Measurement of Irreversible External-Compressive Strain at RT and Enhancing Strain Tolerance at RT on MgB₂ Multifilament Wire

The strain tolerance of magnesium dioboride (MgB2) wire should be enhanced at room temperature for fabricating MgB2 coils by using the react and wind method. The irreversible external-compressive strain of MgB2 filaments was measured by evaluating the critical current degradation of bent sample wires. From the results, MgB2 filaments can accept -1.77% strain, and the pre-compressive strain should be -0.88% at room temperature to minimize its reversible bending radius. A stainless-steel reinforced 18-filament MgB2 wire was fabricated and its strain tolerance was evaluated through bending and tensile tests at room temperature. The irreversible strain of this wire is 0.60%, and this wire seems to be suitable for the react and wind method. The filling factor of MgB2 of this wire is 17%, so this wire has both suitable strain tolerance for the react and wind method and higher engineering current density.