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

Abstract

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.