DEFORMATION PROCESSING OF REACTION-BONDED ALUMINA CERAMICS

The deformation characteristics of dense, reaction bonded, zirconia di spersed alumina (RBAO) have been investigated in uniaxial compression and biaxial tension at temperatures of 1350-1500 degrees C. Microstruc tural observations demonstrate that grain boundary sliding is the domi nant deformation mechanism. In the lower temperature range the stress exponent has a value near 1 and increases slightly at higher temperatu res. Diffusional accommodation is most likely the rate limiting step d uring grain switching. The superplastic formability was assessed by de ep drawing tests and it was found that high temperatures (1500 degrees C) and low punch rates are needed to obtain crack-free specimens. Sin ter forging tests were performed to analyze the potential of this pres sure-assisted sintering technique to produce fine-grained, high-streng th RBAO. Strengths of more than 1 GPa have been obtained by this proce ss. The sinter forging process has been analysed in depth at 1320 degr ees C. (C) 1997 Elsevier Science S.A.