Effects of Temperature and Strain Rate on the Plastic Deformation of Fully Dense Polycrystalline Y1Ba2Cu3O7−x Superconductor

The knowledge of the steady-state stress for plastic deformation as a function of temperature and strain rate is essential for hot-forming superconducting material into commercially useful shapes. In this paper, results are presented on the experimental determination of the rheology of fully dense polycrystalline Y₁Ba₂Cu₃O_7?x superconducting material at temperatures ranging from 750° to 950°C and strain rates of 10^?4, 10^?5, and 10^?6 s^?1. The data are best fitted by a power law: ε(s^?1)=8.9 × 10^?17. (s^?1) σ^2.5 (Pa) exp ?2.01 × 10⁵(J·mol^?1)|RT]. X-ray analysis shows that the superconducting material retains its phase composition after nearly 70% total strain of the sample. A strong anisotropy in the resistivity of the deformed samples is observed because of the development of a preferred orientation of the a or b axis of Y₁Ba₂Cu₃O_7?x orthorhombic perovskite single crystals perpendicular to the principal maximum compressive stress.