Localized yielding during high temperature deformation of Y2O3-fully-stabilized cubic ZrO2 single crystals

A series of Y2O3 fully-stabilized cubic ZrO2 single crystals with high solute contents were compressed at high temperatures along [112] and [001]. Two distinct types of deformation were observed, uniform and localized. Plastic instabilities and localized yielding corresponded to high strength conditions, sigma greater than or equal to 300 MPa, in [112] compression samples with low initial dislocation densities. A variety of prestraining, static aging and strain rate jump tests show that the Portevin-Le Chatelier (PLC) effect is not operational in these alloys. While thermal feedback can have a significant effect on the deformation of these materials, thermomechanical instabilities are not the source of the instabilities. The triggering mechanism appears to be structural softening caused by avalanche multiplication of mobile dislocations. Coupling of this type of instability with localized thermal softening is used to explain the characteristics of localized deformation, including the 300 MPa ''critical'' flow stress at which localized slip occurs. Copyright (C) 1996 Acta Metallurgica Inc.