Electromechanical Properties of Filamentary $\hbox {MgB}_{2}$ Wires

This work describes the performance of several MgB₂ composite wires when subjected to tensile stress at 4.2 K. Electromechanical properties of these wires are influenced by the composite elements encasing the filament and also by the filament´s mechanical strength. A linear increase in critical current by tension up to ≈20% was measured due to compensation of the precompression effect caused by different thermal expansions of composite elements. Final heat treatment influences the electromechanical characteristics of composite wires due to stress recovery and also by interface reactions among the composite elements. Results showed that the highest irreversible strain ε_irr = 0.9 % was obtained for MgB₂ wires reinforced by stainless steel, which has more than doubled ε_irr in comparison to commercially available MgB₂/Nb/Cu/Monel wires with the same filament number.