Study On Electrical And Mechanical Properties Of Particle And Whisker Hybrid Reinforced Copper Matrix Composites

Due to excellent electrical conductivity,high strength and good wear resistance,copper matrix composites have wide applications in the rail transportation,high voltage electrical appliances,and weaponry.As compared to a single phase reinforced copper matrix composites,the particle and whisker hybrid reinforced copper matrix composites have a larger room for reinforcement phase design and regulation,which can be expected to achieve a significant improvement on the comprehensive performance.Subsequently,it is necessary to explore the intrinsic relationship between the characteristic parameters of the reinforcement phase and the properties,and the research is of vital theoretical significance and engineering value for the design and manufacture of copper matrix composites.In this thesis,a single phase(TiB2,Al2O3,SiCw)and hybrid phases(TiB2+SiCw,Al2O3+SiCw)reinforced copper matrix composites were studied,the microstructure and interface of the composites were characterized by scanning electron microscope(SEM)and transmission electron microscope(TEM),and the electrical conductivity,the mechanical properties,current carrying tribological behavior and arc erosion resistance were tested as well.The effect of the reinforcement phase characteristic parameters on the electrical conductivity and mechanical properties of copper matrix composites was systematically studied,and the correlation of the reinforcement phase characteristic parameters and the electrical conductivity and mechanical properties of copper matrix composites was established.Based on the above study,the current carrying tribological behavior and arc erosion resistance of hybrid reinforced copper matrix composites were investigated.The main research contents and conclusions are as follows.(1)The analytical model for the electrical conductivity of single particle reinforced copper matrix composites was constructed via comprehensive consideration on the main factors that affect the electrical conductivity,such as particle content,size,proportion,and the interface relationship between particle and Cu matrix.Based on topological structure of the composite together with the principle of equivalent circuit,a new analytical electrical conductivity model of whisker reinforced copper matrix composites including whisker orientation and whisker structure parameters is proposed,in which the continuity and correlation between whisker arrangement and electron transmission in electron transmission channel are considered.Subsequently,the electrical conductivity analytical model of particle and whisker hybrid reinforced copper matrix composites is constructed utilizing the topology transformation and equivalent circuit technology along with the electrical conductivity analytical model of particle and whisker reinforced copper matrix composites.(2)The mechanical tests display that the particle/whisker size,distribution and interfacial bonding state affect the mechanical properties of particle and whisker hybrid reinforced copper matrix composites.The strength and elongation of the composites can be improved simultaneously by introducing an appropriate proportion of whisker.Compared with the Al2O3/Cu composite,the yield strength and elongation of(SiCw+Al2O3)/Cu composite are increased by 6.0%and 15.6%,respectively.(SiCw+Al2O3)/Cu composite has the tensile strength of 153 MPa at 600℃,exhibiting excellent high-temperature property.(3)The hybrid reinforced copper matrix composites present lower friction coefficient and wear rate in comparison with the single particle or whisker reinforced copper matrix composites.Particle and whisker can give full play to their advantages in the studied copper matrix composites,in which the particle reinforcement can improve the strength and regulate whisker spatial distribution,whereas the whisker bear most of the average stress,thus increasing the strength.The whiskers tilt toward the sliding direction or are parallel to the worn surface,which increase the friction contact area and bear more loads.Therefore,the synergistic effect of the particle and whisker enhances the tribological properties of copper matrix composites.(4)Compared with the TiB2/Cu and Al2O3/Cu composites,the arc erosion resistance is significantly improved for the(SiCw+TiB2)/Cu and(SiCw+Al2O3)/Cu composites,in which the hybrid of the particle and whisker can give full play to space occupying advantage.Hence,they can synergistically strengthen the copper matrix,disperse arc,increase the viscosity of the molten pool,reduce flow and splashing of the molten pool,thereby causing the formation of uniform erosion surface and avoiding serious pit erosion.