Critical radius of zirconia inclusions in transformation toughening of ceramics

The paper presents a transformation toughening model of ceramics taking into account an energy barrier the overcoming of which results in phase transformation of zirconia inclusions. Methods based on experimental data analysis are proposed for estimating the energy barrier. The size range of zirconia inclusions in Al₂O₃ and WC matrices is defined depending on the energy barrier value, working temperature, and external load. It is shown that the introduction of an energy barrier enables an adequate estimation of the size range of inclusions at which transformation toughening occurs in ceramics. The elastic interaction of inclusions is shown to cause a decrease in their critical radii with the growing volume density, which agrees with experimental data.