Melt Growth Composite material (MGC) consists of multiple single crystal with fine entangled in three dimensional network structures. The MGCs are thermally stable and have higher creep resistance. Furthermore, the flexural strength at room temperature can be maintained almost up to the melting point. In this study, in order to discuss the generation mechanism of residual stress in an Al2O3/Y3Al5O12 (YAG) binary MGC, the residual stresses of YAG phase were measured by X-rays from synchrotron radiation source. We used a method for stress determination of single crystal by using a position sensitive proportional counter (PSPC) system and a specimen-oscillating device. Lattice strains of {4 6 10} in the YAG phase were measured. The residual stresses were from 40 to 120MPa in tension in the longitudinal direction which corresponds to the solidification direction, 80MPa in compression in the thickness direction, and 70MPa in tension in the width direction. Since the thermal expansion behavior of Al2O3 is anisotropy in the crystallographic direction, the residual stress states of MGC indicated the anisotropy. However, only the mismatch of the thermal expansion coefficient between each phase cannot lead the reason of the generation mechanism of the residual stresses. The Young's modulus, which was mechanically measured using a four-point bending method, was about 349±3GPa, which is equal to the Young's modulus calculated by the Voigt model. The X-ray stresses on YAG phase under applied stressing were equivalent with the calculated stresses based on the Voigt model. Therefore, the Voigt model may be applied in the stress behavior on the Al2O3/YAG binary MGC.
