Effective silver assited welding of YBCO blocks: mechanical versus electrical properties

Abstract

Superconducting welding of bulk YBCO is a key technology allowing the fabrication of large, complex-shaped pieces for applications such as levitation, bearings or large magnets. Ideally, the electrical and mechanical properties of welds should be comparable to that of the joint grains. In this paper, we have investigated the correlation between the microstructural, mechanical and critical current density performances of melt-textured [001]-tilt YBCO welds fabricated by the silver welding technique. The hardness reduction across the weld, measured by nanoindentation, correlates linearly with the decrease of intergranular critical current density, measured at 77 K and self-field by magnetic Hall mapping. Remarkably, we show that high quality zero-angle welds could be fabricated with unaltered current and hardness performances across the joint, paving the way for the implementation of silver welds in large-scale systems.