Model analysis of boundary residual stress and its effect on toughness in thin boundary layered yttria-stabilized tetragonal zirconia polycrystalline ceramics

摘要

The average thermal residual stress in acontinuous boundary phase in polycrystalline ceramiccomposites was calculated with a simple thin boundary layermodel, and a criterion for the self-cracking of the boundaryphase was derived under a certain assumption. From theproposed model, the toughness of the materials can be increasedby both tensile and compressive stress at boundaries when thecrack propagates transgranularly. The toughness will beincreased when the stress at boundary is compressive forintergranular fracture mode. The maximum increase is predictedto be achieved at boundary phase contents below 33 percent.The experimental results for yttria-stabilized tetragonal zirconiapolycrystalline ceramics doped with different kinds of grain-boundary phase is in a qualitative agreement with the predictionby the model, but the toughness increase is largely dependent onthe distribution feature of glass phases.