Microstructure and mechanical properties of SiC whisker reinforced ZrO2–6 mol.-%Y2O3 composites

Microstructure, mechanical properties, fracture behaviour, and toughening mechanisms of hot pressed SiC whisker (SiCw) reinforced ZrO2–6 mol.-%Y2O3 composites were investigated via transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and mechanical testing. The experimental results show that there is a continuous increase in the Vickers hardness, elastic modulus, and fracture toughness of the composites with increasing SiCw content, and an addition of 30 vol.-%SiCw increases the fracture toughness from 3·42 MN m−3/2 for the unreinforced matrix to 5·83 MN m−3/2. The flexural strength is increased from 293 MN m−2 for the unreinforced matrix to a maximum of 372 MN m−2 by an addition of 10 vol.-%SiCw, then it is significantly decreased by further increasing the SiCw content. Observations via transmission electron microscopy show that no distinct second phase or intermediate layers form at the SiCw/ZrO2 interface. Diffusional separation of tetragonal phase from the cubic matrix occurred during cooling after hot pressing. Whisker bridging and crack deflection are the main toughening mechanisms, but whisker pull-out, crack branching, and refinement of the matrix particles also contribute to the improvement in the fracture toughness. MST/1747