DENSIFICATION AND MICROSTRUCTURE DEVELOPMENT OF ALUMINA/Y-TZP COMPOSITE POWDER (Y-TZP-RICH) COMPACTS

Al2O3/Y-TZP composite powders (Y-TZP-rich) were prepared by ball milling submicron-sized alumina and coprecipitated nano-sized Y-TZP powders. The densification behavior of the composite powder compacts is studied and it is shown that the shrinkage rate is reduced at lower temperatures and the composites continue to shrink at elevated temperatures compared to single phase tetragonal Y-TZP. Compacts of the composite powders isostatically pressed at 250MPa at room temperature show duplex pore size distributions due to the presence of alumina, and it is these unusual pore size distributions, rather than the stresses arising from the differential sintering of the secondary particles that are believed to be the source of the retarded densification during constant rate heating. In spite of the retarded densification behavior, the composite powder compacts containing not higher than 30 vol.% alumina, can be sintered in 2 h to above 98% of the theoretical density at 1550 degrees C.