Study On The Formation And Influence Of Cube Textuer Of Ni5W Alloy Substrate For Coated Conductors

The second-generation high-temperature superconducting material represented by YBa₂Cu₃O_7-?(YBCO)has high critical temperature,electrical conductivity,and irreversible field,which is the focus of the superconducting field.The substrate is the basis and key of the coated superconducting.The Ni5W alloy substrate is one of the main substrate materials for coating superconductors,and the researchers also proposed the Ni5W/Ni9.3W/Ni5W composite alloy substrate to improve its mechanical properties and reduce magnetic losses.However,the current research on Ni5W and Ni5W/Ni9.3W/Ni5W substrate has mainly focused on its preparation process and application.The recrystallization mechanism and formation of cubic texture cannot be explained by systematic theory.In this paper,the recrystallization mechanism of Ni5W and Ni5W/Ni9.3W/Ni5W will be studied.The main results are as follows:The Ni5W alloy substrate was prepared by melting method.The evolution of microstructure,texture and the formation mechanism of cubic texture in recrystallization were studied by ex-situ EBSD technology.The results have shown that the recovery structure of Ni5W was continuously coarsening,the content of rolling orientation was decreased,the content of random orientation and cube orientation was increased.In recrystallization,the number of randomly oriented nuclei was the largest,while the cubic nuclei did not have the advantage of nucleation.The grains of each orientation grown up,especially the cube grains.The average size of the grains was much larger than that of the other orientation grains,which had the obvious size advantage.Moreover,the shape of grains changed from the long lamella to equiaxed,and the aspect ratio decreased continuously.The content of cubic orientation increased greatly,and the content of random orientation and rolling orientation decreased,indicating that a large number of randomly oriented grains and rolled oriented grains were swallowed up by the cube grains to form the cube texture.The Ni5W/Ni9.3W/Ni5W composite alloy substrate was prepared by powder metallurgy.The nucleation and growth of grains,the formation mechanism of cube texture and the diffusion of elements between inner and outer layers were studied by SEM,EBSD,EDS,PPMS,etc.The results showed that the high quality Ni5W/Ni9.3W/Ni5W composite alloy substrate can be prepared by powder metallurgy and proper heat treatment process and the texture uniformity on surface is good.The high content of tungsten in the internal layer limited the growth of grains.The cubic grains in the surface layer can grow and form a strong cube texture in the surface layer by annexing the internal grains.At the same time,it promotes the mutual diffusion of elements in the internal and external layers,so that the mutual diffusion of elements and the growth of grains can be carried out synchronously.The element diffusion between the inner and outer layers made the composition distribution of the composite substrate more uniform,but it did not have an obvious effect on its magnetic properties.To sum up,the recovery recrystallization evolution and formation mechanism of cubic texture of Ni5W and Ni5W/Ni9.3W/Ni5W were studied in this paper,which laid a good foundation for the preparation of higher-performance Ni W alloy substrate and promoted the industrialization of high-temperature superconducting tape.