Mechanical properties of reinforced MgB2 wires

For technical application in windings of coils, transformers or motors, a reinforcement of MgB₂ wires and tapes is necessary to withstand applied stresses and strains and to avoid cracks in the filaments. Therefore, the response of the superconducting transport currents on applied axial strain in different magnetic background fields was investigated for differently stainless steel reinforced MgB₂ wires, by means of an axial strain rig. Increased amounts of stainless steel in the sheath caused a stronger decrease of the critical currents in fields above 3 T as a consequence of a changed irreversibility field. Heat treated wires have a quite different mechanical behavior compared to as-cold-worked wires, but an about 10 times higher transport current level. Tape geometries, having generally higher current carrying capabilities than wires, showed much poorer mechanical properties with a less effective filament precompression from the matrix.