Investigation On Electrochemical Machining Of Metal Substrate

The Apperance of YBa2Cu3O7-δ(YBCO) coated conductors opens up a new route to practical application of high temperature superconductor. Coated conductors contain textured substrate, transition layer and superconducting layer three main parts. As a carrier of the coated conductors, substrate is one of the main factors which detemine the performance of superconducting material. Due to the level limiting of rolling technology, the surface quality of metal substrate cannot meet the requirements of coated conductor technology. Therefore this paper use the pulse electrochemical technology to improve the surface quality of the substrate. High cost in subsrate is the major obstacle to the large-scale application of coated conductors. Therefore we hope to prepare biaxially texured metal film on nou texured high strength metal substrate by electro-deposition technology which meet the requirements of epitaxial growth coated conductors. It is possible to develop a low cost manufacture technology to texured substrate for coated conductors,which greatly reduces the manufacturing cost of coated conductors.The research content has the following several aspects:(1) Using enviroment friendly phosphoric acid and glycerol buffer additives as the polishing system. Using Pulse electro-polishing to research the influences of pulse parameters, namely current density, pulse frequency and pulse duty cycle on the polishing effects of NiW substrate. The polishing substrate microstructure surface were characterized by scanning electron microscope and atomic force microscope. Also looking for the best pulse polishing process according to the test results. Results show that substrate surface quality of nano scale roughness can be obtained under the polishing process.(2) Cu has been deposited on nikle substrate by electro-deposition method. After electro-polishing the substrate’s surface, we will get uniform and smooth metal surface. In order to find the best approach of preparing continuous and compact Cu film, we explore the optimal parameters of electro-deposition. The results show that the continuous and compact copper films can be prepared by best electrodeposition process, which provide good transition layer for the subsequent depositionof silver films(3) Ag has been deposited on substrate by electro-deposition method. The Cu surface quality will be improved by pulse electrochemical polishing method. First we explore wethere the cectroplating has oriention function, and deposition film texture under different parameters. Then find the best approach of preparing (111) textured film. Metal films’crystal orientation, crystallization and surface morphology are characterized by X-ray diffraction and scanning electron microscope. Results show that electro-deposition is oriented and Ag (111) layer can be plated by appropriate pulse parameters.(4) Ag (200) layer with biaxial texture on Cu substrate has been plated by using of a novel principle electroplating unit which developed independently by ourselves. Cu/Ag composite substrate with (200) oriented biaxially texture was prepares by this kind of oriented plating function. Ag film grain orderly arrangement in a-b plane with in-plane texture.(5) (200) textured Ag buffer layer has been deposited on biaxially textured NiW substrate by chemical deposition method. After heat treatment, the texture of Ag film deposited on copper substrate transfered from (111) preferential orientation to (200) preferential orientation.