SINTER FORGING OF ZIRCONIA-TOUGHENED ALUMINA

Sinter forging experiments have been carried out on powder compacts of zirconia toughened alumina (ZTA) Ceramics Alumina-15 wt% zirconia was prepared by a gel precipitation method and calcined at temperatures of 900 or 1100-degrees-C. Full densification of ZTA ceramics was obtained within 15 min at 1400-degrees-C and 40 MPa. A homogeneous microstructure can be observed with an alumina grain size of 0.7 mum and a zirconia grain size of 0.2 mum. Almost no textural evolution occurred in the microstructure. During sinter forging the densification behaviour of the compacts was improved by an effective shear strain, for which values of more than 100% could be obtained. As a result of the shear deformation the densification of ZTA in the alpha alumina phase stage shifted to lower temperature. During pressureless sintering the theta to alpha alumina transformation temperature was dependent of the preceding calcination temperature, while during sinter forging this phase transformation was independent of calcination temperature and took place at a lower temperature.