Deformation mechanism map for creep in YBa2Cu3O7−x

A deformation mechanism map with grain size and stress as variables was constructed for creep in YBa₂Cu₃O_7–xat 850 and 950 °C. Theoretical models of Nabarro-Herring, Coble, and power-law creep were used for the construction. The values of various physical constants for creep of YBa₂Cu₃O_7–x were taken from the literature, or estimated with appropriate assumptions. The constructed map showed that the Nabarro-Herring creep would dominate at high temperatures in the practical range of grain size and stress, and that the power-law creep would occur at large stress (> 1 GPa) and grain size. A review of previous creep studies showed that the map is in close agreement with the experimental results. Discrepancies in the values of stress exponent and activation energy for creep of YBa₂Cu₃O_7–x given in the literature are explained by the use of the constructed map.