Bimaterial Composites via Colloidal Rolling Techniques: III, Mechanical Properties

The mechanical properties of layered Ce-TZP/Al₂O₃ composites with laminate and cellular morphologies have been investigated. The strength and toughness increase as the layer thickness decreases, and the amount of transformation in the Ce-TZP layer increases discontinuously at the laminate/cellular transition. Very high strengths (1.1 GPa) and toughnesses (16 MPa·m^1/2) have been obtained in some cases. These results indicate that the progressive refinement of layer microstructure and the disruption of planar connectivity of phases are beneficial to the mechanical performance, because they provide more stress concentrators to trigger stress-assisted transformation for toughening functions. The composites of finer microstructure, with a layer thickness of lessthan equal to20 µm, have a homogeneous hardness of 11.5 GPa, which is a considerable improvement over that of Ce-TZP alone.