Phase transformations during the reaction heat treatment of Nb₃Sn superconductors

Coarse ${\rm Nb}_{3}{\rm Sn}$ Grain Formation and Phase Evolution During the Reaction of a High Sn Content Internal Tin Strand

“…During the 10 h-440 treatment most has been transformed into , but a small amount of is still detected. Since the decomposition temperature is 415 , this indicates that liquid Sn was present at the end of the 10 h-440 treatment, which was retransformed into upon cool down [7]. EDS analysis indicates that the material with relatively high atomic number around the filaments is still the presumed Cu-Nb-Sn ternary phase.…”

“…[10], but in today's state-of-the-art PIT strands a relatively large amount of coarse grains is still present. In contrast, in IT strands of the RRP design it is possible to strongly limit the growth and, as a result, only a very small amount of coarse is formed [8]. The formation of and coarse grained seems to be linked to the Sn content around the filaments in the relevant temperature range, and possibly to the presence of liquid Sn at the filament periphery.…”

“…All these phases have previously been detected during the reaction of strands of the PIT [7], Tube Type [8] and RRP [5] design. The temperature regions where the different intermetallic phases are detected are similar to those determined by diffraction measurements for the other high Sn strands [8]. The evolution of selected Cu-Nb-Sn, and Nb peak areas during the three different heating ramps (600 , 100…”

Nb3Sn nucleation and growth in multifilament superconducting strands monitored by high resolution synchrotron diffraction during in situ reaction

“…In the RRP strand the Nb 3 Sn (200) peak is first detected at 540 °C, at significantly lower temperature than the (320), (321) and (210) peaks [ 11 ], and the Nb 3 Sn (200) peak remains the largest reflection throughout the entire HT. Therefore, the Nb 3 Sn (200) peak has been selected for peak profile analysis.…”

The crystal structure of (Nb0.75Cu0.25)Sn2 in the Cu-Nb-Sn system

“…During heating experiments on wires monitored by synchrotron X-ray diffraction (XRD), the ternary phase was observed between 350 C and 580 C [15]. Several compositions of the ternary phase were reported from energy dispersive x-ray spectroscopy (EDS) measurements in a scanning electron microscope (SEM) [14,16,17].…”