ABSTRACT
During a study of room temperature creep in high toughness commercial Mg-PSZ, neutron diffraction was used to quantify the phase transitions which had occurred. As expected, substantial transformation of tetragonal to monoclinic zirconia was found but, unexpectedly, the tetragonal to orthorhombic transformation was also discovered. The orthorhombic phase was found to represent up to 10% of the strained volume of the cylindrical tensile creep specimens and is crystallographically identical to that formed in Mg-PSZ when it is cooled to below ~200K. The ratio of the orthorhombic phase content to the new monoclinic phase content (that is, additional to that in the starting material) is similar in this series of specimens. The stress-induced orthorhombic phase has only been observed in samples with very high creep strains and hence its presence is related to the transformability of the ceramic. These results add weight to the proposition that the tetragonal to orthorhombic transformation is martensitic.
