The role of TiC and effect of $Y_2O_3$ addition on the densification, microstructure and mechanical properties of $Al_2O_3$-TiC composite have been investigated. The amount of $Y_2O_3$ has been varied from 0 to 2 wt.% while keeping the TiC content at 10, 20 and 30 wt.%. The powder compacts have been sintered at 1650℃, 1970℃ and 1850℃ under 1 atm Ar atmosphere. Densification and microstructure of sintered specimens have been observed with sintering time and temperature. Hardness and fracture toughness of sintered specimens have been measured by the indentation method.
Considerable increase of sintered density (over 95%) has been achieved by adding 0.5wt.% $Y_2O_3$ in the specimens sintered at 1750℃. More addition of $Y_2O_3$ does practically not affect the densification. At lower sintering temperature of 1650℃, the sintered density of the specimens does not change with $Y_2O_3$ addition. With the increase of sintering time from 0.5h to 4h, slight increase of density results. The grain growth of $Al_2O_3$ has been enhanced by $Y_2O_3$ addition; this tendency is reduced with increasing TiC content because of grain boundary dragging effect of TiC particles.
The hardness of the specimens sintered at 1750℃ increases considerably by an addition of 0.5wt.% $Y_2O_3$, owing to density increase. Further addition of $Y_2O_3$ has no effect on hardness. Fracture toughness augments with TiC content by crack deflection around the particles.
