Critical Radius in the Effect of Transformation Toughening of Zirconia Doped Ceramics and Cermets
Possible increase in fracture toughness of ceramics can be derived from stress induced martensite transformation from tetragonal to monoclinic polymorph of ZrO2 particles embedded into a bulk ceramic material. The incidence of transformations depends on zirconia particle size: too small particles remain overstabilized and do not experience transformation while too large particle may spontaneously transform at the technological stage of cooling. The critical particle size is, therefore, of primary concern for toughening of intrinsically brittle materials. We give a brief review of the previous results obtained. Then basing on the Gibbs energy expression and taking into account interface surface energy as well as thermal stresses, external loading and elastic interaction of the inclusions we estimate the proper range of particle sizes needed for considerable increase in fracture toughness. We specify general results obtained for the case of yttria stabilized ZrO2 particles in Al2O3- and WC-based ceramics.
Prof. Irina Hussainova
A. B. Freidin et al., "Critical Radius in the Effect of Transformation Toughening of Zirconia Doped Ceramics and Cermets", Key Engineering Materials, Vol. 527, pp. 68-73, 2013