Composition dependence of dynamic Young's modulus and internal friction in Al2O3-3Y-ZrO2 composites

The effects of the 3Y-ZrO2 content in Al2O3-3Y-ZrO2 composites on the specific dynamic Young's modulus and the internal friction values were investigated using the resonance method in the flexural vibration of a free- free bar to measure these properties. It was found that, with the increase of 3Y-ZrO2 content, the dynamic Young's modulus decreased linearly, showing a large inflection point at about 20 percent of 3Y-ZrO2 and a small one at 65 percent. The internal friction increased initially to a peak at 17 percent of 3Y-ZrO2 and decreased to a trough at 40 percent. It was also found that the dynamic Young's modulus inflection points corresponded in composition to peaks in the specific loss modulus (calculated from the values of Young's modulus and the internal friction). It was concluded that these features were due to the tetragonal to monoclinic transformation of the ZrO2 phase, and that the increase of internal friction at above 40 percent was due to the flexural deformation caused by shearing force. (I.S.)