ELASTIC PROPERTIES AND MICROCRACKING BEHAVIOR OF PARTICULATE TITANIUMDIBORIDE-SILICON CARBIDE COMPOSITES

The spontaneous microcracking of particulate TiB2-SiC composites is st udied as a function of TIE, volume fraction, The degree of microcracki ng was examined by measuring elastic properties from room temperature to 1300 degrees C, The results showed that only one composition contai ns microcracks, All other compositions did not microcrack regardless o f TIB2 volume fraction, This was attributed to the difference in the s intering aids, In particular, the Al2O3 sintering aid needed in these compositions had reacted with SiO2 to form an amorphous grain boundary phase that allowed residual stresses to relax by viscous how at moder ate to high temperatures, The existence of this amorphous grain bounda ry phase was directly observed by transmission electron microscopy.