Effect of Zr on growth kinetics, microstructure and microtexture of Nb3Sn by bronze technique

Abstract

We have experimentally studied a systematic quantitative effect of Zr on the factors influencing the critical current density of Nb3Sn, such as growth kinetics, microstructure and microtexture using a diffusion couple method. The Nb3Sn phase develops in the interdiffusion zone of the Cu(Sn)/Nb diffusion couple. For the Zr-alloyed diffusion couples, a two-phase mixture of Zr-containing Nb3Sn and sub-micron β-(Nb,Zr) solid solution second-phase develops. The growth kinetics of Zr-containing Nb3Sn is higher than the Zr-free Nb3Sn phase. Enhancement of growth kinetics is attributed to an increase in the diffusion flux of the Sn atoms along the grain boundaries of Nb3Sn owing to grain refinement. The Zr-free Nb3Sn phase has a weak crystallographic texture. On the other hand, the Zr-containing Nb3Sn phase develops not only with a strong crystallographic texture, but also has similar texture component as that of the adjacent Nb-rich parent phase.