時効処理を施したNb 46.5 mass%Ti超伝導線の臨界電流密度特性
1994 年 58 巻 6 号 p. 591-595
詳細
1994 年 58 巻 6 号 p. 591-595
It is well known that, in Nb-Ti superconducting wire, critical current density, Jc, in external magnetic field is crucially controlled by the α-Ti precipitates. Therefore, clarifying its dependence on the heat treatment condition is important to increase Jc still more. In the present study, the characteristic of Jc during heat treatment is investigated using copper-sheathed Nb-46.5 mass%Ti monofilamentary wires which are cold-worked at ε=6.29 prior to the heat treatment. The heat treatment procedure is performed isothermally at temperatures between 300 and 500°C. The precipitation behavior of α-Ti phase against heat treatment conditions is estimated assuming that Jc varies proportionally to the volume fraction of α-Ti precipitates. It is considered that α-Ti phase precipitates most vigorously around 400°C and that, after 1000 h treatment at 400°C, the volume fraction of the precipitated α-Ti reaches up to 20%. A T.T.T. diagram in the Nb-Ti system is also demonstrated based of the present results.
