Yb, Nd/Ca and Ce/Ca containing a-sialon starting compositions have been densified by either pressureless sintering or capsul free sinter/HIP'ing using "conventional" α-Si3N4 powder. X-ray diffraction studies of both compositions after sintering revealed that only a-sialon was observed as a matrix phase. Microstructural characterization of the relatively high nitrogen rich starting composition resulted in a typical equiaxed grain morphology, as expected. But the relatively less nitrogen rich starting composition exhibited surprisingly an elongated grain morphology with typical grain length of 5-20 urn and aspect ratios of 4-15. The mechanical property measurements on the material with equiaxed grains showed a hardness value of 19.76 GPa and a toughness value of 3.96 MPam"2 as expected. The a-sialon material with elongated grains proved to have a hardness value of 19.30 GPa (HV10) but fracture toughness value of 6.31 MPam . Crack deflection, crack bridging and grain pull-out mechanisms were accounted for the significant improvement in fracture toughness. ©2000 Trans Tech Publications,.
CITATION STYLE
Mandai, H., & Hoffmann, M. J. (2000). Hard and tough α-SiAION ceramics. Materials Science Forum, 325–326, 219–224. https://doi.org/10.4028/www.scientific.net/msf.325-326.219
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