Relationship between microstructure and mechanical properties of fibrous HAp-(t-ZrO2)/Al2O3-(m-ZrO2) composites

The microstructure and mechanical properties of core/shell, fibrous HAp-(t-ZrO2)/Al2O3-(m-ZrO2) composites, which were fabricated by the multi-pass extrusion process, were investigated depending on the sintering temperature. In the composite sintered at 1200 °C, many pores were observed in both HAp-(t-ZrO2) core and Al2O3-(m-ZrO2) shell regions. However, at 1500 °C, the shell regions showed dense and anisotropic grain growth and the core region were transformed to α-TCP and β-TCP phase. Also, as a minor reaction phase, the CaAl12O19 peaks detected. The values of relative density, hardness, bending strength and fracture toughness increased as the sintering temperature increased, and their maximum values were at 1500 °C about 890 Hv, 280 MPa and 4.1 MPa m1/2, respectively. The fracture morphology was appeared with homogeneously rough surface, and indentation cracks showed short length due to the crack deflection and microcracking toughening mechanisms.