Assessment of effective elastic properties and residual stresses in directionally solidified eutectic Al2O3/YAG/ZrO2 ceramics by finite element analysis

S. Gourdin, L. Marcin, M. Podgorski, M. Cherif, L. Carroz - Safran Tech – Safran Group, Magny-les-Hameaux, France; SIMaP-EPM, UMR 5266 CNRS, Saint Martin d’Hères, France; RSA Le Rubis SA, Jarrie, France; Safran Aircraft Engines – Safran Group, Etablissement de Villaroche, Moissy-Cramayel, France

Current materials such nickel based superalloys cannot be used anymore and new materials are thus considered. For the hottest parts of jet engines, eutectic ceramics have potentially interesting features. In order to assess the thermo-mechanical properties of this material, numerical multi-scale analyses may be performed. Thus, a 3D finite element model was generated from a CT scan, representative of the microstructure and with a similar volume fraction. Effective elastic properties were calculated by numerical homogenisation. They highlight a quasi-isotropic behaviour of the ternary eutectic ceramics. Thermal residual stresses induced by the manufacturing were also evaluated. Tensile residual stresses in yttria-stabilised zirconia and compressive residual stresses in YAG and alumina were highlighted. This evaluation also shed light on the influence of the phase morphology in the microstructure. Indeed, the computed spatial distribution of the residual stresses showed that they are different from one position to another due to the variation in phase morphology, and also to material properties variability. Therefore, it is important when numerically assessing the thermomechanical properties to take into account the microstructure morphology as well as the variability of material properties.

How Amira-Avizo Software is used

In order to generate a 3D finite element model, a cube of 1 million voxels corresponding to a 30μm edge was removed from the initial CT-scan. Then, several steps were performed in Avizo 9.0 software to segment the three phases and generate a tetrahedral mesh of about 10 million finite elements (C3D4, 5 million degrees of freedom). The resulting 3D finite element model seems to be representative of the real microstructure regarding phases’ morphology and volume fraction.