Study On The Electrocrystallization Behavior Of Copper In Industrial Electrolytes And The Microstructure And Properties Of Deposited Layers

Copper plays a very important role in the development of human society,and is widely used in electrical and electronic industries,machinery and automobile manufacturing industry,chemical industry,defense industry,construction industry and so on.Among them,cathodes copper have high purity,electrical conductivity,thermal conductivity,corrosion resistance and good mechanical properties,which are important for reducing energy consumption,improving energy efficiency,saving raw materials and miniaturizing equipment,and occupy a dominant position in the copper market.Therefore,the development of cathodes copper will become the guide for the domestic copper market.The cathodes copper used in the market today are generally prepared by electrodeposition.The most commonly used processes in industry are conventional electrolysis and permanent cathode copper electrolysis（ISA）.In this paper,cathodes copper of the same cycle produced by conventional method of different companies and cathodes copper produced by two processes of conventional method and ISA method of the same company are studied,and the microscopic morphology,grain size,grain orientation and fracture morphology of cathodes copper are analyzed by XRD,OM and SEM,and the mechanical properties of cathodes copper are analyzed by universal testing machine,impact testing machine and micro hardness tester,as well as the EBSD is used to Grain morphology,grain size distribution,grain orientation,grain boundary characteristics and cross-sectional grain morphology,grain size distribution,grain orientation and growth mode were analyzed on the surface of cathodes copper of different companies.In addition,this paper used industrial electrolyte with different concentrations of Ce₂（SO₄）₃ to obtain the cathodic copper deposition layer by electrodeposition in a Harlem bath,and analyzed the microscopic morphology,grain size and grain orientation of the copper deposition layer by SEM,AFM and XRD,and whether the rare earth element Ce was doped into the deposition layer by EDS.The effects of different concentrations of Ce₂（SO₄）₃ on the electrochemical behavior of copper deposited layers were investigated by cathodic polarization curves（LSV）,cyclic voltammetric curves（CV）and chrono-current curves（CA）to find the optimal rare earth content suitable for grain refinement of copper deposited layers.The study found that:（1）The surface of cathodes copper produced by the conventional electrolytic method of the four companies all show strong selective orientation in the（220）crystal plane,and the homogenization of the weave has a certain effect on the grain refinement,while there is a certain connection between the grain size and the mechanical properties,which shows that the smaller the grain size,the higher the material strength,hardness and toughness,but the grain refinement affects the plastic deformation ability of the material and reduces the elongation.In addition,all four companies’cathodes copper show characteristics typical of ductile fracture,and the abnormal fracture phenomenon during the tensile process indicates that the presence of defects such as nodules can have a great impact on the performance of cathodes copper.（2）The surface grain morphology of cathodes copper produced by the conventional electrolytic method of the four companies was nearly equiaxed,and the grain size showed a pattern of:A<B<C<D.As the electrodeposition proceeds,the cross-sectional grain morphology changes from equiaxed crystals to columnar crystals on the smooth side and columnar crystals on the rough side,and the grain size shows a pattern of:A<B<D<C.All four companies exhibit a strong<110>weave on the surface and cross-section of the cathode copper.The surface grain boundaries are mainly large-angle grain boundaries,and there are a large number of∑3ⁿ grain boundaries.The shape of the initiation sheet has a small effect on the deposited layer,and the two sides of the initiation sheet deposit copper in different ways,with the smooth side of the initiation sheet being re-core and the rough side being continuation growth.（3）Both conventional and ISA cathode copper exhibit strong selective orientation in the（220）crystal plane,and both growth modes are mainly outward growth.Compared with the traditional cathode copper,the apparent mass of the ISA cathode copper is relatively better,the strength and plasticity of the material are relatively higher,the microstructure is more uniform,the tensile property is relatively better,the strength and plasticity of the material show the advantages of isotropy.In addition,the cathode copper produced by the two processes of the same company has similar hardness,and both have high brittle fracture resistance.（4）The surface grain orientation of the cathodes copper produced by both the conventional and ISA methods exhibit a strong<110>weave.The average grain size of cathode copper by conventional method is 8.39μm,and the average grain size of cathode copper by ISA method is 7.20μm,and the grain size shows a pattern of:conventional>ISA.Both conventional and Isa method cathode copper surface grain boundaries are dominated by large-angle grain boundaries,and a large number of twins exist.（5）The copper deposited layer has a certain orientation,and the degree of selective orientation is greatest at（220）,and the degree of selective orientation gradually decreases at（220）as the concentration of Ce₂（SO₄）₃ increases.Meanwhile,the addition of Ce₂（SO₄）₃ to the industrial electrolyte does not change the electrocrystallization nucleation mechanism of copper,which remains a three-dimensional transient nucleation with increased nucleation number density and increased overpotential.When the addition amount of Ce₂（SO₄）₃ is 0.8 g/L,the degree of cathodic polarization as well as the nucleation number density is the largest,which is conducive to the formation of nuclei and inhibits the growth of grains,and the copper deposition layer with fine grains can be obtained with the best effect.