INFLUENCE OF THE TIN DIFFUSION PROCESS IN MULTIFILAMENTARY NB-CU-SN-MG-TA WIRE ON NB3SN INTER-FILAMENTARY BRIDGING

An understanding of the correlation between the diffusion of tin from a high tin reservoir to the niobium filaments and the uniform properti es of the intermetallic Nb3Sn diffusion layers of ''high tin'' multifi lamentary conductors formed during multistage heat treatment is essent ial for the further improvement of the superconducting electromagnetic properties of advanced conductors. A detailed study has been made of the formation of the A-15 layer in multifilamentary Nb-Cu-Sn-Mg-Ta wir e during multistage heat treatment. The importance of the rapid conver sion of epsilon-Cu3Sn on filament displacement and mechanically induce d inter-filamentary bridging within the individual bundles is demonstr ated. It is concluded that the architecture of the conductor and phase development in the Cu-Sn-Mg matrix are the two major factors responsi ble for Nb3Sn inter-filamentary bridging.