DEFORMATION MECHANISM MAP FOR CREEP IN YBA2CU3O7-X

A deformation mechanism map with grain size and stress as variables wa s constructed for creep in YBa2Cu3O7-x at 850 and 950 degrees C. Theor etical models of Nabarro-Herring, Coble, and power-law creep were used for the construction. The values of various physical constants for cr eep of YBa2Cu3O7-x were taken from the literature, or estimated with a ppropriate assumptions. The constructed map showed that the Nabarro-He rring 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 stu dies showed that the map is in close agreement with the experimental r esults. Discrepancies in the values of stress exponent and activation energy for creep of YBa2Cu3O7-x given in the literature are explained by the use of the constructed map.