High-resolution transmission electron microscopy of transformed magnesia-partially-stabilized zirconia precipitates

Transformed Mg-PSZ precipitates consist of monoclinic bands that are twin-related across either (100)m or (001)m planes in an arrangement that leads to accommodation of the shear component of the transformation shape strain. High-resolution images of these variants reveal these twin relationships quite clearly. It is shown that complete compensation of shear does not always occur. This paper also shows observations of monoclinic variants related by a rotation of 90° around the normal to (001)m, in addition to those related by a 180° rotation for the twin-related variants. These findings conform to the predictions of martensite theory and their implications are discussed in terms of shear compensation and reduction in overall strain energy.