PROCESSING OF TAPE-CAST LAMINATES PREPARED FROM FINE ALUMINA-ZIRCONIAPOWDERS

This paper addresses the effect of thermocompression pressure, shear d eformation of green laminates, and postsinter HIPing on the microstruc tural homogeneity of cast tapes and laminates prepared from fine Al2O3 and Al2O3/ZrO2 powders. Green density increases with increasing therm ocompression pressure. Sintered densities, however, depend more on the macroscopic uniformity in the green tapes. When density gradients dev elop within the individual green tapes (because of improper drying), s intering is constrained in two dimensions and densities remain low. Po stsinter HIPing does not significantly increase the sintered densities because of the retention of open porosity within the individual tape- cast layers. The use of a revised thermocompression process involving shear deformation results in higher sintered densities and complete de nsification after HIPing. Sintered densities increase with the degree of shear strain during green-state deformation processing. Thus, green -state deformation can improve homogeneity in laminates. A further var iation of the shear deformation process has also been developed that a llows the formation of complex shapes from tape-cast laminates in the green state, while retaining layer integrity.