| Pure copper has good conductivity,thermal conductivity and elongation properties.It is widely used in electronics,wires and contact wire materials.Whereas the lower strength limits its application in the important areas.This study aims at the problem of low strength of highly conductive pure copper.The evolution of microstructure and texture were studied by OM,SEM,EDS,TEM,EBSD and XRD during ECAP by different deformation routes.Analyze the factors that affect the performance of pure copper during ECAP.Then explore the evolution of precipitates on its mechanical properties and conductivity after alloying by adding a small amount of Zr and Si elements and treated with solid solution + ECAP deformation + aging treatment.The results showed that the uniform shear bands were formed inside the single crystal structure during ECAP by route A and C after 4 passes.The directional solidification pure copper were ECAPed after 4 passes by route Bc,the shear bands intersect each other,which is conducive to formation of uniform equiaxed crystals.During the ECAP process of polycrystalline copper by route A and C,homogeneous fibrous structure were formed and the grain boundaries transformed from random to ordered state along the extrusion direction,the refinement effect for route C is worse than the route A,for the route Bc,equiaxed crystals were formed.The Cu-Zr-Si alloy in as-cast is treated by ECAP deformation and different aging process,after aging for 1h at 375°C,400°C,450°C and 500°C,a small amount of granular and plate-like precipitates appeared discontinuously distribute along grain boundaries and slip lines,As the aging time increases,the content of precipitates at grain boundaries increases and the matrix.The addition of a small amount of Si elements facilitates the refinement and dispersive distribution of the precipitated phase in the matrix.XRD and EBSD detection methods indicate there different original microstructure of Cu shows(111)preferred orientation during ECAP by route A and C,for the Bc route,the crystal orientation are randomly distributed.Single crystal copper were ECAPed after 4 passes by route A and C,the rotation-cube texture {001}<110> was formed.After 6 extrusion passes by route C,{111}<110> texture was formed.After 8 extrusion passes by route A,the weak recrystallization texture {001}<100> and {111}<110> and {111}<112> texture were formed,and the texture strength is significantly weakened.The tensile strength and elongation are maximal during ECAP by route A after 5 passes,which are 415 MPa and 30%,respectively,and the conductivity remains at a high level,which is 98.8%IACS,After 16 passes,the hardness of route A is most,which is 133 HV.When polycrystalline copper was ECAPed through 4 passes by route C,the conductivity increased from 91.8%IACS to 94.5%IACS.When the directional solidification pure copper was ECAPed through 4 passes by three routes,the conductivity are maintained at a high level around 98% IACS.When the Cu-Zr-Si alloy in as-cast was ECAPed after 1 passes and treated by aging at 450 for 4h,the Cu-Zr-Si alloy in as-cast has the best mechanical and conductivity,the conductivity is 78.3%IACS,the hardness is 151 HV,and at the same time,it maintains high plasticity and the elongation is 21.9%.ECAP method can significantly increase the strength of the material while having a small effect on the conductivity.The tensile strength of single crystal copper increased by 147%,the hardness increased by 122%,while the conductivity is only reduced by 2.7%,and the elongation is still maintained at 30%.the conductivity decreased by only 1% after 4 passes for directional solidification pure copper.On the contrary,the conductivity increased by 3% after 4 passes for polycrystalline copper.The discontinuous distribution of precipitates is conducive to the significant improvement of mechanical properties and electrical conductivity during heat treatment. |
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