Relationship between Fracture. Toughness and Phase Assemblage in Mg‐PSZ

The phase content, size, and distribution have a marked effect on the thermomechanical properties of a 9 mol% MgO‐ZrO 2 (Mg‐PSZ) alloy. The work undertaken in this study is the first investigation to simultaneously measure and characterize the quantitative bulk phase contents and correlate these parameters to the fracture toughness and R ‐curve behavior of a variously aged Mg‐PSZ alloy. Quantitative bulk phase characterization entailed a systematic evaluation using neutron diffraction. In addition, microscopy techniques were used to determine the phase distribution and assemblage. The results indicate that the maximum toughness is attained, for a constant tetragonal precipitate size, when the anion‐ordered δ‐phase (Mg 2 Zr 5 O 12 ) replaces a major portion of the cubic matrix phase after and 1100°C aging treatment. The shape of the R ‐curve and the stress required to transform the tetragonal precipitates are also significantly influenced by the δ‐pnase content.