Experimental and numerical investigations on the residual strains of YAG phase in directionally solidified eutectic Al₂O₃/YAG ceramic composite

Because of the attractiveness in superior oxidation resistance, high stability of the microstructure and excellent high temperature mechanical properties in oxidative environment, directionally solidified eutectic (DSE) oxide/oxide ceramic composite have been considered as one of the most potential structural materials for advanced energy generation systems and space propulsion systems. However, due to the mismatch in coefficient of thermal expansion (CTE), the residual strains are always generated from the fabrication process and thermal cycling in use, which would have an influence on properties of DSE ceramic composites. Therefore, the investigation of magnitude, state and distribution of residual strains in oxide ceramic composites is a crucial work. In this study, the residual strains of YAG phase in directionally solidified eutectic Al₂O₃/Y₃Al₅O₁₂ (YAG) ceramic composite were estimated by X-ray diffraction technique and finite element method (FEM). In the X-ray strain measurement, the YAG skeleton specimen derived from the composite by removing the Al₂O₃ phase was used as un-strained reference specimen. The X-ray strain measurements with CuKα irradiation were performed on the two faces: parallel and perpendicular to the solidification direction. The principal residual strains measured from the family of 888 diffraction in YAG phase indicated that YAG phase in composite is in compression. The measured residual strains are varied from -2.19±0.32 (×10^-4) to -4.22±0.08 (×10^-4) on faces parallel and perpendicular to the solidification direction respectively. The experimental results were accounted for by the FEM simulation.