TRANSFORMATION AND MICROCRACK TOUGHENING AS COMPLEMENTARY PROCESSES IN ZRO2-TOUGHENED AL2O3

Both tetragonal (t) and monoclinic (m) ZrO//2 particles in ZrO//2-toughened Al//2O//3 can give rise to toughening. The t-ZrO//2 particles transformed in crack tip stress fields do not, however, also cause appreciable microcracking. The toughening increments via these distinct mechanisms are comparable. It appears that optimally fabricated ZrO//2-toughened Al//2O//3's should contain a mixture of t- and m-ZrO//2.