Residual stresses in YAG phase of melt growth Al2O3/YAG eutectic composite estimated by indentation fracture test and finite element analysis

The residual stresses in YAG phase of the melt growth Al2O3/YAG eutectic composite were studied at room temperature by means of the indentation fracture test and finite element stress analysis. The YAG phase taken out from the composite was used as a reference sample without thermally induced residual stresses. The apparent fracture toughness of YAG phase with residual stress in the composite was higher than that of the reference sample of bare YAG. From the difference in fracture toughness value between the YAG in the composite and the bare YAG, the residual stress of YAG in the composite was estimated to be −170 ± 100 and −220 ± 130 MPa in the cross-sections perpendicular and parallel to the solidification direction, respectively. The experimentally measured spatial distribution of the residual stress in YAG phase in the composite was accounted for by the result of finite element analysis, which showed that the residual stress is different from position to position due to the variation in local morphology of YAG and Al2O3 within the composite.