銅-ニオブ補強安定化Nb₃Sn複合多芯超伝導線材のひずみ特性

抄録

Bronze processed multifilamentary Nb₃Sn superconducting wires with the reinforcing stabilizer CuNb in stead of the conventional Cu stabilizer were fabricated. The mechanical properties and the strain dependence of the critical current, I_c, were evaluated at 4.2K and a magnetic field of 15T. A remarkable increase in the yield stress of 70% and the plastic flow stress as compared with those in the wire with Cu stabilizer were observed. The strain for the peak I_c was also increased by 0.2%. I_c on unloading was reversible within the strain range of 1.5%. The strain sensitivity of I_c in the Cu-Nb/Nb₃Sn wire was almost the same as that of the Cu/Nb₃Sn wire. Decrease in the wire diameter from 0.8 to 0.5mm resulted in a slight increase in the flow stress of the CuNb/Nb₃Sn wire, but no change in the strain dependence of I_c. The heat treatment temperature rise from 700 to 750°C resulted in a decrease in the yield stress of 15%, but no change in the strain dependence of I_c. Marked change in morphology of Nb filament in the CuNb reinforcing stabilizer during the heat treatment was evidenced.