2002 Volume 43 Issue 7 Pages 1557-1560
Internal friction of alumina polycrystals with engineered grain boundaries was measured in the low frequency range of the torsional forced-vibration. The maximum shear stress amplitude was 50 MPa. Owing to the very high temperature reached during these experiments (1900 K), internal friction spectra could be detected which reveal new important features of the intrinsic rheological behavior of alumina grain boundaries. The monotonically rising internal friction background and the torsional creep behavior, both of a diffusive origin, were systematically characterized upon modifying the grain-boundary structure of alumina with the addition of selected cation dopants (e.g., Titanium and Lutetium). The combined characterizations of internal friction spectrum and torsional creep rate enabled us to precisely assess the role of different cation dopants on “locking” or promoting the diffusive grain-boundary flow, which governs polycrystal deformation.
