クラッド・チップ押出し法によるNb₃Snの線材化

抄録

The Clad-Chip Extrusion (CCE) method is applied to a fabrication process of Nb₃Sn superconducting wires. This method is characterized by extruding the chipped Nb-Sn clad sheets with the intended chemical composition. Ti-foil cladding to the Nb-Sn composite sheet is also studied as a method of titanium addition. An extruded Nb-Sn composite bar shows good workability in wire drawing up to a relatively high reduction ratio, R of 10⁶, where R is the cross-section ratio of an initial billet to a final wire.
The CCE-processed Nb₃Sn wire heat-treated under the optimum condition shows the critical transition temperature, T_c of 17.8 K and the critical current density, J_c of 1.18×10⁸ A·m⁻² in the applied magnetic field of 20 T at 4.2 K. The upper critical field, B^∗_c2 (4.2 K) is estimated as 23.4 T using the Kramer plot.