CHARACTERIZATION OF AL2O3-ZRO2 POWDERS PRODUCED BY ELECTROHYDRODYNAMIC ATOMIZATION

The roles of supercooling and alloy composition in the microstructure evolution of rapidly solidified powders have been systematically examined across the Al2O3ZrO2 binary system. Powders ranging in diameter from 10 nm to over 100 μm were produced by electrohydrodynamic atomization of Al2O3ZrO2 rods prepared by colloidal techniques. At the largest supercoolings (powders less than 1 μm), single-phase homogeneous structures, both amorphous and crystalline, may be observed across the entire phase diagram. With increasing particle size, segregation gives rise to duplex microstructures which consist of metastable alumina and monoclinic or tetragonal zirconia, or of tetragonal zirconia and glass. Coarse (greater than 10 μm) powders exhibit different morphologies in the primary phase and the eutectic constituent, with varying supercoolings and cooling rates. The trends in phase selection and segregation are examined with the aid of available information on Tg and schematic T0 curves for the different phases. © 1990.