Phase field study of crack growth in t′ yttria stabilized zirconia with initial domain structures

Abstract

In this paper, the fracture behavior of t′ yttria stabilized zirconia (YSZ) with initial domain structures is studied with the phase field (PF) method. Firstly, a PF model is proposed to characterize the initial domain structure and the subsequent domain switching in YSZ. After that, the PF model for domain structure evolution is coupled with the variational PF fracture model to simulate crack growth in the multi domain YSZ. The toughening effect induced by the ferroelastic domain switching is evaluated by computing the energy dissipation rate (EDR) along with the crack growth. It is shown that the internal stress field of the initial domain structure has very trivial influence on the crack growth resistance. However, the domain switching in the crack growth process can have significant influences on the fracture resistance. The domain structure evolution can bring about a local toughening or deshielding effect on the crack growth, depending on the crystal orientation. The underlying mechanisms are analyzed in detail. The proposed PF approach is efficient to study the mesoscale fracture behavior of multi domain YSZ and is helpful to assess the integrity of thermal barrier coatings.