Atomic force microscopy of transformation toughening in ceria-stabilized zirconia

TL;DR

This paper uses atomic force microscopy to observe transformation toughening mechanisms in ceria-stabilized zirconia, revealing how alloying content influences transformation potential and fracture toughness.

Contribution

It demonstrates the application of AFM to directly observe martensite formation and analyzes the effects of alloying on transformation toughening in zirconia.

Findings

AFM visualizes martensite pairs near cracks.

Transformation potential decreases with more CeO2.

Transformation-induced plasticity contributes to toughening.

Abstract

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.