Deformation processing of reaction bonded alumina ceramics

The deformation characteristics of dense, reaction bonded, zirconia dispersed alumina (RBAO) have been investigated in uniaxial compression and biaxial tension at temperatures of 1350–1500 °C. Microstructural observations demonstrate that grain boundary sliding is the dominant deformation mechanism. In the lower temperature range the stress exponent has a value near 1 and increases slightly at higher temperatures. Diffusional accommodation is most likely the rate limiting step during grain switching. The superplastic formability was assessed by deep drawing tests and it was found that high temperatures (1500°C) and low punch rates are needed to obtain crack-free specimens. Sinter forging tests were performed to analyze the potential of this pressure-assisted sintering technique to produce fine-grained, high-strength RBAO. Strengths of more than 1 GPa have been obtained by this process. The sinter forging process has been analysed in depth at 1320°C.