PROCESSING OF TAPE-CAST LAMINATES PREPARED FROM FINE ALUMINA-ZIRCONIA POWDERS

This paper addresses the effect of thermocompression pressure, shear deformation of green laminates, and postsinter HIPing on the microstructural homogeneity of cast tapes and laminates prepared from fine Al2O3 and Al2O3/ZrO2 powders. Green density increases with increasing thermocompression pressure. Sintered densities, however, depend more on the macroscopic uniformity in the green tapes. When density gradients develop within the individual green tapes (because of improper drying), sintering is constrained in two dimensions and densities remain low. Postsinter 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 densification 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 variation of the shear deformation process has also been developed that allows the formation of complex shapes from tape-cast laminates in the green state, while retaining layer integrity.