,which tends to disperse stably and mechanically embedded in the matrix gradually under the ball-material-can collide with each other and mutual friction between the large particles and finally achieve a uniform distribution in A1 matrix.(3)The results show that,the optimum parameters of vacuum hot pressing and hot extrusion of nano B4Cp/2009Al composites are that:vacuum hot pressing at 600? for 80min,hot extruding at 480?,extrusion ratio is 5:1,and extrusion speed is 5mm/s.The prepared bars have a smooth surface without defects,and the density of the composites is more than 99.74%.(4)The optimum heat treatment parameters of nano-B4Cp/2009Al composites are as follows:solution at 495? for 1h,artificial aging at 175? for 14h.The time to obtain the peak hardness of composites was 2h ahead of the matrix.This is mainly due to the the synergistic effect of a small amount of nanoparticles agglomeration and small nanoparticles to increase the dislocation density in the matrix and promote the rapid nucleation of the precipitated phase,which plays the role of accelerated aging. |
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