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Nb3Sn superconductor wires were investigated in terms of Nb3Sn 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°C/24 h (ramp rate 10° C/hour) + 340°C/ 48 h (ramp rate 25°C/hour) + 700°C/up to 150 h (ramp rate 10° C/hour)). Reaction heat treatments at 700°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 Nb3Sn reaction rate was determined for strands with and without Ti, and Ti was seen to double the rate of Nb3Sn 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.