Processing and properties of ZrO2-containing reaction-bonded aluminum oxide with high initial aluminum contents

The reaction-bonded aluminum oxide (RBAO) process relies upon the oxidation of Al/Al2O3 powder compacts, and many of its associated advantages stem from the presence of the aluminum in the green powder. Higher aluminum contents in the starting powders allow for higher green strengths, densities, and lower overall shrinkage, all while producing a fine-grained, high-strength sintered material. However, it is evident that the reaction and sintering of ZrO2-containing RBAO with higher aluminum contents are more challenging. Therefore, in this study, the effects of aluminum content on the processing, structure, and properties of RBAO ceramics were comprehensively characterized. It was found that RBAO samples with high aluminum contents were more prone to cracking during reaction and even when successfully fired were not able to be sintered to full density. Despite these characteristics, RBAO samples with increasing aluminum contents showed no significant degradation in mechanical properties.