Mechanical and superconducting properties of 6-filament MgB2 wires reinforced by Cu, Cu–Nb and NbTi

Abstract The comparisons of strengthening abilities of Cu, Cu–Nb, and NbTi for 6-filamentary MgB 1.92 (TiC) 0.08 /Nb/Cu wires and the electrical properties of the best reinforced wire are investigated. The Cu–Nb reinforcing core is more appropriate for manufacturing MgB 2 wires. It is observed that the Cu–Nb reinforced wire sintered at 750 °C for 2 h has the highest yield strength of 101.8 MPa. With the sintering temperature increasing, the yield strength of the Cu–Nb and NbTi reinforced wires increased while the value slightly decreased in the case of Cu reinforced one in this study. According to our calculations, those mechanical properties are suitable for the application requirements of superconducting magnets in low field with the critical engineering current I c of 197 and 205 A ( J ce exceeding 1.7 × 10 4 and 1.8 × 10 4  A/cm 2 ) before and after 70 MPa axial load on the wire at 20 K, 1.5 T respectively. And within the working temperature range from 10 K to 35 K, the Cu–Nb reinforced wires show the lowest resistivity as well. The Cu–Nb reinforced long MgB 1.92 (TiC) 0.08 /Nb/Cu wires with unit length over 1 km have already been manufactured using the similar process. The Cu, Cu–Nb, and NbTi reinforced 6-filament MgB 1.92 (TiC) 0.08 /Nb/Cu wires are fabricated by in situ PIT (Powder-in-Tube) method respectively.