Effect of SiC Whisker Orientation on Mechanical Properties of Si3N4 Ceramic Composites

초록

The effect of uni-directional orientation of SiC whisker on the flexural strength(FS) and fracture toughness(KIC) of SiC Si3N4 composite ceramics were investigated. The results obtained were as follows. (1)The flexural strength was increased from 100 MPa to about 1150 MPa(about 15% increase) and KIC was also increased from 6.0MPam1/2 up to 9.4MPam1/2(about 37% increase). KIC of the specimen with uni-directional orientation(WL specimen) was 95% higher than that of the monolith. (2)The degree of crack deflection in the WL specimen was small, compared with that in the conventional specimen, there was no correlation between the degree of crack deflection and KIC, indicating that the higher KIC of the WL specimen could be ascribed to the increase of the load transfer effect by the uni-directional orientation of SiC(w). The effect of the uni-directional orientation of SiC(w) was presumed to be promoted by the preferential orientation of acicular Si3N4 grains, which was mainly caused by the uni-directional orientaion of SiC(w).