Evolution of the Nanocrystalline Structure of Nb_3Sn Superconducting Layers upon Two-Stage Annealing of Nb/Cu-Sn Composites Alloyed with Titanium

摘要

The effect of diffusion annealing on the structure of superconducting layers of the Nb_3Sn phase and the extent of transformation of niobium filaments of multifilamentary Nb/Cu-Sn superconductors obtained using the bronze process has been investigated by scanning and transmission electron microscopy. The samples differed in the titanium concentration and method of alloying. It has been shown that the thickness of layers of the Nb_3Sn phase grows with an enhancement in the titanium concentration in Nb filaments and that it is composites with the alloyed bronze matrix that exhibit the most favorable structure and morphology from the viewpoint of reaching the maximum current-carrying capacity of the conductor in all of the regimes of diffusion annealing under study.