Al2O3 composites with different volume fractions of 3Y-TZP (3 mol% yttria-doped tetragonal zirconia polycrystalline) were prepared by using a colloidal process and pressure-casting into green specimens, then were pressureless sintered to full density at 1550oC. The resulted two-phase microstructure contained uniformly distributed and submicro- meter-sized grains. The addition of 15 vol% ZrO2 resulted in an increase in bending strength (average 656 MPa by 4 pt. test). Appreciate amount of m-ZrO2 phase was detected after fracture. The enhanced transformability results in an increase in flexural strength and toughness. The addition of 30 vol% ZrO2 resulted in best toughness (5.4 MPam0.5) and outstanding wear resistance (7.2×10-8 cm3/Nm).