Hot Deformation of YBa ₂ Cu ₃ O _7‐δ and Composite YBa ₂ Cu ₃ O _7‐δ /Ag

The response of ceramic superconductors and ceramic composites to compressive stresses at high temperatures has been examined. Monolithic YBa ₂ Cu ₃ O _7‐δ and composite YBa ₂ Cu ₃ O ₇ ‐δ ₆ /Ag were tested at constant true strain rates from 10 ^‐6 to 10 ^‐3 s ^‐1 at temperatures from 800° to 950°C. Fine‐grained monolithic YBa ₂ Cu ₃ O _7‐δ appears to have a regime of superplastic deformation between temperatures of 850° and 950°C at strain rates from 10 ^‐6 to 10 ^‐4 S ^‐1 . The addition of 20 vol% Ag to a coarser‐grained material enhances the ductility of the ceramic and lowers the flow stress by a factor of 3 to 10. However, there is no evidence of superplasticity in the composite material in the range of temperature and strain rate where it was tested.