  We demonstrate in this paper that atomic force microscopy can be successfully
used to gain further insights into the understanding of transformation
toughening in ceria stabilized zirconia. Transformation was induced by stresses
accumulated in the region surrounding propagating cracks in double torsion
samples. The resolution provided by AFM at the surface of the samples made it
possible to observe the formation of self accommodated martensite pairs in the
near crack areas. The potential for transformation is found to decrease with
increasing alloying addition, and is totally suppressed for 16 mol.% CeO2-TZP
samples. A statistical analysis of the martensite pair orientation is
performed, and the relationship with the applied stress and strain fields is
discussed. The contribution to transformation toughening by
transformation-induced plasticity occurring in the formation of martensitic
variant pairs with small net shear is demonstrated. The influence of alloying
addition content on the potential for transformation toughening and fracture
toughness values is finally discussed.
