Alumina toughened zirconia from yttria coated powders

Alumina toughened zirconia (ATZ) ceramics are attractive materials for biomedical implants and other engineering applications requiring high strength and abrasion resistance at ambient temperature. As the toughness of conventional ATZ composites is moderate it was tried to improve the mechanical properties by starting from a very tough and transformable 2.5Y-TZP powder derived from powder coating. 2.5Y-TZP and ATZ materials with 20–40vol% of alumina were produced and tested with respect to mechanical properties, microstructure and phase composition. ATZ materials with a bending strength of up to 1900MPa and a fracture toughness of 4.8–5.5MPa√m were obtained. Transformability of the TZP distinctly declines with rising alumina content. Calculation of cooling and transformation stresses of the materials qualitatively confirms the measured toughness values. Alumina addition initially induces tensile residual cooling stress in the zirconia matrix which facilitates phase transformation. Formation of compressive stresses during transformation limits the transformability and toughness.