HERTZIAN CONTACT DAMAGE IN MAGNESIA-PARTIALLY-STABILIZED ZIRCONIA

Hertzian contact damage in magnesia-partially-stabilized zirconia is e xamined. Ceramographic techniques and acoustic emission reveal the dam age patterns to be fundamentally different in the as-fired, peak-aged, and over-aged states. Indentation stress-strain curves show that the plasticity component of the contact deformation increases monotonicall y with aging time. Whereas the tetragonal-monoclinic transformation pl ays an important role in the peak-aged material, alternative deformati on processes dominate in the other states: microcracking in as-fired, and monoclinic twinning in over-aged.