Nb/sub 3/Sn superconductor wires were investigated in terms of Nb/sub 3/Sn phase formation and Ti diffusion. Two series of subelement strands (HP and EG) with Ta, Ti addition were fabricated. For comparison, a special model sample consisting of an annular Nb region containing Sn and surrounded by Cu was fabricated. All samples were given a standard initial up-ramp-and-hold schedule (185/spl deg/C/24 h (ramp rate 10/spl deg/ C/hour) + 340/spl deg/C/ 48 h (ramp rate 25/spl deg/C/hour) + 700/spl deg/C/up to 150 h (ramp rate 10/spl deg/ C/hour)). Reaction heat treatments at 700/spl deg/C were performed for various times on these subelements. The diffusion of Sn and Ti was studied by SEM, EDS, EPMA and STEM analysis. The Nb/sub 3/Sn reaction rate was determined for strands with and without Ti, and Ti was seen to double the rate of Nb/sub 3/Sn formation for these strands. EDS analysis showed that within the filament annular shell, an even distribution of Ti existed with a concentration of 0.4-1.0 at. %. However, for the highest Ti bearing sample, it had a Ti Nausite at the filament boundaries which may reduce the strands superconductor property.
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Wu et al. (2005) studied this question.
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