Mechanical properties and toughening mechanisms of silicon carbide nano-particulate reinforced Alon composites

Aluminum oxynitride (Alon) has been considered as a potential ceramic material due to excellent stability, chemical and mechanical properties such as high rigidity and good chemical stability, but it has relatively low strength and poor fracture toughness. The aim of this study was to investigate a type of silicon carbide (SiC) nano-particulate reinforced Alon composites with improved mechanical properties and fracture resistance via hot-press sintering. The addition of SiC nano-particles resulted in a reduction of both porosity and grain size, and a change of fracture mode from intergranular cracking in the monolithic Alon to intragranular cracking in the composites due to the pinning effect of SiC nano-particles positioned at grain boundaries or triple junctions of micro-sized Alon particles. With 8 wt% SiC nano-particles addition, the relative density, microhardness. Young's modulus, flexural strength, and fracture toughness all increased. Different toughening mechanisms including crack bridging, crack branching and crack deflection were observed, thus effectively increasing the crack propagation resistance and leading to a considerable improvement in the flexural strength and fracture toughness of the composites. (C) 2012 Elsevier B.V. All rights reserved.