Evaluation of the threshold stress for creep deformation in a 3 mol% Y 2 O 3 -stabilized tetragonal ZrO 2 polycrystal

The origin of the increase in the stress exponent from n , 2.0 to with decreasing stress in 3 mol% Y 2 O 3 -stabilized tetragonal ZrO 2 has been examined. The present data show that the increase in the n value arises from the existence of a threshold stress that depends on the grain size and temperature. Careful examination of earlier creep data confirms that evaluation of the threshold stress is sensitive to the accuracy of the creep data and the value of n chosen for the compensation of the data. Inspection of the present results and some recent observations of the deformed microstructure suggests that the threshold stress is associated with intragranular dislocation motion.