Abstract: The residual stress in the particulate reinforced zircon matrix composites was characterizedby X-ray diffraction method. The relationship between the residual stress and toughening behaviorwas discussed on the basis of mechanical properties determination and microstructural observation.The results indicated that a bigger mismatch in the coefficients of thermal expansion of reinforcingparticle and matrix leads to a better toughening effect when the thermal expansion coefficientof particle (α_p) is higher than that of matrix (α_m). It was suggested that the main toughening mechanisms were the crack deflection and branching, which were attributed to the existence of residual stress. The increments of fracture toughness of composites calculated by residual stress field theory were in good agreement with the experiment values.

Key words: residual stress, zircon, toughening, composite