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 α-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.