TRANSFORMATION TEXTURES IN ZIRCONIA

The large shear component of the tetragonal-to-monoclinic transformati on in zirconia causes a stress-induced preferred orientation of the te tragonal and monoclinic variants. The resultant texture, which is depe ndent on the loading condition, has been analyzed in terms of stress a ssistance to transformation and experimentally verified in simple tens ion and compression. Such a preferred orientation is a clear indicatio n of the shear contribution to transformation plasticity and to fractu re. Other implications of this analysis are also explored. For example , while the monoclinic texture is obviously most relevant to generatin g strains and plastic work, it is the tetragonal texture which might b e advantageously tailored to enhance transformability and toughness. T ransformation texture causes the ratio of {111} monoclinic and tetrago nal X-ray peaks in tensile fracture to be higher than the actual ratio of monoclinic-to-tetragonal phase fractions, making it generally unsu itable for estimating phase fraction in stress-induced transformation.