Strength of Crack Healed-Specimen and Elastic Wave Characteristics of Al2O3/SiC Composite Ceramics

Al2O3/SiC composite ceramics were sintered to evaluate the bending strength and elastic wave characteristics. The three-point bending test was carried out under room temperature. The elastic wave was detected by fracture wave detector. The crack healing behavior was investigated from 1373 K to 1723 K. The bending strength of Al2O3/SiC composite by nanocomposite is higher than that of Al2O3 monolithic. Crack-healing behavior depended on an amount of additive powder Y2O3. In Al2O3SiC composite ceramics with 3 wt. % Y2O3 for additive powder, the bending strength at 1573 K is about 100% increase than that of the smooth specimens. From the result of wavelet analysis of elastic wave signal, the smooth specimen and heat treated specimen of Al2O3 monolithic and Al2O3/SiC composite ceramics showed characteristics of frequency about 58 kHz. The strength of Al2O3/SiC composite ceramics was a little higher than those of Al2O3 monolithic. The dominant frequencies were high with increasing of Y2O3 for additive powder. The dominant frequencies had direct connection with the bending strength.