MECHANICAL-PROPERTIES AND FRACTURE-TOUGHNESS OF ALPHA-AL2O3-PLATELET-REINFORCED Y-PSZ COMPOSITES AT ROOM AND HIGH-TEMPERATURES

YPSZ/Al2O3-platelet composites were fabricated by conventional and tap e-casting techniques followed by sintering and HIPing. The room-temper ature fracture toughness increased, from 4.9 MPa.m1/2 for YPSZ, to 7.9 MPa.m1/2 (by the ISB method) for 25 vol% Al2O3 platelets with aspect ratio = 12. The room-temperature flexural strength decreased 21% and 3 0% (from 935 MPa for YPSZ) for platelet contents of 25 vol% and 40 vol %, respectively. Al2O3 platelets improved the high-temperature strengt h (by 110% over YPSZ with 25 vol% platelets at 800-degrees-C and by 40 % with 40 vol% platelets at 1300-degrees-C) and fracture toughness (by 90% at 800-degrees-C and 61% at 1300-degrees-C with 40 vol% platelets ). An amorphous phase at the Al2O3-platelet/YPSZ interface limited mec hanical property improvement at 1300-degrees-C. The influence of plate let alignment was examined by tape casting and laminating the composit es. Platelet alignment improved the sintered density by > 1% d(th), hi gh-temperature strength by 11% at 800-degrees-C and 16% at 1300-degree s-C, and fracture toughness by 33% at 1300-degrees-C, over random plat elet orientation.