High strength and toughness alumina matrix composites by transformation toughening and 'in situ' platelet reinforcement (ZPTA)

High purity alumina ceramics have been used for more than 25 years in biomedical applications due to their excellent wear behaviour and high strength. Nevertheless great effort have been undertaken to develop a material with increased strength combined with excellent wear properties. One candidate material family is ZTA-ceramics. Out of this family a new generation of that material is available now in which high strength, high toughness, high hardness and wear properties are combined. This material is a zirconia and platelet reinforced alumina ceramic (ZPTA). In more details ZPTA-ceramics are based on an alumina matrix containing homogeneously distributed metastable zirconia particles and ''in situ'' formed hexagonal ternary aluminate platelets of a length of about 3 {mu}m and a thickness of 0,3 {mu}m. The chemical composition and the microstructure were optimised to achieve a ceramic material combining all required properties: strength of more than 1200 MPa, fracture toughness of 6,5 MPa{radical}(m) and Vickers hardness HV{sub 1} of 1975 are typical. Extremely low wear rates have been detected in ring-on-disc and HIP simulator tests. (orig.)