Mechanical properties of Al2O3/ZrO2 composites

In the present study, both t-phase zirconia and m-phase zirconia particles are incorporated into an alumina matrix. Dense Al2O3/(t-ZrO2+m-ZrO2) composites were prepared by sintering pressurelessly at 1600 °C. The microstructure of the composites are characterized, the elastic modulus, strength and toughness determined. Because the ZrO2 inclusions are close to each other in the Al2O3 matrix, the yttrium ion originally in t-ZrO2 particles can diffuse to nearby m-ZrO2 particles during sintering, and the m-phase zirconia is thus stabilized after sintering. The strength of the Al2O3/(t-ZrO2+m-ZrO2) composites after surface grinding can reach values as high as 940 MPa, which is roughly three times that of Al2O3 alone. The strengthening effect is contributed by microstructural refinement together with the surface compressive stresses induced by grinding. The toughness of alumina is also enhanced by adding both t-phase and m-phase zirconia, which can reach values as high as two times that of Al2O3 alone. The toughening effect is attributed mainly to the zirconia t–m phase transformation.