AN UNUSUAL TWIN STRUCTURE IN TRANSFORMED PRECIPITATES IN Y-PSZ SINGLE-CRYSTALS

Mosaic-like monoclinic ZrO2 particles form in TEM thin foils in 3.4-mol%-Y2O3-partially-stabilized ZrO2 (Y-PSZ) single crystals aged for 150 h at 1600-degrees-C. These particles transformed martensitically during TEM foil preparation; the parent phase existed as internally twinned tetragonal ZrO2 precipitates which had formed during aging. These monoclinic particles contain (100)m and {110}m transformation twins, and the twin variants have uniform thickness. The origin of this transformation microstructure, the lattice correspondences, and the applicability of the invariant plane strain model of martensitic transformations are discussed.