The effect of sintering aids and contents of SiC whisker on the densification phenomena and mechanical properties of SiC whisker-alumina composites has been studied at sintering temperature of 1700, 1800, and 1900℃. The densification phenomena and mechanical properties of SiC whisker-alumina composite after hot isostatic pressing have been studied also. SiC whisker-alumina composites were doped with 2 wt% $TiO_2$, 2 wt% $Y_2O_3$, and 0.5 wt% MgO, respectively and the content of SiC whisker varied up to 15 vol%.
More than 95% of theoretical density has been obtained up to 15 vol% SiC whisker content sintered at 1900℃ with 2 wt% $Y_2O_3$ sintering aid. Fully dense SiC whisker-alumina composite was obtained by hot isostatic pressing of the presintered body which had above 95 % of theoretical density. Grain growth was not observed after hot isostatic pressing compared with presintered body.
In the case of $Al_2O_3-Y_2O_3$ system, it was observed by XRD and EDS analysis that YAG Phase continuously crystallized at the grain boundary when the composites sintered above 1800℃. This phenomenon suggests that $Al_2O_3-Y_2O_3$ eutectic melt was formed above 1800℃, and crystallized during cooling process. Also, among the sintering aids, $Al_2O_3-Y_2O_3$ system is usable for densifying SiC whisker-alumina composites having high content of SiC whisker.
The maximum 3-point bending strength and fracture toughness of 2 wt% $Y_2O_3$ doped 15 vol% SiC whisker-alumina composites sintered at 1900℃ were 425 MPa and 4.3 MPa m, respectively. After hot isostatic pressing, 3-point bending strength and fracture toughness of 2wt% $Y_2O_3$ doped 15 vol% SiC whisker-alumina composites presintered at 1900℃ were increased to 480 MPa and 5 MPa m, respectively.