| Guide rail is one of the popular applications of copper matrix composites,which not only has the requirements of high conductivity and high strength,but also has the requirements of wear resistance,arc ablation resistance and corrosion resistance.Copper-based composites mostly adopt alloying,solution strengthening and deformation strengthening to improve mechanical properties and microstructure.However,In recent years,rail materials need higher strength,conductivity,wear resistance and arc ablation resistance to adapt to more severe working conditions(such as large working current and high-speed friction.).In this paper,according to the existing demand,the gradient composite method of surface particle reinforced copper matrix composite and core high purity copper material is proposed,the preparation method of gradient copper matrix composite is optimized,and its microstructure and properties are studied.In this paper,two preparation methods of Cu-0.7Cr-0.12Zr-0.1Ag-0.12Nb-1SiC-0.5Gr(graphite)-2W/Cu gradient composites are emphatically introduced,and the best preparation method is selected.according to the Ohm's law and Hooke's Law basic theory,the value range of the cross-sectional area ratio between the surface layer and the core layer is calculated,and the microstructure,deformation characteristics of gradient copper matrix composites under different cumulative deformation are analyzed and compared At the same time,the gradient copper matrix composite material is compared with the existing guide rail material Cu-0.7Cr-0.12Zr alloy,and the variation laws of friction coefficient,wear rate and friction morphology under different loads or different friction velocity are analyzed and compared The change laws of ablation rate and ablation morphology under different ablation times or different ablation current densities are also analyzed and compared.According to the above experimental scheme and test method,the experimental results are as follows:(1)The preparation method of gradient copper matrix composites was optimized.According to the comparative analysis of microstructure,mechanical properties and electrical conductivity of gradient copper matrix composites prepared by the two methods,the method with no agglomeration of functional phase,uniform composition,dense matrix and stable mechanical properties and electrical conductivity was optimized.The specific preparation method is as follows:isostatic pressing,billet making,vacuum consumable melting,infiltration at 1000? for 1 h,solution treatment at 950? for 2 h,rotary forging,cold deformation and aging treatment at 450? for 4 h.(2)According to the Ohm's law and Hooke's Law basic theory,the interval of the cross-sectional area ratio between the surface layer and the core of the gradient copper-based composite is calculated and designed,and the change laws of microstructure,electrical conductivity and mechanical properties of the gradient copper-based composite under different cumulative deformation are analyzed and compared.The results show that with the increase of accumulated deformation,the orientation consistency of grains in the sample increases,and the dislocation density near the precipitated phase and the granular phase increases;The electrical conductivity and tensile strength of the samples are slightly improved.The sample with the best performance is gradient copper matrix composite with cross-sectional area ratio of surface layer to core of 1:3.8,with conductivity of 90.3%IACS and tensile strength of 468MPa.(3)In friction and wear experiments,when the load is 5N-20N,the friction coefficient decreases with the increase of load,and the average friction coefficient and wear rate of gradient copper-based composites decrease by 0.08 and 2.7×10-6 cm3·N-1·m-1,respectively.When the friction velocity is 0.0448 m/s-0.1792 m/s,the friction coefficient and wear rate decrease first and then become constant with the increase of friction velocity.Compared with the rail materials in service,the friction coefficient and wear rate of gradient copper matrix composites decrease by 0.08 and 1.97×10-6 cm3·N-1·m-1 on average.(4)When the number of arc ablation is 30?150,the ablation rate increases gradually at first and then decreases slightly with the increase of ablation times,and the ablation rate of gradient copper-based composite material decreases by 67.3 ?g/C on average compared with that of active rail material.When the ablation current density is between 100 A/mm2 and 500 A/mm2,the ablation rate increases gradually at first and then decreases slightly with the increase of current density,and the ablation rate of gradient copper matrix composites is reduced by 73.1 ?g/C on average compared with the current rail materials. |
PDF Full Text Request