Elastic Properties and Microcracking Behavior of Particulate Titanium Diboride–Silicon Carbide Composites

The spontaneous microcracking of particulate TiB 2 –SiC composites is studied as a function of TiB 2 volume fraction. The degree of microcracking was examined by measuring elastic properties from room temperature to 1300°C. The results showed that only one composition contains microcracks. All other compositions did not microcrack regardless of TiB 2 volume fraction. This was attributed to the difference in the sintering aids. In particular, the Al 2 O 3 sintering aid needed in these compositions had reacted with SiO 2 to form an amorphous grain boundary phase that allowed residual stresses to relax by viscous flow at moderate to high temperatures. The existence of this amorphous grain boundary phase was directly observed by transmission electron microscopy.