Mechanical Properties and Ageing Resistance of Slip Cast and Pressurelessly sintered ZTA - the Influence of Composition and Heat Treatment Conditions

Abstract

Zirconia toughened alumina (ZTA) ceramics are used in a broad range of mechanical engineering and biomedical applications due to their excellent mechanical and tribological properties. In this study it was tried how the change in stabilizer composition and sintering conditions can be exploited to selectively modify the mechanical properties and low temperature degradation resistance of ZTA materials with a typical biomedical grade composition. It was found that the materials react very sensitively to such changes. Fully dense materials combining favorable mechanical properties such as high strength > 800 MPa, fracture toughness > 5.5 MPa√m and LTD resistance can only be produced in a narrow stabilizer concentration range between 1.1-1.2 %. Beyond this range materials are either insufficiently stabilized which results in poor strength and high tendency to LTD, or overstabilized and no longer susceptible to stress induced phase transformation and therefore too brittle. Changes in reinforcement mechanisms can be attributed to changes in microstructure and phase composition caused by variation of stabilizer content and sintering conditions.