Composition dependence of dynamic Young's modulus and internal friction in Al2 O3 -3Y-ZrO2 composites

The specific dynamic Young's modulus E'/rho and the internal friction Q/sup -1/ of Al2 O3 -3Y-ZrO2 composites with different 3Y-ZrO2 content were investigated. With the increase of 3Y-ZrO2 content, the E'/rho decreased linearly showing a large inflection point at about 20% and a small one at 65%, and the Q/sup -1/ reached a peak at 17% and a trough at 40%, and increased showing a shoulder at about 70%. The specific loss modulus E''/rho calculated from E'/rho and Q/sup -1/ showed the peaks at 17% and 65%. The E''/rho peaks corresponded with the E'/rho inflection points in composition. As a result, it was estimated that they were due to the tetragonal to monoclinic transformation of ZrO2 phase, and that the increase of internal friction at above 40% was not due to the crack formation and the ZrO2 phase transformation, but due to the flexural deformation caused by shearing force