Microstructure characterization of fibrous HAp-(20Â vol.% t-ZrO2)/Al2O3-(25Â vol.% m-ZrO2) composites by multi-pass extrusion process

Core-shell structured HAp-(t-ZrO2)/Al2O3-(m-ZrO2) composites were fabricated using a multi extrusion process. The shell of Al2O3-(m-ZrO2) phases was selected due to their excellent biocompatibility and mechanical properties and the core was designed with t-ZrO2 dispersed in the HAp matrix. The t-ZrO2 and m-ZrO2 particles (< 400 nm) were homogeneously dispersed in the HAp and Al2O3 phases, respectively. In the HAp-(t-ZrO2) core region, a heavy strain field contrast was observed due to the mismatch of their thermal expansion coefficients. The values of relative density, bending strength and Vickers hardness of the third pass fibrous HAp-(t-ZrO2)/Al2O3-(m-ZrO2) composites, which were sintered at 1400 °C, were about 93%, 169 MPa, and 792 Hv, respectively.