The Study Of Diffusion Reactiomn Process In Nb/A1Interface And The Pre-design Of Heat Treatment Apparatus For Nb₃A1Precursor

There are three intermetallic compounds existing in Nb/Al binary system:NbAl3, sigma-Nb2Al, and A15-Nb3Al. These niobium aluminides are of interest as candidates for extremely high temperature structure materials for their high strength at elevated temperature, high melting point, high elastic modulus, excellent oxidation resistance and low densities. At the same time, Nb3Al often came into people’s notice as a very potential A15structure superconducting material since its outstanding properties inherently than A15-Nb3Sn such as higher superconductivity transition temperature (Tc) of about18.9K, higher upper critical field (Bc2) of about30T, higher critical current density (Jc) at high filed, and dramatically better strain tolerance. Hence, Nb3Al had been seen as an alternative to Nb3Sn which is now widely used in high-field and large-scale applications, for instance ITER plan, high energy particle accelerators and gigaherzs class nuclear-magnetic-resonance (NMR) and so on.In the first chapter, a review of the development history, the basic characteristics, the classification and characterization of superconducting materials have been introduced. Furthermore, the research significance, the status and perspective of A15type compounds superconductors Nb3Al superconducting material also present in this chapter.In the second chapter, the fabrications of NbsAl in native and foreign such as Nb3Al wire, multilayer films and powder metallurgy, etc, had been reviewed briefly. The experimental instruments and measurement principles in this study were introduced, too.In the third chapter, the fabrication process of Nb3Al precursor with7cores which was used to study the equilibrium process of Nb/Al binary system was introduced. The diffusion process in Nb/Al interface has been reaserched in wide temperature range from700℃to1500℃. the result are as follows:NbAl3was the single phase formed at700℃/48h; the Nb:Al≈-1:1reaction layer which is considered a mixed layer of NbAl3, Nb2Al and Nb occurs at (800-900)℃/48h and disappears at1000℃/48h, at the same time, Nb2Al reaction layer about2μm in thickness, and increase with the heat treatment temperature; off-stoichiometric Nb3Al reaction layer which is decided by Nb/Al binary phase diagram was obtained above1400℃. It can also be concluded that the temperature of solid reaction plays more important role in the formation of Nb3Al than the heat treatment time.In the fourth chapter, RHQ apparatus pre-designed by our team have been introduced. Base on first generation RHQ apparatus in Japan, a new RHQ apparatus which includes many promotions such as working parameter, function requirement, wire routes apparatus, and quenching apparatus and so on is designing. The vibration of the moving wire will be controlled accurately in our apparatus.