TOUGHNESS DETERMINATION OF ZIRCONIA-TOUGHENED ALUMINA CERAMICS FROM GROWTH OF INDENTATION-INDUCED CRACKS

Short surface cracks were generated by Vickers indentation on the poli shed surface of alumina and different zirconia toughened alumina (ZTA) specimens, and their morphology was studied by serial sectioning. The se cracks were grown in three-point bend tests under stepwise loading, and variation of toughness with crack extension was plotted to graphi cally separate the contributions from residual stress intensity and ap plied stress intensity factors. The plateau toughness determined from the intercept height of the crack extension plots exhibited an upward trend with zirconia content up to 15 vol% ZrO2 addition in the composi tion, which was proportional to the fraction of transformable tetragon al grains contributing to transformation toughening.