Mechanical properties of Y-Ba-Cu-O blocks welded by silver added Y-Ba-Cu-O solder

We have performed tensile tests at room temperature for Y-Ba-Cu-O bulk superconductors with artificial grain boundaries, which were fabricated by a joining technique using Ag added Y-Ba-Cu-O solder. The tensile strength of the joint was lower than that of the mother block Y-Ba-Cu-O. Microstructural analyses revealed that a residual liquid phase was observed in the vicinity of the interface between the mother block and the solder in the ac-plane. Cross-sectional observation for the samples after the tensile tests showed that the fracture occurred along the residual liquid phase. Hence, the residual liquid phase was responsible for the lower tensile strength.