Influence of the tin diffusion process in multifilamentary Nb-Cu-Sn-Mg-Ta wire on Nb/sub 3/Sn 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 properties of the intermetallic Nb/sub 3/Sn diffusion layers of "high tin" multifilamentary conductors formed during multistage heat treatment is essential 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 wire during multistage heat treatment. The importance of the rapid conversion of /spl epsi/-Cu/sub 3/Sn on filament displacement and mechanically induced inter-filamentary bridging within the individual bundles is demonstrated. It is concluded that the architecture of the conductor and phase development in the Cu-Sn-Mg matrix are the two major factors responsible for Nb/sub 3/Sn inter-filamentary bridging.