Study of the Specific Features of Kinetics Formation and Structure of the Superconducting Nb3Sn Phase in Technical Superconductors

The growth kinetics of a layer of intermetallic compound Nb3Sn in bronze-processed multifilamentary superconductors of different designs and diameters, developed and fabricated at the A.A. Bochvar High-Technology Research Institute of Inorganic Materials (JSC “VNIINM”), has been studied. The influence of diffusion annealing conditions in a wide range of temperatures and exposure times on the formation of Nb3Sn phase in superconductors has been investigated by methods of metallographic analysis using optical microscopy, electron microscopy, and microanalysis. The structural features of Nb3Sn layers in the initial formation stage and after long-term diffusion annealing are analyzed, their thickness is measured, and the grain structure and composition are studied. Recommendations on improvement of the diffusion annealing conditions for Nb3Sn superconductors of different designs, aimed at obtaining high current-carrying ability, are elaborated.