A theoretical estimation has been made on the effect of debonding at the phase interface on Young's modulus in sintered PSZ/stainless steel composites with an abnormal deterioration of Young's modulus. The present analysis is based on Eshelby's equivalent inclusion method and a debonding model. A comparison is made between the theoretically predicted Young's modulus and experimental data for the composites having three different combinations of original powder size. The theoretical calculation shows that the Young's modulus decreases with increasing fraction of debonding. The fraction of debonding can be, in turn, predicted by comparing the theoretical calculation with the experimental data which have been found to depend on the composition of PSZ and original particle size. The particle size dependence on debonding has been discussed using the Weibull distribution, which shows that the coarser dispersoids have more debonded interface. The composition dependence has been explained by the variation of interface's residual stress with composition, which is generated by the mismatch of thermal expansion coefficients between the matrix and the dispersed particles, and the residual stress is compressive at the metal-rich side and tensile at the ceramic-rich side. The tensile stress at the interface enhances the debonding, however, the compressive stress defend it and improve the Young's modulus. The dependence of the abnormal deterioration of Young's modulus on the composition and particle size has been well accounted for.
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