Effects of room-temperature tensile fatigue on critical current and n-value of IBAD-MOCVD YBa₂Cu₃O_7-x/Hastelloy coated conductor

REBa₂Cu₃O_7-x (REBCO) coated conductors potentially enable a multitude of superconducting applications, over a wide range of operating temperatures and magnetic fields, including high-field magnets, energy storage devices, motors, generators, and power transmission systems (Zhang et al 2013 IEEE Trans. Appl. Supercond. 23 5700704). Many of these are AC applications and thus the fatigue properties may be limiting (Vincent et al 2013 IEEE Trans. Appl. Supercond. 23 5700805). Previous electromechanical studies have determined the performance of REBCO conductors under single cycle loads (Barth et al 2015 Supercond. Sci. Technol. 28 045011), but an understanding of the fatigue properties is lacking. Here the fatigue behavior of commercial ion beam assisted deposition-metal organic chemical vapor deposition REBCO conductors on Hastelloy substrates is reported for axial tensile strains up to 0.5% and up to 100 000 cycles. Failure mechanisms are investigated via microstructural studies. Results show that REBCO conductors retained I _c(ϵ)/I _c0 = 0.9 for 10 000 cycles at ϵ = 0.35% and ϵ = 0.45% strain, and ϵ = 0.5% for 100 cycles. The main cause of fatigue degradation in REBCO conductors is crack propagation that initiates at the slitting defects that result from the manufacturing process.