Mechanical and Friction Properties of Al2O3-ZrO2-TiC Composite with Varying TiC Contents Fabricated by Spark Plasma Sintering

Al2O3-ZrO2-TiC composites with different proportions of TiC were prepared by ball milling and spark plasma sintering. Structural characterization revealed that the composites exhibited fine and homogeneous microstructures. No other phases except alpha-Al2O3, t-ZrO2 and c-TiC were detected by XRD in all Al2O3-ZrO2-TiC composites. The internal stress induced by the mismatch of the thermal expansion coefficients result in a shift of t-ZrO2 diffraction peak. SEM and TEM observations showed that the Al2O3 grain size was inversely proportional to the TiC content, while the grain sizes of ZrO2 and TiC stayed nearly constant. HRTEM micrograph presented that there are glassy phase boundaries with thickness of several nanometers around the TiC grains. As the TiC content increases, the relative density and hardness decreased from 99.2 to 97.7 pct and from 21.0 to 15.8 GPa, respectively. Compared with Al2O3-ZrO2 matrix, composites with TiC exhibited lower flexural strength but enhanced fracture toughness. Composite with TiC of 10 vol pct possessed the best friction property. The increased porosity was mainly responsible for the deterioration of mechanical and friction properties except for the fracture toughness. The improvement in fracture toughness with increasing TiC content was attribute to the crack deflection and pinning effects induced by the TiC particles.