PROCESSING, TOUGHNESS IMPROVEMENT AND MICROSTRUCTURAL ANALYSIS OF SICPLATELET-REINFORCED AL2O3 Y-TZP NANO-CERAMIC MATRIX COMPOSITES/

Hexagonal SiC platelet-reinforced Al2O3/Y-TZP ceramic matrix composite s having sub-micron grains were fabricated. Slip casting was used as a wet colloidal processing route to minimize the processing defects and obtain preferred orientation with platelets. The effect of platelet v olume fraction and aspect ratio on fracture toughness, strength, mode and microstructure of the final composite were examined. The fracture toughness and flexural strength of the reinforced-composites were eval uated using indentation in bending and four-point bending tests, respe ctively. High resolution scanning electron microscopy (HRSEM) and tran smission electron microscopy were used to determine the microstructura l details and the dominant toughening mechanisms that occurred. Mechan ical tests and detailed microstructural results have led to the conclu sion that multiple-toughening behavior via transformation toughening, microcracking, crack deflection, load transfer and platelet pull-out a s well as thermal residual stresses have a significant contribution to improving the fracture toughness. A fracture toughness value as high as 11.2 MPa m(1/2) was achieved for a specimen sintered at 1600 degree s C for 3 h with a platelet addition of 30 vol.%. (C) 1998 Elsevier Sc ience S.A. All rights reserved.