研究論文
Nb3Sn 超電導線用高Sn ブロンズ中のTi 基三元化合物の挙動
2015 年 50 巻 4 号 p. 186-193
詳細
2015 年 50 巻 4 号 p. 186-193
High tin bronze is used as a component of practical Nb3Sn superconducting wires. In particular, the addition of titanium to bronze is well known to improve superconducting properties as well as the workability of the bronze alloy. In the present study, change in the microstructure of bronze by adding titanium was investigated. The important results are summarized as follows. First, when the Cu-10.5 at%Sn-0.72 at%Ti alloy was held at 550oC for 1000 min, three phases of primary α, γ and CuSnTi (Ti111) were equilibrated. Second, after holding at 750oC for 1000 min, three phases of primary α, β and CuSn3Ti5 (Ti135) coexisted. Third, during heating from 560oC to 750oC, a remarkable phase change was observed near 675oC, below which the Ti111 phase was dominant, but above which the principal Ti-based compound phase was Ti135. Fourth, in the present region of alloy composition and heat treatment temperature, two invariant reactions of Ti135 + β = α + Ti111 and α + β = γ + Ti111 were recognized to take place in the Cu-Sn-Ti ternary system. Finally, characteristic features of workability at room temperature as well as at elevated temperatures could be well explained in conjunction with the behavior of titanium ternary compounds.
