Martensitic transformation in zirconia. Part II: Martensite growth

TL;DR

This study investigates the growth mechanisms of martensitic transformation in zirconia, revealing three growth modes, the role of grain boundaries, and supporting the absence of a critical grain size for low-temperature transformation.

Contribution

It provides detailed analysis of martensite growth modes and surface relief features in zirconia, expanding understanding of transformation mechanisms at low temperatures.

Findings

Three growth modes identified and explained.

Microcracks linked to grain disorientation.

No critical grain size for low-temperature transformation.

Abstract

Though the martensitic transformation in zirconia has been the object of a very large number of studies for the last decades, qualitative and quantitative observations of the formation and growth of relief induced by low temperature treatments has hardly ever been reported. In the first part of the study, we have demonstrated the excellent agreement between the atomic force microscopy quantitative observations and the outputs of the calculations derived from the phenomenological theory of martensitic transformation. The intermediate stages of transformation were nonetheless not considered. In this second part, the growth mechanisms of monoclinic phase resulting from the martensitic transformation in ceria-stabilized zirconia (10 mol% CeO2) are investigated. Surface transformation is induced by ageing treatments in water vapor at 413 K. The observations are rationalized by the recent analysis proposed for the crystallographic ABC1 correspondence choice, where the ct axis transforms to the cm axis. Three growth modes are observed and interpreted in terms of transformation strains accommodation. Microcracks formation is observed, explaining grain pop-out where the crystallographic disorientation between two adjacent grains is the largest. The influence of grain boundary paths on the surface relief features is demonstrated. Overall, our results strongly support the non-existence of a critical grain size for low temperature transformation, confirmed by the classical thermodynamics theory applied to this particular case.