ALUMINA PLATELET REINFORCED REACTION-BONDED ALUMINUM-OXIDE COMPOSITES- TEXTURED AND RANDOM

The RBAO (Reaction Bonded Aluminum Oxide) process and water-based gel casting were combined to produce alumina platelet reinforced RBAO comp osites, In the RBAO process, a precursor powder mixture of Al metal an d Al2O3 is reacted to form 100% ceramic, To obtain composites in which the platelets are highly aligned, tapes consisting of 10 vol, % homog eneously distributed alumina platelets and 90 vol, % RBAO precursor po wder were made by water-based gel casting using an extended doctor bla de arrangement. Pellets of textured composites were subsequently prepa red by stacking sheets cut from the green tapes, and filter pressing, Randomly oriented platelet composites were made using the same startin g powders and gelling procedure, but without the tape-casting step, Re action bonding was carried out in a box furnace in air. Microstructure s of the composites were characterized using x-ray diffraction (XRD) a nd scanning electron microscopy (SEM). The effect of platelet orientat ion on contact damage behavior was studied using a Hertzian indentatio n method. It was found that the textured composite exhibited improved damage resistance compared to the random composite.