Fabrication and properties of kilometer level, Nb reinforced, 6 filamentary MgB2 wires

Kilometer level 6 + 1 filamentary MgB2 wires sheathed with Nb/Cu composite tube was fabricated by in situ powder-in-tube (PIT) method, nonferromagnetic Nb was employed as the centre reinforced materials. There is no any annealing in the whole fabrication process due to the excellent ductility of Nb/Cu based tube. The (Mg, B)/Nb/Cu composite wire was fabricated to the target size of 1.4 mm in diameter and heat treated at 680 °C for 2 h in a vacuum furnace. Microstructure, superconductivity, mechanical properties and homogeneity of critical current were measured respectively. The transport engineering critical current density (Jce) reaches 2.5 × 104 A/cm2 at 20 K, 1 T. The results show a good potential to fabricate high performance MgB2 wires at ambient pressure for practical application.