Processing and mechanical properties of ZrO₂-TiB₂ composites

In this paper, a strategy is described to develop high toughness yttria-stabilised tetragonal zirconia polycrystalline (Y-TZP) composites reinforced with hard TiB₂ particles. The experimental results revealed that fully dense Y-TZP composites with 30 vol.% TiB₂, can be obtained with a moderate hardness of 13 GPa, a high strength up to 1280 MPa and an excellent indentation toughness up to 10 MPa m½ by hot pressing in vacuum at 1450 °C. The toughness of the composites can be tailored between 4 and 10 MPa m½ by varying the yttria stabiliser content of the ZrO₂ matrix between 3 and 2 mol%. An optimum composite toughness was achieved for a ZrO₂, matrix with an overall yttria content of 2.5 mol%, obtained by mixing pure monoclinic and 3 mol% Y₂O₃ co-precipitated ZrO₂, starting powders. An important observation is that the thermal residual tensile stress in the ZrO₂ matrix due to the TiB₂ addition, needs to be taken into account when optimising the transformability of the ZrO₂ matrix in order to develop high toughness Y-TZP composites.status: publishe