Materials Science and Engineering A, Structural Materials: Properties, Microstructure and Processing vol:427 issue:1-2 pages:195-202
A powder mixture of alpha-Si3N4, Al2O3, and TiO2 was hot-pressed using different sintering cycles to search for an optimum in situ formed P-O-sialon-TiN composite. The impulse excitation technique (IET), high-temperature X-ray diffraction (HTXRD), and scanning electron microscopy (SEM) were used to investigate the microstructure. Below the temperature of 1300 degrees C, the high-temperature internal friction (Q(-1)) decreases with the increase of sintering temperature, whereas the density of the material increases with the increase of sintering temperature. At a sintering temperature higher than 1850 degrees C, the ceramic could not be densilied and O-sialon was not formed. Also, the mechanical properties of ceramics hot-pressed using different sintering cycles were assessed. The ceramic hot-pressed at 1700 degrees C for 10 min displays a combination of high hardness and good fracture toughness, due to an optimum combination of beta-sialon, O-sialon, and TiN-phases. This paper also evaluated the thermal expansion of beta-sialon in the different ceramics hot-pressed using different sintering cycles. (c) 2006 Elsevier B.V All fights reserved.