Fracture toughness, strength and slow crack growth in a ceria stabilized zirconia–alumina nanocomposite for medical applications

Abstract Mechanical properties and slow crack growth (SCG) behavior of a 10Ce-TZP/Al2 O3 nanocomposite currently developed as a biomaterial are considered. Fracture toughness is determined for sharp, long (double torsion) and short (indentation) cracks and a good agreement is found between the two types of cracks. The main toughening mechanism in the nanocomposite is the tetragonal to monoclinic phase transformation of the ceria-stabilized zirconia (Ce-TZP) phase. Transformation at the surface of ground specimens leads to surface compressive induced stresses and an increase in strength. Crack velocity curves ( V – KI curves) are obtained under static and cyclic fatigue using the double torsion method. The static V – KI curve in air reveals the three stages characteristic of stress corrosion with a threshold KI0 ∼ 4.5 MPa m1/2 and a fracture toughness of 8.8 MPa m1/2 significantly higher than those of currently used inert bioceramics (i.e. alumina and Y-TZP). A crack growth accelerating effect is shown under cyclic loading, correlated with a decrease in the threshold. However, the cyclic fatigue threshold (4 MPa m1/2 ) still stands above that of current biomedical grade alumina and zirconia.