Effect of Al2O3 and Fe3Al on the phase formation and mechanical properties of β-sialon

The paper evaluated the mechanical properties of beta-sialon composites prepared by hot-pressing sintering at 1600 degrees C in N-2 atmosphere using alpha-Si3N4, Al2O3, Y2O3 and Fe3Al as raw materials. The influence of Al2O3 and Fe3Al content on flexure strength, fracture toughness, hardness, and relative density was investigated. And phase formation and morphology of the composites were characterized by X-ray diffraction and electron microscopy. The experimental results indicate that the raw material Fe3Al reacts with alpha-Si3N4 to form silicides at elevated temperature, and supplies more liquid phase to assist densification. Besides, the variation of flexure strength, fracture toughness and hardness is mainly consistent, and also in good agreement with the relative density measurements. The values all increase firstly, and then decrease when the Al2O3 content increases. Scanning electron microscopy illustrates that the metal particles act to inhibit the crack propagation. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.