The Study Of Preparing Technology Of Ni-5at.%w Alloy Substrates For Ybco Coated Conductor

The YBa2Cu3O7-δ(YBCO) coated conductor has the advantages to be low ac loses, high in-field performance and low processing costs. So fabrication techniques of low-cost and high performance YBCO Coated Conductor have been becoming the focus of practicable high temperature superconductor research. Because the characteristics of metal substrates (e.g. texture, roughness of surface and so on) directly determine the characteristics of buffer layes and further influence the superconducting performance of YBCO layer. Therefore, the preparation of high quality metal substrates is one of vital technologies for coated conductor.It was concluded from the literature that Ni-5at.%W alloy is an ideal material as substrate for coated conductor. From the view of low-cost and scale-up production, the rolling assisted biaxially textured substrates (RABiTS) technology with significant commercial potential is popular for the fabrication of substrate. Therefore, the study of fabricating Ni-5at.%W alloy substrate by RABiTS technology was carried out in my experiments. The microstructure and the crystal orientations of substrate were measured by means of optical microscope, scanning electron microscope (SEM), X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD). According to the testing results, the fabrication technique of metallic substrates was optimized and improved.The Ni (99.9%) and W (99.99%) powders were mixed as starting materials. A Ni-5at.%W substrate with a thickness of 80μm was fabricated by swaging, drawing and cold rolling a ingot (Φ20×100), which was prepared by combining a powder metallurgy process with remelting two times in a intermediate frequency induction furnace. The results of the research for rolling process show that the total deformation has great effect on the formation of cube texture. The heavier the total deformation, the more greater the tensity ofβ-fiber and the more sharper the cube texture after recrystallization annealing. Lower deformation per pass is more conducive to a uniaxial deformation during mechanical deformation treatment and developing higher degree of cube texture if inhomogeneous deformation was not appeared. The substrate with 5% reduction per pass attains the sharpest cube texture after recrystallization annealing. The effective total deformation was too low to allow the substrate to attain sharp cube texture in the process of middle annealing.Recrystallization annealing process is important factor that can be effect the formation of cube texture. From the experiments some results can be concluded as follows:Annealing temperature has great effect on the formation of cube texture. It was not only affect the fraction of cube texture, but also affect the speed of recrystallization and the orientation of grains. After primary recrystallization annealing time has no great effect on the formation of cube texture and the microstruture. Heating rates greatly affect the recrystallization texture of cold-deformed metals. Heating with slow speed (≤6℃/min) can reinforce the development of cube texture, but heating with quick speed (≥6℃/min) can not. The strong cube texture was obtained through an optimized two-step recrystallization annealing following heavy cold working.Therefore, the results of experiments have been shown that high cube texture fraction (within 8°around ideal {001}<100> texture) was obtained in Ni-5at.%W alloy substrate with a thickness of 80μm which was fabricated by swaging, drawing and heavily cold rolling a ingot prepared by combining a powder metallurgy process with remelting two times in a intermediate frequency induction furnace, and then annealed at 1300℃for 1h (Ar4H2).