| Cu-graphite composite materials are widely used in aerospace,rail transit,electronic appliances and other fields due to their excellent electrical conductivity,thermal conductivity,and wear resistance.However,the physical properties of graphite and copper differences,poor wettability,which makes the prepared composite dispersion is poor,the weak interfacial bonding,seriously affecting the properties of the composite.There are more or less defects in the existing preparation process.Therefore,a new preparation process is needed to solve the problem of graphite distribution and interface bonding,thereby improving the comprehensive performance of the composite material.In this paper,Cu-graphite composites were prepared by accumulative roll bonding(ARB)and intermediate annealing.The effects of different intermediate annealing processes on the microstructure and properties of the composites were studied,and the optimal intermediate annealing process was determined.On this basis,the number of rolling cycles was further improved,and the changes of composite material interface bonding,graphite distribution,hardness,electrical conductivity,friction coefficient,wear amount,texture,etc.,with the number of cycles were analyzed.The main results are as follows:(1)There are oxide inclusions in the composite material prepared by intermediate annealing in a non-protective atmosphere.With the decrease of intermediate annealing times,graphite agglomerates,grain size decreases,relative density decreases,conductivity decreases,hardness increases,friction coefficient increases and the wear loss decreases.The composite material prepared by one-step annealing has uniform graphite dispersion,friction coefficient of 0.215,conductivity of 94.54%IACS,the composite has the best comprehensive properties and is the best annealing process.(2)With the increase of the number of cycles,the dispersion of graphite becomes uniform,the interface between graphite and matrix is tighter,grain size and conductivity decreases,the Vickers hardness and relative density increases,and the friction coefficient and wear amount decrease.After 8 cycles,the graphite can be broken to nanometer size and evenly distributed in the crystal.At this time,the relative density of the composite material is98.5%,the conductivity is 93.10%IACS,and the hardness is 128.04 HV.The friction coefficient and wear amount of 8 cycles under 20 N load are reduced by 32.5% and 49%respectively compared with that of 1 cycle.(3)After rolling,the RD-ND surface grains of the composite material are elongated along the rolling direction,and the annealing process makes the grains grow across the weld.With the increase of the number of cycles,the bonding between layers is better,the thickness of graphite layer is thinner and thinner,the grain size decreases gradually,and the grain size can’t be restored to the original size during the intermediate annealing process.(4)The RD-ND surface of the accumulative roll bonding sample is dominated by Goss,Brass etc.rolling textures,and contains shear textures E,F and Rotated Cube.The shear texture is due to the shear stress induced by the addition of graphite.The texture strength does not increase as the number of cycle increases.After annealing,the texture becomes chaotic,with Copper texture dominated. |
