Defect and Diffusion Forum Vol. 391

Abstract: In the present study, the Nb₃Sn-based multifilamentary wires with coupled Nb filaments have been investigated by SEM and TEM after various regimes of intermediate annealing including short high-temperature heat treatments and after two-staged diffusion annealing. The formation of some amount of pre-reacted Nb₃Sn layers has been revealed in all the wires studied, and their amount depends on the wire diameter, temperature and duration of the intermediate heat treatment. The structure of final diffusion layers is also affected by the regimes of these preliminary treatments. This research enables the revealing of the optimal heat treatment schedules for the formation of most perfect nanocrystalline structure of superconducting layers ensuring the highest critical current densities.

Abstract: We present results of the constructive critical analysis and interpretation of some recent studies (Blavette, Sauvage, Wilde and others) at the atomic scale (using three-dimensional atom-probe field-ion microscopy) of impurity nanosegregation at dislocations, including “Cottrell atmospheres”, and grain boundaries in deformed intermetallics and metallic materials, and their relevance to mechanical properties and diffusion processes.