Mechanical Properties and Cyclic Fatigue of the Newly Developed Ceramic Material for Artificial Joints

Abstract

Alumina ceramics have been used as components of artificial hip joints because of their high hydrophilicity and hardness. However, improvement of fracture toughness and fatigue resistance of the alumina ceramics is required to enhance their reliability in clinical use. In this study, we synthesized a novel alumina-zirconia composite and evaluated its mechanical performance. It has superior mechanical properties, such as a 4-point bending strength of 1250 MPa and fracture toughness of 4.7 MPa•m^0.5. Namely, the bending strength and fracture toughness of the composites were similar to those of commercial Y₂O₃-stabilized zirconia ceramics. We then evaluated the cyclic fatigue properties of the composites. The alumina-zirconia composite did not break even after 10⁷ cycles under 625 MPa, but all of the pure alumina samples broke after the same number of cycles under 484 MPa. It appears that the alumina-zirconia composite has higher survival reliability under cyclic loadings than the alumina, although anti-fatigue properties could not be quantitatively interpreted. These phenomena can be attributed to the dispersion of rod-shaped particles in the matrix and the fine grain size of the composites.