Undercooling versus stress induced martensitic phase transformation: The case of MgO – partially stabilized zirconia

Abstract

The martensitic tetragonal-to-monoclinic (t→m) phase transformation is the primary inelastic deformation mechanism in zirconia ceramics. In this study, a Ginzburg-Landau type phase-field model is utilized to simulate phase transformations in MgO-partially stabilized zirconia, clearly distinguishing between the effects of undercooling and stress. The simulation results reproduce characteristic lamellar microstructures observed in experiments. Our study shows distinctive differences in microstructure and evolution path between undercooling-induced and stress-induced t→m transformations. In the latter case, sequential growth of monoclinic lamellae is observed, whereas undercooling induced microstructure evolution is characterized by an almost homogeneous and simultaneous nucleation of the monoclinic phase. We show that the different behavior can be explained by the presence of an energy barrier in the Gibbs free enthalpy. It is found that the presence of residual stresses in the tetragonal phase provides such a barrier and contributes to the stability of the tetragonal phase at low temperatures.