Crack-tip transformation zones of CeO_2-stabilized tetragonal ZrO_2 polycrystals

摘要

The toughness of certain ceramics can be increased by transformation plasticity at the crack tip because this provides the requisite energy dissipation and stress-field shielding for toughening [I]. The amount of toughness enhancement depends principally on the transformation zone shape and the detailed transformation plasticity distribution within the zone. The transformation zone shape can be detected by several techniques, such as X-ray diffraction (XRD), Raman spectroscopy and observations by optical interference methods of surface distortions due to transformation plasticity [2-4]. However, these methods have not yet been used to provide a sufficiently quantitative measurement of the distribu-tion of the transformation plasticity. Moire inter-ferometry is a high sensitivity, high spatial resolu-tion, whole-field optical method of measurement of in-plane displacement. It can reveal the micro-mechanical behaviour of the materials to a certain degree [5]. Some works measuring the transforma-tion plasticity of toughened zirconia have been done by moire interferometry [6,7]. In this letter, transformation zone branching at the crack tip is revealed at room temperature and the detailed distribution of transformation plasticity strain is obtained by moire interferometry.