Sn Diffusion Behavior and Microstructure in Nb₃Sn Wires with Third Elemental Addition

Abstract

Element addition plays an important role in the improvement of the physical properties of the Nb₃Sn phase itself and of growth kinetics in the Nb₃Sn diffusion reaction process. This paper first reviews the fundamental reaction behavior between Nb and Sn in the presence of Cu, which is the integral element for the thick Nb₃Sn layer formation at a low temperature reaction, and interprets it in view of Sn chemical potential. Then the paper reviews several advanced element additions to realize breakthrough grain refinement, touching on their grain refinement mechanism. Subsequently, the recent topic of Ti and Ta addition is examined, followed by the addition of unique elements that bring functional enhancement such as mechanical strengthening of the wire.